Electrochemical Conversion Of Carbon Dioxide Research Articles

Unraveling the Interfacial Polarization Effect between Pd and Polymeric Carbon Nitride toward Efficient CO2 Electroreduction to CO.

The efficient electrochemical conversion of carbon dioxide (CO2) to carbon monoxide (CO) using renewable energy is an effective route to pursue carbon neutrality. Optimizing the binding energy of CO on palladium (Pd) metal-based materials used in this process is to make sure the timely desorption of CO from their active sites is critical. Tuning the electronic structure of the Pd center is an effective strategy to optimize its catalytic performance. Herein, we rationally design Pd nanoparticles (NPs)/polymeric carbon nitride (CN) (Pd/CN) composite, which alters the electronic structure of Pd by introducing the interfacial polarization effect to accelerate CO desorption and improve CO selectivity of Pd catalyst. The optimized Pd/CN exhibits a CO Faradaic efficiency of 92.7% at -0.9 V versus reversible hydrogen electrode in CO2-saturated 0.1 M KHCO3 solution. Experimental investigations and theoretical calculations jointly confirm that the enhanced CO selectivity and stability originate from the electron transfer at the Pd/CN interface, and the weakened *CO adsorption on the palladium hydride surface.

Guiding CO2RR Selectivity by Compositional Tuning in the Electrochemical Double Layer.

The electrochemical conversion of carbon dioxide to value-added chemicals provides an environmentally benign alternative to current industrial practices. However, current electrocatalytic systems for the CO2 reduction reaction (CO2RR) are not practical for industrialization, owing to poor specific product selectivity and/or limited activity. Interfacial engineering presents a versatile and effective method to direct CO2RR selectivity by fine-tuning the local chemical dynamics. This Account describes interfacial design strategies developed in our laboratory that use electrolyte engineering and porous carbon materials to modify the local composition at the electrode-electrolyte interface.Our first strategy for influencing surface reactivity is to perturb the electrochemical double layer by tuning the electrolyte composition. We approached this investigation by considering how charged molecular additives can organize at the electrode surface and impact CO2 activation. Using a combination of advanced electrochemical techniques and in situ vibrational spectroscopy, we show that the surfactant properties (the identity of the headgroup, alkyl chain length, and concentration) as well as the electrolyte cation identity can affect how surfactant molecules assemble at a biased electrode. The interplay between the electrolyte cations and the surfactant additives can be regulated to favor specific carbon products, such as HCOO-, and suppress the parasitic hydrogen evolution reaction (HER). Together, our findings highlight how molecular assemblies can be used to design selective electrocatalytic systems.In addition to the electrolyte design, the local spatial confinement of reaction intermediates presents another strategy to direct CO2RR selectivity. We were interested in uncovering the role of porous carbon-supported catalysts toward selective carbon product formation. In our initial study, we show that carbon porosity can be optimized to enhance C2H4 and CO selectivity in a series of Cu catalysts embedded in a tunable carbon aerogel matrix. These results suggested that local confinement of the active surface plays a role in CO2 activation and motivated an investigation into probing how this phenomenon can be translated to a planar Cu electrode. Our findings show that carbon modifiers facilitated surface reconstruction and regulated CO2 diffusion to suppress HER and improve the C2-3 product selectivity. Given the ubiquity of carbon materials in catalysis, this work demonstrates that carbon plays an active role in regulating selectivity by restricting the diffusion of substrate and reaction intermediates. Our work in tuning the composition of the electrochemical double layer for increased CO2RR selectivity demonstrates the potential versatility in boosting catalytic performance across an array of catalytic systems.

