TiO_(2) nanobelts and Co_(3)O_(4)/TiO_(2) catalytic materials were prepared using the hydrothermal method.The cat-alyst was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microsc...TiO_(2) nanobelts and Co_(3)O_(4)/TiO_(2) catalytic materials were prepared using the hydrothermal method.The cat-alyst was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray electron spectroscopy,and fluorescence spectroscopy.At room temperature,with a relative humidity of 50.0%,the total gas flow rate of 1.0 L·min-1,the space velocity of 1.05×10^(4) h^(-1),and toluene volume concentration of 25.0µL·L^(-1),two 6 W vacuum ultraviolet lamps were used as light sources to catalyze,degrade,and mineralize toluene.The results show that the prepared catalyst is in the shape of nano-ribbons.The loading of Co_(3)O_(4) inhibits the recombina-tion of photogenerated electrons and holes and can effectively improve the catalytic performance.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%Co_(3)O_(4) has the best catalytic effect.When N2 was used as a carrier gas,the degradation rate of tol-uene was only 34.7%.The toluene degradation is mainly due to the photolysis of vacuum ultraviolet light.When air was used as a carrier gas,O_(3) was produced.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%and vacuum ultraviolet synergistical-ly promote toluene degradation.The highest degradation rate of toluene was 91.7%and the mineralization rate was 74.6%.The degradation rate of toluene was 2.6 times that of nitrogen as a carrier gas.展开更多
Regulating the intermediates involved in the electrocatalytic nitrate reduction reaction(NO_(3)RR)is crucial for the enhancement of reaction efficiency.However,it remains a great challenge to regulate the reaction int...Regulating the intermediates involved in the electrocatalytic nitrate reduction reaction(NO_(3)RR)is crucial for the enhancement of reaction efficiency.However,it remains a great challenge to regulate the reaction intermediates through active site manipulation on the surface of the catalyst.Here,a family of n%-Co_(3)O_(4)/SiC(n=5,8,12,20)catalysts with a delicate percentage of Co^(2+)and Co^(3+)were prepared for NO_(3)RR.We found that Co^(3+)primarily acts as the active site for NO_(3)^(−)reduction to NO_(2)^(−),while Co^(2+)is responsible for the conversion of NO_(2)^(−)to NH_(3).Moreover,the conversion of these intermediates over the active sites is autonomous and separately controllable.Both processes synergistically accomplish the reduction of nitrate ions to synthesize ammonia.Combining the experimental studies and density functional theory(DFT)calculations,it is discovered the pathway(^(*)NHO→^(*)NHOH→^(*)NH_(2)OH→^(*)NH_(2)→^(*)NH_(3))is more favorable due to the lowerΔG value(0.25 eV)for the rate-limiting step(^(*)NO→^(*)NHO).The NH_(3)yield rate of 8%-Co_(3)O_(4)/SiC reached 1.08 mmol/(cm^(2)h)with a Faradaic efficiency of 96.4%at−0.89 V versus the reversible hydrogen electrode(RHE),surpassing those of most reported non-noble NO_(3)RR catalysts.This strategy not only provides an efficient catalyst for NO_(3)RR but also serves as an illustrative model for the regulation of multi-step reaction intermediates through the design of distinct active sites,thereby presenting a new approach to enhance the efficiency of intricate reactions.展开更多
The electrochemical coupling of biomass oxidation and nitrogen conversion presents a potential strategy for high value-added chemicals and nitrogen cycling.Herein,in this work,CuO/Co_(3)O_(4)with heterogeneous interfa...The electrochemical coupling of biomass oxidation and nitrogen conversion presents a potential strategy for high value-added chemicals and nitrogen cycling.Herein,in this work,CuO/Co_(3)O_(4)with heterogeneous interface is successfully constructed as a bifunctional catalyst for the electrooxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and the electroreduction of nitrate to ammonia(NH_(3)).The open-circuit potential spontaneous experiment shows that more 5-hydroxymethylfurfural molecules are