The effects of axial ligand on the oxygen atom transfer(OAT)reaction from 5,10,15-tris(pentafluorophenyl)corrole((tpfc)MnVO)to dimethyl sulfide(DMS)have been investigated by density functional theory(DFT)calculations....The effects of axial ligand on the oxygen atom transfer(OAT)reaction from 5,10,15-tris(pentafluorophenyl)corrole((tpfc)MnVO)to dimethyl sulfide(DMS)have been investigated by density functional theory(DFT)calculations.Imidazole(Im),4-methylimidazole(4-MI)and pyridine(Py)were selected as the axial ligands.The results revealed that the axial ligand can form coordinate bond with(tpfc)MnVO in the transition state(TS)of the OAT reaction.The axial coordination favored charge transferring from(tpfc)MnVO to DMS,and weakened the Mn≡O bond in both singlet and triplet states.Furthermore,axial coordination can reduce the energy barrier of neutral(tpfc)MnVO from 23.62 kJ·mol^-1 to less than 3 kJ·mol^-1 in the triplet state,which is significantly lower than in the singlet state.This makes(tpfc)MnVO tend to direct the OAT reaction via triplet state pathway.On the other hand,the energy barriers of[(tpfc)MnVIO]+species from disproportionation pathway increased from 1.26 to 33.95 kJ·mol^-1 in a doublet state.This suggests axial ligands were conducive for direct(tpfc)MnVO OAT reaction pathway.展开更多
Cost-effective 3d transition metal(TM) based single atom catalysts(SACs) for oxygen reduction reaction(ORR) are potential alternatives for Pt-based electrocatalysts in fuel cells and metal-air batteries.Understanding ...Cost-effective 3d transition metal(TM) based single atom catalysts(SACs) for oxygen reduction reaction(ORR) are potential alternatives for Pt-based electrocatalysts in fuel cells and metal-air batteries.Understanding the effects of SACs’ properties and active site composition on the catalytic performance is significant to construct highly efficient catalysts. Here, we successfully promote the activity of cobalt single atoms decorated on N-doped carbon nanosheets via tuning the content of different nitrogen components, which outperforms most reported cobalt SACs. The activity and kinetics show positive correlation trends with the content of Co-Nxand graphitic N, serving as the main active sites.Furthermore, ORR kinetics in alkaline media can be positively affected by the conductivity of catalysts while no similar relation is observed in acidic media. The slight loss of Co-Nxsites engenders a mild change of performance in alkaline media, while the decrease of Co-Nxsite activity due to chemical oxidation of carbon support and the loss of Co-Nxsites in acidic media exacerbate the degradation of performance. Our work provides an insight into the relation between ORR electron transfer kinetics and active sites in 3d TM based SACs.展开更多
Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperforma...Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperformance ORR electrocatalysts are highly regarded.Despite recent progress on minimizing the ORR halfwave potential as the current evaluation indicator,in-depth quantitative kinetic analysis on overall ORR electrocatalytic performance remains insufficiently emphasized.In this paper,a quantitative kinetic analysis method is proposed to afford decoupled kinetic information from linear sweep voltammetry profiles on the basis of the Koutecky–Levich equation.Independent parameters regarding exchange current density,electron transfer number,and electrochemical active surface area can be respectively determined following the proposed method.This quantitative kinetic analysis method is expected to promote understanding of the electrocatalytic effect and point out further optimization direction for ORR electrocatalysis.展开更多
The development of non‐precious metal catalysts that facilitate the oxygen evolution reaction(OER)is important for the widespread application of hydrogen production by water splitting.Various perovskite oxides have b...The development of non‐precious metal catalysts that facilitate the oxygen evolution reaction(OER)is important for the widespread application of hydrogen production by water splitting.Various perovskite oxides have been employed as active OER catalysts,however,the underlying mechanism that occurs at the catalyst‐electrolyte interface is still not well understood,prohibiting the design and preparation of advanced OER catalysts.Here,we report a systematic investigation into the effect of proton dynamics on the catalyst‐electrolyte interfaces of four perovskite catalysts:La_(0.5)Sr_(0.5)CoO_(3‐δ)(LSCO),LaCoO_(3),LaFeO_(3),and LaNiO_(3).The pH‐dependent OER activities,H/D kinetic isotope effect,and surface functionalization with phosphate anion groups were investigated to elucidate the role of proton dynamics in the rate‐limiting steps of the OER.For oxides with small charge‐transfer energies,such as LSCO and LaNiO_(3),non‐concerted proton‐coupled electron transfer steps are involved in the OER,and the activity is strongly controlled by the proton dynamics on the catalyst surface.The results demonstrate the important role of interfacial proton transfer in the OER mechanism,and suggest that proton dynamics at the interface should carefully be considered in the design of future high‐performance catalysts.展开更多
