Hydrogen stored in Ru/SnO2 induce alkaline hydrogen oxidation reactions in a wide potential range

Abstract

Ruthenium (Ru) is a promising low-cost alternative to platinum (Pt) as an anode alkaline hydrogen oxidation reaction (HOR) catalyst. However, excessive OH_ad adsorption on metallic Ru at high potentials leads to over-oxidation, causing performance decay. We propose a method to remove excess OH_ad from active sites on Ru using interstitial hydrogen stored in SnO₂ catalysts. The Ru/SnO₂ heterojunction catalyst has been designed to demonstrate its high HOR stability in a wide potential range. The exchange current density (j₀) and kinetic current density (j_k) for Ru/SnO₂ reach 3.19 mA cm⁻² and 46.13 mA cm⁻², which are 5.23 times and 41.56 times of Ru/C, respectively. This activity can maintain up to high potentials (about 1.0 V vs. RHE). Ru/SnO₂ shows an anti-deactivation performance with 87.7% of the current density maintained at 1.0 V, even better than Pt/C. Hydrogen stored in SnO₂ effectively removes OH_ad intermediates from the surface of Ru through HOR, alleviating the issue of OH_ad over-adsorption. Consequently, this allows for dissociative adsorption of hydrogen molecules via the Tafel reaction at higher potentials. This research clarifies the mechanism behind HOR performance decay at elevated potentials and offers insights for designing stable Ru-based alkaline HOR catalysts without activity loss under such conditions.