Selective depression of pyrite remains a major bottleneck in copper flotation,particularly when high-pyrite ores are processed and saline water is used.In such environments,conventional approaches using lime and inert...Selective depression of pyrite remains a major bottleneck in copper flotation,particularly when high-pyrite ores are processed and saline water is used.In such environments,conventional approaches using lime and inert grinding media often fail to discriminate ef-fectively between pyrite and valuable copper minerals due to strong copper activation on pyrite surfaces.This study introduced a novel approach using inorganic radicals generated from peroxymonosulfate(PMS)to selectively oxidize and depress pyrite.Flotation tests with synthetic high-pyrite ore blends showed that PMS significantly reduced pyrite recovery while maintaining or improving chalcopyrite flot-ation.Ethylenediaminetetraacetic acid(EDTA)extraction confirmed selective oxidation of pyrite,and electron paramagnetic resonance(EPR)spectroscopy identified hydroxyl(·OH)and sulfate(SO_(4)^(·-))radicals as the dominant reactive species.Iron ions from grinding me-dia and mineral surfaces were identified as key activators of PMS.A major insight was pyrite’s dual role,acting both as a radical scav-enger and an activator,which made it highly reactive and susceptible to radical-induced oxidation.This process converted surface copper-sulfur species into copper hydroxides,effectively suppressing pyrite flotation.While previous studies have applied EPR to detect radicals in simplified activator/precursor systems,this study provides the first direct mechanistic evidence of radical-driven selectivity in flotation by detecting inorganic radicals in a complex flotation slurry,thereby demonstrating their persistence under industrially relevant conditions and establishing a foundation for more effective and targeted flotation strategies.展开更多
Electrocatalytic oxidation of glycerol for value-added chemicals is a superior strategy to utilize the excess glycerol produced in the biodiesel industry.Pd is one of the few active catalysts for alkaline glycerol oxi...Electrocatalytic oxidation of glycerol for value-added chemicals is a superior strategy to utilize the excess glycerol produced in the biodiesel industry.Pd is one of the few active catalysts for alkaline glycerol oxidation reaction(GOR);however,glycerol inevitably dissociates and converts to carbon dioxide on the Pd surface,which results in its low total Faradaic efficiency(FE)for high-value-added products.Herein,a series of Pd/C and Pd10Bix/C catalysts were synthesized to investigate the GOR pathway.The Pd10Bi3/C catalyst with optimal Bi content achieved an excellent GOR mass activity of 7.5±0.2 A mgPd−1 and an outstanding total FE of 90%±3%,which are much higher than those values on Pd/C(1.2±0.2 A mgPd−1 for mass activity and 63%±4%for total FE).Combined results of in-situ attenuated total reflection surface enhanced infrared absorption spectroscopy and density functional theory calculations show that Bi suppresses the dissociation of glycerol through the“shielding effect”of Bi to the adjacent Pd sites,which weakens the adsorption strength of GOR intermediates on those sites.This work provides a new insight into the GOR mechanism and puts forward a valid strategy for the rational design of catalysts to enable the transformation of glycerol into high-value-added products.展开更多
The effective separation and utilization of photo-generated carriers are of great significance for promoting the development of photocatalysis,especially in the coupled process of photocatalytic H_(2)production and va...The effective separation and utilization of photo-generated carriers are of great significance for promoting the development of photocatalysis,especially in the coupled process of photocatalytic H_(2)production and valueadded chemicals synthesis.To realize this goal,a sandwichstructured MnO_(2)@ZnIn_(2)S_(4)@Ti_(3)C_(2)hollow sphere was designed and synthesized,in which MnO_(2)and Ti_(3)C_(2)were loaded on the inner and outer surfaces of ZnIn_(2)S_(4),respectively.In the photocatalytic system,MnO_(2)as oxidation cocatalyst and Ti_(3)C_(2)as reduction cocatalyst can serve as photo-generated holes and electrons collectors,respectively,which boost the photo-generated carrier separation and create a spatially separated redox reaction.Furthermore,the unique hollow structure integrated into the photocatalytic system further endows a significant enhancement in light-harvesting ability.Remarkably,the optimal MnO_(2)@ZnIn_(2)S_(4)@Ti_(3)C_(2)hollow sphere exhibits an outstanding the photocatalytic activity for coupled H_(2)production(6.29 mmol g^(-1)h^(-1))and selective benzyl alcohol oxidation to benzaldehyde(5.26 mmol g^(-1)h^(-1)),which is significantly superior to that of ZnIn_(2)S_(4),MnO_(2)@ZnIn_(2)S_(4),and ZnIn_(2)S_(4)@Ti_(3)C_(2).By the in situ irradiated X-ray photoelectron spectroscopy,the result reveals that the spatially separated redox dual-cocatalysts can effectively impel the photo-generated carrier separation.Simultaneously,the intermediates during the benzyl alcohol oxidation process have also been confirmed through in situ electron paramagnetic resonance spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy.This work provides a reference and inspiration for constructing efficient photocatalysts that achieve an efficient coupling of photocatalytic H_(2)production and value-added chemicals synthesis.展开更多
This study systematically explored the oxidation behavior of a Ni-10Cr alloy without and with surface spraying hexagonal closed pack(hcp)-structuredα-Al_(2)O_(3)or α-Fe_(2)O_(3)nanoparticles.Despite the distinct equ...This study systematically explored the oxidation behavior of a Ni-10Cr alloy without and with surface spraying hexagonal closed pack(hcp)-structuredα-Al_(2)O_(3)or α-Fe_(2)O_(3)nanoparticles.Despite the distinct equilibrium dissociation oxygen partial pressure of the two kinds of oxide nanoparticles,they both contributed to the selective oxidation of Ni-10Cr alloy,achieving the transition from internal Cr oxidation to external Cr_(2)O_(3)scale formation.Nano-scaled characterization indicates that a coherent interface was developed between the newly grown Cr_(2)O_(3)grains and the hcp-structured oxide nanoparticles,whereby promoting epitaxial Cr_(2)O_(3)nucleation surrounding the nanoparticles and kinetically accelerating the formation of a continuous Cr_(2)O_(3)scale at the transient oxidation stage.The findings provide new insights into the selective oxidation mechanism of alloys with low Cr contents.展开更多