Electrochemical conversion of CO2 using different electrode materials in an Li–K molten salt system

The electrochemical conversion of carbon dioxide to solid carbon using four electrode materials (Ag, Pt, Ni, and Ir) in Li–K molten salts was investigated. The current-time plots indicate that the current in the Ag electrode is higher than that in the other electrodes owing to its high reactivity. Over 12 h, the current gradually increased for the Ag and Ni electrodes, whereas it decreased for the Pt and Ir electrodes. The TG and DTG results showed all carbon samples have similar thermal reactivity, and low crystallinity compared to graphite. The XRD results revealed that the solid carbon produced on the Ag and Pt electrodes had a low crystallinity index because the samples that exhibited high reactivity had a low crystallinity index. The carbon produced on the Ag electrode contained Ag due to corrosion of the electrode in the molten carbonate. According to the SEM images, the nanoparticle sizes of Ag and Pt are smaller than those of Ni and Ir. Many shell shapes are formed from a reaction between CO2 and CO; this reduces the efficiency of carbon production. Comparing the characteristics of the produced carbon, Pt is a suitable material for this system, considering the reactivity and durability.

Insight into the Activity and Selectivity of Nanostructured Copper Titanates during Electrochemical Conversion of CO2 at Neutral pH via In Situ X-ray Absorption Spectroscopy.

The electrochemical conversion of carbon dioxide (CO2) to useful chemical fuels is a promising route toward the achievement of carbon neutral and carbon negative energy technologies. Copper (Cu)- and Cu oxide-derived surfaces are known to electrochemically convert CO2 to high-value and energy-dense products. However, the nature and stability of oxidized Cu species under reaction conditions are the subject of much debate in the literature. Herein, we present the synthesis and characterization of copper-titanate nanocatalysts, with discrete Cu-O coordination environments, for the electrochemical CO2 reduction reaction (CO2RR). We employ real-time in situ X-ray absorption spectroscopy (XAS) to monitor Cu species under neutral-pH CO2RR conditions. Combination of voltammetry and on-line electrochemical mass spectrometry with XAS results demonstrates that the titanate motif promotes the retention of oxidized Cu species under reducing conditions for extended periods, without itself possessing any CO2RR activity. Additionally, we demonstrate that the specific nature of the Cu-O environment and the size of the catalyst dictate the long-term stability of the oxidized Cu species and, subsequently, the product selectivity.

Interface rich CuO/Al2CuO4 surface for selective ethylene production from electrochemical CO2 conversion

In this work, we designed a novel CuO/Al2CuO4 catalyst by a phase and interphase engineering approach, which enables the electrochemical conversion of carbon dioxide to ethylene with ultrahigh activity and selectivity.

Boosting CO desorption on dual active site electrocatalysts for CO2 reduction to produce tunable syngas

The electrochemical conversion of CO 2 to generate syngas (H 2 and CO) is regarded as a promising alternative technique to facilitate CO 2 reduction in the ambient atmosphere. However, it is still a great challenge to acquire high catalytic activity with an adjustable H 2 /CO ratio over a wide range. Here, we construct an electrocatalyst with Fe-containing dual active sites on N-doped porous carbon (Fe/FeN 4 C) to promote a CO 2 reduction reaction for tunable syngas production. The Fe/FeN 4 C catalysts have a positive onset potential (−0.18 V RHE ), approximately 100% of the sum of the Faradaic efficiency (FE) of CO and H 2 , a high total current density (>39.33 mA cm −2 ), and a wide H 2 /CO ratio (1.09∼7.08). Density functional-theory calculations suggest that the Fe single atoms dispersed into the N-doped carbon structure, along with the incorporation of Fe nanoparticles, may decrease the adsorption energy of ∗CO, thus synergistically enhancing the catalytic activity. Fe/FeN 4 C serves as a dual active site catalyst for CO 2 RR to syngas The Fe/FeN 4 C catalyst displays superior CO 2 RR performance toward syngas DFT study confirms the decrease in ∗CO adsorption energy benefits syngas production There is interest in developing active catalysts for the electrochemical conversion of carbon dioxide to syngas with a tunable H 2 /CO ratio. Here, Hua et al. report Fe-containing, N-doped, porous carbon to promote CO 2 reduction for tunable syngas production.