adsorbed in the Helmholtz layer of the CuO/Co_(3)O_(4)composite,which certifies that the CuO/Co_(3)O_(4)heterostructure is conducive to the kinetic adsorption of 5-hydroxymethylfurfural.In situ electrochemical impedance spectroscopy further shows that CuO/Co_(3)O_(4)has faster reaction kinetics and lower reaction potential in oxygen evolution reaction and 5-hydroxymethylfurfural electrocatalytic oxidation.Moreover,CuO/Co_(3)O_(4)also has a good reduction effect on NO_(3)^(-).The ex-situ Raman spectroscopy shows that under the reduction potential,the metal oxide is reduced,and the generated Cu_(2)O can be used as a new active site for the reaction to promote the electrocatalytic conversion of NO_(3)^(-)to NH_(3) synthesis.This work provides valuable guidance for the synthesis of value-added chemicals by 5-hydroxymethylfurfural electrocatalytic oxidation coupled with NO_(3)^(-)while efficiently producing NH_(3).展开更多
Flower-like copper foam Co_(3)O_(4) catalysts(Co_(3)O_(4)/CF) were prepared by hydrothermal method.The crystalline structure and microscopic morphology of the prepared samples were characterized by using X-ray diffrac...Flower-like copper foam Co_(3)O_(4) catalysts(Co_(3)O_(4)/CF) were prepared by hydrothermal method.The crystalline structure and microscopic morphology of the prepared samples were characterized by using X-ray diffractometer(XRD) and scanning electron microscope(SEM),and the electrochemical properties were investigated by an electrochemical workstation.The experimental results show that the Co_(3)O_(4) catalysts are successfully prepared on the foamed copper support by hydrothermal method,and the material’s morphology is mainly flower cluster.When the current density is 10 mA·cm^(-2),the overpotential value of the Co_(3)O_(4)/CF catalyst is 141 mV,lower than that of blank support.The electrochemical impedance(EIS) spectrum shows that the R_(ct )value of the Co_(3)O_(4)/CF catalyst decreases,and the Coulomb curves of double-layer show that the electrochemically active area of the Co_(3)O_(4)/CF catalyst efficiently increases compared with that of the blank support.Therefore,the as-obtained Co_(3)O_(4)/CF catalyst exhibits a good hydrogen evolution rate,showing great applicability potential in the catalytic electrolysis of water for hydrogen production.展开更多
氮化硅是一种良好的载体,具有较高的水热稳定性和机械稳定性,其表面的氨基基团能够较好地锚定金属,显著提高金属分散度。但是,商品氮化硅比表面积较低,对金属分散作用仍然有限。因此,以自制的高比表面积氮化硅(Si_(3)N_(4))为载体,通过...氮化硅是一种良好的载体,具有较高的水热稳定性和机械稳定性,其表面的氨基基团能够较好地锚定金属,显著提高金属分散度。但是,商品氮化硅比表面积较低,对金属分散作用仍然有限。因此,以自制的高比表面积氮化硅(Si_(3)N_(4))为载体,通过浸渍法制备了不同Ru负载量(质量分数分别为0.5%、1.0%和2.0%)的催化剂(分别为0.5%Ru/Si_(3)N_(4)、1.0%Ru/Si_(3)N_(4)和2.0%Ru/Si_(3)N_(4)),并以商品氮化硅(Si_(3)N_(4)-C)为载体制备了2.0%Ru/Si_(3)N_(4)-C催化剂作为对照组。表征了催化剂的理化性质,测试了其在300℃、0.1 MPa下的CO_(2)加氢反应活性。结果显示,与Si_(3)N_(4)-C相比,Si_(3)N_(4)的比表面积较高(502 m^(2)/g),Si_(3)N_(4)作为载体显著提高了金属分散度,降低了金属粒径,催化剂暴露出更多的活性位点。0.5%Ru/Si_(3)N_(4)的金属粒径较小,展现出强的H_(2)吸附能力,H难以解吸,抑制了中间物种CO加氢生成CH_(4)。随着Ru负载量增加,金属粒径增大,催化剂的CH_(4)选择性更好。Ru/Si_(3)N_(4)系列催化剂中,2.0%Ru/Si_(3)N_(4)的CH_(4)选择性较高(98.8%)。空速为10000 m L/(g·h)时,0.5%Ru/Si_(3)N_(4)的CO选择性为88.2%。与2.0%Ru/Si_(3)N_(4)相比,2.0%Ru/Si_(3)N_(4)-C的金属粒径更大,活性位点较少,活性更低。2.0%Ru/Si_(3)N_(4)和2.0%Ru/Si_(3)N_(4)-C的CO_(2)转化率分别为53.1%和9.2%。Si_(3)N_(4)有效提高了金属分散度,提高了催化剂的CO_(2)加氢反应活性;通过调控Ru负载量控制催化剂金属粒径,可实现对产物CO或CH_(4)选择性的调控。展开更多
文摘TiO_(2) nanobelts and Co_(3)O_(4)/TiO_(2) catalytic materials were prepared using the hydrothermal method.The cat-alyst was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray electron spectroscopy,and fluorescence spectroscopy.At room temperature,with a relative humidity of 50.0%,the total gas flow rate of 1.0 L·min-1,the space velocity of 1.05×10^(4) h^(-1),and toluene volume concentration of 25.0µL·L^(-1),two 6 W vacuum ultraviolet lamps were used as light sources to catalyze,degrade,and mineralize toluene.The results show that the prepared catalyst is in the shape of nano-ribbons.The loading of Co_(3)O_(4) inhibits the recombina-tion of photogenerated electrons and holes and can effectively improve the catalytic performance.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%Co_(3)O_(4) has the best catalytic effect.When N2 was used as a carrier gas,the degradation rate of tol-uene was only 34.7%.The toluene degradation is mainly due to the photolysis of vacuum ultraviolet light.When air was used as a carrier gas,O_(3) was produced.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%and vacuum ultraviolet synergistical-ly promote toluene degradation.The highest degradation rate of toluene was 91.7%and the mineralization rate was 74.6%.The degradation rate of toluene was 2.6 times that of nitrogen as a carrier gas.
