Electrochemical Carbon Dioxide Reduction Reaction Research Articles

Cu-based nano-material catalysts for electrochemical carbon dioxide reduction reaction (CO2RR)

With the emergence of the global energy crisis and global climate change, renewable energy systems, such as fuel cells that turn off energetic oxygen and carbon cycles, are becoming increasingly important. Carbon dioxide reduction reaction (CO_2 RR) is an important electrocatalytic process on the gas diffusion electrode of CO_2 electrolyzer, which has been paid more and more attention by researchers. The problems of high cost, low efficiency, weak selectivity and stability of the carbon dioxide reduction reaction (CO_2 RR) also continue to be solved. Catalysts are considered a viable way to solve these problems. The Cu-based nanomaterial catalyst has been proven to have a good positive effect on the reaction. In this paper, the current research results of Cu-based nanomaterials on CO_2 RR were reviewed, and the catalytic effects of several different Cu-based nanomaterials on CO_2 RR reactions were compared. This paper collected the researches on the catalytic effect of copper-based nanomaterials on carbon dioxide reduction reactions in the past ten years, and found that most copper-based nanomaterials can improve the efficiency of the reactions and show good selectivity. The aim of this paper is to provide a possible catalytic direction for the improvement of carbon dioxide reduction reactions in industry

Uncovering the cation effects on the electroreduction of CO2 on Pd/C catalysts − an SEIRAS study

Electrochemical carbon dioxide (CO2) reduction reaction (CO2RR) has long been known to be affected by the electrolyte cations, yet the interpretations of these effects remain controversial. In this work, taking advantage of the unique catalytic characteristics of Pd, we investigated the cation effects on the CO2RR. It was found that the productions of formate and carbon monoxide (CO) are accelerated, and the competitive hydrogen evolution reaction (HER) is suppressed on Pd surfaces by larger cations. Detailed ATR-SEIRAS measurements revealed the promotion of CO2RR comes from two aspects. First, the CO2 molecules can be concentrated at the electrode–electrolyte interface by larger cations through electrostatic interaction. Second, a stronger interfacial electric field brought by the larger cations can accelerate the CO2RR and stabilize the negatively charged intermediates. The potential-dependent spectral transitions of adsorbed CO and interfacial water shed new light on the cation-dependent electric double layer structures. In light of these findings, the cation effects on the formate and CO pathways at different overpotentials were further revealed.

Plasma induced grain boundaries to boost electrochemical reduction of CO2 to formate

Bismuth-based catalysts are highly promising for the electrochemical carbon dioxide reduction reaction (eCO2RR) to formate product. However, achieving high activity and selectivity towards formate and ensuring long-term stability remains challenging. This work reports the oxygen plasma inducing strategy to construct the abundant grain boundaries of Bi/BiOx on ultrathin two-dimensional Bi nanosheets. The oxygen plasma-treated Bi nanosheet (OP-Bi) exhibits over 90% Faradaic efficiency (FE) for formate at a wide potential range from −0.5 to −1.1 V, and maintains a great stability catalytic performance without significant decay over 30 h in flow cell. Moreover, membrane electrode assembly (MEA) device with OP-Bi as catalyst sustains the robust current density of 100 mA cm−2 over 50 h, maintaining a formate FE above 90%. In addition, rechargeable Zn-CO2 battery presents the peak power density of 1.22 mW cm−2 with OP-Bi as bifunctional catalyst. The mechanism experiments demonstrate that the high-density grain boundaries of OP-Bi provide more exposed active sites, faster electron transfer capacity, and the stronger intrinsic activity of Bi atoms. In situ spectroscopy and theoretical calculations further elucidate that the unsaturated Bi coordination atoms between the grain boundaries can effectively activate CO2 molecules through elongating the C–O bond, and reducing the formation energy barrier of the key intermediate (*OCOH), thereby enhancing the catalytic performance of eCO2RR to formate product.

