A precise understanding of the redox chemistry of Nm-Mn+(like N4-Fe^(2+))systems is essential for fundamental studies and rational design of Nm-Mn+-based electrocatalysts for the oxygen reduction reaction(ORR).Herein,...A precise understanding of the redox chemistry of Nm-Mn+(like N4-Fe^(2+))systems is essential for fundamental studies and rational design of Nm-Mn+-based electrocatalysts for the oxygen reduction reaction(ORR).Herein,three different iron phthalocyanines(FePcs)adsorbed on carbon nanotubes((NH2)4FePc@CNTs,(t-Bu)4FePc@CNTs,and FePc@CNTs)were evaluated to demonstrate the effect of the electron donating power of the substituents on the Fe^(3+)/Fe^(2+)redox potential of FePc@CNTs and the role of these composites as ORR mediators in alkaline media.The Fe^(3+)/Fe^(2+)redox potential of the FePcs was found to shift towards the cathodic region upon substitution with electron-donating groups.This up-field shift in the eg-orbital leads to a lower overlap between the onset potential of the Fe^(3+)/Fe^(2+)redox couple and that of the ORR,and thus,the ORR activity decreased in the following order based on the substitution of FePc:-H>-t-Bu>-NH2.展开更多
Cation substitution in spinel cobaltites(e.g.,ACo2O4,in which A=Mn,Fe,Co,Ni,Cu,or Zn)is a promising strategy to precisely modulate their electronic structure/properties and thus improve the corresponding electrochemic...Cation substitution in spinel cobaltites(e.g.,ACo2O4,in which A=Mn,Fe,Co,Ni,Cu,or Zn)is a promising strategy to precisely modulate their electronic structure/properties and thus improve the corresponding electrochemical performance for water splitting.However,the fundamental principles and mechanisms are not fully understood.This research aims to systematically investigate the effects of cation substitution in spinel cobaltites derived from mixed-metal-organic frameworks on the oxygen evolution reaction(OER).Among the obtained ACo2O4 catalysts,FeCo2O4 showed excellent OER performance with a current density of 10 mA·cm^-2 at an overpotential of 164 mV in alkaline media.Both theoretical calculations and experimental results demonstrate that the Fe substitution in the crystal lattice of ACo2O4 can significantly accelerate charge transfer,thereby achieving enhanced electrochemical properties.The crystal field of spinel ACo2O4,which determines the valence states of cations A,is identified as the key factor to dictate the OER performance of these spinel cobaltites.展开更多
文摘A precise understanding of the redox chemistry of Nm-Mn+(like N4-Fe^(2+))systems is essential for fundamental studies and rational design of Nm-Mn+-based electrocatalysts for the oxygen reduction reaction(ORR).Herein,three different iron phthalocyanines(FePcs)adsorbed on carbon nanotubes((NH2)4FePc@CNTs,(t-Bu)4FePc@CNTs,and FePc@CNTs)were evaluated to demonstrate the effect of the electron donating power of the substituents on the Fe^(3+)/Fe^(2+)redox potential of FePc@CNTs and the role of these composites as ORR mediators in alkaline media.The Fe^(3+)/Fe^(2+)redox potential of the FePcs was found to shift towards the cathodic region upon substitution with electron-donating groups.This up-field shift in the eg-orbital leads to a lower overlap between the onset potential of the Fe^(3+)/Fe^(2+)redox couple and that of the ORR,and thus,the ORR activity decreased in the following order based on the substitution of FePc:-H>-t-Bu>-NH2.
文摘Cation substitution in spinel cobaltites(e.g.,ACo2O4,in which A=Mn,Fe,Co,Ni,Cu,or Zn)is a promising strategy to precisely modulate their electronic structure/properties and thus improve the corresponding electrochemical performance for water splitting.However,the fundamental principles and mechanisms are not fully understood.This research aims to systematically investigate the effects of cation substitution in spinel cobaltites derived from mixed-metal-organic frameworks on the oxygen evolution reaction(OER).Among the obtained ACo2O4 catalysts,FeCo2O4 showed excellent OER performance with a current density of 10 mA·cm^-2 at an overpotential of 164 mV in alkaline media.Both theoretical calculations and experimental results demonstrate that the Fe substitution in the crystal lattice of ACo2O4 can significantly accelerate charge transfer,thereby achieving enhanced electrochemical properties.The crystal field of spinel ACo2O4,which determines the valence states of cations A,is identified as the key factor to dictate the OER performance of these spinel cobaltites.
