This paper reports results on a (anatase)‐based CO sensor and proposes a possible surface‐controlled sensing mechanism. The complex plane analysis of the ac electrical data provides quantitative evidence supporting the mechanism. The grain‐boundary capacitance and conductance, extracted from the impedance plane, were observed to increase with the CO concentration. This effect is attributed to a change in the depletion region thickness and barrier height at the intergranular contact. The analysis of the electrical data combined with x‐ray diffraction and x‐ray photoelectron spectroscopy observations support the proposed sensing mechanism involving CO adsorption and ionization on the titania surface, and not an oxidation‐reduction type reaction as observed in most oxide‐based sensors.
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Akbar et al. (1997) studied this question.