Anion Engineering of Nickel‐Iron (NiFe)‐Based Electrocatalysts for Enhanced Water Electrolysis

Developing highly efficient water electrolysis technologies is pivotal to the transition toward a sustainable hydrogen economy, yet the sluggish kinetics of the oxygen evolution reaction (OER) remain a critical bottleneck. While nickel–iron (NiFe)‐based materials are among the most active benchmark nonprecious electrocatalysts, the important regulatory roles of anions are often overshadowed by cation‐focused research. This review provides a comprehensive overview of “anion engineering” strategies for NiFe‐based catalysts. The profound impacts of anions are elucidated, including their functions as intrinsic lattice components and interlayer guests that modulate electronic structures and mass transport, as well as their roles as dynamic surface regulators. Particular attention is devoted to mechanisms that mitigate chloride‐induced corrosion and enhance selectivity during seawater electrolysis. Furthermore, the critical capabilities of anions as synthesis‐directing agents for morphology control and defect inducers for accelerating active phase reconstruction are summarized. Coupled with insights from advanced in situ characterizations and theoretical calculations that unveil structure‐activity relationships, perspectives on future challenges are discussed to guide the rational design of robust electrocatalysts for industrial‐scale applications.