Defect engineering in metal organic frameworks(MOFs)has captured significant attention in the field of photocatalysis.A series of UiO-66(Ce)(UiO=University of Oslo)MOFs with different contents of missing-linker defect...Defect engineering in metal organic frameworks(MOFs)has captured significant attention in the field of photocatalysis.A series of UiO-66(Ce)(UiO=University of Oslo)MOFs with different contents of missing-linker defects have been developed for the photocatalytic selective oxidation of benzylamine(BA)and thioanisole(TA)under visible light.The introduction of missing-linker defects promotes the formation of unsaturated Ce sites with a high Ce3+content.It also generates a high concentration of oxygen vacancies.In situ Fourier transform infrared spectroscopy(FTIR)results revealed that BA and TA molecules were activated on coordinatively unsaturated Ce sites via the H-N…Ce and the C-S…Ce interactions,respectively.Simulated in situ electron paramagnetic resonance(EPR)data indicate that O_(2) activation and reduction occur at coordinatively unsaturated Ce^(3+)sites to form·O_(2)^(-).This is accelerated by the Ce^(3+)/Ce^(4+)redox cycle associated with the photogenerated electrons.The corresponding photogenerated holes are involved in the deprotonation of the activated BA and TA.The most active sample exhibits 98.4%and 95.5%conversion rates for BA and TA oxidation.Mechanisms for the molecular activation are proposed at the molecular level.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
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
The photocatalytic selective oxidation of biomass-derived 5-hydroxymethylfurfural(HMF)offers a sustainable alternative to thermal catalysis.However,the efficiency of this process is significantly limited by inadequate...The photocatalytic selective oxidation of biomass-derived 5-hydroxymethylfurfural(HMF)offers a sustainable alternative to thermal catalysis.However,the efficiency of this process is significantly limited by inadequate light absorption efficiency and the rapid recombination of photogenerated charge carriers in conventional photocatalysts.Herein,we developed a Co_(3)O_(4)/ZnIn_(2)S_(4)(Co_(3)O_(4)/ZIS)photocatalyst,in which Co_(3)O_(4)functions as a multifunctional cocatalyst.This photocatalyst significantly enhances the chemisorption and activation of HMF molecules through interfacial oxygen-hydroxyl interactions.Additionally,the incorporation of narrow-band gap Co_(3)O_(4)broadens the optical absorption range of the composite photocatalyst.Besides,integrating Co_(3)O_(4)with ZnIn_(2)S_(4)leads to a 5.9-fold increase in charge separation efficiency compared to pristine ZnIn_(2)S_(4).The optimized Co_(3)O_(4)/ZIS-3 photocatalyst(3 wt% Co_(3)O_(4)loading)exhibits exceptional selectivity and yield for 2,5-diformylfuran(DFF)under visible light irradiation,achieving 70.4%DFF selectivity with a 5.4-fold enhancement compared to pristine ZnIn_(2)S_(4).Scavenger experiments and electron spin resonance(ESR)spectroscopy indicate that superoxide radicals(O_(2)^(-))and h^(+)are the main active species driving the photocatalytic oxidation of HMF.Molecular simulations reveal that the activation of HMF and the transformation of the intermediate^(*)MF to^(*)DFF are more favorable over the Co_(3)O_(4)/ZIS composite due to lower activation barriers compared to those over ZnIn_(2)S_(4).Through this work,we aim to design highly efficient and affordable photocatalysts for biomass valorization and contribute valuable insights into the mechanisms of photocatalytic oxidation of HMF.展开更多
The methane selective oxidation was a"holy grail"reaction.However,peroxidation and low selectivity limited the application.Herein,we combined three Au contents with TiO_(2)in both encapsulation(xAu@TiO_(2))a...The methane selective oxidation was a"holy grail"reaction.However,peroxidation and low selectivity limited the application.Herein,we combined three Au contents with TiO_(2)in both encapsulation(xAu@TiO_(2))and surface-loaded(xAu/TiO_(2))ways by MOF derivation strategy,reported a catalyst 0.5Au@TiO_(2)exhibited a CH_(3)OH yield of 32.5μmol·g^(-1)·h^(-1)and a CH_(3)OH selectivity of 80.6%under catalytic conditions of only CH_(4),O_(2),and H_(2)O.Mechanically speaking,the catalytic activity was controlled by both electron-hole separation efficiency and core-shell structure.The interfacial contact between Au nanoparticles and TiO_(2)in xAu@TiO_(2)and xAu/TiO_(2)induced the formation of oxygen vacancies,with 0.5 Au content showing the highest oxygen vacancy concentration.At the same Au content,xAu@TiO_(2)generated more oxygen vacancies than xAu/TiO_(2).The oxygen vacancy acted as an effective electron cold trap,which enhanced the photogenerated carrier separation efficiency and thereby improved the catalytic activity.In-situ DRIFTs revealed that the isolated OH(non-hydrogen bond adsorption)were key species for the methane selective oxidation,playing a role in the activation of CH_(4)to^(*)CH_(3).However,an overabundance of isolated OH led to severe overoxidation.Fortunately,the core-shell structure over xAu@TiO_(2)provided a slow-release environment for isolated OH through the intermediate state of^(*)OH(hydrogen bond adsorption)to balance the formation rate and consumption rate of isolated OH,doubling the methanol yield and increasing the>29%selectivity.These results showed a new strategy for the control of the overoxidation rate via a strategy of MOF encapsulation followed by pyrolytic derivation for methane selective oxidation.展开更多
For the effective treatment of the wastewater with low-medium concentration ammonia nitrogen and low strength COD,a high-performance Co_(3)O_(4) catalyst supported on carbon nanocages(CNCs)was prepared.By isovolumetri...For the effective treatment of the wastewater with low-medium concentration ammonia nitrogen and low strength COD,a high-performance Co_(3)O_(4) catalyst supported on carbon nanocages(CNCs)was prepared.By isovolumetric im pregnation,Co_(3)O_(4) could be uniformly dispersed on surface of CNCs,which possess tiny particle size and strong electron transfer capability.The catalytic performance of the prepared Co_(3)O_(4)/CNCs catalysts with different Co_(3)O_(4) loadings was systematically evaluated and compared with Co_(3)O_(4)/CNTs.It is found that 20 wt.%Co_(3)O_(4)/CNCs shows the best catalytic performance,achieving an ammonia nitrogen conversion rate of 71.0%and a nitrogen selectivity of 81.8%.Compared to commonly used Co_(3)O_(4),ammonia conversion and nitrogen selectivity of Co_(3)O_(4)/CNCs increased by 28.9%and 15.8%respectively.In the five consecutive cycles,the catalytic activity remained stable.The mechanism that CNCs support effectively increases the surface oxygen vacancies of Co_(3)O_(4) through XPS analysis was also elucidated,and DFT calculations confirm strong electron transfer between CNCs and Co_(3)O_(4),rendering Co_(3)O_(4) nanoparticles as the primary catalytic active sites.The results may contribute to the development of highperformance catalytic ozone oxidation catalysts for ammonia nitrogen.展开更多
