The influences of reductant concentration and Pd loading on the response and recovery times and the sensitivity in detecting hydrogen of Pd/Nafion electrodes prepared by an impregnation-reduction method were investigated in this study. The Pd/Nafion electrodes with a Pd loading of 6.90 mg/cm2, obtained at 0.006 M Pd(NH3)4Cl2 and 0.06 M NaBH4, show the maximum sensitivity of 0.0519 μA/ppm in the H2 concentration range 0-4410 ppm. However, the Pd/Nafion electrodes with a Pd loading of 11.42 mg/cm2, obtained at 0.01 M Pd(NH3)4Cl2 and 0.06 M NaBH4, show the fastest response and recovery speed in sensing hydrogen. Generally, the response time decreases with an increase of the hydrogen concentration, but the recovery time increases with an increase of the hydrogen concentration. A sensing model is also proposed to illustrate the sensing phenomenon.
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