Electrochemical Carbon Dioxide Research Articles

La-based Transition Metal Oxide Perovskites as Electrocatalysts for Electrochemical Carbon Dioxide Reduction

We report here the feasibility of using LaTMO3-based perovskites (TM = Co, Cr, Fe, Mn, Ni, i.e., non-Cu 3d transition metals) as electrocatalysts for electrochemical CO2 reduction reaction (eCO2RR). Phase pure LaTMO3 perovskites, having TM-ions in multiple oxidation states for all and O-defects for LaFeO3 and LaNiO3, have been synthesized and tested as electrocatalysts for eCO2RR in flow cell type set-up. The above characteristics of the La-TM-oxides have been found to influence the current densities during eCO2RR at the various applied potentials, with favorable effects of the presence of O-defects (as for LaFeO3 and LaNiO3). Upon eCO2RR, both C1 and C2 liquid products have been obtained, including ethanol, with a partial current density of −2.66 mA cm−2 at −1.2 V vs RHE (for LaFeO3). The types of products and the faradic efficiencies have been found to depend on the TM-ion present (in the LaTMO3); in particular, the oxidation state(s), associated O-defect(s) and electronic conductivity. Furthermore, the electrocatalysts have been found to be stable during eCO2RR. Overall, the present work highlights the potential of La-TM-oxide perovskites for usage as stable electrocatalysts for eCO2RR, and also provides insights into the proper selection of “TM” and reaction conditions for obtaining the desired product(s).

Facile Preparation of Stable NiII‐ and CoII‐tetraaminophthalocyanine Electropolymers for Highly Efficient Heterogeneous Carbon Dioxide Reduction

This study focused on preparation of stable polymer films of NiII‐ and CoII‐tetraaminophthalocyanines, p‐NiTAPc and p‐CoTAPc, respectively, for highly efficient heterogeneous electrochemical carbon dioxide (CO2) reduction in a flow electrolysis cell. Major development represented in this work was fabrication of p‐NiTAPc and p‐CoTAPc films via electropolymerization of their corresponding monomers on carbon‐based substrates without using binder or conducting additive materials to obtain efficient gas diffusion electrodes (GDEs) for scalable, productive and selective CO2‐to‐CO conversion. The target polymers were characterized by UV‐visible spectrophotometry, attenuated total reflection‐Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X‐ray spectroscopy and cyclic voltammetry. According to controlled potential electrolysis and gas chromatography, p‐NiTAPc‐catalyzed CO2 reduction at –0.99V vs. reversible hydrogen electrode (RHE) gave 953 mL of CO in a period of 16 hours with current density and Faradaic efficiency (FE) of 109±1 mA·cm‐2 and 99±2%, respectively. A p‐CoTAPc‐modified GDE exhibited superior catalytic performance to the case of p‐NiTAPc in terms of catalyst stability and CO productivity by performing the continuous CO2 reduction at the potential of –1.10 V vs. RHE for up to 41 hours and affording almost 3 times higher amount of CO with the current density of 161±5 mA/cm2 and 95±2% FE.

Continuous Production of Ethylene and Hydrogen Peroxide from Paired Electrochemical Carbon Dioxide Reduction and Water Oxidation (Adv. Energy Mater. 18/2024)

Continuous Production of Ethylene and Hydrogen Peroxide from Paired Electrochemical Carbon Dioxide Reduction and Water Oxidation (Adv. Energy Mater. 18/2024)

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.

Dynamic (Sub)surface-Oxygen Enables Highly Efficient Carbonyl-Coupling for Electrochemical Carbon Dioxide Reduction.

Nowadays, high-valent Cu species (i.e., Cuδ +) are clarified to enhance multi-carbon production in electrochemical CO2 reduction reaction (CO2RR). Nonetheless, the inconsistent average Cu valence states are reported to significantly govern the product profile of CO2RR, which may lead to misunderstanding of the enhanced mechanism for multi-carbon production and results in ambiguous roles of high-valent Cu species. Dynamic Cuδ + during CO2RR leads to erratic valence states and challenges of high-valent species determination. Herein, an alternative descriptor of (sub)surface oxygen, the (sub)surface-oxygenated degree (κ), is proposed to quantify the active high-valent Cu species on the (sub)surface, which regulates the multi-carbon production of CO2RR. The κ validates a strong correlation to the carbonyl (*CO) coupling efficiency and is the critical factor for the multi-carbon enhancement, in which an optimized Cu2O@Pd2.31 achieves the multi-carbon partial current density of ≈330 mA cm-2 with a faradaic efficiency of 83.5%. This work shows a promising way to unveil the role of high-valent species and further achieve carbon neutralization.

Co-sensitization of Copper Indium Gallium Disulfide and Indium Sulfide on Zinc Oxide Nanostructures: Effect of Morphology in Electrochemical Carbon Dioxide Reduction.

Recent advances in nanoparticle materials can facilitate the electro-reduction of carbon dioxide (CO2) to form valuable products with high selectivity. Copper (Cu)-based electrodes are promising candidates to drive efficient and selective CO2 reduction. However, the application of Cu-based chalcopyrite semiconductors in the electrocatalytic reduction of CO2 is still limited. This study demonstrated that novel zinc oxide (ZnO)/copper indium gallium sulfide (CIGS)/indium sulfide (InS) heterojunction electrodes could be used in effective CO2 reduction for formic acid production. It has been determined that Faradaic efficiencies for formic acid production using ZnO nanowire (NW) and nanoflower (NF) structures vary due to structural and morphological differences. A ZnO NW/CIGS/InS heterojunction electrode resulted in the highest efficiency of 77.2% and 0.35 mA cm-2 of current density at a -0.24 V (vs. reversible hydrogen electrode) bias potential. Adding a ZTO intermediate layer by the spray pyrolysis method decreased the yield of formic acid and increased the yield of H2. Our work offers a new heterojunction electrode for efficient formic acid production via cost-effective and scalable CO2 reduction.

