Ni-Decorated B12N12 Nanocages as High-Performance Platforms for Reversible NH3 Sensing: A Comprehensive DFT Study

Selective and reliable NH3 detection under realistic environmental conditions remains a major challenge for next-generation chemiresistive gas sensors. Herein, density functional theory (DFT) calculations were employed to systematically investigate six Ni-decorated B12N12 nanocage configurations to identify the optimal active site for ammonia sensing. Among the investigated systems, Ni@b66 exhibited the best sensing performance, combining moderate adsorption strength (Eads = -0.82 eV), pronounced band-gap modulation (Δgap = 42.8%), and rapid recovery (τ = 3.74 s at 298 K). PDOS, ELF, CDD, and CDA analyses revealed a donor-acceptor charge-transfer mechanism responsible for the observed electronic and optical responses. Unlike conventional theoretical studies, the sensing mechanism was further validated under realistic conditions through explicit-water molecular dynamics simulations, structural analyses between 173 and 373 K, competitive NH3/H2O/O2 adsorption, and multicomponent atmospheres containing O2, N2, CO2, H2O, and CH4. The negligible influence of atmospheric O2, despite its abundance and reactivity, highlights the robustness and selectivity of the proposed sensor. Benchmark calculations further confirmed the reliability of the computational methodology. These findings establish Ni@b66 as a promising boron nitride-based NH3 sensor and provide practical design principles for realistic gas-sensing applications.