Coordination-Mediated Heterogeneous Nucleation Enables Self-Supported Ni(OH)₂/NiFe-LDH Electrodes for AEM Water Electrolysis

Self-supported electrodes represent a promising anode architecture for anion exchange membrane water electrolyzers; however, their practical implementation is hindered by an insufficient understanding of their formation mechanisms and the consequently limited catalytic efficiency and stability. In this work, we developed a self-supported electrode comprising a composite catalyst of β-Ni(OH)₂ and NiFe layered double hydroxide (LDH), grown on nickel felt (denoted as Ni(OH)₂/NiFe-LDH/NFt) via a one-step hydrothermal process. We systematically investigated and clarified the role of NH₄F in governing the synthesis of self-supported Ni(OH)₂/NiFe-LDH/NFt. The coordination effect of F⁻ with Fe³⁺ and etching effect of NH₄⁺ on the surface oxide layer of nickel felt leads to favorable heterogeneous nucleation. Moreover, the etching effect provides an additional Ni source that favors the deposition of Ni(OH)₂ on NiFe-LDH. However, excess NH₄⁺ leads to the formation of Ni-based complex compounds in solution during the hydrothermal process and suppresses the deposition of Ni(OH)_2. When applying as the Ni(OH)₂/NiFe-LDH/NFt anode catalyst in practical anion exchange membrane water electrolysis, it requires only 1.81 V to deliver 1.0 A cm⁻² and exhibits outstanding durability, with no noticeable performance decay after 750 h of continuous operation at 0.5 A cm⁻².