Adsorption of C2H2, CH4 and CO on Mn-doped graphene: Atomic, electronic, and gas-sensing properties

Density functional calculations have been carried out to study the adsorption of three characteristic oil-dissolved gases in transformers (C2H2, CH4 and CO) on pristine graphene, and Mn-doped graphene (Mn-graphene) to obtain an ideal gas sensing material. First, three possible doping sites of Mn atom on graphene surface were studied, and it is found that the Bridge-doping site was the steadiest one. Then, the adsorption of gas molecules on pristine graphene, and Mn-graphene surface with different positions and orientations, were analyzed and compared by calculating the adsorption energy of each structure to obtain the most stable adsorption structures. Furthermore, density of states, and molecular orbital theory were carried out to analyze the gas sensing mechanism. The results show that pristine graphene surface shows weak adsorption to the gases. By contrast, the adsorption energy of the gases on Mn-graphene has largely increased except CH4 due to the electronic hybridization. Therefore, we concluded that the Mn-graphene could be a possible gas sensing material for C2H2 and CO detection, but not appropriate for CH4 sensing because of the weak adsorption and small conductivity change. •Pristine and Mn-doped graphene is applied to detect the characteristic dissolved gases in transformer oil: C2H2, CH4, and CO.•The Mn doping method has effectively improved the gas sensitivity and selectivity of graphene to C2H2, CH4, and CO.•This study is important to guide the experiments on preparing new gas sensor based on Mn-doped graphene material.