Carbon Nanotube CO Reservoir Enables Efficient Tandem CO2 Electroreduction to Multicarbon Products with >1 A cm-2 Partial Current Density.

CO2 electroreduction to multicarbon products from carbonate capture liquid

Efficient Electrocatalytic CO2 Reduction to C2+ Alcohols at Defect-Site-Rich Cu Surface

An Extrinsic Faradaic Layer on CuSn for High-Performance Electrocatalytic CO ₂ Reduction

Toward abiotic sugar synthesis from CO2 electrolysis

Polyacrylate modified Cu electrode for selective electrochemical CO2 reduction towards multicarbon products

Tandem catalysis presents a promising strategy to improve the selectivity toward multicarbon products in the electrocatalytic carbon dioxide reduction reaction (CO2RR). For this reaction, it is well-known that CO is a critical intermediate for producing multicarbon products. Thus, control of CO localization and CO diffusion are vital for promoting the formation of multicarbon products. However, the management of CO localization and CO diffusion remains underexplored. Herein, we design a three-dimensional tandem catalyst electrode with silver nanoparticles (Ag NPs) to generate CO as an intermediate product at the bottom of a copper (Cu) nanoneedle array. This design is shown to enhance the conversion of the intermediate product, CO. Via this nanostructured design, CO2 reduces to C2+ products with a high Faradaic efficiency (FEC2+) of 68.4% in a H-cell and 70% in a flow cell with a current density of 350 mA cm-2 are achieved,. These figures-of-merit are currently among the top reports within the known literature for flow cells with partial current density >200 mA cm-2 to C2+ products. More importantly, we employed in-situ Raman spectroscopy and finite-element method calculations to elucidate the origins of the enhanced selectivity. Together, these approaches reveal the crucial role of prolonging the CO diffusion path length in improving CO utilization during CO2 conversion with tandem catalyst systems. The favorable CO2RR selectivity and current density to C2+ products in two distinct environments (H-cell and flow cell reactors) further corroborate that this effect is not limited to a particular reactor environment. Overall, this study provides a valuable strategy for designing tandem catalysts for improved selectivity to C2+ products in CO2RR.

Increasing demand for energy has led to a high dependence on fossil fuels, which are limited and have been closely associated with major environmental issues such as groundwater pollution and imbalances in the carbon cycle. A more sustainable and cleaner method of producing chemicals and fuels is the electrochemical CO2 reduction reaction (CO2RR). When coupled with renewable electricity, CO2 can be converted to high energy density fuels and commodity chemicals, such as ethanol, propanol, and ethylene, in an environmentally friendly way.Recently, the use of CO feedstocks, instead of CO2, was shown to enhance the selectivity toward multi-carbon products on copper-based electrocatalysts. Technoeconomic analyses have also demonstrated that CO can be produced from CO2RR cost-effectively. This has led to increased efforts in developing tandem electrocatalytic systems. However, state-of-the-art CO2-to-CO electrocatalysts are based on expensive noble metals such as Ag and Au, while earth-abundant Zn displays relatively poorer selectivity and activity. Herein, we show that oxide-derived Zn with high surface area can reduce CO2 to CO with a Faradaic efficiency of 86% and a partial current density (j CO) of −201 mA cm-2. While oxygen vacancies were previously implicated for CO2RR to CO, we pinpointed by detailed experiments and density functional theory calculations that highly undercoordinated Zn sites provide even higher activity, in view of their nearly optimal *COOH adsorption energies. These findings indicate that suitably engineered ZnO-derived materials can potentially be an alternative to the more costly Ag and Au electrocatalysts, and that the main guideline for their design is to increase the undercoordination of the catalytic sites.We also investigate the electrochemical CO reduction reaction (CORR) to liquid fuels and industrial feedstocks on copper-based and mixed copper-silver catalysts. To further enhance the CORR activity and product selectivities, a systematic optimization of the experimental environment, such as the use of various supports, catalyst binder and electrolytes, was done. We develop a set of experimental conditions for optimal CORR performance to value-added products.

