SiC: A Photocathode for Water Splitting and Hydrogen Storage

摘要

The report by Fujishima and Honda in 1971 that a TiO2 photoanode, short-circuited to a Pt cathode, could be used to split water into hydrogen and oxygen caught the imagination of the scientific community. Illumination of the n-type semiconductor creates electrons and holes. The minority carriers oxidize water to oxygen while the electrons reduce protons or water at the counter electrode to produce hydrogen. This discovery offered the prospect of using sunlight to produce environmentally friendly fuel. TiO2 is chemically a very stable photoanode. However, the large band gap (3.2 eV) means that only the UV part of the solar spectrum is effective in water splitting. Subsequent work has concentrated on n-type semiconductors with a smaller band gap, such as WO3 and Fe2O3. Promising results based on the chemical modification of TiO2 have recently been reported. An alternative approach to splitting water is to generate hydrogen at a photocathode (a p-type semiconductor) and oxygen at the counter electrode. Turner and his group have shown that p-type GaInP2, either coupled to a photovoltaic device (a GaAs p/n junction) or in combination with a photoanode (α-Fe2O3 or WO3), offers interesting possibilities. Recently, Mor et al. reported a similar approach with a combination of a p-type Cu-Ti-O nano-tube array and an n-type TiO2 nanotube array. Hydrogen production at these photocathodes short-circuited to Pt has not been reported.