First principle study of the adsorption of formaldehyde molecule on intrinsic and doped BN sheet

The adsorption properties of formaldehyde molecules adsorbed on pristine and doped BN sheet systems were investigated by the first principles method within the density functional theory. The most stable adsorption configurations, adsorption energy, charge transfer, energy band and density of states of pure and doped BN sheets-formaldehyde system were calculated. The results show that the adsorption capacity of BN sheet system doped with S or Al is significantly higher than that of pristine BN sheet. The conductivity of Al, S doped BN-CH2O system is increased due to the tailored energy band gap and/or the introduced impurity levels in the energy band gap by Al, S doping. As a result, Al, S doping accelerates the response of BN sheet to formaldehyde gas and improve the sensitivity of BN sheet as sensor electrode material to formaldehyde gas. The charge transfer between BN sheet and formaldehyde is significantly increased due to the Al, S doping, which leads to the changed carrier concentration and the improved conductivity. The recovery time calculations indicated that formaldehyde molecules desorption from the S doped BN sheet would be unrealistic at room temperature, while the Al doped BN sheet is suitable for formaldehyde molecules detection because of appropriate recovery time at ambient temperature for recycle use. Combination of results of theoretical analysis, we concluded that the Al doped BN sheet may be a good strategy for improving the sensitivity of these sheets toward formaldehyde molecules, while the S doped BN sheet can be as a gas adsorbent for formaldehyde molecules removal from specific environments. The effect of P-doping on BN sheet-formaldehyde system is very slight. Therefore, the present theoretical studies can help us find a suitable way for detection or monitoring the toxic gas formaldehyde molecules by using doped BN sheet.