EPR spin trapping evidence of radical intermediates in the photo-reduction of bicarbonate/CO2 in TiO2 aqueous suspensions.
Photochem Photobiol Sci
; 14(5): 1039-46, 2015 May.
Article
en En
| MEDLINE
| ID: mdl-25849227
ABSTRACT
Using the EPR spin trapping technique, we prove that simultaneous reactions take place in illuminated suspensions of TiO2 in aqueous carbonate solutions (pH ≈ 7). The adsorbed HCO3(-) is reduced to formate as directly made evident by the detection of formate radicals (ËCO2(-)). In addition, the amount of OHË radicals from the photo-oxidation of water shows a linear dependence on the concentration of bicarbonate, indicating that electron scavenging by HCO3(-) increases the lifetime of holes. In a weakly alkaline medium, photo-oxidation of HCO3(-)/CO3(2-) to ËCO3(-) interferes with the oxidation of water. A comparative analysis of different TiO2 samples shows that formation of ËCO2(-) is influenced by factors related to the nature of the surface, once expected surface area effects are accounted for. Modification of the TiO2 surface with noble metal nanoparticles does not have unequivocal benefits the overall activity improves with Pd and Rh but not with Ru, which favours HCO3(-) photo-oxidation even at pH = 7. In general, identification of radical intermediates of oxidation and reduction reactions can provide useful mechanistic information that may be used in the development of photocatalytic systems for the reduction of CO2 also stored in the form of carbonates.
Texto completo:
1
Bases de datos:
MEDLINE
Asunto principal:
Titanio
/
Bicarbonatos
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Dióxido de Carbono
/
Agua
/
Procesos Fotoquímicos
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
Photochem Photobiol Sci
Asunto de la revista:
BIOLOGIA
/
QUIMICA
Año:
2015
Tipo del documento:
Article
País de afiliación:
Italia