Investigation of an electrochemical conversion of carbon dioxide to ethanol and solid oxide fuel cell, gas turbine hybrid process

An integrated system including solid oxide fuel cell (SOFC)-gas turbine power plant and further combine this two equipment with electrochemical conversion of carbon dioxide (CO2) to ethanol is presented and analyzed. In this operation, heat, power and ethanol (as a fuel) are produced. Analyses of energy and exergy achieved along with cells potential and efficiency of total system. The developed SOFC electrochemical model and conversion of CO2 to ethanol is validated with other studies. Main parameters and thermodynamic package of combined system are analyzed. The system net power is calculated to be 491.3 kW. Results demonstrated that electrical efficiency without parametric study in best situation was 63%. The power of gas turbine and heat recovery were obtained 121 kW and 14.8 kW, respectively. According to cell polarization curve, the maximum power density of SOFC occurred in 1.6 A per square centimeter. Electrochemical conversion of CO2 to ethanol (ECCE) with 89.9% exergy efficiency has high efficiency compared with other components. With this research conditions, ECCE produced 23.4 kW net power (5.3% of the overall power production) that with the presence of ECCE the total efficiency of hybrid system increased 4.8% compared to its absence. In parametric study, results showed that overall efficiency and electrical efficiency can reach 72.5% and 66.5% respectively. Also the reformer temperature and after that the fuel utilization have most impacts on the electrical efficiency.

Correlation between impedance spectroscopy and bubble-induced mass transport in the electrochemical reduction of carbon dioxide

In the electrochemical conversion of carbon dioxide, high currents need to be employed to obtain large production rates, thus implying that mass transport of reactants and products is of crucial importance. This aspect can be investigated by employing a model that depicts the local environment for the reduction reactions. Simultaneously, electrochemical impedance spectroscopy, despite being a versatile technique, has rarely been adopted for studying the mass transport features during the carbon dioxide (CO2) electroreduction. In this work, this aspect is deeply analyzed by correlating the results of impedance spectroscopy characterization with those obtained by a bubble-induced mass transport modeling under controlled diffusion conditions on a gold rotating disk electrode. The effects of potential and rotation rate on the local environment are also clarified. In particular, it has been found that CO2 depletion occurs at high kinetics when the rotation is absent, giving rise to an increment of the competing hydrogen evolution reaction. This feature reflects in an enlargement of the diffusion resistance, which overcomes the charge transport one.

Amine-Functionalized Carbon Nanodot Electrocatalysts Converting Carbon Dioxide to Methane.

The electrochemical conversion of carbon dioxide (CO2 ) to methane (CH4 ), which can be used not only as fuel but also as a hydrogen carrier, has drawn great attention for use in supporting carbon capture and utilization. The design of active and selective electrocatalysts with exceptional CO2 -to-CH4 conversion efficiency is highly desirable; however, it remains a challenge. Here a molecular tuning strategy-in situ amine functionalization of nitrogen-doped graphene quantum dots (GQDs) for highly efficient CO2 -to-CH4 conversion is presented. Amine functionalized nitrogen-doped GQDs achieve a CH4 Faradic efficiency (FE) of 63% and 46%, respectively, at CH4 partial current densities of 170 and 258mA cm-2 , approximating to or even outperforming state-of-the-art Cu-based electrocatalysts. These GQDs also convert CO2 to C2 products mainly including C2 H4 and C2 H5 OH with a maximum FE of ≈10%. A systematic analysis reveals that the CH4 yield varies linearly with amine group content, whereas the C2 production rate is positively dependent on pyridinic N dopant content. This work provides insight into the rational design of carbon catalysts with CO2 -to-CH4 conversion efficiency at the industrially relevant level.

