DFT-based comparative study of Li-decorated organic (C24), inorganic (B12N12), and hybrid nanocages for Cl2, COCl2, H2S, and NH3 sensing

Efficient detection of hazardous gases is crucial for ensuring environmental safety and industrial process control. This study investigates the sensing performance of Li-decorated organic (C-24), inorganic (B12N12) and hybrid nanocages (B12C6N6, B6C12N6, B6C6N12) for detecting Cl-2, COCl2, H2S, and NH3 using spin-polarized DFT calculations. Stability analysis revealed that before as well as after Li decoration, C-24 nanocage exhibited the highest stability, followed by B12N12. Among the hybrid nanocages, the stability order was B6C6N12 > B12C6N6 > B6C(12)N6. Cl-2 dissociates, COCl2 and H2S undergo physisorption, while NH3 shows chemisorption on all nanocages. Recovery time for COCl2 and H2S are within milliseconds to seconds at room temperature while for NH3 it can be achieved within seconds at 400 K under visible light exposure. QTAIM and RDG analyses reveal non- covalent interactions between the Li adatom and the gas molecules, primarily involving electrostatic and van der Waals interactions. Among all the nanocages, the band gap reduction for B12N12Li after COCl2 adsorption is 20 %, followed by B12C6N6Li at 8 %, while other gas molecules show only marginal variations, indicating lower sensitivity. Additionally, B12N12Li and B12C6N6Li demonstrate high selectivity toward COCl2 in the presence of interfering gases. Adsorption is thermodynamically favourable across a wide range of temperatures and pressures, except for COCl2 on B6C6N12, which is favourable only up to 250 K. The AIMD simulation confirms the structural integrity of B12N12Li and B12C6N6Li at an elevated temperature of 400 K. The investigation suggests that B12N12Li and B12C6N6Li are promising candidates for COCl2 sensing and can be considered for fabrication.