Electrochemical CO2 Research Articles

Unraveling the rate-determining step of C2+ products during electrochemical CO reduction

The electrochemical reduction of CO has drawn a large amount of attention due to its potential to produce sustainable fuels and chemicals by using renewable energy. However, the reaction’s mechanism is not yet well understood. A major debate is whether the rate-determining step for the generation of multi-carbon products is C-C coupling or CO hydrogenation. This paper conducts an experimental analysis of the rate-determining step, exploring pH dependency, kinetic isotope effects, and the impact of CO partial pressure on multi-carbon product activity. Results reveal constant multi-carbon product activity with pH or electrolyte deuteration changes, and CO partial pressure data aligns with the theoretical formula derived from *CO-*CO coupling as the rate-determining step. These findings establish the dimerization of two *CO as the rate-determining step for multi-carbon product formation. Extending the study to commercial copper nanoparticles and oxide-derived copper catalysts shows their rate-determining step also involves *CO-*CO coupling. This investigation provides vital kinetic data and a theoretical foundation for enhancing multi-carbon product production.

The Missing Link for Electrochemical CO2 Reduction: Classification of CO vs HCOOH Selectivity via PCA, Reaction Pathways, and Coverage Analysis

The Missing Link for Electrochemical CO₂ Reduction: Classification of CO vs HCOOH Selectivity via PCA, Reaction Pathways, and Coverage Analysis

Multi-band Metasurface-Driven Surface-Enhanced Infrared Absorption Spectroscopy for Improved Characterization of in-Situ Electrochemical Reactions.

Surface-enhanced spectroscopy techniques are the method-of-choice to characterize adsorbed intermediates occurring during electrochemical reactions, which are crucial in realizing a green and sustainable future. Characterizing species with low coverage or short lifetimes has so far been limited by low signal enhancement. Recently, single-band metasurface-driven surface-enhanced infrared absorption spectroscopy (SEIRAS) has been pioneered as a promising technology to monitor a single vibrational mode during electrochemical CO oxidation. However, electrochemical reactions are complex, and their understanding requires the simultaneous monitoring of multiple adsorbed species in situ, hampering the adoption of nanostructured electrodes in spectro-electrochemistry. Here, we develop a multi-band nanophotonic-electrochemical platform that simultaneously monitors in situ multiple adsorbed species emerging during cyclic voltammetry scans by leveraging the high resolution offered by the reproducible nanostructuring of the working electrode. Specifically, we studied the electrochemical reduction of CO2 on a Pt surface and used two separately tuned metasurface arrays to monitor two adsorption configurations of CO with vibrational bands at ∼2030 and ∼1840 cm-1. Our platform provides a ∼40-fold enhancement in the detection of characteristic absorption signals compared to conventional broadband electrochemically roughened platinum films. A straightforward methodology is outlined starting with baselining our system in a CO-saturated environment and clearly detecting both configurations of adsorption. In contrast, during the electrochemical reduction of CO2 on platinum in K2CO3, CO adsorbed in a bridged configuration could not be detected. We anticipate that our technology will guide researchers in developing similar sensing platforms to simultaneously detect multiple challenging intermediates, with low surface coverage or short lifetimes.

Electrochemical CO2 reduction integrated with membrane/adsorption‐based CO2 capture in gas‐diffusion electrodes and electrolytes

AbstractElectrochemical CO2 reduction reaction (CO2RR) has attracted much attention in the last decade, owing to its unique advantages such as operation at ambient conditions, coupling with renewable electricity, and producing a wide range of products and commodities. The majority of CO2RR studies are focused on pure CO2 as feed, while in real CO2 waste streams, such as flue gas or biogas, CO2 concentration does not exceed 40%. Therefore, the economic feasibility of CO2RR and its carbon footprint are greatly limited by the CO2 purification steps before electrolysis ($70–100 per ton of CO2 for CO2/N2 separation). In recent years, studies have exhibited the importance of this matter by integrating CO2 capture and electroreduction in a single unit. Mostly, CO2 capture solutions as electrolytes have been under attention, and promising results have been achieved to significantly improve the overall economy of CO2RR. The focus on CO2 capture‐electroreduction integration can go beyond the solution/electrolyte‐based CO2 capture (e.g., amine solutions and ionic liquids) and other processes such as solid adsorption and membrane‐based processes, as more efficient options, can be potentially integrated with CO2 electroreduction in the gas‐diffusion electrode design. This article aims to review the recent efforts in integrating capture and electroreduction of CO2 and provides new perspectives in material selection and electrode design for membrane‐ and adsorption‐based CO2 capture‐reduction integration, in addition to the analysis of the economic feasibility of this integration.

