Abstract
Unprecedented metal‐free photocatalytic CO2 conversion to CO (up to 228±48 μmol g−1 h−1) was displayed by TiO2@IL hybrid photocatalysts prepared by simple impregnation of commercially available P25‐titanium dioxide with imidazolium‐based ionic liquids (ILs). The high activity of TiO2@IL hybrid photocatalysts was mainly associated to (i) TiO2@IL red shift compared to the pure TiO2 absorption, and thus a modification of the TiO2 surface electronic structure; (ii) TiO2 with IL bearing imidazolate anions lowered the CO2 activation energy barrier. The reaction mechanism was postulated to occur via CO2 photoreduction to formate species by the imidazole/imidazole radical redox pair, yielding CO and water.
Highlights
(i. e., CO2 thermal reduction and CO2 electroreduction).[2b]
We demonstrate that the enhancement of the CO2-photocalytic performance is associated to (i) a shift of the TiO2@ionic liquids (ILs) valence and conduction band edge with simultaneously decreasing the band gap when compared to bare TiO2; (ii) continuous generation of formate species via imidazole/imidazole radical redox pair lowered the activation barrier energy of CO2 photoreduction (Figure 1)
The photoreduction of CO2 was first performed in aqueous solution of ILs,[21] without the presence of TiO2 (Table 1)
Summary
E., valence and conduction band edge energies and modification of the band gap).[18] In this case, the IL may provide the driving force towards photocatalytic redox process by formation of a solid semiconductor-liquid junction improving the charge separation and tuning the electron/hole ratio. We demonstrate that the enhancement of the CO2-photocalytic performance is associated to (i) a shift of the TiO2@IL valence and conduction band edge with simultaneously decreasing the band gap when compared to bare TiO2; (ii) continuous generation of formate species via imidazole/imidazole radical redox pair lowered the activation barrier energy of CO2 photoreduction (Figure 1)
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