CO2 Electroreduction Research Articles

Near-Electrode Concentration Gradients of Bicarbonate and pH within Porous Gas Diffusion Electrode for Optimized Selective CO2 Electroreduction to C2+ Products.

With high current density, the intense near-electrode CO2 reduction reaction (CO2RR) will cause the concentration gradients of bicarbonate (HCO3-) and hydroxyl (OH-) ions, which affect the selectivity of high-value C2+ products of the CO2RR. In this work, we simulated the near-electrode concentration gradients of electrolyte species with different porous Cu-based CLs (catalyst layers) of GDE (gas diffusion electrode) by COMSOL Multiphysics. The higher porosity CL exhibits a better buffer ability of local alkalinity while ensuring a sufficient supply of H+ and local CO2 concentration. Subsequently, the different porosity CLs were prepared by vacuum-thermal evaporation with different evaporation rate. Structural characterizations and liquid permeability tests confirm the role of the porous CL structure in optimizing concentration gradients. As a result, the high-porosity CL (Cu-HP) exhibits a higher C2+ Faraday efficiency (FE) of ∼79.61% at 500 mA cm-2 under 1 M KHCO3, far more than the FEC2+ ≈ 38.20% with the low-porosity sample (Cu-LP).

Nonbonding Metal-Metal Interaction in Metal-Nitrogen-Carbon Single-Atom Catalysts Boosts CO Electroreduction.

Metal-nitrogen-carbon single-atom catalysts (SACs) have recently emerged as selective electrocatalysts for the reduction of CO2 to CO, but their ability to further electroreduce CO is poor. Here, based on constant-potential density functional theory simulations, we predict that Co-N-M (M = Fe, Co) SACs with nonbonding metallic centers bridged by a common nitrogen atom can catalyze four-electron reduction of CO to methanol at an ultralow overpotential of 220-310 mV. We show that the metal atoms in the SACs are terminated by H species which prevent the formation of σ bonding between CO and the metal atoms. Thanks to the nonbonding electrostatic repulsion between Co and its adjacent M atom, the Co dxz band is broadened and shifted toward the Fermi level, leading to enhanced dxz - 2π* interaction that gives rise to stable CO adsorption and promotes its active and selective reduction. This work offers an alternative strategy to tackle the challenge of CO electroreduction on SACs and highlights the role of nonbonding metal-metal interactions in modulating adsorption properties of SACs.

Robust Bi Metal–Organic Framework-Derived Catalyst for the Selective Electroreduction of CO2 to Formate at Current Densities up to 1 A cm–2 in Gas Diffusion Electrodes

Robust Bi Metal–Organic Framework-Derived Catalyst for the Selective Electroreduction of CO₂ to Formate at Current Densities up to 1 A cm^–2 in Gas Diffusion Electrodes

Nanowire arrays with abundant Cu–Ni interfaces for electroreduction of CO2 to ethylene

Electrochemical reduction of CO2 to ethylene (C2H4), driven by renewable electricity, represents a strategy for sustainable development and carbon neutrality. However, continuous production of C2H4 at high efficiency and low cost remains a significant challenge. Herein, a synergistic approach using non-precious metals was employed, and in situ construction of a nanoarray structure with abundant Cu–Ni interfaces (Ni/Cu NWs) on a gas diffusion layer (GDL) was performed. The atomic interactions at the interface significantly enhanced the efficiency of C–C coupling. The Faraday efficiency (FE) for C2H4 production reached 58.65 %, and the current density of 253.42 mA cm−2 at −1.1 V, markedly surpassing that of bare Cu nanowire (Cu NWs, 25.33 %). By virtue of the in-situ construction on the GDL, the Cu–Ni interface catalyst demonstrated excellent stability, operating under high current for more than 72 h. In situ infrared characterization and theoretical calculations demonstrate that the incorporation of Ni effectively enhanced the CO2 activation process, which is beneficial for the accumulation of key intermediate of C–C coupling. At the Cu–Ni interface, the energy barrier for C–C coupling was reduced, thereby effectively promoting the conversion of C2H4. This work presents a solution strategy for the interfacial engineering of non-precious metal catalysts.

