Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carri...Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.展开更多
In light of the percentage of Earth’s cloud coverage, heterogeneous ice nucleation in clouds is the most important global-scale pathway. More recent parameterizations of ice nucleation processes in the atmosphere are...In light of the percentage of Earth’s cloud coverage, heterogeneous ice nucleation in clouds is the most important global-scale pathway. More recent parameterizations of ice nucleation processes in the atmosphere are based on the concept of ice nucleation active surface site density (<i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;">). It is usually assumed that </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> is independent of time and aerosol size distribution, </span><i><span style="font-family:Verdana;">i.e.</span></i><span style="font-family:Verdana;"> that the surface properties of aerosols of the same species do not vary with size. However, the independence of </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> on aerosol size for every species has been questioned. This study presents the results of ice nucleation processes of ATD laboratory-generated aerosol (particle diameters of 0 - 3 μm). Ice nucleation in the condensation mode was performed in a Dynamic Filter Processing Cham- ber at temperatures of </span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span><span style="font-family:Verdana;">18<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C and </span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span><span><span style="font-family:Verdana;">22<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C, with a saturation ratio with respect to water of 1.02. Results show that </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> increased by lowering the nucleation temperature, and was also dependent on the particle size. The </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> of particles collected on the filters, after a 0.5 μm D</span><sub><span style="font-family:Verdana;">50</span></sub><span style="font-family:Verdana;"> cut-off cyclone, resulted statistically higher with respect to the values obtained from the particles collected on total filters. The results obtained suggest the need for further investigation of </span><i><span style="font-family:Verdana;">n</span></i><sub><span style="font-family:Verdana;">s</span></sub><span style="font-family:Verdana;"> dependence of same composition aerosol particles with a view to support weather and climate predictions.</span></span></span>展开更多
Identifying the active site of oxide-supported metal catalysts and revealing the intrinsic synergistic mechanism between metal and oxide support remain a large challenge.Herein,we report the identification and separat...Identifying the active site of oxide-supported metal catalysts and revealing the intrinsic synergistic mechanism between metal and oxide support remain a large challenge.Herein,we report the identification and separation of the Pt-O-Ti interface and TiO_(2) surface in Pt-TiO_(2)-based catalysts by depositing different thickness of TiO_(2) shell with∼0.4-nm micropores onto the surface of Pt/TiO_(2) catalyst through atomic layer deposition(ALD).In the oxidation of 3,3′,5,5′-tetramethylbenzidine(TMB)by hydrogen peroxide(H_(2)O_(2))process,the TiO_(2) microporous shells can prevent the contact between TMB and embedded Pt clusters,but not delay the diffusion of H_(2)O_(2).The heterolysis of H_(2)O_(2) to ·OH occurs on the Pt-O-Ti interface,and the generated•OH migrates to the TiO_(2) surface to supplement the surface lattice oxygen,which sequentially oxidizes TMB to oxTMB.And the synergistic effect between Pt-O-Ti interface active sties and TiO_(2) surface active sites can significantly improve the catalytic performance.Our study provides a guide for the understanding of the intrinsic synergistic mechanism between the metal and oxide support in the metal-oxide catalysts.展开更多
The surface acidity of synthetic amorphous AI hydroxide was determined by acid/base titration with several complementary methods including solution analyses of the reacted solutions and XRD characterization of the rea...The surface acidity of synthetic amorphous AI hydroxide was determined by acid/base titration with several complementary methods including solution analyses of the reacted solutions and XRD characterization of the reacted solids. The synthetic specimen was characterized to be the amorphous material showing four broad peaks in XRD pattern. XRD analyses of reacted solids after the titration experiments showed that amorphous AI hydroxide rapidly transformed to crystalline bayerite at the alkaline condition （pH〉10）. The solution analyses after and during the titration Ksp=^aAl^3＋/aH^＋^3 ,was 10^10.3. The amount of consumption of added acid or base during the titration experiment was attributed to both the protonation/deprotonation of dissolved AI species and surface hydroxyl group. The surface acidity constants, surface hydroxyl density and specific surface area were estimated by FITEQL 4.0.展开更多
Ammonia(NH3)is not only an important chemical in many fields,but also provides a promising intermediate for energy stor-age[1,2].To produce NH3 from naturally abundant N2,the strong N≡N bond in the inert N2 molecules...Ammonia(NH3)is not only an important chemical in many fields,but also provides a promising intermediate for energy stor-age[1,2].To produce NH3 from naturally abundant N2,the strong N≡N bond in the inert N2 molecules must be broken firstly.展开更多
