CO2 gas sensor based on Pt-, Ag-, Au- and Pd-doped InSe monolayer: a first-principles study

Abstract

Through a first-principles study based on density functional theory, a physical model of CO2 gas molecule adsorption on an InSe monolayer was designed and built. The geometric structures of the InSe monolayer doped with different transition metal elements were optimized, and the spin-polarized energy band structure and magnetoelectric properties, such as the density of states, semimetallicity and magnetic moment of nanosheets with stable adsorbed phases, were calculated. The microscopic mechanism of these properties was analyzed by crystal field theory, and it was found that InSe monolayers are typical semiconductors, but transition metal–InSe monolayers can conduct electricity and are typical semi-metallic nanosheets. Second, the adsorption mechanism of CO2 gas molecule adsorption on InSe monolayers is studied. The calculation results show that when the O atom of the CO2 gas molecule is adsorbed on the surface of an InSe monolayer, the adsorption structure is relatively stable. The surface adsorption is mainly due to the transition of electrons on the InSe monolayer surface to the CO2 gas molecule. The doping of metal atoms gives CO2 gas molecules strong adsorption energy, promotes the magnetic properties of the adsorption system, and completes the transition from semiconductor to metal. The change of the work function of the adsorption system before and after doping indicates that this doping method can also enhance the sensitivity of the InSe monolayer to CO2 gas molecules.