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

Abstract

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.

Two-Dimensional Zinc Oxide Nanostructures for Gas Sensor Applications

“…Jones and Maffeïs [79] used ZnO nanosheets to create a mathematical model of the surface reactions of CO on this material. The ZnO nanosheets were produced by thermal decomposition at 500 • C of layered basic zinc acetate, synthesized by a microwave method.…”

Investigation into the effects of surface stripping ZnO nanosheets

“…Zinc Oxide (ZnO) is a wide band gap (3.37 eV) metal oxide piezoelectric semiconductor that has the ability to be formed in numerous nanostructures including nanowires, nanorods and nanosheets [1][2][3]. Due to their high surface area to volume ratio, polycrystalline ZnO nanosheets have been shown to have potential practical application in gas-sensing devices and dye-sensitised solar cells [4][5][6].…”

Gas sensing properties of YMnO3 based materials for the detection of NOx and CO

“…The presence of peaks related to oxygen chemisorption can be very important since traditionally, in the literature, the low temperature chemoresistive behavior is fully explained by the presence of highly reactive surface chemisorbed Oions [23][24]. On the other hand, it was recently pointed out that in many cases the sensor response is partially or completely due to direct chemisorption of the target gas on the surface [26][47-50].…”

“…The second one, which is the most used by the researchers to model the chemoresistive behavior (see, e. g., [23][24]), is an irreversible oxidation of CO that consumes a pre-adsorbed oxygen releasing the electron trapped by this latter (consuming probably a hole): the resistance grows due to an increase of Ns related to a decrease of the density of surface negative charged species (see Eqs. ( 3) and ( 4)), as well as a decrease of the hole density.…”

“…To validate some of these hypotheses, a model has been developed for the transient chemoresitive response in simple chemical conditions (presence of a single gas). We model the observed chemical responses using a model similar to others presented in the literature (see, for example, [23][24][25][26] and references therein).…”