Multicarbon Products Research Articles

Highly selective electrocatalytic CO2 reduction to multi-carbon products at CuPd synergistic sites over OD-Cu based catalysts

CO2 reduction is a potential way to kill two birds with one stone by converting greenhouse gas into fuels through clean energy. Cu-based catalysts, with a wide range of products, often have limited selectivity and low activity for specific products. In this study, Cu2O was used as the oxide-derived copper (OD-Cu) substrate, which was loaded with CuPd nanoparticles by using pulsed potential and galvanic replacement. Theoretical calculations revealed that the strong H-affinity Pd sites can reduce the selectivity of formate by stabilizing *COOH and simultaneously lowering the d-band center of neighboring Cu. Additionally, the asymmetric C–C coupling of *CHO+*CO, distributed between Cu and Pd sites, can lower the free energy change of rate-determining step to promote production of the C2+ products. Faradaic efficiency (FE) of the C2+ products over Cu2O-CuPd0.5μM was more than three times higher than that over untreated Cu2O NW, rising from 16.50 % to 54.47 % under −1 V (vs RHE) bias. Moreover, the FE for formate and CO decreased respectively from 28.57 % and 19.30 % to 3.69 % and 11.82 %, accompanied by a simultaneous increase in current density by 71.49 %.

Detection of electrocatalytical and -chemical processes by means of in situ flow NMR spectroscopy

In situ studies of electrochemical processes using NMR offer valuable information on reaction mechanisms, kinetics, and species identification, making it a powerful tool in electrochemistry research. In this study, we present the design of an in situ redox-flow NMR cell that allows for a continuous flow of liquid (electrolyte) or gas, application of electrical voltage, and recording of NMR signals. The utility of this setup is demonstrated through two case studies: electrochemical copper deposition on a gold electrode and the electrochemical conversion of carbon dioxide into hydrocarbon products. Specifically, the presence of multicarbon products containing C–C bonds generated during the electrochemical reduction reaction is confirmed in the 2H NMR spectra in the latter example. These findings highlight the ability of the in situ redox-flow NMR cell to directly monitor reaction intermediates and products, thereby enabling the elucidation of reaction mechanisms for the efficient and selective production of valuable hydrocarbon products through the conversion of CO2 into value-added chemicals. In contrast to other reported in situ NMR cells, the presented cell is suitable for multiple uses, and allows detecting NMR signals not only from exhaust products but also from those formed on the catalyst surface.

Cathode Surface pH Modulates Multicarbon Product Selectivity during the Electrochemical Conversion of CO2 Capture Solutions

Cathode Surface pH Modulates Multicarbon Product Selectivity during the Electrochemical Conversion of CO₂ Capture Solutions

Local CO Generator Enabled by a CO-Producing Core for Kinetically Enhancing Electrochemical CO2 Reduction to Multicarbon Products.

CO plays a crucial role as an intermediate in electrochemical CO2 conversion to generate multicarbon (C2+) products. However, optimizing the coverage of the CO intermediate (*CO) to improve the selectivity of C2+ products remains a great challenge. Here, we designed a hierarchically structured double hollow spherical nanoreactor featuring atomically dispersed nickel (Ni) atoms as the core and copper (Cu) nanoparticles as the shell, which can greatly improve the catalytic activity and selectivity for C2+ compounds. Within this configuration, CO generated at the active Ni sites on the inner layer accumulates in the cavity before spilling over neighboring Cu sites on the outer layer, thus enhancing CO dimerization within the cavity. Notably, this setup achieves a sustained faradaic efficiency of 74.4% for C2+ production, with partial current densities reaching 337.4 mA cm-2. In situ Raman spectroscopy and finite-element method (FEM) simulations demonstrate that the designed local CO generator can effectively increase the local CO concentration and restrict CO evolution, ultimately boosting C-C coupling. The hierarchically ordered architectural design represents a promising solution for achieving highly selective C2+ compound production in the electroreduction of CO2.

Dinuclear Cu(I) molecular electrocatalyst for CO2-to-C3 product conversion

Molecular metal complex catalysts are highly tunable in terms of their CO2 reduction performance by means of their flexible molecular design. However, metal complex catalysts have challenges in their structural stability and it has not been possible to synthesize high-value-added C3 products due to their inability to perform C–C coupling. Here we show a CO2 reduction reaction catalysed by a Br-bridged dinuclear Cu(I) complex that produces C3H7OH with high robustness during the reaction. The C–C coupling reaction mechanism was analysed by experimental operando surface-enhanced Raman scattering analysis, and theoretical quantum-chemical calculations proposed the formation of a C–C coupling intermediate species with substrate incorporation between the two Cu centres. Molecular design guidelines based on this discovery offer an approach to developing next-generation catalysts that generate multicarbon CO2 reduction products.

