Ozone production sensitivity is widely used to reveal the chemical dominant precursors of urban ozone rise.Here,we diagnose the impact of the decline in global human production activities level caused by the COVID-19 ...Ozone production sensitivity is widely used to reveal the chemical dominant precursors of urban ozone rise.Here,we diagnose the impact of the decline in global human production activities level caused by the COVID-19 on ozone sensitivity through the ratio of formaldehyde(HCHO)and NO_(2)(FNR=HCHO/NO_(2))observations from the TROPOspheric Monitoring Instrument.We use a relative uncertainty threshold to clean the satellite FNR,and our satellite FNR present a good correlation(R=0.6248)with U.S.Environmental Protection Agency observations.We found that the outbreak of the COVID-19 did not change the pattern of global ozone sensitivity,while the global regimes was transforming or strengthening to VOC-limited regimes due to the significant decline of human production activities levels.During the COVID-19,ozone sensitivity in Eastern China and East Africa continued to shift to VOC-limited regimes,while India,Western Europe and North America first moved to NOx-limited regimes,and then changed to VOC-limited regimes with the resumption of production and the increase in travel.The clustering results tell that urban ozone sensitivity tends to shift towards NOx-limited regimes as economic growing.The ozone formation in cities with lower FNR and per capita gross domestic product(GDP)are more sensitive to changes in VOCs,while cities with higher FNR and per capita GDP are more sensitive to variations in NOx.Cities with intermediate FNR and GDP are good evidence of the existence of transitional regimes.Our study identifies the driving role of urban economics in orienting the evolution of ozone sensitivity regimes.展开更多
This research study fabrics to ensure that they are free from carcinogenic dyes. It has been observed that there are poor-quality fabrics and consumers go to buy them without paying attention to the risks of using pro...This research study fabrics to ensure that they are free from carcinogenic dyes. It has been observed that there are poor-quality fabrics and consumers go to buy them without paying attention to the risks of using prohibited materials in the manufacture of these fabrics, and the use of unknown dyes has proven that some of them cause diseases to humans, especially children, that cause cancerous diseases. With the study sample consisting of (7), the study results indicate the presence of toxic formaldehyde in all sample dyes obtained from discount markets and online shopping.展开更多
The unique properties of TiO_(2)-sulfur(TiO_(2)-S)modified graphene nanocomposite electrode(GPE/TiO_(2)-S)in the electrochemical sensing of formaldehyde compound has been evaluated.We prepared TiO_(2)-S by hydrotherma...The unique properties of TiO_(2)-sulfur(TiO_(2)-S)modified graphene nanocomposite electrode(GPE/TiO_(2)-S)in the electrochemical sensing of formaldehyde compound has been evaluated.We prepared TiO_(2)-S by hydrothermal method and modified the graphene nanocomposite electrode by applying electrochemical cyclic voltammetry(CV)approach.The TiO_(2)-S nanocomposite was characterized by X-ray diffraction(XRD),while the GPE/TiO_(2)-S was examined by scanning electron microscopy(FESEM)and X-Ray fluorosense(XRF)techniques.TiO_(2)-S has a grain size of 19.32 nm.The surface morphology of the GPE/TiO_(2)-S nanocomposite shows a good,intact,and tightly porous structure with TiO_(2)-S covers the graphene surface.The content of optimized GPE/TiO_(2)-S electrodes is 41.5%of graphene,37.8%of TiO_(2),and 12.4%of sulfur that was prepared by mixing 1 g of TiO_(2)-S with 0.5 g of graphene and 0.3 mL paraffin.The GPE/TiO_(2)-S electrode produces a high anodic current(I_(pa))of 800μA and a high cathodic current(I_(pc))of-600μA at a scan rate of 0.1 V·s^(-1)using an electrolyte0.01 mol·L^(-1)K_3[Fe(CN)_6]solution containing 150 mg·L^(-1)formaldehyde.The limit of detection can reach as low as 9.7 mg·L^(-1)with stability with Horwitz ratio value as low as 0.397.The composite electrode also exhibits excellent slectivity properties by showing clear formaldehyde sugnal in the presence of high concentration of interfering agent.GPE/TiO_(2)-S electrode should find potential application of formaldehyde detection in food industries.展开更多
Volatile Organic Compounds(VOCs)are highly harmful to human beings and other organisms,and thus the elimination of VOCs is extremely urgent.Here,La-Si co-doped TiO_(2)microsphere photocatalysts,which were prepared by ...Volatile Organic Compounds(VOCs)are highly harmful to human beings and other organisms,and thus the elimination of VOCs is extremely urgent.Here,La-Si co-doped TiO_(2)microsphere photocatalysts,which were prepared by a hydrothermal method,exhibited high photocatalytic activity in the decomposition of formaldehyde compared with TiO_(2).The improved activity can be attributed to the promoted separation efficiency and density of the charge carriers,as verified by the electrochemical results in combination with density functional theory calculations.In addition,the Si dopant changed the microstructure and surface acidity,while the addition of La promoted the separation efficiency of charge carriers.More interestingly,it was found that singlet oxygen was the key species in the activation of molecular dioxygen,and it played a pivotal role in the photocatalytic decomposition of formaldehyde.This work provides a novel strategy for the selective activation of dioxygen for use in the decomposition of formaldehyde.展开更多
Highly dispersed noble metals are acknowledged for its pivotal role in influencing the efficiency of catalysts during the HCHO oxidation process.Interestingly,in this work,an innovative approach was employed to augmen...Highly dispersed noble metals are acknowledged for its pivotal role in influencing the efficiency of catalysts during the HCHO oxidation process.Interestingly,in this work,an innovative approach was employed to augmenting the stabilization of noble metals on irreducible carriers supported noble metal catalyst(Pd/SiO_(2))by adding alkali metal potassium(K).A formidable promotion effect was observed when the K doping to Pd/SiO_(2) catalysts.It achieves a conversion rate of 93%for 270 ppmV of HCHO to harmless CO_(2) and H_(2)O at a weight hourly space velocity(WHSV)of 300,000 mL/(g·hr)at 25℃.Multiple characterization results illustrated that a strong interaction between added K and Pd species was formed after K addition,which not only stabilized Pd species on the carrier surface but alsomarkedly enhanced its dispersal on the SiO_(2) carrier.The increasing Pd dispersion induced more oxygen vacancies on the surfaces of the Pd/SiO_(2) catalysts.The formation of these oxygen vacancies can be attributed to the phenomenon of hydrogen spillover,which also contributed to elevating the electron density on the Pd sites.Meanwhile,the oxygen vacancies favored the O_(2) activation to formmore reactive oxygen species participating in the HCHO oxidation reaction,thus improving the performance of Pd/SiO_(2) catalysts displayed for HCHO oxidation.This study provides a simple strategy to design high-performance irreducible carriers supported noble metal catalysts for HCHO catalytic oxidation.展开更多
