Designing a high-performance gas sensor to efficiently detect the hazardous NH₃ molecule is beneficial to air monitoring and pollution control. In this work, the first-principles calculations were employed to investigate the adsorption structures, electronic characteristics, and gas sensing properties of the pristine and B-, N-, P-, Al-, and Si-doped penta-graphene (PG) toward the NH₃, H₂S, and SO₂ molecules. The results indicate that the pristine PG is insensitive to those toxic gases due to the weak adsorption strength and long adsorption distance. Nevertheless, the doping of B, N, Al, and Si (B and Al) results in the transition of NH₃ (H₂S and SO₂) adsorption from physisorption to chemisorption, which is primarily ascribed to the large charge transfer and strong orbital hybridizations between gas molecules and doping atoms. In addition, NH₃ adsorption leads to the remarkable variation of electrical conductivity for the B-, N-, and Si-doped PG, and the adsorption strength of NH₃ on the B-, N-, and Si-doped PG is larger than that of H₂S and SO₂. Moreover, the chemically adsorbed NH₃ molecule on the N-, B-, and Si-doped PG can be effectively desorbed by injecting electrons into the systems. Those results shed light on the potential application of PG-based nanosheets as reusable gas sensors for NH₃ detection.

The emission of toxic gases from industrial production has intensified issues related to atmospheric pollution and human health. Consequently, the effective real-time monitoring and removal of these harmful gases have emerged as significant challenges. In this work, the density functional theory (DFT) method was utilized to examine the adsorption behaviors and electronic properties of the Ni-decorated InSe (Ni-InSe) monolayer when interacting with twelve gases (CO, NO, NO₂, NH₃, SO₂, H₂S, H₂O, CO₂, CH₄, H₂, O₂, and N₂). A comparative assessment of adsorption strength and sensing properties was performed through analyses of the electronic structure, work function, and recovery time. The results show that Ni doping enhances the electrical conductivity of the InSe monolayer and improves the adsorption capabilities for six toxic gases (CO, NO, NO₂, NH₃, SO₂, and H₂S). Furthermore, the adsorption of these gases on the Ni-InSe surface is characterized as chemisorption, as indicated by the analysis of the adsorption energy, density of states, and charge density difference. Additionally, the adsorption of CO, NO, NO₂, and SO₂ results in significant alterations to the bandgap of Ni-InSe, with changes of 18.65%, 11.37%, 10.62%, and −31.77%, respectively, underscoring its exceptional sensitivity. Moreover, the Ni-InSe monolayer exhibits a moderate recovery time of 3.24 s at 298 K for the SO₂. Consequently, the Ni-InSe is regarded as a promising gas sensor for detecting SO₂ at room temperature. This research establishes a foundation for the development of an Ni-InSe-based gas sensor for detecting and mitigating harmful gas emissions.