Tailoring Microenvironments and In Situ Transformations of Cu Catalysts for Selective and Stable Electrosynthesis of Multicarbon Products

AbstractElectrochemical CO2 reduction is of tremendous interest for storing chemical energy from renewable sources while reducing CO2 emissions. While copper is one of the most effective catalysts, it suffers from low selectivity and limited long‐term durability. Here, these limitations are overcome by engineering Nafion coatings on CuO nanoparticle‐based catalysts supported on glassy carbon. By tuning the Nafion thickness and internal structure, it is shown that both the selectivity to multicarbon (C2+) products and long‐term stability can be dramatically enhanced. Optimized catalyst layers reach Faradaic efficiencies for C2+ products of 86% during long‐term testing for 200 h, with no evidence for performance degradation. Indeed, the C2+ Faradaic efficiency increases during testing, which is attributed to favorable in situ electrochemical fragmentation of catalytic nanoparticles. Finally, the optimized Nafion/Cu catalytic coatings are utilized to create scalable membrane electrode assemblies for CO2 electrolysis, yielding significantly enhanced C2H4 selectivity (≈58%) and activity at technologically‐relevant currents of 1–2 A. These results highlight the potential for creating multi‐functional Nafion coatings on CO2 reduction catalysts to favorably tune the reaction environment, while also promoting in situ transformations to active and selective nanoscale structures and morphologies, not just on model surfaces but also in state‐of‐the‐art gas diffusion electrodes.

Copper nanoclusters: Selective CO2 to methane conversion beyond 1 A/cm²

Carbon dioxide offers a unique opportunity as a feedstock for energy production through electrocatalysis. Methane production holds promise for its widespread applications and market demand. However, commercial viability faces challenges of low selectivity, current density, and high applied potential. Efforts to improve methane selectivity while suppressing multi-carbon products, e.g., ethylene, often involve lower alkalinity electrolytes. However, it reduces current density due to increased ohmic resistance without significant gains in the reaction yield. This study utilizes quantum mechanics computations to design a nano-cluster copper catalyst that redirects the reaction pathway from ethylene towards methane, even under alkaline conditions. We achieved a Faradaic efficiency (FE) of 85 %, a current density of 1.5 A/cm2, and stability of over 10 hours solely by controlling particle size in copper catalysts. This work paves the way to overcoming current limitations in electrocatalytic methane production and holds broader implications for advancing sustainable CO2 utilization in energy systems.

Ligand-modified nanoparticle surfaces influence CO electroreduction selectivity

Improving the kinetics and selectivity of CO2/CO electroreduction to valuable multi-carbon products is a challenge for science and is a requirement for practical relevance. Here we develop a thiol-modified surface ligand strategy that promotes electrochemical CO-to-acetate. We explore a picture wherein nucleophilic interaction between the lone pairs of sulfur and the empty orbitals of reaction intermediates contributes to making the acetate pathway more energetically accessible. Density functional theory calculations and Raman spectroscopy suggest a mechanism where the nucleophilic interaction increases the sp2 hybridization of CO(ad), facilitating the rate-determining step, CO* to (CHO)*. We find that the ligands stabilize the (HOOC–CH2)* intermediate, a key intermediate in the acetate pathway. In-situ Raman spectroscopy shows shifts in C–O, Cu–C, and C–S vibrational frequencies that agree with a picture of surface ligand-intermediate interactions. A Faradaic efficiency of 70% is obtained on optimized thiol-capped Cu catalysts, with onset potentials 100 mV lower than in the case of reference Cu catalysts.

Nanoconfinement Enables Photoelectrochemical Selective Oxidation of Glycerol via the Microscale Fluid Effect.

