Effective charge separation in the rutile TiO2 nanorod-coupled α-Fe2O3 with exceptionally high visible activities

Herein, we have fabricated rutile TiO2 nanorod-coupled α-Fe2O3 by a wet-chemical process. It is demonstrated that the visible activities for photoelectrochemical water oxidation and for degrading pollutant of α-Fe2O3 are greatly enhanced after coupling a proper amount of rutile nanorods. The enhanced activity is attributed to the prolonged lifetime and improved separation of photogenerated charges mainly by the transient surface photovoltage responses. Interestingly, the observed EPR signals (with g⊥ = 1.963 and g|| = 1.948) of Ti(3+) in the fabricated TiO2-Fe2O3 nanocomposite at ultra low temperature (1.8 k) after visible laser excitation, along with the electrochemical impedance spectra and the normalized photocurrent action spectra, testify evidently that the spacial transfers of visible-excited high-energy electrons of α-Fe2O3 to TiO2 could happen. Moreover, it is confirmed that it is more favorable for the uncommon electron transfers of α-Fe2O3 to rutile than to anatase. This is responsible for the much obvious enhancement of visible activity of Fe2O3 after coupling with rutile TiO2, compared with anatase and phase-mixed P25 ones. This work would help us to deeply understand the uncommon photophysical processes, and also provide a feasible route to improve the photocatalytic performance of visible-response semiconductor photocatalyst for water splitting and pollutant degradation.