Photoelectrocatalytic oxidation of uric acid on a novel ruthenium(II) polypyridyl complex modified ZnO electrode for photo-stimulated fuel cells

•[Ru(tatp)3]2+/ZnO/ITO electrode shows a pair of redox peaks with E°′ = 0.458 V.•The prepared electrode shows high photoelectrocatalytic activity for UA oxidation.•A good linear response to UA between 0.1 μmol L−1 and 10.0 mmol L−1 is obtained.•The assembled UA fuel cell has attractive performances.

A novel [Ru(tatp)3]2+ (tatp = 1,4,8,9-tetra-aza-triphenylene) is first applied to the photoelectrocatalytic oxidation of uric acid (UA) upon incorporation of ZnO nanoparticles. [Ru(tatp)3]2+ adsorbed on an indium-tin oxide (ITO) or ZnO/ITO electrode shows a pair of well-defined redox peaks with the formal potential of 0.458 V (vs. Ag/AgCl with 0.05 mol L−1 NaCl salt bridge). The [Ru(tatp)3]2+/ZnO/ITO electrode with such an appropriate applied potential exhibits a good linear response for the electrocatalytic oxidation of UA between 0.1 μmol L−1 and 10.0 mmol L−1. Further studies reveal that the ultraviolet (UV) irradiation can greatly enhance the amperometric response of the [Ru(tatp)3]2+/ZnO/ITO electrode towards UA oxidation, and the photovoltaic effect of ZnO nanoparticles simultaneously improves the photoelectrocatalytic ability of [Ru(tatp)3]2+. Moreover, the [Ru(tatp)3]2+/ZnO/ITO electrode is found to work well as photoanode of a monopolar UA fuel cell. Upon exposure to 0.1 mW cm−2 UV light, the proposed cell has attractive performances, which indicate open-circuit photovoltage (Voc) of 0.508 V, short-circuit photocurrent (Isc) of 70.83 μA cm−2 and maximum power density (Pmax) of 16.09 μW cm−2 at 0.39 V, fill factor (ff) of 0.45 and photoenergy conversion efficiency (η) of 30.9%, respectively. The principle used in this study has an opportunity to extend into the synergistic application of photoelectrocatalysis in photo-stimulated fuel cells and photoelectrochemical sensors.

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