Study of the effect of the acid-base surface properties of ZnO, Fe2O3 and ZnFe2O4 oxides on their gas sensitivity to ethanol vapor

Binary (ZnO, Fe2O3) and ternary (ZnFe2O4) gas-sensitive oxide materials are synthesized, and the correlation between their sensitivity to ethanol vapor and the functional chemical composition of the surface is studied by X-ray photoelectron spectroscopy and by the technique of the adsorption of acid-base indicators. It is found that the sensitivity to ethanol increases with increasing content of Brönsted acid sites with the acidity index pK a ≈ 2.5 and with increasing percentage of surface oxygen involved in OH/CO3/C-O groups. This interrelation is attributed to the specific features of interaction between ethanol molecules and hydroxyl groups on the surface of the oxides.