Carbon dioxide （CO2） capture and geological storage （CCS） is one of promising technologies for greenhouse gas effect mitigation. Many geotechnical challenges remain during carbon dioxide storage field practices, a...Carbon dioxide （CO2） capture and geological storage （CCS） is one of promising technologies for greenhouse gas effect mitigation. Many geotechnical challenges remain during carbon dioxide storage field practices, among which effectively detecting CO2 from deep underground is one of engineering problems. This paper reviews monitoring techniques currently used during CO2 injection and storage. A method developed based on measuring seismic microtremors is of main interest. This method was first successfully used to characterize a site in this paper. To explore its feasibility in C02 storage monitoring, numerical simulations were conducted to investigate detectable changes in elastic wave signatures due to injection and geological storage of CO2. It is found that, although it is effective for shallow earth profile estimation, the surface wave velocity is not sensitive to the CO2 layer physical parameter variations,especially for a thin CO2 geological storage layer in a deep underground reservoir.展开更多
Single Fe atoms with N-coordination(FeN_(x)sites)in Fe-N-C catalysts are widely recognized as the active centers for catalyzing oxygen reduction reaction(ORR),but attaining superior intrinsic activity and more exposur...Single Fe atoms with N-coordination(FeN_(x)sites)in Fe-N-C catalysts are widely recognized as the active centers for catalyzing oxygen reduction reaction(ORR),but attaining superior intrinsic activity and more exposure of the FeN_(x)sites remains challenging.Herein,the surface pore-edge FeN_(x)sites anchored on suitable porous carbon(SPE-FeN_(x)-HPNC)are reported.展开更多
Isomorphic substitution of ferric ion(Fe~(3+))by aluminum ion(Al~(3+))in iron(hydro)oxides is ubiquitous in natural environments.Aluminum substitution inevitably leads to changes in the microstructures,physicochemical...Isomorphic substitution of ferric ion(Fe~(3+))by aluminum ion(Al~(3+))in iron(hydro)oxides is ubiquitous in natural environments.Aluminum substitution inevitably leads to changes in the microstructures,physicochemical properties,and surface reactions of iron(hydro)oxides,which may have great impacts on the sequestration of nutrients and contaminants in soils and aquatic environments.Over the past decades,the structural properties and surface reactivity of Al-substituted iron(hydro)oxides have been intensively studied.Iron(hydro)oxides in various structural forms and with different Al substitution amounts present high application potentials in addressing environmental issues.A timely summary of the structural properties and interfacial reactions of the most common and representative Al-substituted iron(hydro)oxides is of significance.Herein,the effects of Al substitution on the structural properties and surface activities of iron(hydro)oxides were clarified according to the microstructure,crystal facets,surface site type and density,interfacial reaction mechanisms,and modeling parameters of iron(hydro)oxides.This review systematically elucidates how Al substitution affects the structural properties and surface reactions of iron(hydro)oxides,including the well crystallized goethite and hematite and the poorly crystallized ferrihydrite,providing theoretical guidance for further exploration of the mineralogical characteristics and environmental geochemical behaviors of iron(hydro)oxides.展开更多
The development of highly efficient and selective metal-acid bifunctional catalysts with excellent synergy is essential for obtaining target products and reducing carbon loss in biomass upgrades.Here,a strategy of sur...The development of highly efficient and selective metal-acid bifunctional catalysts with excellent synergy is essential for obtaining target products and reducing carbon loss in biomass upgrades.Here,a strategy of surface Brønsted acid local enrichment induced by hydrogen spillover is proposed to optimize the metal-acid synergy.The Ni/10 TiO_(2)/ZSM-22 catalyst,which features Ni nanoparticles and ZSM-22 separated by a sub-nanometric TiO_(2)porous film,was prepared using atomic layer deposition to improve the palmitic acid hydrodeoxygenation performance.The TiO_(2)film facilitates hydrogen spillover,improving the hydrogenation activity of metal sites.Approximately 75%of the original surface Brønsted acid sites(BASs)on ZSM-22 are covered by the porous TiO_(2),and the surface BAS concentration of Ni/10 TiO_(2)/ZSM-22 is increased due to the facilitated hydrogen spillover,i.e.,the surface BASs are enriched locally in the zone of TiO_(2)pores.Thanks to the surface BAS local enrichment,the formation of byproduct pentadecane is inhibited,and the intermediate 1-hexadecanol is rapidly converted,obtaining notable hexadecane selectivity.This strategy is also effective for the Pt/10 TiO_(2)/ZSM-22 catalyst,resulting in nearly 100%hexadecane yield(99.6%).This research provides valuable insights into designing highly efficient bifunctional catalysts for energy conversion.展开更多
