Enhancement of Photogenerated Charge Transport By TiO2 Modification of WO3/BiVO4 Core-Shell Heterojunction

Abstract

Photoelectrochemical (PEC) water oxidation is a promising approach to generate hydrogen using solar light. For the purpose, several candidate materials are considered that are mostly semiconductive materials including metal oxide. Among various metal oxides, WO3 has been regarded as a prospective resource because of their suitable band position, relatively higher photocorrosion resistance, and low cost. WO3 allows photogenerated electrons and provide easy electron pathway to current collector through the conduction band. Furthermore, BiVO4 deposition on WO3 can attract hole from WO3 that plays a key role for oxygen evolution reaction. Nevertheless, BiVO4 has a drawback to be solved with respect to stability. For this reason, blocking layers with high band gap energy are suggested to protect the unstability. In particular, TiO2 has not only high band gap energy but also chemical/physical stability. Moreover, TiO2 blocks solution-mediated recombination at surface of WO3/BiVO4 core-shell heterojunction, which helps to improve PEC efficiency.In the present work, we achieve facile approach to modify WO3/BiVO4 with TiO2 deposition. As a result, photoinduced current density is recorded as 0.59 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) under AM 1.5 G illumination. This value makes 78.8µL cm-2 of H2 evolution, which indicates almost 1.5 times higher than the WO3/BiVO4 core-shell heterojunction. Figure 1