Electrocatalytic CO2 Research Articles

Confined CuⅠ sites in partially electro-reduced 2D conductive Cu-MOF film for boosting CO2 electrocatalysis to C2 products

Cu-based catalysts, especially co-sites of Cu0 and CuⅠ, are the best competitors for electrochemical CO2 fixation to produce multi-carbon (C2 + ) products. However, it is challenging to construct highly stable CuⅠ sites due to the changeability of its valence state and electronic structure in the electroreduction process, and the mechanism is also elusive. Herein, a 2D conductive CuⅡ-MOF film (CuⅡHHTP@Cu0) is prepared on Cu (100) foil by in-situ electrochemical assembly. After pre-reduction, the in-situ produced Cu2O clusters are confined in the cavities of the film created by the local breaking of the MOF framework to construct a unique CuⅠ-CuⅡHHTP@Cu0 catalyst, so that a novel strategy is proposed to stablize highly dispersed CuⅠ sites during electrochemical reduction, thus protecting the Cu2O clusters from further reduction and ensuring the coexistence of CuⅠ (111)-Cu0 (100) sites. As such, the current density of CO2 electrochemical reduction catalyzed by this catalyst exceeds 300 mA cm−2, the duration overs 50 h, and the C2 selectivity achieves 72.6 %. In-situ spectroscopy and theoretical calculations reveal that the optimized microenvironment of the CuⅠ (111) sites reduces the energy barrier of *OCCOH coupling, and Cu0 (100) sites increase the coverage of *CO, thus boosting the production of C2 products.

PH‐Universal Electrocatalytic CO2 Reduction with Ampere‐Level Current Density on Doping‐Engineered Bismuth Sulfide

AbstractThe practical application of the electrocatalytic CO2 reduction reaction (CO2RR) to form formic acid fuel is hindered by the limited activation of CO2 molecules and the lack of universal feasibility across different pH levels. Herein, we report a doping‐engineered bismuth sulfide pre‐catalyst (BiS‐1) that S is partially retained after electrochemical reconstruction into metallic Bi for CO2RR to formate/formic acid with ultrahigh performance across a wide pH range. The best BiS‐1 maintains a Faraday efficiency (FE) of ~95 % at 2000 mA cm−2 in a flow cell under neutral and alkaline solutions. Furthermore, the BiS‐1 catalyst shows unprecedentedly high FE (~95 %) with current densities from 100 to 1300 mA cm−2 under acidic solutions. Notably, the current density can reach 700 mA cm−2 while maintaining a FE of above 90 % in a membrane electrode assembly electrolyzer and operate stably for 150 h at 200 mA cm−2. In situ spectra and density functional theory calculations reveals that the S doping modulates the electronic structure of Bi and effectively promotes the formation of the HCOO* intermediate for formate/formic acid generation. This work develops the efficient and stable electrocatalysts for sustainable formate/formic acid production.

Anion Modulation of Ag‐Imidazole Cuboctahedral Cage Microenvironments for Efficient Electrocatalytic CO2 Reduction

AbstractHow to achieve CO2 electroreduction in high efficiency is a current challenge with the mechanism not well understood yet. The metal‐organic cages with multiple metal sites, tunable active centers, and well‐defined microenvironments may provide a promising catalyst model. Here, we report self‐assembly of Ag4L4 type cuboctahedral cages from coordination dynamic Ag+ ion and triangular imidazolyl ligand 1,3,5‐tris(1‐benzylbenzimidazol‐2‐yl) benzene (Ag‐MOC‐X, X=NO3, ClO4, BF4) via anion template effect. Notably, Ag‐MOC‐NO3 achieves the highest CO faradaic efficiency in pH‐universal electrolytes of 86.1 % (acidic), 94.1 % (neutral) and 95.3 % (alkaline), much higher than those of Ag‐MOC‐ClO4 and Ag‐MOC‐BF4 with just different counter anions. In situ attenuated total reflection Fourier transform infrared spectroscopy observes formation of vital intermediate *COOH for CO2‐to‐CO conversion. The density functional theory calculations suggest that the adsorption of CO2 on unsaturated Ag‐site is stabilized by C−H⋅⋅⋅O hydrogen‐bonding of CO2 in a microenvironment surrounded by three benzimidazole rings, and the activation of CO2 is dependent on the coordination dynamics of Ag‐centers modulated by the hosted anions through Ag⋅⋅⋅X interactions. This work offers a supramolecular electrocatalytic strategy based on Ag‐coordination geometry and host–guest interaction regulation of MOCs as high‐efficient electrocatalysts for CO2 reduction to CO which is a key intermediate in chemical industry process.

