A Simple Absorbent Cotton Biotemplate to Fabricate SnO2 Porous Microtubules and Their Gas-Sensing Properties for Chlorine

SnO2 porous microtubules (PMs) were synthesized by a two-step immersion–calcination method, and absorbent cotton is used as the biotemplate. This method is simple, eco-friendly, and cost-efficient. The absorbent cotton as a biotemplate not only supported the formation of microtubule-like structures but also provided a hypoxia atmosphere to introduce oxygen vacancies in the calcination process. The as-synthesized SnO2 PMs maintain the morphology of absorbent cotton—long, curly, and twisted. The gas-sensing property of the SnO2 PMs sensor was systematically investigated for detection of chlorine (Cl2). On the basis of such porous microtubules, the sensor exhibited excellent sensitivity and selectivity to Cl2 at 200 °C. Compared with SnO2 particles, the gas response (Rgas/Rair) of the SnO2 PMs sensor to 10 ppm of Cl2 at 200 °C was increased about 100 times. Finally, the enhanced gas-sensing performance was associated with the hollow morphology of SnO2 PMs and the formation of abundant oxygen vacancies because of the decomposition of absorbent cotton.