Efficient Electrochemical Reduction of CO₂ to Formate in Methanol Solutions by Mn‐Functionalized Electrodes in the Presence of Amines**

Abstract

Carbon cloth electrode modified by covalently attaching a manganese organometallic catalyst is used as cathode for the electrochemical reduction of CO 2 in methanol solutions. Six different industrial amines are employed as cocatalyst in millimolar concentrations to deliver a series of new reactive system. While such absorbents were so far believed to provide a CO 2 reservoir and act as sacrificial proton source, we herein demonstrate that this role can be played by methanol, and that the adduct formed between CO 2 and the amine can act as an effector or inhibitor toward the catalyst, thereby enhancing or reducing the production of formate. Pentamethyldiethylentriamine (PMDETA), identified as the best effector in our series, converts CO 2 in wet methanolic solution into bisammonium bicarbonate. Computational studies revealed that this adduct is responsible for a barrierless transformation of CO 2 to formate by the reduced form of the Mn catalyst covalently bonded to the electrode surface. As a consequence, selectivity can be switched on demand from CO to formate anion, and in the case of (PMDETA) an impressive TON HCOOÀ of 2.8 × 10 4 can be reached. This new valuable knowledge on an integrated capture and utilization system paves the way toward more efficient transformation of CO 2 into liquid fuel.

Two-dimensional materials: synthesis and applications in the electro-reduction of carbon dioxide

“…Substrates functionalized by molecular monolayers are considered a type of 2D electrodes, which have been extensively studied for CO 2 electro-reduction [166][167][168][169] . For instance, Fang et al reported that a Au electrode modified with 4-pyridinylethanemercaptan(4-PEM) exhibits high CO 2 selectivity toward formate compared with pristine Au electrode [170] .…”

Heterogenised Molecular Catalysts for Sustainable Electrochemical CO2 Reduction

“…The method of immobilisation also influences the performance and efficiency of the system. Different strategies are described in the literature, such as grafting via covalent bonding, [24][25][26] immobilisation via weak interactions and physical adsorption, [27][28][29] and integration of the molecular complexes into the porous support structure. [17,[30][31][32] Each strategy has its own merits and drawbacks.…”

A Dicationic fac-Re(bpy)(CO)3Cl for CO2 Electroreduction at a Reduced Overpotential

“…For example, Mn catalysts with pendent amine bases that work as proton relays produce formate with striking turnover rates, but Re catalysts of the same ligand are much slower and largely selective for CO . Notably, the ability to tune product selectivity using simpler catalysts in the presence of amines and alcohols invokes debate over which strategy is more effective: tailoring catalysts or customizing the reaction medium. , Hydrogen-bonding groups can accelerate low overpotential protonation-first pathways for Mn catalysts; however, the benefits must be balanced against high activation barriers for the rate-determining step caused by excessive steric bulk …”