Enhanced Electrochemical Reduction of CO₂ Catalyzed by Cobalt and Iron Amino Porphyrin Complexes

Abstract

Metallo-porphyrin complexes such as cobalt and iron porphyrins (CoP and FeP) have shown potential as electrocatalysts for CO 2 reduction. Here we report that introducing amino substituents enhances the electrocatalytic activity of these systems toward CO 2 reduction through a dual active site approach. We developed a flexible synthesis of Coand Fe-porphyrins having variable amino groups and found that monoamino FeP reduces CO 2 to carbon monoxide (CO) at ambient pressure and temperature with competitive turnover numbers (TONs). This efficiency enhancement approach opens a new path to designing and optimizing next generation homogeneous catalysts.

Aqueous Electrochemical Reduction of Carbon Dioxide and Carbon Monoxide into Methanol with Cobalt Phthalocyanine

“…A series of reports with transition-metal complexes were published in the 80s,which, upon assistance from aheterogeneous co-catalyst (Everittss alt) deposited on ap latinum electrode,s howed some methanol evolution. [11][12][13] Af ew papers have reported traces of CH 3 OH production when using metal complexes,i ncluding cobalt phthalocyanine (CoPc) as ac atalyst, but the exact source of the alcohol was not identified [14] and no follow-up studies were published. [15,16] Here,w ed emonstrate for the first time that CoPc is able to electroreduce CO 2 into CH 3 OH in aqueous media through aCOintermediate.Since the CO 2 -to-CO step is very efficient at aneutral pH, further optimization was focused on the CO to CH 3 OH step.Inbasic media (pH 12-13), we used pure CO as as ubstrate and discovered experimental conditions to reach an early 50-fold increase for the Faradaic efficiency (FE) towards methanol generation (from 0.3 to 14.3 %).…”

Enhanced Electrochemical Reduction of CO2 to CO upon Immobilization onto Carbon Nanotubes Using an Iron‐Porphyrin Dimer

“…[30,[35][36][37][38] Carbon nanotubes (CNTs) are of particular interest for CO 2 electroreduction owing to their high stability, conductivity and large surface area. [66] The aim of the present contribution is to improve the electrocatalytic efficiency of this system by increasing the catalyst capturing sites and functionalizing their use as heterogeneous catalysts in aqueous environment (Figure 1).Immobilization of the of iron-tetraphenylporphyrin (TPP)-Dimer (Fe-TPP-Dimer) onto multi-walled CNTs (MWCNTs) coated directly onto the electrodes exhibited remarkable electrocatalytic activity and over 92-fold enhancement of TOF for reduction of CO 2 to CO compared to their homogenous analogues. Metalloporphyrin catalysts are attractive as molecular catalysts in this field because of their robust structure and their stability to harsh conditions such as high temperatures.…”

“…Metalloporphyrin catalysts are attractive as molecular catalysts in this field because of their robust structure and their stability to harsh conditions such as high temperatures. [66] The aim of the present contribution is to improve the electrocatalytic efficiency of this system by increasing the catalyst capturing sites and functionalizing their use as heterogeneous catalysts in aqueous environment ( Figure 1). [25,27,[53][54][55][56][57] A series of low-oxidation-state homogeneous metalloporphyrins electrocatalysts for CO 2 reduction, have been reported in recent years.…”

“…The CV behavior of Fe porphyrin dimers in Figure 3b demonstrates three standard redox potentials belongs to 2e À reductions/oxidations peaks (2Fe III/II , 2Fe II/I and 2Fe I/0 ) in agreement with previous studies. As elaborated upon in previous work, [70] due to the strong stabilization of the Fe(0)-CO 2 , water (5%) was introduced to all the homogenous experiments to serve an additional proton source to facilitate CÀ O bond cleavage, represented by a subsequent increase in current density. As elaborated upon in previous work, [70] due to the strong stabilization of the Fe(0)-CO 2 , water (5%) was introduced to all the homogenous experiments to serve an additional proton source to facilitate CÀ O bond cleavage, represented by a subsequent increase in current density.…”

Homogeneous and heterogeneous molecular catalysts for electrochemical reduction of carbon dioxide

“…[20][21][22][23] Electroreduction of CO 2 RR can be completed using either homogeneous or heterogeneous catalysts. Although homogeneous catalysis have shown high selectivity, with near product unity for the production of CO and other reduction products, 18,[25][26][27][28][29] these systems are dependent on the solubility constraints of the catalysts and are limited by low current densities and instability. 30 On the other hand, heterogeneous electrocatalysts minimize the electrode and catalyst distance, allowing for more efficient processes and higher current densities at the expense of product selectivity.…”