In situ FTIR spectroscopy was utilized to investigate the magnetic field effect on the heterogeneous photocatalytic degradation of benzene over platinized titania (Pt/TiO2). The results revealed that the employment ...In situ FTIR spectroscopy was utilized to investigate the magnetic field effect on the heterogeneous photocatalytic degradation of benzene over platinized titania (Pt/TiO2). The results revealed that the employment of magnetic field may not change the mechanism of photocatalytic degradation of benzene, however, it greatly facilitate the conversion of benzene to phenol and quinone, as well as the transformation from phenol to quinone, resulting in opening the benzene ring easily and promoting the production of CO2.展开更多
Infrared reflection-absorption spectra for primary, secondary and tertiary orthophosphate anions on a gold electrode in aqueous solution were studied by in situ FTIR spectroscopy. The spectra show that H2PO4- , HPO io...Infrared reflection-absorption spectra for primary, secondary and tertiary orthophosphate anions on a gold electrode in aqueous solution were studied by in situ FTIR spectroscopy. The spectra show that H2PO4- , HPO ions do not interact with the electrode surface as strong as PO do. According to the surface selection rule, we deduce the modes of adsorption of these anions on the electrode from these spectra. The experiment also confirms the affection to adsorption of ion on the electrode due to ion-migration into thin-layer cavity.展开更多
Chromium hexacyanoferrate (CrHCF) modified grassy carbon electrode (GC) in different electrolytes was studied by cyclic voltammetry and in situ FTIR spectroelectrochemistry. The results indicate that the behavior of C...Chromium hexacyanoferrate (CrHCF) modified grassy carbon electrode (GC) in different electrolytes was studied by cyclic voltammetry and in situ FTIR spectroelectrochemistry. The results indicate that the behavior of CrHCF firm can be understood in term of two structures: Cr1/3Cr(III)Fe(II)(CN), and MCr(III)Fe(II)(CN)(6). Besides,the film exists in amorphous state: the outer layer is porous film, while the inner layer is relatively compact. According to the electrochemical reaction of CrHCF, the lattice can contract and expand with the cations' diffusion.展开更多
Corn rod-like WO<sub>3</sub> nanomaterials were successfully synthesized by a simple hydrothermal method. The morphology, structure and optical absorption properties of the prepared samples were characteri...Corn rod-like WO<sub>3</sub> nanomaterials were successfully synthesized by a simple hydrothermal method. The morphology, structure and optical absorption properties of the prepared samples were characterized by SEM, XRD, FTIR and UV-Vis-DRS. The WO<sub>3</sub> materials were corn rod-like morphology with about 800 nm for length and 150 nm for diameter, especially there were plenty of corn particles (about 20 nm) on the surface of corn rods. The X-ray diffraction peaks of the products corresponded with WO<sub>3</sub> standard card, and the characteristic peak of W-O bond was found in the infrared spectrum. The absorption band edge of the products was about 480 nm, indicating their potential visible-light-induced photocatalytic activity. In situ FTIR technology research showed that the prepared WO<sub>3</sub> nanomaterials had visible photocatalytic activity to gas-phase toluene. After a photocatalytic reaction for 8 hours toluene was effectively degraded, and carboxylic acid and aldehyde could be regarded as the intermediate products, and CO<sub>2</sub> was produced as the final product during the reaction process.展开更多
By means of in situ diffuse reflectance FTIR, the IR spectra of 6 coals with different ranks were obtained from room temperature to 230 ℃. A new curve fitting method was used to recognize the different hydrogen ...By means of in situ diffuse reflectance FTIR, the IR spectra of 6 coals with different ranks were obtained from room temperature to 230 ℃. A new curve fitting method was used to recognize the different hydrogen bonds in the coals, and the influence of coal ranks on the distribution of hydrogen bonds(HBs) in the coals and their thermal stability were discussed. The results show that there is another new HB(around 2514 cm -1 ) between the -SH in mercaptans or thiophenols and the nitrogen in the pyridine like compounds in the coals, and the evidence for that was provided. The controversial band of the HB between hydroxyl and the nitrogen of the pyridine like compounds was determined in the range of 3028-2984 cm -1 , and the result is consistent with but more specific than that of Painter et al .. It was found that the stability of different HBs in the coals is influenced by both coal rank and temperature. For some HBs, the higher the coal rank, the higher the stability of them. Within the temperature range of our research, the stability of the HB between the hydroxyl and the π bond increases to some extent for some coals at temperatures higher than 110 or 140 ℃.展开更多
