Visible-light CO2 photocatalytic reduction performance of ball-flower-like Bi2WO6 synthesized without organic precursor: Effect of post-calcination and water vapor

Abstract

• Photocatalytic CO 2 reduction on non-organic synthesized PB-Bi 2 WO 6 was investigated. • CO was detected as the major product. • Increased amount of CO was yielded in the condition with little water vapor. • Photocatalytic performance was enhanced with Bi 2 WO 6 after 550 °C post-annealing. • Renewing the catalysts used in CO 2 photoreduction by water washing was achieved. Nanoplates-composed ball-flower-like Bi 2 WO 6 (PB-Bi 2 WO 6 ) was synthesized by a hydrothermal method without any organic precursor and its performance in photocatalytic reduction of CO 2 was investigated in a continuous-flow reaction system under visible light irradiation (420 nm < λ < 620 nm). CO was detected as the main product of this photocatalytic process and H 2 O was found to suppress the conversion of CO 2 to CO due to its competitive absorption with CO 2 on the medium strength basic sites of Bi 2 WO 6 . PB-Bi 2 WO 6 annealed at 550 °C showed superior CO yield in the condition with little water vapor. It might be attributed to the enhanced crystallinity, significantly decreased recombination rate of photo-generated electrons and holes and more stable basic sites for strengthened CO 2 adsorption, according to characterization results by XRD, SEM, UV–vis SRS, PL and CO 2 -TPD. However, comparing with PB-Bi 2 WO 6 , the negative effect of H 2 O was even more prominent on the annealed sample because of the reduced surface area. Yield decrease was observed during the irradiation time due to the adsorption of intermediates generated but fortunately washing with deionized water was found to be an effective way to renew the catalyst.