Design, Mechanisms, and Advances in Two‐Dimensional van der Waals Heterostructures for Photocatalytic Water Splitting

ABSTRACT Photocatalytic water splitting is a promising method for producing clean hydrogen. Although traditional photocatalysts have been widely studied, their efficiency is hindered by limited light absorption, rapid charge recombination, and slow surface reactions. The construction of heterojunctions—predominantly two‐dimensional van der Waals heterostructures—has become a vital strategy to overcome these limitations. This review systematically classifies heterojunctions by construction method and band alignment, and analyzes the three fundamental processes in photocatalysis: light absorption, charge separation/transport, and surface reactions. Furthermore, various performance enhancement strategies are explored, encompassing external stimuli such as electric fields, ferroelectric/piezoelectric effects, and strain, as well as static structural designs including layer‐number control, interlayer‐spacing adjustment, twist‐angle tuning, and dual‐Z/S‐scheme heterojunction configurations. This work thus provides theoretical insights and practical pathways for developing highly efficient two‐dimensional van der Waals heterojunction photocatalysts.