Electrochemical Conversion Of CO2 Research Articles

Liquid Metal-Enabled Tunable Synthesis of Nanoporous Polycrystalline Copper for Selective CO2-to-Formate Electrochemical Conversion.

Copper-based catalysts exhibit high activity in electrochemical CO2 conversion to value-added chemicals. However, achieving precise control over catalysts design to generate narrowly distributed products remains challenging. Herein, a gallium (Ga) liquid metal-based approach is employed to synthesize hierarchical nanoporous copper (HNP Cu) catalysts with tailored ligament/pore and crystallite sizes. The nanoporosity and polycrystallinity are generated by dealloying intermetallic CuGa2 formed after immersing pristine Cu foil in liquid Ga in a basic or acidic solution. The liquid metal-based approach allows for the transformation of monocrystalline Cu to the polycrystalline HNP Cu with enhanced CO2 reduction reaction (CO2RR) performance. The dealloyed HNP Cu catalyst with suitable crystallite size (22.8nm) and nanoporous structure (ligament/pore size of 45nm) exhibits a high Faradaic efficiency of 91% toward formate production under an applied potential as low as -0.3 VRHE. The superior CO2RR performance can be ascribed to the enlarged electrochemical catalytic surface area, the generation of preferred Cu facets, and the rich grain boundaries by polycrystallinity. This work demonstrates the potential of liquid metal-based synthesis for improving catalysts performance based on structural design, without increasing compositional complexity.

Conjugated polyimides modified self-supported carbon electrodes for electrochemical conversion of CO2 to CO

Conjugated polyimides modified self-supported carbon electrodes for electrochemical conversion of CO₂ to CO

Recent advances in integrated capture and electrochemical conversion of CO2

Recent advances in integrated capture and electrochemical conversion of CO2

Synthesis of Surfactant-Modified Copper Molybdate Nanorod and Its Catalytic Activity Study toward the Electrochemical Conversion of CO2 to Acetaldehyde and C–C Coupling

Synthesis of Surfactant-Modified Copper Molybdate Nanorod and Its Catalytic Activity Study toward the Electrochemical Conversion of CO₂ to Acetaldehyde and C–C Coupling

Solid Oxide Cell Reactor Model for Transient and Stationary Electrochemical H2O and CO2 Conversion Process Studies

The ability of high-temperature solid oxide cell (SOC) electrochemical reactors to efficiently convert atmospheric carbon to high value chemicals for industrial and energy storage applications via CO2 and co-electrolysis makes them a key technology for active carbon utilisation. However, due to additional operational risks from thermochemical reactions on thermal management, limited experimental capacity, and relative novelty, CO2 and co-electrolysis lag behind steam electrolysis in large-scale adoption. Here, a 1D+1D SOC model based on fundamental first principles considering three-dimensional heat transfer was improved via a unique method for representing co-electrolysis electrochemistry, solving with low computational effort. Validation against experimental data for two compositions and pressures, showed high levels of accuracy with respect to characteristic cell voltages, temperatures, and outlet compositions. The model also showed CO2 reduction during co-electrolysis mainly occurred via reverse water gas shift, while CO2 electrolysis still accounted for up to 35% of the total share. Pressurised co-electrolysis operation promotes exothermic methanation, causing pronounced heating of the reactor, consequently reducing the isothermal current density. Therefore, low to moderate pressurisation is likely most suited for coupling with downstream synthesis processes to avoid the installation of unnecessarily large systems and associated high costs.

Investigation of m- and p-xylene linked bimetallic Ni-cyclam-complexes as potential electrocatalysts for the CO2 reduction

Among the various molecular CO2 reduction catalysts, the [Ni(cyclam)]2+ (Ni-{N4}) complex with its earth-abundant metal center and macrocyclic ligand proved to be efficient for the selective electrochemical conversion of CO2 to CO. In the present study we now connected the two Ni-cyclam units by using para- and meta-xylene as organic linkers attached to the amines of the macrocycle to form the p-{Ni2} andm-{Ni2} complexes, respectively, and test them as catalysts for the electrochemical CO2 reduction reactions. Notably, the p-{Ni2} complex demonstrates a higher faraday efficiency in the electrochemical reduction of CO2 to CO compared to the m-{Ni2} complex. This finding highlights the significant role played by the M-M distance in influencing this catalytic process.