Mechanistic insights into C-C coupling in electrochemical CO reduction using gold superlattices

Developing in situ/operando spectroscopic techniques with high sensitivity and reproducibility is of great importance for mechanistic investigations of surface-mediated electrochemical reactions. Herein, we report the fabrication of highly ordered rhombic gold nanocube superlattices (GNSs) as substrates for surface-enhanced infrared absorption spectroscopy (SEIRAS) with significantly enhanced SEIRA effect, which can be controlled by manipulating the randomness of GNSs. Finite difference time domain simulations reveal that the electromagnetic effect accounts for the significantly improved spectroscopic vibrations on the GNSs. In situ SEIRAS results show that the vibrations of CO on the Cu2O surfaces have been enhanced by 2.4 ± 0.5 and 18.0 ± 1.3 times using GNSs as substrates compared to those on traditional chemically deposited gold films in acidic and neutral electrolytes, respectively. Combined with isotopic labeling experiments, the reaction mechanisms for C-C coupling of CO electroreduction on Cu-based catalysts are revealed using the GNSs substrates.

Recent Developments in Copper‐Based Catalysts for Enhanced Electrochemical CO2 Reduction

AbstractThe drastic climate change imposing adverse environmental effects receives serious research attention for finding a suitable solution. The replacement of conventional fossil energy sources with renewable and sustainable energy sources is the potential route; and thus, manifests as a viable solution. Accordingly, the electrocatalytic carbon dioxide (CO2) reduction process coupled with the renewable energy source is an emerging strategy for adopting a sustainable approach. However, the existing challenges in designing suitable catalyst, support material, electrolyte, inadequate selectivity, and intermediate reactions of CO2 reduction demand substantial research advancement. Numerous studies reported for the CO2 reduction process highlight the importance of catalyst design and product selectivity. Importantly, the copper‐based catalysts, capable in the output of multi‐carbon products, are reported as a “star” material. This review; therefore, focuses on catalyst design strategies, unique structural/morphological features, and product selectivity of diverse copper‐based catalysts. The outstanding findings of copper‐based catalysts and the corresponding products are critically discussed with adequate figures of merits. The impact of structural/morphological features on product selectivity is discussed in detail. The future scope and author perspectives on copper‐based catalysts for the feasible electrocatalytic CO2 reduction application are summarized.

The Relevance of the Interfacial Water Reactivity for Electrochemical CO Reduction on Copper Single Crystals.

The electrochemical reduction of CO2 is an important electrolysis reaction that enables the conversion of a waste gas to fuels or value-added chemicals. To make this reaction viable, a profound understanding of central intermediate steps, such as the CO electroreduction, is required. On Cu, the CO reduction reaction (CORR) is intimately linked to the hydrogen evolution reaction (HER) that proceeds via the reduction of water in alkaline or neutral electrolytes. Here, we demonstrate that the interaction of water or more specifically the water reduction kinetics on differently smooth Cu(100) and Cu(111) surfaces during the CORR in alkaline media significantly governs the CORR. On Cu(111), faster HER kinetics and the highest CORR activity are observed, even though HER and CORR onsets are more negative. While on Cu(100) small Cu ad-island clusters form in the cathodic potential range only when CO is present, structural changes appear on a larger length scale on Cu(111) both under CORR conditions and when no CO is present. These differences in the reconstruction characteristics may be attributed to the dominance of either the CORR and its intermediates or the HER on the different Cu surfaces. Therefore, the interfacial water reactivity is considered an essential activity descriptor for the CORR on Cu in alkaline media.

