Sensing capabilities of the sawtooth penta-SiC2 nanoribbon for CO2 and CO molecules based on variations in molecular density: insights from a DFT investigation

Abstract

Using Density Functional Theory (DFT) simulations, we explore the gas-sensing capabilities of the sawtooth penta-SiC₂ nanoribbon (p-SiC₂-SS) for CO₂ and CO molecules under varying concentrations. Our findings reveal that CO₂ is significantly more difficult to capture than CO. Free CO₂ adsorption occurs only when its initial distance from the adsorbent is less than 1.80 Å, and the molecule should be positioned parallel to the adsorbent. Under these conditions, the material’s electric field bends CO₂ to an angle of around 135°, inducing polarity and enabling adsorption. At low concentrations (one molecule per approximately 54 × 10⁻⁶ cm³), p-SiC₂-SS selectively adsorbs CO₂ via strong chemisorption, with an adsorption energy of approximately −1.60 eV. When the molecular concentration triples, p-SiC₂-SS sequentially adsorbs both CO₂ and CO, with the adsorption energies decreasing to approximately −0.33 eV and −0.36 eV, respectively. Additionally, the electronic properties of p-SiC₂-SS undergo distinct modifications depending on the type of adsorbed molecule. In all cases, the p orbitals of carbon and silicon atoms predominantly contribute to the energy levels near the Fermi level, with the p orbitals of carbon atoms playing a dominant role at the CBM. Our study highlights the potential of p-SiC₂-SS as an effective gas sensor, capable of detecting and distinguishing CO₂ and CO molecules, especially across different molecular concentrations.