Electrocatalysts For CO2 Reduction Research Articles

Tailoring the catalytic microenvironment of CuO with hydrophobic CuSA2 for selective CO2 electroreduction to C2+ products

Advancing the Faraday efficiency (FE) and current density of Cu catalyzed electrochemical CO2 reduction (ECR) reaction to produce C2+ products is important for its practical applications. Constructing a hydrophobic interface to regulate the local reaction environment is an effective method to improve the selectivity of C2+ products, but it is limited by the low reaction current density. In this work, we fabricated a novel hydrophobic and ECR active copper stearate (CuSA2) decorated CuO nanoparticle catalyst (CuO/CuSA2) for ECR reaction toward C2+ products. As a result, the CuO/CuSA2 catalyst achieved an FE of 61.33 % and a partial current density of 429.33 mA cm−2 for C2+ products. The CuSA2 and CuO nanoparticle cooperate very well for the formation of C2+ products. The in-situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and electrochemical adsorption experiment indicated that the hydrophobic CuSA2 regulated the local ECR reaction environment. The local ∗CO2.- and *CO adsorption were strengthened by hydrophobic CuSA2 modification while the H2O adsorption was inhibited. CuO nanoparticle promotes *CO coupling reaction and enhances C2 intermediates (*OCCOH and *OC2H5) adsorption. Hydrophobic CuSA2 and CuO nanoparticle synergistically promote the generation of C2+ products. This work provides new insights into the design of hydrophobic CO2 reduction electrocatalysts for the preparation of C2+ products.

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.

Phase transfer-assisted indium recovery from spent liquid crystal display panels and its extension in preparing indium-based electrocatalysts for CO2 reduction

Transforming discarded electronic devices into low-cost and high-efficiency catalysts presents a win–win approach to address the scarcity of rare resources and sustainable energy challenges. Herein, we report an effective strategy that combines an ethanol-mediated dodecylamine (DDA) phase transfer with hydrothermal methods for facilitating the facile synthesis of indium (In)-based nanomaterials from the leachates of liquid crystal display panels (LCDPs) toward high-efficiency electrochemical CO2 reduction reaction (eCO2RR). In this strategy, the rapid formation of coordinating compounds between the –NH2 group of DDA and metal ions facilitates the separation of In3+ cations from the acidic LCDPs leach solution by transferring them into an organic phase, which are then converted into InOOH nanoparticles with abundant oxygen vacancies (denoted as In-LCDPs and hereafter) through a low-temperature hydrothermal process. The eCO2RR evaluations confirm the superior electrocatalytic performance of the In-based nanoparticles produced from the LCDPs. In specific, within a broad potential range (−0.77 to −1.17 V vs RHE), the In-LCDPs show a Faradaic efficiency for formate (FEformate) of 85 %, with the highest FEformate of 90.23 % at −0.97 V vs RHE, which is comparable to the FEformate (93.8 % at −0.97 V vs RHE) of In-based catalyst prepared from pure In precursors using the same method. Further investigations reveal that the Sn and Al impurities have minimal impact on the catalytic performance of In-LCDPs, while the presence of Fe3+ impurities significantly enhance the production of hydrogen during the eCO2RR. This work might have provided a scalable pathway to transform LCDPs into value-added electrocatalysts for eCO2RR.

Nitrided copper-iron composite oxides derived from layered double hydroxides for enhanced carbon dioxide electroreduction to methane and formic acid

The reduction of carbon dioxide into valuable chemical products is a promising solution to address carbon balance and energy issues. Herein, amorphous nitrided copper-iron oxides are prepared by gas-phase nitriding of CuFe-layered double hydroxide precursors with urea as a nitrogen source. The obtained materials show high activity for CO2 electroreduction to methane and formic acid, achieving a total Faraday efficiency of 74.7% at −0.7 V vs. RHE and exhibiting continuous 10 h durability in the H-cell. The uniformly distributed Cu+ sites act as active sites by losing electrons to activate CO2. During the CO2 electroreduction, CO2 is converted to *COOH via proton-electron coupling; *COOH combines directly with a proton in solution to produce the HCOOH product; and the other part of *COOH undergoes a protonated dehydration process to form the *CHO intermediate, which dehydrates again to form CH4. This study provides a new approach for designing CO2 electroreduction catalysts.