Atomic Indium‐Doped Copper‐Based Catalysts for Electrochemical CO2 Reduction to C2+ Products

The electrochemical carbon dioxide reduction reaction (CO2RR) holds substantial promise for producing high‐value chemicals and fuels, drawing significant attention from both academia and industry. This work proposes an in‐situelectrodeposition method to prepare indium‐doped copper (Cu)‐based catalysts on carbon paper (Cu100Inx‐CP, x = 3.9, 4.5, 4.8, 5.1, and 7.6, denoting the molar ratio of In to Cu in the catalyst.). The catalysts Cu100Inx‐CP were used for CO2RR to produce multi‐carbon (C2+) products. Characterization results showed that In was highly dispersed in the Cu particles at x<5.1. The Cu100In5.1‐CP (containing 0.95 wt% In based on Cu) was very efficient for electrocatalytic CO2RR. The in‐situ Raman spectroscopy showed that Cu100In5.1‐CP enhanced *CO intermediate adsorption and promoted the production of C2+ products due to the synergistic effect between In and Cu. In doping could suppress HER, enhanced *CO intermediate adsorption, and C‐C coupling for the production of C2+ products in CO2RR.

Cu-phen Coordination Enabled Selective Electrocatalytic Reduction of CO2 to Methane.

Manipulation of selectivity in the catalytic electrochemical carbon dioxide reduction reaction (eCO2RR) poses significant challenges due to inevitable structure reconstruction. One approach is to develop effective strategies for controlling reaction pathways to gain a deeper understanding of mechanisms in robust CO2RR systems. In this work, by precise introduction of 1,10-phenanthroline as a bidentate ligand modulator, the electronic property of the copper site was effectively regulated, thereby directing selectivity switch. By modification of [Cu3(btec)(OH)2]n, the use of [Cu2(btec)(phen)2]n·(H2O)n achieved the selectivity switch from ethylene (faradaic efficiency (FE) = 41%, FEC2+ = 67%) to methane (FECH4 = 69%). Various in situ spectroscopic characterizations revealed that [Cu2(btec)(phen)2]n·(H2O)n promoted the hydrogenation of *CO intermediates, leading to methane generation instead of dimerization to form C2+ products. Acting as a delocalized π-conjugation scaffold, 1,10-phenanthroline in [Cu2(btec)(phen)2]n·(H2O)n helps stabilize Cuδ+. This work presents a novel approach to regulate the coordination environment of active sites with the aim of selectively modulating the CO2RR.

Interface engineering of Cu2O/In(OH)3 for efficient solar-driven CO2 electrochemical reduction to syngas

Electrochemical carbon dioxide reduction reaction (CO2RR) holds greater promise for converting CO2 into value-added chemicals, but designing and manufacturing efficient CO2RR catalysts remains desirable but challenging. Here, the Cu2O/In(OH)3 with heterojunction structure was prepared as an efficient CO2RR electrocatalysts. The optimized Cu2O/In(OH)3–1:1 stabilizes over a wide range of potentials to generate syngas (hydrogen/carbon monoxide, H2/CO) at a ratio of 2:1, and the total Faraday efficiency (FE) remains close to 100 %. However, the ratio of syngas will change to 1:1 when the Cu/In ratio becomes 1:2. In addition, creatively using solar energy to drive the CO2RR system can directly and efficiently achieve the change of solar energy to chemical energy (syngas). Moreover, in-situ experiments show that part of Cu+ is converted to Cu during the CO2RR process, while In(OH)3 remains stable. This work highlights an efficient electrocatalyst for producing syngas based on interface engineering.

Tuning CO2 electroreduction by facet-dependent metal-support interaction

Electrochemical carbon dioxide reduction reaction (CO2RR) helps to build a sustainable carbon cycle system. The selectivity and stability of CO2RR catalysts can be tuned by manipulating Metal-Support Interaction (MSI). Here, we conducted a theoretical and experimental research on the interaction between Ag nanoparticles and diverse crystal faces of Cu2O. It was found the strong electron transfer from Ag to (100) facet of hexahedral Cu2O enabled the formation of charge-redistributed interface with positively charged Ag and negatively charged Cu2O, which was more favorable to the stability of integrated structure and CO2-to-CO catalytic process compared to Ag-decorated octahedral and dodecahedral Cu2O with exposed (111) and (110) facets, respectively. Consequently, the composite of Ag on hexahedral Cu2O exhibited an impressive CO Faradaic efficiency of 93%, surpassing Ag on octahedral and dodecahedral Cu2O as well as individual Ag and Cu2O nanoparticles. This work provides an effective avenue to tune CO2RR process by interface engineering.