Electrocatalytic Reduction of Carbon Dioxide in Acidic Electrolyte with Superior Performance of a Metal-Covalent Organic Framework over Metal-Organic Framework.

CO2 electroreduction (CO2RR) to generate valuable chemicals in acidic electrolytes can improve the carbon utilization rate in comparison to that under alkaline conditions. However, the thermodynamically more favorable hydrogen evolution reaction under an acidic electrolyte makes the CO2RR a big challenge. Herein, robust metal phthalocyanine(Pc)-based (M = Ni, Co) conductive metal-covalent organic frameworks (MCOFs) connected by strong metal tetraaza[14]annulene (TAA) linkage, named NiPc-NiTAA and NiPc-CoTAA, are designed and synthesized to apply in the CO2RR in acidic electrolytes for the first time. The optimal NiPc-NiTAA exhibited an excellent Faradaic efficiency (FECO) of 95.1% and a CO partial current density of 143.0 mA cm-2 at -1.5 V versus the reversible hydrogen electrode in an acidic electrolyte, which is 3.1 times that of the corresponding metal-organic framework NiPc-NiN4. The comparison tests and theoretical calculations reveal that in-plane full π-d conjugation MCOF with a good conductivity of 3.01 × 10-4 S m-1 accelerates migration of the electrons. The NiTAA linkage can tune the electron distribution in the d orbit of metal centers, making the d-band center close to the Fermi level and then activating CO2. Thus, the active sites of NiPc and NiTAA collaborate to reduce the *COOH formation energy barrier, favoring CO production in an acid electrolyte. It is a helpful route for designing outstanding conductive MCOF materials to enhance CO2 electrocatalysis under an acidic electrolyte.

Exploring the CO2 Electrocatalysis Potential of 2D Metal-Organic Transition Metal-Hexahydroxytriquinoline Frameworks: A DFT Investigation.

Metal-organic frameworks have demonstrated great capacity in catalytic CO2 reduction due to their versatile pore structures, diverse active sites, and functionalization capabilities. In this study, a novel electrocatalytic framework for CO2 reduction was designed and implemented using 2D coordination network-type transition metal-hexahydroxytricyclic quinazoline (TM-HHTQ) materials. Density functional theory calculations were carried out to examine the binding energies between the HHTQ substrate and 10 single TM atoms, ranging from Sc to Zn, which revealed a stable distribution of metal atoms on the HHTQ substrate. The majority of the catalysts exhibited high selectivity for CO2 reduction, except for the Mn-HHTQ catalysts, which only exhibited selectivity at pH values above 4.183. Specifically, Ti and Cr primarily produced HCOOH, with corresponding 0.606 V and 0.236 V overpotentials. Vanadium produced CH4 as the main product with an overpotential of 0.675 V, while Fe formed HCHO with an overpotential of 0.342 V. Therefore, V, Cr, Fe, and Ti exhibit promising potential as electrocatalysts for carbon dioxide reduction due to their favorable product selectivity and low overpotential. Cu mainly produces CH3OH as the primary product, with an overpotential of 0.96 V. Zn primarily produces CO with a relatively high overpotential of 1.046 V. In contrast, catalysts such as Sc, Mn, Ni, and Co, among others, produce multiple products simultaneously at the same rate-limiting step and potential threshold.

Combination of Co Single Atom and MoS2 Antisite Defect for Efficient Electrocatalytic CO2 Methanation: A Rational Design at Electronic Scale

AbstractMethane, the simplest hydrocarbon, has a high energy density and is widely used as chemical feedstocks or fuels. Converting CO2 to methane through electrochemical reduction offers a promising strategy for managing the global carbon balance, but is a challenge due to the lack of effective electrocatalysts. Herein, the Co single atom catalyst supported by MoS2 antisite defect (Co‐MoS2) is designed from both the activity and selectivity aspects. By virtue of i) moderately electron‐deficient state (Coδ+) ensuring efficient CO2 activation and HER suppression; ii) the strong adsorption capability for intermediate enhancing selectivity; iii) the single atomic active site avoiding the formation of C2 products, Co‐MoS2 could selectively convert CO2 to CH4 with a limiting potential of −0.45 V vs. RHE, which outperforms most of the present catalysts, and is expected to be a promising substitution for Cu‐based catalysts.

