Recrystallization reduces surface oxygen vacancies to unlock hole transfer channel for hematite photoelectrochemistry

Hematite is a promising photoanode in photoelectrochemical water splitting system, but the slow water oxidation kinetics at the photoanode/electrolyte interface seriously limits the photoelectrochemical properties. Improving the surface state of hematite is an effective method to improve the transport and separation of carriers. Herein, we propose a strategy to recrystallize the hematite, which can effectively reduce the oxygen vacancies on the surface of hematite, increase active sites and improve the oxidation activity of water. The experimental results show that the charge recombination rate of the recrystallized Fe₂O₃ photoanode is reduced, and the carrier transport efficiency is improved. The photocurrent density at 1.23 V is four times higher than that of the original hematite, and the initial potential shifts negatively by about 20 mV, which is attributed to the upward bending of hematite energy band and the reduction of surface defects after treatment. This research provides a feasible strategy for designing efficient α-Fe₂O₃ photoanode.