Electronic Structure Design of Transition Metal-Based Catalysts for Electrochemical Carbon Dioxide Reduction.

With the increasingly serious greenhouse effect, the electrochemical carbon dioxide reduction reaction (CO2RR) has garnered widespread attention as it is capable of leveraging renewable energy to convert CO2 into value-added chemicals and fuels. However, the performance of CO2RR can hardly meet expectations because of the diverse intermediates and complicated reaction processes, necessitating the exploitation of highly efficient catalysts. In recent years, with advanced characterization technologies and theoretical simulations, the exploration of catalytic mechanisms has gradually deepened into the electronic structure of catalysts and their interactions with intermediates, which serve as a bridge to facilitate the deeper comprehension of structure-performance relationships. Transition metal-based catalysts (TMCs), extensively applied in electrochemical CO2RR, demonstrate substantial potential for further electronic structure modulation, given their abundance of d electrons. Herein, we discuss the representative feasible strategies to modulate the electronic structure of catalysts, including doping, vacancy, alloying, heterostructure, strain, and phase engineering. These approaches profoundly alter the inherent properties of TMCs and their interaction with intermediates, thereby greatly affecting the reaction rate and pathway of CO2RR. It is believed that the rational electronic structure design and modulation can fundamentally provide viable directions and strategies for the development of advanced catalysts toward efficient electrochemical conversion of CO2 and many other small molecules.

Dynamics of bulk and surface oxide evolution in copper foams for electrochemical CO2 reduction

Oxide-derived copper (OD-Cu) materials exhibit extraordinary catalytic activities in the electrochemical carbon dioxide reduction reaction (CO2RR), which likely relates to non-metallic material constituents formed in transitions between the oxidized and the reduced material. In time-resolved operando experiment, we track the structural dynamics of copper oxide reduction and its re-formation separately in the bulk of the catalyst material and at its surface using X-ray absorption spectroscopy and surface-enhanced Raman spectroscopy. Surface-species transformations progress within seconds whereas the subsurface (bulk) processes unfold within minutes. Evidence is presented that electroreduction of OD-Cu foams results in kinetic trapping of subsurface (bulk) oxide species, especially for cycling between strongly oxidizing and reducing potentials. Specific reduction-oxidation protocols may optimize formation of bulk-oxide species and thereby catalytic properties. Together with the Raman-detected surface-adsorbed *OH and C-containing species, the oxide species could collectively facilitate *CO adsorption, resulting an enhanced selectivity towards valuable C2+ products during CO2RR.

Size‐Dependent Carbon Dioxide Reduction Activity of Copper Nanoparticle and Nanocluster Electrocatalysts

AbstractThe electrochemical carbon dioxide (CO2) reduction reaction (CRR, which can convert CO2 into useful compounds at room temperature and ambient pressure by using electricity derived from renewable energy source), has been attracting attention in recent years. This is because it can convert CO2 into useful compounds, which is pertinent to establishing a next‐generation recycling‐oriented energy society. However, further improvement of the electrocatalyst is required to improve its activity, selectivity, and durability. Among these, copper (Cu) can synthesize various hydrocarbons from CO2 and has been the most studied electrocatalyst for the CRR over many years. In particular, regarding ligand‐protected Cu particles for the CRR, the size, shape, and ligands of Cu particles prepared by chemical reduction can be precisely controlled. In this review, we summarize previous research on the size‐dependence of the CRR by using ligand‐protected Cu particles (nanoparticles and nanoclusters) prepared by liquid‐phase reduction, and discuss the current status of these studies for researchers on the electrochemical CRR.