Composition effects of electrodeposited Cu-Ag nanostructured electrocatalysts for CO2 reduction

The electrochemical carbon dioxide reduction (CO2RR) on Cu-based catalysts is a promising strategy to store renewable electricity and produce valuable C2+ chemicals. We investigate the CO2RR on Cu-Ag nanostructures that have been electrodeposited in a green choline chloride and urea deep eutectic solvent (DES). We determine the electrochemically active surface area (ECSA) using lead underpotential deposition (UPD) to investigate the CO2RR intrinsic activity and selectivity. We show that the addition of Ag on electrodeposited Cu primarily suppresses the production of hydrogen and methane. While the production of carbon monoxide slightly increases, the partial current of the total C2+ products does not considerably increase. Despite that the production rate of C2+ is similar on Cu and Cu-Ag, the addition of Ag enhances the formation of alcohols and oxygenates over ethylene. We highlight the potential of metal electrodeposition from DES as a sustainable strategy to develop bimetallic Cu-based nanocatalysts for CO2RR.

NHC-CDI Ligands Boost Multicarbon Production in Electrocatalytic CO2 Reduction by Increasing Accumulated Charged Intermediates and Promoting *CO Dimerization on Cu.

Copper-based materials exhibit significant potential as catalysts for electrochemical CO2 reduction, owing to their capacity to generate multicarbon hydrocarbons. The molecular functionalization of Cu electrodes represents a simple yet powerful strategy for improving the intrinsic activity of these materials by favoring specific reaction pathways through the creation of tailored microenvironments around the surface active sites. However, despite its success, comprehensive mechanistic insights derived from experimental techniques are often limited, leaving the active role of surface modifiers inconclusive. In this work, we show that N-heterocyclic carbene-carbodiimide-functionalized Cu catalysts display a remarkable activity for multicarbon product formation, surpassing bare Cu electrodes by more than an order of magnitude. These hybrid catalysts operate efficiently using an electrolyzer equipped with a gas diffusion electrode, achieving a multicarbon product selectivity of 58% with a partial current density of ca. -80 mA cm-2. We found that the activity for multicarbon product formation is closely linked to the surface charge that accumulates during electrocatalysis, stemming from surface intermediate buildup. Through X-ray photoelectron spectroscopy, we elucidated the role of the molecular additives in altering the electronic structure of the Cu electrodes, promoting the stabilization of surface CO. Additionally, in situ Raman measurements established the identity of the reaction intermediates that accumulate during electrocatalysis, indicating preferential CO binding on Cu step sites, known for facilitating C-C coupling. This study underscores the significant potential of molecular surface modifications in developing efficient electrocatalysts for CO2 reduction, highlighting surface charge as a pivotal descriptor of multicarbon product activity.

Electrocatalytic reduction of CO2 by Co-Cu metastable alloy nanoparticles derived from MOFs

The construction of non-noble metal electrodes for the catalytic reduction of CO2 has drawn much attention in recent years. Herein, a facile CoCu@C composite catalyst was synthesized by simply carbonizing CoCu-MOFs, a bimetal MOFs fabricated by integrating Cu2+ ions into the synthesis of ZIF-67. Co-Cu alloy nanoparticles were closely embedded in porous carbon skeleton. Notably, the optimal Co1Cu3@C sample exhibited a total catalytic current of 29.8 mA·cm−2 at −0.7 V vs RHE, which was 2.56 times of the Co@C catalyst derived from original ZIF-67. Besides, the Co1Cu3@C sample achieved targeted CO:H2 ratios in the CO2 reduction reactions, covering approximately 1:1.7–1:4, meeting well with industrial needs. Density Functional Theory (DFT) calculations unveiled an electron migration from Co to Cu within the alloy, indicating the promoted transfer of electrons. Co atoms in Co-Cu alloy was found as the predominant active sites for the reduction of CO2. The study provided a economical CO2 reduction electrocatalyst with cheap feedstock, low operating voltage and specific ratio of syngas. Additionally, this work significantly advances our understanding of Co-Cu alloy electrocatalysts, providing crucial insights for the ongoing evolution of electrocatalyst research in material preparation and theoretical calculations.

