The uniqueness of Janus: A key element in breakthrough oxygen evolution reaction and oxygen reduction reaction bifunctional electrocatalyst design

The development of efficient, cost-effective, and environmentally friendly electrocatalysts is a fundamental prerequisite for advancing renewable energy storage and conversion technologies. Focusing on bifunctional electrocatalyst systems for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), we find that the Janus-type two-dimensional (2D) transition metal chalcogenide SnSSe monolayer offers a unique combination of electronic structure and multiple reactive sites suitable for dual-function catalysis. Based on density functional theory (DFT) calculations, we demonstrate that single-atom modification is an effective strategy to endow the SnSSe substrate with both ORR and OER catalytic capabilities. Among the eighteen configurations doped with transition metals (TM) examined, the Pd-V S , Pd-V Se , Pt-V S , and Pt-V Se @SnSSe systems exhibit superior electrochemical stability and catalytic potential, primarily due to their higher dissolution potentials. Their catalytic excellence is attributed to the simultaneous reduction in overpotentials and enhancement of reaction kinetics, governed by both thermodynamic equilibrium and kinetic reaction pathways. Notably, Pt-V Se @SnSSe shows the most promising performance, achieving theoretical overpotentials of η ORR = 0.43 V and η OER = 0.40 V, which surpass those of conventional benchmark catalysts Pt(111) and RuO 2 (110). This superior activity originates from a reconstruction of the electronic structure triggered by changes in the coordination environment. This work not only elucidates the structure–activity relationship of bifunctional catalytic centers but also provides a theoretical foundation for the application of Janus-type two-dimensional materials in metal air batteries and other energy conversion devices. • This article discusses a novel two-dimensional material, Janus SnSSe, and demonstrates its potential as an outstanding electrocatalyst. • Transition metal doping can significantly enhance the intrinsic performance of two-dimensional materials. • This work designs single-atom catalysts by doping transition metals (Fe, Co, Ni, etc.) at S/Se-vacancy sites in Janus SnSSe. • DFT reveals a single-atom strategy enabling dual ORR/OER functionality in Janus SnSSe, screening three monofunctional (e.g., Pd-V S ) and one bifunctional (Pt-V Se @SnSSe) catalysts. • The bifunctional Pt-V Se @SnSSe exhibits low overpotentials (OER: 0.43 V, ORR: 0.40 V), outperforming commercial benchmarks.