Enhanced photocatalytic activity of Bi₂WO₆ with PVP addition for CO₂ reduction into ethanol under visible light

The conversion of CO₂ into new carbon-based products, such as fuels and chemicals, is an attractive and promising means of mitigating global energy needs and minimizing environmental damage. Although bismuth tungstate (Bi₂WO₆) as a photocatalyst can promote CO₂ photoreduction, a systematic study for the development of a low-cost and efficient catalyst is needed. Thus, Bi₂WO₆ with different morphologies was successfully synthesized using the hydrothermal method. An experimental design was applied to investigate the effect of synthesis time and PVP (polyvinylpyrrolidone) concentration on catalyst photocatalytic activity. Crystal structures, morphologies, optical absorption, and surface charges of the catalysts were characterized by X-ray diffraction, scanning electron microscope, UV-vis diffuse-reflection spectroscopy, nitrogen adsorption, and zeta potential. All samples exhibited good performance for the photoreduction of CO₂ into ethanol, and both time and PVP concentration were significant in the ethanol yield. Changes in synthesis conditions induced differences in catalyst characteristics, such as morphology, crystallinity, and, predominantly, surface area. Furthermore, PVP addition improved photocatalytic efficiency by up to 258% compared with results without the surfactant. The best sample, W-8h-10%, presented a flower-like morphology and ethanol yield of 68.9 μmol g^-1 h^-1.