Tuning the Covering on Gold Surfaces by Grafting Amino-Aryl Films Functionalized with Fe(II) Phthalocyanine: Performance on the Electrocatalysis of Oxygen Reduction

Abstract

Current selective modification methods, coupled with functionalization through organic or inorganic molecules, are crucial for designing and constructing custom-made molecular materials that act as electroactive interfaces. A versatile method for derivatizing surfaces is through an aryl diazonium salt reduction reaction (DSRR). A prominent feature of this strategy is that it can be carried out on various materials. Using the DSRR, we modified gold surface electrodes with 4-aminebenzene from 4-nitrobenzenediazonium tetrafluoroborate (NBTF), regulating the deposited mass of the aryl film to achieve covering control on the electrode surface. We got different degrees of covering: monolayer, intermediate, and multilayer. Afterwards, the ArNO2 end groups were electrochemically reduced to ArNH2 and functionalized with Fe(II)-Phthalocyanine to study the catalytic performance for the oxygen reduction reaction (ORR). The thickness of the electrode covering determines its response in front of ORR. Interestingly, the experimental results showed that an intermediate covering film presents a better electrocatalytic response for ORR, driving the reaction by a four-electron pathway.

On the role of functional groups in the formation of diazonium based covalent attachments: dendritic vs. layer-by-layer growth

“…43 Due to its electronwithdrawing nature, the NO 2 group is well-known as a strongly deactivating group for aryl substitution, resulting in a favorable polymerization by electrophilic attack of diazonium ions on graed groups to form dendritic multilayers. 43,46,47 This is consistent with our observation of the 4-NBD moiety.…”

Effect of Support on Oxygen Reduction Reaction Activity of Supported Iron Porphyrins

“…Relatively little work addresses adsorption of Fe-containing macrocycles on noncarbon supports for ORR purposes. Co or Fe macrocycles adsorbed onto Au electrodes modified with self-assembled monolayers (SAMs) demonstrate ORR activity, albeit at somewhat higher overpotentials. − …”

Catalizadores bifuncionales basados en mezclas de porfirinas metálicas como componentes de cátodos de baterías de litio-oxígeno

“…Marianov y colaboradores 50 reportaron el efecto de la unión covalente de una porfirina de Mn en la actividad electrocatalítica de ORR y OER. Más recientemente, Olguín y colaboradores 88 reportaron la performance catalítica hacia la ORR de un sistema que contiene temas correlacionar esas propiedades electroquímicas con técnicas que permitan analizar la composición química de la superficie, como ser XPS combinada a LSV, de modo de poder asignar la performance electrocatalítica observada a las señales provenientes de los sitios activos. Otro tema a destacar es que a pesar de las ventajas que ofrece el electrografting como método de preparación de películas y de las excelentes propiedades electrocatalíticas de las FeTPP (para catalizar la ORR) y de las CoTPP (para catalizar la OER), no hay reportes en la literatura en cuanto a la utilización del electrografting de sales diazonio para desarrollar catalizadores duales bimetálicos basados en mezclas de porfirinas de Fe y Co.…”