Self-Powered Electrochemical CO2 Conversion Enabled by a Multifunctional Carbon-Based Electrocatalyst and a Rechargeable Zn-Air Battery.

Multifunctional electrocatalysts are required for diverse clean energy-related technologies (e.g., electrochemical CO2 reduction reaction (CO2RR) and metal-air batteries). Herein, a nitrogen and fluorine co-doped carbon nanotube (NFCNT) is reported to simultaneously achieve multifunctional catalytic activities for CO2RR, oxygen reduction reaction (ORR), and oxygen evolution reaction (OER). Theoretical calculations reveal that the superior multifunctional catalytic activities of NFCNT are attributed to the synergistic effect of nitrogen and fluorine co-doping to induce charge redistribution and decrease the energy barrier of rate-determining step for different electrocatalytic reactions. Furthermore, the rechargeable Zn-air battery (ZAB) with NFCNT electrode delivers a high peak power density of 230mWcm-2 and superior durability over 100 cycles, outperforming the ZAB with Pt/C+RuO2 based electrodes. More importantly, a self-driven CO2 electrolysis unit powered by the as-assembled ZABs is developed, which achieves 80% CO Faraday efficiency and 60% total energy efficiency. This work provides a new insight into the exploration of highly efficient multifunctional carbon-based electrocatalysts for novel energy-related applications.

Enhanced photo-electro catalytic CO2 conversion using transition metal doped TiO2 nanoparticles

The Fe, Co, and Ni-doped TiO2 were synthesised by sol–gel process, and the nanomaterials were coated on electrodes through a slurry with Nafion. This study aims to use prepared nanoparticles of Fe, Co, and Ni-doped TiO2 to enhance the photo-electrocatalytic conversion of CO2. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and electrochemical analyses were utilized to characterise the doped and undoped TiO2 nanoparticles. Transmission electron microscopy (TEM) studies revealed that the nanomaterials had an average size below 20 nm. Tauc plot analysis for optical absorption studies shown a reduction in band gap when doped with Fe, Co and Ni, with the most significant decrease observed for Fe-doped TiO2, following the order Fe < Co < Ni. Electrochemical CO2 conversion efficiencies were investigated through cyclic voltammetry (CV) curves, electrochemical impedance spectroscopy (ESI), and linear sweep voltammetry (LSV) studies. The results were analysed based on various scan rates and photo exposure, indicating superior performance for Fe-TiO2, aligning with the observed band gap trends. Gas chromatography (GC) analysis of the reduction products revealed the generation of hydrocarbons, with Fe-TiO2 exhibiting the most favourable outcomes. This research provides valuable insights into tailoring TiO2 nanoparticles for efficient photo-electro catalytic reduction of CO2.

Direct Electrochemical Conversion of CO2 Sorbent Solution to Formate by a Molecular Iron Catalyst

Direct Electrochemical Conversion of CO₂ Sorbent Solution to Formate by a Molecular Iron Catalyst

Unraveling the Influence of Shell Thickness in Organic Functionalized Cu2O Nanoparticles on C2+ Products Distribution in Electrocatalytic CO2 Reduction

AbstractCu‐based electrocatalysts exhibit enormous potential for electrochemical CO2 conversion to added‐value products. However, high selectivity, specially toward C2+ products, remains a critical challenge for its implementation in commercial applications. Herein, the study reports the preparation of a series of electrocatalysts based on octadecyl amine (ODA) coated Cu2O nanoparticles (NPs). HRTEM images show ODA coatings with thickness from 1.2 to 4 nm. DFT calculations predict that at low surface coverage, ODA tends to lay on the Cu2O surface, leaving hydrophilic regions. Oppositely, at high surface coverage, the ODA molecules are densely packed, being detrimental for both mass and charge transfer. These changes in ODA molecular arrangement explain differences in product selectivity. In situ Raman spectroscopy has revealed that the optimum ODA thickness contributes to the stabilization of key intermediates in the formation of C2+ products, especially ethanol. Electrochemical impedance spectroscopy and pulse voltammetry measurements confirm that the thicker ODA shells increase charge transfer resistance, while the lowest ODA content promotes faster intermediate desorption rates. At the optimum thickness, the intermediates desorption rates are the slowest, in agreement with the maximum concentration of intermediates observed by in situ Raman spectroscopy, thereby resulting in a Faradaic efficiency to ethanol and ethylene over 73%.

