Engineering metal-oxide interfaces via controlled exsolution in Ir-doped Y2Ru2O7 pyrochlore for superior hydrogen evolution reaction

Developing efficient and durable electrocatalysts for hydrogen evolution reaction (HER) is crucial for advancing sustainable energy technologies. Pyrochlore oxides show promise due to their structural versatility, but their application in HER is limited by weak hydrogen binding, poor conductivity, and insufficient active site exposure. Here, we demonstrate a controlled in-situ exsolution approach to create optimized RuIr/Y₂O₃ heterointerfaces from Ir-doped Y₂Ru₂O₇ pyrochlore oxide. Through systematic tuning of reduction parameters, we achieve precise control over size and distribution of exsolved RuIr nanoparticles, forming intimate metal-oxide heterojunctions with enhanced charge transfer properties. The optimized YRIO-450-8H (Y₂Ru_1.7Ir_0.3O₇ reduced at 450 °C for 8 h) catalyst exhibits exceptional HER performance, requiring only 20 and 30 mV overpotential to deliver 10 mA cm⁻² in alkaline and acidic media, respectively, outperforming commercial Pt/C. Mechanistic investigations combining advanced characterizations and DFT calculations reveal that the remarkable activity stems from synergistic effects: (1) optimized hydrogen binding energy (−0.13 eV) at RuIr sites, (2) electronic structure modulation at the metal-oxide interface, and (3) abundant oxygen vacancies facilitating water dissociation. The catalyst maintains activity over 120 h in alkaline and 55 h in acidic conditions, providing fundamental insights into exsolution mechanisms and design principles for high-performance heterogeneous electrocatalysts.