Preparation of magnetic hematite/carbon nanoscrolls composite photocatalysts and its performance in photocatalytic N2/H2O synthesis of ammonia

In this paper, coal-based carbon nanoscrolls (CNS) were prepared using coal from Wucaiwan Coal Mine in Xinjiang as a carbon source: first, most of the impurities in the coal were removed by acid treatment; then, graphitization was carried out at high temperature; finally, coal-based CNS were prepared by a modified chemical intercalation method. Meanwhile, magnetic multi-shell hematite hollow spheres (α-Fe2O3) were prepared by the template method. Then, the composite photocatalysts α-Fe2O3/CNS with different hematite contents were prepared by loading hematite hollow spheres onto coal-based CNS substrates using the calcination method. The photocatalytic performance of the composites for N2/H2O to NH3 under visible light was investigated, and the material structure was also characterized. The results show that the coal-based CNS has a certain number of defective structures inside and has excellent visible light absorption and good electron transport properties. Using coal-based CNS as a carrier not only improves the light absorption performance of the catalyst in the visible range but also promotes the separation of photogenerated electron–hole pairs of the catalyst, thus promoting the photocatalytic activity of the catalyst. The α-Fe2O3/CNS prepared in this experiment has a narrow band gap width (Eg = 1.68 eV) and excellent visible light responsiveness. The NH3 yield of photocatalytic N2/H2O reaction for 4 h reached 1.662 mmol/ (L g cat.), which is 3.75 times higher than the yield of pure hematite microspheres for the photocatalytic NH3 synthesis under the same experimental conditions. In addition, the prepared α-Fe2O3/CNS catalyst has strong magnetic properties and is easy to be recovered.