Direct formic acid fuel cell(DFAFC) is an important research project in clean energy field.However,commercialization of DFAFC is still largely limited by the available catalysts with unsatisfied activity,durability an...Direct formic acid fuel cell(DFAFC) is an important research project in clean energy field.However,commercialization of DFAFC is still largely limited by the available catalysts with unsatisfied activity,durability and cost for formic acid electrooxidation(FAEO).Using Pt-and Pd-based nanoclusters as electrocatalysts is a particularly promising strategy to solve the above problem,but two attendant problems need to be solved firstly.(Ⅰ) The controllable synthesis of practicable and stable sub-2 nm clusters remains challenging.(Ⅱ) The catalyzing mechanism of sub-2 nm metal clusters for FAEO has not yet completely understood.Herein,different from traditional solution synthesis,by designing a novel supporting material containing electron-rich and electron-deficient functional groups,size-and dispersioncontrollable synthesis of ~1 nm PtPd nanoclusters is realized by an electrochemical process.The electrocatalytic properties and reaction mechanism of the PtPd nanoclusters for the FAEO were studied by different electrochemical techniques,in-situ fourier transform infrared(FTIR) spectra and density functional theory(DFT) calculations.The tiny PtPd nanoclusters have much higher catalytic activity and durability than commercial Pt/C,Pd/C and 3.5 nm PtPd nanoparticles.The present study shows that the metalreactant interaction plays a decisive role in determining the catalytic activity and cluster-support interaction plays a decisive role in enhancing the durability of electrocatalyst.The ratio and arrangement of Pt and Pd atoms on the surface of 1 nm PtPd cluster as well as the overall valence state,d-band center and specific surface area make them exhibit different catalytic performance and reaction mechanism from nanoparticle catalysts.In addition,in situ FTIR and DFT calculations showed that on the surface of PtPd clusters,the generation of CO_(2)through trans-COOH intermediate is the most optimal reaction pathway for the FAEO.展开更多
The application of direct ethanol fuel cell(DEFC)has been bottlenecked by the sluggish ethanol oxidation reaction(EOR).Efficient electrocatalysts for the C-C bond cleavage are essential to promote EOR with high effici...The application of direct ethanol fuel cell(DEFC)has been bottlenecked by the sluggish ethanol oxidation reaction(EOR).Efficient electrocatalysts for the C-C bond cleavage are essential to promote EOR with high efficiency and C1 selectivity.Here,we prepared Rh-Cu alloy nano-dendrites(RhCu NDs)with abundant surface steps through controlled co-reduction,which exhibited significantly enhanced activity and C1 selectivity(0.47 m A cm_((ECSA))^(-2),472.4 mA mg_(Rh)^(-1),and 38.9%)than Rh NDs(0.32 mA cm((ECSA))-2,322.1 mA mgRh-1,and 21.4%)and commercially available Rh/C(0.18 mA cm_((ECSA))^(-2),265.4 mA mg_(Rh)^(-1),and 14.9%).Theoretical calculations and CO-stripping experiments revealed that alloying with Cu could modulate the surface electronic structures of Rh to resist CO-poisoning while strengthening ethanol adsorption.In situ Fourier transform infrared spectroscopy(FTIR)indicated that the surface steps on RhCu NDs further promoted the C-C bond cleavage to increase the C1 selectivity.Therefore,optimizing the surface geometric and electronic structures of nanocrystals by rational composition and morphology control can provide a promising strategy for developing practical DEFC devices.展开更多
Heterogeneous photosynthesis is a promising route for sustainable ammonia production,which can utilize renewable energy and water as the hydrogen source under ambient condition.In this study,a series of Bi_(5)O_(7)I(B...Heterogeneous photosynthesis is a promising route for sustainable ammonia production,which can utilize renewable energy and water as the hydrogen source under ambient condition.In this study,a series of Bi_(5)O_(7)I(BOI)nanosheets and nanotubes are synthesized,the surface tensile strain is formed by curling the nanosheets into nanotubes to tune the concentration and location of dynamic vacancies.Scanning transmission electron microscopy(STEM)with spherical aberration correction confirms the presence of intrinsic areal defects on the surface of the BOI nanotube resulted from surface tensile strain.The presence of areal defects lowers the formation energy of I vacancies(IV)at step edge site,thus the IV with higher concentration would be favorably generated under visible light.Rapid scan in situ Fourier transform infrared(FT-IR)analysis in the aqueous media reveals that the IV promotes photocatalytic N_(2) activation and reduction,proceeds through an associative alternating mechanism.Specially,after turning off the light,the surface vacancy sites can be reoccupied by I−ions,which enables the protection and regeneration of photocatalyst surface in an aerobic and dark environment.This work provides an innovative strategy to tune concentration and location of dynamic surface vacancies on photocatalysts by building surface tensile strain for advancing sustainable ammonia production.展开更多