CO2 Electrolyzer to Produce Formic Acid Using Flue Gas at Industry Relevant Current Density

The electrochemical conversion of carbon dioxide (CO2) into valuable fuels and feedstocks has gained great attention recently due to the global urgency to mitigate the rapid climate change. A wide variety of chemicals can be obtained through the electrochemical CO2 reduction reaction (CO2RR). Among all the chemicals generated through CO2RR, formic acid has attracted great interest because of its wide applications in silage preservation in agriculture, as an antibacterial agent in animal food additives, as a chemical additive in leather and tanning processing, as a chemical component in textile dyeing and finishing, as a reagent in pharmaceutical and chemical synthesis, and as deicing agents and a component in drilling fluids. Recently, the use of formic acid as a feedstock for biorefineries has also attracted increasing interest.Over the past decade, much effort has been devoted to the prospects of electrochemical CO2 conversion to formic acid. However, issues including low current density, low selectivity, low energy efficiency, lack of long-term stability evaluation, and production of formate salts instead of formic acid remain as the great challenges for the development and commercialization of this technology. Additionally, up to date, most of the electrochemical CO2 reduction work has been conducted in idealized laboratory conditions, such as feeding pure CO2 gas in the electrochemical cell. However, when CO2 is emitted with flue gas, reduced CO2 composition and different contaminants are present. If one wants to use flue gas as the source of CO2 for CO2RR to reduce CO2 emission and embrace circular economy, it is critical to identify the potential effect of the contaminants and CO2 composition on CO2RR. Thus, appropriate treatments and catalysts can be developed to mitigate the detrimental effects if any when a flue gas stream is used as the source of CO2.Recently, Dioxide Materials (DM) has developed an electrolyzer technology that can directly convert CO2 to pure formic acid using a three-compartment CO2 electrolyzer. In this work, we will present our recent efforts on how to run CO2 electrolyzers to produce pure formic acid using a flue gas as CO2 source at an industry relevant current density (200 mA/cm2). The testing results showed that the CO2 electrolyzer could directly produced formic acid with concentration and Faradaic efficiency (FE) up to 16 wt% (3.6 M) and 91%, respectively, depending on the operation conditions. We also investigated how the CO2 composition and impurities in the flue gas affect the electrolyzer performance. The electrolyzer operation results with 14, 50, 100 vol% CO2 at 200 mA/cm2 indicated that the electrolyzer shared similar performance with 50 and 100 vol% CO2 while the one with 14 vol% CO2 showed slightly lower performance. Among the impurities (O2, NOx and SOx) tested, O2 presents the most detrimental effect on CO2 electrolzyer performance. The detailed effects of O2, as well as NOx and SOx on the electrolyzer performance will be presented. Lastly, the long-term (1000 h) performance of the electrolyzer at different conditions and the strategy to maintain the performance will be discussed, as well as the ongoing efforts to test the device at a coal fired power plant. Figure 1

Enhancement of Activity of Copper Sites Toward Electroreduction of Carbon Dioxide through Hierarchical Deposition of Metal Oxide Cocatalysts

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties. There has been growing interest in the electrochemical conversion of carbon dioxide (a potent greenhouse gas and a contributor to global climate change) to useful carbon-based fuels or chemicals. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large over-potentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the electrochemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered.We explore here the ability of polynuclear transition metal oxide based systems to function as cocatalysts and to stabilize and activate metal nanocenters. Here certain nanostructured metal oxides of zirconium, titanium, molybdenum or tungsten have been demonstrated to influence supported catalytic metal sites in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ru), thus affecting their chemisorptive and catalytic properties during CO2-reduction. Metal oxide (WO3, MoO3, TiO2) nanostructures can generate highly reactive –OH groups at electrocatalytic interface.Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Pd), thus affecting their chemisorptive properties. Metal oxide (ZrO2, WO3) nanospecies can generate –OH groups at electrocatalytic interface. Our electrocatalytic results with copper nanostructures over-coated with ZrO2 or WO3 nanostructures imply the systems’ improved selectivity toward CO2-reduction relative to the competitive hydrogen evolution as well as the lower tendency of copper sites to undergo poisoning.