Biomass-based carbon aerogels with interconnected pores and controllable Zn–N sites for CO2 electroreduction

The rational design of renewable, highly active, and selective catalysts has always been the key to the practical application of CO2 electroreduction. In this study, biomass-based Zn/N doped carbon aerogels were fabricated for high-selectivity electrical reduction of CO2 to CO. After in situ Zn/N doping, carbon aerogels exhibited interconnected pores, high surface area, and exposed active sites, and their physicochemical properties are significantly affected by pyrolysis temperature. When the pyrolysis temperature increased to 950 °C, the number of surface active sites and pore structure parameters of carbon aerogels decreased significantly due to the escape of zinc and nitrogen. CAZN-850 exhibited the highest specific surface area of 1317.0 m2/g and abundant Zn–N sites, which results in its high activity and selectivity for electroreduction of CO2 to CO (FECO = 89 % at −1.0V vs. RHE). Moreover, the stability test results for CO2RR showed that the reduction value of FECO for Zn/N doped carbon aerogels was only 5 % under long-time operation. This work provides a new idea for the design of biomass-based catalysts for CO2 electroreduction.

Gray mesoporous SnO2 catalyst for CO2 electroreduction with high partial current density and formate selectivity

The mesoporous metal oxide semiconductors exhibit unique chemical and physical characteristics, making them highly desirable for catalysis, electrochemistry, energy conversion, and energy storage applications. Here, we report the facial fabrication of mesoporous gray SnO2 (MGS) electrocatalysts employing an evaporation-induced co-assembly (EICA) approach, utilizing poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymers Pluronic P123 (PEO-PPO-PEO) triblock copolymer as a template for electrochemical CO2 reduction reaction (eCO2RR). By sustaining the co-assembly conditions and utilizing a thermal treatment technique based on carbon, gray mesoporous SnO2 materials with a high density of active sites and oxygen vacancies can be constructed. The MGS materials were employed in eCO2RR in a flow cell type, which exhibits excellent catalytic activity and selectivity toward formate with a high partial current density of −234 mA cm−2 and Faradaic efficiency (FE) of 93.60 % at −1.3 V vs. reversible hydrogen electrode (RHE). Interestingly, the mesoporous SnO2 with a 1.5 wt% ratio of Sn precursor to P123 surfactant (MS-1.5@350N-400A) electrode exhibits a high level of Faradaic efficiency (FE) of (98%) at a low overpotential of −0.6 VRHE, which is a seldom recorded performance for similar systems. A stable FE of 96 ± 1% was observed in the range of −0.6 to −1.2 VRHE, which is the result of a large surface area (184 m2/g) and a high number of active sites and oxygen vacancies within the mesostructured framework.

Sustainedly High‐Rate Electroreduction of CO2 to Multi‐Carbon Products on Nickel Oxygenate/Copper Interfacial Catalysts

AbstractCopper (Cu) is the most attractive electrocatalyst for CO2 reduction to multi‐carbon (C2+) products with high economic value in considerable amounts. However, the rational design of a structurally stable Cu‐based catalyst that can achieve high activity and stability towards C2+ products remain a grand challenge. Here, a highly stable nickel oxygenate/Cu electrocatalyst is developed with abundant NiOOH/Cu interfaces by in situ electrochemical reconstruction. The nickel oxygenate/Cu electrocatalyst achieves a superior Faradaic efficiency of 86.3 ± 3.0% and a record partial current density of 2085 A g−1 for C2+ products with long‐term stability. In situ experimental and theoretical studies demonstrates that the exceptional performance in generating C2+ products is attributed to the presence of the NiOOH/Cu interfaces which increase *CO coverage, lower energy barrier for *CO coupling and stabilize *OCCO simultaneously. This work provides new insights into the rational design of electrocatalysts to achieve stable and efficient electrocatalytic CO2 reduction capabilities.