N-doped Cu2O with the tunable Cu0 and Cu+ sites for selective CO2 electrochemical reduction to ethylene

The electrochemical carbon dioxide reduction reaction (CO2RR) to high value-added fuels or chemicals driven by the renewable energy is promising to alleviate global warming. However, the selective CO2 reduction to C2 products remains challenge. Cu-based catalyst with the specific Cu0 and Cu+ sites is important to generate C2 products. This work used nitrogen (N) to tune amounts of Cu0 and Cu+ sites in Cu2O catalysts and improve C2-product conversion. The controllable Cu0/Cu+ ratio of Cu2O catalyst from 0.16 to 15.19 was achieved by adjusting the N doping amount using NH3/Ar plasma treatment. The major theme of this work was clarifying a volcano curve of the ethylene Faraday efficiency as a function of the Cu0/Cu+ ratio. The optimal Cu0/Cu+ ratio was determined as 0.43 for selective electroreduction CO2 to ethylene. X-ray spectroscopy and density functional theory (DFT) calculations were employed to elucidate that the strong interaction between N and Cu increased the binding energy of NCu bond and stabilize Cu+, resulting in a 92.3% reduction in the potential energy change for *CO-*CO dimerization. This study is inspiring in designing high performance electrocatalysts for CO2 conversion.

Integrating hydrogen utilization in CO2 electrolysis with reduced energy loss

Electrochemical carbon dioxide reduction reaction using sustainable energy is a promising approach of synthesizing chemicals and fuels, yet is highly energy intensive. The oxygen evolution reaction is particularly problematic, which is kinetically sluggish and causes anodic carbon loss. In this context, we couple CO2 electrolysis with hydrogen oxidation reaction in a single electrochemical cell. A Ni(OH)2/NiOOH mediator is used to fully suppress the anodic carbon loss and hydrogen oxidation catalyst poisoning by migrated reaction products. This cell is highly flexible in producing either gaseous (CO) or soluble (formate) products with high selectivity (up to 95.3%) and stability (>100 h) at voltages below 0.9 V (50 mA cm−2). Importantly, thanks to the “transferred” oxygen evolution reaction to a water electrolyzer with thermodynamically and kinetically favored reaction conditions, the total polarization loss and energy consumption of our H2-integrated CO2 reduction reaction, including those for hydrogen generation, are reduced up to 22% and 42%, respectively. This work demonstrates the opportunity of combining CO2 electrolysis with the hydrogen economy, paving the way to the possible integration of various emerging energy conversion and storage approaches for improved energy/cost effectiveness.

Cation-Induced Interfacial Hydrophobic Microenvironment Promotes the C-C Coupling in Electrochemical CO2 Reduction.

The electrochemical carbon dioxide reduction reaction (CO2RR) toward C2 products is a promising way for the clean energy economy. Modulating the structure of the electric double layer (EDL), especially the interfacial water and cation type, is a useful strategy to promote C-C coupling, but atomic understanding lags far behind the experimental observations. Herein, we investigate the combined effect of interfacial water and alkali metal cations on the C-C coupling at the Cu(100) electrode/electrolyte interface using ab initio molecular dynamics (AIMD) simulations with a constrained MD and slow-growth approach. We observe a linear correlation between the water-adsorbate stabilization effect, which manifests as hydrogen bonds, and the corresponding alleviation in the C-C coupling free energy. The role of a larger cation, compared to a smaller cation (e.g., K+ vs Li+), lies in its ability to approach the interface through desolvation and coordinates with the *CO+*CO moiety, partially substituting the hydrogen-bonding stabilizing effect of interfacial water. Although this only results in a marginal reduction of the energy barrier for C-C coupling, it creates a local hydrophobic environment with a scarcity of hydrogen bonds owing to its great ionic radius, impeding the hydrogen of surrounding interfacial water to approach the oxygen of the adsorbed *CO. This skillfully circumvents the further hydrogenation of *CO toward the C1 pathway, serving as the predominant factor through which a larger cation facilitates C-C coupling. This study unveils a comprehensive atomic mechanism of the cation-water-adsorbate interactions that can facilitate the further optimization of the electrolyte and EDL for efficient C-C coupling in CO2RR.

