| Semiconductor metal oxides（SMO）are ideal gas sensing materials.The doping of SMO with g-C3N4 is beneficial to improving their gas sensing performance.In this paper,we synthesized g-C3N4-SMO（SMO=ZnO,WO3,SnO2）composites containing g-C3N4 in different weight ratios through hydrothermal method.The composites were characterized through XRD,SEM,TG-DSC,FT-IR,UV-vis,XPS and nitrogen adsorption-desorption,followed by evaluation of their gas sensing properties.The ZnO and g-C3N4-ZnO composite were synthesized by hydrothermal method.These gas sensitive materials were first characterized,followed by evaluation of their gas sensing properties.The test results showed that the optimum working temperature for g-C3N4-ZnO composite materials was reduced from 350°C to 300°C;Addition of9%mass ratio of g-C3N4 to ZnO improved the selectivity towards acetic acid gas as compared to ethanol,formaldehyde,acetaldehyde,acetone,and ammonia.A high response of 286 was obtained.The detection limit was reduced to 1 ppm.The WO3 and g-C3N4-WO3 composites were synthesized by hydrothermal method.The gas sensitive materials were characterized and gas sensing properties were evaluated.The test results show that the optimal working temperature of acetone gas for g-C3N4-WO3 composite materials is reduced from 360°C to 310°C.Out of six gases the selectivity towards acetone gas was found to be the best.Adding 2%mass fraction of g-C3N4 to WO3 improved gas sensitivity towards acetone gas,with a response of58.2.The detection limit was found to be 0.5 ppm,and the stability was found to improve.The g-C3N4-SnO2 composite gas-sensitive materials were prepared by co-deposition method.The materials were characterized and gas sensing properties tests were performed.The test results show that the optimal working temperature of acetic acid gas for g-C3N4-SnO2 composite materials is reduced from 230°C to 185°C;adding10%mass fraction of g-C3N4 to SnO2 improved gas sensitivity towards acetic acid gas,resulting in a maximum response of 87.75.Acetone gas was detected with concentration as low as 0.1 ppm.The stability was also found to improve. |
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