Ascorbic Acid-Assisted Morphology Tailoring of Crystalline Bi2WO6 for the Application in CO2 Photoreduction

Abstract

The photoreduction of CO2 into sustainable and green solar fuels is an intriguing way to simultaneously address environmental disasters and energy shortage. Bismuth tungstate (Bi2WO6) samples were synthesized in a single phase using ascorbic acid for photocatalytic CO2 reduction upon exposure to UV-vis irradiation. The best performing Bi2WO6 sample synthesized with 1.0 g ascorbic acid (BW1) showed a significant CO production rate which was almost 3.8 times greater than pristine Bi2WO6 (BW0). The activity of BW1 was improved by the exposed pore area (4.89 m(2)/g) which has increased by 53% due to surface modification, decreasing the reaction energy barrier for protonating activated CO2 to its intermediates with the help of H2O molecules. The photocatalytic CO2 reduction mechanism of the BW1 photocatalyst was investigated based on in situ diffuse reflection infrared spectroscopy results. The anticipated CO2 methanation routes were CO2* -> COOH* -> CO and CO2 -> HCO3- -> CH4. The BW1 sample exhibited a CO2 selectivity of 86% and the CO and CH4 formation rate of 70.88 mu mol g(-1) h(-1) and 27.87 mu mol g(-1) h(-1), respectively, owing to the modification of the BW1 pore surface area by the ascorbic acid. The study demonstrated that Bi2WO6 photocatalyst with diverse morphologies effectively enhances physisorption and chemisorption processes on catalytic surfaces, achieving high photocatalytic efficiency.