Fabrication of a humidity-resistant formaldehyde gas sensor through layering a molecular sieve on 3D ordered macroporous SnO₂ decorated with Au nanoparticles

Abstract

The development of highly-sensitive and moisture resistant semiconductor metal oxide (SMO) gas sensors for practical application remains a challenge. Here, a three-dimensional ordered macroporous (3DOM) SnO2 decorated with Au nanoparticles (NPs) was obtained via a facile self-assembly template method and the Au content was optimized. The resulting 3DOM Au/SnO2 gas sensor displayed remarkable performance, with its response and lower actual detection limit to formaldehyde 10.2 times higher and 500 times lower, respectively, compared to the undecorated 3DOM SnO2 sensor at 110 °C. Meanwhile, the fast response-recovery process and the repeatability, stability, and selectivity of the sensor indicate that it can meet the requirements for practical application. Density functional theory (DFT) calculations revealed that the Au/SnO2 NPs have strong adsorption energies and electrical conductivity, allowing for selective formaldehyde detection. Further, the 3MCM-48 layer protects the 3DOM Au/SnO2 layer from moisture, allowing at least 80 % of the initial response value to formaldehyde to be maintained even at> 90 % relative humidity. Hence, the proposed strategy represents, for the first time, a universal and effective way to achieve high response and moisture-resistant formaldehyde sensors and demonstrates the potential of SMO gas sensors for indoor air monitoring.