Electronic structure regulation of RuIrTaOx induces highly efficient acidic OER†

The widespread application of proton exchange membrane water electrolyzers (PEMWEs) is limited by the high noble metal loading and high overpotential of the anodic oxygen evolution reaction (OER). Ruthenium (Ru) is widely considered a low-cost alternative to iridium (Ir) as an anode electrocatalyst in PEMWEs. However, due to the inherent high lattice oxygen reactivity of ruthenium-based catalysts, which can lead to irrepressible ruthenium leaching and structural collapse, most reported ruthenium-based catalysts usually only work for tens of hours in PEMWEs. We prepared ultra-thin two-dimensional materials RuIrTaO_x with abundant grain boundaries using a facile molten salt method, containing only 16.17 wt% of extremely low Ir content. The overpotential at a current density of 10 mA cm⁻² was only 237 mV, and there was no significant decay observed during continuous OER for up to 200 h. The RuIrTaO_x membrane electrode assembly (MEA) possesses excellent PEMWE activity, with only 1.743 V at 2 A cm⁻² current density and a stable reaction for 500 h. The ultra-thin two-dimensional polycrystalline material has achieved a larger specific surface area, and the abundant grain boundaries and surface oxygen vacancies (O_v) provide more active sites. The doping of Ta adjusts the electronic structure, enhancing its OER activity, conductivity and stability.