Analysis of the kinetics of surface reactions on a zinc oxide nanosheet-based carbon monoxide sensor using an Eley–Rideal model

Herein, we experimentally test a mathematical model of the reactions on the surface of a zinc oxide nanosheet-based carbon monoxide sensor. The carbon monoxide is assumed to react with surface oxygen via an Eley–Rideal mechanism, considering only the direct reaction between the two species. We demonstrate that the measured resistance responses of the system are well described by the model, facilitating further analysis of the physical rate constants in the system. By initially considering the system in the absence of any reducing gas, it is shown that various reaction parameters may be precisely estimated. For instance, fitting the model to response curves obtained at different temperatures shows the activation energy of the reaction between oxygen ions and carbon monoxide to be 54 ± 9 kJ mol−1, whereas the recovery curves yield an estimate of 42 ± 7 kJ mol−1. Similarly, the energy barrier for the formation of oxygen ions is found to equal 72 ± 9 kJ mol−1 from the sensor response and 63 ± 10 kJ mol−1 from the recovery. These estimates are in agreement with values quoted elsewhere in the literature, corroborating the validity of the model. In the absence of surface ions, the energy difference between the Fermi level and the conduction band minimum at the surface is estimated as 590 ± 90 meV