Quantum dot sensitized titania for photo-fuel-cell and for water splitting operation in the presence of sacrificial agents

Abstract

Abstract Photoelectrochemical cells have been constructed using quantum dot sensitized nanocrystalline titania photoanodes and were operated under photo-fuel-cell operation to produce electricity or water-splitting operation to produce hydrogen. In the first case, the cell functioned in the presence of an alkaline electrolyte using ethanol as fuel. The obtained data allowed to define the optimal thickness of the titania film, which was approximately 15 μm. Functional sensitizers were CdS or ZnSe combined with CdS. Small band gap quantum dot sensitizers like CdSe and PbS were not functional in photo-fuel-cells, owing to the limited oxidative power of their valence-band holes. For water-splitting operation, we mainly used a S 2− /SO 3 2− electrolyte. In that case, panchromatic sensitization is possible. Thus the photoanode, which gave the highest hydrogen production rate, was constructed by combining TiO 2 /FTO with ZnS/CdSe/CdS quantum dots. Hydrogen was produced by applying an external bias of 0.5 V. In the absence of bias the quantity of hydrogen was very small. Hydrogen production rate was also very small in a purely alkaline environment with ethanol as fuel.