Tuning the Electronic Structure of Monoclinic Tungsten Oxide Nanoblocks by Indium Doping for Boosted Photoelectrochemical Performance.

Photoelectrochemical (PEC) water oxidation, a desirable strategy to meet future energy demands, has several bottle-necks to resolve. One of the prominent issues is the availability of charge carriers at the surface reaction site to promote water oxidation. Of the several approaches, metal dopants to enhance the carrier density of the semiconductors, is an important one. In this work, we have studied the effect of In-doping on monoclinic WO3 nanoblocks, growing vertically over fluorine-doped tin oxide (FTO) without the aid of any seed layer. X-ray photoelectron spectroscopy (XPS) data reveals that In3+ ions are partially occupying the W6+ ions in In-doped WO3 photoanode. In3+ ions are offering better performance by adding additional charge carriers for amplifying the expression of the number of carriers. The maximum current density value of 2.18 mA/cm2 has been provided by the optimized In-doped WO3 photoanode with 3 wt% indium doping at 1.23 V vs. RHE, which is ∼3 times higher than that of undoped monoclinic WO3 photoanode. Mott-Schottky (MS) analysis reveals charge carrier density (ND ) for In-doped WO3 photoanode has been enhanced by a factor of 3. An average Faradic yield of ∼90 percent has been achieved which can serve as a model system using In3+ as a dopant for an inexpensive and attractive method for enhanced WO3 based PEC water oxidation.