Engineering stable Cu+-Cu0 sites and oxygen defects in boron-doped copper oxide for electrocatalytic reduction of CO2 to C2+ products

Cu-based catalysts inevitably undergo surface reconstruction during the electrochemical carbon dioxide reduction reaction (CO2RR) process. Thus, it is a challenge to construct stable Cu+-Cu0 sites of Cu-based catalysts. In this study, we report a simple and facile engineering strategy for stable Cu+-Cu0 sites and oxygen defects derived from the boron-doped copper composite catalyst (B-CuxO) as an efficient CO2RR electrocatalyst. The 5 % B-CuxO exhibited 48.44 % C2+ products Faraday efficiency (FE) for 12 h at −1.0 V vs reversible hydrogen electrode (RHE) in H-cell, which was far superior to CuxO (23.85 %). Combining density functional theory (DFT) and in situ Attenuated Total Reflection Fourier Transform Infrared spectroscopy (in situ ATR-FTIR), a higher electronic depletion on the catalyst surface inhibited the electrons accumulation around Cu sites, thereby maintaining the positive charge and inhibiting the complete reduction of Cu+. Moreover, the high oxygen defects in 5 % B-CuxO could effectively activate CO2 into *CO. We emphasized that Cu+ functioned as the primary active site by facilitating adsorption and dimerization of *CO, whereas Cu0 assisted in optimizing CO2 activation.

Steering CO2 Electroreduction to C2+ Products via Enhancing Localized *CO Coverage and Local Pressure in Conical Cavity.

The electrochemical carbon dioxide (CO2) reduction reaction (CO2RR) involves a multistep proton-coupled electron transfer (PCET) process that generates a variety of intermediates, making it challenging to transform them into target products with high activity and selectivity. Here, a catalyst featuring a nanosheet-stacked sphere structure with numerous open and deep conical cavities (OD-CCs) is reported. Under the guidance of the finite-element method (FEM) simulations and theoretical analysis, it is shown that exerting control over the confinement space results in diffusion limitation of the carbon intermediates, thereby increasing local pressure and subsequently enhancing localized *CO coverage for dimerization. The nanocavities exhibit a structure-driven shift in selectivity of multicarbon (C2+) product from 41.8% to 81.7% during the CO2RR process.

A Sulfur-Doped Copper Catalyst with Efficient Electrocatalytic Formate Generation during the Electrochemical Carbon Dioxide Reduction Reaction.

Catalysts involving post-transition metals have shown almost invincible performance on generating formate in electrochemical CO2 reduction reaction (CO2 RR). Conversely, Cu without post-transition metals has struggled to achieve comparable activity. In this study, a sulfur (S)-doped-copper (Cu)-based catalyst is developed, exhibiting excellent performance in formate generation with a maximum Faradaic efficiency of 92 % and a partial current density of 321 mA cm-2 . Ex situ structural elucidations reveal the presence of abundant grain boundaries and high retention of S-S bonds from the covellite phase during CO2 RR. Furthermore, thermodynamic calculations demonstrate that S-S bonds can moderate the binding energies with various intermediates, further improving the activity of the formate pathway. This work is significant in modifying a low-cost catalyst (Cu) with a non-metallic element (S) to achieve comparable performance to mainstream catalysts for formate generation in industrial grade.