Efficient Lead Removal by Assembly of Bio-Derived Ellagate Framework, Which Enables Electrocatalytic Reduction of CO2 to Formate.

Lead (Pb) poisoning and CO2-induced global warming represent two exemplary environmental and energy issues threatening humanity. Various biomass-derived materials are reported to take up Pb and convert CO2 electrochemically into low-valent carbon species, but these works address the problems separately rather than settle the issues simultaneously. In this work, cheap, natural ellagic acid (EA) extracted from common plants is adopted to assemble a stable metal-organic framework (MOF), EA-Pb, by effective capture of Pb2+ ions in an aqueous medium (removal rate close to 99%). EA-Pb represents the first structurally well-defined Pb-based MOF showing selective electrocatalytic CO2-to-HCOO- conversion with Faradaic efficiency (FE) of 95.37% at -1.08V versus RHE. The catalytic mechanism is studied by 13CO2 labeling, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and theoretical calculation. The use of EA-Pb as an electrocatalyst for CO2 reduction represents a 2-in-1 solution of converting detrimental wastes (Pb2+) as well as natural resources (EA) into wealth (electrocatalytic EA-Pb) for addressing the global warming issue.

Synergistic Effects of Doping and Strain in Bismuth Catalysts for CO2 Electroreduction.

Doping is a recognized method for enhancing catalytic performance. The introduction of strains is a common consequence of doping, although it is often overlooked. Differentiating the impact of doping and strain on catalytic performance poses a significant challenge. In this study, Cu-doped Bi catalysts with substantial tensile strain are synthesized. The synergistic effects of doping and strain in bismuth result in a remarkable CO2RR performance. Under optimized conditions, Cu1/6-Bi demonstrates exceptional formate Faradaic efficiency (>95%) and maintains over 90% across a wide potential window of 900 mV. Furthermore, it delivers an industrial-relevant partial current density of -317 mA cm-2 at -1.2 VRHE in a flow cell, while maintaining its selectivity. Additionally, it exhibits exceptional long-term stability, surpassing 120 h at -200 mA cm-2. Through experimental and theoretical mechanistic investigations, it has been determined that the introduction of tensile strain facilitates the adsorption of *CO2, thereby enhancing the reaction kinetics. Moreover, the presence of Cu dopants and tensile strain further diminishes the energy barrier for the formation of *OCHO intermediate. This study not only offers valuable insights for the development of effective catalysts for CO2RR through doping, but also establishes correlations between doping, lattice strains, and catalytic properties of bismuth catalysts.

Large language model enhanced corpus of CO2 reduction electrocatalysts and synthesis procedures

CO2 electroreduction has garnered significant attention from both the academic and industrial communities. Extracting crucial information related to catalysts from domain literature can help scientists find new and effective electrocatalysts. Herein, we used various advanced machine learning, natural language processing techniques and large language models (LLMs) approaches to extract relevant information about the CO2 electrocatalytic reduction process from scientific literature. By applying the extraction pipeline, we present an open-source corpus for electrocatalytic CO2 reduction. The database contains two types of corpus: (1) the benchmark corpus, which is a collection of 6,985 records extracted from 1,081 publications by catalysis postgraduates; and (2) the extended corpus, which consists of content extracted from 5,941 documents using traditional NLP techniques and LLMs techniques. The Extended Corpus I and II contain 77,016 and 30,283 records, respectively. Furthermore, several domain literature fine-tuned LLMs were developed. Overall, this work will contribute to the exploration of new and effective electrocatalysts by leveraging information from domain literature using cutting-edge computer techniques.