Surface oxygen vacancy defects and metal deposition on semiconductor photocatalysts play a critical role in photocatalytic reactions.In this work,oxygen-deficient Bi_(2)WO_(6)microspheres have been prepared by a facil...Surface oxygen vacancy defects and metal deposition on semiconductor photocatalysts play a critical role in photocatalytic reactions.In this work,oxygen-deficient Bi_(2)WO_(6)microspheres have been prepared by a facile ethylene glycol-assisted solvothermal method.Bi0 nanoparticles were reduced by in situ thermaltreatment on Bi_(2)WO_(6)microspheres to obtain Bi^(0)@Bi_(2)WO_(6)-x as well as maintaining the oxygen vacancies(OVs)under N_(2)atmosphere.Afterwards,photocatalytic NO oxidation removal activities of these photocatalysts were investigated under visible light irradiation and Bi^(0)@Bi_(2)WO_(6)-x shows the best NO removal activity than other samples.The photogenerated cha rge separation and trans fe r are promoted by Bi0 nanoparticles deposited on the surface of semiconductor catalysts.OVs defects promote the activation of reactants(H_(2)O and O_(2)),thereby enhancing the formation of the active substance.Moreover,both OVs defects and Bi0 metal have the characteristics of extending light absorption and enhancing the efficient utilization of solar energy.Besides,the photocatalytic NO oxidation mechanism of Bi^(0)@Bi_(2)WO_(6)-xwas investigated by in situ FTIR spectroscopy for reaction intermediates and final products.This work furnishes insight into the synthesis strategy and the underlying photocatalytic mecha nism of the surfacemodified Bi^(0)@Bi_(2)WO_(6)-x composite for pollutants removal.展开更多
Variable temperature in situ FTIR spectroscopy has been used as the primary tool to investigate the effects of temperature(10 to 50 ℃) on formaldehyde dissociative adsorption and electro oxidation on the Ru(00...Variable temperature in situ FTIR spectroscopy has been used as the primary tool to investigate the effects of temperature(10 to 50 ℃) on formaldehyde dissociative adsorption and electro oxidation on the Ru(0001) electrode in perchloric acid solution, and the results were interpreted in terms of the surface chemistry of the Ru(0001) electrode and compared to those obtained during our previous studies on the adsorption of CO under the same conditions. It was found that formaldehyde did undergo dissociative adsorption, even at -200 mV vs . Ag/AgCl, to form linear(CO L) and 3 fold hollow(CO H) binding CO adsorbates. In contrast to the adsorption of CO, it was found that increasing the temperature to 50 ℃ markedly increased the amount of CO adsorbates formed on the Ru(0001) surface from the adsorption of formaldehyde. On increasing the potential, the electro oxidation of the CO adsorbates to CO 2 took place via reaction with the active (1×1) O oxide. A significant increase in the surface reactivity was observed on the RuO 2(100) phase formed at higher potentials. Formic acid was detected as a partial oxidation product during formaldehyde electro oxidation. The data obtained at 50 ℃ are markedly different from those collected at 10 and 25 ℃ in terms of the amount of both CO 2 and formic acid formed and the adsorbed CO L and CO H species observed. These results were rationalized by the thermal effects on both the loosening of the CO adlayer and the activation of surface oxide on increasing the temperature.展开更多
In situ infrared spectra of dimethyl ether adsorbed on two H-ZSM-5 zeolites are reported which are different in both lattice and extraframework aluminium contents. A number of dissociatively adsorbed dimethyl ether sp...In situ infrared spectra of dimethyl ether adsorbed on two H-ZSM-5 zeolites are reported which are different in both lattice and extraframework aluminium contents. A number of dissociatively adsorbed dimethyl ether species associated respectively with the Bronsted acid sites, the external silanol groups and extraframework aluminium species at different temperatures are identified. In particular, dimethyl ether reacts with non acidic hydroxyl species associated with extraframework aluminium to form the third methoxy species. The distributions of hydrocarbons desorbed from a single pulse of dimethyl ether (1.0 mL) onto these zeolite samples are presented. Propene is the major product, and the yield of hydrocarbons correlates with the concentration of Bronsted acid bound methoxy groups.展开更多
