Ce doped SnO/SnO2 heterojunctions for highly formaldehyde gas sensing at low temperature

Highly sensitive and selective detection of formaldehyde is of great significance for indoor air quality. In this work, semiconductor gas sensors with high response have been successfully fabricated based on hydrothermally synthesized Ce doped SnO/SnO 2 nanocomposites. Gas sensing performance measurements show that the response has increased by 20 times compared with the undoped samples. In specific, the response is 22.4 toward 5 ppm HCHO at 160 °C, the response and recovery time are about 124 and 54 s, the detection limit is 70 ppb, and the selectivity over typical interfering gases such as methanol, ethanol, isopropanol and acetone is good. The improvement of gas sensing performance can be ascribed to the synergetic effect of higher surface area and more chemisorbed oxygen which comes from the addition of Ce and the p-n heterojunction formed between SnO and SnO 2 . The involved mechanism is investigated by in-situ infrared reflectance spectroscopy where abundant intermediates of HCHOO, HCOO - and CO 3 2- are observed. It is expected that the proposed Ce doped SnO/SnO 2 based sensor can make a good reference for the development of high-performance gas sensors. • Ce doped SnO/SnO 2 composites show good formaldehyde-sensing properties at low temperature. • Ce doped SnO/SnO 2 samples are characteristic of a n-type semiconductor. • The improved sensing performance was ascribed to the combination of higher surface area and more chemical adsorbed oxygen. • Intermediates of HCHOO, HCOO - and CO 3 2- are observed during the sensing process.