CO2 Electroreduction Research Articles

Manganese Doped‐Nitrogenated Carbon as an Efficient Catalyst for Acidic Electrocatalytic Reduction of CO2

AbstractRenewable electricity‐driven CO2 electroreduction to value‐added chemicals is a feasible approach to alleviate both environmental and energy issues. However, CO2 reduction reaction (CO2RR) systems in alkaline electrolytes are constrained by intrinsic limitations such as salt accumulation that impede further industrialization. Herein, an atomically dispersed Mn doped‐nitrogen carbon (AD MnNC) catalyst is developed to electrochemically reduce CO2 to CO in both neutral and acidic media. Benefiting from well‐dispersed MnNx sites, the maximum CO Faradaic efficiency (FECO) reaches ≈100% at −0.73 V versus reversible hydrogen electrode (RHE) with CO current density (JCO) of 20.4 mA cm−2 in neutral 0.5 m KHCO3. Due to diminished *H adsorption, AD MnNC achieves a FECO of 85.3% at pH 2.0, effectively suppressing the hydrogen evolution reaction (HER) in an acidic electrolyte. The mechanistic study reveals that AD MnNC accelerates the production of *COOH intermediates through a proton‐coupled electron transfer (PCET) pathway and thus promotes CO formation.

Why do CuAl catalysts outperform in CO2 electro-reduction to C2H4?

Why do CuAl catalysts outperform in CO2 electro-reduction to C2H4?

Modulation of charge structure in Bi/Bi2O3-In2O3@C for efficient CO2 electroreduction to formate

Electrocatalytic CO2 reduction reaction (ECO2RR) to value-added chemicals is of significant importance to control CO2 emission and reach carbon neutrality. Herein, Bi/Bi2O3-In2O3@C electrocatalyst with nanosheet arrays is successfully fabricated by a facile solvothermal with subsequent calcination process. It is found that the electron structure of Bi/Bi2O3-In2O3@C can be adjusted by the synergistic effects of Bi-In hetero-diatoms, which can significantly enhance its inherent catalytic activity. As expected, it requires a maximum HCOOH faradaic efficiency (FEHCOOH) of 97.6 % at −1.1 V vs. Reversible Hydrogen Electrode (RHE), which further delivers over 90 % at a wide potential range of −0.8 to −1.4 V vs. RHE, and exhibits high stability of 90.1 % over 60-h long-term test. In-situ Raman analysis is performed to explore the mechanism of its excellent stability. Meanwhile, in-situ attenuated total reflection-Fourier-transform infrared (ATR-FTIR) analysis combined with theoretical calculations reveal that the hetero-bridging absorption of *OCHO and d-d orbital coupling effect can regulate d-band center of Bi/Bi2O3-In2O3@C and improve its density of states around Ef, moderating free energy of intermediates, thereby the improved formate production performance can be seen.

Mg-Doped Cu Catalyst for Electroreduction of CO2 to Multicarbon Products: Lewis Acid Sites Simultaneously Promote *CO Adsorption and Water Dissociation.

The electroreduction of CO2 to valuable fuels or high-value chemicals by using sustainable electric energy provides a promising strategy for solving environmental problems dominated by the greenhouse effect. Copper-based materials are the only catalysts that can convert CO2 into multicarbon products, but they are plagued by high potential, low selectivity, and poor stability. The key factors to optimize the conversion of CO2 into multicarbon products are to improve the adsorption capacity of intermediates on the catalyst surface, accelerate the hydrogenation step, and improve the C-C coupling efficiency. Herein, we successfully doped Lewis acid Mg into Cu-based materials using a simple liquid-phase chemical method. In situ Raman and FT-IR tracking show that the Mg site enhances the surface coverage of the *CO intermediate, simultaneously promoting water dissociation. Under an industrial current density of 0.7 A cm-2, the FEC2+ reaches 73.9 ± 3.48% with remarkable stability. Density functional theory studies show that doping the Lewis acid Mg site increases the coverage of *CO and accelerates the splitting of water, thus promoting the C-C coupling efficiency, reducing the reaction energy barrier, and greatly improving the selectivity of C2+ products.

Dimensional effect of oxide-derived Cu electrocatalysts to reduce CO2 into multicarbon compounds

Oxide-derived Cu (OD-Cu) are the most promising catalysts for multicarbon formation via CO2 electroreduction (CO2ERR), yet facing structural/compositional reconstruction trends during CO2ERR. Nanocatalysts with specific mesoscopic morphology are more resistant to reconstruction, which would benefit systematical exploration of dimensional effects on CO2ERR. Herein, nanostructured OD-Cu catalysts of 1D nanowires (NWs), 2D nanosheets (NSs) and 3D nanoflowers (NFs) with good reconstruction resistance during CO2ERR are fabricated. Their well-preserved dimensional structures lead to altered Cu–O coordination, which is intensively investigated via X-ray absorption fine structure spectroscopy, resulting in distinctive CO2ERR performances. OD-Cu NWs catalyst with the highest Cu–O coordination possesses an impressive 77.7 % C2+ faradaic efficiency. Further in situ Fourier-transformed infrared spectroscopy and density functional theory calculations suggest more favorable asymmetric C–C coupling over the highest Cu–O coordination surface of OD-Cu NWs. This work provides new insights on developing reconstruction-resistant OD-Cu catalysts for value-added chemicals from advanced CO2 conversion.

In situ activation of Sn(OH)4 catalyst for efficient CO2 electroreduction to formate

Electroreduction of CO2 into the highly valuable fuel formic acid (HCOOH) has been considered an ideal method for converting renewable energy and addressing environmental challenges. Herein, we present a straightforward and rapid method for preparing Sn(OH)4 catalysts specifically designed for electroreducing CO2 to formate. The Sn(OH)4 catalyst obtained through in-situ electrochemical reduction transforms from bulk morphology to nanoporous form, featuring numerous grain boundaries and a high hydroxyl content, enhancing its stability and availability of active sites.The resulting electrocatalyst demonstrates a remarkable formate faradaic efficiency (FEformate) exceeding 80 % across a broad potential range (−0.9 to −1.9 V). Notably, a peak FE value of 92 % is achieved for HCOOH production at −1.7 V vs RHE. This study presents a novel and effective method for developing high-performance Sn-based catalysts.

Shaping hollow spherical assemblies for enhanced Cu0/Cu+ interface to boost C2+ selectivity in CO2 electroreduction

Shaping hollow spherical assemblies for enhanced Cu0/Cu+ interface to boost C2+ selectivity in CO2 electroreduction

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.

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