Ultrafast timescale charge carrier dynamics in nanocomposite hematite photoelectrodes

Abstract

Hematite (α-Fe2O3) has been extensively studied as a candidate for solar water splitting. However, its overall efficiency in solar water splitting is currently low. In this study, Ti-doping, ZnFe2O4 shell and Co-Pi oxygen evolution catalysts (OECs) were applied on α-Fe2O3 nanocoral photoelectrode by forming a heterojunction to improve charge carrier separation. The current density of the Ti:Fe2O3/ZnFe2O4/Co-Pi nanocomposite photoelectrode at 1.23 VRHE was 3.6 mA/cm2. Moreover, the onset potential exhibited a cathodic shift of 0.85 VRHE, which improved the conversion efficiency to approximately 0.33 %. Transient absorption spectroscopy (TAS) was employed to investigate the yield and decay dynamics of photogenerated holes in the hematite-based photoelectrodes. The transient absorption data indicated different trends corresponding to the enhancement in the carrier separation due to band bending and holes transfer in the modified photoelectrodes. The enhancement in carrier separation was the origin of the high performance induced by long-lived carriers.