The methylene-selective oxidation of simple alkanes catalyzed by a nonheme iron(Ⅲ)-monoamidate complex using H_(2)O_(2)as the terminal oxidant is reported.Mechanistic studies suggest that iron(V)-oxo species is the a...The methylene-selective oxidation of simple alkanes catalyzed by a nonheme iron(Ⅲ)-monoamidate complex using H_(2)O_(2)as the terminal oxidant is reported.Mechanistic studies suggest that iron(V)-oxo species is the active intermediate,undergoing hydrogen atom abstraction(HAA)as the rate-determining step to initiate C-H bond activation.展开更多
To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretre...To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.展开更多
Photoelectrocatalytic(PEC)seawater splitting as a green and sustainable route to harvest hydrogen is attractive yet hampered by low activity of photoanodes and unexpected high selectivity to the corrosive and toxic ch...Photoelectrocatalytic(PEC)seawater splitting as a green and sustainable route to harvest hydrogen is attractive yet hampered by low activity of photoanodes and unexpected high selectivity to the corrosive and toxic chlorine.Especially,it is full of challenges to unveil the key factors influencing the selectivity of such complex PEC processes.Herein,by regulating the energy band and surface structure of the anatase TiO_(2) nanotube array photoanode via nitrogen-doping,the seawater PEC oxidation shifts from Cl^(-)oxidation reaction(ClOR)dominant on the TiO_(2) photoanode(61.6%)to oxygen evolution reaction(OER)dominant on the N-TiO_(2) photoanode(62.9%).Comprehensive investigations including operando photoelectrochemical FTIR and DFT calculations unveil that the asymmetric hydrogen-bonding water at the N-TiO_(2) electrode/electrolyte interface enriches under illumination,facilitating proton transfer and moderate adsorption strength of oxygen-intermediates,which lowers the energy barrier for the OER yet elevates the energy barrier for the ClOR,resulting to a promoted selectivity towards the OER.The work sheds light on the underlying mechanism of the PEC water oxidation processes,and highlights the crucial role of interfacial water on the PEC selectivity,which could be regulated by controlling the energy band and the surface structure of semiconductors.展开更多
Electrochemical nitrogen looping represents a promising carbon-free and sustainable solution for the energy transition,in which electrochemical ammonia oxidation stays at the central position.However,the various nitro...Electrochemical nitrogen looping represents a promising carbon-free and sustainable solution for the energy transition,in which electrochemical ammonia oxidation stays at the central position.However,the various nitrogen-containing intermediates tend to poison and corrode the electrocatalysts,even the state-of-the-art noble-metal ones,which is worsened at a high applied potential.Herein,we present an ultrarapid laser quenching strategy for constructing a corrosion-resistant and nanostructured CuNi alloy metallic glass electrocatalyst.In this material,single-atom Cu species are firmly bonded with the surrounding Ni atoms,endowing exceptional resistance against ammonia corrosion relative of conventional CuNi alloys.Remarkably,a record-high durability for over 300 h is achieved.Ultrarapid quenching also allows a much higher Cu content than typical single-atom alloys,simultaneously yielding a high rate and selectivity for ammonia oxidation reaction(AOR).Consequently,an outstanding ammonia conversion rate of up to 95%is achieved with 91.8%selectivity toward nitrite after 8 h.Theoretical simulations reveal that the structural amorphization of CuNi alloy could effectively modify the electronic configuration and reaction pathway,generating stable singleatom Cu active sites with low kinetic barriers for AOR.This ultrarapid laser quenching strategy thus provides a new avenue for constructing metallic glasses with well-defined nanostructures,presenting feasible opportunities for performance enhancement for AOR and other electrocatalytic processes.展开更多
In this work,a series of Ce-Ti composite oxides with different Ti/Ce molar ratios was prepared by coprecipitation method,and investigated for the catalytic degradation of toluene and selective catalytic reduction of N...In this work,a series of Ce-Ti composite oxides with different Ti/Ce molar ratios was prepared by coprecipitation method,and investigated for the catalytic degradation of toluene and selective catalytic reduction of NO.The phase transition process between Ce species and Ti species is limited by modulating the interaction between Ce4+and Ti4+,while a completely amorphous composite is generated with an appropriate molar ratio of Ti/Ce(1.5/1).The catalyst CeTi1.5Oxexhibits the best catalytic performance,where the values of T90and T50for deep degradation of toluene are 297 and 330℃respectively at high weight hours space velocity(WHSV=120000 mL/(g·h)).Compared with CeO_(2),T90and T50decrease by48 and 34℃respectively while declining by 67 and 70℃compared to TiO_(2).For the SCR reaction,CeTi1.5Oxreaches 100%NO conversion at 250℃with WHSV=60000 mL/(g·h),reduced by 50℃compared to pure CeO_(2).The amorphous nanostructure with highly dispersed Ce and Ti species was confirmed by transmission electron microscopy(TEM)and X-ray diffraction(XRD)characterizations.The X-ray photoelectron spectroscopy(XPS)and Raman analyses show that a large number of active Ce-O-Ti species and surface oxygen vacancies are generated due to the strong interaction between Ti^(4+)and Ce^(4+)in CeTi_(1.5)O_(x).Additionally,H_(2)-TPR and O_(2)-TPD further confirm that the interaction promotes the low-temperature reducibility and mobility of surface-active oxygen species.Meanwhile,in-situ DRIFTS study reveals that CeTi1.5Oxwith amorphous nanostructure can dramatically enhance the dissociative and complete oxidation capacity for toluene.展开更多