Pulsing the Applied Potential in Electrochemical CO2 Reduction Enhances the C2 Activity by Modulating the Dynamic Competitive Binding of *CO and *H

Pulsing the Applied Potential in Electrochemical CO₂ Reduction Enhances the C₂ Activity by Modulating the Dynamic Competitive Binding of *CO and *H

A Guideline to Determine Faradaic Efficiency in Electrochemical CO2 Reduction

A Guideline to Determine Faradaic Efficiency in Electrochemical CO₂ Reduction

Theoretical insights into lanthanide rare earth single-atom catalysts for electrochemical CO2 reduction

This study comprehensively investigated the catalytic performance of lanthanide rare earth metals (REMs) anchored into Salen for CO2RR in terms of stability, selectivity, and activity using density functional theory (DFT).

Metal–organic frameworks and their derivatives for the electrochemical CO2 reduction reaction: insights from molecular engineering

Molecular engineering of MOF-based electrocatalysts for the CO2RR, computational simulations, and advanced characterization studies are discussed and summarized to illustrate the correlation between their structure and performance.

Progress in Cu-based electrocatalysts for electrochemical CO2 reduction to C2+ products

Recent progress in Cu-based electrocatalysts for CO2RR to C2+ products, from theoretical and experimental aspects.

Enzyme-mimicking redox-active vitamin B12 functionalized MWCNT catalyst for nearly 100% faradaic efficiency in electrochemical CO2 reduction

Development of highly functional and green electrocatalyst which mimics the natural enzymes for 100% efficiency, selectivity and low-over potential based facile operation is the ultimate aim for the success of the future electrochemical CO2 reduction based carbon net-zero technologies.

Efficient electrochemical CO2 reduction in acidic electrolytes using armor-like iron nanoparticles/porous nitrogen-doped carbon

The armor-like Fe@NC catalyst was prepared using mechanochemistry-assisted ball milling followed by simple pyrolysis to achieve the electrochemical conversion of CO2 to CO with an impressive FECO of 99.0% in acidic electrolytes.

Modification of ZnO gas-diffusion-electrodes for enhanced electrochemical CO2 reduction: optimization of operational conditions and mechanism investigation

Amino-functionalized ZnO exhibits enhanced CO2 adsorption capacity and selectivity for electrochemical conversion of CO2 to CO.

Surface defect induced polarization manipulation in Cu2SnS3 for boosting electrochemical CO2 reduction

Enhancing electrochemical CO2 reduction of Cu2SnS3via surface polarization manipulation proves effective for designing efficient CO2-to-formate electrocatalysts.

Modeling diurnal and annual ethylene generation from solar-driven electrochemical CO2 reduction devices

Integrated solar fuels devices for CO2 reduction (CO2R) are a promising technology class towards reducing CO2 emissions.

Remote p–d orbital hybridization via first/second-layer coordination of Fe single atoms with heteroatoms for enhanced electrochemical CO2-to-CO reduction

d–p orbital hybridization induced by S/N in the coordination layer of pyrrole-type Fe–N4 can modulate the electronic structure of Fe single atoms, enabling *COOH adsorption and *CO desorption to exclusively furnish CO but suppressing H2 formation.

Enhanced electrochemical CO2-to-ethylene conversion through second-shell coordination on a Cu single-atom catalyst

The electrocatalytic CO2 reduction reaction (CO2RR) utilizing Cu single-atom catalyst modulation through second-shell S coordination (Cu–C3N4–S) achieves predominant catalytic activity with high C2H4 faradaic efficiency at low potentials.

Electronic delocalization engineering of bismuth-based materials for catalytic electrochemical CO2 and N2 conversion

This review focuses on the electronic delocalization engineering of Bi-based materials for the electrocatalytic reduction of CO2 and N2, including facet engineering, alloying, defect engineering, atomic engineering, and others.