Interfacial construction of P25/Bi₂WO₆ composites for selective CO₂ photoreduction to CO in gas–solid reactions

Abstract

Proposed mechanism of CO2 photoreduction of the P25/Bi2WO6 nanocomposites.

Hierarchical Hollow TiO2@Bi2WO6 with Light-Driven Excited Bi(3–x)+ Sites for Efficient Photothermal Catalytic CO2 Reduction

“…With regard to H-TiO 2 , the absorption peaks in the range from 850 to 433 cm −1 are ascribed to the vibration of the Ti−O−Ti bonds of H-TiO 2 . 29 With regard to the TiO 2 @Bi 2 WO 6 composite material, those adsorption peaks mentioned above in pure Bi 2 WO 6 and H-TiO 2 can be observed, which proves the successful preparation of a composite material. As shown in the Raman spectra (Figure S7), these signals located at 157, 306, 791, and 828 cm −1 are assigned to Bi 2 WO 6 (signals at 157 cm −1 for WO 6 6−x , 306 cm −1 for the vibrational stretching mode between Bi 3+ and WO 6 6− , and 791 and 828 cm −1 for the vibrational stretching mode of the W−O bond).…”

“…When visible light (λ > 400 nm) is introduced into the reaction system, one can see that the peak intensities of m -CO 3 2– (1040, 1090, and 1490 cm –1 ) and b-CO 3 2– (1580 cm –1 ) are significantly weakened, which indicates the catalytic transformation of absorbed carbonate species into intermediates or products. Meanwhile, carboxylic acid species (COO – ; 1220, 1350, and 1720 cm –1 ) and formic acid species (COOH – ; 1560 cm –1 ) are also detected, and the intensity of these new peaks increases with illumination time. ,, The infrared absorption peaks of COO – and COOH – have been considered as the main active intermediates for the reduction of CO 2 to CO previously. , These results indicate the transformation of adsorbed carbonate species into CO via an important intermediate of COO – and COOH – . One peak appears at 1130 cm –1 , assigned to HCO 3 – , which might be a product from the reaction between CO 3 2– and adsorbed water on the surface of the catalyst during the photocatalytic process .…”

“…In the Raman spectrum of anatase H-TiO 2 , signals at 143, 396, 515, and 638 cm −1 are attributed to the vibration of the O−Ti−O bonds. 29 The Raman spectrum of TiO 2 @Bi 2 WO 6 shows characteristic signals of both pure Bi 2 WO 6 and H-TiO 2 . These results clearly demonstrate the successful preparation of a composition consisting of H-TiO 2 and Bi 2 WO 6 .…”

“…As shown in the Raman spectra (Figure S7), these signals located at 157, 306, 791, and 828 cm –1 are assigned to Bi 2 WO 6 (signals at 157 cm –1 for WO 6 6– x , 306 cm –1 for the vibrational stretching mode between Bi 3+ and WO 6 6– , and 791 and 828 cm –1 for the vibrational stretching mode of the W–O bond). In the Raman spectrum of anatase H-TiO 2 , signals at 143, 396, 515, and 638 cm –1 are attributed to the vibration of the O–Ti–O bonds . The Raman spectrum of TiO 2 @Bi 2 WO 6 shows characteristic signals of both pure Bi 2 WO 6 and H-TiO 2 .…”

“…In situ DRIFTS was further carried out to identify the crucial carbon-based intermediates and possible reaction pathway of CO 2 reduction over the TiO 2 @Bi 2 WO 6 catalyst. , As shown in Figure d, CO 2 and H 2 are introduced under dark conditions. The absorption peaks of monodentate carbonate species ( m -CO 3 2– ; 1040, 1090, 1280, and 1490 cm –1 ) and bidentate carbonate species (b-CO 3 2– ; 1520 and 1580 cm –1 ) and the peak intensity gradually increase with adsorption time. − These peaks indicate that CO 2 is effectively adsorbed on the surface of the TiO 2 @Bi 2 WO 6 catalyst to form a carbonate species.…”