The glycerol oxidation reaction (GOR) run with photoelectrochemical cells (PECs) is one of the most promising ways to upgrade biomass because it is thermodynamically favorable, while irreversible overoxidation leads to unsatisfactory product selectivities. Herein, a tunable one-dimensional nanoconfined environment was introduced into the GOR process, which accelerated mass transfer of glycerol via the microscale fluid effect and changed the main oxidation product from formic acid (FA) to glyceraldehyde (GLD), which led to retention of the heavier multicarbon products. The rate of glycerol diffusion in the nanochannels increased by a factor of 4.92 with decreasing inner diameters. The main product from the PEC-selective oxidation of glycerol changed from the C1 product FA to the C3 product GLD with a great selectivity of 60.7%. This work provides a favorable approach for inhibiting further oxidation of multicarbon products and illustrates the importance of microenvironmental regulation in biomass oxidation.

Triazine-COF@Silicon nanowire mimicking plant leaf to enhance photoelectrocatalytic CO2 reduction to C2+ chemicals

Triazine-COF@Silicon nanowire mimicking plant leaf to enhance photoelectrocatalytic CO2 reduction to C2+ chemicals

Modulating surface microenvironment based on Ag-adorned CuO flower-liked nanospheres for strengthening C-‍C coupling during CO2RR

Modulating the surface microenvironment is crucial in strengthening CC coupling, leading to increasing selectivity in the production of multi-carbon (C2+) products during CO2 electroreduction. Herein, we have concentrated on investigating how to control the effect of surface distribution of active components of a series of Ag-decorated CuO, denoted as xAg/yCuO. These catalysts with similar chemical elements and morphology are designed, but they exhibit different selectivity in the CO2 electroreduction process. As a result, the Ag particles in 3Ag/CuO aggregates, while the Ag in 2Ag/2CuO and Ag/3CuO is uniformly distributed on the flower-like CuO nanosphere. Besides, 3Ag/CuO has the highest Faraday efficiency (FE) of CO with a value of 30.9 % at 0.8 V vs. RHE, demonstrating rich-Ag catalysts are beneficial to produce CO. 2Ag/2CuO shows excellent FEC2H4 of 51.4 % at -1.2 V vs. RHE due to the highly dispersed distribution of Ag on the flower-like CuO and higher vacancy O. Ag/3CuO exhibits higher FEH2 compared to other catalysts across a wide potential range, and its minimal impedance is attributed to its exceptional performance in the hydrogen evolution reaction. The proposed reaction pathway for the most effective catalysts 2Ag/2CuO, as determined by in-situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), involves the following steps: CO2 →*CO2−→ *COOH → *CO→ *CHO→ *OCHCHO→ *OCHCH2→ C2H4. These findings demonstrate that controlling the surface structure can influence the local environment to enhance the efficiency of CO2 electroreduction.

Engineering NH2-Cu-NH2 Triple-atom Sites in Defective MOFs for Selective Overall Photoreduction of CO2 into CH3COCH3.

Selective photoreduction of CO2 to multicarbon products, is an important but challenging task, due to high CO2 activation barriers and insufficient catalytic sites for C-C coupling. Herein, a defect engineering strategy for incorporating copper sites into the connected nodes of defective metal-organic framework UiO-66-NH2 for selective overall photo-reduction of CO2 into acetone. The Cu2+ site in well-modified CuN2O2 units served as a trapping site to capture electrons via efficient electron-hole separation, forming the active Cu+ site for CO2 reduction. Two NH2 groups in CuN2O2 unit adsorb CO2 and cooperated with copper ion to functionalize as a triple atom catalytic site, each interacting with one CO2 molecule to strengthen the binding of *CO intermediate to the catalytic site. The deoxygenated *CO attached to the Cu site interacted with *CH3 fixed at one amino group to form the key intermediate CO*-CH3, which interacted with the third reduction intermediate on another amino group to produce acetone. Our photocatalyst realizes efficient overall CO2 reduction to C3 product acetone CH3COCH3 with an evolution rate of 70.9 μmol gcat -1 h-1 and a selectivity up to 97 % without any adducts, offering a promising avenue for designing triple-atomic sites to producing C3 product from photosynthesis with water.

Enhanced CO2 Electroreduction to Multi-Carbon Products on Copper via Plasma Fluorination.

