Photoelectrocatalytic response of tris(2,2′-bipyridyl)ruthenium(II)-modified mesoporous silica film on ITO electrode with methyl viologen quencher and EDTA donor

Abstract

International audienceIn the present paper, we investigate the photoelectrochemical behaviour of a tris(bipyridine) derivative (denoted [Ru(bpy)2(bpy')] 2+ ) covalently immobilized in the nanochannels of a vertically aligned mesoporous silica film (VMSF) generated by electrochemically assisted self-assembly (EASA) onto a transparent indium-tin oxide (ITO) electrode, in solutions containing a quencher (methyl viologen, MV 2+ ) and a model substrate partner (ethylenediaminetetraacetate, EDTA). The optimal film loading was first determined according to its solid-state photophysical properties. Then, the electrochemically accessible [Ru(bpy)2(bpy')] 2+ moieties were exploited in the presence of the MV 2+ quencher alone in solution (aerated medium) to demonstrate the possible electrochemical regeneration of the photocatalyst immobilized in VMSF on ITO. This was achieved on the basis of experiments carried out by hydrodynamic amperometry at constant potential under successive sequential illumination (at 400 nm) and dark periods. Finally, the functionalized film was applied to the photoelectrocatalytic oxidation of EDTA in an oxygen-free solution containing also MV 2+ species, thanks to the effective electrochemical regeneration of the quencher, as also evidenced by photocurrent measurements as a function of time with successive switching of light from 'off' to 'on' and vice versa. Such photoelectrocatalytic transformation of EDTA is possible at a much lower potential (-0.1 V) than that observed for its direct electrocatalytic oxidation by the same [Ru(bpy)2(bpy')] 2+ -functionalized film operating without light (+1.2 V).</div