We report a photoanode based on Fe 2 O 3 /zinc oxide (ZnO) heterojunction synthesized by hydrothermal method for photoelectronchemical (PEC) water splitting. The forming heterojunction is systemically characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results from the I-V characteristic curve and conversation efficiency of Fe 2 O 3 /ZnO heterojunction reveal that the forming heterojunction would be a benefit for electron transferring from conduction band of ZnO to that of Fe 2 O 3 . However, the quantity of ZnO film has an effect on the photocurrent density, the suitable of which has shown enhanced PEC performance.Keywords: Fe 2 O 3 /ZnO; photoanode; photoelectrochemical property; water splitting. Photoelectrochemical (PEC) water splitting, as an effective way to solve the world's energy problem, has drawn wide attention. 1 Many metal oxides have been widely used in the process of the PEC water splitting, like TiO 2 , Fe 2 O 3 , zinc oxide (ZnO) and so on. 2-4 Especially, α-Fe 2 O 3 has been significantly investigated in-depth due to its various advantaged properties, such as chemical stability, erosion resistance, non-toxicity and high photocatalytic activity. 5 However, the photoelectric conversion efficiency of single α-Fe 2 O 3 is low 6 resulting from its short lifetime of photogenerated charge carriers, limited hole diffusion length, and poor mobility of charge carriers. 7 Heterostructured semiconductor material with unique energy band and properties of carrier transport can restrain the recombination of photogenerated electrons and holes to improve photoelectric conversion efficiency. [8][9][10] ZnO material is a kind of important inorganic materials, 11 and the corresponding reports of ZnO in the field of PEC water splitting have been mainly focused on characteristics of high transparency and high dispersion, 12,13 which might match with α-Fe 2 O 3 suitably. Taking account of its large band gap (c.a. 3.37 eV), ZnO takes a nature of responding ability to ultraviolet light. ZnO itself has low photocatalytic efficiency and high rate of photocorrosion, 14 but enhanced photocatalytic activity and superior structural stability will be achieved when the size of ZnO decreases into nanoscale. 15 Surface electronic structure and crystal structure of ZnO nanograins have changed, and the photocorrosion phenomena would mainly occur at the surface defect sites of ZnO.Based on the properties of above two matrices, the combination of Fe 2 O 3 and ZnO could effectively enhance separation of electrons and holes and improve photocatalytic activity, 16,17 due to their cooperativity of energy level structures. 18 Photocatalyst materials with heterojunction can be applied in PEC water splitting, and degrade various organic pollution in our environment. 19,20 The recent researches show that there are still lack of practical heterojunction with stable property and good photocatalytic performance. 21,22 So it is an urgent task for us to develop the re...