Bismuth oxide nanoflakes grown on defective microporous carbon endows high-efficient CO2 reduction at ampere level

Carbon dioxide electroreduction is a green technology for artificial carbon sequestration, which is being delayed from industrialization due to the lack of efficient catalysts at high current conditions. Herein, the Bi2O3 nanoflakes were uniformly grown on a defective porous carbon (PC). This self-assembling Bi2O3/PC catalyst was applied to drive CO2 electroreduction at 1.0 A, 1.5 A and 2.0 A while the Faradaic efficiency of formate reaches 91.50 %, 86.30 % and 84.22 %, respectively. Density functional theory calculations revealed the intrinsic defect of carbon is able to give electron to Bi through O bridge, which increased the electron aggregation of Bi and lowered the generation energy barrier of *OCHO intermediate. Additionally, the unique 3D network of staggered Bi2O3 enhances the CO2 adsorption and favors the electron transportation. By integrating all above advantages into a solid electrolyte-type cell, we are able to produce pure formic acid in a rate of 15.48 mmol h−1 at ampere current.

CO2 Electrolysis Technologies: Bridging the Gap toward Scale-up and Commercialization.

CO2 electroreduction (CO2E) converts CO2 into carbon-based fuels and chemical feedstocks that can be integrated into existing chemical processes. After decades of research, CO2E is approaching commercialization with several startups, pilot plants, and large initiatives targeting different products. Here, we analyze the global efforts in scaling up CO2E, addressing implementation challenges and proposing methods for acceleration. We present a comparative analysis of key performance indicators (KPIs) between laboratory and industrial settings and suggest a stepwise technoeconomic analysis (TEA) framework, supported by industrial data, exploiting interactions within the academic and industrial communities. We identify the lack of systems-oriented standardization and durability as the main bottlenecks slowing down progress in the lab-to-prototype-to-market pathway of CO2E technologies. Inspired by electrolysis and fuel cell technologies, we outline protocols to advance fundamental research and aid catalyst development progress in performance, upscaling, and technology readiness level of CO2E.

Investigating CO2 electro-reduction mechanisms: DFT insight into earth-abundant Mn diimine catalysts for CO2 conversions over hydrogen evolution reaction, feasibility, and selectivity considerations

Investigating CO2 electro-reduction mechanisms: DFT insight into earth-abundant Mn diimine catalysts for CO2 conversions over hydrogen evolution reaction, feasibility, and selectivity considerations

Theoretical investigation of sustainable CO2 electroreduction to high-value products utilizing N-doped/BN-modified Triphenylene-Graphdiyne catalysts

The potential of carbon-based triphenylene-graphdiyne (tpGDY) and its derivatives for the electrochemical CO2 reduction reaction (eCO2R) was comprehensively explored using density functional theory (DFT) calculations. Six variants were studied: pristine tpGDY, tpGDY-BN, tpGDY-N01, tpGDY-N02, tpGDY-N08, and tpGDY-BN-B01. Pristine tpGDY, tpGDY-BN, and tpGDY-N08 exhibited exceptional catalytic activity, efficiently converting CO2 into CO and HCOOH without external energy input. Significantly, N-doped tpGDY catalysts incorporating sp2-hybridized nitrogen atoms at the acetylenic sites (tpGDY-N01 and tpGDY-BN-N01) demonstrated remarkable electrocatalytic activity for the targeted conversion of CO2 to CH3OH. This outstanding performance is further corroborated by the low limiting potentials of −0.18 V and −0.27 V for tpGDY-N01 and tpGDY-BN-N01, respectively, highlighting their economic viability. Furthermore, the feasibility of C2 production (e.g., C2H5OH, C2H4 and C2H6) through C–C coupling of *CHO+*CO intermediate was investigated for tpGDY-N01 and tpGDY-BN-N01. DFT calculations suggest these pathways are achievable but require potentials of 0.84 V and 0.71 V for tpGDY-N01 and tpGDY-BN-N01, respectively. This study demonstrates the efficacy of N-doped tpGDY as a metal-free electrocatalyst for CO2 reduction, enabling the generation of both C1 and C2 products. This discovery holds significant promise for the advancement of sustainable CO2 conversion technologies.

Ni-Electrocatalytic CO2 Reduction Toward Ethanol.

