Molecular cobalt corrole complex for the heterogeneous electrocatalytic reduction of carbon dioxide

Abstract

Electrochemical conversion of CO 2 to alcohols is one of the most challenging methods of conversion and storage of electrical energy in the form of high-energy fuels. The challenge lies in the catalyst design to enable its real-life implementation. Herein, we demonstrate the synthesis and characterization of a cobalt(III) triphenylphosphine corrole complex, which contains three polyethylene glycol residues attached at the meso -phenyl groups. Electron-donation and therefore reduction of the cobalt from cobalt(III) to cobalt(I) is accompanied by removal of the axial ligand, thus resulting in a square-planar cobalt(I) complex. The cobalt(I) as an electron-rich supernucleophilic d 8 -configurated metal centre, where two electrons occupy and fill up the antibonding d z 2 orbital. This orbital possesses high affinity towards electrophiles, allowing for such electronically configurated metals reactions with carbon dioxide. Herein, we report the potential dependent heterogeneous electroreduction of CO 2 to ethanol or methanol of an immobilized cobalt A 3 -corrole catalyst system. In moderately acidic aqueous medium (pH = 6.0), the cobalt corrole modified carbon paper electrode exhibits a Faradaic Efficiency (FE%) of 48 % towards ethanol production.

Electrocatalytic Reduction of CO2 to Acetic Acid by a Molecular Manganese Corrole Complex

“…The resulting GC-MS spectrum for acetate showed a shift of m/z = 2 of the molecular ion peak (CH 3 COOH + , m/z = 60 to 62) due to 13 C incorpo- Angewandte ration in both carbon atoms of acetic acid (Figure 2 C). This trend is also reflected for different fragments, for example, where COOH + m/z = 45 shifts to m/z = 46 due to 13 C substitution. The fragment obtained at m/z = 43 during the reduction of 12 CO 2 corresponds to CCH 3 CO + and shifted to m/ z = 45 upon replacement with 13 CO 2 (Figure 2 C).…”

“…The D 2 O/H 2 O experiments verify that protons are incorporated via proton coupled electron transfer (PCET) in the CO 2 reduction reaction and confirms water is the proton source in the formed products. Moreover, CPE measurements with 13 CO 2 were performed to confirm the carbon source. The resulting GC-MS spectrum for acetate showed a shift of m/z = 2 of the molecular ion peak (CH 3 COOH + , m/z = 60 to 62) due to 13 C incorpo- Angewandte ration in both carbon atoms of acetic acid (Figure 2 C).…”

“…At this step, the reaction can take different routes one of which is another PCET on carbon site to form COOH (D) 12 CH 3 OH (E) 13 CH 3 OH. F) 1 H-coupled-13 C-NMRspectrum in 13 CO 2 saturated phosphate buffer (pH 6) after 5 h CPE at À1.25 V vs. Ag/AgCl under 13 CO 2 saturation.…”

Electrocatalytic Reduction of CO2 to Acetic Acid by a Molecular Manganese Corrole Complex

“…The D 2 O/H 2 O experiments verify that protons are incorporated via proton coupled electron transfer (PCET) in the CO 2 reduction reaction and confirms water is the proton source in the formed products. Moreover, CPE measurements with 13 CO 2 were performed to confirm the carbon source. The resulting GC-MS spectrum for acetate showed a shift of m/z = 2 of the molecular ion peak (CH 3 COOH + , m/z = 60 to 62) due to 13 C incorpo-…”

“…13 % at À0.95 V vs. RHE). [13] In this study we focus on the design of manganese corroles as potent electrocatalysts for CO 2 reduction. Manganese(III) corroles are square-planar complexes and initially possess no axial ligand coordination compared to the Co III (-L) corroles (e.g., L = triphenylphosphine or pyridine), which renders the complex freely accessible towards axial coordination by nucleophiles (e.g., H 2 O or OH À ).…”