Oxygen role in the electrochemical response of a gas sensor using ideally polarizable electrodes

In an attempt to explain the electrochemical effects observed on an origina l potentiometric gas sensor, the influence of oxygen pressure and temperatu re on the electrochemical response of the device were largely investigated The sensor consists of a solid electrolyte associated with two different el ectrodes, one in platinum the other in gold, located in the same gas mixtur e. A thermodynamic model is proposed, based first on the competitive adsorp tion of two oxygen species on the metals and second on the capacitance effe cts which may occur at the metal solid electrolyte interface. The simulatio n of the model provides a satisfactory solution if one of the oxygen specie s is considered as a metastable particle responsible for the electrostatic potential that appears at the metal-solid electrolyte interface. Additional electrostatic experiments confirm the role of oxygen in the potentials of platinum and gold which appear as ideally polarizable electrodes. (C) 1999 The Electrochemical Society. S0013-4651(98)07-011-6. All rights reserved.