Recent studies have reported a variety of Mn bipyridine complexes as efficient electrochemical catalysts for the CO_(2)reduction reaction(CO_(2)RR).However,the catalytic reduction mechanism remains ambiguous,particula...Recent studies have reported a variety of Mn bipyridine complexes as efficient electrochemical catalysts for the CO_(2)reduction reaction(CO_(2)RR).However,the catalytic reduction mechanism remains ambiguous,particularly regarding the influence of terminal bipyridine substituents and the role of weak acids on catalytic performance.In this work,density functional theory(DFT)calculations and microkinetic modeling(MKM)are carried out to gain intuitive thermodynamics and kinetics insights into catalytic CO_(2)RR behaviors of[(bpy)Mn(CO)_(3)]^(+)(abbreviated as[bpy Mn])and[(mesbpy)Mn(CO)_(3)]+(abbreviated as[mesbpy Mn]),focusing on product selectivity control.The 2e-reduction of Mn(I)to active Mn(0)-mesbpy(-1)in a spin-polarized singlet state is associated with ligand-to-metal electron transfer induced by axial ligand departure(LMET-ALD),which is attributed to the low reduction potential of[mesbpy Mn].The complete cycles of producing CO,formic acid(FA),and H_(2) show that the rate-determining steps are the second protonation and hydride formation,respectively.Structural similarity of transition states of hydride formation from various acids demonstrates that there is a correlation between the energy barrier for FA production and p K a of acids.The terminal substituent[mes]serves a dual function:(1)elevating the singly occupied molecular orbital(SOMO)energy level through increasing the contribution of the emptyπ(mebpy),which favors electron transfer for hydride formation;and(2)acting as an“energy bridge”to mediate the degeneration of d xy(Mn)with fully occupiedπ(mesbpy)orbitals,facilitating the second protonation step.These findings provide a comprehensive understanding of Mn-bipyridinecatalyzed CO_(2)RR,offering valuable insights for the design of improved molecular catalysts for CO_(2)RR.展开更多
Accurate modeling of catalytic reactions on undercoordinated sites requires accounting for the structural and ensemble-specific nature of the active sites.This study examines how common microkinetic modeling(MKM)assum...Accurate modeling of catalytic reactions on undercoordinated sites requires accounting for the structural and ensemble-specific nature of the active sites.This study examines how common microkinetic modeling(MKM)assumptions affect predicted kinetics and mechanisms on the stepped Pt(211)facet for the ethane dehydrogenation(EDH)and the ethane hydrogenolysis(EH).Six(211)MKMs were developed,differing in(i)the number of active sites represented,(ii)adsorbate site occupancy treatment,and(iii)inclusion of cross-facet interactions.These models are benchmarked against a particle-based microkinetic model(PB-MKM),which best represents step-edge behavior.MKM assumptions caused deviations in turnover frequencies exceeding ten orders of magnitude and led to contrasting mechanistic and selectivity predictions.Multi-site MKMs overestimate activity by inflating free site availability,single-site models underestimate activity,and uniform occupancy models overpredict coverage of multi-dentate intermediates,leading to reaction-specific artifacts.Overall,the Combined Site Edge Model(CSEM),a single-siteMKMaccounting for site occupancy and cross-facet interactions,most closely approximates PB-MKM predictions.All models predict similar kinetics when surfaces are clean or primarily occupied by monodentate species.This work provides practical guidance for selecting MKM frameworks for undercoordinated catalytic surfaces and highlights the critical role of modeling assumptions in catalytic predictions.展开更多
基金supported by the National Natural Science Foundation of China(U23A20140)the Hebei Natural Science Foundation(B2024208068)+2 种基金the Huang Jin Tai Plan Project of Hebei Provincial Department of Education(HJZD202512)supported by the Spanish Ministry of Science(PID2023-149905NB-I00)the Generalitat de Catalunya(2021SGR 00110)。
