Measuring the adsorption of ethanol on aluminium oxides using odd random phase multisine electrochemical impedance spectroscopy

The adsorption of self-assembling organic monolayers (SAM) on oxides frequently involves the use of an organic solvent. However, the influence of this solvent on the oxide chemistry is never taken into account in SAM adsorption studies. Nevertheless, it is necessary to investigate its dynamics, as they might exhibit a competitional behaviour with respect to the later adsorption of organic SAM's. In this study, the adsorption of the ethanol solvent on aluminium oxides is monitored. Due to the dynamic behaviour of the investigated system, odd random phase multisine electrochemical impedance spectroscopy has been employed (ORP EIS). A model was developed and statistically proven to be correct. The adsorption of ethanol molecules to form ethoxides on the surface was shown. Because of this reaction, hydroxyl groups of the oxide are being consumed, leading to changes in the oxide layer capacitance. This approach enables us to perform well founded studies of the adsorption of organic SAM's on oxides, as the influence of the solvent on the bare material is fully explored and known.

► An in-situ approach to characterise the influence of ethanol on oxides is described.
► A model is proposed, which is statistically proven to be correct.
► Trends of the fitted parameters were recognised and in accordance with literature.