Influences Of Oxygen-Containing Groups On The Humidity Response Of Graphene Oxides

Graphene and its derivatives show significantly stronger performance than other materials in the field of humidity sensing due to their high specific surface area and unique structural characteristics.As a derivative of graphene,graphene oxide(GO)has good hydrophilicity and rich active sites,which has great application potential in the field of humidity sensing.The oxygencontaining functional groups in GO have an important influence on its interlayer spacing,hydrophilicity and humidity sensing performance,but the corresponding relationship in the field of humidity is still unclear.In order to further understand the type and number of oxygen-containing functional groups in graphene oxide and the role of different size specifications in the humidity sensing process,the following aspects were studied in this thesis :In order to explore the influence of oxygen-containing functional groups on the response of GO humidity sensing,in this paper,three kinds of graphite of 80-120 mesh,325 mesh and 8000 mesh were selected,and GO-80,GO-325 and GO-8000 samples containing-COOH,-OH,-C-O-C-,-C = O were prepared by oxidation.The O : C of the three samples reached 47.25%,47.75%and 48.26%,respectively.As the sample size decreases,the interlayer spacing increases and the conductivity decreases.When the humidity increased from15% to 92%,the interlayer spacing of the samples increased from 9.01 ?,9.42 ? and 9.57 ? to 12.12 ?,12.60 ? and 13.22 ?,respectively,with an increase of 34.52%,33.76% and 38.14%,respectively.The response time and recovery time at 92 % RH were 6 s,3 s,2 s and 12 s,28 s,48 s,respectively.This is because with the increase of oxygen-containing functional groups,the conductive structure of graphite is destroyed,more active sites appear,and the hydrophilicity and resistivity are enhanced.The response sensitivities were 97.03%,98.69% and 98.48%,respectively.On the whole,GO-8000 shows the best comprehensive performance in humidity sensing.On the whole,GO-8000 shows the best comprehensive performance in humidity sensing.Among the oxygen-containing functional groups,-OH has the greatest influence on the hydrophilicity and resistance of the sample,while-COOH has the least influence on the hydrophilicity and resistance of the sample.Due to the higher oxidation degree and more oxygen-containing functional groups of GQDs and their own size limitation effect,GQDs have better performance at low and medium humidity(15～57% RH),which is more suitable for humidity detection at low and medium humidity.