Carbon Dioxide Electroreduction Research Articles

Improving Stability of CO2 Electroreduction by Incorporating Ag NPs in N-Doped Ordered Mesoporous Carbon Structures.

The electroreduction of carbon dioxide (eCO2RR) to CO using Ag nanoparticles as an electrocatalyst is promising as an industrial carbon capture and utilization (CCU) technique to mitigate CO2 emissions. Nevertheless, the long-term stability of these Ag nanoparticles has been insufficient despite initial high Faradaic efficiencies and/or partial current densities. To improve the stability, we evaluated an up-scalable and easily tunable synthesis route to deposit low-weight percentages of Ag nanoparticles (NPs) on and into the framework of a nitrogen-doped ordered mesoporous carbon (NOMC) structure. By exploiting this so-called nanoparticle confinement strategy, the nanoparticle mobility under operation is strongly reduced. As a result, particle detachment and agglomeration, two of the most pronounced electrocatalytic degradation mechanisms, are (partially) blocked and catalyst durability is improved. Several synthesis parameters, such as the anchoring agent, the weight percentage of Ag NPs, and the type of carbonaceous support material, were modified in a controlled manner to evaluate their respective impact on the overall electrochemical performance, with a strong emphasis on operational stability. The resulting powders were evaluated through electrochemical and physicochemical characterization methods, including X-ray diffraction (XRD), N2-physisorption, Inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), SEM-energy-dispersive X-ray spectroscopy (SEM-EDS), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), STEM-EDS, electron tomography, and X-ray photoelectron spectroscopy (XPS). The optimized Ag/soft-NOMC catalysts showed both a promising selectivity (∼80%) and stability compared with commercial Ag NPs while decreasing the loading of the transition metal by more than 50%. The stability of both the 5 and 10 wt % Ag/soft-NOMC catalysts showed considerable improvements by anchoring the Ag NPs on and into a NOMC framework, resulting in a 267% improvement in CO selectivity after 72 h (despite initial losses) compared to commercial Ag NPs. These results demonstrate the promising strategy of anchoring Ag NPs to improve the CO selectivity during prolonged experiments due to the reduced mobility of the Ag NPs and thus enhanced stability.

Low cost 3D printable flow reactors for electrochemistry

Transition to carbon neutrality requires the development of more sustainable pathways to synthesize the next generation of chemical building blocks. Electrochemistry is a promising pathway to achieve this goal, as it allows for the use of renewable energy to drive chemical transformations. While the electroreduction of carbon dioxide (CO2) and hydrogen evolution are attracting significant research interest, fundamental challenges exist in moving the research focus toward performing these reactions on scales relevant to industrial applications. To bridge this gap, we aim to facilitate researchers' access to flow reactors, which allow the characterization of electrochemical transformations under conditions closer to those deployed in the industry. Here, we provide a 3D-printable flow cell design (manufacturing cost < $5), which consists of several plates, offering a customizable alternative to commercially available flow reactors (cost > $6,000). The proposed design and detailed build instructions allow the performance of a wide variety of chemical reactions in flow, including gas and liquid phase electroreduction, electro(less)plating, and photoelectrochemical reactions, providing researchers with more flexibility and control over their experiments. By offering an accessible, low-cost reactor alternative, we reduce the barriers to performing research on sustainable electrochemistry, supporting the global efforts necessary to realize the paradigm shift in chemical manufacturing.

FeOOH with Low Spin State Iron as Electron Acceptors for High Yield Rate Electrosynthesis of Urea from Nitrate and Carbon Dioxide.

Co electroreduction of carbon dioxide and nitrate to synthesize urea provides an alternative strategy to high energy-consumption traditional methods. However, the complexity of the reaction mechanism and the high energy barrier of nitrate reduction result in a diminished production of urea. Herein, a convenient electrodeposition technique to prepare the FeOOH with low spin state iron that increases the yield rate of urea efficiently is employed. According to soft X-ray Absorption Spectroscopy and theoretical calculations, the unique configuration of low spin state iron as electron acceptors can effectively induce electron pair transfer from the occupied σ orbitals of intermediate * NO to empty d orbitals of iron. This σ→d donation mechanism leads to a reduction in the energy barrier associated with the rate-determining step (* NOOH→* NO+* OH), hence augmenting the urea generation. The low spin state iron presents a high urea yield rate of 512µgh-1 cm-2 , representing approximately two times compared to the medium spin state iron. The key intermediates (* NH2 and * CO) in the formation of C─N bond are detected with in situ Fourier transform infrared spectroscopy. The coupling of * NH2 and * CO contributes to the formation of * CONH2 , which subsequently endures multi-step proton-coupled electron transfer to generate urea.