Formaldehyde(HCHO)is a significant indoor pollutant found in various sources and poses potential health risks to humans.Noble metal catalysts show efficient and stable catalytic activity for ambient-temperature HCHO o...Formaldehyde(HCHO)is a significant indoor pollutant found in various sources and poses potential health risks to humans.Noble metal catalysts show efficient and stable catalytic activity for ambient-temperature HCHO oxidation,yet suffer from low metal utilization.Efforts focus on designing catalysts with enhanced intrinsic activity and reduced noble metal loading.In this study,we developed a simple pretreatment method using ammonia solution on SiO_(2)carrier to enhance the activity of the Pd/SiO_(2)catalyst for HCHO oxidation.After the carrier was pretreated with an ammonia solution,a significant promoting effect was observed on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst.It achieved almost complete oxidation of 150 ppmV of HCHO at 25℃,much better than the Pd/SiO_(2)-R(5%HCHO conversion rate).Multiple characterization results indicated that the ammonia solution pretreatment of the SiO_(2)carrier increased the surface defects,facilitating the anchoring of Pd nanoparticles and increasing their dispersion.The increase dispersion of Pd resulted in the generation of additional oxygen vacancies on the catalyst surfaces.The increased in oxygen vacancies on the catalyst was beneficial for enhancing the catalyst's ability to activate H_(2)O to form surface hydroxyl groups,thereby accelerating the catalytic oxidation process of HCHO.The reaction mechanism of HCHO on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst mainly follows an efficient pathway:firstly,the HCHO being oxidized by surface active hydroxyl groups to formate;subsequently,the formate being oxidized by hydroxyl groups to H_(2)O and CO_(2).This study provides a promising strategy for designing high-performance noble metal catalysts for HCHO catalytic oxidation.展开更多
Iron-Vanadium(FeV)catalyst showed a unique catalytic activity for the selective oxidation of methanol to formaldehyde;however,due to its complex compositions,the identification of catalytic active sites still remains ...Iron-Vanadium(FeV)catalyst showed a unique catalytic activity for the selective oxidation of methanol to formaldehyde;however,due to its complex compositions,the identification of catalytic active sites still remains challenging,inhibiting the rational design of excellent FeV-based catalysts.Here,in this work,a series of FeV catalysts with various compositions,including FeVO_(4),isolated VO_(x),low-polymerized V_(n)O_(x),and crystalline V_(2)O_(5) were prepared by controlling the preparation conditions,and were applied to methanol oxidation to formaldehyde reaction.A FeV_(1.1) catalyst,which consisted of FeVO_(4) and low-polymerized V_(n)O_(x) species showed an excellent catalytic performance with a methanol conversion of 92.3%and a formaldehyde selectivity of 90.6%,which was comparable to that of conventional iron-molybdate catalyst.The results of CH_(3)OH-IR,O_(2) pulse and control experiments revealed a crucial synergistic effect between FeVO_(4) and low-polymerized V_(n)O_(x).It enhanced the oxygen supply capacity and suitable binding and adsorption strengths for formaldehyde intermediates,contributing to the high catalytic activity and formaldehyde selectivity.This study not only advances the understanding of FeV structure but also offers valuable guidelines for selective methanol oxidation to formaldehyde.展开更多
During high-temperature periods in summer,formaldehyde(HCHO)levels increase due to secondary production.However,recent studies have also shown a rise in the HCHO concentration in winter,but the underlying cause remain...During high-temperature periods in summer,formaldehyde(HCHO)levels increase due to secondary production.However,recent studies have also shown a rise in the HCHO concentration in winter,but the underlying cause remains unclear.Here,HCHO observations in urban Beijing were conducted,the impact of meteorological differences between warm and cold seasons to HCHO concentrations was investigated.Additionally,the positive matrix factorization model was applied to the source apportionment of HCHO,with a focus on changes during pollution events.The results indicated that,during warm seasons,the secondary production of HCHO was driven by high temperature influenced by the low-pressure front,with the contribution of secondary production+background peaking at 85.9% in the afternoon,exhibiting a unimodal diurnal variation.Conversely,during cold seasons,the influence of a uniform pressure field,coupled with weak winds,low boundary layers and high humidity,led to HCHO accumulation from primary emissions,resulting in multiday highconcentration pollution.During the most severe pollution periods,anthropogenic primary emissions contributed up to 91.7%.Therefore,while the contribution of volatile organic compounds to HCHO levels through secondary production has been recognized,the significant impact of primary emissions during cold seasons cannot be overlooked.展开更多
The efficient catalytic conversion of fossil-based low-carbon small molecules to oxygen-containing chemicals is an attractive research topic in the fields of energy and chemical engineering.The selective oxidation of ...The efficient catalytic conversion of fossil-based low-carbon small molecules to oxygen-containing chemicals is an attractive research topic in the fields of energy and chemical engineering.The selective oxidation of dimethyl ether(DME),which is derived from fossil resources,represents a promising approach to producing high-concentration formaldehyde with low energy consumption.However,there is still a lack of catalysts achieving satisfactory conversion of DME with high selectivity for formaldehyde under mild conditions.In this work,an efficient iron-molybdate(FeMo)catalyst was developed for the selective oxidation of DME to formaldehyde.The DME conversion of 84% was achieved with a superior formaldehyde selectivity(77%)at 300℃,a performance that is superior to all previously reported results.In an approximately 550 h continuous reaction,the catalyst maintained a conversion of 64% and a formaldehyde selectivity of 79%.Combined X-ray diffraction(XRD),Transmission electron microscope(TEM),Ultraviolet-visible spectroscopy(UV-Vis),Hydrogen temperature-programmed reduction(H_(2)-TPR),Fourier transform infrared(FT-IR)analyses,along with density functional theory(DFT)calculations,demonstrated that the excellent FeMo catalyst was composed of active Fe_(2)(MoO_(4))_(3)and MoO_(3)phases,and there was an interaction between them,which contributed to the efficient DME dissociation and smooth hydrogen spillover,leading to a superior DME conversion.With the support of DME/O_(2)pulse experiments,in-situ Raman,in-situ Dimethyl ether infrared spectroscopy(DME-IR)and DFT calculation results,a Mars-van Krevelen(MvK)reaction mechanism was proposed:DME was dissociated on the interface between Fe_(2)(MoO_(4))_(3)and MoO_(3)phases to form active methoxy species firstly,and it dehydrogenated to give hydrogen species;the generated hydrogen species smoothly spilled over from Fe_(2)(MoO_(4))_(3)to MoO_(3)enhanced by the interaction between Fe_(2)(MoO_(4))_(3)and MoO_(3);then the hydrogen species was consumed by MoO_(3),leading to a reduction of MoO_(3),and finally,the reduced MoO_(3)was re-oxidized by O_(2),returning to the initial state.These findings offer valuable insights not only for the development of efficient FeMo catalysts but also for elucidating the reaction mechanism involved in the oxidation of DME to formaldehyde,contributing to the optimized utilization of DME derived from fossil resources.展开更多
Herein we report the facial detection of formaldehyde(FA)by using an interesting red acidichromic carbon dots(ACDs)which turns blue when pH gradually decreases.The color change was attributed to the conversion between...Herein we report the facial detection of formaldehyde(FA)by using an interesting red acidichromic carbon dots(ACDs)which turns blue when pH gradually decreases.The color change was attributed to the conversion between the double bonds(C=N)and single bonds(C-N)on the surface of the ACDs.Inspired by the reaction between FA and ammonium chloride that produces H^(+)and methenamine and decrease the pH value of the solution,a fast and simple visual detection method for FA was found with a minimum discriminated concentration of 0.04 mol/L.A fluorescence detection method for FA was also found with LOD of 0.029 mol/L and FA in real sample,e.g.,shredded squid was successfully analyzed.This work provides a new idea of developing fast visual detection method for daily monitor or in-site semiquantitative assessment on FA.展开更多