Electrocatalysis,a form of heterogeneous catalysis,is closely associated with both catalyst properties and the catalyst/electrolyte interfacial microenvironment.Herein,we rationally design and synthesize a unique PdCu...Electrocatalysis,a form of heterogeneous catalysis,is closely associated with both catalyst properties and the catalyst/electrolyte interfacial microenvironment.Herein,we rationally design and synthesize a unique PdCu nano-sea urchins(PdCu NSUs)featured with high-curvature nanotips,by which the interfacial microenvironment is expected to be tailored to the electrocatalytic reactions.PdCu NSUs exhibit excellent activity for ethanol electrooxidation,with a specific activity of 4.11 mA cm^(-2)and a mass activity of 2.24 mAμg_(Pd)^(-1),and a high Faraday efficiency(FE)of 96.4%toward acetic acid.COMSOL finite element simulations confirm that the unique nanotips could induce a local electric field due to the accumulation of positive charges in the nanotips,resulting in enrichment of OH^(-)at the catalyst surface to promote the formation of Pd-OH_(ads),a species required by ethanol dehydrogenation.Furthermore,DFT calculations and in-situ electrochemical Fourier transform infrared spectroscopy discover that the d-band center of Pd significantly downshifts in PdCu alloy,which facilitates the desorption of the produced acetic acid.This work provides a new electrocata lytic material with high-curvature nanotips,and also clarifies how the material morphology,by inducing local electric fields,affects the interfacial microenvironment and thus the catalytic activity and selectivity.展开更多
In this paper,we establish and study a single-species logistic model with impulsive age-selective harvesting.First,we prove the ultimate boundedness of the solutions of the system.Then,we obtain conditions for the asy...In this paper,we establish and study a single-species logistic model with impulsive age-selective harvesting.First,we prove the ultimate boundedness of the solutions of the system.Then,we obtain conditions for the asymptotic stability of the trivial solution and the positive periodic solution.Finally,numerical simulations are presented to validate our results.Our results show that age-selective harvesting is more conducive to sustainable population survival than non-age-selective harvesting.展开更多
Gold nanoparticles(AuNPs)supported on the Cu-doped LaMnO_(3)perovskites exhibit strong Au-Mn-Cu synergy in the aerobic oxidation of gaseous ethanol to acetaldehyde(AC).The Au/LaMnCuO_(3)catalysts achieve AC yields exc...Gold nanoparticles(AuNPs)supported on the Cu-doped LaMnO_(3)perovskites exhibit strong Au-Mn-Cu synergy in the aerobic oxidation of gaseous ethanol to acetaldehyde(AC).The Au/LaMnCuO_(3)catalysts achieve AC yields exceeding 90%and a space-time yield of 715 g_(AC)g_(AU)^(-1)h^(-1)at 225℃,outperforming reported catalysts.The outstanding performance is attributed to adjacent Cu^(+)and Mn^(2+)ions in the perovskite surface,which,together with nearby AuNPs,contribute to the high activity and stability.The best-performing catalyst contains a Cu/Mn ratio of 1/3 in the perovskite.Doping too much Cu into the perovskite leads to metallic Cu,suppressing catalyst performance.Density functional theory(reaction energetics,electronic structure analysis)and microkinetics simulations aided in understanding the synergy between Cu and Mn and the role of AuNPs.The reaction involves two H abstraction steps:(1)O-H cleavage of adsorbed ethanol by the basic perovskite lattice oxygen atom and(2)α-C-H cleavage by AuNPs,yielding AC and adsorbed water.Molecular O_(2)adsorbs in the oxygen vacancy(O_(V))formed by water removal,generating a peroxide anion(O_(2)^(2-))as the activated oxygen species.In the second part of the catalytic cycle,the basic O_(2)^(2-)species abstracts the H atom from another ethanol molecule,followed byα-C-H cleavage by AuNPs,AC production,and water removal.Water formation in the second part of the catalytic cycle is the rate-controlling step for Au/LaMnO_(3)and Au/LaMnCuO_(3)models.Moderate Cu doping enhances the essential Cu^(+)-OV-Mn^(2+)sites and lowers the barrier for water formation due to the weaker Cu-O bond than the Mn-O bond.In contrast,excessive Cu doping creates unstable Cu^(2+)-O-Cu^(2+)sites and shifts the barrier to theα-C-H cleavage.展开更多
Ethylene glycol(EG)is a biomass derivative of polyethylene terephthalate(PET),and its electrocatalytic conversion into high-value chemicals has sparked widespread interest.This study reviews the most recent research d...Ethylene glycol(EG)is a biomass derivative of polyethylene terephthalate(PET),and its electrocatalytic conversion into high-value chemicals has sparked widespread interest.This study reviews the most recent research development in electrocatalysis-based EG to glycolic acid(GA)conversion.Firstly,the strategies and research results of modulating the electronic structure of catalysts for efficient selective GA production from EG are reviewed.Second,by reviewing the data of in-situ Fourier transform infrared spectroscopy and in-situ electrochemically attenuated total reflection surface enhanced infrared absorption spectroscopy,the reaction pathway and catalytic mechanism of EG partial oxidation to GA were clarified.Finally,the design and regulation of catalysts for selective oxidation of EG by electrocatalysis in the future are prospected.展开更多
To explore the formation mechanism of anisotropy in Ti-6Al-4V alloy fabricated by selective laser melting(SLM),the compressive mechanical properties,microhardness,microstructure,and crystallographic orientation of the...To explore the formation mechanism of anisotropy in Ti-6Al-4V alloy fabricated by selective laser melting(SLM),the compressive mechanical properties,microhardness,microstructure,and crystallographic orientation of the alloy across different planes were investigated.The anisotropy of SLM-fabricated Ti-6Al-4V alloys was analyzed,and the electron backscatter diffraction technique was used to investigate the influence of different grain types and orientations on the stress-strain distribution at various scales.Results reveal that in room-temperature compression tests at a strain rate of 10^(-3) s^(-1),both the compressive yield strength and microhardness vary along the deposition direction,indicating a certain degree of mechanical property anisotropy.The alloy exhibits a columnar microstructure;along the deposition direction,the grains appear equiaxed,and they have internal hexagonal close-packed(hcp)α/α'martensitic structure.α'phase has a preferential orientation approximately along the<0001>direction.Anisotropy arises from the high aspect ratio of columnar grains,along with the weak texture of the microstructure and low symmetry of the hcp crystal structure.展开更多
基金support from the Australian Research Council(ARC)Linkage Project(No.LP230100166).