The electroreduction of CO2 offers a sustainable route to generate synthetic fuels. Cu-based catalysts have been developed to produce value-added C2+ alcohols; however, the limited understanding of complex C-C coupling and reaction pathway hinders the development of efficient CO2-to-C2+ alcohols catalysts. Herein, a Cu-free, highly mesoporous NiO catalyst, derived from the microphase separation of a block copolymer,is reported, which achieves selective CO2 reduction toward ethanol with a Faradaic efficiency of 75.2% at -0.6V versus RHE. The dense mesopores create a favorable local reaction environment with CO2-rich and H2O-deficient interfaces, suppressing hydrogen evolution and maximizing catalytic activity of NiO for CO2 reduction. Importantly, the C1-feeding experiments, in situ spectroscopy, and theoretical calculations consistently show that the direct coupling of *CO2 and *COOH is responsible for C-C bond formation on NiO, and subsequent reduction of *CO2-COOH to ethanol is energetically facile through the *COCOH and *OC2H5 pathway. The unconventional C-C coupling mechanism on NiO, in contrast to the *CO dimerization on Cu, is triggered by strong CO2 adsorption on the polarized Ni2+-O2- sites. The work not only demonstrates a highly selective Cu-free Ni-based alternative for CO2-to-C2+ alcohols transformation but also provides a new perspective on C-C coupling toward C2+ synthesis.

Enhancing CO2 electroreduction to ethylene via microenvironment regulation in boron-imidazolate frameworks.

Using the structure-induced effect of KBH(mim)3 ligand, four 2-dimensional (2D) boron imidazolate frameworks with identical body framework and different dangling monocarboxylate ligands, have been synthesized. Electrocatalytic results indicate that the surrounding microenvironment regulation could effectively affect the activity and selectivity towards C2H4. BIF-151 showed the highest electrocatalytic performances with the Faraday efficiency (FE) of 25.94% for C2H4 at -1.4 V vs. RHE.

Manipulation of Oxygen Species on an Antimony-Modified Copper Surface to Tune the Product Selectivity in CO2 Electroreduction.

Rational regulation of the electrochemical CO2 reduction reaction (CO2RR) pathway to produce desired products is particularly interesting, yet designing economical and robust catalysts is crucial. Here, we report an antimony-modified copper (CuSb) catalyst capable of selectively producing both CO and multicarbon (C2+) products in the CO2RR. At a current density of 0.3 A/cm2, the faradaic efficiency (FE) of CO was as high as 98.2% with a potential of -0.6 V vs reversible hydrogen electrode (RHE). When the current density increased to 1.1 A/cm2 at -1.1 V vs RHE, the primary products shifted to C2+ compounds with a FE of 75.6%. Experimental and theoretical studies indicate that tuning the potential could manipulate the oxygen species on the CuSb surface, which determined the product selectivity in the CO2RR. At a more positive potential, the existence of oxygen species facilitates the potential-limiting step involving *COOH formation and reduces the adsorption of *CO intermediates, thereby promoting CO production. At a more negative potential, the localized high CO concentration coupled with the enhanced adsorption of *CO intermediates due to Sb incorporation facilitates C-C coupling and deep hydrogenation processes, resulting in an increased C2+ selectivity.

Highthroughput Screening of CuBi Bimetallic Catalyst Array for Electrocatalytic CO2 Reduction Reaction by Scanning Electrochemical Microscope.

The testing and evaluation of catalysts in CO2 electroreduction is a very tedious process. To study the catalytic system of CO2 reduction more quickly and efficiently, it is necessary to establish a method that can detect multiple catalysts at the same time. Herein, a series of CuBi bimetallic catalysts have been successfully prepared on a single glass carbon electrode by a scanning micropieptte contact method. The application of scanning electrochemical microscopy (SECM) enabled the visualization of the CO2 reduction activity in diverse catalyst micro-points. The SECM imaging with Substrate generation/tip collection (SG/TC) mode was conducted on CuBi bimetallic micro-points, revealing that HER reaction emerged as the prevailing reaction when a low overpotential was employed. While the applied potential was lower than -1.5 V vs. Ag/AgCl, the reduction of CO2 to formic acid became dominant. Increasing the bismuth proportion in the bimetallic catalyst can inhibit the hydrogen evolution reaction at low potential and enhances the selectivity of the CO product at high cathode overpotential. This research offers a novel approach to examining arrays of catalysts for CO2 reduction.

Size and Morphology Dependent Activity of Cu Clusters for CO2 Activation and Reduction: A First Principles Investigation.