Coupled electroreduction of CO&lt;sub&gt;2&lt;/sub&gt; and H&lt;sup&gt;+&lt;/sup&gt; in the presence of substituted salts of 2,2'-bipyridine

The possibility of conjugate electroreduction of carbon dioxide and hydrogen in the presence of 2,2'-bipyridine and its N -substituted salts in the presence of acids with different pKa values was studied. It was revealed how the strength of the acid affects the efficiency of the process; in particular, it was determined that the presence of methylsulfonic acid in the system promotes the conjugate formation of hydrogen and the reduction of carbon dioxide to formic acid. Probable mechanisms for the reactions occurring have been proposed.

In-Induced Electronic Structure Modulations of Bi─O Active Sites for Selective Carbon Dioxide Electroreduction to Liquid Fuel in Strong Acid.

The formation of carbonate in neutral/alkaline solutions leads to carbonate crossover, severely reducing carbon dioxide (CO2 ) single pass conversion efficiency (SPCE). Thus, CO2 electrolysis is a prospective route to achieve high CO2 utilization under acidic environment. Bimetallic Bi-based catalysts obtained utilizing metal doping strategies exhibit enhanced CO2 -to-formic acid (HCOOH) selectivity in alkaline/neutral media. However, achieving high HCOOH selectivity remains challenging in acidic media. To this end, Indium (In) doped Bi2O2CO3 via hydrothermal method is prepared for in-situ electroreduction to In-Bi/BiOx nanosheets for acidic CO2 reduction reaction (CO2RR). In doping strategy regulates the electronic structure of Bi, promoting the fast derivatization of Bi2O2CO3 into Bi-O active sites to enhance CO2RR catalytic activity. The optimized Bi2 O2 CO3 -derived catalyst achieves the maximum HCOOH faradaic efficiency (FE) of 96% at 200 mA cm-2 . The SPCE for HCOOH production in acid is up to 36.6%, 2.2-fold higher than the best reported catalysts in alkaline environment. Furthermore, in situ Raman and X-ray photoelectron spectroscopy demonstrate that In-induced electronic structure modulation promotes a rapid structural evolution from nanobulks to Bi/BiOx nanosheets with more active species under acidic CO2 RR, which is a major factor in performance improvement.

Nanocurved electric-field-induced optimal catalyst loading for carbon dioxide electroreduction

Nanocurved electric-field-induced optimal catalyst loading for carbon dioxide electroreduction

In Situ Generation of Flash Graphene Supported Spherical Bismuth Nanoparticles in Less than 200 ms for Highly Selective Carbon Dioxide Electroreduction

In Situ Generation of Flash Graphene Supported Spherical Bismuth Nanoparticles in Less than 200 ms for Highly Selective Carbon Dioxide Electroreduction

Engineering bimetallic interfaces and revealing the mechanism for carbon dioxide electroreduction to C3+ liquid chemicals

Engineering bimetallic interfaces and revealing the mechanism for carbon dioxide electroreduction to C3+ liquid chemicals

1.42-fold enhancement of formate selectivity by linker conversion on the Zn-based metal organic framework catalyst

Electro-reduction of carbon dioxide (ERCO2) is considered an effective method to alleviate the greenhouse effect and produce value-added chemicals. Achieving the dominant selectivity of Zn-based catalysts for formate remains a challenge. In this article, the ZnIn-E12 catalyst is successfully prepared by solvent assisted ligand exchange (SALE) method to convert organic ligands, achieving a Faradaic efficiency of 72.28% for formate at −1.26 V vs. RHE (VRHE), which is 1.42 times higher than the original catalyst. Evidence shows that the successful conversion of organic ligands can transform the catalyst from the original large size polyhedron to cross-linked network of particles with a diameter of about 30 nm. The increased specific surface area can expose more active sites and facilitate the electrocatalytic conversion of CO2 to formate. This work is expected to provide inspiration for the regulation of formate selectivity and catalyst size in Zn-based catalysts.