Pseudo-first order reaction rate constants of 5,10,15-tris（pentafluorophenyl）corrole Mn（V）-oxo （F_（15）CMn（V）-oxo）,5,15-bis（pentafluorophenyl）-10-（phenyl）corrole Mn（V）-oxo（F_（10）CMn（V）-oxo）,5,15- ...Pseudo-first order reaction rate constants of 5,10,15-tris（pentafluorophenyl）corrole Mn（V）-oxo （F_（15）CMn（V）-oxo）,5,15-bis（pentafluorophenyl）-10-（phenyl）corrole Mn（V）-oxo（F_（10）CMn（V）-oxo）,5,15- bis（phenyl）-10-（pentafluorophenyl）corrole Mn（V）-oxo（F_5CMn（V）-oxo） and 5,10,15-tris（phenyl）corrole Mn（V）-oxo（F_0CMn（V）-oxo） with a series of alkene substrates in different solvents were determined by UV-vis spectroscopy.The results indicated that the oxygen atom transfer pathway between Mn（V）-oxo corrole and alkene is solvent-dependent.展开更多
The development of catalytic aerobic epoxidation by numerous metal complexes in the presence of aldehyde as a sacrificial reductant(Mukaiyama epoxidation)has been reported,however,comprehensive examination of oxygen a...The development of catalytic aerobic epoxidation by numerous metal complexes in the presence of aldehyde as a sacrificial reductant(Mukaiyama epoxidation)has been reported,however,comprehensive examination of oxygen atom transfer mechanism involving free radical and highly reactive intermediates has yet to be presented.Herein,meso-tetrakis(pentafluorophenyl)porphyrinatooxidovanadium(Ⅳ)(VOTPFPP)was prepared and proved to be efficient toward aerobic olefin epoxidation in the presence of isobutyraldehyde.In situ electron paramagnetic resonance spectroscopy(in situ EPR)showed the generation,transfer pathways and ascription of free radicals in the epoxidation.According to the spectral and computational studies,the side-on vanadium-peroxo complexes are considered as the active intermediate species in the reaction process.In the cyclohexene epoxidation catalyzed by VOTPFPP,the kinetic isotope effect value of 1.0 was obtained,indicating that epoxidation occurred via oxygen atom transfer mechanism.The mechanism was further elucidated using isotopically labeled dioxygen experiments and density functional theory(DFT)calculations.展开更多
Exploring platinum group metal-free electrocatalysts with superior catalytic performance and favorable durability for oxygen reduction reaction is a remaining bottleneck in process of developing sustainable techniques...Exploring platinum group metal-free electrocatalysts with superior catalytic performance and favorable durability for oxygen reduction reaction is a remaining bottleneck in process of developing sustainable techniques in energy storage and conversion. Herein, a hierarchical porous single atomic Fe electrocatalyst(Fe/Z8-E-C) is rationally designed and synthesized via acid etching, calcination, adsorption of Fe precursor and recalcination processes. This unique electrocatalyst Fe/Z8-E-C shows excellent oxygen reduction performance with a half-wave potential of 0.89 V in 0.1 mol/L KOH, 30 m V superior to that of commercial Pt/C(0.86 V), which is also significantly higher than that of typical Fe-doped ZIF-8 derived carbon nanoparticles(Fe/Z8-C) with a half-wave potential of 0.84 V. Furthermore, Fe/Z8-E-C-based Zn-air battery exhibits greatly enhanced peak power density and specific capacity than those of original Fe/Z8-C,verifying the remarkable performance and practicability of this specially designed hierarchical structure due to its efficient utilization of the active sites and rapid mass transfer. This present work proposes a new method to rationally synthesize single atom electrocatalysts loaded on hierarchical porous frame materials for catalysis and energy conversion.展开更多
基金supported by the National Natural Science Foundation of China(21275057,21671068)Natural Science Foundation of Guangdong Province(S2012010008763,2017A050506048)
文摘The effects of axial ligand on the oxygen atom transfer(OAT)reaction from 5,10,15-tris(pentafluorophenyl)corrole((tpfc)MnVO)to dimethyl sulfide(DMS)have been investigated by density functional theory(DFT)calculations.Imidazole(Im),4-methylimidazole(4-MI)and pyridine(Py)were selected as the axial ligands.The results revealed that the axial ligand can form coordinate bond with(tpfc)MnVO in the transition state(TS)of the OAT reaction.The axial coordination favored charge transferring from(tpfc)MnVO to DMS,and weakened the Mn≡O bond in both singlet and triplet states.Furthermore,axial coordination can reduce the energy barrier of neutral(tpfc)MnVO from 23.62 kJ·mol^-1 to less than 3 kJ·mol^-1 in the triplet state,which is significantly lower than in the singlet state.This makes(tpfc)MnVO tend to direct the OAT reaction via triplet state pathway.On the other hand,the energy barriers of[(tpfc)MnVIO]+species from disproportionation pathway increased from 1.26 to 33.95 kJ·mol^-1 in a doublet state.This suggests axial ligands were conducive for direct(tpfc)MnVO OAT reaction pathway.
