Built‐in Electric Field‐Driven Electrocatalysis for Water Splitting: Toward Highly Efficient Hydrogen Production

Against the backdrop of global “dual‐carbon” goals and the rapid expansion of the new energy industry, water electrolysis for hydrogen production has emerged as a pivotal route for transforming the global energy structure. However, its industrial‐scale deployment is hindered by sluggish electrocatalytic reaction kinetics, highlighting the urgent need for high‐performance electrocatalysts to reduce energy barriers. Built‐in electric field (BIEF) engineering has attracted increasing attention because it can accelerate charge transport, regulate the adsorption/desorption behavior of reaction intermediates, enhance intrinsic catalytic activity, and tailor the local reaction microenvironment. Unlike existing reviews that mainly focused on general heterostructure design or charge‐transfer regulation in electrocatalysis, this review provides a systematic overview of BIEF engineering for water electrolysis electrocatalysts. Specifically, the fundamental concepts, formation mechanisms, and intrinsic advantages of BIEFs are summarized, followed by representative modulation strategies, including alloying, heteroatom doping, defect engineering, and heterojunction engineering. Moreover, practical applications of BIEF engineering in n–n, p–n, p–p, and Mott–Schottky heterojunction electrocatalysts are highlighted, establishing the relationship between BIEF construction, interfacial electronic regulation, and electrocatalytic performance enhancement. Finally, current challenges and future perspectives are discussed to guide the rational design of advanced BIEF‐driven electrocatalysts.