基金financially supported by the National Key Research and Development Program of China (2018YFA0209404)the Fundamental Research Funds for the Central Universities (DUT22LAB601)
文摘Regulating the intermediates involved in the electrocatalytic nitrate reduction reaction(NO_(3)RR)is crucial for the enhancement of reaction efficiency.However,it remains a great challenge to regulate the reaction intermediates through active site manipulation on the surface of the catalyst.Here,a family of n%-Co_(3)O_(4)/SiC(n=5,8,12,20)catalysts with a delicate percentage of Co^(2+)and Co^(3+)were prepared for NO_(3)RR.We found that Co^(3+)primarily acts as the active site for NO_(3)^(−)reduction to NO_(2)^(−),while Co^(2+)is responsible for the conversion of NO_(2)^(−)to NH_(3).Moreover,the conversion of these intermediates over the active sites is autonomous and separately controllable.Both processes synergistically accomplish the reduction of nitrate ions to synthesize ammonia.Combining the experimental studies and density functional theory(DFT)calculations,it is discovered the pathway(^(*)NHO→^(*)NHOH→^(*)NH_(2)OH→^(*)NH_(2)→^(*)NH_(3))is more favorable due to the lowerΔG value(0.25 eV)for the rate-limiting step(^(*)NO→^(*)NHO).The NH_(3)yield rate of 8%-Co_(3)O_(4)/SiC reached 1.08 mmol/(cm^(2)h)with a Faradaic efficiency of 96.4%at−0.89 V versus the reversible hydrogen electrode(RHE),surpassing those of most reported non-noble NO_(3)RR catalysts.This strategy not only provides an efficient catalyst for NO_(3)RR but also serves as an illustrative model for the regulation of multi-step reaction intermediates through the design of distinct active sites,thereby presenting a new approach to enhance the efficiency of intricate reactions.
基金the support received from the National Natural Science Foundation of China(Grant No.22372012,22261160640,and 22002009)the Natural Science Foundation of Hunan Province(Grant No.2023JJ20037 and 2021JJ40565)the Scientific Research Project of Hunan Provincial Department of Education(Grant No.22B0293)
文摘The electrochemical coupling of biomass oxidation and nitrogen conversion presents a potential strategy for high value-added chemicals and nitrogen cycling.Herein,in this work,CuO/Co_(3)O_(4)with heterogeneous interface is successfully constructed as a bifunctional catalyst for the electrooxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid and the electroreduction of nitrate to ammonia(NH_(3)).The open-circuit potential spontaneous experiment shows that more 5-hydroxymethylfurfural molecules are adsorbed in the Helmholtz layer of the CuO/Co_(3)O_(4)composite,which certifies that the CuO/Co_(3)O_(4)heterostructure is conducive to the kinetic adsorption of 5-hydroxymethylfurfural.In situ electrochemical impedance spectroscopy further shows that CuO/Co_(3)O_(4)has faster reaction kinetics and lower reaction potential in oxygen evolution reaction and 5-hydroxymethylfurfural electrocatalytic oxidation.Moreover,CuO/Co_(3)O_(4)also has a good reduction effect on NO_(3)^(-).The ex-situ Raman spectroscopy shows that under the reduction potential,the metal oxide is reduced,and the generated Cu_(2)O can be used as a new active site for the reaction to promote the electrocatalytic conversion of NO_(3)^(-)to NH_(3) synthesis.This work provides valuable guidance for the synthesis of value-added chemicals by 5-hydroxymethylfurfural electrocatalytic oxidation coupled with NO_(3)^(-)while efficiently producing NH_(3).
