Effective Carbon Dioxide Photoreduction over Metals (Fe-, Co-, Ni-, and Cu-) Incorporated TiO2/Basalt Fiber Films

Abstract

Mineralogical basalt fibers as a complementary adsorbent were introduced to improve the adsorption of CO ₂over the surfaces of photocatalysts. TiO ₂photocatalysts (M-TiO ₂) incorporated with 5.0 mol.% 3d-transition metals (Fe, Co, Ni, and Cu) were prepared using a solvothermal method and mixed with basalt fibers for applications to CO ₂photoreduction. The resulting 5.0 mol.% M-TiO ₂powders were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, photoluminescence, Brunauer, Emmett, and Teller surface area, and CO ₂-temperature-programmed desorption. A paste composed of two materials was coated and fixed on a Pyrex plate by a thermal treatment. The 5.0 mol.% M-TiO ₂/basalt fiber films increased the adsorption of CO ₂significantly, indicating superior photocatalytic behavior compared to pure TiO ₂and basalt fiber films, and produced 158~360 μmol ${\mathrm{g}\mathrm{c}\mathrm{a}\mathrm{t}}^{-1}$ L ⁻¹CH ₄gases after an 8 h reaction. In particular, the best performance was observed over the 5.0 mol.% Co-TiO ₂/basalt fiber film. These results were attributed to the effective CO ₂gas adsorption and inhibition of photogenerated electron-hole pair recombination.