A chain of GdCe oxides boosted biochars derived from maize straw and sewage sludge(GdyCe1-y/MPBs)were fabricated for formaldehyde(HCHO)catalytic decomposition.The ingenerate relationship between the abatement performa...A chain of GdCe oxides boosted biochars derived from maize straw and sewage sludge(GdyCe1-y/MPBs)were fabricated for formaldehyde(HCHO)catalytic decomposition.The ingenerate relationship between the abatement performance and corresponding structural feature was comprehensively evaluated by XPS,in situ DRIFTS,BET,XRD,SEM and H_(2)-TPR.Meanwhile,10%Gd0.25Ce0.75/MPB exhibited excellent performance,favorable SO_(2) and moisture toleration over a broad temperature range from 160 to 320℃,where it achieved 96.8%removal efficiency with 90.5%selectivity at 200℃.The single or united effects of O_(2),SO_(2),H_(2)O on HCHO abatement over 10%Gd_(0.25)Ce_(0.75)/MPB were tested,and the findings demonstrated that the suppressive effects of SO_(2) and H_(2)O outweighed the promoting influence of O_(2) within a specific range.Gd and Ce co-modified MPB revealed superior HCHO removal capability in contrast to that of Gd or Ce severally modified MPB,ascribing to the synergistic effect of GdO_(x) and CeO_(x) and benefitting from the augmentation of surface area and total pore volume,the aggrandizement of surface active oxygen species,the promotion of redox ability and the inhibition crystallization of CeO_(x).According to in situ DRIFTS,a series of intermediates including formate species and dioxymethylene(DOM)were produced,which would eventually decompose into H_(2)O and CO_(2).In addition,the mass transfer and diffusion of the reactants along with the accessibility of the catalytic sites were enlarged by the hierarchical porous structure of the support,which were also answerable for its distinguished catalytic performance.Furthermore,10%Gd0.25Ce0.75/MPB possessed remarkable potential for industrial applications.展开更多
Vanadium phosphorus oxide(VPO)catalyst is a promising candidate for the condensation reaction of formaldehyde(FA)and acetic acid(HAc)to produce acrylic acid(AA).However,the complexity of the active phases and their dy...Vanadium phosphorus oxide(VPO)catalyst is a promising candidate for the condensation reaction of formaldehyde(FA)and acetic acid(HAc)to produce acrylic acid(AA).However,the complexity of the active phases and their dynamic interconversion under redox conditions has led to controversies regarding the actual active phase in this reaction.To address this,this study systematically investigates the phase transition and underlying mechanism of VPO catalysts under reaction conditions.X-ray diffraction(XRD)patterns,Raman spectra,transmission electron microscopy images and X-ray photoelectron spectroscopy collectively demonstrated that the V^(4+)phase(VO)_(2)P_(2)O_(7)retained the bulk phase structure throughout the reaction,with only minor surface phase transition observed.In contrast,the V^(5+)phase underwent reduction to other phases in both bulk and surface regions.Specifically,theδ-VOPO_(4)phase rapidly transformed into theαII-VOPO_(4)phase,which could reversibly convert into the R1-VOHPO_(4)phase(V^(4+)).Controlled variable experiments,H_(2)-temperature programmed reduction and in-situ XRD experiments in a hydrogen atmosphere further demonstrated that these phase transitions were primarily attributed to the loss of lattice oxygen.The presence of V^(4+)phase in VPO catalysts enhanced the selectivity of acrylic acid,while the existence of V^(5+)phase promoted the activation of acetic acid.This work elucidates the redox-driven phase evolution of VPO catalysts and offers valuable insights for designing efficient catalysts for FA-HAc cross-condensation by balancing phase stability and activity.展开更多
The SiO_(2) inverse opal photonic crystals(PC)with a three-dimensional macroporous structure were fabricated by the sacrificial template method,followed by infiltration of a pyrene derivative,1-(pyren-8-yl)but-3-en-1-...The SiO_(2) inverse opal photonic crystals(PC)with a three-dimensional macroporous structure were fabricated by the sacrificial template method,followed by infiltration of a pyrene derivative,1-(pyren-8-yl)but-3-en-1-amine(PEA),to achieve a formaldehyde(FA)-sensitive and fluorescence-enhanced sensing film.Utilizing the specific Aza-Cope rearrangement reaction of allylamine of PEA and FA to generate a strong fluorescent product emitted at approximately 480 nm,we chose a PC whose blue band edge of stopband overlapped with the fluorescence emission wavelength.In virtue of the fluorescence enhancement property derived from slow photon effect of PC,FA was detected highly selectively and sensitively.The limit of detection(LoD)was calculated to be 1.38 nmol/L.Furthermore,the fast detection of FA(within 1 min)is realized due to the interconnected three-dimensional macroporous structure of the inverse opal PC and its high specific surface area.The prepared sensing film can be used for the detection of FA in air,aquatic products and living cells.The very close FA content in indoor air to the result from FA detector,the recovery rate of 101.5%for detecting FA in aquatic products and fast fluorescence imaging in 2 min for living cells demonstrate the reliability and accuracy of our method in practical applications.展开更多
The formaldehyde oxidation reaction(FOR)on a Cu-based electrocatalyst enables hydrogen(H_(2))at the anode in OH−solution,facilitating a bipolar H_(2) production system at ultra-low electrolysis voltage.However,the spe...The formaldehyde oxidation reaction(FOR)on a Cu-based electrocatalyst enables hydrogen(H_(2))at the anode in OH−solution,facilitating a bipolar H_(2) production system at ultra-low electrolysis voltage.However,the specific impact of*OH adsorption on the Cu surface regarding the FOR has been rarely investigated.Herein,the strong*OH adsorption Cu(S-OH Cu)electrode,which exhibits high activity and excellent stability of FOR,is developed to investigate the specific impact of*OH adsorption on the Cu surface during the FOR process.Impressively,the increased*OH adsorption on the Cu electrode,typically regarded as a poisoning effect that diminishes inherent FOR activity by reducing the adsorption of intermediate reactants,is firstly revealed as an OH-induced favorable reconstruction effect that significantly improves FOR stability.Specifically,the dual functions of OH-induced favoring reconstruction include accelerating the phase transition of the Cu(0)/Cu(I)redox cycle to refresh the active site and optimizing surface reconstruction to preferentially generate Cu(220)with stronger adsorption energy for H_(2)C(OH)O*and lower C−H barrier energy during FOR.This work provides a promising strategy for designing stable Cu electrocatalysts for FOR to produce hydrogen with extremely low energy input.展开更多
Multi-axial differential optical absorption spectroscopy(MAX-DOAS)measurements were conducted in Xishuangbanna,Yunnan,China,between November 1,2021 and June 30,2022 to obtain vertical distributions of formaldehyde(HCH...Multi-axial differential optical absorption spectroscopy(MAX-DOAS)measurements were conducted in Xishuangbanna,Yunnan,China,between November 1,2021 and June 30,2022 to obtain vertical distributions of formaldehyde(HCHO)and glyoxal(CHOCHO).The observations show an increase in vertical column densities(VCDs)and volume mixing ratios(VMRs)for both HCHO and CHOCHO concentrations during periods of biomass combustion.The VCDs of HCHO and CHOCHO from TROPOMI are in good agreementwith the MAX-DOAS observations.(R^(2) HCHO=0.71;R^(2) CHOCHO=0.70).Regarding seasonal variations,HCHO predominantly occupies the upper layer(400-800 m)during the biomass burning,possibly attributed to the formation of secondary HCHO as the plume ascends during combustion.CHOCHO is primarily found in the lower layer(0-200 m),suggesting a longer lifespan for HCHO compared to CHOCHO,preventing the latter from diffusing to higher altitudes.Concerning the daily variation patterns,both HCHO and CHOCHO VMRs exhibited peaks at 9:00 and 13:00,which were attributed to the nighttime accumulation and midday oxidation.Furthermore,we also investigated the sources of volatile organic compounds(VOCs)using the CHOCHO to HCHO ratio(RGF).During the period of biomass burning,there are minimal differences in the daily RGF across layers,indicating that biomass burning is the predominant source.During the non-biomass burning period,the daily RGF shows significant differences among layers,indicating that emissions from biological and anthropogenic sources primarily contribute during the period.展开更多