Electrocatalytic conversion of CO2 over in-situ grown Cu microstructures on Cu and Zn foils

Electrochemical conversion of carbon dioxide to value added multi-carbon products is of great importance and a promising approach to mitigate greenhouse gases. In this work, we report the fabrication of electrodes by depositing Cu over the metallic foils of Cu and Zn, which show high faradic efficiency for the conversion of CO2 to formic acid, acetate, and methanol. The morphology, phase and oxidation state of the Cu were different on the two foils while maintaining the same synthesis steps. The Cu particles embedded on Cu foil (Cu/Cu-foil) are in 3D cuboids form with flat and smooth faces, whereas Cu on Zn foil (Cu/Zn-foil) emerge in the shape of 3D flowers with the club of Cu microspikes grown perpendicularly from a root. For the electrocatalytic conversion of CO2, the Cu/Cu-foil shows a high selectivity for formic acid and ethyl acetate with the highest faradaic efficiency of 78 % at −0.3 V vs RHE, and 64 % at −1.0 V (vs RHE) for the two products, respectively. In contrast, the Cu/Zn-foil displays a high selectivity towards methanol, with the highest faradaic efficiency of 48 % at −1.0 V vs RHE, indicating that the product selectivity can be easily modulated by changing the metallic foil on which the Cu particles are deposited. Both the electrodes, Cu/Cu-foil and Cu/Zn-foil, show long-term stable performance while maintaining the selectivity of the products during CO2 electrocatalytic conversion.

Electrochemical production of formic acid from carbon dioxide: A life cycle assessment study

Even though lab-scale experimental studies have shown the technological potential of the electrochemical conversion of carbon dioxide (CO2) to formic acid (FA), there are few studies that have evaluated the environmental feasibility of such a conversion. This study develops an integrated process consisting of a three-compartment cell reaction system and a pressure-swing distillation separation system to produce commercial-grade FA from CO2. A total of 18 environment impact categories, including climate change and fossil depletion, are estimated for the process configurations on a system level. The electrochemical process has a 12.4–99.7% reduced environmental impact except for terrestrial ecotoxicity, compared to the conventional FA production process using carbon monoxide obtained from fossil fuels. In 17 categories, except that of ionizing radiation, electricity was identified as a major factor (17–97%) affecting the environment. A reduction in the electricity requirements or supply of renewable electricity, such as hydropower, will enable more environment friendly FA production from CO2.

Understanding High-Temperature Electrolysis

Electrolysis is the technology, which provides the key for sector coupling. It enables the conversion of renewable energy to material value generation. Therefore, it is of utmost importance, that the energy is used in the most efficient way. High-temperature electrolysis on solid oxide cells provides high efficiency combined with the possibility to convert both water (H2O) and carbon dioxide (CO2) to hydrogen (H2) and carbon monoxide (CO)[1].For a purposive improvement of the efficiency of the high-temperature electrolysis, a precise understanding of the on-going processes is needed[2]. Both the electrochemical and the procedural processes can have a significant impact on the performance, lifetime and overall effectiveness of the conversions taking place[3]. Some of the outcomes of changing operation parameters have been discussed before, although focusing on specific topics within the field. Therefore, a comprehensive sweep of parameters has to be conducted and results and findings have to be analyzed in full detail[3-6].In this contribution, we show the summary and conclusions of multiple investigations of the high-temperature electrolysis. A series of detailed analysis has been performed using current-voltage characteristics (IV curves) and electrochemical impedance spectroscopy (EIS). The sets of experiments were conducted using commercially available cells (Elcogen) consisting of a Nickel/ 8 mol % Yttrium-Stabilized Zirconia (8YSZ) cermet fuel electrode, an 8YSZ electrolyte, a Cerium Gadolinium Oxide barrier layer and a Lanthanum Strontium Cobaltite air electrode. The variation of parameters included feed gas compositions ranging from pure water electrolysis to pure carbon dioxide electrolysis and co-electrolysis in between, temperature range of 650 °C to 900 °C, flow rates with various space-velocities, current densities from OCV up to over 2 A·cm2 and measurement times up to 500 h. In parallel a full-scale model was developed starting from fundamental thermodynamics over applied kinetics using Comsol software, in order to compare the experimental results and evaluation with the simulation results. As a first result, we are able to show a solution to the discussion of the role and impact of the direct electrochemical conversion of carbon dioxide during co-electrolysis. This is a first essential step for the understanding of high-temperature electrolysis in general. Foit, S.R.; Vinke, I.C.; de Haart, L.G.J.; Eichel, R.-A. Power-to-syngas: An enabling technology for the transition of the energy system? Angew. Chem. Int. Ed. 2017, 56, 5402-5411.Foit, S.R.; Dittrich, L.; Vibhu, V.; Vinke, I.C.; Eichel, R.-A.; de Haart, L.G.J. Co-electrolysis, quo vadis? ECS Transactions 2017, 78, 3139-3147.Dittrich, L.; Nohl, M.; Theuer, T.; Foit, S.; Vinke, I.C.; de Haart, L.G.J.; Eichel, R.-A. Co-electrolysis – a sustainable technology for syngas production. Chem. Ing. Tech. 2018, 90, 1158-1159.Theuer, T.; Schäfer, D.; Dittrich, L.; Nohl, M.; Foit, S.; Blum, L.; Eichel, R.-A.; de Haart, L.G.J. Sustainable syngas production by high-temperature co-electrolysis. Chem. Ing. Tech. 2020, 92, 40-44.Foit, S.; Dittrich, L.; Duyster, T.; Vinke, I.; Eichel, R.-A.; de Haart, L.G.J. Direct solid oxide electrolysis of carbon dioxide: Analysis of performance and processes. Processes 2020, 8, 1390.Dittrich, L.; Nohl, M.; Jaekel, E.E.; Foit, S.; de Haart, L.G.J.; Eichel, R.-A. High-temperature co-electrolysis: A versatile method to sustainably produce tailored syngas compositions. J. Electrochem. Soc. 2019, 166, F971-F975. Figure 1