Roughness Factors of Electrodeposited Nanostructured Copper Foams

Copper-based electrocatalytic materials play a critical role in various electrocatalytic processes, including the electroreduction of carbon dioxide and nitrate. Three-dimensional nanostructured electrodes are particularly advantageous for electrocatalytic applications due to their large surface area, which facilitates charge transfer and mass transport. However, the real surface area (RSA) of electrocatalysts is a crucial parameter that is often overlooked in experimental studies of high-surface-area copper electrodes. In this study, we investigate the roughness factors of electrodeposited copper foams with varying thicknesses and morphologies, obtained using the hydrogen bubble dynamic template technique. Underpotential deposition (UPD) of metal adatoms is one of the most reliable methods for estimating the RSA of highly dispersed catalysts. We aim to illustrate the applicability of UPD of lead for the determination of the RSA of copper deposits with hierarchical porosity. To find the appropriate experimental conditions that allow for efficient minimization of the limitations related to the slow diffusion of lead ions in the pores of the material and background currents of the reduction of traces of oxygen, we explore the effect of lead ion concentration, stirring rate, scan rate, monolayer deposition time and solution pH on the accuracy of RSA estimates. Under the optimized measurement conditions, Pb UPD allowed to estimate roughness factors as high as 400 for 100 µm thick foams, which translates into a specific surface area of ~6 m2·g−1. The proposed measurement protocol may be further applied to estimate the RSA of copper deposits with similar or higher roughness.

Boron-modified CuO as catalyst for electroreduction of CO2 towards C2+ products

The development for electroreduction of carbon dioxide (CO2) is crucial for achieving sustainable cycles and carbon neutrality. Electroreduction of CO2 to C2+ products can not only mitigate environmental issues by reducing CO2 but also provide high-value chemicals for modern industry. In this study, we synthesized CuO nanosheets (CuO NS) via simple hydrothermal method and modified its electron structure by in-situ boron (B) doping to produce B-CuO NS catalyst. The XPS spectra revealed the successfully doping of B into CuO NS, which obviously changes the electron density of Cu on the surface of CuO NS. As a result, B-CuO NS displayed a higher performance for electroreduction of CO2 compared with original CuO NS. The optimized B-CuO NS catalyst exhibits a faradaic efficiency of 54.78 % for C2+ production at −1.2 V vs. reversible hydrogen electrode (RHE). Based on the structural characterization and Density Functional Theory (DFT) calculations, the introduction of B increases the charge density of Cu, which could process free electrons to adsorb *CO. Thanks to the easier adsorbing of *CO on B-CuO NS as well as the lower adsorption energy of *CO on Cu, C–C coupling reaction was promoted to produce more C2+ products. This work shows a rational design strategy for developing efficient catalysts for electroreduction of CO2.

Electronic Structure Modulation of Unconventional Phase Metal Nanomaterials for Highly Selective Carbon Dioxide Electroreduction

Electronic Structure Modulation of Unconventional Phase Metal Nanomaterials for Highly Selective Carbon Dioxide Electroreduction

Towards ethylene production from carbon dioxide: Economic and global warming potential assessment

Currently, ethylene is the most important chemical with the largest global demand: it is mainly produced by ethane or naphtha cracking but, this is characterized by significant carbon dioxide emissions. For this reason, starting from carbon dioxide and water, different routes for ethylene production have been proposed and investigated in the literature but a complete comparative analysis is missing.In this research, we analyze ethylene production via carbon dioxide electroreduction and methanol-to-olefin process, with methanol obtained in several ways. After the modelling of these systems, economic and environmental (in term of global warming potential) analyses are conducted to develop a comparison among the investigated processes and a conventional one based on naphtha cracking.Results, located in the UK, show that the tandem process could be economically competitive (with the lowest production cost of $ 1.34 per kg of ethylene), while the methanol-to-olefin process with methanol obtained from syngas (produced through carbon dioxide-water co-electrolysis) has the best advantage for carbon dioxide emissions (with the lowest impact of −3.08 kg of CO2eq per kg of ethylene). Moreover, the most preferred energy source for the electricity supply is the nuclear one with a small-scale plant because, economic and greenhouse gas emission advantages are provided while, worse conditions are obtained when solar energy is used.Our main finding is that electrochemical processes are likely to play an important role in the future when performance improvements are realized.

Synergistic interaction of FeCo anchored on phthalocyanine for efficient CO2 electroreduction to C2 via microkinetic study

It is been thought as an absorbing method to carbon dioxide electroreduction reaction (CO2RR) into worthy products. However, it has been hindered because of the ultrahigh overpotential required, poor selectivity, the inevitably competitive hydrogen evolution reactions and inefficient conversion to C2 for the trouble of C–C coupling. Herein, a dual metal–nitrogen active sites anchored within phthalocyanine (FeCo-Pc) is designed as a perfect synergistic catalyst for capable CO2RR into C2. Because of the strong synergistic interactions of the doped Cobalt and Ferrum dual active sites, the obtained FeCo-Pc catalyst exhibits significantly enhanced capability in substrate adsorption and CO2 activation. The proposed reaction path shows that FeCo-Pc can accelerate CO∗ and CHO∗ intermediates dimerization with 0.70 eV activation energy, forming C2 species. Density functional theory studies have proposed that glycolaldehyde could be a selectivity-determining intermediate. The structure sensitivity and energy difference of the reaction after this intermediate would decide the ascendant C2, ethanol, ethylene, and ethylene glycol. It finds that FeCo-Pc efficiently converts CO2 mainly to ethylene at potentials of −0.66 versus reversible hydrogen electrode. Through analysis the rate constant and rate determining step, ethylene mechanism is judged as the most favorable one. The turnover frequency control degree (XTOF) of the species in four mechanisms is employed as descriptors to enhance the FeCo-Pc catalyst. This work may serve as a new method for CO2RR to C2 products by designing and utilizing multiple catalytic active sites catalysts.