Electrochemical synthesis of C2 and C3 hydrocarbons from CO2 on an Ag electrode in DEME-BF4 containing H2O and metal hydroxides

In the electrochemical synthesis of hydrocarbon gases from CO2, the improvement of the selectivity of the product by controlling the composition of the electrolyte is attractive as a process that does not require complex electrode structures; however, little is known about the conversion process of CO2 at the ionic liquid-based electrolyte/metal electrode interface. In this study, the electrochemical conversion of CO2 and H2O to C2 and C3 hydrocarbons on a pure Ag electrode in N, N‑diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate (DEME-BF4) containing H2O and metal hydroxides, such as Ca(OH)2, NaOH, and CsOH, was investigated. Quantitative gas analysis of the samples obtained by potentiostatic electrolysis for 30 min in the melt with DEME-BF4:H2O:Ca(OH)2 molar ratio of 2:1:1.8 × 10−4 at room temperature demonstrated that C2H4, C2H6, C3H6, and C3H8 were produced, and the current efficiency of C3H8 was determined to be 11.3 %. The reactant was HCO3− coordinated with DEME+, BF4−, and Ca2+ ions, as identified by Raman spectroscopy combined with density functional theory (DFT) calculations. Moreover, the surface-enhanced Raman spectroscopic data revealed that the intermediate on the Ag electrode during potentiostatic electrolysis was adsorbed 2CO− interacting with Ca2+ ions. DFT simulations also demonstrated that Ca2+ increased the energetic stability of the 2CO−. This study showed that tailoring the electrolyte can lead to molecular-level changes in the phase transformation of CO2 in bulk solution and at the electrode/ionic liquid electrolyte interface and proposed a process that enables the synthesis of unique hydrocarbons such as C3.

Continuous Direct Air Capture and Electrochemical Conversion of CO2 and H2O into Ethylene and Oxygen in a Solid Electrolyte Reactor

Continuous Direct Air Capture and Electrochemical Conversion of CO₂ and H₂O into Ethylene and Oxygen in a Solid Electrolyte Reactor

Visualizing Electrochemical CO2 Conversion via the Emerging Scanning Electrochemical Microscope: Fundamentals, Applications and Perspectives.

With the rapid development and maturity of electrochemical CO2 conversion involving cathodic CO2 reduction reaction (CO2RR) and anodic oxygen evolution reaction (OER), conventional ex situ characterizations gradually fall behind in detecting real-time products distribution, tracking intermediates, and monitoring structural evolution, etc. Nevertheless, advanced in situ techniques, with intriguing merits like good reproducibility, facile operability, high sensitivity, and short response time, can realize in situ detection and recording of dynamic data, and observe materials structural evolution in real time. As an emerging visual technique, scanning electrochemical microscope (SECM) presents local electrochemical signals on various materials surface through capturing micro-current caused by reactants oxidation and reduction. Importantly, SECM holds particular potentials in visualizing reactive intermediates at active sites and obtaining instantaneous morphology evolution images to reveal the intrinsic reactivity of active sites. Therefore, this review focuses on SECM fundamentals and its specific applications toward CO2RR and OER, mainly including electrochemical behavior observation on local regions of various materials, target products and onset potentials identification in real-time, reaction pathways clarification, reaction kinetics exploration under steady-state conditions, electroactive materials screening and multi-techniques coupling for a joint utilization. This review undoubtedly provides a leading guidance to extend various SECM applications to other energy-related fields.

Boosting electrochemical conversion of CO2 to ethanol through the confinement of pyridinic N-B layer on copper nanoparticles

Developing efficient electrocatalysts for CO2 reduction has gained significant attention in the field of sustainable energy, especially the Cu-based catalysts for CO2 conversion to valuable alcohols. In this study, we developed Cu nanoparticles supported on pyridinic N-B doped graphene nanoribbons/amorphous carbon (Cu/BNC-1) as an electrocatalyst for CO2 reduction, exhibiting substantially improved ethanol (EtOH) conversion rate in terms of activity, selectivity, and stability. The Cu/BNC-1 achieved a remarkable 58.64 % Faradaic efficiency (FE) for producing EtOH at −1.0 V vs. RHE with a current density of 20.4 mA cm−2 in 0.5 M KHCO3 electrolyte. In-situ Raman, FT-IR, and density functional theory (DFT) calculations demonstrated that the high C2+ product selectivity of Cu/BNC-1 attributed to the pyridinic N-B modulation, lowering the CO dimerization barrier. Moreover, the synergistic confinement effect of Cu and BNC can stabilize the C-O bond of the *HOCCH intermediate, thereby increasing the yield of EtOH.

