An Ionomer-Free Gapless Catalyst-Bridging Membrane Electrode Assembly for High-Performance Pure Water-Fed Anion Exchange Membrane Electrolyzer.

Anion exchange membrane water electrolyzers (AEMWEs) are promising for hydrogen production due to low cost and high product purity. However, the performance of AEMWEs fed by pure water is unsatisfactory because of high ohmic resistance and sluggish reaction kinetics in the membrane electrode assembly (MEA). Here, an efficient ionomer-free gapless catalyst-bridging MEA (GCB-MEA) is developed for high-performance AEMWEs by confined directional deposition of the catalyst layer. The ionomer-free catalyst layer bridges the anion exchange membrane and the gas diffusion layer, creating robust interfaces at its both sides. Compared to conventional MEAs, the GCB-MEA exhibits more active sites, lower contact resistance, faster mass transfer kinetics, and stronger interfacial binding. The GCB-MEA-based AEMWE shows an energy conversion efficiency of 85.7% at 1 A cm-2 and a voltage degradation rate of 65 µV h-1 at 0.5 A cm-2 after 1 000 h, being the lowest reported to date for pure water-fed AEMWEs. Moreover, the electrolyzer exhibits stable responses under the fluctuating solar energy supply conditions. This work provides an efficient strategy to prepare MEAs for high-performance hydrogen production, especially under pure water condition.