Gas sensing and hydrogen storage property of Ti2CO2 doped by 3d transition-metal (V, Cr, and Co): A DFT study

High performance gas sensors and efficient hydrogen storage materials have become the current research hotspot, and MXenes have great application potential. This work presents a systemic study on the adsorption behavior of three types of gas (H2, CO, CO2) adsorbed on Ti2CO2 doped with V, Cr, and Co by using the density functional theory (DFT). The results indicated the appearance of O-vacancy defects improved the adsorption stability of CO and CO2 more significantly than transition-metal doping. Furthermore, the V-doped Ti2CO2 changed from semiconductor to be conductor after adsorbed H2, CO, and CO2 molecule. The change of band gap inducing change of conductivity could be used as signal of detecting gas, and then V-doped Ti2CO2 exhibit potential for effective gas sensors. Moreover, H2 molecule adsorbed transition-metal doped Ti2CO2 exhibited larger adsorption energies, suggesting TM-Ti2CO2 had potential for hydrogen storage. After five H2 molecules adsorbed V- and Cr-doped Ti2CO2, the two systems still maintained good adsorption capacity, which also exhibited high thermodynamic stability. The obtained results provide new idea for designing gas sensors and hydrogen storage materials based on MXenes.