Electrochemical and catalytic conversion of CO2 into formic acid on Cu-InO2 nano alloy decorated on reduced graphene oxide (Cu-InO2@rGO)

The catalytic and electrochemical hydrogenation of CO2 offers the option of a carbon-neutral cycle for sustainable energy and synthesis of value-added chemicals. The synthesized noble metal-free Cu-InO2@rGO nanocomposite has been characterized by various techniques such as scanning electron microscopy (SEM) confirming the spherical shape of Cu-InO2 nanoalloy embedded on rGO, the average size calculated by high resolution-transmission electron microscopy (HR-TEM) shows Cu-InO2 (∼ 4 nm) alloy is on rGO surface (∼100 nm). The XRD pattern confirms the Face centered cubic (FCC) crystal structure of Cu-InO2@rGO, and Furrier transform- Infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses of Cu-In-O exist in the nanomaterials. The linear sweep voltammetry (LSV) demonstrates an ultra-low potential of −0.9 V vs. SCE. The bulk electrolysis on Cu-InO2@rGO electrocatalyst demonstrated at a potential of −1.1 V vs. SCE to reach HCOOH with a Faradic yield of 76.10%. Electrochemical CO2 reduction on Cu-InO2@rGO is responsible for the variation of adsorption of CO2 intermediates due to controlled selectivity and inhibiting the formation of H2 and CO. In catalytic hydrogenation used as the same catalyst was found, an excellent yield towards HCOOH is 5.5 mmol. Current studies have highlighted the enhancement in activity along with selectivity for product formation could be due to having a capable active interface from electrocatalysts for low cost and proficient production of fuels.

Electrodeposition of Cu with Amino Acids toward Electrocatalytic Enhancement of CO2 Reduction Reaction

This study investigates the effect of five amino acids on the electrodeposition of Cu to enhance its electrocatalytic performance in CO2 reduction reactions (CO2RR). The amino acids significantly influenced the deposition potential, crystallite size, and surface morphology of the electrodeposited Cu. Electrodeposited Cu with amino acids exhibit significantly smaller crystallites and higher particle density on carbon paper relative to amino acid-free samples. The integration of amino acids into the electrodeposited Cu was confirmed via high-angle annular dark-field scanning transmission electron microscopy, energy dispersive X-ray spectroscopy and hard X-ray photoelectron spectroscopy. All electrodeposited Cu exhibits a higher faradaic efficiency (FE) in the electrochemical reduction of CO2 to CH4 relative to Cu foil (24.2%), regardless of the presence or absence (55.0%) of amino acids when the electrolysis was conducted at −1.27 V vs RHE. Electrodeposited Cu with L-histidine, containing an imidazole group, demonstrates a higher FE of CH4 (67.6%) and effectively suppressed the hydrogen evolution reaction, highlighting the crucial role of amino acid functional groups, particularly imidazole, in augmenting the electrochemical conversion of CO2 to CH4. The study demonstrates the critical influence of specific functional groups in amino acids on the catalytic efficiency of electrodeposited Cu in CO2RR electrocatalysis applications.

Electrochemical Characterization of Nickel/Gadolinia Doped Ceria Fuel Electrodes under H2/H2O/CO/CO2-Atmospheres