Electrocatalytic CO2 Reduction to Alcohols: Progress and Perspectives

Utilizing renewable electricity for the electrocatalytic conversion of CO2 into alcohols represents a promising avenue for generating value‐added fuels and achieving carbon neutrality. Recently, there has been growing scientific interest in achieving high‐efficiency conversion of CO2 to alcohols, with significant advancements made in mechanism understanding, reactor design, catalyst development, and more. Herein, a thorough examination of the latest advances in electrocatalytic CO2 reduction reaction (CO2RR) to alcohols is provided. General mechanisms and pathways of electrocatalytic conversion of CO2‐to‐alcohols are systematically illustrated. Subsequently, electrolyzer configurations, electrolytes, and electrocatalysts employed in CO2RR are summarized. After that, critical operating parameters (e.g., reaction pressure, temperature, and pH) that would significantly influence the CO2RR process are also analyzed. Finally, the review addresses challenges and offers perspectives in this field to guide future studies aimed at advancing CO2‐to‐alcohols conversion technologies.

Upcycling CO2 into succinic acid via electrochemical and engineered Escherichia coli

Converting CO2 into value-added chemicals still remains a grand challenge. Succinic acid has long been considered as one of the top building block chemicals. This study reported efficiently upcycling CO2 into succinic acid by combining between electrochemical and engineered Escherichia coli. In this process, the Cu-organic framework catalyst was synthesized for electrocatalytic CO2-to-ethanol conversion with high Faradaic efficiency (FE, 84.7 %) and relative purity (RP, 95 wt%). Subsequently, an engineered E. coli with efficiently assimilating CO2-derived ethanol to produce succinic acid was constructed by combining computational design and metabolic engineering, and the succinic acid titer reached 53.8 mM with the yield of 0.41 mol/mol, which is 82 % of the theoretical yield. This study effort to link the two processes of efficient ethanol synthesis by electrocatalytic CO2 and succinic acid production from CO2-derived ethanol, paving a way for the production of succinic acid and other value-added chemicals by converting CO2 into ethanol.

Promoting CO Electroreduction to C2+ Oxygenates by Distribution of Water Dissociation Sites.

The electrocatalytic CO2 or CO reduction reaction is a complex proton-coupled electron transfer reaction, in which protons in the electrolyte have a critical effect on the surface adsorbed *H species and the multi-carbon oxygenate products such as ethanol. However, the coupling of *H and carbon-containing intermediates into C2+ oxygenates can be severely hampered by the inappropriate distributions of those species in the catalytic interfaces. In this work, the controlled distribution of highly dispersed CeOx nanoclusters is demonstrated on Cu nanosheets as an efficient CO electroreduction catalyst, with Faradaic efficiencies of ethanol and total oxygenates of 35% and 58%, respectively. The CeOx nanoclusters (2-5 nm) enabled efficient water dissociation and appropriate distribution of adsorbed *H species on the Cu surface with carbon-containing species, thus facilitating the generation of C2+ oxygenate products. In contrast, pristine Cu without CeOx tended to form ethylene, while the aggregated CeOx nanoparticles promoted the surface density of *H and subsequent H2 evolution.

Tuning the Microenvironment of Co−N4 Ensemble for Co Single‐Atom Catalysts for Electrocatalytic CO2 Reduction

AbstractSingle‐atom catalysts (SACs), with their well‐defined structure, serve as an efficient catalyst model for studying the structure‐performance relation in the electrocatalytic CO2 reduction reaction (CO2RR). Current CO2RR research primarily focus on the coordination interactions between metal single atoms and coordinated ligands, while the impact of the metal SAC′s microenvironment remains largely unexplored. Herein, we generate three microenvironments for a CoN4 ensemble by using different nitrogen sources to prepare Co SACs, i. e. pyridine‐type Co−N4 (Co−N4 SACPhen), the pyrrole‐type Co−N4 (Co−N4 SACDp) and the mixed‐type Co−N4(Co−N4 SACMm). It reveals that the Co−N4 SACPhen contributes to CO generation with 99.5 % selectivity at −0.76 vs RHE, whereas the Co−N4 SACDp accelerates a severe hydrogen evolution reaction. Experimental studies confirmed that the Co−N4 SACPhen possesses distinctive electrochemical properties and electronic structure, with the pyridine‐N being more conducive to electron accumulation and exhibited a higher electron delocalization, thereby promoting the generation of CO. This study deepens our understanding of the cobalt SAC′s microenvironment‘s influence on CO2RR.

