Enhanced photoelectrochemical catalysis of CO2 reduction mediated by a supramolecular electrode of packed CoII(tetrabenzoporphyrin)

Study of the Hydrogen Evolution Reaction Using Ionic Liquid/Cobalt Porphyrin Systems as Electro and Photoelectrocatalysts

In this work, the design and manufacture of graphite paste (Gr) electrodes is carried out, including N-octylpyridinium hexafluorophosphate (OPyPF6) ionic liquid (IL) as binder and modification with Co-octaethylporphyrin (Co), in order to study the hydrogen evolution reaction (HER) in the absence and presence of light. The system is characterized by XRD and FESEM-EDX (Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy), confirming the presence of all the components of the system in the electrode surface. The studies carried out in this investigation confirm that a photoelectrocatalytic system towards HER is obtained. The system is stable, efficient and easy to prepare. Through cyclic voltammetry and electrochemical impedance spectroscopy, was determined that these electrodes improve their electrochemical and electrical properties upon the addition of OPyPF6. These effects improve even more when the systems are modified with Co porphyrin. It is also observed that when the systems are irradiated at 395 nm, the redox process is favored in energy terms, as well as in its electrical properties. Through gas chromatography, it was determined that the graphite paste electrode in the presence of ionic liquid and porphyrin (Gr/IL/Co) presents a high turnover number (TON) value (6342 and 6827 in presence of light) in comparison to similar systems reported.

Improved photoelectrocatalytic effect of Co(ii) and Fe(iii) mixed porphyrins on graphite paste electrodes towards hydrogen evolution reaction

The use of light in metallic complexes has been widely studied in the photoelectrocatalytic performance of the hydrogen evolution reaction (HER).

Synthesis and investigation of tetraphenyltetrabenzoporphyrins for electrocatalytic reduction of carbon dioxide

We report the synthesis and electrochemical properties of freebase tetraphenyltetrabenzoporphyrin and its complexes of Zn(ii), Co(ii), Ni(ii), Cu(ii) and Sn(iv) towards electrochemical reduction of carbon dioxide (CO2). Based on cyclic voltammetry, it is shown that central metals significantly affect the electrocatalytic performance in the reduction of CO2 in terms of reduction potential and catalytic current enhancement. At an applied potential of -1.90 V vs. an Ag/AgCl quasi reference electrode for 20 h, the electrocatalytic reduction of CO2 realized by Zn(ii)- and Cu(ii)-tetraphenyltetrabenzoporphyrins to carbon monoxide resulted in faradaic efficiencies of around 48% and 33%, respectively.

Electrochemistry of Carbon Dioxide on Carbon Electrodes

Carbon electrodes have the advantages of being chemically inert at negative potential ranges in all media and high offset potentials for hydrogen evolution in comparison to metal electrodes, and therefore are the most suitable electrodes for electrochemistry and electrochemical conversion of CO₂ into valuable chemicals. Herein we summarize on carbon electrodes the voltammetry, electrochemical and electrocatalytic CO₂ reduction, as well as electron synthesis using CO₂ and carbon electrodes. The electrocatalytic CO₂ reduction using carbocatalyts and the future activities about electrochemical CO₂ conversion are highlighted.

A review of iron and cobalt porphyrins, phthalocyanines and related complexes for electrochemical and photochemical reduction of carbon dioxide

This review summarizes research on the electrochemical and photochemical reduction of CO 2 using a variety of iron and cobalt porphyrins, phthalocyanines and related complexes. Metalloporphyrins and metallophthalocyanines are visible light absorbers with extremely large extinction coefficients. However, yields of photochemically-generated active catalysts for CO 2 reduction are typically low owing to the requirement of a second photoinduced electron. This requirement is not relevant to the case of electrochemical CO 2 reduction. Recent progress on efficient and stable electrochemical systems includes the use of FeTPP catalysts that have prepositioned phenyl OH groups in their second coordination spheres. This has led to remarkable progress in carrying out coupled proton-electron transfer reactions for CO 2 reduction. Such ground-breaking research has to be continued in order to produce renewable fuels in an economically feasible manner.

Electrochemical behavior of electrodes modified with metalloporphyrin and multiwalled carbon nanotubes for the reduction of oxygen, proton and carbon dioxide

Iron porphyrin and cobalt porphyrin were respectively modified on glassy carbon (GC) electrodes together with multiwalled carbon nanotubes (MWCNTs), and the modified electrodes were characterized by X-ray photoelectron spectroscopy (XPS). Their electrochemical performance for the reduction of oxygen (O2) , proton (H+) and carbon dioxide (CO2) were respectively investigated and compared by cyclic voltammetry (CV). The results showed that iron porphyrin-MWCNT modified electrode always had a better performance than cobalt porphyrin-MWCNT modified electrode. It is proposed that iron porphyrin-MWCNT modified electrode will have promising application in electrochemical architectures like microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) for its good biocompatibility, easy availability, as well as excellent electrochemical performance.

Cobalt-porphyrin catalyzed electrochemical reduction of carbon dioxide in water. 2. Mechanism from first principles

We apply first principles computational techniques to analyze the two-electron, multistep, electrochemical reduction of CO(2) to CO in water using cobalt porphyrin as a catalyst. Density functional theory calculations with hybrid functionals and dielectric continuum solvation are used to determine the steps at which electrons are added. This information is corroborated with ab initio molecular dynamics simulations in an explicit aqueous environment which reveal the critical role of water in stabilizing a key intermediate formed by CO(2) bound to cobalt. By use of potential of mean force calculations, the intermediate is found to spontaneously accept a proton to form a carboxylate acid group at pH < 9.0, and the subsequent cleavage of a C-OH bond to form CO is exothermic and associated with a small free energy barrier. These predictions suggest that the proposed reaction mechanism is viable if electron transfer to the catalyst is sufficiently fast. The variation in cobalt ion charge and spin states during bond breaking, DFT+U treatment of cobalt 3d orbitals, and the need for computing electrochemical potentials are emphasized.