A stable and conductive phthalocyanine-porphyrin two-dimensional carbon-rich conjugation frameworks for highly selective electroreduction of carbon dioxide to dimethyl carbonate

Electrocatalytic reduction of carbon dioxide (CO2RR) to long-chain chemicals, such as dimethyl carbonate (DMC), is considered an effective strategy for addressing excessive CO2 emissions. However, the underlying reaction mechanism remains unclear. In this work, based on phthalocyanine-porphyrin 2D CCFs, a tandem catalyst composed of Fe and other transition metals (TMs) co-embedded in rectangular extended Pc and TM-embedded in porphyrins is proposed. Among various catalysts, the Fe-Sc-Pc-Co-TPP-CCF catalyst stands out due to its unique catalytic sites that can efficiently convert both C1 and C2 intermediates simultaneously. This catalyst exhibits superior CO2 adsorption capacity and excellent catalytic activity, which can be attributed to the ability of the d orbitals of both Fe and TMs to accept lone pairs and feedback electrons from CO2. Additionally, the synergistic effect between the two different metals enhances the adsorption and activation of CO2 molecules. The detailed process of CO2 reduction to DMC on the Fe-Sc-Pc-Co-TPP-CCF catalyst was systematically investigated, and it was identified that the direct coupling of CO2 and methanol to form DMC is the optimal pathway. To evaluate the catalytic performance of the catalyst, we conducted density functional theory calculations. The results show that the Fe-Sc-Pc-Co-TPP-CCF catalyst exhibits an inhibitory effect on competing reactions of CO2RR, such as proton-coupling reaction and HER. Combined with DFT calculations, the reaction mechanism at the phthalocyanine-porphyrin 2D CCFs was systematically studied, providing novel insights into the potential pathway for the chemical conversion of CO2 into long-chain chemicals.

Carbon Dioxide Electroreduction to Formate in Acid Electrolytes in the Acetylene Black Gas-Diffusion Electrode with Lead Catalyst

Carbon Dioxide Electroreduction to Formate in Acid Electrolytes in the Acetylene Black Gas-Diffusion Electrode with Lead Catalyst

Phase Interface Regulating on Amorphous/Crystalline Bismuth Catalyst for Boosted Electrocatalytic CO2 Reduction to Formate.

Electroreduction of carbon dioxide into readily collectable and high-value carbon-based fuels is greatly significant to overcome the energy and environmental crises yet challenging in the development of robust and highly efficient electrocatalysts. Herein, a bismuth (Bi) heterophase electrode with enriched amorphous/crystalline interfaces was fabricated via cathodically in situ transformation of Bi-based metal-phenolic complexes (Bi-tannic acid, Bi-TA). Compared with amorphous or crystalline Bi catalyst, the amorphous/crystalline structure Bi leads to significantly enhanced performance for CO2 electroreduction. In a liquid-phase H-type cell, the Faraday efficiency (FE) of formate formation is over 90% in a wide potential range from -0.8 to -1.3 V, demonstrating a high selectivity toward formate. Moreover, in a flow cell, a large current density reaching 600 mA cm-2 can further be rendered for formate production. Theoretical calculations indicate that the amorphous/crystalline Bi heterophase interface exhibits a favorable adsorption of CO2 and lower energy barriers for the rate-determining step compared with the crystalline Bi counterparts, thus accelerating the reaction process. This work paves the way for the rational design of advanced heterointerface catalysts for CO2 reduction.

