CO2 Reduction Research Articles

High-Entropy Metal Sulfide Promises High-Performance Carbon Dioxide Reduction.

The efficient conversion of carbon dioxide (CO2) requires the development of stable catalysts with high selectivity and reactivity within a wide potential range. Here, the high-entropy metal sulfide CuAgZnSnS4 is designed for CO2 reduction with excellent performance (FEcarbonproducts ≥ 90%) in whole test potential windows (600 mV) based on the synergistic effect of the high-entropy metal sulfide. In particular, CuAgZnSnS4 exhibits better single-product selectivity with the highest FEHCOOH/FECO value (29.03) at -1.28 versus reversible hydrogen electrode (RHE). In combination with in situ measurements and theoretical calculations, it is further revealed that the synergistic effect of CuAgZnSnS4 realizes the controllable regulation of the surface electronic structure at Sn active sites, strengthening orbital interactions between *OCHO and Sn active sites. As a result, the effective adsorption and activation of *OCHO instead of *H are obtained, improving the single-product selectivity of electrocatalytic CO2 reduction and inhibiting the competitive hydrogen evolution reaction significantly. Our findings may complete the understanding of the synergistic effect for high-entropy materials in catalysis and offer new insight into the design of efficient electrocatalysts with high catalytic activity.

Highly Selective Electroreduction of Carbon Dioxide Using Defect-Driven Catalysis.

The production of methanol from the electrochemical reduction of CO2 is a promising method of mitigating climate change while simultaneously producing a useful liquid fuel. In this study, we design self-assembled monolayers (SAMs) of thiols on metal and metal oxide electrodes that operate via cooperative catalysis between the thiolated surface sites and exposed electrode defect sites. This defect-driven mechanism enables the fabrication of SAM-modified ZnO electrodes that yield methanol with an extraordinarily high Faradaic efficiency of up to 92%. To understand the origin of this high selectivity, we study the effect of the chain length of the alkanethiols, different tail functional groups, and applied voltages on catalyst performance. These results combined with density functional theory calculations give a detailed atomic-level understanding of catalyst operation. Furthermore, the SAM linkage tolerates CO2 reduction conditions, and the catalyst's excellent selectivity for methanol remains high after 10 h of continuous conversion. Taken together, these findings with SAM-based electrodes convey a new and facile design strategy for the creation of highly selective CO2 reduction electrocatalysts.

Room-Temperature Formate Ester Transfer Hydrogenation Enables an Electrochemical/Thermal Organometallic Cascade for Methanol Synthesis from CO2.

The reduction of CO2 to synthetic fuels is a valuable strategy for energy storage. However, the formation of energy-dense liquid fuels such as methanol remains rare, particularly under low-temperature and -pressure conditions that can be coupled to renewable electricity sources via electrochemistry. Here, a multicatalyst system pairing an electrocatalyst with a thermal organometallic catalyst is introduced, which enables the reduction of CO2 to methanol at ambient temperature and pressure. The cascade methanol synthesis proceeds via CO2 reduction to formate by electrocatalyst [Cp*Ir(bpy)Cl]+ (Cp* = pentamethylcyclopentadienyl, bpy = 2,2'-bipyridine), Fischer esterification of formate to isopropyl formate catalyzed by trifluoromethanesulfonic acid (HOTf), and thermal transfer hydrogenation of isopropyl formate to methanol facilitated by the organometallic catalyst (H-PNP)Ir(H)3 (H-PNP = HN(C2H4PiPr2)2). The isopropanol solvent plays several crucial roles: activating formate ion as isopropyl formate, donating hydrogen for the reduction of formate ester to methanol via transfer hydrogenation, and lowering the barrier for transfer hydrogenation through hydrogen bonding interactions. In addition to reporting a method for room-temperature reduction of challenging ester substrates, this work provides a prototype for pairing electrochemical and thermal organometallic reactions that will guide the design and development of multicatalyst cascades.

Novel Single Perovskite Material for Visible-Light Photocatalytic CO2 Reduction via Joint Experimental and DFT Study.