The optimization of the electronic structure and increased number of exposed surface sites represent a promising direction for enhancing the activity of Ni-based catalysts for urea oxidation reaction(UOR)-assisted ele...The optimization of the electronic structure and increased number of exposed surface sites represent a promising direction for enhancing the activity of Ni-based catalysts for urea oxidation reaction(UOR)-assisted electrolysis.Herein,we have reported the designed synthesis of 2D porous NiCo alloy thin sheets(NiCo/C)based on NaCl-induced transformation of the EDTA-NiCo complex for the effective UORassisted hydrogen evolution reaction(HER).The porous and thin-sheet structure endows a large specific surface area of 141.59 m^(2) g^(−1),greatly enhancing the exposure of active sites.Electron transfer from Co to Ni can optimize the electronic properties of the Ni sites,decreasing the energy barrier and accelerating the reaction kinetics for the UOR.The catalyst shows a low UOR potential of 1.30 V at a current density of 10 mA cm^(−2),which is much lower than the traditional oxygen evolution reaction(1.51 V).In situ impedance/infrared spectroscopy indicates the fast UOR process and a more environmentally sustainable“carbonate”pathway.The catalyst also shows a low HER overpotential of 30 mV at a current density of 10 mA cm^(−2),being comparable to Pt/C.A urea-assisted H2 production cell based on NiCo/C requires only 1.38 V at a current density of 10 mA cm^(−2),which is superior to the Pt/C||uO_(2) cell(1.45 V).展开更多
CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with expos...CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with exposed{001}planes.Temperature programmed reduction of CO shows that Co_(3)O_(4) nanobelts have stronger reducing properties than Co_(3)O_(4) nanocubes.The essence of shape and crystal plane effect is revealed by the fact that turnover frequency of Co3+sites of{011}planes on Co_(3)O_(4) nanobelts is far higher than that of{001}planes on Co_(3)O_(4) nanocubes.展开更多
Various and critical electrocatalytic processes are involved during the redox reactions in the Li-S batteries,which extremely depend on the surface structure and chemical state.Recently,single-atom concept unlocks a r...Various and critical electrocatalytic processes are involved during the redox reactions in the Li-S batteries,which extremely depend on the surface structure and chemical state.Recently,single-atom concept unlocks a route to maximize the use of surface-active atoms,however,further increasing the density of active site is still strictly limited by the inherent structure that single-atoms are only highly-dispersed on substrate.Herein,we provide a viewpoint that an elaborate facet design with singlecrystalline structure engineering can harvest high-density surface active sites,which can significantly boost the electrocatalyst performance for excellent Li-S batteries.Specifically,the single-crystal CoSe_(2)(scCS)exhibits three-types of terminated(011)facet,efficiently obtaining the surface with a high-rich Co^(3+)–Se bond termination,in contrast with lots of surface grain boundaries and dangling bonds in polycrystalline CoSe_(2).Surprisingly,the surface active sites concentration can reach more than 69%.As anticipated,it can provide high-density and high-efficient active sites,enormously suppressing the shuttle effect and improving the reaction kinetics via accelerating the conversion and deposition of polysulfides and Li2S.This surface lattice strategy with element terminated mode is a promising approach for designing electrocatalyst effect-based energy system,not merely for Li-S batteries.展开更多
Cu/ZSM-5 and CeO_2-modified Cu/ZSM-5 catalysts were prepared by a wetness impregnation method. The addition of CeO_2 was found to enhance the NO_x selective catalytic reduction（SCR） activity of the catalyst at low t...Cu/ZSM-5 and CeO_2-modified Cu/ZSM-5 catalysts were prepared by a wetness impregnation method. The addition of CeO_2 was found to enhance the NO_x selective catalytic reduction（SCR） activity of the catalyst at low temperatures, but the high-temperature activity was weakened. The catalysts were characterized by X-ray diffraction（XRD）, nitrogen physisorption, inductively coupled plasma optical emission spectrometry（ICP-OES）, X-ray photoelectron spectroscopy（XPS）, electron paramagnetic resonance（EPR）, H_2 temperature-programmed reduction（TPR） and NH_3 temperature-programmed desorption（TPD）. The results showed that more CuO clusters instead of isolated Cu^（2＋） species were obtained on the modified catalyst. These active CuO clusters, as well as the Cu-Ce synergistic effect, improved the redox property of the catalyst and low-temperatures SCR activity via promoting the oxidation of NO to NO_2 and fast SCR reaction. The loss in high-temperatures activity was attributed to the enhanced competitive oxidation of NH_3 by O_2 and decreased surface acidity of the catalyst.展开更多
In recently published paper by Yang Chunxin[1], I reexamined the paper. On page 128, the paper 'pointed out that the size and spatial distribution density of nucleation sites presented on real boiling surface can ...In recently published paper by Yang Chunxin[1], I reexamined the paper. On page 128, the paper 'pointed out that the size and spatial distribution density of nucleation sites presented on real boiling surface can be described by the normalized fractal distribution function, and the physical meaning of parameters involved in some experimental correlations proposed by early investigations are identified according to fractal distribution'. However, the definition on fractal dimension given by Yang[1] is highly questionable, and the results obtained by Yang are contradictory to the basic fractal theory. Here are my comments:展开更多
