Systematic Construction of Type‐II BiVO ₄ /CoWO ₄ p–n Heterojunction Photoanodes for Efficient Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting is widely regarded as a sustainable route for hydrogen generation, in which efficient water oxidation requires highly active photoanodes. Although bismuth vanadate (BiVO 4 ) is a promising visible‐light‐responsive photoanode because of its suitable bandgap, its PEC performance is still largely constrained by severe bulk/surface charge recombination and sluggish oxygen‐evolution kinetics. In this work, p‐type CoWO 4 nanoparticles were introduced onto n‐type BiVO 4 to build a type‐II p–n heterojunction. Intimate interfacial contact generates a built‐in electric field that, together with the staggered band alignment, drives the directional separation and migration of photogenerated carriers. Meanwhile, CoWO 4 offers abundant catalytic sites and lowers the interfacial reaction resistance, thereby accelerating surface water oxidation. The optimized BiVO 4 /CoWO 4 photoanode reaches a photocurrent density of 4.58 mA cm −2 at 1.23 V versus reversible hydrogen electrode (RHE), representing a 3.6‐fold improvement over pristine BiVO 4 . A series of analyses and characterizations further confirm that the heterojunction effectively suppresses charge recombination, extends carrier lifetime, and promotes charge injection as well as interfacial water‐oxidation kinetics, leading to improved PEC performance. Overall, this study demonstrates an effective heterojunction‐engineering strategy for improving the PEC performance of BiVO 4 ‐based photoanodes.