Decoration of BiVO4/ZnO Photoanodes with Fe‐ZIF‐8 to Simultaneously Enhance Charge Separation and Hole Transportation for Efficient Solar Water Splitting

Abstract Facilitating the separation and transport efficiency of photogenerated electron–hole pairs is a key factor in realizing efficient photoelectrochemical (PEC) reactions. Herein, a novel metal–organic framework (MOF)‐derived cocatalyst of iron‐substituted ZIF‐8 (Fe‐ZIF‐8) is fabricated, which is attached to a BiVO 4 /ZnO (BZ) photoanode. The formation of Fe‐ZIF‐8 is based on ZnO nanoparticles in BZ (BiVO 4 /ZnO : Fe‐ZIF‐8, BZZF) through a ligand‐exchange method. Fe‐ZIF‐8 can extract holes from BZ, prolong the lifetime of charge carriers at the photoanode/electrolyte interface, and enhance the built‐in electric field to drive the separation of photogenerated charge carriers. In addition, more active sites and surface defect states are induced by the decoration with Fe‐ZIF‐8. As a result, the prepared BZZF photoanode achieves enhanced separation and transport efficiency under AM 1.5G solar light illumination (100 mW cm −2 ). The PEC performance achieves 4.14 mA cm −2 with a maximum applied bias photon‐to‐current efficiency of 1.10 % at 0.71 V vs . RHE, which is superior to that of BiVO 4 . This work suggests that the semiconductor combined with MOF‐derived materials is a rational design to facilitate charge separation and increase hole transport efficiency simultaneously to advance PEC water splitting systems.