Ferro-photocatalytic Enhancement of Photoelectrochemical Water Splitting Using the WO3/BiFeO3 Heterojunction

Storing sunlight energy in chemical bonds by water splitting or carbon dioxide reduction grabs a vast majority of interest in recent years. The race for improving the photoelectrochemical (PEC) water splitting performance has been raised mostly by investigating heterojunction semiconductors. In this article, the WO 3 /BiFeO 3 n–p heterojunction device is deposited via sol–gel spin coating, and the PEC water splitting of the device is compared to those of each counterpart. The monoclinic-phase WO 3 film without any impurity with granular morphology and a band gap of 3.00 eV is synthesized. The BiFeO 3 film is also synthesized through three different methods to reach phase purity and a band gap of 2.15 eV. PEC measurements demonstrate that the WO 3 /BiFeO 3 heterojunction reveals an onset potential of 0.25 V and a photocurrent density of 35.2 mA/cm 2 at 2 V versus Ag/AgCl, which is far better than those of individual components. These properties result from not only built-in potential at the interface of the n–p heterojunction but also from abnormal ferroelectric-assisted photocatalytic behavior of BiFeO 3 on the surface and from porous morphology of the film. Moreover, the WO 3 /BiFeO 3 represents long-lasting photostability. The n–p heterojunction properly enhances the carrier lifetime by appropriate band alignment formation, confirmed by photoluminescence spectroscopy and electrochemical spectroscopy.