Theoretical insight of pyrite-like bimetallic diselenides for oxygen reduction reaction

Transition metal dichalcogenides (TMDs) have been widely considered as one of the promising candidates to replace platinum-based oxygen reduction reaction (ORR) catalysts due to their attractive properties. However, the single active site in such catalysts poses challenges in surpassing the inherent limits of scaling relations between adsorption energy of multi-intermediates in ORR catalytic process. Herein, inspired by the concept of multiple active centers, we design a series of stable pyrite-like bimetallic diselenides (A0.5B0.5Se2, A = Mn, Fe, Co, Ni, B = Cu, Cd, Sn) as catalysts, which aim at enhancing ORR catalytic activity through synergistic effect in dual active sites. Through density functional theory calculations, we find that the ORR activities of most A0.5B0.5Se2 catalysts are comparable to or even better than those of the noble metal Pt, verifying the promotional ORR activities of A0.5B0.5Se2. Among them, Co0.5Sn0.5Se2 has an overpotential of 0.31 V, which shows better catalytic performance than Pt for ORR. Such improvement is attributed to the tandem reaction mechanism and the reduction in the barrier for the rate-determining steps, resulting from the presence of dual active sites within Co0.5Sn0.5Se2. The projected density of states (PDOS) and Bader charge analysis reveal that the excellent catalytic activity is contributed by the strong d-p orbital hybridization between Co and Sn in the Co0.5Sn0.5Se2, which significantly weakens the over-adsorption of the crucial O* intermediates. These findings provide valuable theoretical insights for designing optimum ORR catalysts.