RESUMO
A series of Zn x Cd1-x S monodispersed nanospheres were successfully synthesized with tunable band structures. As-prepared Zn x Cd1-x S solid solutions show much enhanced photocatalytic efficiency for CO2 photoreduction in aqueous solutions under visible light irradiation, relative to pure CdS analog. Methanol (CH3OH) and acetaldehyde (CH3CHO) are the major products of CO2 photoreduction for the solid solutions with x = 0, 0.2, and 0.5. Interestingly, Zn0.8Cd0.2S photocatalyst with a wide band gap can also additionally generate ethanol (CH3CH2OH) besides CH3OH and CH3CHO. The balance between the band structure-directing redox capacity and light absorption should be considered to influence both product yield and selectivity of CO2 photoreduction. The possible photoreduction mechanism was tentatively proposed.
RESUMO
Two-dimensional MoS2 nanosheets were in situ grown on TiO2 nanosheets to form two-dimensional (2D) hybrid nanojunctions, with which MoS2 nanosheets compactly contact with TiO2 to increase the interfacial area. MoS2 was identified as a promising cost-effective substitute for noble metal cocatalysts such as Pt, Au, and Ag, and shows superior activity and selectivity for reducing CO2 to CH3OH in aqueous solution to these metal cocatalysts under UV-vis light irradiation. The photo-luminescence (PL) spectra and transient time-resolved PL decay measurements reveal that the fast electron transfer from TiO2 to MoS2 can minimize charge recombination losses to improve the conversion efficiency of photoreduction. It reveals that Mo-terminated edges of MoS2 nanosheets possess the metallic character and a high d-electron density, and the Mo cation sites may benefit the stabilization of CHxOy intermediates via electrostatic attraction to enhance the CH3OH formation from the reduction of CO2 in aqueous solution.
