Enhanced methane-sensing performances of Pd (monomer or dimer) decorated or doped γ-Graphyne: A DFT insight

Abstract

In the present article, the interaction of CH4 with Pd(monomer)-, Pd(dimer)-decorated or Pd-doped γ-Graphyne (γ-GYN), are explored by the dispersion-corrected form of density functional theory (DFT-D2). The most stable geometry, adsorption energy, and electronic properties including energy band structure, the density of electronic states, and negative charge transfer are presented. The obtained results present the adsorption or absorption process in Pd(monomer)-, Pd(dimer)-decorated or Pd-doped γ-GYN is a chemical type and exothermic. Because of Pd adsorption/absorption on γ‒GYN, the out-of-plane wrinkle formed on the γ-GYN plane that leads to structural asymmetry. Due to the charge transfer from Palladium atom(s) to γ‒GYN, all three compounds have become n-type semiconductor with smaller bandgaps. The CH4 adsorption onto Pd(dimer)-decorated γ-GYN, in comparison to the other two compounds, provides a greater amount of energy (about -0.554 eV), Pd(dimer)-decorated γ-GYN more efficient for a thermo-based CH4 sensor. Also, the out-of-plane wrinkles of the Pd(dimer)-decorated γ‒GYN is increased due to methane adsorption and the total negative charge transferred from methane to Pd(dimer)- decorated γ‒GYN. Owing to the significant change in the bandgap of Pd(dimer)-decorated γ‒GYN due to the adsorption of CH4, the Pd(dimer)-decorated γ‒GYN can be used in resistivity-based CH4 sensors as well.