Synergistic Fe/Co Doping and Vacancy Engineering for Stable RuO_x in Acidic OER

RuO₂ is one of the most effective catalysts for the oxygen evolution reaction (OER) in proton-exchange membrane water electrolyzers (PEMWEs); however, its long-term stability is hindered by Ru dissolution under harsh electrochemical conditions. In this study, we explore the combined effects of metal doping and oxygen vacancy engineering on enhancing the stability performance of RuO₂-based catalysts. Using Fe or Co as dopants, we demonstrate that doping not only decreases the Ru valence but also induces a significant enrichment of oxygen vacancies. The obtained Fe-RuO_x and Co-RuO_x catalysts exhibit small overpotentials of 191 and 203 mV at 10 mA cm^-2, respectively, and both can be sustained for over 500 h in an acidic electrolyte with negligible degradation. Furthermore, both the Fe-RuO_x- and Co-RuO_x-based PEMWEs can operate for more than 250 h at 100 mA cm^-2. Density functional theory simulation reveals that the incorporation of Fe or Co dopants could weaken the adsorption of OOH* on Ru, thereby lowering the onset potential of the OER and improving the catalytic activity. Moreover, the abundant oxygen vacancies could increase the reconstruction energy of the RuO₂ (110) surface, thereby effectively suppressing Ru dissolution and enhancing catalyst stability. These findings provide valuable insights into the design of highly stable Ru-based catalysts for acid-based water electrolysis.