The development of highly active electrocatalysts for the oxygen evolution reaction (OER) in proton exchange membrane water electrolyzers (PEMWEs) has garnered significant scientific intrigue. Herein, we report a facile two-step hydrothermal and annealing method for synthesizing cerium-doped ruthenium dioxide nanoparticles (Ce-RuO₂) as efficient OER electrocatalyst in PEM electrolyzer, which exhibits superior OER catalytic performance and durability. More impressively, in-situ characterizations of Ce-RuO₂ as the anode catalyst in membrane electrode assembly is employed, and the results demonstrate that it exhibits reduced kinetic losses, higher catalytic activity, and enhanced stability compared to commercial RuO₂ in PEMWE. In addition, density functional theory (DFT) calculations further confirm that Ce doping maintains its valence state and redistributing the density states of Ru species, thereby enhancing its activity and stability during the OER processes.

The oxygen evolution reaction (OER) represents an anodic reaction for a variety of sustainable energy conversion and storage technologies, such as hydrogen production, CO₂ reduction, etc. To realize the large-scale implementation of these technologies, the sluggish kinetics of the OER resulting from multi-step proton/electron transfer and occurring at the gas–liquid–solid triple-phase boundary needs to be accelerated. Manganese oxide-based (MnO_x) materials, especially MnO₂, have become promising non-precious metal electrocatalysts for the OER under acidic conditions due to the good trade-off between catalytic activity and stability. This paper reviews the recent progress of MnO₂-based materials to catalyze the OER through either the traditional adsorbent formation mechanism (AEM) or the emerging lattice-oxygen-mediated mechanism (LOM). Pure manganese dioxide OER catalysts with different crystalline structures and morphologies are summarized, while MnO₂-based composite structures are also discussed, and the application of MnO₂-based catalysts in PEMWEs is summarized. Critical challenges and future research directions are presented to hopefully help future research.