The quantitative understanding of how atomic-level catalyst structural changes affect the reactivity of the electrochemical CO_(2)reduction reaction is challenging.Due to the complexity of catalytic systems,convention...The quantitative understanding of how atomic-level catalyst structural changes affect the reactivity of the electrochemical CO_(2)reduction reaction is challenging.Due to the complexity of catalytic systems,conventional in situ X-ray spectroscopy plays a limited role in tracing the underlying dynamic structural changes in catalysts active sites.Herein,operando high-energy resolution fluorescence-detected X-ray absorption spectroscopy was used to precisely identify the dynamic structural transformation of well-defined active sites of a representative model copper(Ⅱ)phthalocyanine catalyst which is of guiding significance in studying single-atom catalysis system.Comprehensive X-ray spectroscopy analyses,including surface sensitive△μspectra which isolates the surface changes by subtracting the disturb of bulk base and X-ray absorption near-edge structure spectroscopy simulation,were used to discover that Cu species aggregated with increasing applied potential,which is responsible for the observed evolution of C_(2)H_(4).The approach developed in this work,characterizing the active-site geometry and dynamic structural change,is a novel and powerful technique to elucidate complex catalytic mechanisms and is expected to con tribute to the rational design of highly effective catalysts.展开更多
Cobalt carbide(Co2C)was considered as potential catalysts available for large-scale industrialization of transforming syngas(H2 and CO)to clean fuels.Herein,we successfully synthesized Co-based catalysts with MnO supp...Cobalt carbide(Co2C)was considered as potential catalysts available for large-scale industrialization of transforming syngas(H2 and CO)to clean fuels.Herein,we successfully synthesized Co-based catalysts with MnO supported,to comprehend the effects of Co2C for Fischer–Tropsch synthesis(FTS)under ambient conditions.The huge variety of product selectivity which was contained by different active sites(Co and Co2C)has been found.Furthermore,density functional theory(DFT)shows that Co2C is efficacious of CO adsorption,whereas is weaker for H adsorption than Co.Combining the advantages of Co and Co2C,the catalyst herein can not only obtain more C5+products but also suppress methane selectivity.It can be a commendable guide for the design of industrial application products in FTS.展开更多
Understanding of the oxygen reduction reaction(ORR)mechanism for single atom catalysts is pivotal for the rational design of non-precious metal cathode materials and the commercialization of fuel cells.Herein,a series...Understanding of the oxygen reduction reaction(ORR)mechanism for single atom catalysts is pivotal for the rational design of non-precious metal cathode materials and the commercialization of fuel cells.Herein,a series of non-precious metal electrocatalysts based on nitrogen-doped bimetallic(Fe and Co)carbide were modeled by density functional theory calculations to predict the corresponding reaction pathways.The study elucidated prior oxygen adsorption on the Fe atom in the dual site and the modifier role of Co atoms to tune the electronic structures of Fe.The reaction activity was highly correlated with the bimetallic center and the coordination environment of the adjacent nitrogen.Interestingly,the preadsorption of*OH resulted in the apparent change of metal atoms'electronic states with the d-band center shifting toward the Fermi level,thereby boosting reaction activity.The result should help promote the fundamental understanding of active sites in ORR catalysts and provide an effective approach to the design of highly efficient ORR catalysts on an atomic scale.展开更多
Cobalt carbide has recently been reported to catalyse the FTO con version of syngas with high selectivity for the production of lower olefins (C2-C4). Clarifying the formation process and atomic structure of cobalt ca...Cobalt carbide has recently been reported to catalyse the FTO con version of syngas with high selectivity for the production of lower olefins (C2-C4). Clarifying the formation process and atomic structure of cobalt carbide will help understand the catalytic mechanism of FTO. Herein, hydrogenati on of carb on monoxide was investigated for cobalt carbide synthesized from CoMn catalyst, followed by X-ray diffraction, transmission electron microscopy, temperature programmed reaction and in situ X-ray absorption spectroscopy. By monitoring the evolution of cobalt carbide during syngas conversion, the wavelet transform results give evidenee for the formation of the cobalt carbide and clearly demonstrate that the active site of catalysis was cobalt carbide.展开更多
The relationship between the structural evolution and redox of Li-rich transition-metal layered oxides(LLOs)cathodes remains ambiguous,obstructing the development of high-performance lithium-ion(Li^(+))battery.Herein,...The relationship between the structural evolution and redox of Li-rich transition-metal layered oxides(LLOs)cathodes remains ambiguous,obstructing the development of high-performance lithium-ion(Li^(+))battery.Herein,the coherent effects of local atomic and electronic structure in Li_(2)Ru_(x)Mn_(1-x)O_(3)(LRMO)with a wide voltage window(1.3–4.8 V)is identified by in situ X-ray absorption fine spectroscopy(XAFS)and chemometrics.We not only skillfully separated the redox active structures to track the electrochemical path,but also visualized the coupling mechanism between the evolution of Ru-Ru dimer and the(de)excitation of cations and anions.Furthermore,introducing manganese triggers the“heterogeneity”of coordination environment and electronic structure between Ru and Mn after discharge to 3 V.The change of thermodynamic and kinetic paths affects the relithiation,and further leads to the hysteresis of the anion activation structure relaxation of Li_(2)Ru_(0.4)Mn_(0.6)O_(3)relative to Li_(2)RuO_(3)(LRO).Additionally,it is demonstrated that the high charge cut-off voltage restrains the relaxation of anionic active structure in LRO from a new perspective through comparative experiments.Our work associates the evolution of atomic structure with charge compensation and negative electrochemical reactions such as voltage hysteresis(VH)and capacity attenuation,deepening the understanding electrochemical reaction mechanism of LLOs during the first cycle and providing a theoretical support for the further design and synthesis of high-efficiency cathodes.展开更多
基金supported by the National Natural Science Foundation of China,grant number:U1732267.
