Theoretical study on structural properties and hydrogen adsorption performance of C3N doped with monoatomic Al/Li

Highlights: • Electronic, thermodynamic and H₂ adsorption performance of C₃N materials were studied by DFT. • The structural stability of the defective C₃N increased after embedding of Al and Li. • Li/V_N-C₃N has the best adsorption performance for H₂ among five C₃N materials. • When adsorbing six H₂, the absolute value of the adsorption energy reaches the maximum. • When adsorbing multiple H₂, adsorption energy of four doped C₃N materials first increases and then decreases. In this paper, density functional theory (DFT) was used to study the structural properties, charge transfer, thermodynamic stability and hydrogen storage properties of C₃N two-dimensional materials and atomic defects C₃N doped with Al and Li (Al/V_N-C₃N, Al/V_C-C₃N, Li/V_N-C₃N and Li/V_C-C₃N), respectively. The results show that Al/Li doping does not reduce the stability of C₃N structure, and C₃N, Al/V_N-C₃N, Al/V_C-C₃N and Li/V_N-C₃N have good thermal stability at room temperature (300 K). The calculation results of H₂ adsorption show that Li/V_N-C₃N has the best adsorption performance, and the average adsorption energy of single H₂ is −0.289 eV. When adsorbing multiple hydrogen molecules, the energy of the four doped C3N materials first increased from 0.2 eV to 0.5 eV and then decreased to 0.4 eV on average. The decrease is small, indicating that it was possible to adsorb more hydrogen. When adsorbing six hydrogen molecules, the absolute value of the adsorption energy reaches the maximum. Thus, four doped C₃N materials, particular for Li/V_N-C₃N, have the potential to become new hydrogen storage materials.