Quantum Dot Sensitized Titania Applicable as Photoanode in Photoactivated Fuel Cells

Abstract

Quantum dot sensitized nanocrystalline titania has been studied as a photoanode in photoactivated fuel cells functioning in the presence of aqueous alkaline electrolyte containing ethanol as fuel. The results encourage the employment of quantum dot sensitized photoanodes absorbing visible radiation. The best choice of a photosensitizer is a combination of 75% CdS with 25% ZnS (atomic metal ratio). Other sensitizer combinations involving CdSe have also been examined. The target sought for in a photoactivated fuel cell is the photocatalytic oxidation of a fuel; therefore, it was concluded that utilization of panchromatic sensitizers is not the best choice for a photoanode, since too much of a decrease in the combined energy band gap leads to a decrease of the oxidative power of the material. The photocurrents produced by a cell using an optimized photoanode were high and corresponded to an incident photon to current conversion efficiency higher than 1. Such a situation is realized when the oxidation of the fuel proceeds by formation of radical intermediates and additional electron injections into the photocatalyst.