Increasing visible light water splitting efficiency through synthesis route and charge separation in measoporous g-C3N4 decorated with WO3 nanoparticles

Separation of photogenerated charge carriers and lowering the band gap are essential in designing an efficient photocatalyst in visible light setup. Separation of charge carriers can be achieved via incorporation of a metal-oxide catalyst on the surface of a semiconductor. In this paper we report synthesis of WO3/g-C3N4 nanocomposite material starting with a mesoporous MCM-41 as a template to produce high surface area g-C3N4 with subsequent WO3 decoration. Various compositions were prepared (3-12% WO3 decoration) and tested for their photocatalytic efficiency utilizing water splitting reaction. Comparisons to the efficiencies of pristine g-C3N4 and WO3 reveal superior activity of the nanocomposites. 9% content of WO3 was determined to be the optimum concentration of the additive and showed 27.5 and 55 times more efficiency than that of WO3 and g-C3N4. Addition of glycerol as a positive hole scavenger helps to increase the efficiency of the catalytic system. The nanocomposite photocatalyst also showed stability upon reuse and remained efficient even after five runs. Major parameters affecting the photocatalytic activity of the WO3/g-C3N4 nanocomposite include its ability of charge separation during the photocatalytic process, its mesoporous structure, a band gap width in the visible region and its high surface area.