Carbon dioxide and nitrate co-electroreduction to urea on CuOxZnOy

Urea is a commonly used nitrogen fertiliser synthesised from ammonia and carbon dioxide using thermal catalysis. This process results in high carbon dioxide emissions associated with the required amounts of ammonia. Electrocatalysis provides an alternative method to urea production with reduced carbon emissions while utilising waste products like nitrate. This manuscript reports on urea synthesis from the electroreduction of nitrate and carbon dioxide using CuOxZnOy electrodes under mild conditions. Catalysts with different ratios of CuO and ZnO, synthesised via flame spray pyrolysis, were explored for the reaction. The results revealed that all the CuOxZnOy electrocatalyst compositions produce urea, but the efficiency strongly depends on the metal ratio composition of the catalysts. The CuO50ZnO50 composition had the best performance in terms of selectivity (41% at −0.8 V vs RHE) and activity (0.27 mA/cm2 at −0.8 V vs RHE) towards urea production. Thus, this material is one of the most efficient electrocatalysts for urea production reported so far. This study systematically evaluates bimetallic catalysts with varying compositions for urea synthesis from carbon dioxide and nitrate.

Reverse Water Gas Shift Versus Carbon Dioxide Electro-Reduction: The Reaction Pathway Responsible for Carbon Monoxide Production in Solid Oxide Co-Electrolysis Cells

Solid oxide co-electrolysis cells are an emerging technology that can utilize renewable energy sources for the conversion of steam and carbon dioxide into valuable chemicals and feedstocks. An important challenge in the analysis of these devices is understanding the reaction pathway(s) responsible for the production of carbon monoxide. Some researchers have suggested that it is largely attributed to the reverse water gas shift reaction, since the polarization curves of pure steam electrolysis and co-electrolysis overlap each other; therefore, they surmised the electro-reduction of carbon dioxide is inconsequential to carbon monoxide production. Conversely, other studies have shown the polarization curves corresponding to co-electrolysis lie between those of pure steam and pure carbon dioxide electrolysis, thus indicating the reverse water gas shift reaction and the electro-reduction of carbon dioxide are both contributors. For the first time, this analysis attempts to untangle the conflicting phenomena observed in previous experiments by utilizing dimensional analysis, thermodynamics, and reaction kinetics. We illustrate the operating regime in which both reaction pathways contribute to the production of carbon monoxide, while demonstrating that the reverse water gas shift reaction is inconsequential when steam electrolysis and co-electrolysis polarization curves coincide, which is contrary to what has been concluded in previous analyses. This work is intended to provide an enhanced understanding of the observed behaviour of solid oxide co-electrolysis cells, and can help designers and researchers make informed decisions on how to construct their cell to exploit a desired reaction pathway.

Species Crossover in Electrochemical CO2 Reduction

Catalyst studies have improved the overall CO2R (electrochemical CO2 reduction) faraday efficiency (FE)1, however, the experimental FE can be deteriorated by product crossover through the membrane in a practical electrochemical CO2R cell. The CO2R product molecules generated at the cathode are subject to oxidation at the anode if they permeate through the membrane, thus decreasing the practical CO2R product collection. The product loss at the anode also poses a challenge for quantification and study of the crossover behavior2–4. In this work, we will present experimental designs that effectively overcome the oxidation at the anode to reveal the CO2R product crossover.The CO2R product crossover can be driven by electromigration and the concentration gradient across the membrane. Although the electromigration plays a significant role based on the current density of CO2R operation, the later can be varied by membrane design parameters. The membrane thickness and non-ionic reinforcement layers can effectively change the permeability of various CO2R product species. The CO2R product crossover measurements of commercially available anion exchange membranes will be presented.From a fundamental perspective, CO2R product crossover is a reflection of membrane selectivity. We also extend the component study to the cell level where parameters like electrolyte concentration/conductivity and electrolyte/CO2 flow rate also affect the crossover. The species other than products in CO2R can have impact on both catalyst performance and crossover. We will discuss the crossover behavior in our standard CO2R setup5,6. Overall, we aim to address the CO2R product crossover by bridging the fundamental study of a component and CO2R integration efforts at NREL. Ge, L. et al. Electrochemical CO2 reduction in membrane-electrode assemblies. Chem 8, 663–692 (2022).McCallum, C. et al. Reducing the crossover of carbonate and liquid products during carbon dioxide electroreduction. Cell Rep. Phys. Sci. 2, 100522 (2021).Wang, N. et al. Suppressing the liquid product crossover in electrochemical CO2 reduction. SmartMat 2, 12–16 (2021).Zhang, J., Luo, W. & Züttel, A. Crossover of liquid products from electrochemical CO2 reduction through gas diffusion electrode and anion exchange membrane. J. Catal. 385, 140–145 (2020).Chen, Y. et al. A Robust, Scalable Platform for the Electrochemical Conversion of CO2 to Formate: Identifying Pathways to Higher Energy Efficiencies. ACS Energy Lett. 5, 1825–1833 (2020).Chen, Y. et al. The effect of catholyte and catalyst layer binders on CO2 electroreduction selectivity. Chem Catal. 2, 400–421 (2022).