Reaction mechanisms of pristine and Cu-doped ZnO clusters with ethanol using Evans–Polanyi principle

The interaction and adsorption of pristine and copper (Cu)-doped zinc oxide (ZnO) nanoparticles of ethanol (C₂H₆O) and several other gases are calculated. These gases include carbon dioxide (CO₂), carbon monoxide (CO), ammonia (NH₃), ozone (O₃), nitrogen dioxide (NO₂) and sulfur dioxide (SO₂). Most of these gases are air pollutants. Zinc oxide wurtzoid clusters are used to represent zinc oxide nanoparticles. The Gibbs free energy and enthalpy of reactions are evaluated. The Evans–Polanyi principle is used to evaluate the activation energy that gives the best fit to the Arrhenius equation of the reaction. The results of solving the reaction rate equations are used to compare with experimental findings. The reaction of gases with air before reaching the sensor surface is included. A comparison of the calculated response time (10.5 s), recovery time (470 s) and reaction rate with available experimental results is performed (9 and 420 s, respectively) for 50 parts per million ethanol at room temperature. As these results show, the Evans–Polanyi principle combined with Arrhenius equation can give acceptable results. The response time is inversely proportional to the gas concentration, while the recovery time is linearly proportional to the gas concentration. A correlation factor can relate the reaction rate with the response.