A series of silver-doped cerium zirconium oxide(Ag-CevZr)samples was synthesized successfully for selective catalytic reduction of nitric oxide(NO)with hydrogen and propene(H2/C3H6-SCR)under excess oxygen condition.Th...A series of silver-doped cerium zirconium oxide(Ag-CevZr)samples was synthesized successfully for selective catalytic reduction of nitric oxide(NO)with hydrogen and propene(H2/C3H6-SCR)under excess oxygen condition.The catalytic activity test proved that Ag-Ce0.4Zr exhibited the best C3H6-SCR activity.Hydrogen(H2)significantly enlianced NO conversion and widened the temperature window.Multi-technology characterizations were conducted to ascertain the properties of fabricated catalysts including X-ray diflraction(XRD),Fourier transform infrared spectrometry(FTIR),scanning electron microscopy(SEM)and H2 temperature programmed reduction(H2-TPR).In situ FTIR results demonstrated that various types of nitrates and chelating nitrite were generated on Ag-CexZr after introduction of NO.Besides,adding H2 could increase the concentration of bidentate nitrate and chelated bidentate nitrate dramatically,especially for Ce0.4Zr catalyst.Transient reaction between pre-adsorbing NO and C3H/C3H6+H2 illuminated that the most active intermediate was chelating nitrite,which was promoted significantly by H2 participation.Furthermore,adding H2 improved the formation of organo-nitro(R-N02),which was the key intennediate in C3H6-SCR.The reaction mechanism over Ag-CexZr catalysts was proposed at 200℃ as follows:nitric oxide(NO)+pr opene(C 3H6)+hy dr ogen(H2)+oxy gen(O2)→chelating nitrite (N O2-)+acry late-type species(CxHyOz)→organo-nitro(R-NO2)→isocyanate(-NCO)+cyanide(—CN)→nitrogen(N2).展开更多
The catalytic performance of Pt-based catalysts depends sensitively on their d-band centers.Nevertheless,there are still huge challenges to evaluate their d-band centers from experimental technologies,and modulate the...The catalytic performance of Pt-based catalysts depends sensitively on their d-band centers.Nevertheless,there are still huge challenges to evaluate their d-band centers from experimental technologies,and modulate them to analyze their selectivity in ethanol oxidation reaction(EOR).Here,Pt1Au1alloy supported on the commercial carbon material(Pt_(1)Au_(1)/C)is employed as a typical example to investigate its d-band center shift of surface Pt,and as electrocatalysts to study its selectivity towards EOR.Significantly,a highly reliable in situ Fourier-transform infrared spectroscopy CO-probe strategy is developed to characterize the d-band center shift of surface Pt.The modified electronic effect and site effect of Pt_(1)Au_(1)/C dictated the adsorption configuration of intermediate species and the OH species coverage,thereby influencing its selectivity.More importantly,we developed a universal cyclic voltammetry peak differentiation fitting method as an electrochemical analysis technique to investigate CO_(2)selectivity,which is potentially extendable to other Pt-based electrocatalysts.展开更多
Anodic electrocatalyst plays the co re role in direct alcohol fuel cells(DAFCs),while traditional Pt-catalysts suffer from limited catalytic activity,high over potential and severe CO poisoning.Herein,by selectively d...Anodic electrocatalyst plays the co re role in direct alcohol fuel cells(DAFCs),while traditional Pt-catalysts suffer from limited catalytic activity,high over potential and severe CO poisoning.Herein,by selectively depositing Rh atoms on the defective-sites of Pt nanowires(NWs),we developed a new Pt@Rh NW electrocatalyst that exhibited enhanced electrocatalytic performance for both methanol oxidation(MOR)and ethanol oxidation(EOR).Both cyclic voltammetry(CV) and in-situ infrared spectroscopy revealed that the presence of Rh atoms suppressed the generation of poisonous intermediates and completely oxidized alcohols molecule into CO2.Atomic resolusion spherical aberration corrected high-angle annular dark field scanning transmission electron microscopy(CS-HAADF-STEM) and energy-dispersive X-ray spectroscopy(EDS) mapping analysis revealed that Rh atoms were primarily deposited on the defective sites of Pt NWs.Meanwhile,the presence of Rh atoms also modified the electronic state of Pt atoms and therefore lowered the onset potential for alcohols oxidation potential.This work gives the first clear clue on the role of the defective sites of Pt nanocatalyst poisoning,and propose that selectively blocking these sites with trace amount of Rh is an effective strategy in designing advantageous electrocatalysts.展开更多
基金This work was supported financially by the National Natural Science Foundation of China(No.20133010)Education Department of Fujian(No.JB04238).