The electrochemical reduction of carbon dioxide (CO2RR) holds promise for carbon capture and utilization (CCU), aiming to produce carbon-neutral fuels and valuable chemical intermediates. Copper (Cu) is recognized as the primary metallic catalyst facilitating C-C coupling reactions to yield multi-carbon compounds.Many researchers have been developing Cu catalysts, such as oxide-derived Cu (OD-Cu), and tandem catalysts to increase the kinetics of C-C coupling. The investigation of tandem catalysts, especially those derived from oxides of copper (OD-Cu), has been conducted to improve selectivity towards multi-carbon compounds like ethylene and ethanol.Nonetheless, the effect of the loading structure of the CO-producing catalyst within the tandem catalyst on CO2RR performance has not been fully explored. In this study, we synthesized Au nanoparticles with different sizes and loading densities on Cu2O through the galvanic replacement reaction and examined their influence on CO2RR properties.Tandem catalysts containing smaller Au nanoparticles demonstrated heightened activity in the electrochemical CO2RR, leading to an anodic shift in potential. Additionally, tandem catalysts with smaller Au nanoparticles exhibited improved Faradaic efficiencies (FEs) and partial current densities (PCDs) for C2+ compounds. The tandem catalysts with larger Au nanoparticles also showed better CO2RR performance than the original OD-Cu; however, it was found that CO2RR results of the tandem catalysts with a small size of Au nanoparticles were superior to those with large size of Au nanoparticles.Interestingly, the FEs and PCDs of n-propanol, a C3 product, increased as the coverage of Au nanoparticles increased. This behavior contrasts with the case of ethylene and ethanol. The maximum Faradaic efficiencies (FEs) of these C2 products from tandem catalysts did not exceed those from OD-Cu.The effectiveness of the tandem effect relies on the localized concentration of CO, heightened by the CO-producing catalyst situated on the confined OD-Cu surface. The improvement of the selectivity towards the C3 product may come from the interface between the Au nanoparticles and OD-Cu, where the C1-C2 coupling reaction is favorable.We utilized a Nickel single-atom catalyst (Ni-SAC) to create a high local concentration of CO within the catalyst layer. Despite this, we did not observe any tandem effect. This suggests that the proximity between CO active sites and C2+ active sites plays a crucial role in triggering the CO spillover effect. Our results shed light on a strategy for constructing efficient tandem structures in CO2RR.

Boosting selectivity for multi-carbon products in electrochemical CO2 reduction via enhanced hydroxide adsorption in ultrafine CuOx/CeOx nanoparticles

Electrochemical reduction of carbon dioxide: IV dependence of the Faradaic efficiency and current density on the microstructure and thickness of tin electrode

Boosting Electrocatalytic CO ₂ Reduction with Conjugated Bimetallic Co/Zn Polyphthalocyanine Frameworks

Coupling covariance matrix adaptation with continuum modeling for determination of kinetic parameters associated with electrochemical CO2 reduction

The electrochemical reduction of CO2 is a promising approach for achieving a closed carbon cycle. An increase in the current density is essential for the practical implementation of this technology. As CO2 electrolysis technology for CO production is approaching industrial practicality, there is now an increasing demand for electrolysis technologies that convert the produced CO into higher-valued multicarbon (C2+) products under high-current-density conditions. Herein, we report a substantial enhancement of the partial current density for the reduction of CO to C2+ products over Cu nanoparticles supported on gas diffusion electrodes in 1 M KOH, achieving a record value of 1.6 A cm−2 for C2+ formation at a total current density of 3 A cm−2. This high-current-density CO electrolysis was enabled by the extremely large triple-phase interface area in our electrode, which maximized CO transport. Notably, the partial current density for acetate reached 519 mA cm−2 at −1.74 V vs. Ag/AgCl, with a Faradaic efficiency of 26.0%. The selectivity for acetate in the CO reduction reaction was several times higher than that in the CO2 reduction reaction over the wide total current density range from 0.2 to 3 A cm−2. The coupling between adsorbed reduced species and gaseous CO is expected to form an intermediate for acetate. Under high CO partial pressures, the formation of this intermediate is favored in CO reduction reactions over CO2 reduction reactions. In addition, high-current-density electrolysis increases the surface pH at the electrode, promoting the insertion of OH− into the adsorbed precursor, thereby facilitating acetate formation, as suggested by the analysis of the simulated surface pH.

Selective electrochemical reduction of CO2 by a binder-free platinum/nitrogen-doped carbon nanofiber/copper foil catalyst with remarkable efficiency and reusability

Electrochemical carbon dioxide reduction (CO2 ) is a promising technology to use renewable electricity to convert CO2 into valuable carbon-based products. For commercial-scale applications, however, the productivity and selectivity toward multi-carbon products must be enhanced. A facile surface reconstruction approach that enables tuning of CO2 -reduction selectivity toward C2+ products on a copper-chloride (CuCl)-derived catalyst is reported here. Using a novel wet-oxidation process, both the oxidation state and morphology of Cu surface are controlled, providing uniformity of the electrode morphology and abundant surface active sites. The Cu surface is partially oxidized to form an initial Cu (I) chloride layer which is subsequently converted to a Cu (I) oxide surface. High C2+ selectivity on these catalysts are demonstrated in an H-cell configuration, in which 73% Faradaic efficiency (FE) for C2+ products is reached with 56% FE for ethylene (C2 H4 ) and overall current density of 17 mA cm-2 . Thereafter, the method into a flow-cell configuration is translated, which allows operation in a highly alkaline medium for complete suppression of CH4 production. A record C2+ FE of ≈84% and a half-cell power conversion efficiency of 50% at a partial current density of 336 mA cm-2 using the reconstructed Cu catalyst are reported.