Facile deposition of Cu 2 O in a UV-enhanced sulfite-mediated glucose fuel cell for photoelectrocatalytic reduction of oxygen

The photoelectrocatalytic oxidation of glucose (Glu) on a TiO2 photoanode promoted by sulfite can drive the cathodic deposition of flower-like cuprous oxide (Cu2O) crystals through an evolution from cube, truncated cube and truncated octahedron on an indium-tin oxide (ITO) electrode in a UV-excited Glu/Cu(II) fuel cell. The cathodic deposition kinetics of Cu2O is investigated by varying Glu concentration, operation pH and temperature under pseudo-first-order conditions. The spontaneous endothermic deposition reaction is controlled by a coupled dehydration conversion from Glu to 5-hydroxymethylfurfural (5-HMF). The proposed cathodic deposition method has the merits of mild reaction condition, environment-friendly procedure, no requirement of applied voltage, and harvesting UV photons (Pin = 55 μW cm−2) and chemical energy from 1.0 mol L−1 Glu/0.1 mol L−1 SO32− (298 K, pH 12) to produce open-circuit photovoltage (Voc) of 1.121 V, short-circuit current density (isc) of 0.25 mA cm−2 and power conversion efficiency (η = Pmax/Pin) of 14.8%. Furthermore, the as-prepared Cu2O can act as cathode catalysts to improve remarkably the performances of photoelectrochemical Glu/O2 fuel cells (298 K, pH 7) based on its photoelectrocatalytic activity towards the reduction of oxygen with the assistance of methylene blue (MB).