The electroreduction of carbon dioxide (CO2) to multi-carbon (C2+) compounds offers a viable approach for the up-conversion of greenhouse gases into valuable fuels and feedstocks. Nevertheless, current industrial applications face limitations due to unsatisfactory conversion efficiency and high overpotential. Herein, a facile and scalable plasma fluorination method is reported. Concurrently, self-evolution during CO2 electroreduction is employed to control the active sites of Cu catalysts. The copper catalyst modified with fluorine exhibits an impressive C2+ Faradaic efficiency (FE) of 81.8% at a low potential of -0.56V (vs a reversible hydrogen electrode) in an alkaline flow cell. The presence of modified fluorine leads to the exposure and stabilization of high-activity Cu+ species, enhancing the adsorption of *CO intermediates and the generation of *CHO, facilitating the subsequent dimerization. This results in a notably improved conversion efficiency of 13.1% and a significant reduction in the overpotential (≈100mV) for the C2+ products. Furthermore, a superior C2+ FE of 81.6% at 250mAcm-2, coupled with an energy efficiency of 31.0%, can be achieved in a two-electrode membrane electrode assembly electrolyzer utilizing the fluorine-modified copper catalyst. The strategy provides novel insights into the controllable electronic modification and surface reconstruction of electrocatalysts with practical potential.

Engineering NH2‐Cu‐NH2 Triple‐atom Sites in Defective MOFs for Selective Overall Photoreduction of CO2 into CH3COCH3

AbstractSelective photoreduction of CO2 to multicarbon products, is an important but challenging task, due to high CO2 activation barriers and insufficient catalytic sites for C−C coupling. Herein, a defect engineering strategy for incorporating copper sites into the connected nodes of defective metal–organic framework UiO‐66‐NH2 for selective overall photo‐reduction of CO2 into acetone. The Cu2+ site in well‐modified CuN2O2 units served as a trapping site to capture electrons via efficient electron‐hole separation, forming the active Cu+ site for CO2 reduction. Two NH2 groups in CuN2O2 unit adsorb CO2 and cooperated with copper ion to functionalize as a triple atom catalytic site, each interacting with one CO2 molecule to strengthen the binding of *CO intermediate to the catalytic site. The deoxygenated *CO attached to the Cu site interacted with *CH3 fixed at one amino group to form the key intermediate CO*‐CH3, which interacted with the third reduction intermediate on another amino group to produce acetone. Our photocatalyst realizes efficient overall CO2 reduction to C3 product acetone CH3COCH3 with an evolution rate of 70.9 μmol gcat−1 h−1 and a selectivity up to 97 % without any adducts, offering a promising avenue for designing triple‐atomic sites to producing C3 product from photosynthesis with water.

Copper Electrocatalyst Produced by Cu2(OH)2CO3-Mediated In Situ Deposition for Diluted CO2 Reduction to Multicarbon Products.

Pure CO2 is commonly used in most of the current studies for electrochemical CO2 reduction which will need a further cost of gas purification and separation. However, the limited works on diluted CO2 reduction are focused on CO or CH4 production other than C2 products. In this work, copper electrocatalysts were prepared by Cu2(OH)2CO3-mediated in situ deposition for diluted CO2 reduction to multicarbon products. Using in situ Raman spectroscopy, constant amounts of CO and OH* were observed on the catalyst surface, which could effectively suppress the high kinetics of hydrogen evolution and promote C-C coupling, especially under the condition of diluted CO2 reduction. The optimized Cu catalyst achieves a C2 Faradaic efficiency as high as 60.72% in the presence of merely 25% CO2, which is almost equivalent to that observed with pure CO2.

Nanoreactor Confined and Enriched Intermediates for Electroreduction of CO2 to C2+ Products.

In the process of electroreduction of carbon dioxide (eCO2RR) to multi-carbon (C2+) products, it is imperative to enhance the concentration of key intermediate species on the catalyst surface. The utilization of micro-nano reactors to achieve confinement effects has been widely observed in various catalytic reactions, yet it has seldom been employed in eCO2RR. Here, we present a novel nanoreactor composed of stacked CuS nanosheets for eCO2RR to C2+ products. In comparison to catalyst comprising of nanosheet with open space, the C-C coupling within this confined nanospace is significantly enhanced, resulting in the increase of Faraday efficiency (FE) of C2+ products to 53 %. In situ infrared (IR) spectroscopy reveals the confinement and enrichment of key intermediate by the nanoreactor. Our research findings demonstrate that a meticulously designed nanoreactor can elevate the selectivity of C2+ products, thereby aiding in the design of eCO2RR catalysts.

