Constructing ZnO/ZnCr2O4@TiO2-NTA Nanocomposite for Photovoltaic Conversion and Photocatalytic Hydrogen Evolution

Nanocomposites based on TiO2 nanotube arrays (TiO2-NTA) have received increasing attention for photoconversion and photocatalytic reactions. Here, TiO2-NTA were prepared by an anodic oxidation process. ZnO and ZnCr2O4 nanoparticles were further anchored on the surface of the pre-synthesized TiO2-NTA to form a ternary ZnO/ZnCr2O4@TiO2-NTA (Zn-Cr-O@TiO2-NTA) nanocomposite by an electrochemical reduction–oxidation strategy. Compared to bare TiO2-NTA, the Zn-Cr-O@TiO2-NTA nanocomposite shows remarkably higher photovoltaic conversion efficiency (nine times greater) under visible light irradiation, and photocatalytic H2 evolution activity (2.8 times greater) under simulated sunlight irradiation, respectively. The construction of ternary nanocomposite is beneficial to enhancing the absorption of simulated sunlight irradiation. Moreover, the Type-II semiconductor heterojunction facilitates separation of electron–hole pairs and interfacial charge transport. As a result, improvement of photoconversion efficiency has been obtained. This work may have fundamental importance to designing complex and efficient photoelectrodes for energy-harvesting applications, including photovoltaic solar cells and water splitting.