The Composite Modification And Photocatalytic Performance Of Nano - Fe 'sub - 2 3 Photogenerated Charge Separation

Photocatalytic reduction of CO2 and degradation of pollutants using sunlight is an ideal solution to the global warming and energy issue. Among various semiconductor photocatalysts, a-Fe₂O₃ has attracted great attention because of its high stability, low cost, nontoxicity, environmental compatibility, and narrow band gap（about 2.1 e V）.However, it usually exhibits low photocatalytic activities, which is mainly attributed to the high charge recombination. Therefore, it is highly desired to enhance the photogenerated charge separation of Fe₂O₃. The C with the two dimensional structure,like graphene, is always used to improve the properties of Fe₂O₃. The influence of the heterogeneity on the adsorption of the reactants, such as CO2 and O2, is often neglected,so the modification mechanism is not analysized clearly. It is very necessary for us to consider the improvement of the content of the quaternary N in C with the two-dimensional structure such as graphene. It is expected that the photogenerated charge separation and photocatalytic activity of Fe₂O₃ are improved by the composite modification. In this paper, we focus on the modification of graphene with high amount of quaternary N and the modification of g-C3N4 with higher amount of quaternary N on Fe₂O₃.Firstly, N-doped graphene was prepared by the wet chemistry method and the content of quaternary N is controlled by altering the hydrothermal temperature. Then Fe₂O₃ was modified with the N-doped graphene by the wet-chemical method. The results of the atmosphere-controlled surface photovoltage spectra and time-resolved surface photovoltage responses show that the quaternary N in the N-doped graphene-Fe₂O₃ nanocomposite plays important roles in the transfer and transportation of photogenerated charges, leading to the obviously improved photocatalytic activities of Fe₂O₃. It is due to the fact that the quaternary N could increase the amount of CO2 and O2 adsorption, which is verified by the temperature-programmed desorption curves.Secondly, the amount of quaternary N in N-doped graphene is limited. In order to further improve the content of quaternary N, we thought of graphite carbon nitride（g-C3N4）. The g-C3N4 is a new type of photocatalytic semiconductor material and it hasthe same structure as graphene. g-C3N4 mainly contains quaternary N. N-doped graphene/Fe₂O₃ composite and g-C3N4-Fe₂O₃ composite was prepared, respectively.Then the comparative study on the two kinds of composites was carried out. The photogenerated charge separation and photocatalytic performance of the samples were significantly improved after compositing with g-C3N4. The optimal composite amount of g-C3N4 and Fe₂O₃ was further explored in order to obtain the best photocatalytic activity of the composites.This work would provide some new ideas to design and synthesize Fe₂O₃ modified with the two dimensional structure C, and the basis of further studying the mechanism of photocatalytic reaction.