Interfacial and Vacancy Engineering on 3D-Interlocked Anode Catalyst Layer for Achieving Ultralow Voltage in Anion Exchange Membrane Water Electrolyzer

Developing a high-efficiency and stable anode catalyst layer (CL) is crucial for promoting the practical applications of anion exchange membrane (AEM) water electrolyzers. Herein, a hierarchical nanosheet array composed of oxygen vacancy-enriched CoCrO_<i>x</i> nanosheets and dispersed FeNi layered double hydroxide (LDH) is proposed to regulate the electronic structure and increase the electrical conductivity for improving the intrinsic activity of the oxygen evolution reaction (OER). The CoCrO<i>_x</i>/NiFe LDH electrodes require an overpotential of 205 mV to achieve a current density of 100 mA cm^-2, and they exhibit long-term stability at 1000 mA cm^-2 over 7000 h. Notably, a breakthrough strategy is introduced in membrane electrode assembly (MEA) fabrication by transferring CoCrO_<i>x</i>/NiFe LDH to the surface of an AEM, forming a 3D-interlocked anode CL, significantly reducing the overall cell resistance and enhancing the liquid/gas mass transfer. In AEM water electrolysis, it exhibits an ultralow cell voltage of 1.55 V_cell to achieve a current density of 1.0 A cm^-2 in 1 M KOH, outperforming the state-of-the-art Pt/C//IrO₂. This work provides a valuable approach to designing high-efficiency electrocatalysts at the single-cell level for advanced alkaline water electrolysis technologies.