Fe304 was supported on mesoporous A12O3 or SiO2 （50 wt.%） using an incipient wetness impregnation method, and Fe304/A12O3 exhibited higher catalytic efficiency for the degradation of 2,4-dichlorophenoxyace- tic acid...Fe304 was supported on mesoporous A12O3 or SiO2 （50 wt.%） using an incipient wetness impregnation method, and Fe304/A12O3 exhibited higher catalytic efficiency for the degradation of 2,4-dichlorophenoxyace- tic acid andpara-chlorobenzoic acid aqueous solution with ozone. The effect and morphology of supported Fe304 on catalytic ozonation performance were investigated based on the characterization results of X-ray diffraction, X-ray photoelectron spectroscopy, BET analysis and Fourier transform infrared spectroscopy. The results indicated that the physical and chemical properties of the catalyst supports especially their Lewis acid sites had a significant influence on the catalytic activity. In comparison with SiO2, more Lewis acid sites existed on the surface of A12O3, resulting in higher catalytic ozonation activity. During the reaction process, no significant Fe ions release was observed. Moreover, Fe304/A12O3 exhibited stable structure and activity after successive cyclic experiments. The results indicated that the catalyst is a promising ozonation catalyst with magnetic separation in drinking water treatment.展开更多
Surface-abundant active sites,rapid charge transport and associated prolonged electron lifetime are vital factors that determine efficient photocatalysis.A series of different Zn_(0.5)Cd_(0.5)S solid solutions,includi...Surface-abundant active sites,rapid charge transport and associated prolonged electron lifetime are vital factors that determine efficient photocatalysis.A series of different Zn_(0.5)Cd_(0.5)S solid solutions,including single crystalline Zn_(0.5)Cd_(0.5)S(ZCS),single crystalline Zn_(0.5)Cd_(0.5)S with S vacancies(ZCS-V),twin structured-Zn_(0.5)Cd_(0.5)S(T-ZCS)and twin-structure Zn_(0.5)Cd_(0.5)S with S vacancies(T-ZCSv)were successfully prepared in the present work by manipulating the conditions of the hydrothermal reaction.Experimental results confirm that the optimized T-ZCSv photocatalyst that possesses a hexagonal wurtzite/zinc blende(WZ/ZB)twin structure and rich-surface S vacancies exhibits an excellent photocatalytic hydrogen production efficiency of approximately 551.74μmol h^(-1).The outstanding performance of the optimized T-ZCSv is attributed to the prolonged electron lifetime and effectively facilitated separation and migration of charge carriers.These are provided by the periodically aligned WZ/ZB interfacial homojunctions that form the S-scheme staggered energy band structure across the junction and abundant S vacancies that serve as electron trapping sites in the T-ZCSv.Furthermore,T-ZCSv are uniformly dispersed on 2-methylimidazole zinc salt[zeolitic imidazolate framework-8(ZIF-8 polyhedron)],which not only could inhibit the aggregation of T-ZCSv but also expose more active sites for photocatalytic-redox reactions.Finally,a possible charge separation and transfer mechanism explaining the optimum activity of the outperforming sample is proposed on the basis of the results obtained from a range of investigation methods[scanning electron microscopy and energy-dispersive spectroscopy(SEM-EDS),transmission electron microscopy and high-resolution transmission electron microscopy(TEM/HRTEM),X-ray diffraction(XRD)technique,ultraviolet-visible(UV-vis)diffuse reflection spectroscopy,and electron paramagnetic resonance(EPR)spectroscopy].This study demonstrates the development of a structurally unique Zn_(0.5)Cd_(0.5)S(with twin structure and S vacancies)and a Zn_(0.5)Cd_(0.5)S-based metal-organic framework(MOF)for photocatalytic applications.展开更多
Based on monolayer dispersion theory,Co_(3)O_(4)/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia.Co_(3)O_(4)can spontaneously disperse on HZSM...Based on monolayer dispersion theory,Co_(3)O_(4)/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia.Co_(3)O_(4)can spontaneously disperse on HZSM-5 support with a monolayer dispersion threshold of 0.061 mmol 100 m^(-2),equaling to a weight percentage around 4.5%.It has been revealed that the quantities of surface active oxygen(O_(2)^(-))and acid sites are crucial for the reaction,which can adsorb and activate NO_(x)and NH_(3)reactants effectively.Below the monolayer dispersion threshold,Co_(3)O_(4)is finely dispersed as sub-monolayers or monolayers and in an amorphous state,which is favorable to generate the two kinds of active sites,hence promoting the performance of ammonia selective catalytic reduction of nitrogen oxide.However,the formation of crystalline Co_(3)O_(4)above the capacity is harmful to the reaction performance.4%Co_(3)O_(4)/ZSM-5,the catalyst close to the monolayer dispersion capacity,possesses the most abundant active O_(2)^(-)species and acidic sites,thereby demonstrating the best reaction performance in all the samples.It is proposed the optimal Co_(3)O_(4)/ZSM-5 catalyst can be prepared by loading the capacity amount of Co_(3)O_(4)onto HZSM-5 support.展开更多
基金E.L.,K.L.,P.W.,and S.T.are supported by the SCCER-Heat and Energy Storage program
文摘Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.
