Factors in the utilization of corrosive ruthenium in the oxygen evolution electrode of polymer electrolyte membrane water electrolysis

Abstract

The use of non-Pt materials in polymer electrolyte membrane water electrolysis (PEMWE) anodes is imperative to reduce green hydrogen production costs. Ru provides sufficient electrical and thermal conductivity, but rapidly over-oxidizes to RuO₄²⁻ or H₂RuO₅ during PEMWE device operation. Therefore, this study involved using corrosive Ru instead of expensive Pt to form an interlayer between a Ti porous transport layer and the IrO_x catalyst in PEMWE anodes, while enhancing the water-oxidation-catalyzing ability of IrO_x. The optimized Ru-containing anode was comparable to the Pt-containing equivalent in OER performance (5.5 A cm⁻² at 2.0 V_Cell; ∼80 μg cm⁻² of Ir). Importantly, the Ru in the PEMWE anode functioned stably for >250 h at a practical current density (2.0 A cm⁻²) during current swing operation. Consequently, the Ru-interlayer-based device was comparable to the conventional Pt-interlayer-based counterpart in performance and durability. The relationship between Ru dissolution and local oxygen accumulation at electrode surfaces was clarified.