Surface states modulation of hematite photoanodes for enhancing photoelectrochemical catalysis

Sluggish interfacial carrier transfer and oxygen production kinetics of photoelectrochemical water split-ting are related to the Fermi-level pinning of the hematite surface states, thus it requires extra energy input and results in low PEC efficiency. Here we develop a facile secondary calcination strategy for regulating the density and distribution of surface states in hematite photoanode system. The fabricated alpha- Fe2O3-450 possesses significantly reduced disordered layers and renovated surface oxygen vacancy structure to increase carrier density and effectively passivate surface trapping states. Thus, both bulk and interfacial recombination of electrons and holes are effectively suppressed, and the quasi-hole Fermi level moves to more positive position, leading to a large photovoltage for reducing kinetic overpotential. Therefore, the photocurrent density of alpha-Fe2O3-450 (1.035 mA cm(-2)) is 1.8 times higher than that of pristine alpha-Fe2O3 (0.58 mA cm(-2)) at 1.23 V versus reversible hydrogen electrode, and alpha-Fe2O3-450 has more cathodic onset potential than alpha-Fe2O3. (C) 2021 Elsevier Ltd. All rights reserved.