Developing advanced and economically viable technologies for the capture and utilization of carbon dioxide (CO2) is crucial for sustainable energy production from fossil fuels. Converting CO2 into valuable chemicals and fuels is a promising approach to mitigate atmospheric CO2 levels. Among various methods, photocatalytic reduction stands out for its potential to reduce emissions and produce useful products. Here, novel perovskite ZnMoFeO3 (ZMFO) nanosheets are presented as promising semiconductor photocatalysts for CO2 reduction. Experimental results show that ZMFO has a narrow bandgap, exceptional visible light response, large specific surface area, high crystallinity, and various surface-active sites, leading to an impressive photocatalytic CO2 reduction activity of 24.87 µmolg-1h-1 and strong stability. Theoretical calculations reveal that CO2 conversion into CO and CH4 on the ZMFO surface follows formaldehyde and carbine pathways. This study provides significant insights into designing innovative perovskite oxide-based photocatalysts for economical and efficient CO2 reduction systems.

Single-Atom-Layer Metallization of Plasmonic Semiconductor Surface for Selectively Enhancing IR-Driven Photocatalytic Reduction of CO2 into CH4.

Efficient harvesting and utilization of abundant infrared (IR) photons from sunlight is crucial for the industrial application of photocatalytic CO2 reduction. Plasmonic semiconductors have significant potential in absorbing low-energy IR photons to generate energetic hot electrons. However, modulating these hot electrons to selectively enhance the activity of CO2 reduction into CH4 remains a challenge. Herein, the study proposes a single-atom-layer (SAL) metallization strategy to enhance the generation of IR-driven hot electrons and facilitate their transfer from plasmonic semiconductors to CO2 for producing CH4. This strategy is demonstrated using a paradigmatic W18O49@W-Sn nanowire array (NWA), where Sn2+ ions are grafted onto exposed O atoms on the surface of plasmonic W18O49 to form a surface W-Sn SAL. The incorporation of Sn single atoms enhances plasmonic absorption in IR light for W18O49 NWA. The W-Sn SAL not only promotes CO2 adsorption and reduces its reaction activation energy barrier but also shifts the endoergic CO-protonation process toward an exoergic reaction pathway. Thus, the W18O49@W-Sn NWA exhibits >98% selectivity for IR-driven CO2 reduction to CH4 with an activity over 9.0 times higher than that of bare W18O49 NWA. This SAL metallization strategy can also be applied to other plasmonic semiconductors for selectively enhancing CO2-to-CH4 reduction reactions.

Boosting the Microbial Electrosynthesis of Formate by Shewanella oneidensis MR-1 with an Ionic Liquid Cosolvent.

Microbial electrosynthesis (MES) is a rapidly growing technology at the forefront of sustainable chemistry, leveraging the ability of microorganisms to catalyze electrochemical reactions to synthesize valuable compounds from renewable energy sources. The reduction of CO2 is a major target application for MES, but research in this area has been stifled, especially with the use of direct electron transfer (DET)-based microbial systems. The major fundamental hurdle that needs to be overcome is the low efficiency of CO2 reduction largely attributed to minimal microbial access to CO2 owing to its low solubility in the electrolyte. With their tunable physical properties, ionic liquids present a potential solution to this challenge and have previously shown promise in facilitating efficient CO2 electroreduction by increasing the CO2 solubility. However, the use of ionic liquids in MES remains unexplored. In this study, we investigated the role of 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) using Shewanella oneidensis MR-1 as a model DET strain. Electrochemical investigations demonstrated the ability of S. oneidensis MR-1 biocathodes to directly convert CO2 to formate with a faradaic efficiency of 34.5 ± 26.1%. The addition of [EMIM][Ac] to the system significantly increased cathodic current density and enhanced the faradaic efficiency to 94.5 ± 4.3% while concurrently amplifying the product yield from 34 ± 23 μM to 366 ± 34 μM. These findings demonstrate that ionic liquids can serve as efficient, biocompatible cosolvents for microbial electrochemical reduction of CO2 to value-added products, holding promise for more robust applications of MES.

Enhancing Electrochemical CO Reduction to Methane by Modulating the Interfacial Water Structure with Glycerol

Enhancing Electrochemical CO Reduction to Methane by Modulating the Interfacial Water Structure with Glycerol

Advances in Tandem Strategies for CO2 Electroreduction: From Electrocatalysts to Reaction System Design

AbstractThe electrochemical reduction of CO2 (CO2RR) offers the opportunity to store renewable energy in the form of chemicals and fuels while simultaneously reducing CO2 emissions. Compared to low carbon products such as carbon monoxide and formic acid, multicarbon products have demonstrated greater value in terms of economic feasibility. To date, various strategies have been developed to enhance electrocatalytic performance, with tandem strategies emerging as a promising approach, particularly for the formation of multicarbon products. In this review, current tandem strategies regarding CO2RR are thoroughly discussed, covering electrocatalyst designs from atomic‐scale tandem electrocatalysts to macroscale electrode configurations as well as reaction system designs. Additionally, the internal reaction processes involving reduction product upgrades, the application of multi‐physical tandem fields, and the tandem reaction systems are further summarized. This review aims to provide more fundamental insights into tandem strategies for CO2RR applications and inspire more creative ideas in the research community of CO2RR in light of this promising approach with its wide versatility, diversity, and flexibility.

