The reductive demetalation of manganese corroles was investigated in CH2Cl2/HCl (aqueous) solvent by using SnCl2 as reducing agent. It was found that the demetalation yields depend on the substituents of corrole mac...The reductive demetalation of manganese corroles was investigated in CH2Cl2/HCl (aqueous) solvent by using SnCl2 as reducing agent. It was found that the demetalation yields depend on the substituents of corrole macrocycle significantly. Electron- rich manganese corrole undergoes reductive demetalation more easily than electron-deficient ones. The isolated reductive demetalation yield of manganese 5,10,15-tris(phenyl)corrole in present system is moderate (46%). As for electron-deficient Mn(Ⅲ) 5,10,15-tris(pentafluorophenyl)corrole, the acid-induced demetalation in HOAc-HESO4 (V/V = 3:1) is preferable with an isolated yield of 67%.展开更多
The results of research on the adsorption characteristics of materials based on fibrous carbon (CNF) are considered in this paper. It is shown that changing the conditions and procedure of CNF modifying namely specifi...The results of research on the adsorption characteristics of materials based on fibrous carbon (CNF) are considered in this paper. It is shown that changing the conditions and procedure of CNF modifying namely specific adsorption surface, volume of the pore space, and parameters of the pore structure it became possible ultimately to vary in a wide range the adsorption characteristics of obtained materials.展开更多
Transition metal supported N-doped carbon(M-N-C)catalysts for oxygen reduction reaction(ORR)are viewed as the promising candidate to replace Pt-group metal(PGM)for proton exchange membrane fuel cells(PEMFCs).However,t...Transition metal supported N-doped carbon(M-N-C)catalysts for oxygen reduction reaction(ORR)are viewed as the promising candidate to replace Pt-group metal(PGM)for proton exchange membrane fuel cells(PEMFCs).However,the stability of M-N-C is extremely challenging due to the demetalation,H_(2)O_(2)attack,etc.in the strongly oxidative conditions of PEMFCs.In this study,we demonstrate the universal effect of Zn on promoting the stability of atomically dispersed M-Nx/C(M=Co,Fe,Mn)catalysts and the enhancement mechanism is unveiled for the first time.The best-performing dual-metal-site Zn-Co-N-C catalyst exhibits a high half-wave potential(E1/2)value of 0.81 V vs.reversible hydrogen electrode(RHE)in acid and outstanding durability with no activity decay after 15,000 accelerated degradation test(ADT)cycles at 60℃,surpassing most reported Co-based PGM-free catalysts in acid media.For comparison,the Co-N-C in the absence of Zn suffers from a rapid degradation after ADT due to the demetalation and higher H_(2)O_(2)yield.X-ray adsorption spectroscopy(XAS)and density functional theory(DFT)calculations suggest the more negative formation energy(by 1.2 eV)and increased charge transfer of Zn-Co dual-site structure compared to Co-N-C could strength the Co-N bonds against the demetalation and the optimized d-band center accounts for the improved ORR kinetics.展开更多
基金National Natural Science Foundation of China(Nos.20771039,20572027),Research Grant Council of Hong Kong.
文摘The reductive demetalation of manganese corroles was investigated in CH2Cl2/HCl (aqueous) solvent by using SnCl2 as reducing agent. It was found that the demetalation yields depend on the substituents of corrole macrocycle significantly. Electron- rich manganese corrole undergoes reductive demetalation more easily than electron-deficient ones. The isolated reductive demetalation yield of manganese 5,10,15-tris(phenyl)corrole in present system is moderate (46%). As for electron-deficient Mn(Ⅲ) 5,10,15-tris(pentafluorophenyl)corrole, the acid-induced demetalation in HOAc-HESO4 (V/V = 3:1) is preferable with an isolated yield of 67%.
文摘The results of research on the adsorption characteristics of materials based on fibrous carbon (CNF) are considered in this paper. It is shown that changing the conditions and procedure of CNF modifying namely specific adsorption surface, volume of the pore space, and parameters of the pore structure it became possible ultimately to vary in a wide range the adsorption characteristics of obtained materials.
基金National Natural Science Foundation of China(22122202,21972051,22072051,22109121)Natural Science Foundation of Guangdong Province(2021A1515012343)the fund from Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials(Wuhan University of Science and Technology,WKDM202204)。
文摘Transition metal supported N-doped carbon(M-N-C)catalysts for oxygen reduction reaction(ORR)are viewed as the promising candidate to replace Pt-group metal(PGM)for proton exchange membrane fuel cells(PEMFCs).However,the stability of M-N-C is extremely challenging due to the demetalation,H_(2)O_(2)attack,etc.in the strongly oxidative conditions of PEMFCs.In this study,we demonstrate the universal effect of Zn on promoting the stability of atomically dispersed M-Nx/C(M=Co,Fe,Mn)catalysts and the enhancement mechanism is unveiled for the first time.The best-performing dual-metal-site Zn-Co-N-C catalyst exhibits a high half-wave potential(E1/2)value of 0.81 V vs.reversible hydrogen electrode(RHE)in acid and outstanding durability with no activity decay after 15,000 accelerated degradation test(ADT)cycles at 60℃,surpassing most reported Co-based PGM-free catalysts in acid media.For comparison,the Co-N-C in the absence of Zn suffers from a rapid degradation after ADT due to the demetalation and higher H_(2)O_(2)yield.X-ray adsorption spectroscopy(XAS)and density functional theory(DFT)calculations suggest the more negative formation energy(by 1.2 eV)and increased charge transfer of Zn-Co dual-site structure compared to Co-N-C could strength the Co-N bonds against the demetalation and the optimized d-band center accounts for the improved ORR kinetics.