Highly sensitive formaldehyde sensors based on catalyst added porous films fabricated by plasma spray physical vapor deposition

Highly sensitive formaldehyde sensors were developed using Pt-added porous SnO2 films deposited by plasma spray physical vapor deposition (PS-PVD). The change in the response with Pt addition and film thickness/microstructure was investigated based on the sensor model. It is found that the magnitude of the response strongly depends on both the Pt catalytic activity and the formaldehyde gas diffusion/permeation through the SnO2 film. The Pt addition enhances the increase in the film conductivity upon exposure to the gas and also accelerates the gas reaction with the SnO2 films simultaneously. Especially for the porous films, due to its high gas permeation capability, Pt catalytic effect can be effectively utilized to enhance the response, by suppressing the localized gas consumption near the film surface. As a result of the optimization of these parameters, the PS-PVD porous film sensor with Pt has shown the noticeable response to formaldehyde at a concentration as low as 20 ppb.