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/SnO2 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 degrees 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 SnO2. The involved mechanism is investigated by in-situ infrared reflectance spectroscopy where abundant in-termediates of HCHOO, HCOO- and CO32-are observed. It is expected that the proposed Ce doped SnO/SnO2 based sensor can make a good reference for the development of high-performance gas sensors