Synergistic gradient distribution of IrO2/TiNX ratio and ionomer content reduces the internal voltage loss of the anode catalytic layer in PEM water electrolysis

The design of the anode catalyst layer (ACL) is crucial to the performance and stability of PEM electrolyzers. In this work, the ACL was designed into three sublayers, each different in ionomer content and IrO2/TiNX ratio. The high ionomer content of the subset layer will reduce the utilization of the active sites of the catalytic layer, but based on the improvement of the kinetic performance and proton conductivity near the membrane interface, increased mass transport can be achieved. A higher Ir loading near the gas diffusion layer (PTL) and less Ir loading near the membrane interface can improve cell performance, especially at high current densities. The abundance of bubbles produced by oxygen evolution reduces the three-phase reaction boundary, which results in a low utilization rate of the catalyst close to the membrane. In contrast, more Ir in the catalytic layer near the PTL interface can alleviate the effect of mass transfer performance and improve the performance. The internal voltage loss of the optimal MEA is 21.5% lower than the conventional single-layer catalyst layer MEA at 3 A cm‐2.