Synergetic Surface Sensitivity of Photoelectrochemical Water Oxidation on TiO2 (Anatase) Electrodes

The paper compares photoelectrocatalytic activity and selectivity of nanocrystalline anatase dominated by {110}, {101}, and {001} faces in photo(electro)catalytic water splitting. Although the anodic half-reaction of water splitting—oxygen evolution—dominates the overall photoelectrochemical behavior of the photoexcited anatase, simultaneous reduction under photoelectrochemical conditions is also observed on some anatase faces. The activity of individual facets in anodic half-reaction of water splitting (oxygen evolution) increases in the order {101} < {110} < {001}. The increasing oxidation activity tracks the tendency of the surface to generate the OH• radical producing intermediates (H2O2, ozone) on the trapped hole states. The activity in reduction processes increases in the reversed order. Particularly, the reduction activity of the {101} oriented anatase can be attributed to pronounced hydrogen evolution by a charge transfer of photogenerated electrons. The observed trends agree with DFT-based model...