Boosting Acidic Water Oxidation on Hematite Photoanodes with Synergistic Effects of Ce‐Doped Co3O4 Nanoparticles

Abstract Photoelectrochemical (PEC) water splitting is pivotal for addressing the clean and renewable energy demands. However, developing low‐cost, efficient, and robust non‐precious metal catalysts for the acidic oxygen evolution reaction (OER) remains a significant challenge. In this study, we introduced Ce to modulate the electronic structure of Co 3 O 4 , enhancing the stability of Co 3 O 4 without compromising its activity. Ce‐doped Co 3 O 4 nanoparticles were electrodeposited onto Ti‐doped hematite surfaces (Ce : Co 3 O 4 /Fe 2 O 3 ), significantly enhancing the PEC performance for water splitting under acidic conditions. These catalysts achieved high photocurrent densities and exhibited prolonged stability. Functioning as p‐type semiconductors, the Ce : Co 3 O 4 nanoparticles not only boosted light absorption but also formed a p‐n heterojunction with the Ti‐doped hematite. This heterojunction generated a built‐in electric field that facilitated the separation and transfer of photogenerated carriers, thereby improving charge separation efficiency. Additionally, these nanoparticles expanded the active surface area of hematite and served as a co‐catalyst, markedly accelerating the OER kinetics. The Ce : Co 3 O 4 /Fe 2 O 3 photoanode achieved an impressive photocurrent density of 1.08 mA cm −2 at 1.23 V RHE in acidic media, demonstrating its enhanced activity and stability.