Ppb-Level Detection of a Formaldehyde Gas Sensor Based on the Honeycomb SnO₂/SnSe₂ Heterostructure

In this work, a low-temperature formaldehyde sensor based on a hydrothermally synthesized tin dioxide/tin selenide (SnO2/SnSe2) nanostructure was demonstrated. The SnO2 nanosheets were decorated on the SnSe2 nanoblocks. The microstructural characterization proves this unique morphology. At 150 °C, the SnO2/SnSe2 composite gas sensor exhibits more than three times the response to formaldehyde gas compared to pure SnO2, with a response of 13.47 to 10 ppm formaldehyde and a response recovery time of 63 s/12 s. In addition, the SnO2/SnSe2 gas sensor is capable of detecting formaldehyde gas at the ppb level. The sensor also exhibits excellent repeatability, excellent long-term performance stability, and resistance to humidity interference. The n–n heterojunction formed between SnO2 and SnSe2, along with its unique microstructure, significantly enhances the performance of the SnO2/SnSe2 sensor. The adsorption behavior of formaldehyde molecules on sensitive material surfaces was studied by using density functional theory.