Effective analysis of gaseous formaldehyde based on a platinum-deposited screen-printed edge band ultramicroelectrode coated with Nafion as solid polymer electrolyte

We report here the development of an electrochemical formaldehyde gas sensor based on a screen-printed edge band carbon ultramicroelectrode deposited with Pt nanoparticles and coated with Nafion as the solid polymer electrolyte. The success of the proposed formaldehyde gas sensor lies not only in electrode itself but also in proper detecting scheme. In the detection scheme, a high potential was first applied to fully convert formaldehyde to formic acid and at the same time to release active sites of the Pt catalyst. On the cathodic scan, the overlap responses from the reduction of platinum oxide and the oxidation of formic acid were effectively differentiated by forward/reverse square wave voltammetry (SWV). Simply by measuring the current response of the reverse SWV, a linear calibration curve up to 5.1 ppm formaldehyde was obtained. For six continuous measurements of 0.3 ppm formaldehyde in the gas phase, a R.S.D. of 1.5% was obtained, indicating good reproducibility of the detection system. The detection limit was calculated as 80 ppb (S/N = 3).