PHOTOELECTROCHEMICAL CELLS / Overview

The discovery that photoelectrochemical cells (PECs) can convert solar energy into useful fuels or electricity dates back to the early 1970s. Since then, considerable improvements have been made in cell design and in the choice of materials for photoelectrode, electrolyte, and auxiliary electrode. Many PECs now show solar conversion efficiencies exceeding 10%. Electrodes and electrolytes have been optimized not only to increase efficiency, but also to keep the corrosion reactions under control and to allow long-term cell stability. New, nanostructured materials have been developed and have allowed the widespread use of dye sensitization in conjunction with large-bandgap semiconductor electrodes. PECs are divided into three main categories according to the basic mode of operation: regenerative PECs, in other words wet photovoltaic (PV) cells (no Gibbs function change in the cell, ?G=0); photoelectrolytic cells, in which two separate redox reactions are driven at the two electrodes (for an overall ?G<0); cells for photoelectrocatalysis (?G<0), with potential applications in different fields, including environmental purification.