Highly selective and reversible 2D PtX2 (X = P, As) hazardous gas sensors: Ab-initio study

Abstract

A first principles characterization has been conducted, in order to inspect the gas sensing mechanism of penta-PtX2 (X = P, As) monolayer, for carbon monoxide (CO), carbon dioxide (CO2), methane (CH4) and ammonia (NH3). Examining the electronic properties, the quantitative and selective nature of the sensing layer has been investigated. The absence of overlapping in projected density of states (PDOS) suggests physical adsorption of the gases by the monolayers. On the basis of Bader charge analysis, the study of charge transfer mechanism suggests that the charge transferred from penta-PtX2 (X = P, As) monolayer to the CO, CO2, CH4 and NH3, is responsible for the gas sensing. The reversibility of both the monolayers has been analysed by studying the relaxation time. In case of PtP2, good amount of reversibility with 0.59 milli-sec for CO and 0.23 milli-sec for NH3, has been observed. The adsorption energies for all the gases are evocative of physical adsorption. The proper amount of adsorption of CO and NH3 with both the sensing layers boasts of their gas sensing efficiency. The variation in the work function of PtP2 and PtAs2, in presence of CO2 is 0.14 eV and 0.17 eV, respectively, making them suitable selections as CO2 gas sensor. The selective nature of PtP2 monolayer towards NH3 was confirmed by analysing the deviation in the I-V characteristics of the monolayer. Based on our findings, both PtP2 and PtAs2 monolayer are potential gas sensors for CO, CO2 and NH3 and can be used to identify gas leaks in factories or manufacturing units.