Comparison of Gas-sensitive response of three metal-doped GaNNT with Pb, Pd and Pt after adsorption of hazardous gases

Abstract

In this paper, we comparatively analyze the gas-sensing ability of Pb, Pd and Pt metal-doped GaNNT (M-GaNNT) materials for the hazardous H₂S, SO₂, NH₃ and Cl₂ gases. The adsorption structure, adsorption energy (E_ads), density of states (DOS), differential charge density and frontier molecular orbital of the M-GaNNT adsorbed hazardous gas have been studied based on the density functional theory (DFT) calculations. The results show that the energy gap of Pb-GaNNT performs the largest change with an increasing percentage change of 358 % after the Cl₂ adsorption compared with that before the Cl₂ adsorption, while the energy gap of Pt-GaNNT has the least change with an average value of 20.8 %. The doping of metal atoms can effectively improve the gas-sensitivity of M-GaNNT, and the gas-sensitivity follows the order of Pb-GaNNT> Pd-GaNNT> Pt-GaNNT. The potential applications of M-GaNNT in gas sensor and adsorbent are then predicted through the analysis of the adsorption energy, sensitive response (SR) and recovery time (τ). Pb-GaNNT performs the best Cl₂ gas removal since the largest E_ads (-5.883 eV), largest SR (4.4 × 10¹⁵) and largest τ (2.9 × 10⁸⁷s) can be determined for Cl₂ adsorption on Pb-GaNNT. Furthermore, Pb-GaNNT is a good NH₃ gas sensor since the related τ is only 2.9 s at 498 K, and a small E_ads (-1.232 eV) with large SR (9.7 × 10⁵) can be determined as well. The research findings in this paper provide a new sensor material option for both the detection and the removal of harmful gases, and the systematically theoretical method can spread to other systems.