Facile synthesis of nitrogen doped ordered mesoporous TiO2 with improved humidity sensing properties

Highlights: • Well-designed N-doped ordered mesoporous TiO₂ were successful synthesized. • High resistance change (>10⁵) to 90% RH proves its highly application potential. • Using structure effect, doping effect and defect to explain the improved property. Long range nitrogen doped ordered mesoporous TiO₂ (N-OMT) structures having pore size 3–4 nm and wall thickness ∼2 nm were synthesized via multi-component process and then characterized by XRD, Raman spectra, BET, SEM, TEM, and XPS. Afterwards, powders of N-OMT were sprayed on the ceramic substrates with Au interdigitated electrodes to apply as humidity sensors and conduct systematic dynamic humidity sensing tests under dark conditions and room temperature via a custom-made gas-sensing test system. High resistance variation (>10⁵) towards 90% RH reveals its high sensitivity and application potential. The results indicate that nitrogen doping and mesoporous structure are synergistically conducive to enhancing the humidity sensing properties and evaporation induced self-assembly (EISA) strategy should be one of the most effective and significant approaches to prepare the higher performance humidity sensing materials. Based on the characterization and analysis, as well as the comparison with other sensors based on OMT and Commercial powders, a reasonable humidity sensing mechanism aim to explain the enhancement of N-OMT sensor's performances is discussed in detail.