Sensing of volatile pollutants on reduced graphene oxide-polypyrrole composite: DFT investigation

Air pollutants generated from volatile toxic chemicals pose significant public health concerns. Density functional theory (DFT) computations were used in this research to explore the efficiency and mechanism of harmful gas sensing over the reduced graphene oxide-polypyrrole (rGO-PPy) composite. Volatile molecule sensing was investigated for the NH₃, H₂CO, CH₃OH, and C₂H₅OH gas molecules over three PPy orientations on the rGO substrate. Results showed that PPy orientation over rGO plays a crucial role in the sensing efficiency of the investigated gas molecules. The rGO-PPy composite, with PPy in a vertical orientation, demonstrated higher stability and enhanced sensing than other orientations. The results indicate that the strong hydrogen bonding of NH₃ and CH₃OH with both PPy and rGO significantly enhanced the sensing of these gas molecules on rGO by influencing the charge transfer with adsorption energy values of - 0.84 and - 0.92 eV, respectively. The lack of a direct hydrogen bonding with rGO and the weak hydrogen bonding with PPy caused a weak adsorption of H₂CO and C₂H₅OH over rGO as indicated by the adsorption energy values of - 0.60 and - 0.78 eV, respectively. Selectivity analysis for the NH₃ and C₂H₅OH gas molecules showed that NH₃ can maintain hydrogen bonding with PPy in the presence of C₂H₅OH while C₂H₅OH cannot sustain this interaction. This study highlights the importance of the structural and electronic properties of the rGO-PPy composite in volatile pollutant sensing, providing insights for designing high-performance gas sensors.