文摘Selective depression of pyrite remains a major bottleneck in copper flotation,particularly when high-pyrite ores are processed and saline water is used.In such environments,conventional approaches using lime and inert grinding media often fail to discriminate ef-fectively between pyrite and valuable copper minerals due to strong copper activation on pyrite surfaces.This study introduced a novel approach using inorganic radicals generated from peroxymonosulfate(PMS)to selectively oxidize and depress pyrite.Flotation tests with synthetic high-pyrite ore blends showed that PMS significantly reduced pyrite recovery while maintaining or improving chalcopyrite flot-ation.Ethylenediaminetetraacetic acid(EDTA)extraction confirmed selective oxidation of pyrite,and electron paramagnetic resonance(EPR)spectroscopy identified hydroxyl(·OH)and sulfate(SO_(4)^(·-))radicals as the dominant reactive species.Iron ions from grinding me-dia and mineral surfaces were identified as key activators of PMS.A major insight was pyrite’s dual role,acting both as a radical scav-enger and an activator,which made it highly reactive and susceptible to radical-induced oxidation.This process converted surface copper-sulfur species into copper hydroxides,effectively suppressing pyrite flotation.While previous studies have applied EPR to detect radicals in simplified activator/precursor systems,this study provides the first direct mechanistic evidence of radical-driven selectivity in flotation by detecting inorganic radicals in a complex flotation slurry,thereby demonstrating their persistence under industrially relevant conditions and establishing a foundation for more effective and targeted flotation strategies.
基金supported by the National Natural Science Foundation of China(Grant number 22172112)and the Fundamental Research Funds for the Central Universities.
文摘Electrocatalytic oxidation of glycerol for value-added chemicals is a superior strategy to utilize the excess glycerol produced in the biodiesel industry.Pd is one of the few active catalysts for alkaline glycerol oxidation reaction(GOR);however,glycerol inevitably dissociates and converts to carbon dioxide on the Pd surface,which results in its low total Faradaic efficiency(FE)for high-value-added products.Herein,a series of Pd/C and Pd10Bix/C catalysts were synthesized to investigate the GOR pathway.The Pd10Bi3/C catalyst with optimal Bi content achieved an excellent GOR mass activity of 7.5±0.2 A mgPd−1 and an outstanding total FE of 90%±3%,which are much higher than those values on Pd/C(1.2±0.2 A mgPd−1 for mass activity and 63%±4%for total FE).Combined results of in-situ attenuated total reflection surface enhanced infrared absorption spectroscopy and density functional theory calculations show that Bi suppresses the dissociation of glycerol through the“shielding effect”of Bi to the adjacent Pd sites,which weakens the adsorption strength of GOR intermediates on those sites.This work provides a new insight into the GOR mechanism and puts forward a valid strategy for the rational design of catalysts to enable the transformation of glycerol into high-value-added products.
基金supported by the National Natural Science Foundation of China(52202102,52472215)Key Innovation Project of the Science-Education-Industry Integration Pilot Engineering of Qilu University of Technology(Shandong Academy of Sciences)(2025ZDZX08)+1 种基金Key Research&Development Project of Shandong Province(2024TSGC0222)Interdisciplinary Innovation Guidance Program from Qilu University of Technology(Shandong Academy of Sciences)(2025XKJC0103)。
文摘The effective separation and utilization of photo-generated carriers are of great significance for promoting the development of photocatalysis,especially in the coupled process of photocatalytic H_(2)production and valueadded chemicals synthesis.To realize this goal,a sandwichstructured MnO_(2)@ZnIn_(2)S_(4)@Ti_(3)C_(2)hollow sphere was designed and synthesized,in which MnO_(2)and Ti_(3)C_(2)were loaded on the inner and outer surfaces of ZnIn_(2)S_(4),respectively.In the photocatalytic system,MnO_(2)as oxidation cocatalyst and Ti_(3)C_(2)as reduction cocatalyst can serve as photo-generated holes and electrons collectors,respectively,which boost the photo-generated carrier separation and create a spatially separated redox reaction.Furthermore,the unique hollow structure integrated into the photocatalytic system further endows a significant enhancement in light-harvesting ability.Remarkably,the optimal MnO_(2)@ZnIn_(2)S_(4)@Ti_(3)C_(2)hollow sphere exhibits an outstanding the photocatalytic activity for coupled H_(2)production(6.29 mmol g^(-1)h^(-1))and selective benzyl alcohol oxidation to benzaldehyde(5.26 mmol g^(-1)h^(-1)),which is significantly superior to that of ZnIn_(2)S_(4),MnO_(2)@ZnIn_(2)S_(4),and ZnIn_(2)S_(4)@Ti_(3)C_(2).By the in situ irradiated X-ray photoelectron spectroscopy,the result reveals that the spatially separated redox dual-cocatalysts can effectively impel the photo-generated carrier separation.Simultaneously,the intermediates during the benzyl alcohol oxidation process have also been confirmed through in situ electron paramagnetic resonance spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy.This work provides a reference and inspiration for constructing efficient photocatalysts that achieve an efficient coupling of photocatalytic H_(2)production and value-added chemicals synthesis.
基金supported by the National Natural Science Foundation of China(No.52301089)the Jiangxi Provincial Key Research and Development Program(No.20232BBE50007).
