Origin of the Improved Photoelectrochemical and Photocatalytic Activity in a ZnO-TiO<sub>2</sub> Nanohybrid Revealed by Experimental and Density Functional Theory Studies
Abinash Das, Dongyu Liu, Yifan Wu, Bayan Amer Abzakh, R. Madhumitha, M. Preethi, Elena A. Kazakova, Andrey S. Vasenko, Oleg V. Prezhdo
Abstract
High Resolution Image Download MS PowerPoint Slide Heterojunctions of metal oxides have attracted a great deal of attention as photo (electro) catalysts owing to their excellent photoactivity. While multiple fundamental studies have been dedicated to heteroaggregation, self-assembly of oppositely charged particles to obtain heterojunctions for energy applications has been underexplored. Herein, we report the synthesis of ZnO-TiO 2 heterojunctions using the electrostatic self-assembly approach. The synthesized ZnO-TiO 2 heterojunctions were characterized by using multiple experimental techniques. Density functional theory calculations were conducted to establish the heterojunction formation mechanism and electronic properties. The ZnO-TiO 2 nanohybrid was tested for the photodegradation of rhodamine B dye and water splitting applications. The photocatalytic performance of the ZnO-TiO 2 nanohybrid is 3.5 times higher than that of bare ZnO. In addition, the heterostructure exhibited an excellent photocurrent density of 2.4 mA cm –2 at a low onset potential during photoelectrochemical oxygen evolution. The performance improvements are attributed to the formation of the type II heterojunction between ZnO and TiO 2, which suppresses carrier recombination and enhances carrier transport, boosting the catalytic activity.