Novel 2D carbon material T-graphene supported 3d transition metal single atoms as efficient oxygen reduction catalysts

Abstract

We propose a novel single atom catalyst structure with weaker adsorption ability than traditional graphene single atoms, and reveal the structure-property relationship to help researchers achieve quick screening of ORR catalysts.

Exploring Spin Distribution and Electronic Properties in FeN4-Graphene Catalysts with Edge Terminations

“…The objective is to understand, modify, and control the spin-density distributions in nanostructured graphene. Among the strategies for shaping graphene’s magnetic properties, doping with heteroatoms has emerged as a general method for tuning magnetic, electronic, optical, and transport properties [ 9 , 18 , 19 , 20 , 21 , 22 , 23 ]. Computational studies using density functional theory (DFT) revealed that doping GNRs with nitrogen, boron, or transition metal (TM) atoms at specific positions can induce thermodynamically stable ferromagnetic GNRs with spin-polarized edge carbons, depending on the edge geometry (zigzag or armchair), ribbon widths, location, and density of dopant atoms [ 9 , 20 , 21 , 24 , 25 , 26 , 27 ].…”

“…The ability of graphene to stabilize various dopants is also used in catalysis by employing graphene to host a variety of active sites, including non-metal dopants and a broad range of single metal atoms, from 3d transition metals to heavier elements, such as Sn and platinum-group metals [ 28 , 29 , 30 ]. In particular, co-doped graphene with transition metals and nitrogen has been emerging as a promising electrocatalyst for oxygen reduction reactions (ORR) [ 22 , 31 , 32 , 33 ], CO 2 conversion [ 34 , 35 , 36 ], or nitrate reductions [ 36 ]. TMNx-graphene has been identified as an efficient catalyst because of its spin polarization [ 36 , 37 ].…”

“…TMNx-graphene has been identified as an efficient catalyst because of its spin polarization [ 36 , 37 ]. In particular, FeN 4 moieties that are covalently integrated in carbonaceous matrices have been established as the most promising precious-metal-free active sites in proton exchange membrane fuel cell cathodes for ORR [ 22 , 32 , 38 , 39 , 40 ]. Unrevealing the origins behind the good reactivity of Fe-N-C catalysts has become an important milestone for a more rational design of non-precious metal catalysts.…”

“…By analyzing the computed and measured Mössbauer quadrupole splitting data, the presence of high-spin Fe(III)-N 4 C 12 porphyrinic structures and low- or medium-spin Fe(II)-N 4 C 10 pyridinic structures in pyrolyzed Fe-N-C catalysts has been established [ 42 ]. DFT studies have revealed the thermodynamic stability of spin-polarized at-edge TM-C x N y defects [ 21 , 22 , 31 , 37 , 47 ]. A high magnetic moment computed in FeN 4 -AGNR and FeN 4 -ZGNR was attributed to parallel spin moments on the localized 3d electrons of Fe atom and 2p electrons of C atoms [ 47 ].…”

“…A high magnetic moment computed in FeN 4 -AGNR and FeN 4 -ZGNR was attributed to parallel spin moments on the localized 3d electrons of Fe atom and 2p electrons of C atoms [ 47 ]. More recent theoretical studies have correlated the ORR activity with the iron magnetic moments in FeN 4 -graphene, owing to the hybridization between spin-polarized Fe3d and O2p orbitals in the activated OH complex [ 22 ]. The enhancement in the performance of the FeN 4 -graphene catalyst was attributed to an alteration in FeN 4 -graphene band structure from metallic to half-metallic [ 48 ], meaning that the spin-up bands have isolating character, whereas spin-down bands have conducting character, or vice versa.…”