Ultrafine semi-crystalline Y-doped RuO₂ for highly active and durable proton-exchange-membrane water electrolysis

Activity and stability are often inversely entwined in catalysis, especially for the water oxidation reaction (WOR) to generate hydrogen under acidic media. Here, we show that an ionic-mismatch-induced semi-crystalline Y_0.3Ru_0.7O₂ gives rise to exceptionally active and stable WOR performance. The mismatched ionic radii and valences between Y³⁺ and Ru⁴⁺ leads to a strongly bonded hybrid nanostructure of ultra-fine crystalline and amorphous domains. The short-range ordered structure also leads to a reduced adjacent distance, which facilitates a more efficient and stable dual-site coupling mechanism with an extremely low overpotential of 170 mV at 10 mA cm⁻² and prolonged stability over 300 h in an acidic electrolyte. A proton-exchange-membrane (PEM) water electrolyzer loaded with the catalyst shows an outstanding performance with only 1.64 V to reach 1 A cm⁻² and stable operation at 0.5 A cm⁻² over 300 h, demonstrating its outstanding potential for practical applications in PEM electrolysis. © 2025 Elsevier Inc.