文摘In situ FTIR spectroscopy was utilized to investigate the magnetic field effect on the heterogeneous photocatalytic degradation of benzene over platinized titania (Pt/TiO2). The results revealed that the employment of magnetic field may not change the mechanism of photocatalytic degradation of benzene, however, it greatly facilitate the conversion of benzene to phenol and quinone, as well as the transformation from phenol to quinone, resulting in opening the benzene ring easily and promoting the production of CO2.
文摘Infrared reflection-absorption spectra for primary, secondary and tertiary orthophosphate anions on a gold electrode in aqueous solution were studied by in situ FTIR spectroscopy. The spectra show that H2PO4- , HPO ions do not interact with the electrode surface as strong as PO do. According to the surface selection rule, we deduce the modes of adsorption of these anions on the electrode from these spectra. The experiment also confirms the affection to adsorption of ion on the electrode due to ion-migration into thin-layer cavity.
文摘Chromium hexacyanoferrate (CrHCF) modified grassy carbon electrode (GC) in different electrolytes was studied by cyclic voltammetry and in situ FTIR spectroelectrochemistry. The results indicate that the behavior of CrHCF firm can be understood in term of two structures: Cr1/3Cr(III)Fe(II)(CN), and MCr(III)Fe(II)(CN)(6). Besides,the film exists in amorphous state: the outer layer is porous film, while the inner layer is relatively compact. According to the electrochemical reaction of CrHCF, the lattice can contract and expand with the cations' diffusion.
文摘Corn rod-like WO<sub>3</sub> nanomaterials were successfully synthesized by a simple hydrothermal method. The morphology, structure and optical absorption properties of the prepared samples were characterized by SEM, XRD, FTIR and UV-Vis-DRS. The WO<sub>3</sub> materials were corn rod-like morphology with about 800 nm for length and 150 nm for diameter, especially there were plenty of corn particles (about 20 nm) on the surface of corn rods. The X-ray diffraction peaks of the products corresponded with WO<sub>3</sub> standard card, and the characteristic peak of W-O bond was found in the infrared spectrum. The absorption band edge of the products was about 480 nm, indicating their potential visible-light-induced photocatalytic activity. In situ FTIR technology research showed that the prepared WO<sub>3</sub> nanomaterials had visible photocatalytic activity to gas-phase toluene. After a photocatalytic reaction for 8 hours toluene was effectively degraded, and carboxylic acid and aldehyde could be regarded as the intermediate products, and CO<sub>2</sub> was produced as the final product during the reaction process.
基金Supported by the National Natural Science Foundation of China(No.2 990 6 0 12)
文摘By means of in situ diffuse reflectance FTIR, the IR spectra of 6 coals with different ranks were obtained from room temperature to 230 ℃. A new curve fitting method was used to recognize the different hydrogen bonds in the coals, and the influence of coal ranks on the distribution of hydrogen bonds(HBs) in the coals and their thermal stability were discussed. The results show that there is another new HB(around 2514 cm -1 ) between the -SH in mercaptans or thiophenols and the nitrogen in the pyridine like compounds in the coals, and the evidence for that was provided. The controversial band of the HB between hydroxyl and the nitrogen of the pyridine like compounds was determined in the range of 3028-2984 cm -1 , and the result is consistent with but more specific than that of Painter et al .. It was found that the stability of different HBs in the coals is influenced by both coal rank and temperature. For some HBs, the higher the coal rank, the higher the stability of them. Within the temperature range of our research, the stability of the HB between the hydroxyl and the π bond increases to some extent for some coals at temperatures higher than 110 or 140 ℃.
