Amorphous-rich RuMnOx aerogel with weakened Ru–O covalency for efficient acidic water oxidation

Abstract

Ruthenium dioxide (RuO₂) is one of the most promising acidic oxygen evolution reaction (OER) catalysts to replace the expensive and prevalent iridium (Ir)-based materials. However, the lattice oxygen oxidation induced Ru dissolution during OER compromises the activity and stability. Amorphous materials have been identified as a viable strategy to promote the stability of RuO₂ in acidic OER applications. This study reported a nanoporous amorphous-rich RuMnO_x (A-RuMnO_x) aerogel for efficient and stable acidic OER. Compared with highly crystalline RuMnO_x, the weakened Ru–O covalency of A-RuMnO_x by forming amorphous structure is favorable to inhibiting the oxidation of lattice oxygen. Meanwhile, this also optimizes the electronic structure of Ru sites from overoxidation and reduces the reaction energy barrier of the rate-determining step. As a result, A-RuMnO_x aerogel exhibits an ultra-low overpotential of 145 mV at 10 mA cm⁻² and durability exceeding 100 h, as well as high mass activity up to 153 mA mg⁻¹_Ru at 1.5 V vs. reversible hydrogen electrode (RHE). This work provides valuable guidance for preparing highly active and stable Ru-based catalysts for acidic OER.