Electronic properties and superior CO2 capture selectivity of metal nitride (XN) and phosphide (XP) (X = Al, Ga and In) sheets

In this work, we performed ab initio calculations to investigate the structural stability, carrier mobility, and CO2 separation and capture ability of mono-layered group III nitrides (XN) and phosphides (XP) (X = Al, Ga, In). The results showed that all the six two-dimensional sheets exhibit indirect band gaps, ranging from 1.35 eV for InP to 4.02 eV for AlN by using HSE functional. Mobility calculations performed using deformation potential theory shows that the mobility is dominated by holes as compared to electrons and reaches a value of 1.7 x 10(3) cm(2-) V-1 s(-1) for AlN and 6.9 x 10(2) cm(2-) V-1 s(-1) AlP. Density functional perturbation theory was used to predict the frequency of Raman active modes, the results showed a red shift in the calculated Raman peak frequency with increase in the mass of metal ion. The calculated adsorption energy of CO2 is in the range of -0.19 eV to -0.22 eV over XN, whereas the adsorption energy varies from -0.51 eV to -1.12 eV over XP, which is larger than that of graphene and hexagonal boron nitride. The adsorption energy of CO2 on various nanostructures follows the order as E-InN > E-GaN > E-AlN and > E-InP > E-GaP > E-AlP. On the other hand, it is seen that N-2 show significantly weaker interaction with the surfaces of XN and XP as compared to CO2, indicating high selectivity of sheets towards CO2 capture.