(Invited) Passivated Anodes in Anion-Exchange Membrane Water Electrolyzers

Abstract

Understanding and engineering the catalyst-electrolyte interface are important for many electrochemical devices. In anion exchange membrane water electrolysis (AEMWE) specifically, the durability of the system is limited by substantial oxidative ionomer degradation at the anodic potentials for oxygen evolution reaction (OER) at the anode. We understand that oxidative ionomer degradation at the anodes is due to the electron transfer from ionomer to the electrode as there is electrical contact between catalysts and ionomers. Here a thin layer of transition metal oxide coating is applied as a passivation (insulating) layer at the catalyst-ionomer interface at the anodes to suppress ionomer degradation and enhance the durability of AEMWE. We investigate the optimal thickness of the metal oxide coatings in Ir- and Co-based electrode systems and observe that the thin layer of metal oxide films on top of the catalyst layers improves the voltage degradation and protects ionomer from oxidative degradation. This work helps us understand the interaction between catalysts and ionomers and solve the durability problems in AEMWE systems using interfacial engineering.