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

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 indiumtin 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 mu mol 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 (V-oc) of 0.508 V, short-circuit photocurrent (I-sc) of 70.83 mu A cm(-2) and maximum power density (P-max) of 16.09 mu W cm(-2) at 0.39V, fill factor (ff) of 0.45 and photoenergy conversion efficiency (eta) 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. (C) 2014 Elsevier Ltd. All rights reserved.