Photocatalysis by metal doped semiconductor is attracting major attention to enable the reduction of CO₂(g) in the presence of water vapor as a hole scavenger. Such technology has the potential to produce chemical feedstock and simultaneously minimize environmental pollution. Potassium doped iron oxide (α-Fe₂O₃) of varying potassium compositions (100 Fe:x K, 0 ≤ x ≤ 5) are synthesized using incipient wetness impregnation method. The structure, composition, and properties of the catalysts are investigated by X-ray diffraction, nitrogen adsorption-desorption experiments, DSC, TGA, and multiple spectroscopies, including: DRUV-vis, FTIR, Raman, ICP-AES, XPS and UPS, TEM with EDS and SAED. UV-visible light (λ ≥ 295 nm) excited the catalysts uniformly deposited in a cylindrical photoreactor in presence of pure CO₂ or air (400 ppm CO₂), both under a saturated water vapor atmosphere. The maximum production of CO(g) (R_CO = 0.5836 μmol g_cat^-1 h^-1 in pure CO₂ and R_CO = 0.4267 μmol g_cat^-1 h^-1in air) quantified by GC-TCD-FID corresponds to 100Fe:1K photocatalyst. The surface doped potassium photocatalyst enhances the photocatalytic efficiency by creating a more negative conduction band than the CO₂/CO reduction potential as supported by UPS and DRUV-vis spectroscopies. The photoreduction mechanism and also the effects of scavenger species will be reported.

Zhiming Liang

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