Non-Nernstian behavior at modified Au electrodes for hydrocarbon gas sensing

It was found that the non-Nernstian behavior of a stabilized zirconia cell using a gold (Au) working electrode for saturated and unsaturated hydrocarbon gases can be markedly enhanced by adding tantalum oxide (Ta(2)O(5)) to the Au electrode. The non-ideal emf value of the cell using the 10 wt % Ta(2)O(5)-added Au electrode for propene is typically three times the value of the cell using the parent Au electrode. The enhancing effect is explained by a promotion of the anodic reaction of propene in preference to the cathodic reaction of oxygen, which simultaneously occurs at the working electrode. The non-ideal emf value for hydrocarbons becomes more negative as the carbon number increases, the C-C linkage is unsaturated, and the chain structure is branched. The enhancing effect due to the calcination of the Au electrode at high temperatures was also studied and was found to be based on a depression of the cathodic reaction of oxygen rather than the anodic reaction of propene. (C) 1999 The Electrochemical Society. S0013-4651(99)01-077-0. All rights reserved.