Electrochemical CO₂ Reduction into Chemical Feedstocks: From Mechanistic Electrocatalysis Models to System Design

Abstract

The electrochemical reduction of CO2 is a promising route to convert intermittent renewable energy to storable fuels and valuable chemical feedstocks. To scale this technology for industrial implementation, a deepened understanding of how the CO2 reduction reaction (CO2RR) proceeds will help converge on optimal operating parameters. Here, a techno‐economic analysis is presented with the goal of identifying maximally profitable products and the performance targets that must be met to ensure economic viability—metrics that include current density, Faradaic efficiency, energy efficiency, and stability. The latest computational understanding of the CO2RR is discussed along with how this can contribute to the rational design of efficient, selective, and stable electrocatalysts. Catalyst materials are classified according to their selectivity for products of interest and their potential to achieve performance targets is assessed. The recent progress and opportunities in system design for CO2 electroreduction are described. To conclude, the remaining technological challenges are highlighted, suggesting full‐cell energy efficiency as a guiding performance metric for industrial impact.

Promises of Main Group Metal–Based Nanostructured Materials for Electrochemical CO2 Reduction to Formate

“…However, things become much complicated when it comes to flow cells or MEA cells. Many parameters including cell configuration, GDL, electrolyte, membrane, pressure, and temperature all greatly impact the overall cell performance, which, unfortunately, are not given as much attention as electrocatalyst materials at present . For one example, issues such as flooding or drying out of the GDL, and salt precipitate can cause cell failure before electrocatalysts reach their end of lives.…”

“…It was recently proposed that replacing the sluggish OER half reaction with less energy intensive alternatives (such as the oxidation of glycerol) could dramatically reduce the system operation cost and carbon footprint . In the future, one important task of CO 2 RR research is to better optimize the system design, and assess the electrochemical performance in terms of full‐cell figure of merit including cell voltage, cell current density, energy efficiency, and lifetime . Of course, the existing knowledge about electrolyzers and fuel cells can be readily transplanted to expedite this learning process.…”

“…At present, the stability studies of most CO 2 RR electrocatalysts in laboratory are carried out for only tens of hours at the most. Successful commercialization of this technology, however, would demand a catalyst lifetime of thousands of hours . This huge gap needs to be bridged in the near future.…”

Engineering Local Coordination Environments of Atomically Dispersed and Heteroatom‐Coordinated Single Metal Site Electrocatalysts for Clean Energy‐Conversion

“…The reaction pathway for the CO 2 RR is more complex than the electrocatalytic ORR and OER. It can produce C 1 (e.g., CO and formic acid), C 2 (e.g., ethylene and ethanol), and C 3 products (e.g., propyl alcohol and acetone) . Due to the variety of the intermediates involved, establishing suitable descriptors to guide the design of SACs for CO 2 RR remains a grand challenge.…”

Insights into the Carbon Balance for CO2 Electroreduction on Cu using Gas Diffusion Electrode Reactor Designs

“…The electrochemical conversion of CO2 into fuels and valuable chemicals under mild conditions has gained significant interest as an attractive route for the storage of intermittent renewable energy and the utilization of the captured CO2. [1][2][3][4][5][6][7][8] Over the past few decades, the focus of most CO2 reduction research has concentrated on the development of selective, efficient and stable electrocatalytsts using traditional H-cell reactors filled with CO2-saturated aqueous solutions. [9][10][11][12] Researchers have substantially reduced the overpotentials required for driving selective CO2 reduction via tuning morphologies, 13,14 compositions, 15 facets 16,17 and oxidation states of catalysts 18 .…”