Various Cu-based materials in diverse forms have been investigated as efficient catalysts for electrochemical reduction of CO2; however, they suffer from issues such as higher over potential and poor selectivity. The activity and selectivity of CO2 electro reduction have been shown to change significantly when the surface morphology (steps, kinks, and edges) of these catalysts is altered. In light of this, size and morphology dependent activity of selected copper clusters, Cun (n=2-20) have been evaluated for the activation and reduction of CO2 molecule. The phase-space of these copper clusters is rich in conformations of distinct morphologies starting from planar, 2D geometries to prolate-shaped geometries and also high-symmetry structures. The binding efficiency and the activation of CO2 are highest for medium sized clusters (n=9-17) with prolate-morphologies as compared to small or larger sized CunCO2 clusters that are existing mainly as planar (triangular, tetragonal etc.) or highly-symmetric geometries (icosahedron, capped-icosahedron etc.), respectively. The best performing (prolate-shaped) CunCO2 conformations are quite fluxional and also they are thermally stable, as demonstrated by the molecular dynamics simulations. Furthermore, on these CunCO2 conformations, the step-by-step hydrogenation pathways of CO2 to produce value-added products like methanol, formic acid, and methane are exceptionally favorable and energy-efficient.

Key intermediates and Cu active sites for CO2 electroreduction to ethylene and ethanol

Key intermediates and Cu active sites for CO2 electroreduction to ethylene and ethanol

High oxidation state on porous Ga-Ag9In4 catalyst enhance CO2 electroreduction to CO

The oxidation state of Ga, In and Ag active sites for the selective electrochemical conversion of CO2 to CO has been successfully modulated through the construction of a porous Ga-Ag9In4 liquid alloy catalyst. X-ray photoelectron spectroscopy measurements confirmed the formation of a higher amount of oxidized states on the high-performing Ga-Ag9In4 electrode surface during the CO2 reduction reaction process. Based on density functional theory calculations, the Ga-Ag9In4 catalyst with a high oxidized species exhibits an electronic-rich surface that promotes CO2 adsorption and activation. In a H-type electrolysis cell, the porous Ga-Ag9In4 catalyst exhibits a maximum Faradaic efficiency of 88 % for CO production, with current densities of 30.2 mA·cm−2. This strategy of porous liquid alloy engineering and oxidation state modulation in multicomponent systems has good application prospect and research value for enhancing electrocatalytic performance.

Stabilized Cu0 -Cu1+ dual sites in a cyanamide framework for selective CO2 electroreduction to ethylene

Electrochemical reduction of carbon dioxide to produce high-value ethylene is often limited by poor selectivity and yield of multi-carbon products. To address this, we propose a cyanamide-coordinated isolated copper framework with both metallic copper (Cu0) and charged copper (Cu1+) sites as an efficient electrocatalyst for the reduction of carbon dioxide to ethylene. Our operando electrochemical characterizations and theoretical calculations reveal that copper atoms in the Cuδ+NCN complex enhance carbon dioxide activation by improving surface carbon monoxide adsorption, while delocalized electrons around copper sites facilitate carbon-carbon coupling by reducing the Gibbs free energy for *CHC formation. This leads to high selectivity for ethylene production. The Cuδ+NCN catalyst achieves 77.7% selectivity for carbon dioxide to ethylene conversion at a partial current density of 400 milliamperes per square centimeter and demonstrates long-term stability over 80 hours in membrane electrode assembly-based electrolysers. This study provides a strategic approach for designing catalysts for the electrosynthesis of value-added chemicals from carbon dioxide.

Gapped and Rotated Grain Boundary Revealed in Ultra-Small Au Nanoparticles for Enhancing Electrochemical CO2 Reduction.

Although gapped grain boundaries have often been observed in bulk and nanosized materials, and their crucial roles in some physical and chemical processes have been confirmed, their acquisition at ultrasmall nanoscale presents a significant challenge. To date, they had not been reported in metal nanoparticles smaller than 2 nm owing to the difficulty in characterization and the high instability of grain boundary (GB) atoms. Herein, we have successfully developed a synthesis method for producing a novel chiral nanocluster Au78(TBBT)40 (TBBT=4-tert-butylphenylthiolate) with a 26-atom gapped and rotated GB. This nanocluster was precisely characterized using single-crystal X-ray crystallography and mass spectrometry. Additionally, an offset atomic defect linked to the peripheral Au(TBBT)2 staple was found in the structure. Comparing it to similarly face-centered cubic-structured Au36(TBBT)24, Au44(TBBT)28, Au52(TBBT)32, Au92(TBBT)44, and ~5 nm nanocrystals, the bridging Au78(TBBT)40 nanocluster exhibited higher catalytic activity in the electroreduction of CO2 to CO. This enhanced activity was explained through density functional theory calculations and X-ray photoelectron spectroscopy analysis, which highlight the impact of GBs and point defects on the surface properties of metal nanoclusters in balancing intermediate adsorption and product desorption.