文摘The quantitative understanding of how atomic-level catalyst structural changes affect the reactivity of the electrochemical CO_(2)reduction reaction is challenging.Due to the complexity of catalytic systems,conventional in situ X-ray spectroscopy plays a limited role in tracing the underlying dynamic structural changes in catalysts active sites.Herein,operando high-energy resolution fluorescence-detected X-ray absorption spectroscopy was used to precisely identify the dynamic structural transformation of well-defined active sites of a representative model copper(Ⅱ)phthalocyanine catalyst which is of guiding significance in studying single-atom catalysis system.Comprehensive X-ray spectroscopy analyses,including surface sensitive△μspectra which isolates the surface changes by subtracting the disturb of bulk base and X-ray absorption near-edge structure spectroscopy simulation,were used to discover that Cu species aggregated with increasing applied potential,which is responsible for the observed evolution of C_(2)H_(4).The approach developed in this work,characterizing the active-site geometry and dynamic structural change,is a novel and powerful technique to elucidate complex catalytic mechanisms and is expected to con tribute to the rational design of highly effective catalysts.
基金supported from the National Natural Science Foundation of China,Grant/Award Number:U1732267,21503218.
文摘Cobalt carbide(Co2C)was considered as potential catalysts available for large-scale industrialization of transforming syngas(H2 and CO)to clean fuels.Herein,we successfully synthesized Co-based catalysts with MnO supported,to comprehend the effects of Co2C for Fischer–Tropsch synthesis(FTS)under ambient conditions.The huge variety of product selectivity which was contained by different active sites(Co and Co2C)has been found.Furthermore,density functional theory(DFT)shows that Co2C is efficacious of CO adsorption,whereas is weaker for H adsorption than Co.Combining the advantages of Co and Co2C,the catalyst herein can not only obtain more C5+products but also suppress methane selectivity.It can be a commendable guide for the design of industrial application products in FTS.
基金the Joint Fund of the National Natural Science Foundation of China(U1732267).
文摘Understanding of the oxygen reduction reaction(ORR)mechanism for single atom catalysts is pivotal for the rational design of non-precious metal cathode materials and the commercialization of fuel cells.Herein,a series of non-precious metal electrocatalysts based on nitrogen-doped bimetallic(Fe and Co)carbide were modeled by density functional theory calculations to predict the corresponding reaction pathways.The study elucidated prior oxygen adsorption on the Fe atom in the dual site and the modifier role of Co atoms to tune the electronic structures of Fe.The reaction activity was highly correlated with the bimetallic center and the coordination environment of the adjacent nitrogen.Interestingly,the preadsorption of*OH resulted in the apparent change of metal atoms'electronic states with the d-band center shifting toward the Fermi level,thereby boosting reaction activity.The result should help promote the fundamental understanding of active sites in ORR catalysts and provide an effective approach to the design of highly efficient ORR catalysts on an atomic scale.
基金the financial support from Joint Fund U1732267 of the National Natural Science Foundation of Chinathe Strategic Priority Research Program of Chinese Academy of Sciences(XDB17000000)+2 种基金the National Key R&D Program of China(2017YFB0602500)the National Natural Science Foundation of China(Grant no.21503218)DICP DMTO201306(Grant no.DICP DMTO201306)
文摘Cobalt carbide has recently been reported to catalyse the FTO con version of syngas with high selectivity for the production of lower olefins (C2-C4). Clarifying the formation process and atomic structure of cobalt carbide will help understand the catalytic mechanism of FTO. Herein, hydrogenati on of carb on monoxide was investigated for cobalt carbide synthesized from CoMn catalyst, followed by X-ray diffraction, transmission electron microscopy, temperature programmed reaction and in situ X-ray absorption spectroscopy. By monitoring the evolution of cobalt carbide during syngas conversion, the wavelet transform results give evidenee for the formation of the cobalt carbide and clearly demonstrate that the active site of catalysis was cobalt carbide.
基金supported by the National Key Research and Development Program of China(2021YFA1500502)。
文摘The relationship between the structural evolution and redox of Li-rich transition-metal layered oxides(LLOs)cathodes remains ambiguous,obstructing the development of high-performance lithium-ion(Li^(+))battery.Herein,the coherent effects of local atomic and electronic structure in Li_(2)Ru_(x)Mn_(1-x)O_(3)(LRMO)with a wide voltage window(1.3–4.8 V)is identified by in situ X-ray absorption fine spectroscopy(XAFS)and chemometrics.We not only skillfully separated the redox active structures to track the electrochemical path,but also visualized the coupling mechanism between the evolution of Ru-Ru dimer and the(de)excitation of cations and anions.Furthermore,introducing manganese triggers the“heterogeneity”of coordination environment and electronic structure between Ru and Mn after discharge to 3 V.The change of thermodynamic and kinetic paths affects the relithiation,and further leads to the hysteresis of the anion activation structure relaxation of Li_(2)Ru_(0.4)Mn_(0.6)O_(3)relative to Li_(2)RuO_(3)(LRO).Additionally,it is demonstrated that the high charge cut-off voltage restrains the relaxation of anionic active structure in LRO from a new perspective through comparative experiments.Our work associates the evolution of atomic structure with charge compensation and negative electrochemical reactions such as voltage hysteresis(VH)and capacity attenuation,deepening the understanding electrochemical reaction mechanism of LLOs during the first cycle and providing a theoretical support for the further design and synthesis of high-efficiency cathodes.