A TiO2 electrode was coated with chlorophyll a to regenerate nicotinamide adenine dinucleotide phosphate (NADPH), which can enhance the photovoltages of the electrodes for photoelectrochemical capacitors. The photovoltage of an uncoated TiO2 electrode was high during the first cycle but then steadily reduced owing to the oxidization of NADPH in the electrolyte during the photo-charge-discharge cycling. By contrast, a chlorophyll a-coated TiO2 electrode maintained high photovoltages for 100 cycles. Residual NADPH concentrations after 100 cycles increased from 73% to 90% because of the coating, demonstrating that NADPH was regenerated by photoexcited chlorophyll a similar to a photosynthetic reaction in nature.
Keywords: TiO2; chlorophyll a; nicotinamide adenine dinucleotide phosphate; photoelectrochemical reaction; photosynthesis; photovoltage.