Fabrication and characterization of metal ion doped BIVO4-TIO2 photoanode for H2 evolution under visible light irradiation
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Date
2016-06
Authors
Teng, Jin Wen
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Abstract
Producing H2 using water splitting method is an attractive way to tackle energy crisis. BiVO4 is recently known as one of the most promising photoanode material for water splitting application. However, it suffers from high electron-hole recombination and poor charge transport. Therefore, BiVO4/TiO2 heterocomposite photoanode has been successfully fabricated using a simple, solution based metal-organic decomposition (MOD) method to overcome the conventional drawbacks of BiVO4. In this work, the properties of BiVO4/TiO2 with different molar ratios were studied. The current density was increased by ~10 times using BiVO4/TiO2 with 3:1 molar ratio with respect to bare BiVO4 under 1000 W m-2 illumination. The enhancement in current density is due to the better charge separation across the junction. However, the current density were still in the range of 0.27 - 0.54 mA cm-2 due to poor charge transport. In order to increase the charge transfer, Mo and W were incorporated into BiVO4/TiO2 heterocomposite system. Different concentrations (2 - 6 %) of the dopants were investigated. Mo did not show significant improvement in current density due to the particles size which increase the grain boundaries that act as recombination sites. 2% of W were found to give significant effect in photoelectrochemical performance, showing ~2 folds enhancement in current density compared to BiVO4/TiO2 3:1 system. W showed better performance due to higher tendency to donate electrons to the lattice. It is recommended that 2 % of W in BiVO4/TiO2 3:1