Sacrificial Agents Steering the Formation of Active and Stable β-Ni(Fe)OOH on NiFe Layered Double Hydroxide for...

The sluggish kinetics of the oxygen evolution reaction (OER) greatly hinder alkaline water electrolysis. NiFe layered double hydroxide (NiFe LDH) is a promising OER pre-catalyst that anodically reconstructs into the active Ni(Fe)OOH species. However, slow surface reconstruction kinetics and Ni overoxidation toward the γ-Ni(Fe)OOH phase severely compromise activity and stability. Herein, we deposit amorphous ZnS onto NiFe LDH (denoted as ZS/LDH) as a sacrificial agent via plasma magnetron sputtering. During electrochemical activation, Lewis acidic Zn²⁺ effectively enriches OH^-, thereby promoting the surface reconstruction of NiFe LDH. The S^2- undergoes preferential oxidation to SO₄ ^2-, consuming anodic charge and suppressing Ni overoxidation, directing the formation of a highly active and stable β-Ni(Fe)OOH phase. Activated ZS/LDH (A-ZS/LDH) exhibits enhanced lattice oxygen activity, achieving 207 mV at 10 mA cm^-2 and 1200 h stability at 800 mA cm^-2. In an anion exchange membrane water electrolyzer, the A-ZS/LDH-based cell requires only 2.05 V to reach 1000 mA cm^-2 at 60 °C and operates stably for over 2000 h. Even under high-frequency start-stop cycles, it sustains at least 700 h without decay. This work provides a simple sacrificial agent strategy to steer NiFe LDH reconstruction toward the desirable β phase for durable industrial water electrolysis.