Enhanced formaldehyde sensing performance based on Ag@WO3 2D nanocomposite

A novel gas sensor based on Ag nanoparticle-doped WO3 nanosheets with various doping levels was successfully fabricated via a two-step process that included a facile acid-precipitation method followed by a dipping route. The crystal structures, morphologies and composition of the as-obtained sensing materials were characterized by XRD, SEM, TEM and XPS methods. Gas sensing tests revealed that the 2 at.% Ag NPs-WO3 nanosheets possess excellent gas sensing performance for formaldehyde (HCHO). The sensitivity of the material towards 100 ppm HCHO was as high as 20.83 at an optimum operating temperature of 300 °C, which is higher than that of pure one even at lower working temperatures. Furthermore, the rapid response/recovery speeds (5 s/5 s), great selectivity and outstanding long-term stability were also exhibited for the 2 at.% Ag NPs-modified WO3 sensor. The improvement of sensing performance is related to the active space charge regions around the interface of Ag particles and WO3, and the catalytic role of Ag nanoparticles as the possible sensing mechanism was proposed. The Ag NP-decorated WO3 with superior gas sensing property is expected to be a promising candidate for formaldehyde detection in practical application and industrial production.