Cobalt-based oxides are renowned for their excellent activity in the oxygen evolution reaction (OER), making them promising alternatives to precious metal catalysts. Among these, β-CoMoO₄, with its wolframite structure, exhibits superior OER performance compared to widely studied cobalt-based perovskite oxides. However, its underlying catalytic mechanism remains largely unexplored. In this study, we synthesized β-CoMoO₄ using a hydrothermal method and achieved remarkable OER catalytic performance in an alkaline environment, with an overpotential of 366 mV at a current density of 10 mA/cm² and an intrinsic activity of 180 μA/cm_ox² at 1.55 V (vs. reversible hydrogen electrode (RHE)). Following OER activation, the micron-sized rod-like structure of β-CoMoO₄ dissociates as a whole and reconstructs into amorphous CoOOH, forming a hexagonal flake structure on the scale of hundreds of nanometers. This transformation provides abundant surface active sites with a low-coordination structure. By combining in situ X-ray absorption fine structure (XAFS) with cyclic voltammetry (CV) scanning, we investigated the kinetic behavior of the active sites of β-CoMoO₄ as a function of potential. The results indicate that the Co ions in this low-coordination structure can be pre-oxidized at relatively low voltages. Therefore, the excellent OER performance of β-CoMoO₄ is attributed to its unique bulk-phase reconstruction behavior and the strong deprotonation ability of the in situ generated amorphous low-coordination active structure. Our research provides valuable insights for the development of new and efficient cobalt-based oxide electrocatalysts for water-splitting applications.

The development of an efficient and low-cost electrocatalyst for the oxygen evolution reaction (OER) via an eco-efficient route is a desirable, although challenging, outcome for overall water splitting. Herein, an iron-rich La_0.6Sr_0.4Co_0.2Fe_0.8O_2.9 (LSCF28) perovskite with an open porous topographic structure was developed as an electrocatalyst by a straightforward molten-salt synthesis approach. It was found that porosity correlates with both the iron content and the molten-salt approach. Benefiting from the large surface area, high activity of the porous internal surface, and the optimal electronic configuration of redox sites, this inexpensive material exhibits high performance with a large mass activity of 40.8 A·g^–1 at a low overpotential of 0.345 V in 0.1 M KOH, surpassing the state-of-the-art precious metal IrO₂ catalyst and other well-known perovskites, such as Ba_0.5Sr_0.5Co_0.8Fe_0.2O₃ and SrCoO_2.7. Our work illustrates that the molten-salt method is an effective route to generate porous structures in perovskite oxides, which is important for energy conversion and storage devices.