Revolutionizing CO2‐to‐C2 Conversion: Unleashing the Potential of CeO2 Nanocores for Self‐ Supported Electrocatalysts with Cu2O Nanoflakes on 3D Graphene Aerogel

AbstractCu serves as a promising electrocatalyst for converting CO2 into valuable C2 products in CO2 reduction reactions (CO2RR). However, instability in CO* formation is crucial for CO2 adsorption‐ desorption still remains a challenge under reduction conditions. This study explores the impact of lanthanide oxide, particularly CeO2, on Cu‐based catalytic performances. By leveraging Ce's distinctive electronic structure, CO* species are stabilized during the reaction in CeO2─Cu2O, resulting in exceptional catalytic performance for CO2 electroreduction to C2 products. Hybridizing CeO2‐Cu2O with graphene aerogel enhances electrochemical active surface area and CO2RR efficiency. The resulting CeO2─Cu2O(10%)/GA electrocatalyst exhibits a remarkable faradaic efficiency for C2 products, exceeding 62%, alongside exceptional stability over 80 h with wide potential window (−0.8 to −1.2 V) using a H‐cell. Systematic investigations elucidate the intricate interplay between surface properties and catalytic activity. Furthermore, a solar cell‐ powered CO2 reduction system demonstrates consistent performance (−27.8 mA cm−2 at 3.46 V) under solar radiation of ≈100 mW cm−2, showcasing outstanding stability with nearly 100% retention over 4 h of continuous illumination. In short, by harnessing catalytic and electronic effects, this innovation advances the development of electrocatalysts with heightened CO2‐to‐C2 selectivity, bridging fundamental research with technological innovation to tackle critical global challenges.

Revealing Real Active Sites in Intricate Grain Boundaries Assemblies on Electroreduction of CO2 to C2+ Products

AbstractAlthough intricate structural assemblies contribute to enhancing the activity of electrocatalytic CO2 reduction (ECR) to C2+ products, blindly coupling multiple design strategies may not yield the expected results, and even inhibit the activity of intrinsic catalytic sites. Therefore, elucidating the promoting or inhibitory effects of each design strategy on the CO2‐to‐C2+ conversion to clarify the real active sites and dynamic oxidation processes is of paramount importance. Here, commonly used grain boundaries (GBs), oxidation states, and alloying strategies are focused on, constructing four different types of catalysts structures: original Cu GBs, oxygen‐enriched grain boundary oxidation (GBO), Ag‐enriched GBO, and Cu/Ag GBs. Multiple operando characterizations reveal that GBs and GBO strengthen the resistance of the oxidative Cu species to the electrochemical reduction. The in situ generated strongly oxidative hydroxyl radicals alter the local reaction environment on the catalyst surface, inducing and stabilizing oxidative Cuδ+ species. Catalytic activity comparisons indicate that the oxidation state of Cu plays a decisive role in the CO2‐to‐C2+ conversion, and the nanoalloy effect tends to favor the CH4 production in intricate GBs assemblies. Theoretical calculations suggest that weak CO adsorption on GBO structures facilitates hydrogenation, promoting C–C coupling toward C2+ products.

Fabrication of porous Au/Cu alloy catalyst for CO2 electro-reduction to CO in three-chamber electrolyzer: With Cl2 and NaOH produced as byproducts

A three-compartment electrolyzer has been developed for the electro-reduction of CO2 to CO in an organic electrolyte, with NaOH and Cl2 produced as byproducts. In order to improve the performance of the electrolyzer, we have prepared an Au/Cu alloy electrode using a novel non-cyanide electroplating method with high porosity. By expanding the specific surface area of the cathode, and providing a large number of active sites for CO2 electro-reduction, the cathodic current density reaches to 92.7 mA·cm−2, and the Faradaic efficiency of CO formation remains stable at 94.0 %. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations analysis identified that alloying tune the electronic structure of the Au and Cu surface, resulting in promoting the activation of CO2.