Enhancing Internal Electric Field of Metal-Free Donor-Acceptor Conjugated Photocatalysts for Efficient Photocatalytic Degradation of Tetracycline and CO2 Reduction.

Constructing alternating donor-acceptor (D-A) units within g-C3N4 represents an effective strategy for enhancing photocatalytic performance through improved charge carrier separation while concurrently addressing energy shortages and facilitating wastewater remediation. Here, a series of D-A-type conjugated photocatalysts (CNBTC-X) are prepared using g-C3N4 as an acceptor unit and different masses of 5-bromo-2-thiophenecarboxaldehyde (BTC) as a donor unit by a one-step thermal polymerization. CNBTC-50 presents higher photocatalytic properties for CO2 reduction coupled with tetracycline (TC) removal than those of g-C3N4, CNBTC-10, CNBTC-30, and CNBTC-70. The introduction of the unique electron-donor-acceptor structure effectively drives the separation and transfer of photoinduced carriers while reducing the internal carrier transfer hindrance. Photocatalytic experiments reveal that the CNBTC-50 photocatalyst achieves up to 94.6% TC removal under visible light irradiation conditions. Compared with that of the pristine g-C3N4, the photocatalytic degradation reaction rate constant of CNBTC-50 is significantly increased by about 3.87 times. The study examines the influence of various reaction parameters on degradation activity, including catalyst concentration, pH, and TC concentration. Additionally, LC-MS is utilized to perform a comprehensive analysis of the intermediates and pathways involved in TC degradation. Furthermore, CNBTC-50 demonstrates remarkable photocatalytic CO2 reduction activity, achieving rates of 20.83 μmol g-1 h-1 (CO) and 9.36 μmol g-1 h-1 (CH4), which are 10.68 and 5.98 times more efficient than those of g-C3N4, respectively. This work aims to offer valuable guidance for the rational design of nonmetal D-A-structured catalysts and effectively integrates reaction systems to couple CO2 reduction with antibiotic removal.

Interface‐Engineering‐Induced C–C Coupling for C2H4 Photosynthesis from Atmospheric‐Concentration CO2 Reduction

Producing ethylene (C2H4) from carbon dioxide (CO2) photoreduction under mild conditions is primarily restricted by the difficulty of C−C coupling. Herein, we designed highly active metal atom clusters anchored on semiconductor nanosheet, which established heteroatom sites on the interface to steer C−C coupling, realizing air‐concentration CO2 photoreduction into C2H4 in pure water for the first time. As an example, the Pd nanoclusters loaded on ZnO nanosheets are prepared, demonstrated by the X‐ray photoelectron spectroscopy and high‐angle annular dark‐field image. In situ Fourier transform infrared spectroscopy confirms the C−C coupling step over the Pd‐ZnO nanosheets, while quasi in situ X‐ray photoelectron spectroscopy illustrates the active sites of Pd and Zn atoms on the Pd‐ZnO nanosheets during CO2 photoreduction. Density functional theoretical calculations unveil the transition state energy barrier of C–C coupling of CO* and COH* intermediates are only 0.998 eV, hinting the easy C–C coupling to produce C2 fuels. Therefore, the Pd‐ZnO nanosheets first realize C2H4 photosynthesis by atmospheric‐concentration CO2 reduction with the formation rate of 1.03 μmol g−1 h−1, while the ZnO nanosheets only acquired the carbon monoxide product.

