Unraveling the Role of Functional Groups in Polyaniline for Ammonia Sensing: A Theoretical Approach
Abstract
One of the pressing challenges in the hydrogen energy field is the safe storage and transport of hydrogen, where leakage can pose severe risks, making the detection of hydrogen and its carriers, such as ammonia, critically important. Polyaniline (PANI), due to its tunable conductivity and chemical reactivity, has emerged as a promising material for ammonia sensing applications. This study investigates the interaction of ammonia with unfunctionalized oligomeric PANI and its functionalized derivatives (NH2- and OH-functionalized PANI) to evaluate their relative gas-sensing performance using Density Functional Theory and classical Molecular Dynamics simulations. Based on literature, NH3 sensitivity is hypothesized to follow the trend: NH2-functionalized PANI > OH-functionalized PANI > unfunctionalized PANI. Optimized geometries revealed increased reactivity and altered charge distributions due to functionalization. Molecular electrostatic potential maps and Mulliken charge analysis showed that NH2 and OH groups enhance local electron density near hydrogen bonding sites, promoting stronger NH3 interactions. Reduced density gradient and non-covalent interaction plots confirmed enhanced hydrogen bonding and van der Waals interactions, especially for NH2-functionalized PANI. Quantum Theory of Atoms in Molecules analysis revealed more and denser bond critical points for NH2-functionalized PANI. Molecular structures, radial distribution functions, and number of hydrogen bond analysis further supported this trend.