基金supported by the National Key Research and Development Plan(2020YFB1506001)the Natural Science Foundation of Guangxi Province(2019GXNSFGA245003)+1 种基金the National Natural Science Foundation of China(Nos.22272036,21575134,21773224)the Guangxi Normal University Research Grant(2022TD)。
文摘Direct formic acid fuel cell(DFAFC) is an important research project in clean energy field.However,commercialization of DFAFC is still largely limited by the available catalysts with unsatisfied activity,durability and cost for formic acid electrooxidation(FAEO).Using Pt-and Pd-based nanoclusters as electrocatalysts is a particularly promising strategy to solve the above problem,but two attendant problems need to be solved firstly.(Ⅰ) The controllable synthesis of practicable and stable sub-2 nm clusters remains challenging.(Ⅱ) The catalyzing mechanism of sub-2 nm metal clusters for FAEO has not yet completely understood.Herein,different from traditional solution synthesis,by designing a novel supporting material containing electron-rich and electron-deficient functional groups,size-and dispersioncontrollable synthesis of ~1 nm PtPd nanoclusters is realized by an electrochemical process.The electrocatalytic properties and reaction mechanism of the PtPd nanoclusters for the FAEO were studied by different electrochemical techniques,in-situ fourier transform infrared(FTIR) spectra and density functional theory(DFT) calculations.The tiny PtPd nanoclusters have much higher catalytic activity and durability than commercial Pt/C,Pd/C and 3.5 nm PtPd nanoparticles.The present study shows that the metalreactant interaction plays a decisive role in determining the catalytic activity and cluster-support interaction plays a decisive role in enhancing the durability of electrocatalyst.The ratio and arrangement of Pt and Pd atoms on the surface of 1 nm PtPd cluster as well as the overall valence state,d-band center and specific surface area make them exhibit different catalytic performance and reaction mechanism from nanoparticle catalysts.In addition,in situ FTIR and DFT calculations showed that on the surface of PtPd clusters,the generation of CO_(2)through trans-COOH intermediate is the most optimal reaction pathway for the FAEO.
基金the financial support from the National Natural Science Foundation of China(Nos.21971012,21922502,21971017)the National Key Research and Development Program of China(No.2020YFB1506300)+1 种基金the Beijing Municipal Natural Science Foundation(No.JQ20007)the Beijing Institute of Technology Research Fund Program。
文摘The application of direct ethanol fuel cell(DEFC)has been bottlenecked by the sluggish ethanol oxidation reaction(EOR).Efficient electrocatalysts for the C-C bond cleavage are essential to promote EOR with high efficiency and C1 selectivity.Here,we prepared Rh-Cu alloy nano-dendrites(RhCu NDs)with abundant surface steps through controlled co-reduction,which exhibited significantly enhanced activity and C1 selectivity(0.47 m A cm_((ECSA))^(-2),472.4 mA mg_(Rh)^(-1),and 38.9%)than Rh NDs(0.32 mA cm((ECSA))-2,322.1 mA mgRh-1,and 21.4%)and commercially available Rh/C(0.18 mA cm_((ECSA))^(-2),265.4 mA mg_(Rh)^(-1),and 14.9%).Theoretical calculations and CO-stripping experiments revealed that alloying with Cu could modulate the surface electronic structures of Rh to resist CO-poisoning while strengthening ethanol adsorption.In situ Fourier transform infrared spectroscopy(FTIR)indicated that the surface steps on RhCu NDs further promoted the C-C bond cleavage to increase the C1 selectivity.Therefore,optimizing the surface geometric and electronic structures of nanocrystals by rational composition and morphology control can provide a promising strategy for developing practical DEFC devices.
基金the National key Research and Development project of China(No.2020YFA0710000)the National Natural Science Foundation of China(Nos.22225606,22176029,and 21822601)+1 种基金the Sichuan Natural Science Foundation for Distinguished Scholars(No.2021JDJQ0006)the Fundamental Research Funds for the Central Universities(No.ZYGX2019Z021).
文摘Heterogeneous photosynthesis is a promising route for sustainable ammonia production,which can utilize renewable energy and water as the hydrogen source under ambient condition.In this study,a series of Bi_(5)O_(7)I(BOI)nanosheets and nanotubes are synthesized,the surface tensile strain is formed by curling the nanosheets into nanotubes to tune the concentration and location of dynamic vacancies.Scanning transmission electron microscopy(STEM)with spherical aberration correction confirms the presence of intrinsic areal defects on the surface of the BOI nanotube resulted from surface tensile strain.The presence of areal defects lowers the formation energy of I vacancies(IV)at step edge site,thus the IV with higher concentration would be favorably generated under visible light.Rapid scan in situ Fourier transform infrared(FT-IR)analysis in the aqueous media reveals that the IV promotes photocatalytic N_(2) activation and reduction,proceeds through an associative alternating mechanism.Specially,after turning off the light,the surface vacancy sites can be reoccupied by I−ions,which enables the protection and regeneration of photocatalyst surface in an aerobic and dark environment.This work provides an innovative strategy to tune concentration and location of dynamic surface vacancies on photocatalysts by building surface tensile strain for advancing sustainable ammonia production.
