A hole-selective hybrid TiO2 layer for stable and low-cost photoanodes in solar water oxidation

Abstract The use of conductive and corrosion-resistant protective layers represents a key strategy for improving the durability of light absorber materials in photoelectrochemical water splitting. For high performance photoanodes such as Si, GaAs, and GaP, amorphous TiO 2 protective overlayers, deposited by atomic layer deposition, are conductive for holes via a defect band in the TiO 2 . However, when coated on simply prepared, low-cost photoanodes such as metal oxides, no charge transfer is observed through amorphous TiO 2 . Here, we report a hybrid polyethyleneimine/TiO 2 layer that facilitates hole transfer from model oxides BiVO 4 and Fe 2 O 3 , enabling access to a broader scope of available materials for practical water oxidation. A thin polyethyleneimine layer between the light absorber and the hybrid polyethyleneimine/TiO 2 acts as a hole-selective interface, improving the optoelectronic properties of the photoanode devices. These polyethyleneimine/TiO 2 modified photoanodes exhibit high photostability for solar water oxidation over 400 h.