Sulfur coordination engineering of molybdenum single-atom for dual-functional oxygen reduction/evolution catalysis

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysis are required in metal-air batteries and an efficient dual-functional single-atom catalyst (SAC) is still lacking. This is partly because of the limited synthesis strategies to modify the coordination environment of metal centers in SACs. Herein, we report a genetic strategy, transformation from thiometallate anions in the precursor to metal-sulfur bonding in carbon, producing hollow-sphere-structured Mo SAC with O/N/S co-coordination as an efficient ORR/OER dual-functional catalyst. The MoS42--doped polydopamine have O/S co-coordination for Mo, which converts into S/ O/N co-coordination in carbon during pyrolysis. We established that coordination engineering, specifically S coordination, could boost the ORR catalysis of Mo SAC. The low ORR half-wave potential (E-1/2) and small Tafel slope are among the best of Mo-based non-noble metal catalysts. The OER overpotential of 303 mV at 10 mA cm(-2) is significantly lower than that of commercial IrO2, and Pt/C. Assembled Zn-air batteries can work steadily for 90 h without significant voltage decay. Our strategy can be extended to the synthesis of other group-V and group-VI metal hollow SACs with an S coordination, such as W.

Automated summary

In this study, a genetic strategy was used to synthesize an efficient dual-functional catalyst, hollow-sphere-structured Mo SAC, for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). By modifying the coordination environment of the metal-sulfur bonding in the precursor, the researchers successfully enhanced the ORR catalysis of Mo SAC. The synthesized catalyst showed excellent performance in both ORR and OER, making it a promising candidate for metal-air batteries.