Two Birds with One Stone: Contemporaneously Enhancing OER Catalytic Activity and Stability for Dual-Phase Medium-Entropy Metal Sulfides

Transition metal-based sulfides exhibit remarkable potential as electrocatalysts for oxygen evolution reaction (OER) due to the unique intrinsic structure and physicochemical characteristics. Nevertheless, currently available sulfide catalysts based on transition metals face a bottleneck in large-scale commercial applications owing to their unsatisfactory stability. Here, the first fabrication of (FeCoNiMn2)S2 dual-phase medium-entropy metal sulfide (dp-MEMS) is successfully achieved, which demonstrated the expected optimization of stability in the OER process. Benefiting from the "cell wall" -like structure and the synergistic effect in medium-entropy systems, (FeCoNiMn2)S2 dp-MEMS delivers an exceptionally low overpotential of 169 and 232 mV at current densities of 10 and 100 mA cm-2, respectively. The enhancement mechanism of catalytic activity and stability is further validated by density functional theory (DFT) calculations. Additionally, the rechargeable Zn-air batteries integrated with FeCoNiMn2)S2 dp-MEMS exhibit remarkable performance outperforming the commercial catalyst (Pt/C+RuO2). This work demonstrates that the dual-phase medium-entropy metal sulfide-based catalysts have the potential to provide a greater application value for OER and related energy conversion systems. (FeCoNiMn2)S2 dual-phase medium-entropy metal sulfide (dp-MEMS) demonstrates ultra-efficient catalytic activity and surprisingly stability for oxygen evolution reaction (OER). The coexistence of dual-phase (FCC + HCP) structures effectively inhibits the structure collapse and performance attenuation during OER processes. Density functional theory calculations reveal that the formation of (FeCoNiMn2)S2 dp-MEMS results in the proximity of the d-band center to the Fermi level.image