Sensing applications of graphitic carbon nitride (g-C3N4) for sensing SO2 and SO3 – A DFT study

Abstract

Gas sensors are instruments that detects and monitors the presence of harmful and toxic gases in the atmosphere. They are an essential tool for maintaining environmental health, air quality, and safety, and their invention has prompted an extensive research and advancement in the field of gas detection. The sensing and adsorption behaviour of graphitic carbon nitride are analyzed to detect noxious gases SO2 and SO3 using density functional theory. Upon absorption of SO2 and SO3 analytes on the surface of the carbon nitride (C6N8), moderate physiorption for the SO2 analyte (−37.11 kJ mol−1), and high chemisorption for SO3 analyte (−67.90 kJ mol−1) are observed. The interaction energies depict weak van der Waals forces that is further demonstrated by the noncovalent interaction index (NCI), symmetry perturbation theory (SAPT0) and quantum theory of atoms in molecules (QTAIM) analysis. Using the natural bond orbital analysis, UV–Vis analysis, electron localization function, molecular electrostatic potential, and density of state (DOS) analysis, the electronic properties of complexes were analyzed to determine the significant impacts of the adsorption of these analytes (SO2 and SO3) on the carbon nitride C6N8. Natural bond orbital analysis revealed that charge migration occurs from the carbon nitride C6N8 surface towards the analytes (SO2 and SO3) during complex formation that are −0.032 and −0.189 e−, for SO2@C6N8 and SO3@C6N8 complexes. The analytes (SO2 and SO3) behave as electrophiles and the carbon nitride C6N8 surface serves as a nucleophilic attack in both complexes. The chemical reactivity of both complexes was shown by the development of new excited states in the PDOS spectrum. At 300 K, the recovery period was calculated by applying the transition state theory to analyze the reusability of the carbon nitride C6N8 surface. Our finding provides a theoretical foundation for the possible use of carbon nitride C6N8 surface for gas sensors targeting significant air pollutants such as SO2 and SO3 in the environment.