Enhanced Electrocatalysis of the Oxygen Reduction Reaction Using Cobalt and Iron Porphyrin/Ionic Liquid Systems

Abstract

Oxygen reduction reaction mediated by electrodes composed of graphite powder, octylpyridinium hexafluorophosphate as a binder, and cobalt and iron metal octaethylporphyrins is studied. Morphological and composition changes of the electrodic surfaces are observed employing the ionic liquid (IL) as a binder by scanning electron microscopy along with X‐ray microanalysis. Cyclic voltammetry and electrochemical impedance spectroscopy studies indicate that both the ILs and porphyrins are capable of generating an electrocatalytic effect in terms of current and/or potential toward this reaction, as well as increasing the conductive ability of the systems, presenting a synergistic effect between the ILs and the porphyrins. Scan rate studies determine that with the mixing of Co–Fe porphyrins, an oxygen reduction close to four electrons, either directly or through the production of a hydrogen peroxide intermediate, is generated.

Electrodetermination of Gallic Acid Using Multi‐walled Carbon Nanotube Paste Electrodes and N‐Octylpyridinium Hexafluorophosphate

“…The Gr and MWCNT systems present mostly carbon in their composition (over 96 %) coming mainly from the structure of both carbon materials and from the mineral oil used as binder in the carbon pastes. In addition, they show a low percentage of oxygen probably coming from the mineral oil [53]. On the other hand, the Gr/IL and MWCNT/IL systems present over 86 % of carbon, a lower percentage of oxygen in relation to the systems without ionic liquid (less than or equal to 0.8 % probably because of the decrease in the amount of mineral oil).…”

“…In addition, according to the literature [55], it is common to use the 70 : 30 (w/w) ratio in the manufacture of carbon paste electrodes based on graphite and graphene, obtaining better electrochemical responses. Similar paste electrodes have been fabricated in previous works, using the same proportion of carbon materials and binders to study the hydrogen evolution reaction [56, 57] and the oxygen reduction reaction [53], generating electrochemically stable, reproducible electrodes of conductive and mechanically resistant surfaces to neutral and alkaline pH. Specifically, the Gr/IL and MWCNT/IL systems reported in Table 1 were prepared in a 70 : 15 : 15 ratio of carbon material, mineral oil and ionic liquid in order to resist the acidic conditions in which the gallic acid determination was carried out (pH=2).…”

“…The ultrapure water (> 17 MΩ-cm) was prepared using a Direct-Q ® water purification system (Model ZRQSVP3WW) and argon gas (99.99 % pure) was purchased from AGA (Santiago, Chile). N-octylpyridinium hexafluorophosphate (OPyPF 6 ) ionic liquid was previously synthetized and characterized [53] using a general method for similar ionic liquid synthesis [54], obtaining a yield of 91 %.…”

Effect of the Metal of a Metallic Ionic Liquid (-butyl-methylimidazolium tetrachloroferrate) on the Oxidation of Hydrazine

“…The 70:30 (w/w) ratio of carbon materials and binder was used after experimentally checking that the electrodes lose their mechanical and structural consistency at different binder ratios (both higher and lower). For the manufacture of the carbon paste electrode, the bare carbon paste electrode was made by mixing multi-walled carbon nanotubes (MWCNT) and mineral oil (MO) in a 70:30 (MWCNT/MO) weight-to-weight ratio [76][77][78]. On the other hand, to manufacture the carbon paste electrodes with MWCNT and ionic liquid, a 70:20:10 (w/w) ratio of MWCNT, mineral oil, and ionic liquid were used, respectively.…”

High-Performance Organometallic Catalyst Based on Nickel Porphyrin/Carbon Fibre for the Oxygen Reduction Reaction

“…[33][34][35][36] Metalloporphyrins were used in a wide range of catalytic applications due to their unique structure, which is comprised of a transition metal at the centre of a highly conjugated 18-π-electron system. [37][38][39][40] The long conjugated aromatic system of the porphyrin enables the molecule to act as macrocyclic ligands of convenient size; that can in principle form complexes with almost all metal ions. The produced complex has a four-coordinated structure with two axial positions unoccupied.…”