文摘In light of the percentage of Earth’s cloud coverage, heterogeneous ice nucleation in clouds is the most important global-scale pathway. More recent parameterizations of ice nucleation processes in the atmosphere are based on the concept of ice nucleation active surface site density (<i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;">). It is usually assumed that </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> is independent of time and aerosol size distribution, </span><i><span style="font-family:Verdana;">i.e.</span></i><span style="font-family:Verdana;"> that the surface properties of aerosols of the same species do not vary with size. However, the independence of </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> on aerosol size for every species has been questioned. This study presents the results of ice nucleation processes of ATD laboratory-generated aerosol (particle diameters of 0 - 3 μm). Ice nucleation in the condensation mode was performed in a Dynamic Filter Processing Cham- ber at temperatures of </span><span style="font-family:;" "=""><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span><span style="font-family:Verdana;">18<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C and </span><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span></span><span><span style="font-family:Verdana;">22<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C, with a saturation ratio with respect to water of 1.02. Results show that </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> increased by lowering the nucleation temperature, and was also dependent on the particle size. The </span><i><span style="font-family:Verdana;">n</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> of particles collected on the filters, after a 0.5 μm D</span><sub><span style="font-family:Verdana;">50</span></sub><span style="font-family:Verdana;"> cut-off cyclone, resulted statistically higher with respect to the values obtained from the particles collected on total filters. The results obtained suggest the need for further investigation of </span><i><span style="font-family:Verdana;">n</span></i><sub><span style="font-family:Verdana;">s</span></sub><span style="font-family:Verdana;"> dependence of same composition aerosol particles with a view to support weather and climate predictions.</span></span></span>
基金financially supported from the National Natural Science Foundation of China(21802094,22272127,22002118,and 22172119)the National Science Fund for Distinguished Young Scholars(21825204)+1 种基金the Fundamental Research Funds for the Central Universities(D5000210666)the Natural Science Basic Research Plan in Shaanxi Province of China(2021JM-047).
文摘Identifying the active site of oxide-supported metal catalysts and revealing the intrinsic synergistic mechanism between metal and oxide support remain a large challenge.Herein,we report the identification and separation of the Pt-O-Ti interface and TiO_(2) surface in Pt-TiO_(2)-based catalysts by depositing different thickness of TiO_(2) shell with∼0.4-nm micropores onto the surface of Pt/TiO_(2) catalyst through atomic layer deposition(ALD).In the oxidation of 3,3′,5,5′-tetramethylbenzidine(TMB)by hydrogen peroxide(H_(2)O_(2))process,the TiO_(2) microporous shells can prevent the contact between TMB and embedded Pt clusters,but not delay the diffusion of H_(2)O_(2).The heterolysis of H_(2)O_(2) to ·OH occurs on the Pt-O-Ti interface,and the generated•OH migrates to the TiO_(2) surface to supplement the surface lattice oxygen,which sequentially oxidizes TMB to oxTMB.And the synergistic effect between Pt-O-Ti interface active sties and TiO_(2) surface active sites can significantly improve the catalytic performance.Our study provides a guide for the understanding of the intrinsic synergistic mechanism between the metal and oxide support in the metal-oxide catalysts.
文摘The surface acidity of synthetic amorphous AI hydroxide was determined by acid/base titration with several complementary methods including solution analyses of the reacted solutions and XRD characterization of the reacted solids. The synthetic specimen was characterized to be the amorphous material showing four broad peaks in XRD pattern. XRD analyses of reacted solids after the titration experiments showed that amorphous AI hydroxide rapidly transformed to crystalline bayerite at the alkaline condition （pH〉10）. The solution analyses after and during the titration Ksp=^aAl^3＋/aH^＋^3 ,was 10^10.3. The amount of consumption of added acid or base during the titration experiment was attributed to both the protonation/deprotonation of dissolved AI species and surface hydroxyl group. The surface acidity constants, surface hydroxyl density and specific surface area were estimated by FITEQL 4.0.
基金financial support from the National Natural Science Foundation of China(51702352,21975280)the Key Research Program of Frontier Sciences,CAS(QYZDB-SSWSLH034)+3 种基金the Youth Innovation Promotion Association Chinese Academy of Sciences(20200354)the Guangdong Special Support Program(2017TX04C096),the Leading Talents of Guangdong Province Program(00201520)the Guangdong Basic and Applied Basic Research Fund(2019A1515111062)the City University of Hong Kong Strategic Research Grant(SRG)(Nos.7005105 and 7005264)。
文摘Ammonia(NH3)is not only an important chemical in many fields,but also provides a promising intermediate for energy stor-age[1,2].To produce NH3 from naturally abundant N2,the strong N≡N bond in the inert N2 molecules must be broken firstly.
基金the financial supports from the State Key Laboratory for Geomechanics & Deep Underground Engineering, China University of Mining and Technology (No. SKLGDUEK1002)the Fundamental Research Funds for the Central Government Supported Universities of Tongji University, China (No. 0270219037)
文摘Carbon dioxide （CO2） capture and geological storage （CCS） is one of promising technologies for greenhouse gas effect mitigation. Many geotechnical challenges remain during carbon dioxide storage field practices, among which effectively detecting CO2 from deep underground is one of engineering problems. This paper reviews monitoring techniques currently used during CO2 injection and storage. A method developed based on measuring seismic microtremors is of main interest. This method was first successfully used to characterize a site in this paper. To explore its feasibility in C02 storage monitoring, numerical simulations were conducted to investigate detectable changes in elastic wave signatures due to injection and geological storage of CO2. It is found that, although it is effective for shallow earth profile estimation, the surface wave velocity is not sensitive to the CO2 layer physical parameter variations,especially for a thin CO2 geological storage layer in a deep underground reservoir.