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.

Ordered porous copper sulfide with hollow interior for superior electrochemical CO2 to formate conversion

Targeted for superior formate production from electrochemical carbon dioxide (CO2) reduction, hollow ordered porous copper sulfide cuboctahedra (HOP CuS-CO) with controlled shell thicknesses were designed and synthesized in this study. Uniform and interconnected pores are evenly distributed in the hollow shells of HOP CuS-CO. Capitalizing on the merits of porous cages, HOP CuS-CO exhibit outstanding formate production with a Faradaic efficiency up to 70.3 % and catalytic stability of 26 h under an applied potential of −1.1 V versus reversible hydrogen electrode (vs. RHE). In situ Raman spectroscopy results reveal that the adsorption of HCOO* intermediates is promoted on the catalyst surfaces of HOP CuS-CO due to a spatial confinement effect, which leads to highly efficient CO2 to formate conversion. The present study offers insights for designing materials toward superior formate production from electrochemical CO2 reduction.

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.

Ternary Zn-Ce-Ag catalysts for selective and stable electrochemical CO2 reduction at large-scale

Catalyst materials with high stability and selectivity, based on inexpensive materials, are vital for practical electrochemical carbon dioxide (CO2) reduction (ECR). In this study, we report ternary Zn-Ce-Ag catalysts for selective and stable CO2-to-CO conversion at high current densities on a large scale. We found that ZnO catalysts are relatively selective for CO2-to-CO conversion, but are only stable for less than 20 h at current densities over 100 mA cm−2 due to the reduction of the Zn oxide phase, along with the ECR. Combining ZnO with CeO2 significantly improves the stability of the catalysts, maintaining a CO Faradaic efficiency (FECO) of 80 % for 100 h at the current density of 200 mA cm−2. By introducing a small amount of silver (<10 wt%) to form ternary Ag-Ce-Zn catalysts, both CO selectivity and stability are significantly improved: the developed catalysts exhibit a high FECO of 90 % at 200 mA cm−2 and are stable for 200 h. We attribute the enhanced CO2-to-CO conversion efficiency to the abundance of stable interfacial areas of various metal-oxide interactions, which are critical for ECR. To demonstrate the potential for practical application, we performed the ECR in a large electrochemical cell, with an active surface area of 100 cm2. The system delivers a FECO of 90 % at 200 mA cm−2 for an extended operation time of 200 h.

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.

Recent Advances and Challenges in Electrocatalytic Carboxylation of CO2

AbstractThe electrochemical fixation of carbon dioxide onto organic matter has emerged as a promising approach in recent years. By combining the unique features of electrochemistry with the goal of carbon dioxide fixation, researchers aim to develop new strategies that can contribute to a more sustainable and environmentally friendly synthesis of organic compounds. One advantage of electrochemical methods is their ability to provide both electrons and energy for chemical transformations. This allows for the direct conversion of carbon dioxide into valuable organic products, without the need for transition metal catalysts or harsh reaction conditions. As a result, electrochemical carbon dioxide fixation offers the potential for milder and more efficient processes compared to traditional methods. Scientists have made noteworthy progress in exploring different strategies for the fixation of carbon dioxide under electrochemical conditions. These strategies involve the activation of various types of chemical bonds, including C(sp2)–C(sp2), C(sp2)–H, C–X (X = halogen), and C(sp3)–X (X = S, C, O, N). This review aims to provide an overview of the current state of research on electrochemical carbon dioxide fixation into organic matter. It will discuss the different strategies employed, the key findings, and the challenges that remain to be addressed. By highlighting the recent advancements in this field, this review hopes to inspire further exploration and innovation in the area of electrochemical synthesis for carbon dioxide fixation.1 Introduction2 Electrocatalytic Monocarboxylation of CO2 2.1 Monocarboxylation of C(sp2)–C(sp2)2.2 Monocarboxylation of C(sp2)–H2.3 Monocarboxylation of C–X (X = Cl, Br, I)2.4 Monocarboxylation of C(sp3)–X (X = S, C, O, N)3 Electrocatalytic Dicarboxylation of CO2 4 Electrocatalytic Esterification of CO2 5 Conclusions

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.

Continuous Production of Ethylene and Hydrogen Peroxide from Paired Electrochemical Carbon Dioxide Reduction and Water Oxidation

AbstractPaired electrolysis offers an auspicious strategy for the generation of high‐value chemicals, at both the anode and cathode, in an integrated electrochemical reactor. Through efficient electron utilization, routine product misuse at overlooked electrodes can be prevented. Here, an original paired electrosynthetic system is reported that can convert CO2 to ethylene (C2H4) at the cathode, and water to hydrogen peroxide (H2O2) at the anode under a single pass of electric charge. Amongst various investigated copper (Cu) nanomorphologies, the bespoke mixed Cu nanowire/nanoparticle catalyst recorded a peak C2H4 Faraday efficiency (FE) of 60% following 370 h of electrolysis at 200 mA cm−2, while the tailored boron‐doped diamond (BDD) anode accumulated an unprecedented ≈1% w/w of H2O2 in 4 m K2CO3 upon applying 300 mA cm−2 for 10 h. When paired, the dual C2H4‐H2O2 electrochemical cell attains a combined FE of 120% for 50 h at 200 mA cm−2, a combined energy efficiency (EE) of 69%, and a 50% decrease in the overall electrical energy consumption (EEC) compared to the individual electrosynthesis of C2H4 and H2O2.