CO2 Electroreduction over Metallic Oxide, Carbon-Based, and Molecular Catalysts: A Mini-Review of the Current Advances

Abstract

Electrochemical CO2 reduction reaction (CO2RR) is one of the most challenging targets of current energy research. Multi-electron reduction with proton-coupled reactions is more thermodynamically favorable, leading to diverse product distribution. This requires the design of stable electroactive materials having selective product generation and low overpotentials. In this review, we have explored different CO2RR electrocatalysts in the gas phase and H-cell configurations. Five groups of electrocatalysts ranging from metals and metal oxide, single atom, carbon-based, porphyrins, covalent, metal–organic frameworks, and phthalocyanines-based electrocatalysts have been reviewed. Finally, conclusions and prospects have been elaborated.

Mechanism and Selectivity of Electrochemical Reduction of CO2 on Metalloporphyrin Catalysts from DFT Studies

“…A DFT-calculated E° = −1.15 V for [CoP] 0 /[CoP] − has been reported [ 40 ]. Moreover, the second reduction potentials are more negative than the corresponding first reduction potentials, indicating that the formation of [MP] 2− is less favorable and Step 4 is unlikely to happen under a typically applied potential of CO 2 reduction (−1 V to −1.5 V) [ 46 , 47 ]. Consequently, [MP] 2− is less likely to have a significant contribution to either the CO or HCOO − /H 2 cycle.…”

Revisiting Electrocatalytic CO2 Reduction in Nonaqueous Media: Promoting CO2 Recycling in Organic Molecules by Controlling H2 Evolution

“…Electrochemical CO 2 reduction is challenging due to its linear sp hybridized structure, granting high thermodynamic stability to the CO 2 molecule [18,19] and its low solubility. [19] In the aqueous system, the carbon dioxide solubility is 34 mmol L À1 (300 K, neutral pH) and may vary slightly depending on the temperature, pressure, concentration, and type of anions in the electrolyte.…”

“…Electrochemical CO 2 reduction is challenging due to its linear sp hybridized structure, granting high thermodynamic stability to the CO 2 molecule [18,19] and its low solubility. [19] In the aqueous system, the carbon dioxide solubility is 34 mmol L À1 (300 K, neutral pH) and may vary slightly depending on the temperature, pressure, concentration, and type of anions in the electrolyte. [20,21] In this sense, the main advantage of using a nonaqueous electrolyte is the higher solubility of CO 2 and the possibility of complete suppression of hydrogen evolution reaction (HER).…”

Insights of Fe2O3 and MoO3 Electrodes for Electrocatalytic CO2 Reduction in Aprotic Media

“…A wide variety of methods, such as photocatalysis, electrocatalysis, and heterogeneous catalysis, have all been successful in CO 2 reduction [ 3 ]. Factors such as solvent, electrolyte, pH, temperature, CO 2 concentration, electrode material, surface structure, and electrode potential influence the variety of products obtained [ 4 , 5 ]. Reduction products, including CO, CH 4 , and CH 3 OH, among others, have been reported [ 6 , 7 , 8 ].…”

“…In this sense, acetonitrile (ACN) is one of the most widely used non-aqueous aprotic solvents in catalysis and electrochemistry, and has been used to study the electrocatalytic CO 2 reduction [ 18 , 19 , 20 ]. Pons et al studied solutions of tetra-n-butylammonium tetrafluoroborate (TBAF) in dry ACN, finding ACN decomposition at potentials more negative than –3.0 V vs. Ag/Ag+ (0.01 M) [ 5 ]. The ACN solution containing tetrabutylammonium salts, such as the electrolyte system, TBAF (0.1 M), has been used for the study of the electrocatalytic reduction of CO 2 .…”