基金supported by the National Natural Science Foundation of China(No.51772183)the key Research and Development Program of Shaanxi Province(No.2018ZDCXL-SF-02-04)the Fundamental Research Funds for the Central Universities(Nos.GK201903023 and GK201801005)。
文摘Surface oxygen vacancy defects and metal deposition on semiconductor photocatalysts play a critical role in photocatalytic reactions.In this work,oxygen-deficient Bi_(2)WO_(6)microspheres have been prepared by a facile ethylene glycol-assisted solvothermal method.Bi0 nanoparticles were reduced by in situ thermaltreatment on Bi_(2)WO_(6)microspheres to obtain Bi^(0)@Bi_(2)WO_(6)-x as well as maintaining the oxygen vacancies(OVs)under N_(2)atmosphere.Afterwards,photocatalytic NO oxidation removal activities of these photocatalysts were investigated under visible light irradiation and Bi^(0)@Bi_(2)WO_(6)-x shows the best NO removal activity than other samples.The photogenerated cha rge separation and trans fe r are promoted by Bi0 nanoparticles deposited on the surface of semiconductor catalysts.OVs defects promote the activation of reactants(H_(2)O and O_(2)),thereby enhancing the formation of the active substance.Moreover,both OVs defects and Bi0 metal have the characteristics of extending light absorption and enhancing the efficient utilization of solar energy.Besides,the photocatalytic NO oxidation mechanism of Bi^(0)@Bi_(2)WO_(6)-xwas investigated by in situ FTIR spectroscopy for reaction intermediates and final products.This work furnishes insight into the synthesis strategy and the underlying photocatalytic mecha nism of the surfacemodified Bi^(0)@Bi_(2)WO_(6)-x composite for pollutants removal.
文摘Variable temperature in situ FTIR spectroscopy has been used as the primary tool to investigate the effects of temperature(10 to 50 ℃) on formaldehyde dissociative adsorption and electro oxidation on the Ru(0001) electrode in perchloric acid solution, and the results were interpreted in terms of the surface chemistry of the Ru(0001) electrode and compared to those obtained during our previous studies on the adsorption of CO under the same conditions. It was found that formaldehyde did undergo dissociative adsorption, even at -200 mV vs . Ag/AgCl, to form linear(CO L) and 3 fold hollow(CO H) binding CO adsorbates. In contrast to the adsorption of CO, it was found that increasing the temperature to 50 ℃ markedly increased the amount of CO adsorbates formed on the Ru(0001) surface from the adsorption of formaldehyde. On increasing the potential, the electro oxidation of the CO adsorbates to CO 2 took place via reaction with the active (1×1) O oxide. A significant increase in the surface reactivity was observed on the RuO 2(100) phase formed at higher potentials. Formic acid was detected as a partial oxidation product during formaldehyde electro oxidation. The data obtained at 50 ℃ are markedly different from those collected at 10 and 25 ℃ in terms of the amount of both CO 2 and formic acid formed and the adsorbed CO L and CO H species observed. These results were rationalized by the thermal effects on both the loosening of the CO adlayer and the activation of surface oxide on increasing the temperature.
文摘In situ infrared spectra of dimethyl ether adsorbed on two H-ZSM-5 zeolites are reported which are different in both lattice and extraframework aluminium contents. A number of dissociatively adsorbed dimethyl ether species associated respectively with the Bronsted acid sites, the external silanol groups and extraframework aluminium species at different temperatures are identified. In particular, dimethyl ether reacts with non acidic hydroxyl species associated with extraframework aluminium to form the third methoxy species. The distributions of hydrocarbons desorbed from a single pulse of dimethyl ether (1.0 mL) onto these zeolite samples are presented. Propene is the major product, and the yield of hydrocarbons correlates with the concentration of Bronsted acid bound methoxy groups.