Transforming carbon dioxide into a methanol surrogate using modular transition metal-free Zintl ions

Although not the only greenhouse gas, CO2 is the poster child. Unsurprisingly, therefore, there is global interest across industrial and academic research in its removal and subsequent valorisation, including to methanol and its surrogates. Although difficult to study, the heterogenous pnictogens represent one important category of catalytic materials for these conversions; their high crustal abundance and low cost offers advantages in terms of sustainability. Here, Zintl clusters based on these elements are studied as homogenous atom-precise models in CO2 reduction. A family of group 13 functionalized pnictogen clusters with the general formula [(R2E)Pn7]2– (E = B, Al, In; Pn = P, As) is synthesized and their catalytic competency in the reduction of CO2 probed. Trends in both turnover numbers and frequencies are compared across this series, and [(iBu2Al)P7]2– found to be very high-performing and recyclable. Electronic structures across the series are compared using density functional theory to provide mechanistic insights.

Pervasive fire danger continued under a negative emission scenario

Enhanced fire-prone weather under greenhouse gas warming can significantly affect local and global carbon budgets from increased fire occurrence, influencing carbon-climate feedbacks. However, the extent to which changes in fire-prone weather and associated carbon emissions can be mitigated by negative emissions remains uncertain. Here, we analyze fire weather responses in CO2 removal climate model experiments and estimate their potential carbon emissions based on an observational relationship between fire weather and fire-induced CO2 emissions. The results highlight that enhanced fire danger under global warming cannot be restored instantaneously by CO2 reduction, mainly due to atmospheric dryness maintained by climatic inertia. The exacerbated fire danger is projected to contribute to extra CO2 emissions in 68% of global regions due to the hysteresis of climate responses to CO2 levels. These findings highlight that even under global cooling from negative emissions, increased fire activity may reinforce the fire-carbon-climate feedback loop and result in further socio-economic damage.

Efficient photoreduction of CO2 to CO by Co-ZIL-L derived NiCo-OH with ultrathin nanosheet assembled 2D leaf superstructure.

The photocatalytic reduction of CO2 into valuable chemicals and fuels is considered a promising solution to address the energy crisis and environmental challenges. In this work, we introduce a Co-ZIL-L mediated in situ etching and integration process to prepare NiCo-OH with an ultrathin nanosheet-assembled 2D leaf-like superstructure (NiCo-OH UNLS). The resulting catalyst demonstrates excellent photocatalytic performance for CO2 reduction, achieving a CO evolution rate as high as 309.5 mmol g-1 h-1 with a selectivity of 91.0%. Systematic studies reveal that the ultrathin nanosheet structure and 2D leaf-like architecture not only enhance the transfer efficiency of photoexcited electrons but also improve the accessibility of active reaction sites. Additionally, the Ni-Co dual sites in NiCo-OH UNLS accelerate CO2 conversion kinetics by stabilizing the *COOH intermediate, significantly contributing to its high activity. This work offers valuable insights for designing advanced photocatalysts for CO2 conversion.

Why Including Solvation is Paramount: First-Principles Calculations of Electrochemical CO2 Reduction to CO on a Cu Electrocatalyst.

Electrochemical reduction reaction of CO2 (eCO2RR) to produce valuable chemicals offers an attractive strategy to solve energy and environmental problems simultaneously. We have mapped out entire reaction pathways of eCO2RR to CO on Cu(100), including all intermediates and transition states using first-principles simulations. To accurately account for the solvent effect, the reaction was investigated with and without explicit water molecules, highlighting the limitations of the often (mis)used vacuum reaction pathway simplification. The results show that the reduction reaction was initiated under neutral pH conditions at an applied potential of -0.11 V (RHE, reversible hydrogen electrode) and all elementary reactions were thermodynamically favorable, while an applied potential of -1.24 V is required to ensure that all reactions exhibit spontaneous behavior. Detailed analysis revealed that solvation significantly influences the stability of the adsorbates and intermediates. Its inclusion notably alters the calculated reaction kinetics and energetic parameters by lowering the barrier energies and Gibbs free energies of all reactions. CO production proceeded mainly via the COOH* pathway (CO2-->trans-COOH*-->cis-COOH*-->CO*+OH*-->CO*-->CO). The use of water as a more sustainable and cost-effective solvent is compared to other options such as organic solvents, ionic liquids and mixed solvent systems, which are less sustainable and more expensive.

Interface-Engineering-Induced C-C Coupling for C2H4 Photosynthesis from Atmospheric-Concentration CO2 Reduction.

