Construction of Single-Atom Catalysts for N, O Synergistic Coordination and Application to Electrocatalytic O2 Reduction.

Abstract

Replacing expensive platinum oxygen reduction reaction (ORR) catalysts with atomically dispersed single-atom catalysts is an effective way to improve the energy conversion efficiency of fuel cells. Herein, a series of single-atom catalysts, TM-N2O2Cx (TM=Sc-Zn) with TM-N2O2 active units, were designed, and their catalytic performance for electrocatalytic O2 reduction was investigated based on density functional theory. The results show that TM-N2O2Cx exhibits excellent catalytic activity and stability in acidic media. The eight catalysts (TM=Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) are all 4e- reaction paths, among which Sc-N2O2Cx, Ti-N2O2Cx, and V-N2O2Cx follow dissociative mechanisms and the rest are consistent with associative mechanisms. In particular, Co-N2O2Cx and Ni-N2O2Cx enable a smooth reduction in O2 at small overpotentials (0.44 V and 0.49 V, respectively). Furthermore, a linear relationship between the adsorption free energies of the ORR oxygen-containing intermediates was evident, leading to the development of a volcano plot for the purpose of screening exceptional catalysts for ORR. This research will offer a novel strategy for the design and fabrication of exceptionally efficient non-precious metal catalysts on an atomic scale.