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

Abstract

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.