Al and Ti-doped black phosphorus as sensitive materials for adsorption of HF and H₂S toxic gases: an <i>ab initio</i> study

This study explores the potential of aluminum (Al) and titanium (Ti)-doped black phosphorus (BP) as sensitive materials for detecting and adsorbing toxic gases, hydrogen fluoride (HF) and hydrogen sulfide (H₂S), using Density Functional Theory (DFT) calculations. The structural, electronic, and optical properties of pristine BP, Al and Ti-doped BP before and after gas adsorption were investigated. Molecular dynamics revealed the thermodynamic stability of all the substrates at room temperature. Al and Ti-doping enhanced the adsorption behavior of BP significantly. The studied adsorbents revealed both physisorption and chemisorption of the selected gases, with maximum adsorption energy of -1.651 eV for HF gas. Electronic analyses show that Ti-doping transforms BP into a metal, while Al-doping modulates the band gap, improving sensitivity. Charge distribution indicates significant electron redistribution in doped systems upon gas adsorption. Additionally, optical spectra show slight red shifts due to gas adsorption. RGD analysis revealed the presence of weak van der Waals and strong attractive interactions between adsorbents and the gas molecules. The findings indicate that Al and Ti-doped BP are promising materials for the development of highly sensitive and selective gas sensors targeting HF and H₂S molecules.