Polymer-Supported Liquid Layer Electrolyzer Enabled Electrochemical CO2 Reduction to CO with High Energy Efficiency.

The electrochemical conversion of carbon dioxide (CO2) to carbon monoxide (CO) is a favorable approach to reduce CO2 emission while converting excess sustainable energy to important chemical feedstocks. At high current density (>100 mA cm−2), low energy efficiency (EE) and unaffordable cell cost limit the industrial application of conventional CO2 electrolyzers. Thus, a crucial and urgent task is to design a new type of CO2 electrolyzer that can work efficiently at high current density. Here we report a polymer‐supported liquid layer (PSL) electrolyzer using polypropylene non‐woven fabric as a separator between anode and cathode. Ag based cathode was fed with humid CO2 and potassium hydroxide was fed to earth‐abundant NiFe‐based anode. In this configuration, the PSL provided high‐pH condition for the cathode reaction and reduced the cell resistance, achieving a high full cell EE over 66 % at 100 mA cm−2.

Electrochemical conversion of carbon dioxide in molten salts: In-situ and beyond

Molten salt electrochemistry shows promise as a new platform for conversion of carbon-based fuels with reduced carbon emissions.

Hierarchical Ti3C2Tx MXene/Carbon Nanotubes for Low Overpotential and Long-Life Li-CO2 Batteries.

Electrochemical carbon dioxide conversion at ambient temperature is an efficient route to synchronously provide a continuous power supply and produce useful chemicals such as carbonates. Rigid catalysts with rational morphological and structural design are used to overcome the sluggish reaction kinetics and contribute to a better cycle life in Li-CO2 batteries. In this report, a two-dimensional Ti3C2Tx MXene/carbon heterostructure assembled parallel-aligned tubular architecture was delicately synthesized through a self-sacrificial templating method and delivered an ultralow overpotential of 1.38 V at 0.2 A·g-1. The heterostructure that inherited the high catalytic performance of Ti3C2Tx MXene and the outstanding stability of carbon material promoted the adsorption of CO2 and accelerated the decomposition of lithium carbonate, which was proved by in situ and ex situ characterizations and density functional theory calculations. The tubular architecture with large surface area was demonstrated to provide a high durability for long cycle life and ensure good contacts among gas, electrolyte, and electrode.

