Directly Coated Iridium Nickel Oxide on Porous‐Transport Layer as Anode for High‐Performance Proton‐Exchange Membrane Water Electrolyzers

Abstract Developing a high‐performance anode design is important for a low‐cost proton‐exchange membrane water electrolyzer (PEMWE). In this study, an iridium nickel oxide directly coated anode (IrNiO_x electrode) for high‐efficient PEMWE is reported. Five IrNiO_x electrodes with different Ir‐to‐Ni ratios are developed using co‐electrodeposition. The resulting electrodes contain a thin IrNiO_x layer on the carbon substrate. To develop the PEMWE incorporating IrNiO_x electrode, the effect of fabrication methods, catalyst compositions, and porous transport layer are investigated. Consequently, the IrNiO_x electrode prepared with 7:3 precursor solution (Ir_0.5Ni_0.5O_x) exhibits higher oxygen evolution reaction activity with a smaller overpotential than the electrode prepared with 10:0 precursor solution (IrO_x) and the commercial IrO₂. Furthermore, the performance of the PEMWE is higher with the Ir_0.5Ni_0.5O_x electrode than that with the sprayed electrode with commercial IrO₂ nanoparticles. This enhancement is attributed to the high electrochemical surface area caused by introducing Ni in IrO_x. Additionally, the performance of the directly coated Ir_0.5Ni_0.5O_x PEMWE is the highest reported in the literature.