EPR studies of electron and hole trapping in titania photocatalysts

► In situ EPR spectroscopy detects conduction band electrons trapped as Ti3+ in titania photocatalysts. ► Efficiency of electron trapping is different between anatase and rutile. ► Trapped valence band holes are largely EPR silent. ► Radicals produced by hole or electron transfer to adsorbed organic molecules adsorbed on titania relate to reaction mechanisms.