Amorphous versus nanocrystalline RuO2 electrocatalysts: activity and stability for oxygen evolution reaction in sulfuric acid

Abstract

Ruthenium oxide (RuO₂) electrocatalysts possessing high activity and stability are needed to sustain the oxygen evolution reaction (OER) under harsh anodic conditions in acidic water electrolysis systems. Herein, we report the activity and stability of RuO₂ particles coated on a Ti-fibre felt substrate. Amorphous RuO₂ particles of low crystallinity have large electrochemically active surface areas (ECSAs) and high OER activity, but are unstable during the OER in 0.1 M H₂SO₄. However, complete thermal decomposition of a RuCl₃ precursor solution at temperatures above 250 °C yields RuO₂ particles with enhanced crystallinity and greater resistance to dissolution under anodic conditions in H₂SO₄. An optimum calcination temperature of 350 °C produces RuO₂ nanoparticles on a Ti-felt with balanced ECSAs and high crystallinity, while simultaneously achieving high OER activity and enhanced stability. The optimized nanocrystalline RuO₂/Ti-felt(350) electrocatalyst was stable throughout 48 h of operation at 50 mA cm⁻² at pH 1.0 and delivered a stability number greater than 1 × 10⁵, which is comparable to the value provided by more costly IrO₂ electrocatalysts.