Environmentally friendly recycling of SnO2/Sn3O4 from tin anode slime for application in formaldehyde sensing material by Ag/Ag2O modification

Highlights: • SnO₂/Sn₃O₄ recovered from tin anode slime is used as gas sensing material. • Ag improves the HCHO sensing properties by forming hetero-structure. • Gas sensing mechanism of the composite is thoroughly discussed. • This study is a resource-saving and environmentally friendly development. Tin anode slime, a by-product of the tin plating process composed mainly of tin oxides, offers great potential for application to the field of gas sensing. In the present study, Ag-doped SnO₂/Sn₃O₄ materials with excellent sensing properties to formaldehyde (HCHO) gas were successfully obtained by combining a simple pre-treatment method with a dipping process. The performance of the modified SnO₂/Sn₃O₄ sensing material was systemically studied by varying the Ag-dopant content. The results indicated that the sensing properties of the SnO₂/Sn₃O₄ material to HCHO were greatly improved compared to the pristine material, depending strongly on the Ag-doping content. The optimum sensing material, 2 mol% Ag/Ag₂O-doped SnO₂/Sn₃O₄, exhibited good sensing properties including a high response (12.76) to 100 ppm HCHO at a low operating temperature (160 °C) as well as a rapid response/recovery speed (5 s/5 s). The selectivity toward HCHO was also enhanced by the assistance of Ag nanoparticles. Importantly, the recovery of tin oxides from tin anode slime represents a resource-saving and environmentally friendly development.