Modelling of the co-electrolysis process requires understanding of the underlying reaction pathways under H2/H2O/CO/CO2-atmospheres. These include the electrochemical steam reduction/hydrogen oxidation, the electrochemical CO2 reduction/CO oxidation and their coupling via the catalytic (reverse) water gas shift reaction ((R)WGS). The assumption of a very fast RWGS and therefore neglectable electrochemical CO2 conversion is commonly used to model the co-electrolysis process. In contrast, previous studies on Ni/GDC fuel electrodes suggest that the electrochemical conversion of CO/CO2 can be present in H2/H2O/CO/CO2-atmospheres. To deconvolute surface-related and non-surface-related processes in the impedance response we present results from a complex variation of operating parameters for process identification by the use of electrochemical impedance spectroscopy and the subsequent impedance analysis by the distribution of relaxation times. A physically meaningful equivalent circuit model, based on a single channel transmission line, is then derived. The model enables quantification of the surface reaction resistance under varied C/H-ratios. From a kinetic analysis it is shown that the electrochemical H2/H2O conversion is dominant for yCO+yCO2≤ 50% and electrochemical CO/CO2-conversion onsets from yCO+yCO2 ≥ 60%.

Evolution of bismuth electrodes activating electrosynthesis of formate from carbon dioxide reduction

Electrochemical conversion of CO2 into valuable chemicals and fuels has emerged as a promising approach to achieving the net-zero emission target. In this work, bismuth (Bi)-based gas diffusion electrodes (GDEs) are prepared via scalable inkjet printing of the precursor on carbon papers, and subsequent thermal treatment. The optimization of the GDEs aims at the efficient CO2 reduction to formate (HCOO−) with good selectivity and high current density. Ex situ FESEM, XRD, and XPS analyses evidence the morphological and structural transformations of Bi-based catalysts during electrolysis. In situ Raman spectroscopy illustrates the dynamic evolution of the electrocatalysts in a range of potentials. The complete procedure is represented as the transformation of Bi2O3 polyhedral microcrystals to a flower-like assembly of Bi2O2CO3 nanoflakes when exposed to KHCO3 electrolyte under electrochemical conditions, and then to metallic Bi at more negative potentials (< −0.6 V vs. RHE). The evolution of Bi-GDEs confirms that metallic Bi nanostructure provides abundant active sites for selective conversion of CO2 to HCOO−, and is highly promising for applications at industrially relavant scales.

Cathode Surface pH Modulates Multicarbon Product Selectivity during the Electrochemical Conversion of CO2 Capture Solutions

Cathode Surface pH Modulates Multicarbon Product Selectivity during the Electrochemical Conversion of CO₂ Capture Solutions

Carbon dioxide capture by direct methanation in co-electrolysis using solid oxide cell

Reducing carbon emissions in the global economy's energy and industry sectors necessitates not just the implementation of innovative low-emission technologies but also the adoption of techniques for capturing and recycling CO2. The Power-to-X conversion allows the path to the reuse of CO2 originating from fossil fuels burning and other industrial processes, hence reducing the emission of the key greenhouse gas. The use of high-temperature electrochemical devices for such purposes is a promising solution, which has been already deployed as subsidized demo projects. In the present work, the direct electrolysis of the H2O-CO2-H2 mixtures with in situ conversion of CO2 and CO to CH4 was effectively conducted in the temperature range of 575–650 °C using commercial solid oxide half-cell with YSZ-type electrolyte on Ni-YSZ support with a custom lanthanum‑strontium cobaltite anode. The degree of carbon conversion in the atmosphere enriched with hydrogen was close to 90%, but under such conditions, the products are diluted to 5–6 vol% in H2. Reducing the temperature leads to a sufficient increase in the CH4 outcome, but it is constrained by the decline of the cell performance. Electrochemical processes were monitored by impedance spectroscopy and analyzed using the distribution of the relaxation times technique. Analysis of the distribution of relaxation times of impedance spectra showed that two parallel competitive processes can be attributed to CO2 conversion. Peak with characteristic time c.a. 0.1 s might be associated with diffusion-like mass transfer through cermet support, and it plays an important role in the electrochemical conversion at elevated temperature and high current density. Conversely, the peak observed in the vicinity of 5 ms becomes the limiting stage at lower temperature and probably is related to charge transfer or absorption and surface diffusion of carbon-containing species. Electrolysis current density might reach 0.4 A cm−2 even at 600 °C without explicit damage to the electrolyte or electrodes. A brief degradation test demonstrated a minor loss in the electrochemical performance of the cell. Thus, it was demonstrated that direct electrochemical conversion of CO2 to CH4 can be achieved with sufficient productivity using a semi-commercial cell with an active surface of 16 cm2 under conditions compatible with those existing in the state-of-the-art stacks of solid oxide cells.