Direct Observation of Charge Separation on Anatase TiO2 Crystals with Selectively Etched {001} Facets

Synchronous illumination X-ray photoelectron spectroscopy (SIXPS) was employed for the first time to directly identify the photogenerated charge separation and transfer on anatase TiO2 single-crystals with selectively etched {001} facets. More specifically, for the TiO2 crystals with intact {001} and {101} facets, most of photo generated charge carriers rapidly recombined, and no evident electron hole separation was detected. With selectively etching on {001} facets, high efficient charge separation via hole transfer to titanium and electron to oxygen was clearly observed. However, when the {001} facets were completely etched into a hollow structure, the recombination for photogenerated electron hole pairs would dominate again. These demonstrations dearly reveal that the appropriate corrosion on {001} facets could facilitate more efficient electron hole separation and transfer. As expected, the optimized TiO2 micro crystals with etched {001} facets could achieve a hydrogen generation rate of 74.3 mu mol/h/g, which is nearly 7 times higher than the intact-TiO2 crystals.