Enhanced gas sensing properties for formaldehyde based on ZnO/Zn2SnO4 composites from one-step hydrothermal synthesis

Highlights: • Lamellar ZnO/Zn₂SnO₄ composites were prepared by one-step hydrothermal method. • The amount of NaOH influenced the composition and structure of the products. • The composites exhibited superior sensing performance towards formaldehyde. • The mechanism of the improved gas sensing performance was discussed. -- Abstract: Formaldehyde gas sensor with high performance is indispensable for monitoring indoor air quality. Exploring novel nanostructured composites as gas sensing materials is considered to be a feasible way to enhance the sensing performance. In this work, one-step hydrothermal method was employed for facile synthesis of ZnO/Zn₂SnO₄ nanocomposites and the as-prepared sample took on a homogeneous hexagonal lamellar nanostructure with a diameter of 600 nm–900 nm and thickness of about 100 nm. Gas sensing properties of the sample were tested and the results demonstrated that the ZnO/Zn₂SnO₄ composites possessed excellent sensing performances to formaldehyde. At 160 °C, the ZnO/Zn₂SnO₄ composites based sensor exhibited a high response of 22.5 towards 100 ppm of formaldehyde and a detection limit as low as 500 ppb. Compared with pristine Zn₂SnO₄ and ZnO, ZnO/Zn₂SnO₄ composites showed higher sensitivity (increased by 80% and 120%), better selectivity and lower detection limit. The noteworthy improvement of formaldehyde sensing performances could be attributed to the synergetic effect as well as the formation of n-n type heterojunctions between Zn₂SnO₄ and ZnO. The mechanism involved in gas sensing performance of ZnO/Zn₂SnO₄ composites was also discussed.