Epitaxial growth of Heteropolyacid-WO3 vertical heterostructures with photo-induced charge modulation for enhanced water oxidation

Abstract

The charge separation and transfer are critical steps during the photoelectrochemical processes. In this paper, we focus on the interfacial properties within the heteropolyacid (denoted as PW12) modified WO3 heterojunction film synthesized by an epitaxial growth method. The characterizations show that heteropolyacid is formed on the surface of WO3 plates with less interfacial defects between PW12 and WO3. The PW12/WO3 photoanodes synthesized via the in-situ method display a photocurrent density of 0.65 mA/cm2 at 1.23 V vs. RHE, which exhibits 1.6 times as much as the bare WO3. And the composite achieves the maximum value of 1.52 mA/cm2 at 1.8 V vs. RHE, while those of PW12/WO3 films prepared by a dip-coating method and pristine WO3 films are just 1.10 and 0.85 mA/cm2. The improvements in PEC performances of PW12/WO3 photoanodes (in-situ) were attributed to the higher electron transmission rate and longer electron lifetime resulted from the less interfacial defects. Moreover, the PW12/WO3 film was treated with TiCl4 solution to form a TiO2/PW12/WO3 ternary heterojunction, which exhibits a higher photocurrent density of 1.89 mA/cm2. The current research has proposed a new perspective and method for the design of highly efficient heterojunction photoelectrodes and inorganic synthesis.