基金financial support from the Natural Science Foundation of Beijing Municipality (2191001)the National Natural Science Foundation of China (51631001, 51672010 and 52001007)+1 种基金the National Key R&D Program of China(2017YFA0206301)the China Postdoctoral Science Foundation (2020M670038)。
文摘Cost-effective 3d transition metal(TM) based single atom catalysts(SACs) for oxygen reduction reaction(ORR) are potential alternatives for Pt-based electrocatalysts in fuel cells and metal-air batteries.Understanding the effects of SACs’ properties and active site composition on the catalytic performance is significant to construct highly efficient catalysts. Here, we successfully promote the activity of cobalt single atoms decorated on N-doped carbon nanosheets via tuning the content of different nitrogen components, which outperforms most reported cobalt SACs. The activity and kinetics show positive correlation trends with the content of Co-Nxand graphitic N, serving as the main active sites.Furthermore, ORR kinetics in alkaline media can be positively affected by the conductivity of catalysts while no similar relation is observed in acidic media. The slight loss of Co-Nxsites engenders a mild change of performance in alkaline media, while the decrease of Co-Nxsite activity due to chemical oxidation of carbon support and the loss of Co-Nxsites in acidic media exacerbate the degradation of performance. Our work provides an insight into the relation between ORR electron transfer kinetics and active sites in 3d TM based SACs.
基金supported by Beijing Natural Science Foundation(JQ20004)National Key Research and Development Program(2016YFA0202500)Scientific and Technological Key Project of Shanxi Province(20191102003).
文摘Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperformance ORR electrocatalysts are highly regarded.Despite recent progress on minimizing the ORR halfwave potential as the current evaluation indicator,in-depth quantitative kinetic analysis on overall ORR electrocatalytic performance remains insufficiently emphasized.In this paper,a quantitative kinetic analysis method is proposed to afford decoupled kinetic information from linear sweep voltammetry profiles on the basis of the Koutecky–Levich equation.Independent parameters regarding exchange current density,electron transfer number,and electrochemical active surface area can be respectively determined following the proposed method.This quantitative kinetic analysis method is expected to promote understanding of the electrocatalytic effect and point out further optimization direction for ORR electrocatalysis.
文摘The development of non‐precious metal catalysts that facilitate the oxygen evolution reaction(OER)is important for the widespread application of hydrogen production by water splitting.Various perovskite oxides have been employed as active OER catalysts,however,the underlying mechanism that occurs at the catalyst‐electrolyte interface is still not well understood,prohibiting the design and preparation of advanced OER catalysts.Here,we report a systematic investigation into the effect of proton dynamics on the catalyst‐electrolyte interfaces of four perovskite catalysts:La_(0.5)Sr_(0.5)CoO_(3‐δ)(LSCO),LaCoO_(3),LaFeO_(3),and LaNiO_(3).The pH‐dependent OER activities,H/D kinetic isotope effect,and surface functionalization with phosphate anion groups were investigated to elucidate the role of proton dynamics in the rate‐limiting steps of the OER.For oxides with small charge‐transfer energies,such as LSCO and LaNiO_(3),non‐concerted proton‐coupled electron transfer steps are involved in the OER,and the activity is strongly controlled by the proton dynamics on the catalyst surface.The results demonstrate the important role of interfacial proton transfer in the OER mechanism,and suggest that proton dynamics at the interface should carefully be considered in the design of future high‐performance catalysts.
