Manganese Dioxide-Based Catalysts with Low Ir Content for High-Durability PEM Water Electrolysis

Introduction Proton exchange membrane water electrolysis (PEMWE) is a promising technology for hydrogen production. However, the local environment of the anode in PEMWE systems is highly acidic, primarily due to the oxygen evolution reaction (OER; 2H 2 O → O 2 + 4H + + 4e − ). Furthermore, the available anode materials are limited to Ir-based materials. Current technology necessitates a high Ir loading of 1−2 mg/cm 2 to achieve activity and durability. Nevertheless, the future demand for hydrogen is anticipated to increase to the GW scale, posing challenges in meeting this demand with existing Ir resources (5~7 tons/year) when the Ir loading is 2 mg/cm 2 (0.5 mgIr/W). Meanwhile, Tosoh has been actively involved in the electrolytic manganese dioxide (EMD) industry. EMD is synthesized through the anodic oxidation of Mn 2+ ions (Mn 2+ + 2H 2 O → MnO 2 + 4H + + 2e − ) under acidic conditions, making it potentially suitable for PEMWE. In this study, a very small amount of Ir (