Boosting photocurrent density of 1D TiO2 based photoanodes by bismuth vanadium oxide enhancement for photoelectrochemical cell application

Abstract

A photoelectrochemical cell (PEC) is a device that can convert light energy into hydrogen fuel. In the present work, a 1D TiO2 based photoanode was enhanced by BiVO4 (BVO). All TiO2 and BVO/TiO2 photoanodes were fabricated by a hydrothermal method. Structural and surface morphology of the thin films were characterized by various spectroscopies. The 1D TiO2 and BVO/TiO2 nanorods were well aligned perpendicular to the fluorine doped tin oxide (FTO) substrate. X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS) revealed BVO formation on the TiO2 surface, which was in agreement with the energy dispersive X-ray spectroscopy (EDS) and high resolution transmission electron microscopy (HRTEM) results. The bandgap of the TiO2 photoanode was decreased due to the BVO enhancement. According to UV–visible spectroscopy and the valence band binding energy from XPS, the estimated bandgap of BVO/TiO2 was 2.8 eV, while pure TiO2 was 3.1 eV. Based on this result, the PEC comprised of a BVO/TiO2 photoanode can harvest visible light. Electrochemical impedance spectroscopy (EIS) was performed to reveal the underlying physical properties when the PEC was operated. Upon illumination with a solar simulator, most of the PECs comprised of a BVO/TiO2 photoanode exhibited greater performance than the PECs comprised of a pristine TiO2 photoanode. The significant increase in performance was due to the light absorption extension to the visible region and the BVO anchoring, which leads to a low internal charge carrier resistance of the TiO2 based photoanode.