| Utilization of solar energy photocatalytic water splitting is an effective method to obtain renewable energy and clean energy. Because of the characteristic of a-Fe2O3 is abundant, stable quality, non-toxic and photocatalytic activity and become one of the hotspots in the new water splitting materials. Band gap width(Eg) of a-Fe2O3 is about 2.1e V, maximum absorption wavelength at 590 nm, and the narrow band gap width able to absorb and utilize the most of sun’s light. But widespread industrial application of nano-a-Fe2O3 material is still restricted by several aspects, such as poor electrical conductivity; hole diffusion distance is short(about 2-4 nm); prepared a larger particle size of a-Fe2O3 currently; Based on atomic layer deposition、chemical vapor deposition method prepared hematite film process, the higher requirement on the equipment, the preparation process complexity, high cost.In this paper, the preparation of ultra-small particles of α-Fe2O3 thin film with a relatively simple the separated two-phase hydrolysis-solvothermal reaction(hydrothermal method), dissolved in n-butanol solution of α-Fe2O3 precursor acetylacetonate iron, in the interface reaction with ammonia to prepare the diameter of 5-8nm α-Fe2O3. The ultrafine nanocrystalline a-Fe2O3 may facilitate the efficient transport of the photogenerated minority carriers to the liquid interface.The Ti O2 underlayer was coated on conductive fluorine-doped tin oxide(FTO) glass by spin coating. The hematite films were formed layer-by- layer by repeating hydrothermal method. We studied the effects of different Ti O2 film thickness on the structure, absorption spectrum and photoelectric properties of a-Fe2O3 film. Hematite film to be formed on Ti O2-modified FTO substrate shows much higher photocurrent densities for more efficient water splitting. When the Ti O2 concentration was 1.0 mg/m L ethanol, a 16-nm- thick Ti O2 film was coated on the FTO substrate. The Ti O2 underlayer plays an important role in the preparation of a-Fe2O3/Ti O2 and markedly improves the photocurrent in photoelectrochemical water splitting. Ti O2 act as an intermediary to alleviate the dead layer effect and as a support of large surface areas to coat greater amounts of Fe2O3. Fe2O3 thin film with four cycles deposition on FTO and 1.0-Ti O2- modified FTO substrate, a detailed analysis of the promoting effect of Ti O2 on photocurrent of a-Fe2O3.Then studied deposited effects of repeated times on the photoelectrochemical properties of of a-Fe2O3 thin films preparated by hydrothermal method. A photocurrent of 0.683 m A/cm2 was obtained at +1.5 V vs. RHE when hematite film was deposited for four cycles. We conducted a Co-Pi surface modification for a-Fe2O3/Ti O2 and found that the use of light-assisted electrochemical deposition of Co-Pi 200 s, open-circuit voltage left shift 0.35 V of water splitting, but also get a higher photocurrent.A total photocurrent of up to 1.53 m A/cm2 was obtained at +1.5 V vs. RHE under visible light(100 m W/cm2) illumination when the four combined photoanodes were used in tandem. The evolution of H2 and O2 originated by the water-splitting process was measured on-line using single optimal photoanode. The photocurrent of the hematite photoanodes remained at approximately 0.68 m A/cm2 over 3 h without degradation. These results show that α-Fe2O3/Ti O2 nano films are very stable and highly efficient for water splitting under visible light. |
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