Nowadays,it is still a challenge to prepared high efficiency and low cost formaldehyde(HCHO)removal catalysts in order to tackle the long-living indoor air pollution.Herein,δ-MnO_(2)is successfully synthesized by a f...Nowadays,it is still a challenge to prepared high efficiency and low cost formaldehyde(HCHO)removal catalysts in order to tackle the long-living indoor air pollution.Herein,δ-MnO_(2)is successfully synthesized by a facile ozonation strategy,where Mn^(2+)is oxidized by ozone(O_(3))bubble in an alkaline solution.It presents one of the best catalytic properties with a low 100%conversion temperature of 85℃for 50 ppm of HCHO under a GHSV of 48,000 mL/(g·hr).As a comparison,more than 6 times far longer oxidation time is needed if O3 is replaced by O_(2).Characterizations show that ozonation process generates a different intermediate of tetragonalβ-HMnO_(2),which would favor the quick transformation into the final productδ-MnO_(2),as compared with the relatively more thermodynamically stable monoclinicγ-HMnO_(2)in the O_(2)process.Finally,HCHO is found to be decomposed into CO_(2)via formate,dioxymethylene and carbonate species as identified by room temperature insitu diffuse reflectance infrared fourier transform spectroscopy.All these results show great potency of this facile ozonation routine for the highly activeδ-MnO_(2)synthesis in order to remove the HCHO contamination.展开更多
CO2 hydrogenation to formate is an effective strategy for promoting the sustainable carbon cycle.However,formate yields are significantly influenced by the amount of noble metal(e.g.,Pd)used.Here,we present Pd-Ni syne...CO2 hydrogenation to formate is an effective strategy for promoting the sustainable carbon cycle.However,formate yields are significantly influenced by the amount of noble metal(e.g.,Pd)used.Here,we present Pd-Ni synergistic catalysis on the hollow NiCo2O4 spinel arrays(PdxNiy/NCO@CC)for enhanced formate production under mild conditions.The Pd-Ni dual-site structure effectively enhances electron accumulation on Pd via charge polarization and the synergistic interaction between Pd and Ni,leading to significantly improved formate yields with a reduced usage of noble metal catalyst.The optimized Pd5Ni5/NCO@CC catalyst achieved a remarkable formate yield of 282.5 molformate molPd^(-1)h^(-1)at 333 K and demonstrated high stability.This strategy of synergistically enhancing catalytic activity via bimetallic sites highlights its advantages in other catalytic fields and practical applications.展开更多
Formaldehyde is a common atmospheric pollutant produced in industrial production and daily life.However,the traditional semiconductor formaldehyde gas sensor cannot work at room temperature,which limits its practical ...Formaldehyde is a common atmospheric pollutant produced in industrial production and daily life.However,the traditional semiconductor formaldehyde gas sensor cannot work at room temperature,which limits its practical application.Therefore,developing high-performance gas sensors for rapidly and accurately detecting formaldehyde at room temperature is an important topic.In this study,Ti_(3)C_(2)Tx/SnO_(2)heterostructures were constructed,which could selectively detect formaldehyde at room temperature with a response value of 29.16%(10×10^(-6)).In addition,the sensor shows a remarkable theoretical detection limit of 5.09×10^(-9)and good longterm stability.Density functional theory(DFT)simulations reveal that SnO_(2)nano spheres provide the majority of adsorption sites that strongly interact with formaldehyde.Meanwhile,Ti_(3)C_(2)T_(x)acting as a conductive layer facilitates the transfer of charge carriers so that they show a sensing response to formaldehyde at room temperature.Moreover,the formation of p-n heterostructures between SnO_(2)and Ti_(3)C_(2)T_(x)boosts the Schottky barrier at the interface,which is the critical factor in enhancing the sensing properties by turning the Schottky barrier upon introducing formaldehyde gas.This perspective is expected to provide instructive guidance for utilizing MXene/metal oxide nanocomposites to improve the gas sensing performance at room temperature.展开更多
Changes in CO2 and temperature are correlated, but it is difficult to observe which is the cause and which is the effect. The release of CO2 dissolved in the ocean into the atmosphere depends on the atmospheric temper...Changes in CO2 and temperature are correlated, but it is difficult to observe which is the cause and which is the effect. The release of CO2 dissolved in the ocean into the atmosphere depends on the atmospheric temperature. However, examining the relationship between changes in CO2 caused by other phenomena and temperature is difficult. Studies of soil respiration (Rs) since the late 20th century have shown that CO2 emissions from soil respiration (Rs) are overwhelmingly greater than CO2 emissions from fossil fuel combustion. This is also noted in the IPCC carbon budget assessment. In this paper, the dependences of Rs on temperature, time, latitude, precipitation, seasons, etc., were investigated using the latest NASA database. The changes in temperature and Rs correlated well. There is also a good correlation between Rs and CO2 generation. Therefore, an increase in temperature results in an increase in CO2. On the other hand, there is no evidence other than model calculations that an increase in anthropogenic CO2 is mainly linked to a rise in temperature. The idea that global warming is caused by anthropogenic CO2 production is still a hypothesis. For these reasons, the relationship between global warming and anthropogenic CO2 should be reconsidered based on physical evidence without preconceptions. .展开更多
In the preparation of a series of Ce_(0.8)Zr_(0.2)O_(y)catalysts catalyzing the removal of formaldehyde,BET,H2-TPR,IR,SEM,XPS,and XRD were used to characterize the catalyst,and the influence of humidity on the catalys...In the preparation of a series of Ce_(0.8)Zr_(0.2)O_(y)catalysts catalyzing the removal of formaldehyde,BET,H2-TPR,IR,SEM,XPS,and XRD were used to characterize the catalyst,and the influence of humidity on the catalyst activity was studied by adjusting the humidity during the process.The experimental results showed that the formaldehyde removal rate increased with the increase of humidity.When the humidity was higher than 50%,the formaldehyde removal rate decreased by 3%over that when the humidity was 50%.The characterization results showed that humidity facilitated the activation of oxygen and the formation of hydroxyl groups,which both promoted the formation and oxidative decomposition of intermediates and prevented the deposition of intermediates that clogged the pores,allowing more formaldehyde to be adsorbed and oxidized,which increased the activity of the catalyst.This provides new mechanistic evidence for the oxidation of formaldehyde and helps in the development of relatively low-cost materials for formaldehyde purification.展开更多
基金supported by the National Key R&D Program(No.2021YFE0117300)the National Natural Science Foundation of China(No.42375090)+6 种基金Shenzhen Key Laboratory of Precision Measurement and Early Warning Technology for Urban Environmental Health Risks(No.ZDSYS20220606100604008)Guangdong Basic and Applied Basic Research Foundation(No.2021A1515110713)Guangdong University Research Project Science Team(No.2021KCXTD004)the Major Talent Project of Guangdong Province(No.2021QN020924)Shandong Provincial Natural Science Foundation,China(No.ZR2020QD012)Shenzhen Science and Technology Program(Nos.KQTD20210811090048025,JCYJ20210324104604012 and JCYJ20220530115404009)supported by the Center for Computational Science and Engineering at Southern University of Science and Technology.
