Synthesis And H₂ Sensing Properties Of Al-doped SnO₂/graphene Composites

The graphene oxide?GO?was prepared through a modified Hummers'method.Then,the flower-like SnO₂,a series of SnO₂/graphene?S-G?composites and Al-SnO₂/graphene?A-S-G?have been synthesized through a simple one-pot hydrothermal method using SnCl₄·5H₂O,NaOH and GO as ingredient.The as-prepared products were characterized by X-ray diffraction?XRD?,field emission scanning electron microscopy?FESEM?,transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?,N₂ adsorption and Raman spectrum analysis.The results clearly revealed that the three dimensional flower-like SnO₂hierarchical structure was destroyed by graphene?GN?nanosheets.However,the suitable content of Al element and GN can not only provide more active sites for the nucleation of SnO₂as well as promote the growth of SnO₂,but also obtain the smal er crystal size.The N₂adsorption isotherms indicated that GN and Al element extend the surface area of samples,which will provide a good platform for gas sensing of samples.The possible growth models for flower-like SnO₂ and S-G composites were proposed based on the microstructure characterizations.The H₂ sensing responses of all samples were investigated at low operating temperatures?OT?between 30 and 180oC.The results indicate the S-G-2?GN content was 0.004 g?based sensor exhibits the excel ent H₂ sensing response of 87.2 at a relatively low OT of 150oC,which is about 70 times higher than that of pure SnO₂.Mechanism of H₂ sensing of S-G composite has been discussed in terms of resistance change which is influenced by the Schottky barrier at the interface of S-G composites.Furthermore,in order to explore the application of S-G composite material in the field to H₂ detection,the gas sensing of a series of A-S-G samples were tested at the atmosphere of 1%H₂.2 wt%A-S-G displayed the maximum response?0.86?at low OT of 120oC,which was 1.5times as much as that of S-G.Based on the results of N₂ adsorption isotherms and XPS,the possible gas mechanism of A-S-G was explained by the electron depletion layer on the surface of SnO₂ nanorods,which caused by the adsorption of negatively charged oxygen.