Evaluation of Chromophore and Assembly Design in Light-Driven Water Splitting with a Molecular Water Oxidation Catalyst

The water oxidation catalyst [Ru(bda)(4-O(CH 2 ) 3 P(O 3 H 2 ) 2 -pyr) 2 ], 1, (pyr = pyridine; bda = 2,2′-bipyridine-6,6′-dicarboxylate) was investigated as the catalyst part of a series of chromophore–catalyst assemblies for light-driven water splitting in dye-sensitized photoelectrosynthesis cells (DSPECs). Both coloaded and layer-by-layer assemblies with phosphonate-Zr(IV) bridging were investigated on SnO 2 /TiO 2 core–shell electrodes. Device performance was evaluated by both photocurrent and direct O 2 measurements in collector–generator cells. The photoelectrodes displayed impressive photocurrents (0.72–1.5 mA/cm 2 ) and Faradaic efficiencies for O 2 generation (71–97%) under 1 sun illumination in pH 5.7, 0.1 M acetate buffer solutions and provided important mechanistic insights into the microscopic details for DSPEC water splitting.