Theoretical insights into the adsorption and gas sensing performance of Fe/Cu-adsorbed graphene

Abstract

The binding mechanism of gas molecules on material surfaces is essential for understanding adsorption and sensing performance. In the present study, we examine the interaction of some volatile organic compounds (VOCs), including HCHO, C₂H₅OH, and CH₃COCH₃, on pristine graphene and its Fe/Cu-adsorbed surfaces using first-principles calculations. The results indicate that the adsorption of these molecules on graphene is regarded as physisorption, while chemisorption is observed for Fe/Cu attached surfaces. The binding of sites on molecules and surfaces primarily involves hydrogen bonds for the pure form of graphene. In contrast, stable interactions occur at functional groups such as >CO, –OH with Fe/Cu atoms, as well as CC bonds of π-rings on modified structures of graphene. It is noticeable that stronger adsorption is observed in the case of Fe addition (Gr-Fe) compared to Cu (Gr-Cu), enhancing the gas adsorption and sensing performance on graphene. Remarkably, the graphene surfaces supported by Fe and Cu improved selectivity in detecting VOC molecules, particularly C₂H₅OH and CH₃COCH₃ for Gr-Fe, and HCHO for Gr-Cu. Quantum chemical analyses reveal that the Fe/Cu⋯O/C contacts are covalent interactions, contributing significantly to the stability of configurations and sensing properties of Fe/Cu-adsorbed graphene. In summary, the observed improvements in selectivity, enhanced adsorption strength, and the identification of crucial interactions at the surface offer valuable insights into designing highly efficient gas sensors and developing advanced sensing materials.