Adsorption and sensing performances of the greenhouse gas molecules (HCOH, CO, H2S, CH4 and SO2) by the pristine and metal(M)-doped germanene (M = Rh, Cr and Mo) monolayers: A DFT investigation

Abstract The structural stability and electronic properties of pristine germanene (Ge55) and metal(M)-doped germanene nanosheets (M = Mo, Rh, and Cr) were systematically investigated using the PBE functional with Grimme’s dispersion correction. In addition, their gas sensing performances towards greenhouse gas molecules, including HCHO, CO, H 2 S, CH 4 , and SO 2 , were evaluated. The results demonstrate that metal doping significantly enhances the adsorption capability of germanene. The calculated adsorption energies range from – 0.671 eV to – 2.191 eV, confirming a chemisorption mechanism. Moreover, Mo- and Cr-doped Ge55 monolayers exhibit high sensitivities (88.7–802.1%) toward most target molecules, except for the relatively low response of CrGe55 to HCHO (33.6%). In contrast, Rh-doped Ge55 shows moderate sensitivities, with notable improvements for H 2 S and HCHO detection. The recovery times of adsorbed molecules on Mo/CrGe55 monolayers are extremely short (4.1 × 10 –3 – 3.3 × 10 –9 s), facilitating rapid regeneration of the adsorption sites, except in the case of CO adsorption on MoGe55, where a significantly longer recovery time (4.9 × 10 5 s) was observed. These findings highlight Mo- and Cr-doped germanene monolayers as promising candidates for high-performance and reusable nanosensors for toxic gas detection.