Nanocomposite ruthenium oxide electrocatalysts for the low-pH oxygen evolution reaction

Abstract

Despite high activity of the Ru-based oxygen evolution reaction (OER) electrocatalysts, their application in polymer electrolyte membrane water electrolysers is limited by insufficient stability. Aiming to address this, we explored a new approach to stabilise the nanoparticular RuO2 catalyst by combining with Mn, V, W and/or Mo oxides. Composite materials were synthesised using a solution-based process followed by calcination, the conditions of which, along with the catalyst composition, were optimised. The best performance was provided by combining MnOx and MoOx to stabilise RuO2 within a composite catalyst having a suboptimal composition of [Ru0.6+Mo0.3+Mn0.2]Ox. When tested in aqueous 0.5 M H2SO4, [Ru+Mo+Mn]Ox immobilised on a flat substrate remained stable for >100 h at ambient temperature while sustaining the OER rate of 10 mA cm-2 (ca 100 A gRu 1) at an overpotential of ca 0.27 V. At 80 ± 1°C and 100 mA cm-2 (ca 1000 A gRu-1), stable performance at an overpotential of ca 0.28 V was demonstrated for 47-50 h with no significant changes to the catalyst composition and morphology. Physical characterisation suggests that the improved stability of [Ru0.6+Mo0.3+Mn0.2]Ox might be associated with the suppression of overoxidation of RuO2 by the intimate intermixing with the [Mo+Mn]Ox matrix.