Grain-Boundary-Rich Mo-Doped RuO2 for Highly Efficient and Stable Proton-Exchange-Membrane Water Electrolysis

RuO2-based oxygen evolution reaction electrocatalysts have gained considerable attention as promising alternatives to replace expensive iridium-based materials in proton-exchange-membrane water electrolysis (PEMWE). Nevertheless, the structural destruction of RuO2 and the dissolution of Ru atoms under high current densities hinder its instability. In this work, we introduced Mo into the RuO2 lattice, which not only disrupted the long-range periodic structure but also the "site blocking" effect of Mo enabling the formation of ultrafine nanocrystals (4.3 nm) of RuO2 with abundant grain boundaries (GB-Mo-RuO2) at a higher temperature (500 °C). The developed GB-Mo-RuO2 exhibited lower overpotentials of 185 and 280 mV and excellent stability of 450 and 150 h at 10 and 100 mA cm-2, respectively. The introduction of Mo and GBs reduced the energy barrier in the rate-determining step and the solubility of Ru, thereby boosting both the activity and the stability of the catalyst. The PEMWE with GB-Mo-RuO2 as the anode exhibited cell voltages of 1.65 and 1.85 V at 1 and 2 A cm-2, respectively, and an extremely low decay rate (56.4 μV h-1) at 1 A cm-2 during 160 h.