文摘Ozone production sensitivity is widely used to reveal the chemical dominant precursors of urban ozone rise.Here,we diagnose the impact of the decline in global human production activities level caused by the COVID-19 on ozone sensitivity through the ratio of formaldehyde(HCHO)and NO_(2)(FNR=HCHO/NO_(2))observations from the TROPOspheric Monitoring Instrument.We use a relative uncertainty threshold to clean the satellite FNR,and our satellite FNR present a good correlation(R=0.6248)with U.S.Environmental Protection Agency observations.We found that the outbreak of the COVID-19 did not change the pattern of global ozone sensitivity,while the global regimes was transforming or strengthening to VOC-limited regimes due to the significant decline of human production activities levels.During the COVID-19,ozone sensitivity in Eastern China and East Africa continued to shift to VOC-limited regimes,while India,Western Europe and North America first moved to NOx-limited regimes,and then changed to VOC-limited regimes with the resumption of production and the increase in travel.The clustering results tell that urban ozone sensitivity tends to shift towards NOx-limited regimes as economic growing.The ozone formation in cities with lower FNR and per capita gross domestic product(GDP)are more sensitive to changes in VOCs,while cities with higher FNR and per capita GDP are more sensitive to variations in NOx.Cities with intermediate FNR and GDP are good evidence of the existence of transitional regimes.Our study identifies the driving role of urban economics in orienting the evolution of ozone sensitivity regimes.
文摘This research study fabrics to ensure that they are free from carcinogenic dyes. It has been observed that there are poor-quality fabrics and consumers go to buy them without paying attention to the risks of using prohibited materials in the manufacture of these fabrics, and the use of unknown dyes has proven that some of them cause diseases to humans, especially children, that cause cancerous diseases. With the study sample consisting of (7), the study results indicate the presence of toxic formaldehyde in all sample dyes obtained from discount markets and online shopping.
基金the financial support from the Ministry of Education,Culture,Research and Technology of the Republic of Indonesia under the Applied Research award(DIPA023.17.1.690523/2023)the World Class Professor award grant 2023。
文摘The unique properties of TiO_(2)-sulfur(TiO_(2)-S)modified graphene nanocomposite electrode(GPE/TiO_(2)-S)in the electrochemical sensing of formaldehyde compound has been evaluated.We prepared TiO_(2)-S by hydrothermal method and modified the graphene nanocomposite electrode by applying electrochemical cyclic voltammetry(CV)approach.The TiO_(2)-S nanocomposite was characterized by X-ray diffraction(XRD),while the GPE/TiO_(2)-S was examined by scanning electron microscopy(FESEM)and X-Ray fluorosense(XRF)techniques.TiO_(2)-S has a grain size of 19.32 nm.The surface morphology of the GPE/TiO_(2)-S nanocomposite shows a good,intact,and tightly porous structure with TiO_(2)-S covers the graphene surface.The content of optimized GPE/TiO_(2)-S electrodes is 41.5%of graphene,37.8%of TiO_(2),and 12.4%of sulfur that was prepared by mixing 1 g of TiO_(2)-S with 0.5 g of graphene and 0.3 mL paraffin.The GPE/TiO_(2)-S electrode produces a high anodic current(I_(pa))of 800μA and a high cathodic current(I_(pc))of-600μA at a scan rate of 0.1 V·s^(-1)using an electrolyte0.01 mol·L^(-1)K_3[Fe(CN)_6]solution containing 150 mg·L^(-1)formaldehyde.The limit of detection can reach as low as 9.7 mg·L^(-1)with stability with Horwitz ratio value as low as 0.397.The composite electrode also exhibits excellent slectivity properties by showing clear formaldehyde sugnal in the presence of high concentration of interfering agent.GPE/TiO_(2)-S electrode should find potential application of formaldehyde detection in food industries.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.22076063,22076098,and 21477047)the Natural Science Foundation of Shandong Province(No.ZR2020MB033)+1 种基金the Key Laboratory of Photochemical Conversion and Optoelectronic Materials,TIPC,CAS(No.PCOM202106)the program for Taishan Scholars of Shandong Province,and the Science and Technology Programof the University of Jinan(No.XKY2111).
文摘Volatile Organic Compounds(VOCs)are highly harmful to human beings and other organisms,and thus the elimination of VOCs is extremely urgent.Here,La-Si co-doped TiO_(2)microsphere photocatalysts,which were prepared by a hydrothermal method,exhibited high photocatalytic activity in the decomposition of formaldehyde compared with TiO_(2).The improved activity can be attributed to the promoted separation efficiency and density of the charge carriers,as verified by the electrochemical results in combination with density functional theory calculations.In addition,the Si dopant changed the microstructure and surface acidity,while the addition of La promoted the separation efficiency of charge carriers.More interestingly,it was found that singlet oxygen was the key species in the activation of molecular dioxygen,and it played a pivotal role in the photocatalytic decomposition of formaldehyde.This work provides a novel strategy for the selective activation of dioxygen for use in the decomposition of formaldehyde.
基金supported by the Youth Innovation Promotion Association,CAS(No.2020310)Sanming University(No.23YG05).
文摘Highly dispersed noble metals are acknowledged for its pivotal role in influencing the efficiency of catalysts during the HCHO oxidation process.Interestingly,in this work,an innovative approach was employed to augmenting the stabilization of noble metals on irreducible carriers supported noble metal catalyst(Pd/SiO_(2))by adding alkali metal potassium(K).A formidable promotion effect was observed when the K doping to Pd/SiO_(2) catalysts.It achieves a conversion rate of 93%for 270 ppmV of HCHO to harmless CO_(2) and H_(2)O at a weight hourly space velocity(WHSV)of 300,000 mL/(g·hr)at 25℃.Multiple characterization results illustrated that a strong interaction between added K and Pd species was formed after K addition,which not only stabilized Pd species on the carrier surface but alsomarkedly enhanced its dispersal on the SiO_(2) carrier.The increasing Pd dispersion induced more oxygen vacancies on the surfaces of the Pd/SiO_(2) catalysts.The formation of these oxygen vacancies can be attributed to the phenomenon of hydrogen spillover,which also contributed to elevating the electron density on the Pd sites.Meanwhile,the oxygen vacancies favored the O_(2) activation to formmore reactive oxygen species participating in the HCHO oxidation reaction,thus improving the performance of Pd/SiO_(2) catalysts displayed for HCHO oxidation.This study provides a simple strategy to design high-performance irreducible carriers supported noble metal catalysts for HCHO catalytic oxidation.
基金supported by the Sanming University(No.23YG05)the Science Foundation of Fujian Province(No.2023J011027).
