Development of In2O3-based Sensing Materials for NO2 Detection at Room Temperature
Date
2023-04-24
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Abstract
In2O3-based chemiresistive gas sensors are extendedly employed in detecting and monitoring trace gas pollutants such as nitrogen dioxide (NO2) owing to their benefits of low cost, small size, and long lifespan. However, their applications are also limited by low sensitivity (compared to optical sensors), long response/recovery time, and the requirement of operation under high temperatures (when compared to electrochemical sensors). This study designed and fabricated three new materials to overcome these challenges. The first material is Ag nanoparticles decorated In2O3 microtubes (Ag-In2O3) derived from annealing metal-organic-framework (In-MIL-68) and loading Ag nanoparticles by chemical reduction. When the weight proportion of Ag reached 6%, the materials exhibited superior NO2 sensing performance at room temperature (RT, 20-25oC). The response is up to 60.2 to 1 ppm NO2, about 3.5 times that of the In2O3 sensor. The corresponding response/recovery time declines from 228/381 s (pure In2O3) to 157/90 s (Ag-In2O3). Its detection limit is 162 ppb. The excellent NO2 sensing properties can be attributed to the formation of heterojunction between Ag and In2O3, high surface area, and spill-over effect of Ag. The second material is constructed by MoS2 nanoflakes grown vertically on the surface of In2O3 microtubes. We found that In2O3@MoS2 composite with a 25% mass of MoS2 presents an outstanding sensing performance with a response of 39.4 to 1 ppm NO2 at RT. The response and recovery time are 72 s and 118 s, respectively, and the detection limit is 115.4 ppb. The enhanced NO2 sensing performance may benefit from p-n heterojunction at the MoS2/In2O3 interface, the increased oxygen vacancies, chemisorbed oxygen, and improved specific area and pore size distribution. The third material is synthesized through rational integration of ultrathin 2D g-C3N4 nanosheets and In2O3 nanoparticles by hydrothermal and calcination. The optimized composites demonstrated a high gas response of 325 toward 1 ppm NO2 and a short response/recovery time (115/81 s). Moreover, the prepared composites displayed excellent reproducibility, a low detection limit (18 ppb), and satisfied selectivity to NO2 at RT. The outstanding gas sensing properties might be due to heterojunction, enhanced specific surface, and enriched defects.
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Keywords
gas sensor, NO2 sensing, heterojunction, In2O3, room temperature
Citation
Liu, Y. (2023). Development of In2O3-based sensing materials for NO2 detection at room temperature (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.