Experiments with the titanium dioxide-ruthenium tris-bipyridine-nickel cyclam system for the photocatalytic reduction of CO2

Abstract

Ruthenium tris-bipyridine derived complexes functionalized by either carboxyl or phosphonyl groups were tested as sensitizers for the photocatalytic reduction of carbon dioxide in the presence of nickel cyclam acting as a catalyst, and a sacrificial donor. These systems were shown to be as efficient as the unsubstituted compounds in solution. Covalent binding to titania nanoparticles gave slightly different results from those with the untreated semiconductor.

Not that innocent – ammonium ions boost homogeneous light-driven hydrogen evolution

“…Specifically, the lifetime of the reduced Ru-PS˙ − approximately doubles in the presence of ammonium ions (10 mM). In contrast to earlier reports on Ru-PS˙ − in a DMF/sodium ascorbate system, 26 we observed a bi-exponential decay, in the presence of ammonium or tetraethyl ammonium (Fig. 3B).…”

Not that innocent – ammonium ions boost homogeneous light-driven hydrogen evolution

“…Specifically, the lifetime of the reduced Ru-PS˙ˉ approximately doubles in the presence of ammonium ions (10 mM). In contrast to earlier reports on Ru-PS˙ˉ in a DMF/sodium ascorbate system, 30 we observed a bi-exponential decay, in the presence of ammonium or tetraethyl ammonium (Figure 3B). This observation is tentatively assigned to the presence of oxidised SED, which is known to act as an efficient quencher for the reduced Ru-PS˙ˉ.…”

Photochemical CO2 reduction in water using a co-immobilised nickel catalyst and a visible light sensitiser

“…10,11 An alternative photocatalytic approach uses [Ru(bpy) 3 ] 2+ (bpy = 2,2 0 -bipyridine) in aqueous solution with NiCyc. [12][13][14][15] Here excitation of the ruthenium dye with visible light gives rise to a metal to ligand charge transfer (MLCT) state 16 that is reductively quenched by a sacrificial electron donor, such as ascorbate, to form [Ru(bpy) 3 ] + that in turn transfers an electron to NiCyc (Scheme 1a). 13 However initial studies reported low efficiencies, proposed to be due to inefficient electron transfer from the reduced ruthenium dye to NiCyc.…”