Comparative study on formic acid sensing properties of flame-made Zn2SnO4 nanoparticles and its parent metal oxides.

Abstract

In this work, the formic acid (CH2O2)-sensing properties of flame-made inverse spinel Zn2SnO4 nanostructures were systematically studied by comparing with its parent oxides, namely ZnO and SnO2. All nanoparticles were synthesized via single nozzle flame spray pyrolysis (FSP) in one step and verified by electron microscopy, X-ray analysis, and nitrogen adsorption to exhibit high phase purity and high specific surface area. From gas-sensing measurements, the flame-made Zn2SnO4 sensor displayed the highest response of 1829 towards 1000 ppm CH2O2 at the optimal working temperature of 300 °C compared with ZnO and SnO2. In addition, the Zn2SnO4 sensor presented a moderately low humidity sensitivity and high formic acid selectivity against several volatile organic acids, volatile organic compounds, and environmental gases. The enhanced CH2O2-sensing of Zn2SnO4 was attributed to very fine FSP-derived nanoparticles with a high surface area and unique crystal structure, which could induce the creation of a large number of oxygen vacancies useful for CH2O2 sensing. Moreover, the CH2O2-sensing mechanism with an atomic model was proposed to describe the surface reaction of the inverse spinel Zn2SnO4 structure to CH2O2 adsorption in comparison with that of the parent oxides. The results suggest that Zn2SnO4 nanoparticles derived from the FSP process could be a promising alternative material for CH2O2 sensing.