Interface-Defect-Morphology Multivariable Engineering of Two-Dimensional BiOBr Nanosheets on TiO₂ Nanotube Arrays for...

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Two-dimensional (2D) metal oxide semiconductor gas sensors face challenges in sensitivity and recovery due to restacking and poor charge transport.
• Existing sensors often struggle with ppb-level detection limits and require elevated operating temperatures.
• Optimizing surface utilization and charge transport is crucial for enhancing gas sensing performance.

Purpose of the Study:

• To develop a novel 2D heterojunction material for highly sensitive and stable gas sensing.
• To investigate the synergistic effects of interface, defects, and morphology on gas sensing performance.
• To explore vacancy-mediated adsorption mechanisms for improved NO2 detection.

Main Methods:

• Fabrication of 2D BiOBr nanosheets grown on TiO2 nanotubular arrays (NTAs) to form heterojunctions.
• Characterization using Positron Annihilation Lifetime Spectroscopy (PALS) to identify defects.
• Monte Carlo simulations to analyze the adsorption behavior of curved nanosheets.
• Gas sensing performance evaluation using NO2 as a target analyte at room temperature.
• In situ Raman spectroscopy and DFT calculations to elucidate adsorption mechanisms.

Main Results:

• The BiOBr/TiO2 NTA composite demonstrated high sensitivity and a wide linear detection range (1 ppb to 10 ppm) for NO2.
• Achieved a low limit of detection (LOD) of 0.12 ppb at room temperature with excellent selectivity and stability (>60 days).
• Positron annihilation spectroscopy confirmed the presence of V_O, V_Br, and V_BrBiBr defects, enhancing NO2 adsorption.
• Monte Carlo simulations showed increased target collision frequency and adsorption probability for curved nanosheets.
• In situ Raman and DFT studies revealed vacancy-mediated NO2 adsorption and efficient charge transfer.

Conclusions:

• The synergistic effect of interface, defects, and morphology in the BiOBr/TiO2 NTA composite significantly enhances NO2 sensing performance.
• The developed material offers a promising platform for designing high-performance gas sensors operating at room temperature.
• This work provides a new strategy for preparing 2D materials with abundant active surfaces for catalytic applications.