基金supported by the Natural Science Foundation of Heilongjiang Province(No.LH2021B026)the National Natural Science Foundation of China(No.21878061).
文摘Single Fe atoms with N-coordination(FeN_(x)sites)in Fe-N-C catalysts are widely recognized as the active centers for catalyzing oxygen reduction reaction(ORR),but attaining superior intrinsic activity and more exposure of the FeN_(x)sites remains challenging.Herein,the surface pore-edge FeN_(x)sites anchored on suitable porous carbon(SPE-FeN_(x)-HPNC)are reported.
基金financially supported by the National Natural Science Foundation of China(Nos.42207352,42007020,and 42007015)the Natural Science Fund for Excellent Young Scholars of Hainan Province,China(No.324YXQN421)。
文摘Isomorphic substitution of ferric ion(Fe~(3+))by aluminum ion(Al~(3+))in iron(hydro)oxides is ubiquitous in natural environments.Aluminum substitution inevitably leads to changes in the microstructures,physicochemical properties,and surface reactions of iron(hydro)oxides,which may have great impacts on the sequestration of nutrients and contaminants in soils and aquatic environments.Over the past decades,the structural properties and surface reactivity of Al-substituted iron(hydro)oxides have been intensively studied.Iron(hydro)oxides in various structural forms and with different Al substitution amounts present high application potentials in addressing environmental issues.A timely summary of the structural properties and interfacial reactions of the most common and representative Al-substituted iron(hydro)oxides is of significance.Herein,the effects of Al substitution on the structural properties and surface activities of iron(hydro)oxides were clarified according to the microstructure,crystal facets,surface site type and density,interfacial reaction mechanisms,and modeling parameters of iron(hydro)oxides.This review systematically elucidates how Al substitution affects the structural properties and surface reactions of iron(hydro)oxides,including the well crystallized goethite and hematite and the poorly crystallized ferrihydrite,providing theoretical guidance for further exploration of the mineralogical characteristics and environmental geochemical behaviors of iron(hydro)oxides.
基金supported by the National Key R&D Program of China(2020YFA0210902)the National Natural Science Foundation of China(22222207,22402217)。
文摘The development of highly efficient and selective metal-acid bifunctional catalysts with excellent synergy is essential for obtaining target products and reducing carbon loss in biomass upgrades.Here,a strategy of surface Brønsted acid local enrichment induced by hydrogen spillover is proposed to optimize the metal-acid synergy.The Ni/10 TiO_(2)/ZSM-22 catalyst,which features Ni nanoparticles and ZSM-22 separated by a sub-nanometric TiO_(2)porous film,was prepared using atomic layer deposition to improve the palmitic acid hydrodeoxygenation performance.The TiO_(2)film facilitates hydrogen spillover,improving the hydrogenation activity of metal sites.Approximately 75%of the original surface Brønsted acid sites(BASs)on ZSM-22 are covered by the porous TiO_(2),and the surface BAS concentration of Ni/10 TiO_(2)/ZSM-22 is increased due to the facilitated hydrogen spillover,i.e.,the surface BASs are enriched locally in the zone of TiO_(2)pores.Thanks to the surface BAS local enrichment,the formation of byproduct pentadecane is inhibited,and the intermediate 1-hexadecanol is rapidly converted,obtaining notable hexadecane selectivity.This strategy is also effective for the Pt/10 TiO_(2)/ZSM-22 catalyst,resulting in nearly 100%hexadecane yield(99.6%).This research provides valuable insights into designing highly efficient bifunctional catalysts for energy conversion.
基金supported by the National Key R&D Program of China(2022YFA1503003)the National Natural Science Foundation of China(91961111,22271081)+3 种基金the Natural Science Foundation of Heilongjiang Province(ZD2021B003)the Basic Research Fund of Heilongjiang University in Heilongjiang Province(2022-KYYWF-1060)the Postdoctoral Science Foundation of Heilongjiang Province(LBH-Z22240)the Heilongjiang University Excellent Youth Foundation.
文摘The optimization of the electronic structure and increased number of exposed surface sites represent a promising direction for enhancing the activity of Ni-based catalysts for urea oxidation reaction(UOR)-assisted electrolysis.Herein,we have reported the designed synthesis of 2D porous NiCo alloy thin sheets(NiCo/C)based on NaCl-induced transformation of the EDTA-NiCo complex for the effective UORassisted hydrogen evolution reaction(HER).The porous and thin-sheet structure endows a large specific surface area of 141.59 m^(2) g^(−1),greatly enhancing the exposure of active sites.Electron transfer from Co to Ni can optimize the electronic properties of the Ni sites,decreasing the energy barrier and accelerating the reaction kinetics for the UOR.The catalyst shows a low UOR potential of 1.30 V at a current density of 10 mA cm^(−2),which is much lower than the traditional oxygen evolution reaction(1.51 V).In situ impedance/infrared spectroscopy indicates the fast UOR process and a more environmentally sustainable“carbonate”pathway.The catalyst also shows a low HER overpotential of 30 mV at a current density of 10 mA cm^(−2),being comparable to Pt/C.A urea-assisted H2 production cell based on NiCo/C requires only 1.38 V at a current density of 10 mA cm^(−2),which is superior to the Pt/C||uO_(2) cell(1.45 V).