文摘Formaldehyde(HCHO)is a significant indoor pollutant found in various sources and poses potential health risks to humans.Noble metal catalysts show efficient and stable catalytic activity for ambient-temperature HCHO oxidation,yet suffer from low metal utilization.Efforts focus on designing catalysts with enhanced intrinsic activity and reduced noble metal loading.In this study,we developed a simple pretreatment method using ammonia solution on SiO_(2)carrier to enhance the activity of the Pd/SiO_(2)catalyst for HCHO oxidation.After the carrier was pretreated with an ammonia solution,a significant promoting effect was observed on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst.It achieved almost complete oxidation of 150 ppmV of HCHO at 25℃,much better than the Pd/SiO_(2)-R(5%HCHO conversion rate).Multiple characterization results indicated that the ammonia solution pretreatment of the SiO_(2)carrier increased the surface defects,facilitating the anchoring of Pd nanoparticles and increasing their dispersion.The increase dispersion of Pd resulted in the generation of additional oxygen vacancies on the catalyst surfaces.The increased in oxygen vacancies on the catalyst was beneficial for enhancing the catalyst's ability to activate H_(2)O to form surface hydroxyl groups,thereby accelerating the catalytic oxidation process of HCHO.The reaction mechanism of HCHO on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst mainly follows an efficient pathway:firstly,the HCHO being oxidized by surface active hydroxyl groups to formate;subsequently,the formate being oxidized by hydroxyl groups to H_(2)O and CO_(2).This study provides a promising strategy for designing high-performance noble metal catalysts for HCHO catalytic oxidation.
文摘Iron-Vanadium(FeV)catalyst showed a unique catalytic activity for the selective oxidation of methanol to formaldehyde;however,due to its complex compositions,the identification of catalytic active sites still remains challenging,inhibiting the rational design of excellent FeV-based catalysts.Here,in this work,a series of FeV catalysts with various compositions,including FeVO_(4),isolated VO_(x),low-polymerized V_(n)O_(x),and crystalline V_(2)O_(5) were prepared by controlling the preparation conditions,and were applied to methanol oxidation to formaldehyde reaction.A FeV_(1.1) catalyst,which consisted of FeVO_(4) and low-polymerized V_(n)O_(x) species showed an excellent catalytic performance with a methanol conversion of 92.3%and a formaldehyde selectivity of 90.6%,which was comparable to that of conventional iron-molybdate catalyst.The results of CH_(3)OH-IR,O_(2) pulse and control experiments revealed a crucial synergistic effect between FeVO_(4) and low-polymerized V_(n)O_(x).It enhanced the oxygen supply capacity and suitable binding and adsorption strengths for formaldehyde intermediates,contributing to the high catalytic activity and formaldehyde selectivity.This study not only advances the understanding of FeV structure but also offers valuable guidelines for selective methanol oxidation to formaldehyde.
基金supported by the National Natural Science Foundation of China(Nos.42075097 and 42177081)the National Key R&D Program of China(No.2023YFC3706103)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0760200)Beijing Municipal Natural Science Foundation(No.8222075)the Youth Cross Team Scientific Research Project of the Chinese Academy of Sciences(No.JCTD-2021-10)。
文摘During high-temperature periods in summer,formaldehyde(HCHO)levels increase due to secondary production.However,recent studies have also shown a rise in the HCHO concentration in winter,but the underlying cause remains unclear.Here,HCHO observations in urban Beijing were conducted,the impact of meteorological differences between warm and cold seasons to HCHO concentrations was investigated.Additionally,the positive matrix factorization model was applied to the source apportionment of HCHO,with a focus on changes during pollution events.The results indicated that,during warm seasons,the secondary production of HCHO was driven by high temperature influenced by the low-pressure front,with the contribution of secondary production+background peaking at 85.9% in the afternoon,exhibiting a unimodal diurnal variation.Conversely,during cold seasons,the influence of a uniform pressure field,coupled with weak winds,low boundary layers and high humidity,led to HCHO accumulation from primary emissions,resulting in multiday highconcentration pollution.During the most severe pollution periods,anthropogenic primary emissions contributed up to 91.7%.Therefore,while the contribution of volatile organic compounds to HCHO levels through secondary production has been recognized,the significant impact of primary emissions during cold seasons cannot be overlooked.
基金supported by the National Natural Science Foundation of China(U23A2088,22025206)the Dalian Innovation Support Plan for High Level Talents(2022RG13)+2 种基金DICP(Grant:DICP I202453,DICP I202234)the Fundamental Research Funds for the Central Universities(20720220008)support of the Liaoning Key Laboratory of Biomass Conversion for Energy and Material。
文摘The efficient catalytic conversion of fossil-based low-carbon small molecules to oxygen-containing chemicals is an attractive research topic in the fields of energy and chemical engineering.The selective oxidation of dimethyl ether(DME),which is derived from fossil resources,represents a promising approach to producing high-concentration formaldehyde with low energy consumption.However,there is still a lack of catalysts achieving satisfactory conversion of DME with high selectivity for formaldehyde under mild conditions.In this work,an efficient iron-molybdate(FeMo)catalyst was developed for the selective oxidation of DME to formaldehyde.The DME conversion of 84% was achieved with a superior formaldehyde selectivity(77%)at 300℃,a performance that is superior to all previously reported results.In an approximately 550 h continuous reaction,the catalyst maintained a conversion of 64% and a formaldehyde selectivity of 79%.Combined X-ray diffraction(XRD),Transmission electron microscope(TEM),Ultraviolet-visible spectroscopy(UV-Vis),Hydrogen temperature-programmed reduction(H_(2)-TPR),Fourier transform infrared(FT-IR)analyses,along with density functional theory(DFT)calculations,demonstrated that the excellent FeMo catalyst was composed of active Fe_(2)(MoO_(4))_(3)and MoO_(3)phases,and there was an interaction between them,which contributed to the efficient DME dissociation and smooth hydrogen spillover,leading to a superior DME conversion.With the support of DME/O_(2)pulse experiments,in-situ Raman,in-situ Dimethyl ether infrared spectroscopy(DME-IR)and DFT calculation results,a Mars-van Krevelen(MvK)reaction mechanism was proposed:DME was dissociated on the interface between Fe_(2)(MoO_(4))_(3)and MoO_(3)phases to form active methoxy species firstly,and it dehydrogenated to give hydrogen species;the generated hydrogen species smoothly spilled over from Fe_(2)(MoO_(4))_(3)to MoO_(3)enhanced by the interaction between Fe_(2)(MoO_(4))_(3)and MoO_(3);then the hydrogen species was consumed by MoO_(3),leading to a reduction of MoO_(3),and finally,the reduced MoO_(3)was re-oxidized by O_(2),returning to the initial state.These findings offer valuable insights not only for the development of efficient FeMo catalysts but also for elucidating the reaction mechanism involved in the oxidation of DME to formaldehyde,contributing to the optimized utilization of DME derived from fossil resources.
基金support from the National Natural Science Foundation of China(Nos.21804062,52071171,and 52202248)Liaoning BaiQianWan Talents Program(No.LNBQW2018B0048)+8 种基金Shenyang Science and Technology Project(No.21-108-9-04)Key Research Project of Department of Education of Liaoning Province(No.LJKZZ20220015)Australian Research Council(ARC)through Future Fellowship(No.FT210100298)Discovery Project(No.DP220100603)Linkage Project(Nos.LP210200504,LP220100088,and LP230200897)Industrial Transformation Research Hub(No.IH240100009)schemesthe Australian Government through the Cooperative Research Centres Projects(No.CRCPXIII000077)the Australian Renewable Energy Agency(ARENA)as part of ARENA’s Transformative Research Accelerating Commercialisation Program(No.TM021)European Commission’s Australia-Spain Network for Innovation and Research Excellence(AuSpire).
