Amperometric H2S sensor with Pd/Au electrode by electrochemical deposition

Amperometric gas sensors fabricated with various working electrode compositions were evaluated for sensitivity to H₂S in the presence of up to 50% hydrogen. The WEs consisted of a gold thin-film deposited on to a porous membrane substrate and the gold film modified with two different loadings of palladium (0.3 and 8.1 mg/cm²). At a +800mV bias (vs. a Pb-mix reference electrode) the H₂S sensitivities in N₂ were 65.1, 16.3, 4947 nA/ppm, for pure gold, 0.03, and 8.1 mg/cm² palladium, respectively. In 1% hydrogen, the H₂S sensitivities were 38.2, 25.0, 120.9 nA/ppm for pure gold, 0.03, and 8.1 mg/cm² palladium, respectively. In 50% hydrogen the H₂S sensitivities were 32.5 and 14.4 nA/ppm for pure gold and 0.03, but at 8.1 mg/cm² palladium loading the H₂S response was not observed. Using a Pd/gold electrode increased sensitivity in air but in very high concentration of hydrogen, it was lower than the pure gold electrode.