文摘This study systematically explored the oxidation behavior of a Ni-10Cr alloy without and with surface spraying hexagonal closed pack(hcp)-structuredα-Al_(2)O_(3)or α-Fe_(2)O_(3)nanoparticles.Despite the distinct equilibrium dissociation oxygen partial pressure of the two kinds of oxide nanoparticles,they both contributed to the selective oxidation of Ni-10Cr alloy,achieving the transition from internal Cr oxidation to external Cr_(2)O_(3)scale formation.Nano-scaled characterization indicates that a coherent interface was developed between the newly grown Cr_(2)O_(3)grains and the hcp-structured oxide nanoparticles,whereby promoting epitaxial Cr_(2)O_(3)nucleation surrounding the nanoparticles and kinetically accelerating the formation of a continuous Cr_(2)O_(3)scale at the transient oxidation stage.The findings provide new insights into the selective oxidation mechanism of alloys with low Cr contents.
基金supported by the National Natural Science Foundation of China(Nos.22272026 and 22272028)the 111 Project(No.D16008)Jinhong Bi thanks the Youth Talent Support Program of Fujian Province(No.00387077).
文摘Defect engineering in metal organic frameworks(MOFs)has captured significant attention in the field of photocatalysis.A series of UiO-66(Ce)(UiO=University of Oslo)MOFs with different contents of missing-linker defects have been developed for the photocatalytic selective oxidation of benzylamine(BA)and thioanisole(TA)under visible light.The introduction of missing-linker defects promotes the formation of unsaturated Ce sites with a high Ce3+content.It also generates a high concentration of oxygen vacancies.In situ Fourier transform infrared spectroscopy(FTIR)results revealed that BA and TA molecules were activated on coordinatively unsaturated Ce sites via the H-N…Ce and the C-S…Ce interactions,respectively.Simulated in situ electron paramagnetic resonance(EPR)data indicate that O_(2) activation and reduction occur at coordinatively unsaturated Ce^(3+)sites to form·O_(2)^(-).This is accelerated by the Ce^(3+)/Ce^(4+)redox cycle associated with the photogenerated electrons.The corresponding photogenerated holes are involved in the deprotonation of the activated BA and TA.The most active sample exhibits 98.4%and 95.5%conversion rates for BA and TA oxidation.Mechanisms for the molecular activation are proposed at the molecular level.
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(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financially supported by the National Key Research and Development Program of China(No.2022YFB3805400)the National Natural Science Foundation of China(No.22178297,No.22478327)+3 种基金the Science and Technology Innovation Program of Hunan Province(No.2024RC9009)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDC04010100)the Provincial Natural Science Foundation of Hunan(No.2024JJ5371)the Scientific Research Fund of Hunan Provincial Education Department(No.24A0107)。
文摘The photocatalytic selective oxidation of biomass-derived 5-hydroxymethylfurfural(HMF)offers a sustainable alternative to thermal catalysis.However,the efficiency of this process is significantly limited by inadequate light absorption efficiency and the rapid recombination of photogenerated charge carriers in conventional photocatalysts.Herein,we developed a Co_(3)O_(4)/ZnIn_(2)S_(4)(Co_(3)O_(4)/ZIS)photocatalyst,in which Co_(3)O_(4)functions as a multifunctional cocatalyst.This photocatalyst significantly enhances the chemisorption and activation of HMF molecules through interfacial oxygen-hydroxyl interactions.Additionally,the incorporation of narrow-band gap Co_(3)O_(4)broadens the optical absorption range of the composite photocatalyst.Besides,integrating Co_(3)O_(4)with ZnIn_(2)S_(4)leads to a 5.9-fold increase in charge separation efficiency compared to pristine ZnIn_(2)S_(4).The optimized Co_(3)O_(4)/ZIS-3 photocatalyst(3 wt% Co_(3)O_(4)loading)exhibits exceptional selectivity and yield for 2,5-diformylfuran(DFF)under visible light irradiation,achieving 70.4%DFF selectivity with a 5.4-fold enhancement compared to pristine ZnIn_(2)S_(4).Scavenger experiments and electron spin resonance(ESR)spectroscopy indicate that superoxide radicals(O_(2)^(-))and h^(+)are the main active species driving the photocatalytic oxidation of HMF.Molecular simulations reveal that the activation of HMF and the transformation of the intermediate^(*)MF to^(*)DFF are more favorable over the Co_(3)O_(4)/ZIS composite due to lower activation barriers compared to those over ZnIn_(2)S_(4).Through this work,we aim to design highly efficient and affordable photocatalysts for biomass valorization and contribute valuable insights into the mechanisms of photocatalytic oxidation of HMF.
文摘The methane selective oxidation was a"holy grail"reaction.However,peroxidation and low selectivity limited the application.Herein,we combined three Au contents with TiO_(2)in both encapsulation(xAu@TiO_(2))and surface-loaded(xAu/TiO_(2))ways by MOF derivation strategy,reported a catalyst 0.5Au@TiO_(2)exhibited a CH_(3)OH yield of 32.5μmol·g^(-1)·h^(-1)and a CH_(3)OH selectivity of 80.6%under catalytic conditions of only CH_(4),O_(2),and H_(2)O.Mechanically speaking,the catalytic activity was controlled by both electron-hole separation efficiency and core-shell structure.The interfacial contact between Au nanoparticles and TiO_(2)in xAu@TiO_(2)and xAu/TiO_(2)induced the formation of oxygen vacancies,with 0.5 Au content showing the highest oxygen vacancy concentration.At the same Au content,xAu@TiO_(2)generated more oxygen vacancies than xAu/TiO_(2).The oxygen vacancy acted as an effective electron cold trap,which enhanced the photogenerated carrier separation efficiency and thereby improved the catalytic activity.In-situ DRIFTs revealed that the isolated OH(non-hydrogen bond adsorption)were key species for the methane selective oxidation,playing a role in the activation of CH_(4)to^(*)CH_(3).However,an overabundance of isolated OH led to severe overoxidation.Fortunately,the core-shell structure over xAu@TiO_(2)provided a slow-release environment for isolated OH through the intermediate state of^(*)OH(hydrogen bond adsorption)to balance the formation rate and consumption rate of isolated OH,doubling the methanol yield and increasing the>29%selectivity.These results showed a new strategy for the control of the overoxidation rate via a strategy of MOF encapsulation followed by pyrolytic derivation for methane selective oxidation.
基金supported by the National Natural Science Foundation of China(No.22278202).
