Quantum capacitance modulation of MXenes by metal atoms adsorption

Researchers are committed to finding high-quality electrode materials to improve the performance of super-capacitors. MXenes material has attracted much attention due to its abundant functional groups on the surface. In this paper, the adsorption of H, O, F and OH groups on the surface of Ti3C2 and Ti2C was studied through first-principles calculation. It was found that the optimal adsorption site is directly above the Ti atoms of the middle layer (or the third layer). Al atom shows the best adsorption effect in the adsorption structure of metal atoms. In addition, metal atoms adsorbed on the surface of Ti3C2 and Ti2C structures terminated by F groups were also constructed. Ti3C2F2 adsorbed by Ca atom has obvious advantages under positive potential with the highest quantum capacitance value of 488.153 mu F/cm2, which can be used as an ideal cathode material for super-capacitors. Moreover, Li atom adsorbed Ti2CF2 exhibits superior quantum capacitance characteristics at the negative potential.