In-situ local phase-transitioned MoSe ₂ in La _0.5 Sr _0.5 CoO _3-δ heterostructure and stable overall water electrolysis over 1000 hours

Developing efficient bifunctional catalysts for overall water splitting that are earth-abundant, cost-effective, and durable is of considerable importance from the practical perspective to mitigate the issues associated with precious metal-based catalysts. Herein, we introduce a heterostructure comprising perovskite oxides (La _0.5 Sr _0.5 CoO _3–δ ) and molybdenum diselenide (MoSe ₂ ) as an electrochemical catalyst for overall water electrolysis. Interestingly, formation of the heterostructure of La _0.5 Sr _0.5 CoO _3–δ and MoSe ₂ induces a local phase transition in MoSe ₂ , 2 H to 1 T phase, and more electrophilic La _0.5 Sr _0.5 CoO _3–δ with partial oxidation of the Co cation owing to electron transfer from Co to Mo. Together with these synergistic effects, the electrochemical activities are significantly improved for both hydrogen and oxygen evolution reactions. In the overall water splitting operation, the heterostructure showed excellent stability at the high current density of 100 mA cm ⁻² over 1,000 h, which is exceptionally better than the stability of the state-of-the-art platinum and iridium oxide couple.