文摘For the effective treatment of the wastewater with low-medium concentration ammonia nitrogen and low strength COD,a high-performance Co_(3)O_(4) catalyst supported on carbon nanocages(CNCs)was prepared.By isovolumetric im pregnation,Co_(3)O_(4) could be uniformly dispersed on surface of CNCs,which possess tiny particle size and strong electron transfer capability.The catalytic performance of the prepared Co_(3)O_(4)/CNCs catalysts with different Co_(3)O_(4) loadings was systematically evaluated and compared with Co_(3)O_(4)/CNTs.It is found that 20 wt.%Co_(3)O_(4)/CNCs shows the best catalytic performance,achieving an ammonia nitrogen conversion rate of 71.0%and a nitrogen selectivity of 81.8%.Compared to commonly used Co_(3)O_(4),ammonia conversion and nitrogen selectivity of Co_(3)O_(4)/CNCs increased by 28.9%and 15.8%respectively.In the five consecutive cycles,the catalytic activity remained stable.The mechanism that CNCs support effectively increases the surface oxygen vacancies of Co_(3)O_(4) through XPS analysis was also elucidated,and DFT calculations confirm strong electron transfer between CNCs and Co_(3)O_(4),rendering Co_(3)O_(4) nanoparticles as the primary catalytic active sites.The results may contribute to the development of highperformance catalytic ozone oxidation catalysts for ammonia nitrogen.
文摘The methylene-selective oxidation of simple alkanes catalyzed by a nonheme iron(Ⅲ)-monoamidate complex using H_(2)O_(2)as the terminal oxidant is reported.Mechanistic studies suggest that iron(V)-oxo species is the active intermediate,undergoing hydrogen atom abstraction(HAA)as the rate-determining step to initiate C-H bond activation.
基金National Natural Science Foundation of China(52071274)Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.
文摘Photoelectrocatalytic(PEC)seawater splitting as a green and sustainable route to harvest hydrogen is attractive yet hampered by low activity of photoanodes and unexpected high selectivity to the corrosive and toxic chlorine.Especially,it is full of challenges to unveil the key factors influencing the selectivity of such complex PEC processes.Herein,by regulating the energy band and surface structure of the anatase TiO_(2) nanotube array photoanode via nitrogen-doping,the seawater PEC oxidation shifts from Cl^(-)oxidation reaction(ClOR)dominant on the TiO_(2) photoanode(61.6%)to oxygen evolution reaction(OER)dominant on the N-TiO_(2) photoanode(62.9%).Comprehensive investigations including operando photoelectrochemical FTIR and DFT calculations unveil that the asymmetric hydrogen-bonding water at the N-TiO_(2) electrode/electrolyte interface enriches under illumination,facilitating proton transfer and moderate adsorption strength of oxygen-intermediates,which lowers the energy barrier for the OER yet elevates the energy barrier for the ClOR,resulting to a promoted selectivity towards the OER.The work sheds light on the underlying mechanism of the PEC water oxidation processes,and highlights the crucial role of interfacial water on the PEC selectivity,which could be regulated by controlling the energy band and the surface structure of semiconductors.
基金National Natural Science Foundation of China,Grant/Award Numbers:22179093,22379111Department of Education of Guangdong Province for Higher Educational Institution,Grant/Award Number:2022ZDZX4104Shenzhen General Project for Institutions of Higher Education,Grant/Award Number:20231127113219001。
文摘Electrochemical nitrogen looping represents a promising carbon-free and sustainable solution for the energy transition,in which electrochemical ammonia oxidation stays at the central position.However,the various nitrogen-containing intermediates tend to poison and corrode the electrocatalysts,even the state-of-the-art noble-metal ones,which is worsened at a high applied potential.Herein,we present an ultrarapid laser quenching strategy for constructing a corrosion-resistant and nanostructured CuNi alloy metallic glass electrocatalyst.In this material,single-atom Cu species are firmly bonded with the surrounding Ni atoms,endowing exceptional resistance against ammonia corrosion relative of conventional CuNi alloys.Remarkably,a record-high durability for over 300 h is achieved.Ultrarapid quenching also allows a much higher Cu content than typical single-atom alloys,simultaneously yielding a high rate and selectivity for ammonia oxidation reaction(AOR).Consequently,an outstanding ammonia conversion rate of up to 95%is achieved with 91.8%selectivity toward nitrite after 8 h.Theoretical simulations reveal that the structural amorphization of CuNi alloy could effectively modify the electronic configuration and reaction pathway,generating stable singleatom Cu active sites with low kinetic barriers for AOR.This ultrarapid laser quenching strategy thus provides a new avenue for constructing metallic glasses with well-defined nanostructures,presenting feasible opportunities for performance enhancement for AOR and other electrocatalytic processes.
基金Project supported by the National Natural Science Foundation of China(22072096,22108184)。
文摘In this work,a series of Ce-Ti composite oxides with different Ti/Ce molar ratios was prepared by coprecipitation method,and investigated for the catalytic degradation of toluene and selective catalytic reduction of NO.The phase transition process between Ce species and Ti species is limited by modulating the interaction between Ce4+and Ti4+,while a completely amorphous composite is generated with an appropriate molar ratio of Ti/Ce(1.5/1).The catalyst CeTi1.5Oxexhibits the best catalytic performance,where the values of T90and T50for deep degradation of toluene are 297 and 330℃respectively at high weight hours space velocity(WHSV=120000 mL/(g·h)).Compared with CeO_(2),T90and T50decrease by48 and 34℃respectively while declining by 67 and 70℃compared to TiO_(2).For the SCR reaction,CeTi1.5Oxreaches 100%NO conversion at 250℃with WHSV=60000 mL/(g·h),reduced by 50℃compared to pure CeO_(2).The amorphous nanostructure with highly dispersed Ce and Ti species was confirmed by transmission electron microscopy(TEM)and X-ray diffraction(XRD)characterizations.The X-ray photoelectron spectroscopy(XPS)and Raman analyses show that a large number of active Ce-O-Ti species and surface oxygen vacancies are generated due to the strong interaction between Ti^(4+)and Ce^(4+)in CeTi_(1.5)O_(x).Additionally,H_(2)-TPR and O_(2)-TPD further confirm that the interaction promotes the low-temperature reducibility and mobility of surface-active oxygen species.Meanwhile,in-situ DRIFTS study reveals that CeTi1.5Oxwith amorphous nanostructure can dramatically enhance the dissociative and complete oxidation capacity for toluene.
