Selenium-modified In2O3 photoanode: oxygen vacancy-mediated “defect capture-interface transport” and extended light absorption for efficient photoelectrochemical water splitting

Abstract

Efficient solar hydrogen production through photoelectrochemical (PEC) water splitting requires overcoming two key challenges: augmenting the separation of photogenerated carriers and boosting light absorption efficiency. In this work, an In₂O_3−x@In₂Se₃ photoanode was prepared through a selenization reaction. The introduction of selenium (Se) dynamically induces an increased concentration of oxygen vacancies (O_V) due to the strong oxygen affinity. These O_V act as an intermediate state, allowing a “defect capture-interface transport” mechanism that facilitates the storage and transfer of photogenerated carriers in PEC water splitting, and improves the photogenerated carrier separation efficiency. Meanwhile, the In₂O_3−x@In₂Se₃ heterojunction formed upon selenization causes band bending, narrowing the bandgap width and increasing the light absorption range, significantly improving the photon utilization of the In₂O_3−x@In₂Se₃ photoanode. Therefore, both the improved efficiency of photogenerated carrier separation and light absorption capacity contribute to the enhanced PEC water splitting of the In₂O_3−x@In₂Se₃ photoanode. In the PEC water oxidation reaction, the In₂O_3−x@In₂Se₃ photoanode exhibits a photocurrent density of 2.68 mA cm⁻² at 1.23 V vs. RHE without cocatalysts, which is 22.25 times higher than that of the In₂O_3−x photoanode (0.12 mA cm⁻²). This study provides new strategies for the design of a metal oxide photoanode with high photogenerated carrier separation efficiency and light absorption capacity.