文摘Recent studies have reported a variety of Mn bipyridine complexes as efficient electrochemical catalysts for the CO_(2)reduction reaction(CO_(2)RR).However,the catalytic reduction mechanism remains ambiguous,particularly regarding the influence of terminal bipyridine substituents and the role of weak acids on catalytic performance.In this work,density functional theory(DFT)calculations and microkinetic modeling(MKM)are carried out to gain intuitive thermodynamics and kinetics insights into catalytic CO_(2)RR behaviors of[(bpy)Mn(CO)_(3)]^(+)(abbreviated as[bpy Mn])and[(mesbpy)Mn(CO)_(3)]+(abbreviated as[mesbpy Mn]),focusing on product selectivity control.The 2e-reduction of Mn(I)to active Mn(0)-mesbpy(-1)in a spin-polarized singlet state is associated with ligand-to-metal electron transfer induced by axial ligand departure(LMET-ALD),which is attributed to the low reduction potential of[mesbpy Mn].The complete cycles of producing CO,formic acid(FA),and H_(2) show that the rate-determining steps are the second protonation and hydride formation,respectively.Structural similarity of transition states of hydride formation from various acids demonstrates that there is a correlation between the energy barrier for FA production and p K a of acids.The terminal substituent[mes]serves a dual function:(1)elevating the singly occupied molecular orbital(SOMO)energy level through increasing the contribution of the emptyπ(mebpy),which favors electron transfer for hydride formation;and(2)acting as an“energy bridge”to mediate the degeneration of d xy(Mn)with fully occupiedπ(mesbpy)orbitals,facilitating the second protonation step.These findings provide a comprehensive understanding of Mn-bipyridinecatalyzed CO_(2)RR,offering valuable insights for the design of improved molecular catalysts for CO_(2)RR.
基金supported by the Institute for Cooperative Upcycling of Plastics (iCOUP), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract DE-AC-02-07CH11358 (Ames National Laboratory)B.R. and W.Y. acknowledge support from the U.S. Department of Energy, Office of Basic Energy Science, Catalysis Science program, under award DE-SC0023376In addition, A.H. acknowledges partial support by the South Carolina Smart State Center for Strategic Approaches to the Generation of Electricity (SAGE). Computing resources are provided by the U.S. Department of Energy facility located at the National Energy Research Scientific Computing Center (NERSC) under projects m4562 and m4885 (2025), and ACCESS facilities located at the San Diego Supercomputer Center (SDSC) and the Rosen Center for Advanced Computing (RCAC) of Purdue University (grant no. TG-CTS090100). Finally, computing resources provided by the University of South Carolina’s High-Performance Computing (HPC) group are gratefully acknowledged.
文摘Accurate modeling of catalytic reactions on undercoordinated sites requires accounting for the structural and ensemble-specific nature of the active sites.This study examines how common microkinetic modeling(MKM)assumptions affect predicted kinetics and mechanisms on the stepped Pt(211)facet for the ethane dehydrogenation(EDH)and the ethane hydrogenolysis(EH).Six(211)MKMs were developed,differing in(i)the number of active sites represented,(ii)adsorbate site occupancy treatment,and(iii)inclusion of cross-facet interactions.These models are benchmarked against a particle-based microkinetic model(PB-MKM),which best represents step-edge behavior.MKM assumptions caused deviations in turnover frequencies exceeding ten orders of magnitude and led to contrasting mechanistic and selectivity predictions.Multi-site MKMs overestimate activity by inflating free site availability,single-site models underestimate activity,and uniform occupancy models overpredict coverage of multi-dentate intermediates,leading to reaction-specific artifacts.Overall,the Combined Site Edge Model(CSEM),a single-siteMKMaccounting for site occupancy and cross-facet interactions,most closely approximates PB-MKM predictions.All models predict similar kinetics when surfaces are clean or primarily occupied by monodentate species.This work provides practical guidance for selecting MKM frameworks for undercoordinated catalytic surfaces and highlights the critical role of modeling assumptions in catalytic predictions.
