Theoretical study of p-block metal–nitrogen–carbon single-atom catalysts for the oxygen reduction reaction

Abstract

Systematic theoretical research on the catalytic behaviors of p-block metal (PM)-based PM–N₄ moieties is desirable to guide the design and synthesis of PM–N–C single-atom catalysts (SACs) for the oxygen reduction reaction (ORR). Herein, using first-principles calculations, the suitability of PM–N₄ moieties as active sites for the ORR are systematically investigated. The results show that Sn–N₄ and Pb–N₄ have promising ORR activity with low overpotentials of 0.45 V and 0.55 V, respectively. For the six PM–N₄ sites with strong OH* adsorption, the self-modifying effect of the intermediate OH* is further studied. In–N₄–OH* upon OH* self-modification shows considerably improved ORR activity with a much lower overpotential (0.67 V) compared with that of pristine In–N₄ (1.24 V). The linear OH* self-regulating mechanism is revealed for the first time, from a unique energy perspective and further verified by typical PM–N₃C sites. In–N₃C–OH* and Ge–N₃C–OH* are located near the top of the volcano plot, with overpotentials of 0.35 V and 0.46 V, respectively. Microkinetic simulation is further used to explicitly demonstrate their ORR activities. Our work sheds light on the rational design of highly efficient main-group metal-based PM–N–C SACs for the ORR.