Hydrothermal Synthesis of SnO₂ with Different Morphologies as Sensing Materials for HCHO Detection

Morphology regulation is an effective strategy for improving the sensor sensitivity of transition metal oxide nanostructures. In this work, SnO₂ with three different morphologies (nanorods, nanoparticles, and nanopillars) has been synthesized by a simple one-step solvothermal process with the addition of various solute ratios at 180 °C for 6 h for detecting formaldehyde (HCHO) at the optimum working temperature of 320 °C. Compared to nanorods and nanopillars, the created SnO₂ nanoparticles exhibit a much faster response time and sensitivity than other samples, showing the fastest recovery time (18 s) with the highest sensitivity of 6-100 ppm of the HCHO gas. The sensing mechanism of the sensors is investigated by Brunauer-Emmett-Teller (BET) methods and X-ray photoelectron spectroscopy (XPS) analysis, revealing that the pore size distribution and amount of O_V and O_C improve the charge transfer and HCHO adsorption of nanoparticle sensors. Such an effect of morphology control on sensing performance paves an idea for the development of different structure-based HCHO sensors.