Recent Progress in Hollow Fiber Gas Diffusion Electrodes for CO2 Electroreduction

CO2 electroreduction (CO2RR) to high‐value chemicals by renewable energy is a promising route for achieving carbon cycling. Traditional two‐dimensional planar electrodes applied in CO2RR are faced with problems of high mass transfer resistance, carbonate precipitation, flooding, and complicated structures, seriously limiting their CO2RR efficiency and application. Three‐dimensional hollow fiber gas diffusion electrodes (HFGDEs) are promising candidates due to their rich specific surface area, low mass transfer resistance, simplified component, and no flooding trouble, which are beneficial for achieving high current density as well as high CO2RR efficiency. In this review, we provide inspirations and positive paradigms for the rational design of HFGDE toward CO2RR by following part: 1. The mechanism of CO2RR. 2. The classification of the typical metal‐based CO2RR catalysts. 3. The preparation process of HFGDEs. 4. Recent advanced HFGDE studies for CO2RR. 5. Challenges at this stage and future development of HFGDEs towards accelerating application of industrial CO2 reduction electrolyzers.

Investigating the interplay between charge transfer and CO2 insertion in the adsorption of a NiFe catalyst for CO2 electroreduction on a graphite support through DFT computational approaches.

This article describes a density functional theory (DFT) study to explore a bio-inspired NiFe complex known for its experimental activity in electro-reducing CO2 to CH4 when adsorbed on graphite. The coordination properties of the complex are investigated in isolated form and when physisorbed on a graphene surface. A comparative analysis of DFT approaches for surface modeling is conducted, utilizing either a finite graphene flake or a periodic carbon surface. Results reveal that the finite model effectively preserves all crucial properties. By examining predicted structures arising from CO2 insertion within the mono-reduced NiFe species, whether isolated or adsorbed on the graphene flake, a potential species for subsequent electro-reduction steps is proposed. Notably, the DFT study highlights two positive effects of complex adsorption: facile electron transfers between graphene and the complex, finely regulated by the complex state, and a lowering of the thermodynamic demand for CO2 insertion.

Highly efficient electrocatalytic CO2 reduction by a CrIII quaterpyridine complex

Design tactics and mechanistic studies both remain as fundamental challenges during the exploitations of earth-abundant molecular electrocatalysts for CO2 reduction, especially for the rarely studied Cr-based ones. Herein, a quaterpyridyl CrIII catalyst is found to be highly active for CO2 electroreduction to CO with 99.8% Faradaic efficiency in DMF/phenol medium. A nearly one order of magnitude higher turnover frequency (86.6 s-1) over the documented Cr-based catalysts (<10 s-1) can be achieved at an applied overpotential of only 190 mV which is generally 300 mV lower than these precedents. Such a high performance at this low driving force originates from the metal-ligand cooperativity that stabilizes the low-valent intermediates and serves as an efficient electron reservoir. Moreover, a synergy of electrochemistry, spectroelectrochemistry, electron paramagnetic resonance, and quantum chemical calculations allows to characterize the key CrII, CrI, Cr0, and CO-bound Cr0 intermediates as well as to verify the catalytic mechanism.

Enhanced Microbial Protein Production from CO2 and Air by a MoS2 Catalyzed Bioelectrochemical System.

Carbon dioxide can be relatively easily reduced to organic matter in a bioelectrochemical system (BES). However, due to insufficient reduction force from in-situ hydrogen evolution, it is difficult for nitrogen reduction. In this study, MoS2 was firstly used as an electrocatalyst for the simultaneous reduction of CO2 and N2 to produce microbial protein (MP) in a BES. Cell dry weight (CDW) could reach 0.81±0.04 g/L after 14 d operation at -0.7 V (vs. RHE), which was 108±3 % higher than that from non-catalyst control group (0.39±0.01 g/L). The produced protein had a better amino acid profile in the BES than that in a direct hydrogen system (DHS), particularly for proline (Pro). Besides, MoS2 promoted the growth of bacterial cell on an electrode and improved the biofilm extracellular electron transfer (EET) by microscopic observation and electrochemical characterization of MoS2 biocathode. The composition of the microbial community and the relative abundance of functional enzymes revealed that MoS2 as an electrocatalyst was beneficial for enriching Xanthobacter and enhancing CO2 and N2 reduction by electrical energy. These results demonstrated that an efficient strategy to improve MP production of BES is to use MoS2 as an electrocatalyst to shift amino acid profile and microbial community.

