The commercial application of artificial photosynthesis systems necessitates the development of stable and efficient heterogeneous catalysts to overcome the slow kinetics of water oxidation. Herein, [Ru(tpy)(dcbpy)OH2]2+ (tpy = 2,2′:6′,2′′-terpyridine, dcbpy = 5,5′-dicarboxy-2,2′ -bipyridine) -doped UiO-67 metal-organic framework (MOF) thin films were grown on fluorine-doped tin oxide (FTO) glass for electrochemical water oxidation. The electrocatalyst retained the catalytic activity of the parent Ru complex, oxidizing water with a TOF of 0.2 (±0.1) s-1 at 1.71 V vs NHE in buffered solution (pH ~7), while exhibiting structural and electrochemical stability. This work provides evidence for the transmission of electrons (and ions) through MOF thin films via redox hopping pathways on the basis of scan-rate dependent voltammetry studies. Specifically, as the concentration of redox-active species increased within the film, the dependence of the observed current on the sweep scan rate decreased from one to one-half, indicating that the origin of the current was change from surface-bound catalysts to in-MOF electrons and ions diffusion. Our results demonstrates a promising way to immobilize large concentrations of electroactive water-oxidation catalysts throughout the MOF thin film scaffold, paving the way for future photoelectrochemical water splitting systems.

Investigations of water oxidation by catalysts incorporated metal-organic frameworks

254th National Meeting (2017)

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