基金The financial support from the National Natural Science Foundation of China(Nos.20971046 and 21171057)
文摘Pseudo-first order reaction rate constants of 5,10,15-tris（pentafluorophenyl）corrole Mn（V）-oxo （F_（15）CMn（V）-oxo）,5,15-bis（pentafluorophenyl）-10-（phenyl）corrole Mn（V）-oxo（F_（10）CMn（V）-oxo）,5,15- bis（phenyl）-10-（pentafluorophenyl）corrole Mn（V）-oxo（F_5CMn（V）-oxo） and 5,10,15-tris（phenyl）corrole Mn（V）-oxo（F_0CMn（V）-oxo） with a series of alkene substrates in different solvents were determined by UV-vis spectroscopy.The results indicated that the oxygen atom transfer pathway between Mn（V）-oxo corrole and alkene is solvent-dependent.
基金financially supported by the National Key Research and Development Program of China(2020YFA0210900)the National Natural Science Foundation of China(Nos.21938001,22078072,21961160741 and 21878344)+2 种基金the Guangdong Provincial Key R&D Programme(2019B110206002)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(2017BT01C102)the Research and Innovation Team Construction Project of Guangdong University of Petrochemical Technology(2019rc049).
文摘The development of catalytic aerobic epoxidation by numerous metal complexes in the presence of aldehyde as a sacrificial reductant(Mukaiyama epoxidation)has been reported,however,comprehensive examination of oxygen atom transfer mechanism involving free radical and highly reactive intermediates has yet to be presented.Herein,meso-tetrakis(pentafluorophenyl)porphyrinatooxidovanadium(Ⅳ)(VOTPFPP)was prepared and proved to be efficient toward aerobic olefin epoxidation in the presence of isobutyraldehyde.In situ electron paramagnetic resonance spectroscopy(in situ EPR)showed the generation,transfer pathways and ascription of free radicals in the epoxidation.According to the spectral and computational studies,the side-on vanadium-peroxo complexes are considered as the active intermediate species in the reaction process.In the cyclohexene epoxidation catalyzed by VOTPFPP,the kinetic isotope effect value of 1.0 was obtained,indicating that epoxidation occurred via oxygen atom transfer mechanism.The mechanism was further elucidated using isotopically labeled dioxygen experiments and density functional theory(DFT)calculations.
基金supported by National Key R&D Program of China (No.2018YFA0108300)the Overseas High-level Talents Plan of China and Guangdong Province+3 种基金the Fundamental Research Funds for the Central Universitiesthe 100 Talents Plan Foundation of Sun Yat-sen Universitythe Program for Guangdong Introducing Innovative and Entrepreneurial Teams (No.2017ZT07C069)the Natinoal Natural Science Foundation of China (Nos.22075321,21821003,21890380 and 21905315)。
文摘Exploring platinum group metal-free electrocatalysts with superior catalytic performance and favorable durability for oxygen reduction reaction is a remaining bottleneck in process of developing sustainable techniques in energy storage and conversion. Herein, a hierarchical porous single atomic Fe electrocatalyst(Fe/Z8-E-C) is rationally designed and synthesized via acid etching, calcination, adsorption of Fe precursor and recalcination processes. This unique electrocatalyst Fe/Z8-E-C shows excellent oxygen reduction performance with a half-wave potential of 0.89 V in 0.1 mol/L KOH, 30 m V superior to that of commercial Pt/C(0.86 V), which is also significantly higher than that of typical Fe-doped ZIF-8 derived carbon nanoparticles(Fe/Z8-C) with a half-wave potential of 0.84 V. Furthermore, Fe/Z8-E-C-based Zn-air battery exhibits greatly enhanced peak power density and specific capacity than those of original Fe/Z8-C,verifying the remarkable performance and practicability of this specially designed hierarchical structure due to its efficient utilization of the active sites and rapid mass transfer. This present work proposes a new method to rationally synthesize single atom electrocatalysts loaded on hierarchical porous frame materials for catalysis and energy conversion.