Enhancing electrochemical carbon dioxide reduction efficiency through heat-induced metamorphosis of copper nanowires into copper oxide/copper nanotubes with tunable surface

Electrochemical CO2 reduction reaction (CO2RR) presents a unique opportunity to convert carbon dioxide (CO2) to value-added products while simultaneously storing renewable energy in the form of chemical energy. However, particle applications of this technology are limited due to the poor efficiency and product selectivity of the existing catalyst. In this study, we demonstrate a facile method for the heat-induced transformation of copper nanowires into CuOx/Cu nanotubes with defect-enriched surfaces. During this transformation, the outward migration of copper results in the formation of tubular structures encased within nanosized oxide grains. Notably, the hydrogen faradaic efficiency (FE) decreases with extended heat treatment, while carbon monoxide (CO) FE increases. As compared to Cu NWs, Cu NTs exhibit lower selectivity towards H2 and single-carbon (C1) products and favor the formation of multi-carbon (C2+) products. Consequently, a 2-fold increase in the single pass CO2 conversion (SPCC) and C2+ half-cell energy efficiency (EEhalf cell) was noted after heat treatment. The Cu NT-4 variant, synthesized under optimized conditions, exhibits the highest FE of 72.1 % for C2+ products at an operating current density (ID) of 500 mA cm−2.

Cooperation of Different Active Sites to Promote CO2 Electroreduction to Multi-carbon Products at Ampere-Level.

Electroreduction of CO2 to C2+ products provides a promising strategy for reaching the goal of carbon neutrality. However, achieving high selectivity of C2+ products at high current density remains a challenge. In this work, we designed and prepared a multi-sites catalyst, in which Pd was atomically dispersed in Cu (Pd-Cu). It was found that the Pd-Cu catalyst had excellent performance for producing C2+ products from CO2 electroreduction. The Faradaic efficiency (FE) of C2+ products could be maintained at approximately 80.8 %, even at a high current density of 0.8 A cm-2 for at least 20 hours. In addition, the FE of C2+ products was above 70 % at 1.4 A cm-2. Experiments and density functional theory (DFT) calculations revealed that the catalyst had three distinct catalytic sites. These three active sites allowed for efficient conversion of CO2, water dissociation, and CO conversion, ultimately leading to high yields of C2+ products.

Photothermal catalytic C–C coupling to ethylene from CO2 with high efficiency by synergistic cooperation of oxygen vacancy and half-metallic WTe2

Photothermal catalytic CO2 conversion provides an effective solution targeting carbon neutrality by synergistic utilization of photon and heat. However, the C–C coupling initiated by photothermal catalysis is still a big challenge. Herein, a three-dimensional (3D) hierarchical W18O49/WTe2 hollow nanosphere is constructed through in-situ embodying of oxygen vacancy and tellurium on the scaffold of WO3. The light absorption towards near-infrared spectral region and CO2 adsorption are enhanced by the formation of half-metal WTe2 and the unique hierarchical hollow architecture. Combining with the generation of oxygen vacancy with strengthened CO2 capture, the photothermal effect on the samples can be sufficiently exploited for activating the CO2 molecules. In particular, the close contact between W18O49 and WTe2 largely promotes the photoinduced charge separation and mass transfer, and thus the *CHO intermediate formation and fixedness are facilitated. As a result, the C–C coupling can be evoked between tungsten and tellurium atoms on WTe2. The ethylene production by optimized W18O49/WTe2 reaches 147.6 μmol g−1 with the selectivity of 80%. The in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations are performed to unveil the presence and significance of aldehyde intermediate groups in C–C coupling. The half-metallic WTe2 cocatalyst proposes a new approach for efficient CO2 conversion with solar energy, and may especially create a new platform for the generation of multi-carbon products.

Halide-modulated Hollow-Fiber Cu penetration electrode boosts Ampere-Level CO2 electroreduction to multicarbon products

Electroreduction of CO2 to chemical fuels is desirable for the economically viable use of CO2 and consumption of renewable electricity. Efficient production of C2+ on Cu-based catalysts remains a challenge. Herein, a copper hollow fiber penetration electrode with a striking C–C coupling capability by virtue of modulating the electronic states through halide ion coordinated adsorption. An efficient C2+ production with a FE of 68.8 % at 2.1 A cm−2 in 3.0 M KI and remained stable during 120-h electrolysis at 2.0 A cm−2, outperforming reported catalytic performance, which is the result of combined effect of penetration effect and halide ion coordinated adsorption, which promotes the transfer of electrons to CO2, reduces the C–C coupling energy and suppresses proton adsorption, thereby reducing hydrogen evolution.