Rapid and accurate detection of highly toxic NO2 gas based on catkins biomass-derived porous In2O3 microtubes at low temperature

Development of In 2 O 3 -based gas sensors has recently attracted widespread attention, however, how to shorten the response and recovery time for sub-ppm level NO 2 detection remains challenging. In this work, biomorphic In 2 O 3 sensing material (In 2 O 3 -600) was successfully prepared through simple indium chloride solution immersion and air calcination at 600 ℃ with waste catkins template. This hierarchical structure is cross-linked by uniform spherical nanoparticles with good crystallinity. Its multi-stage pores and 1-D microtube structure are conducive to promoting the rapid diffusion and desorption of target gas, and the existence of oxygen vacancy defects can also effectively increase the conductivity, active sites and the content of surface adsorbed oxygen species. Their synergism significantly improves the rapid response and recovery speed of sensor to trace NO 2 under low energy consumption. At 92 ℃, the response value of In 2 O 3 -600 sensor towards 10 ppm NO 2 is up to 193 with rapid response and recovery times (56 and 14 s), even 1 ppm for 64 and 32 s, which is significantly shorter than most reported In 2 O 3 -based sensors. In addition, the sensor also has a wide linear detection range, low detection limit, good selectivity, and satisfactory reproducibility, moisture resistance and long-term stability. Therefore, the biomorphic porous In 2 O 3 -600 microtubes are available as candidate for detecting sub-ppm level NO 2 gas at low temperature. • Porous In 2 O 3 microtubes were simply and controllably synthesized using waste catkin as bio-template. • In 2 O 3 -600 sensor exhibits rapid response and recovery times (64 s/32 s) to 1 ppm NO 2 at 92 ℃. • The synergism of unique microtube and oxygen vacancies is highly responsible for excellent sensing performance. • The simple catkin-template method provides useful reference for synthesizing other advanced metal oxide nanomaterials.