Photovoltaic and gas sensing properties of the novel bimetallic Janus ScNbCO 2 MXene

We report a first-principles investigation of the bimetallic Janus MXene ScNbCO2, addressing its multifunctional potential for gas sensing and photovoltaic applications. The monolayer is dynamically and thermally stable, exhibiting a semiconducting direct band gap of 1.90 eV and strong visible-light absorption enhanced by excitonic effects. Gas adsorption studies reveal selective and reversible interactions for NH3 and toluene, with adsorption energies of −0.63 and −0.66 eV and recovery times of milliseconds at 300 K, while H2O and CO display weak physisorption (−0.34 and −0.13 eV), confirming high surface selectivity. Charge density difference analysis indicates localized donor–acceptor charge transfer for NH3 and π –d coupling for toluene. Photovoltaic simulations yield power conversion efficiencies of 29.27% (Shockley–Queisser) and 20.68% (SLME with BSE), surpassing several reported Janus MXenes. These results establish ScNbCO2 as a robust and versatile 2D material for selective sensing and high-efficiency optoelectronic devices.