文摘Herein we report the facial detection of formaldehyde(FA)by using an interesting red acidichromic carbon dots(ACDs)which turns blue when pH gradually decreases.The color change was attributed to the conversion between the double bonds(C=N)and single bonds(C-N)on the surface of the ACDs.Inspired by the reaction between FA and ammonium chloride that produces H^(+)and methenamine and decrease the pH value of the solution,a fast and simple visual detection method for FA was found with a minimum discriminated concentration of 0.04 mol/L.A fluorescence detection method for FA was also found with LOD of 0.029 mol/L and FA in real sample,e.g.,shredded squid was successfully analyzed.This work provides a new idea of developing fast visual detection method for daily monitor or in-site semiquantitative assessment on FA.
基金supported by the Scientific Research Project of Hunan Provincial EducationDepartment(No.22B0458)the National Natural Science Foundation of China(No.52270102).
文摘A chain of GdCe oxides boosted biochars derived from maize straw and sewage sludge(GdyCe1-y/MPBs)were fabricated for formaldehyde(HCHO)catalytic decomposition.The ingenerate relationship between the abatement performance and corresponding structural feature was comprehensively evaluated by XPS,in situ DRIFTS,BET,XRD,SEM and H_(2)-TPR.Meanwhile,10%Gd0.25Ce0.75/MPB exhibited excellent performance,favorable SO_(2) and moisture toleration over a broad temperature range from 160 to 320℃,where it achieved 96.8%removal efficiency with 90.5%selectivity at 200℃.The single or united effects of O_(2),SO_(2),H_(2)O on HCHO abatement over 10%Gd_(0.25)Ce_(0.75)/MPB were tested,and the findings demonstrated that the suppressive effects of SO_(2) and H_(2)O outweighed the promoting influence of O_(2) within a specific range.Gd and Ce co-modified MPB revealed superior HCHO removal capability in contrast to that of Gd or Ce severally modified MPB,ascribing to the synergistic effect of GdO_(x) and CeO_(x) and benefitting from the augmentation of surface area and total pore volume,the aggrandizement of surface active oxygen species,the promotion of redox ability and the inhibition crystallization of CeO_(x).According to in situ DRIFTS,a series of intermediates including formate species and dioxymethylene(DOM)were produced,which would eventually decompose into H_(2)O and CO_(2).In addition,the mass transfer and diffusion of the reactants along with the accessibility of the catalytic sites were enlarged by the hierarchical porous structure of the support,which were also answerable for its distinguished catalytic performance.Furthermore,10%Gd0.25Ce0.75/MPB possessed remarkable potential for industrial applications.
文摘Vanadium phosphorus oxide(VPO)catalyst is a promising candidate for the condensation reaction of formaldehyde(FA)and acetic acid(HAc)to produce acrylic acid(AA).However,the complexity of the active phases and their dynamic interconversion under redox conditions has led to controversies regarding the actual active phase in this reaction.To address this,this study systematically investigates the phase transition and underlying mechanism of VPO catalysts under reaction conditions.X-ray diffraction(XRD)patterns,Raman spectra,transmission electron microscopy images and X-ray photoelectron spectroscopy collectively demonstrated that the V^(4+)phase(VO)_(2)P_(2)O_(7)retained the bulk phase structure throughout the reaction,with only minor surface phase transition observed.In contrast,the V^(5+)phase underwent reduction to other phases in both bulk and surface regions.Specifically,theδ-VOPO_(4)phase rapidly transformed into theαII-VOPO_(4)phase,which could reversibly convert into the R1-VOHPO_(4)phase(V^(4+)).Controlled variable experiments,H_(2)-temperature programmed reduction and in-situ XRD experiments in a hydrogen atmosphere further demonstrated that these phase transitions were primarily attributed to the loss of lattice oxygen.The presence of V^(4+)phase in VPO catalysts enhanced the selectivity of acrylic acid,while the existence of V^(5+)phase promoted the activation of acetic acid.This work elucidates the redox-driven phase evolution of VPO catalysts and offers valuable insights for designing efficient catalysts for FA-HAc cross-condensation by balancing phase stability and activity.
基金supported by the National Natural Science Foundation of China(21663032 and 22061041)the Open Sharing Platform for Scientific and Technological Resources of Shaanxi Province(2021PT-004)the National Innovation and Entrepreneurship Training Program for College Students of China(S202110719044)。
文摘The SiO_(2) inverse opal photonic crystals(PC)with a three-dimensional macroporous structure were fabricated by the sacrificial template method,followed by infiltration of a pyrene derivative,1-(pyren-8-yl)but-3-en-1-amine(PEA),to achieve a formaldehyde(FA)-sensitive and fluorescence-enhanced sensing film.Utilizing the specific Aza-Cope rearrangement reaction of allylamine of PEA and FA to generate a strong fluorescent product emitted at approximately 480 nm,we chose a PC whose blue band edge of stopband overlapped with the fluorescence emission wavelength.In virtue of the fluorescence enhancement property derived from slow photon effect of PC,FA was detected highly selectively and sensitively.The limit of detection(LoD)was calculated to be 1.38 nmol/L.Furthermore,the fast detection of FA(within 1 min)is realized due to the interconnected three-dimensional macroporous structure of the inverse opal PC and its high specific surface area.The prepared sensing film can be used for the detection of FA in air,aquatic products and living cells.The very close FA content in indoor air to the result from FA detector,the recovery rate of 101.5%for detecting FA in aquatic products and fast fluorescence imaging in 2 min for living cells demonstrate the reliability and accuracy of our method in practical applications.
基金the National Natural Science Foundation of China(No.22372104)the Shenzhen Science and Technology Program(Nos.ZDSYS20220527171401003 and KQTD20190929173914967)+1 种基金Guangdong College Students Science and Technology Innovation Cultivation Special Fund Project(No.pdjh2024a315)The authors also acknowledge the Instrumental Analysis Center of Shenzhen University(Xili Campus)for their assistance on TEM observation.
文摘The formaldehyde oxidation reaction(FOR)on a Cu-based electrocatalyst enables hydrogen(H_(2))at the anode in OH−solution,facilitating a bipolar H_(2) production system at ultra-low electrolysis voltage.However,the specific impact of*OH adsorption on the Cu surface regarding the FOR has been rarely investigated.Herein,the strong*OH adsorption Cu(S-OH Cu)electrode,which exhibits high activity and excellent stability of FOR,is developed to investigate the specific impact of*OH adsorption on the Cu surface during the FOR process.Impressively,the increased*OH adsorption on the Cu electrode,typically regarded as a poisoning effect that diminishes inherent FOR activity by reducing the adsorption of intermediate reactants,is firstly revealed as an OH-induced favorable reconstruction effect that significantly improves FOR stability.Specifically,the dual functions of OH-induced favoring reconstruction include accelerating the phase transition of the Cu(0)/Cu(I)redox cycle to refresh the active site and optimizing surface reconstruction to preferentially generate Cu(220)with stronger adsorption energy for H_(2)C(OH)O*and lower C−H barrier energy during FOR.This work provides a promising strategy for designing stable Cu electrocatalysts for FOR to produce hydrogen with extremely low energy input.
基金supported by Yunnan Fundamental Research Projects(No.202101AT070003)the National Natural Science Foundation of China(No.42365007).
