Antimony‐Incorporated Vertically Aligned Cu ₂ O Photoelectrodes for Efficient Solar‐Driven Photoelectrochemical Water Purification

The growing demand for efficient and sustainable water purification technologies has intensified because of the increasing outflow of toxic and nonbiodegradable organic pollutants from industrial activities. Conventional treatment methods often require high energy input or chemical additives, leading to high costs and environmental concerns. Photoelectrochemical (PEC) systems, which utilize solar energy to drive pollutant degradation, offer promising alternatives. In this study, we demonstrate the fabrication of Sb‐incorporated Cu 2 O photocathodes via a simple electrochemical deposition method to enhance PEC water purification performance. Cu 2 O is a favorable p‐type semiconductor with strong visible‐light absorption and an earth‐abundant composition. However, its application is limited by poor crystallinity and randomly distributed grain boundaries that restrict charge transport. Incorporation of antimony promoted preferential (111) crystal orientation of Cu 2 O, increased nucleation density, and the formation of vertical grain boundaries perpendicular to the substrate. The photocathode with 0.75 mol% Sb incorporation exhibited outstanding PEC activity, reaching a photocurrent density of ∼2.8 mA cm −2 at −0.35 V Ag/AgCl under 1‐sun illumination. This enabled the complete degradation of methyl orange within 90 min without any overlayers or posttreatment, while maintaining excellent stability. This study offers a scalable, low‐cost strategy for constructing high‐performance Cu 2 O‐based photocathodes for solar‐driven environmental remediation.