Charge controlled capture/release of CH4 on Nb2CTx MXene: A first-principles calculation

Methane is not only the main cause of coal mine accidents but also a contributor to global warming, meanwhile, it is clean energy. It is necessary to find an advanced material which can capture methane efficiently for its utilization. In this paper, the adsorption of CH4 gas molecules on Nb2CTx(T = O, F, Cl, OH) is studied by first-principles calculation. The results indicate that the adsorption of CH4 on Nb2CTx(T = O, F, Cl, OH) is weak, and the adsorption of CH4 on Nb2C(OH)2 is the best. The calculation results of binding energy and cohesive energy show that Nb2CO2 has the best stability. The adsorption behavior of CH4 on Nb2CO2 under charge control is further studied. With the increase of negative charge state in the system, the adsorption of CH4 on Nb2CO2 is significantly enhanced, from physical adsorption to chemical adsorption; when the charge state of the system is greater than or equal to -2, Nb2CO2 can capture CH4 effectively, and the charges transferred from Nb2CO2 to CH4 mainly come from Nb atom. After the removal of the extra charge, the adsorption of CH4 on Nb2CO2 becomes weak and returns to physical adsorption state; CH4 gas molecules are easy to desorb. Therefore, Nb2CO2 can capture and release CH4 molecules by regulating the charge state of Nb2CO2, and Nb2CO2 is expected to become an excellent candidate material for CH4 capture/release.