基金financially supported by the Major Fundamental Research of Natural Science Foundation of Shandong Province(ZR2022ZD10)National Natural Science Foundation of China(22478211,22372017)+2 种基金Postdoctoral Fellowship Program of CPSF(GZC20231193)Liaoning Binhai Laboratory(LBLG-2024-10)Qingdao Postdoctoral Applied Research Project(QDBSH20240102068)。
文摘Electrocatalysis,a form of heterogeneous catalysis,is closely associated with both catalyst properties and the catalyst/electrolyte interfacial microenvironment.Herein,we rationally design and synthesize a unique PdCu nano-sea urchins(PdCu NSUs)featured with high-curvature nanotips,by which the interfacial microenvironment is expected to be tailored to the electrocatalytic reactions.PdCu NSUs exhibit excellent activity for ethanol electrooxidation,with a specific activity of 4.11 mA cm^(-2)and a mass activity of 2.24 mAμg_(Pd)^(-1),and a high Faraday efficiency(FE)of 96.4%toward acetic acid.COMSOL finite element simulations confirm that the unique nanotips could induce a local electric field due to the accumulation of positive charges in the nanotips,resulting in enrichment of OH^(-)at the catalyst surface to promote the formation of Pd-OH_(ads),a species required by ethanol dehydrogenation.Furthermore,DFT calculations and in-situ electrochemical Fourier transform infrared spectroscopy discover that the d-band center of Pd significantly downshifts in PdCu alloy,which facilitates the desorption of the produced acetic acid.This work provides a new electrocata lytic material with high-curvature nanotips,and also clarifies how the material morphology,by inducing local electric fields,affects the interfacial microenvironment and thus the catalytic activity and selectivity.
基金Supported by the National Natural Science Foundation of China(12261018)Universities Key Laboratory of Mathematical Modeling and Data Mining in Guizhou Province(2023013)。
文摘In this paper,we establish and study a single-species logistic model with impulsive age-selective harvesting.First,we prove the ultimate boundedness of the solutions of the system.Then,we obtain conditions for the asymptotic stability of the trivial solution and the positive periodic solution.Finally,numerical simulations are presented to validate our results.Our results show that age-selective harvesting is more conducive to sustainable population survival than non-age-selective harvesting.
文摘Gold nanoparticles(AuNPs)supported on the Cu-doped LaMnO_(3)perovskites exhibit strong Au-Mn-Cu synergy in the aerobic oxidation of gaseous ethanol to acetaldehyde(AC).The Au/LaMnCuO_(3)catalysts achieve AC yields exceeding 90%and a space-time yield of 715 g_(AC)g_(AU)^(-1)h^(-1)at 225℃,outperforming reported catalysts.The outstanding performance is attributed to adjacent Cu^(+)and Mn^(2+)ions in the perovskite surface,which,together with nearby AuNPs,contribute to the high activity and stability.The best-performing catalyst contains a Cu/Mn ratio of 1/3 in the perovskite.Doping too much Cu into the perovskite leads to metallic Cu,suppressing catalyst performance.Density functional theory(reaction energetics,electronic structure analysis)and microkinetics simulations aided in understanding the synergy between Cu and Mn and the role of AuNPs.The reaction involves two H abstraction steps:(1)O-H cleavage of adsorbed ethanol by the basic perovskite lattice oxygen atom and(2)α-C-H cleavage by AuNPs,yielding AC and adsorbed water.Molecular O_(2)adsorbs in the oxygen vacancy(O_(V))formed by water removal,generating a peroxide anion(O_(2)^(2-))as the activated oxygen species.In the second part of the catalytic cycle,the basic O_(2)^(2-)species abstracts the H atom from another ethanol molecule,followed byα-C-H cleavage by AuNPs,AC production,and water removal.Water formation in the second part of the catalytic cycle is the rate-controlling step for Au/LaMnO_(3)and Au/LaMnCuO_(3)models.Moderate Cu doping enhances the essential Cu^(+)-OV-Mn^(2+)sites and lowers the barrier for water formation due to the weaker Cu-O bond than the Mn-O bond.In contrast,excessive Cu doping creates unstable Cu^(2+)-O-Cu^(2+)sites and shifts the barrier to theα-C-H cleavage.
文摘Ethylene glycol(EG)is a biomass derivative of polyethylene terephthalate(PET),and its electrocatalytic conversion into high-value chemicals has sparked widespread interest.This study reviews the most recent research development in electrocatalysis-based EG to glycolic acid(GA)conversion.Firstly,the strategies and research results of modulating the electronic structure of catalysts for efficient selective GA production from EG are reviewed.Second,by reviewing the data of in-situ Fourier transform infrared spectroscopy and in-situ electrochemically attenuated total reflection surface enhanced infrared absorption spectroscopy,the reaction pathway and catalytic mechanism of EG partial oxidation to GA were clarified.Finally,the design and regulation of catalysts for selective oxidation of EG by electrocatalysis in the future are prospected.
基金National Natural Science Foundation of China(51504138,51674118,52271177)Hunan Provincial Natural Science Foundation of China(2023JJ50181)Supported by State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology(P2024-022)。
文摘To explore the formation mechanism of anisotropy in Ti-6Al-4V alloy fabricated by selective laser melting(SLM),the compressive mechanical properties,microhardness,microstructure,and crystallographic orientation of the alloy across different planes were investigated.The anisotropy of SLM-fabricated Ti-6Al-4V alloys was analyzed,and the electron backscatter diffraction technique was used to investigate the influence of different grain types and orientations on the stress-strain distribution at various scales.Results reveal that in room-temperature compression tests at a strain rate of 10^(-3) s^(-1),both the compressive yield strength and microhardness vary along the deposition direction,indicating a certain degree of mechanical property anisotropy.The alloy exhibits a columnar microstructure;along the deposition direction,the grains appear equiaxed,and they have internal hexagonal close-packed(hcp)α/α'martensitic structure.α'phase has a preferential orientation approximately along the<0001>direction.Anisotropy arises from the high aspect ratio of columnar grains,along with the weak texture of the microstructure and low symmetry of the hcp crystal structure.
