Fundamental investigation of Ti doped WO3 photoanode and their influence on photoelectrochemical water splitting activity

Abstract

Herein, we utilize a facile hydrothermal method for the fabrication of Ti doped WO3 thin films on fluorine-doped tin oxide (FTO) for the efficient photoelectrochemical water splitting activity. Doping of Ti into WO3 is achieved during the condensation of a stable aqueous precursor solution of peroxopolytungstic acid (PTA) at 150°C. Characterization results show that, doping of Ti into WO3 suppresses the crystal growth along (200) facet and shift the 2 θ values to higher degree with a corresponding decrease in d spacing. Elemental mapping along with EDS measurements show the uniform distribution and approximate at% of Ti doped in WO3. The WO3 photoanode doped with 1.16 at% Ti displayed cathodic shift in onset potential with a maximum photocurrent density of 1.139mAcm−2 (at 1.23 vs. RHE), which is found to be 3.5 times higher than undoped WO3 (0.335mAcm−2) under simulated 1.5 AM sunlight. Spectroscopic and impedance measurements show that, the substitution of W with Ti, widens the band gap and shifts the conduction band edge (CBE) and flat band potential upwards to higher energies keeping the relative energy difference between valence band edge (VBE) and Fermi level constant. Such a change in band edge positions of WO3 after Ti doping, shifts the conduction band minimum (CBM) towards the H+/H2 redox potential. The study presented herein demonstrates a simple but systematic and efficient approach for the design and fabrication of band edge-tailored WO3 photoanodes via Ti doping for the efficient photoelectrochemical water splitting.