Phenol electrooxidation on Fe–Co3O4 thin film electrodes in alkaline medium

Fe–Co3O4 thin film with different amounts of Fe have been used for the electro-oxidation of phenol in alkaline medium at room temperature. The electrodes were prepared by coating stainless steel supports with successive layers of the oxides, obtained by thermal decomposition at 673 K. The electrolysis was carried out at constant potential and the phenol disappearance, during the electrolysis, was monitored by UV–Vis absorbance measurements between 250 and 500 nm. After 3 h of electrolysis, the intermediates were identified by comparing the HPLC data and UV–Vis spectra to those from pure standards. The results indicate that the same oxidation products are formed on the different prepared electrodes, namely the decomposition products of phenol such as benzoquinone, hydroquinone and cathecol in basic medium. Simulated results show clearly the decrease of the amount of phenolic species with the electrolysis time. An enhancement of the phenol removal is observed with the presence of iron in the oxide. Under the operating conditions, around 30% of the initial phenol has been removed at ca. 3 h and the complete degradation is obtained after 54 h of electrolysis, when Fe–Co3O4 thin film with 10% of Fe is used as anode.

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► Complete removal of phenol was achieved using Fe–Co3O4 anodes after 54 h of electrolysis.
► Benzoquinone, hydroquinone and catechol are the main by-products of phenol in alkaline medium.
► The presence of Fe improves the Fe–Co3O4 activity towards the phenol electrooxidation.