Theoretical analysis of the NH3, NO, and NO2 adsorption on boron-nitrogen and boron-phosphorous co-doped monolayer graphene - A comparative study

Abstract

In this work, a density functional theory (DFT) based detailed theoretical study has been performed on the Boron/Nitrogen (B/N) and Boron/Phosphorous (B/P) codoped monolayer Graphene for molecular adsorptions and co-adsorptions of three Nitrogen-based environmental pollutant gasses, namely Ammonia (NH3), Nitrogen Di-Oxide (NO2) and Nitric Oxide (NO). The B acts as a localized electron deficit site in the codoped lattice and subsequently offers a suitable adsorption site for electron-enriched gas molecules like NH3 and NOx. The work systematically explores the influence of introducing Nitrogen or Phosphorus impurities in the same and different sub-lattice sites of boron-doped Graphene in the context of molecular adsorption. In this context, six doping configurations are identified that demonstrate distinct electronic properties and characteristic responses towards individual gas molecule adsorption. The molecular adsorption strongly influences the spatial distribution of electronic states near the band edges due to orbital overlaps from the adsorbed gas molecules, which leads to significant modulations in the energy band gaps and effective masses of the codoped lattices. The co-doping strategies appear highly advantageous for electrochemical gas sensing as it leads to appreciable semiconducting bandgap opening while retaining the intrinsic nature of the Graphene. The subsequent molecular adsorptions and co-adsorptions result in notable charge transfer between the gas molecules and the host lattice and considerably enhance the density of electronic states around the Fermi-level for codoped lattices.