The improvement of photocatalytic activity of BiVO4 modified with Co(OH)2 nanoflake arrays for photocatalytic and photo-electrocatalytic desulfurization

Abstract

Various and economical pure BiVO₄ and Co(OH)₂ nanoflake deposited BiVO₄ photocatalysts have been prepared using the electrodeposition technique. Improved photocurrent density of 64 µA/cm² at 1.0 V vs. Ag/AgCl was shown by Co(OH)₂-BiVO₄-150 photoanode (BiVO₄ after 150 s of cobalt electrodeposition), which is about 8 times higher compared with BiVO₄ photoanode. The catalysts prepared have also been used in the photocatalytic oxidation of dibenzothiophene (DBT), which is applied to stimulate fluid catalytic cracking for gasoline production in n-heptane solution. The corresponding parameters in the optimization of oxidative desulfurization of DBT were reaction time, temperature, solvent, DBT concentration and electrical bias voltage. The highest DBT desulfurization efficiency was shown by Co(OH)₂-BiVO₄-150. Based on the mechanism of photocatalytic oxidation, the superoxide and hydroxyl radicals played major parts in DBT degradation. Co(OH)₂-BiVO₄-150 photoanode showed better photo-electrocatalytic degradation efficiency, reaching a high 78.3% DBT removal even during the reaction time, in comparison with photocatalysis and electrocatalysis. The photocatalytic degradation system containing Co(OH)₂-BiVO₄-150 may be recycled six times without any important reduction of photocatalytic activity. This procedure introduces a simple and sustainable approach for the modification of BiVO₄ to improve its photoelectrochemical and photocatalytic activity.