Eliminating over-oxidation of ruthenium oxides by niobium for highly stable electrocatalytic oxygen evolution in acidic media

Proton exchange membrane (PEM) water electrolysis shows advan-tages including high current density, high efficiency, and compact configuration but suffers from the scarcity and high price of iridium (Ir)-based anodic catalysts. Herein, insoluble niobium (Nb)-incorpo-rated RuO2 with a high valence state was designed as an Ir-free cata-lyst for active and stable acidic oxygen evolution reaction (OER). Nb0.1Ru0.9O2 exhibited a low overpotential (204 mV) and superb stability with an ultralow degradation rate (25 mV/h) over a 360-h durability test at 200 mA cm -2, which is only 1/100th of the decay rates of other Ru-based catalysts measured at 10 mA cm -2. The PEM electrolyzer with Nb0.1Ru0.9O2 as an anode survived from a 1 00-h operation at 300 mA cm -2. The strengthened adsorption of oxygen intermediates to active Ru sites reduced the OER energy barrier, while the enhanced electron transfer to Ru by Nb doping and formation of Nb5+ during the OER process extended catalyst's durability.