Effect of the electrolyte cations on photoinduced charge transfer at TiO2

The complete reduction of O2NC6H4CHO to H2NC6H4CH2OH needs photo-charging. Excess negative charge is compensated by cations adsorption and by lattice insertion. In the case of bulky le and TEA(+) (tetraethylammonium ions) that apparently are not inserted, protons are inserted instead. In contrast, Li+ (and to a lesser degree Na+) ions favour selective reduction of O2NC6H4CHO to H2NC6H4CHO.

This work focuses on the effect of electrolyte cations on the behaviour of a probe photocatalytic system comprising 2-propanol and 4-nitrobenzaldehyde (O2NC6H4CHO) as the hole and electron scavenger, respectively. Photo-reduction of the latter occurs via a stepwise pathway involving 4-aminobenzaldehyde (H2NC6H4CHO) as the stable intermediate and 4-aminobenzyl alcohol (H2NC6H4CH2OH) as the final product. 2-propanol photo-oxidation produces protons at the surface.