Designing an efficient catalyst for acidic oxygen evolution reaction (OER) is of critical importance in manipulating proton exchange membrane water electrolyzer (PEMWE) for hydrogen production. Here, we report a fast, nonequilibrium strategy to synthesize quinary high-entropy ruthenium iridium-based oxide (M-RuIrFeCoNiO ₂ ) with abundant grain boundaries (GB), which exhibits a low overpotential of 189 millivolts at 10 milliamperes per square centimeter for OER in 0.5 M H ₂ SO ₄ . Microstructural analyses, density functional calculations, and isotope-labeled differential electrochemical mass spectroscopy measurements collectively reveal that the integration of foreign metal elements and GB is responsible for the enhancement of activity and stability of RuO ₂ toward OER. A PEMWE using M-RuIrFeCoNiO ₂ catalyst can steadily operate at a large current density of 1 ampere per square centimeter for over 500 hours. This work demonstrates a pathway to design high-performance OER electrocatalysts by integrating the advantages of various components and GB, which breaks the limits of thermodynamic solubility for different metal elements.

Developing high-performance bifunctional electrocatalysts towards the hydrogen evolution/oxidation reaction (HER/HOR) holds great significance for efficiently utilizing hydrogen energy. In this work, a unique class of Mo-modified Ru nanosheet assemblies (Mo–Ru NSAs) have been successfully prepared, where Mo possesses a unique configuration of both a metallic Mo atom and MoO₃. Further structural optimization by density functional theory (DFT) calculations has revealed that the metallic Mo atom is embedded in the Ru lattice while MoO₃ is adsorbed on a partially oxidized Mo atom. As a result, the surface electronic properties and lattice structures of Ru nanosheets have been dramatically altered, leading to optimized adsorption of intermediates and superior HER/HOR performance. In detail, 16 mV is sufficient to drive 10 mA cm⁻² for the HER in 1 M KOH with a durable stability of 250 h. Furthermore, a high mass activity of 2.45 A mg_Ru ⁻¹ towards the HOR in 0.1 M KOH with high stability is also achieved. DFT calculations have further revealed that the coupling of a Mo atom and MoO₃ can facilitate the rapid decomposition of H₂O and generate highly active sites by steric hindrance, thereby enabling high bifunctional activity. It is anticipated that this work would enlighten the construction of more advanced bifunctional catalysts via surface and lattice engineering.

A viable anode of atomic Sb with a super-coordinated O₂Sb₁N₄ structure anchored on N-doped micropore carbon nanosheets (O–Sb–N SA@NC) is developed, demonstrating significantly enhanced performance in both half and full potassium-ion batteries.