A Delicate Balance Optimises Water Oxidation Catalysts

The quest for efficient water splitting has triggered a paradigm shift in research, moving focus from metal-centred catalysis to the reactivity of the oxygen structure itself, known as the lattice oxygen-mediated mechanism (LOM). Within this framework, scientists have debated whether performance is driven by metal-oxygen covalency—indicated by 'oxygen 2p holes'—or by 'oxygen vacancies' (missing oxygen atoms). These two factors often compete, creating a chemical tug-of-war.

New findings demonstrate that neither factor works best in isolation. While increasing oxygen 2p holes favours the LOM route, it unfortunately weakens the material's ability to hold onto hydroxide. However, introducing moderate oxygen vacancies can mitigate these negative effects. The study identifies a specific cobaltite perovskite, Sr_0.9Y_0.1CoO_3-δ, which strikes the ideal balance between these parameters. This dual-parameter descriptor offers a coherent explanation for catalytic behaviour and lights the way for designing superior materials under the classic Sabatier principle.