Density Functional Theory Study of Oxygen Evolution Reaction Mechanism on Rare Earth Sc-Doped Graphene

The development of a stable catalyst with excellent catalytic performance for the oxygen evolution reaction (OER) in alkaline environments is a key reaction in various electrochemical technologies. In this work, single-atom catalysts (SACs) systems in which scandium (Sc), a rare earth metal, with different N/C coordination environments (ScNxC3-x@SACs and ScNxC4-x@SACs of Sc) were systematically studied with the help of density functional theory (DFT) calculations. The results of the structural thermodynamic stability analysis indicated that the ScNxC3-x@SACs and ScNxC4-x@SACs systems are more stable with increasing N atom doping concentration around Sc. The ScN3, ScN3C, and ScN4 with better stability were selected as the objects of subsequent research. However, ScN3 and ScN4 form Sc(OH)(2)N-3 and Sc(OH)(2)N-4 structures with double-hydroxyl groups as ligands because of the strong adsorption of OH species, whereas the strong adsorption of OH species by ScN3C causes structural instability. Here, the overpotential (eta) of Sc(OH)(2)N-3 was 1.03 V; Sc(OH)(2)N-4 had two reaction paths and the eta of path 1 was 0.80 V, which was 0.30 V lower than that of path 2. Therefore, Sc(OH)(2)N-4 can be used as a stable and promising OER catalyst with easy desorption of O-2 and good cycle performance. The hydroxyl ligand modification of Sc-NxC3-x@SACs and Sc-NxC4-x@SACs provides a method for studying the catalytic performance of other rare earth elements.