Valorizing carbon dioxide via electrochemical reduction on gas‐diffusion electrodes

Abstract

The electrochemical carbon dioxide (CO2) reduction provides a means to upgrade CO2 into value‐added chemicals. When powered by renewable electricity, CO2 electroreduction holds the promise of chemical manufacturing with carbon neutrality. A commercially relevant CO2 electroreduction process should be highly selective and productive toward desired products, energetically efficient for power conversion, and stable for long‐term operation. To achieve these goals, designing gas‐diffusion catalytic electrodes and prototyping reactors built upon in‐depth understandings of the reaction mechanisms are of paramount importance. In this review, the fundamentals of gas‐diffusion electrodes are briefly presented. Then, the most recent advances in developing high‐performance CO2 reduction using gas‐diffusion electrodes are overviewed. Reactor engineering aiming at enhancing productivity, energy efficiency, CO2 single‐pass utilization, and operating lifetime is further discussed. Challenges in developing CO2 electroreduction systems are included. The prospects for advancing CO2 electroreduction toward practical applications are also narrated.

A coupled electrocatalytic system with reduced energy input for CO2 reduction and biomass valorization

“…Membrane-electrode-assembly (MEA) flow reactor with zero-gap configuration is known for minimizing the Ohmic resistance. 47,48 Therefore, a MEA flow reactor was constructed for converting CO 2 into formate paired with biomass upgrading using Cu 1 Bi and NiCoLDH/NF as cathodic and anodic catalysts, respectively (Fig. 5a).…”

Close to 90% Single-Pass Conversion Efficiency for CO2 Electroreduction in an Acid-Fed Membrane Electrode Assembly

“…The great potential of the electrochemical CO 2 reduction reaction (CO 2 RR) in fostering our transition toward a carbon-neutral economy has been increasingly recognized over recent years. − To effectively leverage this technology requires the rational design of electrocatalyst materials and devices to enable the reaction under industrially relevant conditions. Gas diffusion electrode (GDE) based electrolyzers such as flow cells or membrane electrode assemblies (MEAs) have been demonstrated to circumvent the CO 2 mass transport limit in aqueous solution and thereby achieved a CO 2 RR current density in excess of 1 A cm –2 . − However, most current studies have been carried out in neutral and sometimes alkaline electrolytes, in which the high current density often creates a strongly alkaline microenvironment at the cathodic interface. This, on the one hand, favors the CO 2 RR over the competing hydrogen evolution reaction (HER) and facilitates the C–C coupling to C 2+ products − and, on the other hand, consumes a major fraction of the CO 2 feed. − The undesirable reaction between CO 2 and OH – produces (bi)­carbonate (CO 3 2– or HCO 3 – ) that subsequently crosses the anion exchange membrane (AEM) to the anode, reacts with H + from the oxygen evolution reaction (OER), and is converted back to CO 2 in the anode tail gas, giving rise to a low theoretical single-pass conversion efficiency (i.e., the fraction of CO 2 converted into products) of 50% for two-electron-reduction products (e.g., CO and formic acid) and an even lower efficiency for C 2+ products.…”

Electrochemical C–N coupling of CO2and nitrogenous small molecules for the electrosynthesis of organonitrogen compounds

“…Compared with the conventional H-type cell, the significant difference in the flow cell is the GDE configuration, which allows the coexistence of the gas, liquid, and solid phases by exposing one side to the feeding gas and the other side to the electrolyte. [89][90][91][92][93] However, the flow cell also has some drawbacks, as follows: 24 (1) relatively high resistance due to the existence of two compartments; (2) GDE flooding, carbonate formation, and crossover issues; and (3) cost disadvantages due to the use of a large amount of electrolytes, especially alkaline electrolytes. These disadvantages lead to significant uncertainty for the industrial production of flow cells.…”