Stabilizing ruthenium dioxide with cation-anchored sulfate for durable oxygen evolution in PEMWE

Abstract

Abstract Ruthenium dioxide (RuO2) is considered as the most promising alternative to the prevailing but expensive iridium (Ir)-based oxygen evolution reaction (OER) catalysts for proton-exchange membrane water electrolyzers (PEMWEs). However, the stability of RuO2 in PEMWEs has remained poor due to the over-oxidation of under-coordinated lattice oxygen (O) and the consequent formation of O vacancies (Vo) at high oxidation potentials under acidic corrosive conditions. Here, we propose an oxyacid anion protection mechanism to prevent the formation of Vo on the RuO2 surface by forming coordination-saturated lattice O. Combining density functional theory calculations, electrochemical measurements, and a suite of operando spectroscopies, we showcase that barium (Ba)-anchored sulfate can greatly impede Ru loss and extend the lifetime of Ru-based catalysts during acidic OER while maintaining the activity. The as-prepared Ba0.3(SO4)δW0.2Ru0.5O2−δ, when integrated into a PEMWE using 0.5 M H2SO4 as the electrolyte, can be stably operated for > 300 h at 500 mA cm−2. This work paves a new way for designing stable and active OER catalysts toward acidic water splitting.