The polymer electrolyte membrane (PEM) electrolyzers are burdened with costly iridium (Ir)-based catalysts and high operation overpotentials for the oxygen evolution reaction (OER). The development of earth-abundant, highly active, and durable electrocatalysts to replace Ir is a critical step in reducing the cost of green hydrogen production. Here we develop a Ru₅Mo₄O_x binary oxide catalyst that exhibits high activity and stability in acidic OER. The electron-withdrawing property of Mo enriches the electrophilic surface oxygen species, which promotes acidic OER to proceed via the adsorbate evolution pathway. As a result, we achieve a 189 mV overpotential at 10 mA·cm⁻² and a Tafel slope of 48.8 mV·dec⁻¹. Our catalyst demonstrates a substantial 18-fold increase in intrinsic activity, as evaluated by turnover frequency, compared to commercially available RuO₂ and IrO₂ catalysts. Moreover, we report a stable OER operation at 10 mA·cm⁻² for 100 h with a low degradation rate of 2.05 mV·h⁻¹.

Electrochemical CO₂ reduction has the vast potential to neutralize CO₂ emission and valorizes this greenhouse gas into chemicals and fuels under mild conditions. Its commercial realization hinges on catalyst innovation as well as device engineering for enabling reactions at industrially relevant conditions. Copper has been widely examined for the selective production of multicarbon chemicals particularly ethylene, while there is still a substantial gap between the expected and the attainable. In this work, we report that the surface promotion of copper with alumina clusters is a viable strategy to enhance its electrocatalytic performance. AlO_x-promoted Cu catalyst is derived from Cu-Al layered double hydroxide nanosheets after alkali etching and cathodic conversion. It can catalyze CO₂ to ethylene and multicarbon products with great selectivity and stability far superior to pristine copper in both an H-cell and a zero-gap membrane electrode assembly (MEA) electrolyzer. The surface promotion effect is understood via computational simulations showing that alumina clusters can stabilize key reaction intermediates (*COOH and *OCCOH) along the reaction pathway.