Enhanced visible-NIR absorption and oxygen vacancy generation of Pt/HxMoWOy by H-spillover to facilitate photothermal catalytic CO2 hydrogenation
JOURNAL OF MATERIALS CHEMISTRY A(2022)
Abstract
Photothermal catalytic hydrogenation of CO2 is an intriguing approach to reduce CO2 under mild conditions, which is possible because of photoinduced electron-hole pair generation and an overall increase in the localized temperature under light irradiation. However, the lack of a catalyst with an adequate photothermal conversion efficiency and the ability to generate a sufficient number of photoinduced electrons are the main factors limiting the applicability of this method. H-doped WOy demonstrates surface plasmon resonance (SPR) capabilities, and can be adjusted by changing the dopant (H+) concentration. To improve the potential of the WOy plasmonic effect based on H-doping, we herein report that the Mo-doped Pt/WOy (Pt/MoWOy) substantially increases the dopant (H+) and oxygen vacancy concentration in Pt/HxMoWOy during the H-2 reduction process, facilitating photothermal hydrogenation of CO2 to CO. The developed Pt/HxMoWOy exhibits excellent catalytic performance (3.1 mmol h(-1) g(-1)) in the photothermal reverse water-gas shift (RWGS) reaction at 140 degrees C, outperforming undoped Pt/HxWOy (1.02 mmol h(-1) g(-1)). Experimental and comprehensive analyses, including photoelectrochemical measurements, UV-Vis-NIR diffuse-reflectance spectroscopy, and a model reaction, showed that abundant surface free electrons and oxygen vacancies (V-O) in Pt/HxMoWOy are responsible for the efficient CO2 adsorption and transfer of photoinduced electrons to carry out the reduction of CO2 to CO. X-ray photoelectron spectroscopy (XPS) and in situ X-ray absorption fine structure (XAFS) measurements revealed a reversible redox event for the Mo and W atoms during the RWGS reaction, confirming that the oxygen vacancies between Mo and W atoms in Pt/HxMoWOy act as active sites and that Pt nanoparticles activate H-2 to enable the regeneration of the oxygen vacancies. Moreover, density functional theory (DFT) calculations demonstrated that Mo-doping substantially decreases the energy barrier for oxygen vacancy formation in WOy in the H-2 reduction process. We expect that this study will provide an innovative strategy for designing a highly efficient catalyst for photothermal CO2 conversion.
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Key words
CO2 Reduction,Photocatalytic,NOx Reduction,Selective Oxidation,Hydrogen Production
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