基金This work was supported by National Natural Science Foundation of China(NSFC)(Nos.10979031,20921001,and 90606006)the“973”State Key Project(No.2006CB932303)and the China Postdoctoral Science Foundation(No.20080440361).
文摘CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with exposed{001}planes.Temperature programmed reduction of CO shows that Co_(3)O_(4) nanobelts have stronger reducing properties than Co_(3)O_(4) nanocubes.The essence of shape and crystal plane effect is revealed by the fact that turnover frequency of Co3+sites of{011}planes on Co_(3)O_(4) nanobelts is far higher than that of{001}planes on Co_(3)O_(4) nanocubes.
基金National Natural Science Foundation of China(Nos.52070194,52073309,51902347,51932003,51872115,and 22109135)Science and Technology Development Project of Jilin Province(Nos.YDZJ202101ZYTS165,20210506034ZP,and 20210509051RQ).
文摘Various and critical electrocatalytic processes are involved during the redox reactions in the Li-S batteries,which extremely depend on the surface structure and chemical state.Recently,single-atom concept unlocks a route to maximize the use of surface-active atoms,however,further increasing the density of active site is still strictly limited by the inherent structure that single-atoms are only highly-dispersed on substrate.Herein,we provide a viewpoint that an elaborate facet design with singlecrystalline structure engineering can harvest high-density surface active sites,which can significantly boost the electrocatalyst performance for excellent Li-S batteries.Specifically,the single-crystal CoSe_(2)(scCS)exhibits three-types of terminated(011)facet,efficiently obtaining the surface with a high-rich Co^(3+)–Se bond termination,in contrast with lots of surface grain boundaries and dangling bonds in polycrystalline CoSe_(2).Surprisingly,the surface active sites concentration can reach more than 69%.As anticipated,it can provide high-density and high-efficient active sites,enormously suppressing the shuttle effect and improving the reaction kinetics via accelerating the conversion and deposition of polysulfides and Li2S.This surface lattice strategy with element terminated mode is a promising approach for designing electrocatalyst effect-based energy system,not merely for Li-S batteries.
基金Project supported by the the National Natural Science Foundation of China(51372137)Ministry of Science and Technology,China(2015AA034603)
文摘Cu/ZSM-5 and CeO_2-modified Cu/ZSM-5 catalysts were prepared by a wetness impregnation method. The addition of CeO_2 was found to enhance the NO_x selective catalytic reduction（SCR） activity of the catalyst at low temperatures, but the high-temperature activity was weakened. The catalysts were characterized by X-ray diffraction（XRD）, nitrogen physisorption, inductively coupled plasma optical emission spectrometry（ICP-OES）, X-ray photoelectron spectroscopy（XPS）, electron paramagnetic resonance（EPR）, H_2 temperature-programmed reduction（TPR） and NH_3 temperature-programmed desorption（TPD）. The results showed that more CuO clusters instead of isolated Cu^（2＋） species were obtained on the modified catalyst. These active CuO clusters, as well as the Cu-Ce synergistic effect, improved the redox property of the catalyst and low-temperatures SCR activity via promoting the oxidation of NO to NO_2 and fast SCR reaction. The loss in high-temperatures activity was attributed to the enhanced competitive oxidation of NH_3 by O_2 and decreased surface acidity of the catalyst.
文摘In recently published paper by Yang Chunxin[1], I reexamined the paper. On page 128, the paper 'pointed out that the size and spatial distribution density of nucleation sites presented on real boiling surface can be described by the normalized fractal distribution function, and the physical meaning of parameters involved in some experimental correlations proposed by early investigations are identified according to fractal distribution'. However, the definition on fractal dimension given by Yang[1] is highly questionable, and the results obtained by Yang are contradictory to the basic fractal theory. Here are my comments:
文摘Fe304 was supported on mesoporous A12O3 or SiO2 （50 wt.%） using an incipient wetness impregnation method, and Fe304/A12O3 exhibited higher catalytic efficiency for the degradation of 2,4-dichlorophenoxyace- tic acid andpara-chlorobenzoic acid aqueous solution with ozone. The effect and morphology of supported Fe304 on catalytic ozonation performance were investigated based on the characterization results of X-ray diffraction, X-ray photoelectron spectroscopy, BET analysis and Fourier transform infrared spectroscopy. The results indicated that the physical and chemical properties of the catalyst supports especially their Lewis acid sites had a significant influence on the catalytic activity. In comparison with SiO2, more Lewis acid sites existed on the surface of A12O3, resulting in higher catalytic ozonation activity. During the reaction process, no significant Fe ions release was observed. Moreover, Fe304/A12O3 exhibited stable structure and activity after successive cyclic experiments. The results indicated that the catalyst is a promising ozonation catalyst with magnetic separation in drinking water treatment.
