Self-powered sensor for tannic acid exploiting visible LED light as excitation source

The present work describes the development of a self-powered photoelectrochemical sensor for the determination of tannic acid (TA) based on a TA-sensitized TiO2 (TA/TiO2/FTO) as photoanode and Cu2O/ZnO/FTO photocathode to water reduction. The self-powered cell was comprised of a photoanode and a photocathode separated in two chambers to generate the suitable power output under irradiation from a visible LED light driving the tannic acid sensing process. The electronic characteristics of TA/TiO2/FTO photoanode and Cu2O/ZnO/FTO photocathode were evaluated by electrochemical impedance spectroscopy. The principle of the self-powered photoelectrochemical cell is based on water reduction in the cathodic chamber on the Cu2O/ZnO/FTO photocathode while TA is oxidized in the anodic chamber to generate a cell output which depends on the concentration of TA in the anodic compartment. Under optimized conditions, the cell presented a wide linear response range for TA from 1 μmol L−1 up to 500 μmol L−1, demonstrating that the capability of the proposed system to generate power can be modulated by the TA concentration.