Theoretical study on the electrocatalytic CO2 reduction mechanisms using carbon-nanotube-supported carbon-based single metal atom catalysts

In this study, five Ni-doped carbon-based single metal atom catalysts supported by carbon nanotubes, which can be used for electrocatalytic CO2 reduction, were constructed. According to their structures, these catalysts include one Ni phthalocyanine (NiPc) molecule, two di- and tri-coordinated Ni-doped carbon nanoribbons, and two di-/tri-coordination Ni-doped graphene, which are denoted as NiPc/CNT, H2(H3)-Ni/CNT, 2(3)-Ni/CNT respectively. We first optimized their structures and studied the adsorption characteristics of CO2 on these catalysts with PBE+D3 method. Additionally, the electronic structure characteristics were then calculated, and the electrocatalytic mechanisms of CO2 reduction to CO, HCOOH, CH3OH and CH4 using these catalysts were studied in detail. It is found that the electrocatalytic activities of these five catalysts for reducing CO2 follow the order of 2-Ni/CNT>3-Ni/CNT>H3-Ni/CNT>H2-Ni/CNT>NiPc/CNT. As can be seen, the di-coordination catalysts perform best, followed by the tri-coordination catalysts, while the four-coordination NiPc-based catalyst performs worst. Moreover, graphene-based materials have stronger catalytic activities than their nanoribbon counterparts. Apart from these facts, these five catalytic materials may exhibit product selectivity at different limiting potentials, and specific reaction products can therefore be synthesized by controlling the potentials. We simultaneously investigated the mechanism of competing hydrogen evolution reactions in the electrocatalytic reduction of CO2 with five catalysts, and in order to inhibit the competing hydrogen evolution reactions and improve the efficiency of CO2 electrocatalytic reduction, the acidity of the solution can be appropriately reduced. We hope that our present work can provide a theoretical foundation for the future design and synthesis of novel carbon-based electrocatalyst for efficient CO2 reduction.

Potential Dependent Reorientation Controlling Activity of a Molecular Electrocatalyst.

The activity of molecular electrocatalysts depends on the interplay of electrolyte composition near the electrode surface, the composition and morphology of the electrode surface, and the electric field at the electrode-electrolyte interface. This interplay is challenging to study and often overlooked when assessing molecular catalyst activity. Here, we use surface specific vibrational sum frequency generation (VSFG) spectroscopy to study the solvent and potential dependent activation of Mo(bpy)(CO)4, a CO2 reduction catalyst, at a polycrystalline Au electrode. We find that the parent complex undergoes potential dependent reorientation at the electrode surface when a small amount of N-methyl-2-pyrrolidone (NMP) is present. This preactivates the complex, resulting in greater yields at less negative potentials, of the active electrocatalyst for CO2 reduction.

Unveiling mechanisms in Cu2O-catalyzed electroreduction of CO2 through theoretical resolution using periodic boundary and saturation cluster models

The imperative need to reduce atmospheric CO2 to mitigate global warming and advance sustainable energy systems has driven extensive research. Copper oxide (Cu2O) has emerged as a promising catalyst for electroreduction of CO2, yet its catalytic mechanism remains debated. This study employs a theoretical approach to delve into the intricate details of CO2 electroreduction catalyzed by Cu2O. Utilizing both periodic boundary and saturation cluster models, we explore various reaction pathways, successfully identifying key transition states and intermediates with each model. A comprehensive analysis and comparison of results from both models are conducted. To enhance understanding, we develop a method simulating the impact of an electric field, employed to probe the ongoing reaction. Additionally, we consider the solid–liquid interface by introducing solvent molecules and buffer ions into our analysis. This comprehensive theoretical investigation aims to elucidate the mechanism governing the electroreduction of CO2 catalyzed by Cu2O and analogous semiconductor oxides, providing valuable insights into this critical process.