High Facets on Nanowrinkled Cu via Chemical Vapor Deposition Graphene Growth for Efficient CO2 Reduction into Ethanol

Achieving high electrochemical conversion of carbon dioxide (CO2) into valuable fuels and chemicals is one of the most promising directions to address environmental and energy challenges. Although several single-crystal based studies and simulation results have reported that rich in steps on Cu (100) surfaces are favorable to convert toward C2 alcohol products, most studies are still stuck in low-index (100) facets or surface defect-derived low density of step-sites. In the present work, we report the high production of ethanol by synthesizing a wrinkled Cu catalyst with high facets via a chemical vapor deposition (CVD) graphene growth process. Under our approach, we used graphene as a guiding material to produce wrinkled Cu film for use as an electrocatalyst. The graphene-grown Cu films are not only mass-producible but composed of a high density of step-sites with high-facet atomic arrangements, including the (200) and (310) facets, which are difficult to synthesize using existing methods. The wrinkled Cu film with a unique atomic arrangement showed high ethanol selectivity, achieving 40% faradaic efficiency (FE) at −0.9 V vs reversible hydrogen electrode (RHE), one of the largest selectivity values reported thus far for a Cu-based CO2 conversion catalyst. The C2 selectivity and productivity was 57% FE and −2.2 mA/cm2 at −1.1 V vs RHE, respectively. Density functional theory (DFT) calculation results demonstrated that such a high ethanol productivity is mainly attributable to the (310) facet of the wrinkles, which feature a low C–C coupling barrier (0.5 eV) and a preferred reaction path toward ethanol among other products.

SnS Nanoparticles Grown on Sn-Atom-Modified N,S-Codoped Mesoporous Carbon Nanosheets as Electrocatalysts for CO2 Reduction to Formate

Electrochemical conversion of carbon dioxide (CO2) to formate provides a method for the synthesis of valuable fuels and chemical products. Herein, SnS nanoparticles were grown in situ on Sn-atom-modified N,S-codoped mesoporous carbon nanosheets. As a result, a novel nanohybrid (NH) catalyst named SnS/Sn-NSC NH was obtained for CO2 electroreduction for formate production. In the obtained NHs, the synergistic effect of SnS nanoparticles (∼2.2 nm) with Sn atoms in the carbon matrix and the 3D hierarchical porous structure could provide more active sites and shorten the diffusion pathway, thereby improving the performance of CO2 reduction. The SnS/Sn-NSC NH showed a high Faradaic efficiency (FE) of formate of 91% at a low potential of −0.7 V (vs reversible hydrogen electrode, RHE). In particular, the SnS/Sn-NSC NH demonstrated a favorable FEformate value of over 80% over a wide potential range. On the basis of spectroscopic characterizations, electrochemical tests, and CO2 adsorption analyses, the origin of the enhanced catalytic performance was suggested. This work offers an efficient strategy to construct 3D hierarchical SnS/Sn-NSC NHs for enhancing formate productivity through CO2 electrocatalytic reduction.

Electrochemical conversion of carbon dioxide over silver-based catalysts: Recent progress in cathode structure and interface engineering

Electrochemical CO2 reduction (ECR) to CO and other high-value chemicals is emerging as a prominent technology, which entails using the electricity produced from renewable energy resources to convert the problematic CO2 greenhouse gas into value-added chemicals and fuels. In addition to Au electrocatalysts, which are high-cost materials, Ag-based electrocatalysts have been regarded as promising ECR to CO alternatives in recent years, especially with their excellent activity and lowered cost of electrocatalyst synthesis because Ag is much more abundant and inexpensive. In this study, we firstly introduce some possible reaction mechanisms for Ag electrocatalysts in ECR to CO. To identify an outstanding strategy to develop a guideline for Ag-based electrocatalysts, we comprehensively reviewed recent advances in material development and interfacial engineering based on some critical factors and effects. Finally, a summary and prospects toward the future development of electrocatalysts for ECR are provided.