Regulation of Electron and Mass Transport Pathways in Efficient and Stable Low‐Loading PEM Water Electrolyzers

Abstract Improving the utilization of iridium in proton exchange membrane (PEM) water electrolyzer is critical in reducing their cost for future development. Titanium dioxide (TiO 2 ) has notable electrochemical stability at high operating potential and has been developed as a promising support of iridium‐based OER nano‐catalysts. However, limited by insufficient conductivity, the iridium content on TiO 2 support catalysts is normally above 50 wt.%. Herein, support is provided for iridium on conductivity‐enhanced TiO 2 for low‐iridium‐loading PEMWE, successfully reducing the iridium content to 28 wt.% by the regulation of electron transport pathway. A new ionomer distribution strategy is then applied to the Ir@Pt@TiO 2 catalyst layer to release the iridium sites and regulate the local mass transport pathways in the anode. This work reveals that the catalyst‐ionomer interface played an important role in activity and stability in the anode of PEMWE. Building a thin and uniform ionomer distribution on supports with iridium exposure can result in continuous proton and electron transport pathways, promoting bubble escape, and exposing more effective active sites during reaction situations. This work provides a novel perspective for future research on the catalyst‐ionomer interface and mass transport in PEMWEs.