Electrode Engineering for Electrochemical CO₂ Reduction

Abstract

Excessive carbon dioxide emissions cause severe global warming issues. One efficient way to deal with the problem is to convert CO 2 into valuable fuels and chemicals. The electrocatalytic carbon dioxide reduction reaction (CO 2 RR) has an excellent potential to reduce carbon emissions. Over the past few decades, research in this field has focused on creating highperformance catalysts. However, the overall efficiency of the CO 2 RR process is limited at the device level, such as slow CO 2 mass transportation causing insufficient current density output, which is an urgent issue to be overcome in the design of advanced CO 2 RR electrolyzers. Recently, gas diffusion electrodes have been intensively investigated to raise the CO 2 RR performance into commercially relevant current densities by boosting the CO 2 mass transport rate. This review focuses on recent research progress on electrode engineering for increasing the CO 2 RR performance, along with electrode-stabilizing strategies for long-term CO 2 electrolysis. Future directions are proposed to accelerate the development of advanced electrodes for industrial CO 2 electrolyzers.

Enhancement of CO2RR product formation on Cu-ZnO-based electrodes by varying ink formulation and post-treatment methods

“…Interestingly, similar observations were also made for fuel cell inks in the context of polymer electrolyte membrane fuel cells [26]. Additionally, the usage of ionomers like Nafion was reported to improve the electrolysis by contributing to a faster re-supply of CO 2 and therefore increase the TPB formation where the CO 2 RR takes place [27]. Furthermore, Chen and Su et al modulated the hydrophobicity within the catalyst layer of Cu-particle containing GDEs for the CO reduction using different amounts of polytetrafluoroethylene (PTFE).…”

“…Increasing the binder content up to 25 wt.% increased the contact angle from 132.8 • (5 wt.%) to 147.2 • and led to higher C 2+ product formation compared to 5 or 13 wt.%, probably due to enhanced CO supply at the catalyst [28]. Besides an increased supply of reactant gases, the increased hydrophobicity prevents the GDEs from flooding and stabilizes the electrodes during operation [27]. Additionally, the fabrication method influences the GDE's composition and therefore also the product distribution [29].…”

Advances in cutting‐edge electrode engineering toward CO2 electrolysis at high current density and selectivity: A mini‐review

“…Manipulating the electrode structures, functions, and interface properties has been identified by researchers to have extensive scientific significance, which may greatly promote the device-level CO 2 electrolysis performance, besides the atomic/electronic regulation of the catalytic sites. [10][11][12] Both of them have been demonstrated to achieve CO 2 electrolysis current densities exceeding 200 mA cm −2 . [13][14][15] The reaction path of CO 2 RR from the gaseous CO 2 phase is illustrated in Figure 1c.…”

“…Many recent works have focused on deconvoluting these factors and investigated their influence on CO 2 RR from a theoretical or experimental point of view. [12,22] In addition to regulating the electronic properties of the catalytic sites, electrode engineering has gained particular attention. Electrode engineering promotes the CO 2 RR by increasing the accessible active sites, facilitating the multistep process, tuning the local reactants or intermediates concentration, adjusting the pH of the reaction environment, and optimizing the hydrophilicity or aerophobicity to benefit the mass transportation, as illustrated in Figure 2.…”

“…Solving these two issues is critical to the industrialization of CO 2 electrolysis. Currently existing reviews on the discussion of electrode engineering mostly focus on one aspect of electrode materials, [12,23] electrode structure and morphology, [22] and electrode function. [24] Herein, this review has been organized to comprehensively summarize the recent advances in electrode engineering.…”