Cr-doped SrTiO3/Ti-doped α-Fe2O3 heterojunction has been constructed by an ingenious way,i.e.using segregation titanium oxide on the surface of the Ti-doped α-Fe2O3 electrode to in situ prepare Cr-doped SrTiO3.After construction of the heterojunction,the photocurrent onset potential for water oxidation on a Ti4+ doped α-Fe2O3 cathodically shifts by about 100 mY.Moreover,the cathodic shift of the onset potential can be preserved well even after a long time running.The results indicate the effectiveness and credibility of the fabricated heterojunction.In order to make clear the reason for the onset potential shift,the as-prepared Ti-doped α-Fe2O3 and Cr-doped SrTiO3/Ti-doped α-Fe2O3 samples were investigated by X-ray photoelectron spectroscopy,electrochemical impedance spectroscopy,X-ray diffraction spectroscopy,etc.Based on the experimental evidences,it is proposed that cathodic shift of the onset potential is mainly due to the enhanced charge separation at the photoanode surface.This strategy can offer a reference to construct heteroiunction on other films especially for those with surface segregation.