Adsorption of toxic gas molecules on the pre-oxidized Cu2Si nanosheet - A DFT study

Using first principles calculation, we investigated the adsorption mechanism of small toxic gas molecules (NO, NO2, NH3, CO, CO2, and SO2) by employing van der Waals (vdW) corrections to study the structural, electronic, magnetic and gas sensing properties of pre-oxidized Cu2Si nanosheet. The sensing mechanism was explored in practical oxygen-rich condition to understand its possibility as a gas sensor. All gas molecules except NO were weakly physisorbed on the pre-oxidized Cu2Si nanosheet, while NO gas molecule shows strong physisorption. It is fascinating to see that all the gas molecules except O-2 act as charge donors, and also adsorption of NO and NO2 induces small magnetic moments on the non-magnetic pre-oxidized Cu2Si nanosheet. The value of total magnetic moment for NO is 0.56 mu B/cell and for NO2 is 0.01 mu(B)/cell, respectively. It is observed that the work function increases by about 2.8% for pre-oxidized condition. Further, the adsorption of gas molecules on the pre-oxidized Cu2Si nanosheet indicates a drop in the work function for NO, CO, CO2 and rise for NO2, NH3, SO2. Admissible values of adsorption energy assure short recovery time making pre-oxidized Cu2Si nanosheet as an effective nano sensor for harmful toxic gases.