Advanced Nickel-Based Gas Diffusion Anode for Zero-Gap Anion-Exchange Membrane Water Electrolyzers.

Electrolytic hydrogen production using abundant water and renewable electricity is a key step toward achieving a carbon-neutral economy. Anion-exchange membrane water electrolyzers (AEMWE) present an opportunity to enhance sustainability and reduce the costs of green hydrogen technology. This study focuses on reducing electrical losses in the AEMWE by designing an improved anode catalyst layer. The approach involves modifying nickel foam by using a microporous nickel ink. This modification not only smooths the nickel foam to prevent membrane punctures during compression assembly but also enhances the utilization of the mesoporous NiO (mesoNiO) catalyst in the anode process, namely, the oxygen evolution reaction (OER). The anode leverages a mechanism where both the mesoNiO catalyst and the nickel powder layer participate in the OER, hosting a NiOOH intermediate formed through surface oxidation. By optimization of the mass loading, the design achieves a balance between smooth membrane-electrode contact, reduced kinetic losses during the OER, and efficient ionic transport. As a result, the optimized AEMWE reaches a competitive current density of 2.6 A cm at a cell voltage of 2 V, comparable to the performance of state-of-the-art proton-exchange membrane water electrolyzers. These findings highlight that fluorocarbon membrane-free, zero-gap water electrolyzers with platinum-free anodes can deliver significant advancements in green hydrogen technology. This promising performance encourages further research toward catalyst-free water electrolyzers as the next step in sustainable hydrogen production.