EPR STUDIES OF HOLE AND ELECTRON TRAPPING IN TITANIA PHOTOCATALYSTS

摘要

The creation, recombination and trapping of holes and electrons, and the transfer of electrons between a semiconductor and adsorbed molecules or between two different semiconductors, are all processes of vital importance to the successful operation of photocatalytic, photoelectrochemical and photovoltaic devices. EPR spectroscopy, which observes one–electron species exclusively, is uniquely placed to observe these processes. The technique is highly sensitive (less than 10~(13) spins can be detected), and can be readily adapted to in-situ observation of processes occurring at the solid-gas or solid-liquid interfaces during irradiation. The conventional continuous wave (CW) EPR experiment is not time resolved (shortest time scales measurable are 100s of milliseconds), but measurements at 4 K allow many species to be observed under steady state irradiation which are too short-lived to be detected at room temperature.