Two-Dimensional π-Conjugated Metal Bis(dithiolene) Complex Nanosheets as Selective Catalysts for Oxygen Reduction Reaction

Abstract

Developing high activity and low price catalysts for the oxygen reduction reaction (ORR) is of critical importance for the commercial application of polymer electrolyte membrane fuel cells. On the basis of density functional theory, the catalytic activity of π-conjugated metal bis(dithiolene) complex nanosheets (MC4S4, where M denotes Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt) for the ORR has been investigated systematically. It is found that the ORR activity of MC4S4 is sensitive to the selection of the central metal atom. The adsorption energies of ORR intermediates on MC4S4 decrease as the central atom varies from group 8 to group 10. The free energy change of the rate-determining step in the ORR increases in the order of IrC4S4 < CoC4S4 ≈ RhC4S4 < FeC4S4 < PdC4S4 ≈ PtC4S4 < NiC4S4 < RuC4S4 < OsC4S4. Due to the optimal adsorption properties, the IrC4S4 nanosheet shows the best ORR catalytic activity among the nine studied MC4S4 nanosheets. The free energy change of the rate-determining step in the ORR at high electrode potential follows an inverted volcano curve as a function of the adsorption strength of OH. This work may open new avenues for the development of high-performance ORR catalysts.