Metal anchoring-induced enhancement of Ψ-graphene gas sensors for CH4, CO, and CO2 monitoring

Abstract

Metal-anchored Ψ-graphene (Ψ-G@M; M = Cu, Ag, Pd, and Pt) systems were systematically investigated using first-principles calculations to assess their structural stability, electronic properties, and gas-sensing performance toward CH4, CO, and CO2. Structural analysis indicates that all metal atoms can be stably anchored on the Ψ-graphene surface, with stability following the order Pt > Pd > Cu > Ag based on formation energies and adsorption distances. Electronic structure analyses, including partial density of states (PDOS), electron density difference (EDD), Bader charge, and electron localization function (ELF), reveal stronger orbital hybridization between Pd and Pt with the C-2p states of Ψ-graphene, suggesting partially covalent interactions, whereas Cu and Ag exhibit weaker hybridization and more localized electronic distributions. All metal-anchored systems preserve the intrinsic non-magnetic character of Ψ-graphene. Gas adsorption results demonstrate that CH4 adsorption on Ψ-G@Cu, Ψ-G@Pd, and Ψ-G@Pt, CO adsorption on Ψ-G@Ag, and CO2 adsorption on Ψ-G@Cu, Ψ-G@Pd, and Ψ-G@Pt fall within the optimal adsorption energy range (-0.50 to -1.20 eV), providing a suitable balance between adsorption strength and reversible desorption for sensing applications. In contrast, the exceptionally strong adsorption of CO on Ψ-G@Cu, Ψ-G@Pd, and Ψ-G@Pt suggests that these systems are more suitable for gas capture than for reversible sensing. Work function modulation and sensitivity analyses reveal that CH4 adsorption on Ψ-G@Cu and CO2 adsorption on Ψ-G@Cu, Ψ-G@Pd, and Ψ-G@Pt exhibit sensitivity values exceeding 10%, indicating significant electronic responses upon gas adsorption. Recovery time calculations further demonstrate rapid desorption of CH4 on Ψ-G@Cu and Ψ-G@Pd, and of CO2 on Ψ-G@Cu and Ψ-G@Pd, at 300 K, suggesting excellent reversibility and fast sensing capability. Ab initio molecular dynamics simulations confirm that the sensing systems, CH4-Ψ-G@Cu and CO2-Ψ-G@Pd, remain structurally stable at both 300 K and 500 K, demonstrating strong thermal stability under operating and regeneration conditions. These findings highlight that Cu- and Pd-anchored Ψ-graphene are promising candidates for high-performance CH4 and CO2 gas sensing with high sensitivity, rapid recovery, and robust thermal stability.