A continuous online in situ attenuated total reflection Fourier-transform infrared(ATR-FTIR)spectroscopic technique was used to investigate the adsorption and desorption kinetics of heptyl xanthate(KHX)on the surface ...A continuous online in situ attenuated total reflection Fourier-transform infrared(ATR-FTIR)spectroscopic technique was used to investigate the adsorption and desorption kinetics of heptyl xanthate(KHX)on the surface of ZnO and Cu(Ⅱ)activated ZnO.The results showed that Cu(Ⅱ)facilitated the xanthate adsorption process on the surface,and led to the formation of cuprous xanthate(CuX),dixanthogen(X_(2))and xanthate aggregates.The adsorption of xanthate on the surface of ZnO and Cu(Ⅱ)activated ZnO was found to both follow the pseudo-first-order kinetic model.When the NaOH solution was used as a desorption agent,the adsorbed xanthate can largely be removed due to the competition between OH^(−)and HX−.However,for Cu(Ⅱ)activated ZnO,the peak intensities at 1197 and 1082 cm^(−1) had no obvious weakening,and the absorption intensities at 1261 and 1026 cm^(−1) increased in the first 5 min,indicating an ion-exchange reaction between OH^(−)and surface zinc bonded xanthate HX−and the reorganization of adsorbed xanthate.展开更多
Among all CO2 electroreduction products,methane(CH4)and ethylene(C_(2)H_(4))are two typical and valuable hydrocarbon products which are formed in two different pathways:hydrogenation and dimerization reactions of the ...Among all CO2 electroreduction products,methane(CH4)and ethylene(C_(2)H_(4))are two typical and valuable hydrocarbon products which are formed in two different pathways:hydrogenation and dimerization reactions of the same CO intermediate.Theoretical studies show that the adsorption configurations of CO intermediate determine the reaction pathways towards CH4/C_(2)H_(4).However,it is challenging to experimentally control the CO adsorption configurations at the catalyst surface,and thus the hydrocarbon selectivity is still limited.Herein,we seek to synthesize two well-defined copper nanocatalysts with controllable surface structures.The two model catalysts exhibit a high hydrocarbon selectivity toward either CH4(83%)or C_(2)H_(4)(93%)under identical reduction conditions.Scanning transmission electron microscopy and X-ray absorption spectroscopy characterizations reveal the low-coordination Cu^(0)sites and local Cu^(0)/Cu^(+)sites of the two catalysts,respectively.CO-temperature programed desorption,in-situ attenuated total reflection Fourier transform infrared spectroscopy and density functional theory studies unveil that the bridge-adsorbed CO(CO_(B))on the low-coordination Cu^(0)sites is apt to be hydrogenated to CH4,whereas the bridge-adsorbed CO plus linear-adsorbed CO(CO_(B)+CO_(L))on the local Cu^(0)/Cu^(+)sites are apt to be coupled to C_(2)H_(4).Our findings pave a new way to design catalysts with controllable CO adsorption configurations for high hydrocarbon product selectivity.展开更多
基金supported by the National Natural Science Foundation of China (Nos.51274104,50874052)the National Basic Research Program of China (No.2011CB933700)。
文摘A continuous online in situ attenuated total reflection Fourier-transform infrared(ATR-FTIR)spectroscopic technique was used to investigate the adsorption and desorption kinetics of heptyl xanthate(KHX)on the surface of ZnO and Cu(Ⅱ)activated ZnO.The results showed that Cu(Ⅱ)facilitated the xanthate adsorption process on the surface,and led to the formation of cuprous xanthate(CuX),dixanthogen(X_(2))and xanthate aggregates.The adsorption of xanthate on the surface of ZnO and Cu(Ⅱ)activated ZnO was found to both follow the pseudo-first-order kinetic model.When the NaOH solution was used as a desorption agent,the adsorbed xanthate can largely be removed due to the competition between OH^(−)and HX−.However,for Cu(Ⅱ)activated ZnO,the peak intensities at 1197 and 1082 cm^(−1) had no obvious weakening,and the absorption intensities at 1261 and 1026 cm^(−1) increased in the first 5 min,indicating an ion-exchange reaction between OH^(−)and surface zinc bonded xanthate HX−and the reorganization of adsorbed xanthate.
基金supported by the National Natural Science Foundation of China (21875042)Shanghai Science and Technology Committee (18QA1400800)+1 种基金the Program of Eastern Scholar at Shanghai Institutions and Yanchang Petroleum Groupsupported by the Frontier Research Center for Materials Structure, School of Materials Science and Engineering of Shanghai Jiao Tong University
文摘Among all CO2 electroreduction products,methane(CH4)and ethylene(C_(2)H_(4))are two typical and valuable hydrocarbon products which are formed in two different pathways:hydrogenation and dimerization reactions of the same CO intermediate.Theoretical studies show that the adsorption configurations of CO intermediate determine the reaction pathways towards CH4/C_(2)H_(4).However,it is challenging to experimentally control the CO adsorption configurations at the catalyst surface,and thus the hydrocarbon selectivity is still limited.Herein,we seek to synthesize two well-defined copper nanocatalysts with controllable surface structures.The two model catalysts exhibit a high hydrocarbon selectivity toward either CH4(83%)or C_(2)H_(4)(93%)under identical reduction conditions.Scanning transmission electron microscopy and X-ray absorption spectroscopy characterizations reveal the low-coordination Cu^(0)sites and local Cu^(0)/Cu^(+)sites of the two catalysts,respectively.CO-temperature programed desorption,in-situ attenuated total reflection Fourier transform infrared spectroscopy and density functional theory studies unveil that the bridge-adsorbed CO(CO_(B))on the low-coordination Cu^(0)sites is apt to be hydrogenated to CH4,whereas the bridge-adsorbed CO plus linear-adsorbed CO(CO_(B)+CO_(L))on the local Cu^(0)/Cu^(+)sites are apt to be coupled to C_(2)H_(4).Our findings pave a new way to design catalysts with controllable CO adsorption configurations for high hydrocarbon product selectivity.
