Electrocatalytic Reduction of Oxygen at Glassy Carbon Electrodes Coated with Diazonium‐derived Porphyrin/Metalloporphyrin Films

Abstract

In this study, the influence of the film structure was investigated on the electrocatalytic oxygen reduction at GC electrodes covered with porphyrin and metalloporphyrin rings via the diazonium modification method. For that purpose, primarily, tetraphenylporphyrin (TPP) films on GC electrode surfaces were prepared by electroreduction of in situ generated diazonium salts of 5‐(4‐aminophenyl)‐10,15,20‐triphenylporphyrin (APP) and 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrin (TAPP) molecules. Next, the formation of metalloporphyrin films on the modified surfaces was accomplished through the complexation reactions of surface porphyrin rings with metal ions in the salt solutions containing Mn(II), Fe(III) and Co(II) ions. The resulting porphyrin and metalloporphyrin layers were identified with XPS and ICP‐MS. The electrochemical barrier properties of the films on GC surfaces were examined by cyclic voltammetry in K3Fe(CN)6 aqueous solution. The electrocatalytic abilities of the resulting films were also investigated for the oxygen electrochemical reduction by employing cyclic voltammetry in PBS solutions saturated with oxygen. The results showed that the oxygen reduction potentials on modified GC electrodes were shifted to less negative potentials compared to that of bare GC electrode. Also, it was obtained that the oxygen reduction reaction was more effective on the GC electrodes modified with TPP rings by using TAPP molecules than those prepared by using APP molecules.

Building Tailored Interfaces through Covalent Coupling Reactions at Layers Grafted from Aryldiazonium Salts

“…130 Kudas et al compared the ORR in pH 7 buffer at surfaces modified with Fe-, Co-, and Mn-tetraphenylporphyrin (TPP) in the edge-on configuration and found that only FeTPP catalyzed the four-electron reduction. 132 Immobilized metal complexes can also catalyze the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Le Goff et al's hydrogenase mimic, a dithiolatebridged hexacarbonyldiiron complex, showed catalytic activity for HER in a strong acid but was rapidly deactivated.…”

“…Free-base porphyrins and Pcs can also be directly grafted from diazonium ion derivatives and subsequently metallized with various ions (Scheme ). − There are several reports that grafted carboxyphenyl − and amine groups can lead to the assembly of metal–organic frameworks (MOFs), presumably through an initial coordination of metal ions.…”

“…In contrast, Marianov et al proposed that, for MnTPP assembled in the “edge-on” orientation (Scheme ), the optimum ORR performance in an alkaline medium was achieved when the surface coverage of an immobilized porphyrin allowed Mn centers to participate in multicentered redox reactions . Kudas et al compared the ORR in pH 7 buffer at surfaces modified with Fe-, Co-, and Mn-tetraphenylporphyrin (TPP) in the edge-on configuration and found that only FeTPP catalyzed the four-electron reduction …”

New insight into the electrochemical reduction of different aryldiazonium salts in aqueous solutions

“…A literature survey on electrochemical reduction of diazonium salts show that the goal of most of these studies is the reduction of the diazonium salts to produce the corresponding radical in order to modify the electrode surface (Scheme 1). [13][14][15][16][17][18][19][20][21] These studies show that the reduction of aryldiazoniums involves a single-electron transfer from the cathode to the aryldiazonium salt, resulting in the release of a nitrogen molecule and the formation of an aryl radical followed by the bond formation between the electrode surface and the aryl group. Many researchers have worked on the graing of aryldiazonium salts on different electrode surfaces, and obtained satisfactory results.…”

Recent advances in electrochemical meso- and β-functionalization of porphyrins and electrografting of diazonium porphyrins

“…and application of these electrografted tetraphenylporphyrin-based diazoniums towards the electrocatalytic reduction of oxygen [63].…”