基金Supported by the National Natural Science Foundation of China(Nos.21866022,21567018)the Inner Mongolia Natural Science Foundation,China(Nos.2017MS0214,2013MS0203)+1 种基金the Inner Mongolia Graduate Research Innovation Project,China(No.11200-12110201)the Project of the Inner Mongolia Key Laboratory of Environmental Pollution Control and Waste Resource Recycle,China and the Project of the Inner Mongolia Engineering Research Center of Coal Chemical Wastewater Treatment&Resourcelization,China.
文摘A series of silver-doped cerium zirconium oxide(Ag-CevZr)samples was synthesized successfully for selective catalytic reduction of nitric oxide(NO)with hydrogen and propene(H2/C3H6-SCR)under excess oxygen condition.The catalytic activity test proved that Ag-Ce0.4Zr exhibited the best C3H6-SCR activity.Hydrogen(H2)significantly enlianced NO conversion and widened the temperature window.Multi-technology characterizations were conducted to ascertain the properties of fabricated catalysts including X-ray diflraction(XRD),Fourier transform infrared spectrometry(FTIR),scanning electron microscopy(SEM)and H2 temperature programmed reduction(H2-TPR).In situ FTIR results demonstrated that various types of nitrates and chelating nitrite were generated on Ag-CexZr after introduction of NO.Besides,adding H2 could increase the concentration of bidentate nitrate and chelated bidentate nitrate dramatically,especially for Ce0.4Zr catalyst.Transient reaction between pre-adsorbing NO and C3H/C3H6+H2 illuminated that the most active intermediate was chelating nitrite,which was promoted significantly by H2 participation.Furthermore,adding H2 improved the formation of organo-nitro(R-N02),which was the key intennediate in C3H6-SCR.The reaction mechanism over Ag-CexZr catalysts was proposed at 200℃ as follows:nitric oxide(NO)+pr opene(C 3H6)+hy dr ogen(H2)+oxy gen(O2)→chelating nitrite (N O2-)+acry late-type species(CxHyOz)→organo-nitro(R-NO2)→isocyanate(-NCO)+cyanide(—CN)→nitrogen(N2).
基金granted by the National Natural Science Foundation of China(22172134,22288102,22279011)Fundamental Research Funds for the Central Universities(2022CDJXY-003)。
文摘The catalytic performance of Pt-based catalysts depends sensitively on their d-band centers.Nevertheless,there are still huge challenges to evaluate their d-band centers from experimental technologies,and modulate them to analyze their selectivity in ethanol oxidation reaction(EOR).Here,Pt1Au1alloy supported on the commercial carbon material(Pt_(1)Au_(1)/C)is employed as a typical example to investigate its d-band center shift of surface Pt,and as electrocatalysts to study its selectivity towards EOR.Significantly,a highly reliable in situ Fourier-transform infrared spectroscopy CO-probe strategy is developed to characterize the d-band center shift of surface Pt.The modified electronic effect and site effect of Pt_(1)Au_(1)/C dictated the adsorption configuration of intermediate species and the OH species coverage,thereby influencing its selectivity.More importantly,we developed a universal cyclic voltammetry peak differentiation fitting method as an electrochemical analysis technique to investigate CO_(2)selectivity,which is potentially extendable to other Pt-based electrocatalysts.
基金the Natural Science Foundation of Tianjin Municipality (No.18JCYBJC21200)。
文摘Anodic electrocatalyst plays the co re role in direct alcohol fuel cells(DAFCs),while traditional Pt-catalysts suffer from limited catalytic activity,high over potential and severe CO poisoning.Herein,by selectively depositing Rh atoms on the defective-sites of Pt nanowires(NWs),we developed a new Pt@Rh NW electrocatalyst that exhibited enhanced electrocatalytic performance for both methanol oxidation(MOR)and ethanol oxidation(EOR).Both cyclic voltammetry(CV) and in-situ infrared spectroscopy revealed that the presence of Rh atoms suppressed the generation of poisonous intermediates and completely oxidized alcohols molecule into CO2.Atomic resolusion spherical aberration corrected high-angle annular dark field scanning transmission electron microscopy(CS-HAADF-STEM) and energy-dispersive X-ray spectroscopy(EDS) mapping analysis revealed that Rh atoms were primarily deposited on the defective sites of Pt NWs.Meanwhile,the presence of Rh atoms also modified the electronic state of Pt atoms and therefore lowered the onset potential for alcohols oxidation potential.This work gives the first clear clue on the role of the defective sites of Pt nanocatalyst poisoning,and propose that selectively blocking these sites with trace amount of Rh is an effective strategy in designing advantageous electrocatalysts.