Fe(III)‐Mediated Formation of Cu Nanoinclusions and Local Heterojunctions in CuWO4 Photoanodes

Enhancing the photoelectrochemical (PEC) performance of CuWO4 photoan-odes has typically relied on doping or co-catalyst strategies to improve chargecarrier dynamics. In this work, an alternative approach is presented in whichFe(III) acts as a self-assembly mediator during hydrothermal synthesis, en-abling the formation of a core–shell heterostructure composed of a crystallineCuWO4 core, a partially amorphous CuO/WO 3 shell, and embedded metallicCu nanoinclusions. Rather than functioning as a dopant or co-catalyst, Fe(III)is completely removed during post-synthetic treatment, mediating a redox-guided phase reorganization without being incorporated into the final material.This architecture establishes local heterojunctions that facilitate charge sepa-ration, suppress recombination, and enhance oxygen evolution reaction (OER)activity. A relative increase of ≈30-fold in photocurrent is observed compared topristine CuWO4 , as confirmed by structural, spectroscopic, and electrochemi-cal analyses. While absolute photocurrents remain modest, this enhancementreflects intrinsic modifications in charge transport and recombinationbehavior driven by Fe(III)-mediated structural reorganization. Complementaryphotocatalytic dye degradation experiments reveal that Fe-activated particlesact as highly efficient ROS-generating catalysts in suspension, demonstratingfunctionality beyond thin-film devices. These findings offer a new paradigm foroxide photoanode design, leveraging Fe(III)-induced self-assembly to engineermultifunctional heterostructures without relying on conventional doping.