Electrochemical CO₂ Reduction to Methane by Cu Complex‐Derived Catalysts in Non‐Aqueous Media

Abstract

Electrochemical CO2 reduction using Cu complex catalysts in non‐aqueous media leads exclusively to carbon monoxide or formic acid. This study reports highly selective electrochemical CO2 reduction to methane using a 2,9‐dimethyl‐1,10‐phenanthroline Cu2+ complex in dimethylformamide. XRD reveals the formation of a Cu complex‐derived catalyst during the electrochemical testing, containing Cu and an organic phase when the electrolyte contained tetrabutylammonium cations. Insulating carbonates were preferentially deposited when the electrolyte contained alkali metal cations, leading to low Faradaic efficiency for methane. The dramatic electrolyte dependence is explained by the relative solubility of deposits in dimethylformamide under reductive potentials. The Faradaic efficiency for methane production varied from sample to sample, with underlaying variation in the morphology of the catalyst. Selective methane production using Cu complex‐derived catalysts in non‐aqueous media is intriguing, opening the possibility of combinatorial studies of the effect of ligand structures on product selectivity by involving ligands not soluble in water.

Catalytic Decomposition of an Organic Electrolyte to Methane by a Cu Complex-Derived In Situ CO2 Reduction Catalyst

“…The Cu complex-derived catalyst performed selective ethylene production . As we have shown previously, the catalyst layer consisting of metallic copper and possibly an organic phase was in situ deposited during the chronoamperometric testing under a CO 2 atmosphere . The in situ formation of the catalyst layer was followed by CV measured repeatedly during chronoamperometric testing every 5–10 min (Figure b).…”

“… 29 As we have shown previously, the catalyst layer consisting of metallic copper and possibly an organic phase was in situ deposited during the chronoamperometric testing under a CO 2 atmosphere. 21 The in situ formation of the catalyst layer was followed by CV measured repeatedly during chronoamperometric testing every 5–10 min ( Figure 1 b). The CV curves show new redox peaks appearing at −1.4 and −1.65 V attributed to the in situ deposition of a Cu complex-derived catalyst starting after 5 min and with gradually increasing peaks up to 50 min.…”

“…11 Recently, we developed a Cu complex-derived catalyst, consisting of a metallic Cu phase and possibly a polymeric organic phase, deposited in situ during the electrolysis of a dimethyl-substituted phenanthroline (2,9-dimethyl-1,10-phenanthroline−neocuproine, dmp) Cu 2+ complex dissolved in 0.1 M tetrabutylammonium perchlorate (TBAP)/DMF solution with 0.1 M water. 21 The Cu complex-derived catalyst performed highly selective (up to 80% FE) methane production. The amount of CH 4 produced under a CO 2 atmosphere using an uncoated carbon paper electrode was negligible at the same applied potential.…”

Electrocatalytic and Photocatalytic CO2 Methanation: From Reaction Fundamentals to Catalyst Developments

“…[3] To address the challenge, carbon capture and utilization (CCU) technology, which aims to capture and convert CO 2 into valuable products, has been considered a viable strategy to reduce CO 2 emissions and provide new economic opportunities. [4] Among the fuel products (such as CO, [5] CH 4 , [6] CH 3 OH, [7] HCOOH, [8] and low-carbon olefins [9] ) related to CO 2 conversion, methane (CH 4 ) is an ideal choice due to its high energy density, easy compressibility and storage, and potential application as a substitute for non-renewable natural gas. [10] Compared to non-renewable energy sources such as fossil fuels, electricity can be produced via renewable energies such as wind, solar, and hydropower.…”

Effect of the Cu2+/1+ Redox Potential of Non-Macrocyclic Cu Complexes on Electrochemical CO2 Reduction

“…In addition to the metallic phase, nitrogen atoms of organic molecules are known to bind or “fix” CO 2 [ 27 ]. Coordinating ligands to Cu metal can further enhance the hydrogeneration of *CO to CH 4 before releasing CO [ 28 ]. Therefore, the chemical nature of the organic content, the coordination number of the N-containing phase of the Cu-complex-derived catalyst in particular, may also have an effect on the product selectivity and CO 2 reduction performance.…”