Gas sensing and capturing based on the C7N6 monolayer with and without metal decoration: A first-principles investigation

We have investigated the geometrics, energetics, charge transfer, electron localization function (ELF), electron difference density (EDD), work function, electronic and gas sensing and capturing properties of the pure and metal-decorated C7N6 monolayers toward gases like NO2, SO2, NO, NH3, H2O, H2S, CO, CH4, CO2 and N2 by means of first-principles calculations. It is discovered the pristine C7N6 monolayer is not suitable for gas sensing and capturing materials. The Li decoration on the C7N6 monolayer is energetically and kinetically favorable, and remarkably enhances the adsorption strength of toxic gases (NO2, SO2, NO, and NH3), which in turn significantly influences the electronic properties (particularly conductivity) of the Li-decorated monolayer with apparent charge transfer and changes in work functions. Based on the analysis of recovery time, adsorption strength, changes in electronic properties and work function, the capture capacities and the influence of humidity on the sensing and capturing properties of NO2, SO2, NO, and NH3 on the monolayer, the Li-decorated C7N6 monolayer would be a promising potential of highly sensitive gas sensing and capturing materials for NO and NH3 gases, and an effective scavenger of NO2 and SO2 in specific scenarios in dry environment that call for experimental evaluation.