Fabrication of Ir_xTa_100−xO_y as counter electrodes in saline water

One of the key challenges to realize electrolysis of seawater is to develop highly active and stable electrocatalysts in oxygen evolution reaction (OER). This is crucial even for the development of electrocatalysts for hydrogen evolution reaction (HER) using three-electrode configuration because damaged surfaces of counter electrodes (CEs), which exposed to electrochemical oxidative environments often limit the performance of cathodes in working electrodes (WEs) by lowering the electrical conductivity and poisoning the surface of electrocatalysts. Herein, we demonstrate the use of Ir_xTa_100−xO_y as a CE in simulated seawater. Ir_xTa_100−xO_y-coated electrodes as CEs with optimized Ir:Ta ratios enable the high-valence states of Ir for improving activity and selectivity toward the OER. Moreover, the Ir_xTa_100−xO_y CEs ensure unhindered electrochemical performance of Pt for HER in contrast to carbon-based materials, thus highlighting their reliability as a CE.