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 H-2 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.