基金Funded by the National Natural Science Foundation of China(No.51474170)the Foundation of Shaanxi Educational Committee(No.17JK0395)the Xi’an Science and Technology Committee Program(No.GXYD9.2)。
文摘Flower-like copper foam Co_(3)O_(4) catalysts(Co_(3)O_(4)/CF) were prepared by hydrothermal method.The crystalline structure and microscopic morphology of the prepared samples were characterized by using X-ray diffractometer(XRD) and scanning electron microscope(SEM),and the electrochemical properties were investigated by an electrochemical workstation.The experimental results show that the Co_(3)O_(4) catalysts are successfully prepared on the foamed copper support by hydrothermal method,and the material’s morphology is mainly flower cluster.When the current density is 10 mA·cm^(-2),the overpotential value of the Co_(3)O_(4)/CF catalyst is 141 mV,lower than that of blank support.The electrochemical impedance(EIS) spectrum shows that the R_(ct )value of the Co_(3)O_(4)/CF catalyst decreases,and the Coulomb curves of double-layer show that the electrochemically active area of the Co_(3)O_(4)/CF catalyst efficiently increases compared with that of the blank support.Therefore,the as-obtained Co_(3)O_(4)/CF catalyst exhibits a good hydrogen evolution rate,showing great applicability potential in the catalytic electrolysis of water for hydrogen production.
文摘氮化硅是一种良好的载体,具有较高的水热稳定性和机械稳定性,其表面的氨基基团能够较好地锚定金属,显著提高金属分散度。但是,商品氮化硅比表面积较低,对金属分散作用仍然有限。因此,以自制的高比表面积氮化硅(Si_(3)N_(4))为载体,通过浸渍法制备了不同Ru负载量(质量分数分别为0.5%、1.0%和2.0%)的催化剂(分别为0.5%Ru/Si_(3)N_(4)、1.0%Ru/Si_(3)N_(4)和2.0%Ru/Si_(3)N_(4)),并以商品氮化硅(Si_(3)N_(4)-C)为载体制备了2.0%Ru/Si_(3)N_(4)-C催化剂作为对照组。表征了催化剂的理化性质,测试了其在300℃、0.1 MPa下的CO_(2)加氢反应活性。结果显示,与Si_(3)N_(4)-C相比,Si_(3)N_(4)的比表面积较高(502 m^(2)/g),Si_(3)N_(4)作为载体显著提高了金属分散度,降低了金属粒径,催化剂暴露出更多的活性位点。0.5%Ru/Si_(3)N_(4)的金属粒径较小,展现出强的H_(2)吸附能力,H难以解吸,抑制了中间物种CO加氢生成CH_(4)。随着Ru负载量增加,金属粒径增大,催化剂的CH_(4)选择性更好。Ru/Si_(3)N_(4)系列催化剂中,2.0%Ru/Si_(3)N_(4)的CH_(4)选择性较高(98.8%)。空速为10000 m L/(g·h)时,0.5%Ru/Si_(3)N_(4)的CO选择性为88.2%。与2.0%Ru/Si_(3)N_(4)相比,2.0%Ru/Si_(3)N_(4)-C的金属粒径更大,活性位点较少,活性更低。2.0%Ru/Si_(3)N_(4)和2.0%Ru/Si_(3)N_(4)-C的CO_(2)转化率分别为53.1%和9.2%。Si_(3)N_(4)有效提高了金属分散度,提高了催化剂的CO_(2)加氢反应活性;通过调控Ru负载量控制催化剂金属粒径,可实现对产物CO或CH_(4)选择性的调控。