Reaction Environment Regulation for Electrocatalytic CO2 Reduction in Acids

AbstractThe electrocatalytic CO2 reduction reaction (CO2RR) is a sustainable route for converting CO2 into value‐added fuels and feedstocks, advancing a carbon‐neutral economy. The electrolyte critically influences CO2 utilization, reaction rate and product selectivity. While typically conducted in neutral/alkaline aqueous electrolytes, the CO2RR faces challenges due to (bi)carbonate formation and its crossover to the anolyte, reducing efficiency and stability. Acidic media offer promise by suppressing these processes, but the low Faradaic efficiency, especially for multicarbon (C2+) products, and poor electrocatalyst stability persist. The effective regulation of the reaction environment at the cathode is essential to favor the CO2RR over the competitive hydrogen evolution reaction (HER) and improve long‐term stability. This review examines progress in the acidic CO2RR, focusing on reaction environment regulation strategies such as electrocatalyst design, electrode modification and electrolyte engineering to promote the CO2RR. Insights into the reaction mechanisms via in situ/operando techniques and theoretical calculations are discussed, along with critical challenges and future directions in acidic CO2RR technology, offering guidance for developing practical systems for the carbon‐neutral community.

A review of catalytic reduction of carbon dioxide

Carbon dioxide (CO2) generated from the consumption of fossil fuels is one of the main factors contributing to the greenhouse effect. How to mitigate the greenhouse effect and reduce the extraction and consumption of fossil fuels has become an issue worthy of study. In recent years, a technology for the catalytic reduction of CO2 to fossil fuels and chemicals has attracted a great deal of attention by providing a new way to solve this problem. This paper reviews the basic principles of three fundamental catalytic CO2 reduction, photocatalysis, electrocatalysis and thermocatalysis, and two advanced catalytic modes, thermocatalysis and photoelectrocatalysis, derived from these three modes, as well as their advantages and disadvantages. In addition, the challenges that the catalytic reduction of CO2 is currently facing are also discussed. Although this technology has made significant progress over the decades, it is still in its preliminary stage with some shortcomings and there is a long way to go before it can be applied in reality.

Advances in electrocatalytic carbon dioxide reduction reactors, electrolytes and catalysts

With the advance of The Times, people's demand for fossil energy has greatly increased, and it is the main energy for people to develop economy and science and technology. However, the large-scale exploitation of fossil energy has led to environmental pollution and energy crisis, and the concentration of CO2 in the air continues to rise, and the greenhouse effect is becoming more and more serious. Therefore, the conversion of CO2 into the high value-added fuels and chemicals we need will be a major measure to solve environmental problems. So, converting CO2 into fuels or high value-added chemicals using CO2 electrocatalytic reduction (CO2RR) technology is an effective way to alleviate the current problems of energy and environment. In this paper, we summarize the research progress in reaction systems, electrolyte effects, and catalyst development in CO2RR experiments, focusing on the electrocatalytic aspects of CO2. Finally, we provide an outlook on the CO2 electrocatalysis industry.

CO Intermediate‐Assisted Dynamic Cu Sintering During Electrocatalytic CO2 Reduction on Cu−N−C Catalysts

AbstractThe electrochemical CO2 reduction reaction (eCO2RR) to multicarbon products has been widely recognized for Cu‐based catalysts. However, the structural changes in Cu‐based catalysts during the eCO2RR pose challenges to achieving an in‐depth understanding of the structure–activity relationship, thereby limiting catalyst development. Herein, we employ constant‐potential density functional theory calculations to investigate the sintering process of Cu single atoms of Cu−N−C single‐atom catalysts into clusters under eCO2RR conditions. Systematic constant‐potential ab initio molecular dynamics simulations revealed that the leaching of Cu−(CO)x moieties and subsequent agglomeration into clusters can be facilitated by synergistic adsorption of H and eCO2RR intermediates (e.g., CO). Increasing the Cu2+ concentration or the applied potential can efficiently suppress Cu sintering. Both microkinetic simulations and experimental results further confirm that sintered Cu clusters play a crucial role in generating C2 products. These findings provide significant insights into the dynamic evolution of Cu‐based catalysts and the origin of their activity toward C2 products during the eCO2RR.

Recent Progress on Copper-Based Bimetallic Heterojunction Catalysts for CO2 Electrocatalysis: Unlocking the Mystery of Product Selectivity.