基金supported by the General Research Fund(18300920)of Research Grants CouncilDean’s Research Fund(FLASS/DRF 04738)of the Faculty of Liberal Arts+5 种基金Social Sciences,the Education University of Hong Kong,Hong Kong Special Administrative Region,the National Natural Science Foundation of China(No.51802245)the Natural Science Basic Research Plan in the Shaanxi Province of China(No.2023-JC-ZD-25 and 2023-JC-YB-590)Shaanxi Province(Qin ChuangYuan)“Scientist+Engineer”Team Building(2022KXJ-040)China Postdoctoral Science Foundation Funding(No.2018M631188)Shaanxi Provincial Department of Education Key Scientific Research Project(No.22JY024)Graduate Innovation Foundation of Xi’an Polytechnic University(No.chx2022023).
文摘Surface-abundant active sites,rapid charge transport and associated prolonged electron lifetime are vital factors that determine efficient photocatalysis.A series of different Zn_(0.5)Cd_(0.5)S solid solutions,including single crystalline Zn_(0.5)Cd_(0.5)S(ZCS),single crystalline Zn_(0.5)Cd_(0.5)S with S vacancies(ZCS-V),twin structured-Zn_(0.5)Cd_(0.5)S(T-ZCS)and twin-structure Zn_(0.5)Cd_(0.5)S with S vacancies(T-ZCSv)were successfully prepared in the present work by manipulating the conditions of the hydrothermal reaction.Experimental results confirm that the optimized T-ZCSv photocatalyst that possesses a hexagonal wurtzite/zinc blende(WZ/ZB)twin structure and rich-surface S vacancies exhibits an excellent photocatalytic hydrogen production efficiency of approximately 551.74μmol h^(-1).The outstanding performance of the optimized T-ZCSv is attributed to the prolonged electron lifetime and effectively facilitated separation and migration of charge carriers.These are provided by the periodically aligned WZ/ZB interfacial homojunctions that form the S-scheme staggered energy band structure across the junction and abundant S vacancies that serve as electron trapping sites in the T-ZCSv.Furthermore,T-ZCSv are uniformly dispersed on 2-methylimidazole zinc salt[zeolitic imidazolate framework-8(ZIF-8 polyhedron)],which not only could inhibit the aggregation of T-ZCSv but also expose more active sites for photocatalytic-redox reactions.Finally,a possible charge separation and transfer mechanism explaining the optimum activity of the outperforming sample is proposed on the basis of the results obtained from a range of investigation methods[scanning electron microscopy and energy-dispersive spectroscopy(SEM-EDS),transmission electron microscopy and high-resolution transmission electron microscopy(TEM/HRTEM),X-ray diffraction(XRD)technique,ultraviolet-visible(UV-vis)diffuse reflection spectroscopy,and electron paramagnetic resonance(EPR)spectroscopy].This study demonstrates the development of a structurally unique Zn_(0.5)Cd_(0.5)S(with twin structure and S vacancies)and a Zn_(0.5)Cd_(0.5)S-based metal-organic framework(MOF)for photocatalytic applications.
基金the financial supporting by the National Natural Science Foundation of China(Grant Nos.21962009,22172071,22102069,22062013)the Natural Science Foundation of Jiangxi Province(Grant Nos.20202BAB203006,20181ACB20005)the Key Laboratory Foundation of Jiangxi Province for Environment and Energy Catalysis(Grant No.20181BCD40004).
文摘Based on monolayer dispersion theory,Co_(3)O_(4)/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia.Co_(3)O_(4)can spontaneously disperse on HZSM-5 support with a monolayer dispersion threshold of 0.061 mmol 100 m^(-2),equaling to a weight percentage around 4.5%.It has been revealed that the quantities of surface active oxygen(O_(2)^(-))and acid sites are crucial for the reaction,which can adsorb and activate NO_(x)and NH_(3)reactants effectively.Below the monolayer dispersion threshold,Co_(3)O_(4)is finely dispersed as sub-monolayers or monolayers and in an amorphous state,which is favorable to generate the two kinds of active sites,hence promoting the performance of ammonia selective catalytic reduction of nitrogen oxide.However,the formation of crystalline Co_(3)O_(4)above the capacity is harmful to the reaction performance.4%Co_(3)O_(4)/ZSM-5,the catalyst close to the monolayer dispersion capacity,possesses the most abundant active O_(2)^(-)species and acidic sites,thereby demonstrating the best reaction performance in all the samples.It is proposed the optimal Co_(3)O_(4)/ZSM-5 catalyst can be prepared by loading the capacity amount of Co_(3)O_(4)onto HZSM-5 support.
