A chemical etching strategy to improve and stabilize RuO2-based nanoassemblies for acidic oxygen evolution

RuO2-based catalysts have been widely used for acidic oxygen evolution reaction (OER), a key half reaction of overall water splitting. However, RuO2 suffers from the drawbacks of inferior OER performance in acidic conditions due to its poor stability. We here demonstrate a chemical etching strategy for fabricating a Ru/Fe oxide towards OER, in which Fe species in the pristine Ru/Fe nanoassemblies (P-Ru/Fe NAs) are partially etched by nitric acid (HNO3), leading to the generation of abundant vacancies in the etched Ru/Fe oxide nanoassemblies (E-Ru/Fe ONAs). Owing to the etching of Fe, the local electron density of the lattice O associated with Ru atoms is significantly increased, resulting in the suppression of H2O adsorption on lattice O. On the other hand, the O vacancies in the E-Ru/Fe ONAs can promote the H2O adsorption on metal atoms (i.e., Ru and Fe). Consequently, the optimized E-Ru/Fe ONAs exhibit a superior OER activity with a low overpotential of 238 mV at 10 mA cm−2 in 0.5 M H2SO4, and an enhanced stability with a negligible potential change within 9 h chronopotentiometry test. Theoretical calculations demonstrate that the defective surface of E-Ru/Fe ONA can not only enhance the stability via surface structural modulation, but also optimize the binding strength of the intermediates for promoting OER activity. This work provides an efficient strategy for fabricating active and stable RuO2-based catalysts for OER, which may deepen the research in surface engineering of catalysts. A facile strategy is proposed for fabricating O vacancies in Ru/Fe oxide nanoassemblies (Ru/Fe ONAs), which significantly strengthen the local electron density of the lattice O associated with Ru atoms and facilitate H2O adsorption on Ru. Consequently, the optimized E-Ru/Fe ONAs exhibit a superior acidic OER activity. [Display omitted] •A facile strategy is proposed for fabricating O vacancies in Ru/Fe oxide catalyst.•Vacancies are formed via the etching of Fe by HNO3 in Ru/Fe nanoassemblies.•The local electron density of Ru atoms is significantly strengthened by vacancies.•H2O is preferentially adsorbed on Ru other than lattic O due to electronic effects.•Ru/Fe oxide-based catalyst exhibits an excellent acidic OER activity.