Copper-based bimetallic heterojunction catalysts facilitate the deep electrochemical reduction of CO2 (eCO2RR) to produce high-value-added organic compounds, which hold significant promise. Understanding the influence of copper interactions with other metals on the adsorption strength of various intermediates is crucial as it directly impacts the reaction selectivity. In this review, an overview of the formation mechanism of various catalytic products in eCO2RR is provided and highlight the uniqueness of copper-based catalysts. By considering the different metals' adsorption tendencies toward various reaction intermediates, metals are classified, including copper, into four categories. The significance and advantages of constructing bimetallic heterojunction catalysts are then discussed and delve into the research findings and current development status of different types of copper-based bimetallic heterojunction catalysts. Finally, insights are offered into the design strategies for future high-performance electrocatalysts, aiming to contribute to the development of eCO2RR to multi-carbon fuels with high selectivity.

Hydrogen‐Bonded Organic Framework Supporting Atomic Bi−N2O2 Sites for High‐Efficiency Electrocatalytic CO2 Reduction

AbstractSingle atomic catalysts (SACs) offer a superior platform for studying the structure–activity relationships during electrocatalytic CO2 reduction reaction (CO2RR). Yet challenges still exist to obtain well‐defined and novel site configuration owing to the uncertainty of functional framework‐derived SACs through calcination. Herein, a novel Bi−N2O2 site supported on the (1 1 0) plane of hydrogen‐bonded organic framework (HOF) is reported directly for CO2RR. In flow cell, the target catalyst Bi1‐HOF maintains a faradaic efficiency (FE) HCOOH of over 90 % at a wide potential window of 1.4 V. The corresponding partial current density ranges from 113.3 to 747.0 mA cm−2. And, Bi1‐HOF exhibits a long‐term stability of over 30 h under a successive potential‐step test with a current density of 100–400 mA cm−2. Density function theory (DFT) calculations illustrate that the novel Bi−N2O2 site supported on the (1 1 0) plane of HOF effectively induces the oriented electron transfer from Bi center to CO2 molecule, reaching an enhanced CO2 activation and reduction. Besides, this study offers a versatile method to reach series of M−N2O2 sites with regulable metal centers via the same intercalation mechanism, broadening the platform for studying the structure–activity relationships during CO2RR.

Activating the Ni‐Contenting Carbon Nanotube by Covalent Triazine Frameworks to Form Atomically Dispersed Ni Sites with Curvature Effect for Electrocatalytic CO2 Reduction

N‐coordinated Ni sites (NiNx) are effective catalysts for the electrochemical reduction of CO2 to CO. In most researches, modulating the coordination environment of Ni atoms is focused on to improve electrochemical CO2 reduction (ECR) performance. However, the influence of the carbon substrate's structure on the intrinsic activity of NiNx is seldom investigated. The highly curved surface of carbon nanotubes (CNT) may provide a unique curvature effect on NiNx. It is found that the Ni residues in CNT can be atomized to form NiNx sites on the surface of CNT (Ni‐N/CNT@covalent triazine framework [CTF]) through high‐temperature pyrolysis, using a soluble CTF nanosheet as N precursor. The π‐conjugated and ultrathin 2D structure of CTF enables closer interfacial contact between CTF and CNT, which avoids the formation of a thick carbon layer to maximize the curvature effect. Theoretical data reveal that the NiN3 configuration may act as a highly active ECR site, and the curvature effect from CNT can further tune the electronic structure of NiN3, thus improving the ECR kinetics. The Ni‐N/CNT@CTF‐based flow‐cell electrolyzer exhibits a jCO of 201 mA cm−2 at −0.9 V with a high FECO of 98%.

Electrocatalytic CO2 Reduction with Atomically Precise Au13 Nanoclusters: Effect of Ligand Shell on Catalytic Performance

Electrocatalytic CO₂ Reduction with Atomically Precise Au₁₃ Nanoclusters: Effect of Ligand Shell on Catalytic Performance

Dual Sites on Graphitic Biochar for Electrocatalytic CO2 Reduction to Ethanol Conversion

Dual Sites on Graphitic Biochar for Electrocatalytic CO₂ Reduction to Ethanol Conversion

Cobalt Doping in MOF-Derived Carbon-Loaded Tin Nanomaterials for Enhanced Electrocatalytic CO2 Reduction

Cobalt Doping in MOF-Derived Carbon-Loaded Tin Nanomaterials for Enhanced Electrocatalytic CO₂ Reduction