Trace anodic migration of iridium and titanium ions and subsequent cathodic selectivity degradation in acid electrolysis systems

The oxygen evolution reaction in acidic electrolyzers requires the presence of stable catalysts and current collectors at the anode. IrO2 catalysts and Ti current collectors are among the best in this regard. We show evidence of iridium and titanium corrosion and subsequent membrane crossover in long-term experiments of proton-exchange membrane electrolyzers for H2O2 production. The accumulation of trace iridium at the cathode was linked to degraded performance and increased cathodic current from hydrogen evolution. Detection of trace metal content at the cathode electrodes was enabled by prompt-gamma ray activation analysis and neutron activation analysis. These findings are not just relevant for H2O2 electrolyzers but to any system using iridium-based anode catalysts, including CO2 electroreduction. (C) 2019 Published by Elsevier Ltd.