A Sulfur‐Doped Copper Catalyst with Efficient Electrocatalytic Formate Generation during the Electrochemical Carbon Dioxide Reduction Reaction

AbstractCatalysts involving post‐transition metals have shown almost invincible performance on generating formate in electrochemical CO2 reduction reaction (CO2RR). Conversely, Cu without post‐transition metals has struggled to achieve comparable activity. In this study, a sulfur (S)‐doped‐copper (Cu)‐based catalyst is developed, exhibiting excellent performance in formate generation with a maximum Faradaic efficiency of 92 % and a partial current density of 321 mA cm−2. Ex situ structural elucidations reveal the presence of abundant grain boundaries and high retention of S−S bonds from the covellite phase during CO2RR. Furthermore, thermodynamic calculations demonstrate that S−S bonds can moderate the binding energies with various intermediates, further improving the activity of the formate pathway. This work is significant in modifying a low‐cost catalyst (Cu) with a non‐metallic element (S) to achieve comparable performance to mainstream catalysts for formate generation in industrial grade.

Catalysts and electrolyzers for the electrochemical CO2 reduction reaction: from laboratory to industrial applications.

To cope with the urgent environmental pressure and tight energy demand, using electrocatalytic methods to drive the reduction of carbon dioxide molecules and produce a variety of fuels and chemicals, is one of the effective pathways to achieve carbon neutrality. In recent years, many significant advances in the study of the electrochemical carbon dioxide reduction reaction (CO2RR) have been made, but most of the works exhibit low current density, small electrode area and poor long-term stability, which are not suitable for large-scale industrial applications. Herein, combining the research achievements obtained in laboratories and the practical demand of industrial production, we summarize recent frontier progress in the field of the electrochemical CO2RR, including the fundamentals of catalytic reactions, catalyst design and preparation, and the construction of electrolyzers. In addition, we discuss the bottleneck problem of industrial CO2 electrolysis, and further present the prospect of the essential issues to be solved by the available technology for industrial electrolysis. This review can provide some basic understanding and knowledge accumulation for the development and practical application of electrochemical CO2RR technology.

Influence factors of CO adsorption on C2N-supported dual-atom catalysts unveiled by machine learning and twofold feature engineering.

Dual-atom catalysts (DACs) have emerged as a compelling frontier in the realm of the electrochemical carbon dioxide reduction reaction (CO2RR). However, elucidating the intrinsic properties of dual-atom pairs and their direct correlation with catalytic activity poses significant challenges. Herein, we investigate CO adsorption on 248 kinds of C2N-supported DACs and analyze the underlying structure-activity relationships of dual transition metal (TM) atoms based on density functional theory (DFT) calculations and machine learning (ML) models. Compared to the direct input of atomic features in the decision tree model of ML, we confirm that extra feature engineering with the introduction of the arithmetic combination of atomic features can better reflect the correlation of dual TM atoms on C2N-based DACs. Further feature importance analysis reveals a strong relationship between the last one occupied orbital radius (rv), group number (G) for dual TM atoms and the CO binding strength, as well as a potential connection with the d band centre (εd). Our work provides deeper insights into the design of DACs and highlights the significance of twofold feature engineering for the synergistic effects between dual TM atoms.

Acidic CO2 electroreduction for high CO2 utilization: catalysts, electrodes, and electrolyzers.

The electrochemical carbon dioxide (CO2) reduction reaction (CO2RR) is considered a promising technology for converting atmospheric CO2 into value-added compounds by utilizing renewable energy. The CO2RR has developed in various ways over the past few decades, including product selectivity, current density, and catalytic stability. However, its commercialization is still unsuitable in terms of economic feasibility. One of the major challenges in its commercialization is the low single-pass conversion efficiency (SPCE) of CO2, which is primarily caused by the formation of carbonate (CO32-) in neutral and alkaline electrolytes. Notably, the majority of CO2RRs take place in such media, necessitating significant energy input for CO2 regeneration. Therefore, performing the CO2RR under conditions that minimize CO32- formation to suppress reactant and electrolyte ion loss is regarded an optimal strategy for practical applications. Here, we introduce the recent progress and perspectives in the electrochemical CO2RR in acidic electrolytes, which receives great attention because of the inhibition of CO32- formation. This includes the categories of nanoscale catalytic design, microscale microenvironmental effects, and bulk scale applications in electrolyzers for zero carbon loss reactions. Additionally, we offer insights into the issue of limited catalytic durability, a notable drawback under acidic conditions and propose guidelines for further development of the acidic CO2RR.