کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
45801 | 46422 | 2013 | 10 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Tailoring Cu valence and oxygen vacancy in Cu/TiO2 catalysts for enhanced CO2 photoreduction efficiency Tailoring Cu valence and oxygen vacancy in Cu/TiO2 catalysts for enhanced CO2 photoreduction efficiency](/preview/png/45801.png)
The incorporation of Cu species in TiO2 photocatalysts is critical in photocatalytic CO2 reduction to fuels, but the effect of Cu valence is poorly understood. In this work, Cu/TiO2 (P25) nanoparticle catalysts were prepared by a simple precipitation and calcination method. The as-prepared Cu/TiO2 sample was dominated by Cu2+ species. Thermal pretreatment of the as-prepared samples in He and H2 atmosphere resulted in the transition to a surface dominated by Cu+ and mixed Cu+/Cu0, respectively, confirmed by in situ X-ray photoelectron spectroscopy (XPS) and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses. These thermal pretreatments in reducing atmospheres also induced the formation of defect sites such as oxygen vacancies and Ti3+. The various Cu/TiO2 catalysts were tested in CO2 photoreduction with water vapor under simulated solar irradiation, and their activities were in the order of as-prepared (unpretreated) < He-pretreated < H2-pretreated. Compared with unpretreated TiO2 (P25), the H2-pretreated Cu/TiO2 demonstrated a 10-fold and 189-fold enhancement in the production of CO and CH4, respectively. This significant enhancement was mainly attributed to the synergy of the following two factors: (1) the formation of surface defect sites promoting CO2 adsorption and subsequent charge transfer to the adsorbed CO2; (2) the existence of Cu+/Cu0 couples that facilitate electron and hole trapping at different sites.
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► Cu/TiO2 photocatalysts are fabricated for CO2 photoreduction with water vapor.
► Cu valence and oxygen vacancy are tailored by thermal treatment in He or in H2.
► Photo-activity in the order: H2-pretreated > He pretreated > unpretreated.
► Mixed Cu+/Cu0 promote electron–hole separation more effectively than Cu+ and Cu2+.
► CO2− species is a CO2 reduction intermediate according to in situ DRIFTS.
Journal: Applied Catalysis B: Environmental - Volumes 134–135, 2 May 2013, Pages 349–358