文摘Multi-axial differential optical absorption spectroscopy(MAX-DOAS)measurements were conducted in Xishuangbanna,Yunnan,China,between November 1,2021 and June 30,2022 to obtain vertical distributions of formaldehyde(HCHO)and glyoxal(CHOCHO).The observations show an increase in vertical column densities(VCDs)and volume mixing ratios(VMRs)for both HCHO and CHOCHO concentrations during periods of biomass combustion.The VCDs of HCHO and CHOCHO from TROPOMI are in good agreementwith the MAX-DOAS observations.(R^(2) HCHO=0.71;R^(2) CHOCHO=0.70).Regarding seasonal variations,HCHO predominantly occupies the upper layer(400-800 m)during the biomass burning,possibly attributed to the formation of secondary HCHO as the plume ascends during combustion.CHOCHO is primarily found in the lower layer(0-200 m),suggesting a longer lifespan for HCHO compared to CHOCHO,preventing the latter from diffusing to higher altitudes.Concerning the daily variation patterns,both HCHO and CHOCHO VMRs exhibited peaks at 9:00 and 13:00,which were attributed to the nighttime accumulation and midday oxidation.Furthermore,we also investigated the sources of volatile organic compounds(VOCs)using the CHOCHO to HCHO ratio(RGF).During the period of biomass burning,there are minimal differences in the daily RGF across layers,indicating that biomass burning is the predominant source.During the non-biomass burning period,the daily RGF shows significant differences among layers,indicating that emissions from biological and anthropogenic sources primarily contribute during the period.
基金supported by the National Key Research and Development Program of China(No.2016YFC0207100).
文摘Nowadays,it is still a challenge to prepared high efficiency and low cost formaldehyde(HCHO)removal catalysts in order to tackle the long-living indoor air pollution.Herein,δ-MnO_(2)is successfully synthesized by a facile ozonation strategy,where Mn^(2+)is oxidized by ozone(O_(3))bubble in an alkaline solution.It presents one of the best catalytic properties with a low 100%conversion temperature of 85℃for 50 ppm of HCHO under a GHSV of 48,000 mL/(g·hr).As a comparison,more than 6 times far longer oxidation time is needed if O3 is replaced by O_(2).Characterizations show that ozonation process generates a different intermediate of tetragonalβ-HMnO_(2),which would favor the quick transformation into the final productδ-MnO_(2),as compared with the relatively more thermodynamically stable monoclinicγ-HMnO_(2)in the O_(2)process.Finally,HCHO is found to be decomposed into CO_(2)via formate,dioxymethylene and carbonate species as identified by room temperature insitu diffuse reflectance infrared fourier transform spectroscopy.All these results show great potency of this facile ozonation routine for the highly activeδ-MnO_(2)synthesis in order to remove the HCHO contamination.
基金support by the Natural Science Foundation of Jiangsu Province(BK20210867,BK20231342)the China Postdoctoral Science Foundation(2024M752349)+1 种基金National Natural Science Foundation of China(U1604121)the Doctor Project of Mass Entrepreneurship and Innovation in Jiangsu Province.
文摘CO2 hydrogenation to formate is an effective strategy for promoting the sustainable carbon cycle.However,formate yields are significantly influenced by the amount of noble metal(e.g.,Pd)used.Here,we present Pd-Ni synergistic catalysis on the hollow NiCo2O4 spinel arrays(PdxNiy/NCO@CC)for enhanced formate production under mild conditions.The Pd-Ni dual-site structure effectively enhances electron accumulation on Pd via charge polarization and the synergistic interaction between Pd and Ni,leading to significantly improved formate yields with a reduced usage of noble metal catalyst.The optimized Pd5Ni5/NCO@CC catalyst achieved a remarkable formate yield of 282.5 molformate molPd^(-1)h^(-1)at 333 K and demonstrated high stability.This strategy of synergistically enhancing catalytic activity via bimetallic sites highlights its advantages in other catalytic fields and practical applications.
基金financially supported by the National Natural Science Foundation of China(No.61973223)the Innovative Talents in Colleges and Universities in Liaoning Province(No.2020389)+3 种基金Liao Ning Revitalization Talents Program(No.XLYC2007051)Liaoning Educational Department Foundation(No.LJKMZ20220762)the Natural Science Foundation of Liaoning Province(No.2021-MS-257)the Young and Middle-aged Scientific and Technological Innovation Talents of Shenyang Science and Technology Bureau(No.RC200352)。
文摘Formaldehyde is a common atmospheric pollutant produced in industrial production and daily life.However,the traditional semiconductor formaldehyde gas sensor cannot work at room temperature,which limits its practical application.Therefore,developing high-performance gas sensors for rapidly and accurately detecting formaldehyde at room temperature is an important topic.In this study,Ti_(3)C_(2)Tx/SnO_(2)heterostructures were constructed,which could selectively detect formaldehyde at room temperature with a response value of 29.16%(10×10^(-6)).In addition,the sensor shows a remarkable theoretical detection limit of 5.09×10^(-9)and good longterm stability.Density functional theory(DFT)simulations reveal that SnO_(2)nano spheres provide the majority of adsorption sites that strongly interact with formaldehyde.Meanwhile,Ti_(3)C_(2)T_(x)acting as a conductive layer facilitates the transfer of charge carriers so that they show a sensing response to formaldehyde at room temperature.Moreover,the formation of p-n heterostructures between SnO_(2)and Ti_(3)C_(2)T_(x)boosts the Schottky barrier at the interface,which is the critical factor in enhancing the sensing properties by turning the Schottky barrier upon introducing formaldehyde gas.This perspective is expected to provide instructive guidance for utilizing MXene/metal oxide nanocomposites to improve the gas sensing performance at room temperature.
文摘Changes in CO2 and temperature are correlated, but it is difficult to observe which is the cause and which is the effect. The release of CO2 dissolved in the ocean into the atmosphere depends on the atmospheric temperature. However, examining the relationship between changes in CO2 caused by other phenomena and temperature is difficult. Studies of soil respiration (Rs) since the late 20th century have shown that CO2 emissions from soil respiration (Rs) are overwhelmingly greater than CO2 emissions from fossil fuel combustion. This is also noted in the IPCC carbon budget assessment. In this paper, the dependences of Rs on temperature, time, latitude, precipitation, seasons, etc., were investigated using the latest NASA database. The changes in temperature and Rs correlated well. There is also a good correlation between Rs and CO2 generation. Therefore, an increase in temperature results in an increase in CO2. On the other hand, there is no evidence other than model calculations that an increase in anthropogenic CO2 is mainly linked to a rise in temperature. The idea that global warming is caused by anthropogenic CO2 production is still a hypothesis. For these reasons, the relationship between global warming and anthropogenic CO2 should be reconsidered based on physical evidence without preconceptions. .
基金Funded by the Young and Middle-aged Academic and Technical Leaders Reserve Talent Project of Yunnan Province(No.202105AC160054)。
文摘In the preparation of a series of Ce_(0.8)Zr_(0.2)O_(y)catalysts catalyzing the removal of formaldehyde,BET,H2-TPR,IR,SEM,XPS,and XRD were used to characterize the catalyst,and the influence of humidity on the catalyst activity was studied by adjusting the humidity during the process.The experimental results showed that the formaldehyde removal rate increased with the increase of humidity.When the humidity was higher than 50%,the formaldehyde removal rate decreased by 3%over that when the humidity was 50%.The characterization results showed that humidity facilitated the activation of oxygen and the formation of hydroxyl groups,which both promoted the formation and oxidative decomposition of intermediates and prevented the deposition of intermediates that clogged the pores,allowing more formaldehyde to be adsorbed and oxidized,which increased the activity of the catalyst.This provides new mechanistic evidence for the oxidation of formaldehyde and helps in the development of relatively low-cost materials for formaldehyde purification.
