Under the extreme usage scenario, the thermal runaway gases (H2 and CO2) will be produced and leaked from the electrolyte of lithium battery. The molecular structure, adsorption properties, charge density difference (CDD), density of state (DOS), partial density of state (PDOS), desorption time, sensitivity, work function (WF) and frontier orbital theory are investigated to analyze the sensing characteristics toward H2 and CO2 of CdS monolayer, Ag–CdS, Pt–CdS, and Pd–CdS. The optimal CdS monolayer structure consist of hexagons, and the bandgap is 2.043 eV. After heterometal doping, the Eg decreases to 0.339 eV for Ag–CdS, 1.202 eV for Pt–CdS, and 1.358 eV for Pd–CdS. The adsorbing energy of the CdS–H2, Ag–CdS–H2, Pt–CdS–H2, and Pd–CdS–H2 is - 2.27 eV, - 0.80 eV, - 0.81 eV, and - 0.81 eV respectively, which correspond to the desorption time of 1.33 × 1026, 27.2, 40.1, and 40.1 s at 300 k in sequence. At room temperature, the response value of Pt–CdS to hydrogen is 78.61%, while the response value of Pd–CdS to hydrogen reaches as high as 98.17%. The Pt-doped and the Pd-doped CdS monolayer shows potential for room temperature H2 sensing, while the CdS monolayer displays the potential for H2 and CO2 cleaning.
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