Producing ethylene (C2H4) from carbon dioxide (CO2) photoreduction under mild conditions is primarily restricted by the difficulty of C-C coupling. Herein, we designed highly active metal atom clusters anchored on semiconductor nanosheet, which established heteroatom sites on the interface to steer C-C coupling, realizing air-concentration CO2 photoreduction into C2H4 in pure water for the first time. As an example, the Pd nanoclusters loaded on ZnO nanosheets are prepared, demonstrated by the X-ray photoelectron spectroscopy and high-angle annular dark-field image. In situ Fourier transform infrared spectroscopy confirms the C-C coupling step over the Pd-ZnO nanosheets, while quasi in situ X-ray photoelectron spectroscopy illustrates the active sites of Pd and Zn atoms on the Pd-ZnO nanosheets during CO2 photoreduction. Density functional theoretical calculations unveil the transition state energy barrier of C-C coupling of CO* and COH* intermediates are only 0.998 eV, hinting the easy C-C coupling to produce C2 fuels. Therefore, the Pd-ZnO nanosheets first realize C2H4 photosynthesis by atmospheric-concentration CO2 reduction with the formation rate of 1.03 μmol g-1 h-1, while the ZnO nanosheets only acquired the carbon monoxide product.

Copper Nanoclusters Imparted Metalloporphyrin Based Metal-Organic Frameworks for Enhanced CO2 Electroreduction.

Strategies that can introduce catalytic auxiliary into electrocatalysts to boost the performance of electrocatalytic CO2 reduction reaction (CO2RR) are meaningful in exploring hybrid electrocatalytic systems. Here, a series of hybrid electrocatalysts (Cu NCs@MOF-545-M, M=Fe, Co and Ni) have been prepared by assembly Cu NCs with MOF-545-M (M=Fe, Co and Ni) and successfully applied in electrocatalytic CO2RR. In the obtained MOF-545-M (M=Fe, Co and Ni), the integration of Cu NCs with MOF-545-M (M=Fe, Co and Ni) can create a hybrid electrocatalytic system that enhances the charge transfer efficiency and electrocatalytic CO2RR activity. Specifically, the optimal Cu NCs@MOF-545-Co presents remarkable FECO over a wide potential range (-0.7 V to -1.0 V), high CO generation rate (8.2 mol m-2 h-1) and excellent maximum energy efficiency (69 %, -0.7 V), which is superior to Cu NCs and MOF-545-Co, and represented to be one of the best performances to date. This work demonstrates a facile approach to significantly improve the FECO by loading metal nanoclusters into MOFs, providing a valuable reference for future studies on hybridization strategies to enhance the performance of electrocatalysts.

Near‐Infrared Light‐Driven CO2 Reduction on Cup‐Stacked Carbon Nanotubes

AbstractCarbon nanotubes feature one‐dimensional nature of collective excitations, wherein strong confinement of surface plasmons severely hinders the liberation of hot electrons (HEs), posing grand challenges for their utilization in photochemistry. In this study, we prototypically achieved directed HEs flow and extraction in hybrid plasmonic CNN based on cup‐stacked carbon nanotubes (CSCNTs), taking advantage of their privileged edge‐plane sites. The localized pz electronic states and accessible intersubband plasmon excitations in the near‐infrared (NIR) regime stands in striking contrast to the conventional concentric carbon nanotubes, as evidenced by combined photo‐induced force microscopy (PiFM) and transient photocurrent response. The hybrid comprising intimately integrated CSCNTs‐C3N4 effectively sustains interfacial electronic states and underlies the energy extraction out of plasmonic components. The CNN demonstrates almost near‐unity NIR light‐driven CO2 reduction to CO with a rate of 1.35 μmol g−1 h−1. This work sheds light on the exploitation of metal‐free carbon‐based plasmonic nanostructures for photocatalytic applications.

Strategies for Achieving Carbon Neutrality: Dual-Atom Catalysts in Focus.

Carbon neutrality is a fundamental strategy for achieving the sustainable development of human society. Catalyzing CO2 reduction into various high-value-added fuels serves as an effective pathway to achieve this strategic objective. Atom-dispersed catalysts have received extensive attention due to their maximum atomic utilization, high catalytic selectivity, and exceptional catalytic performance. Dual-atom catalysts (DACs), as an extension of single-atom catalysts (SACs), not only retain the advantages of SACs, but also produce many new properties. This review initiates its exploration by elucidating the mechanism of CO2 reduction reaction (CO2RR) from CO2 adsorption and CO2 activation. Then, a comprehensive summary of recently developed preparation methods of DACs is presented. Importantly, the mechanisms underlying the promoted catalytic performance of DACs in comparison to SACs are subjected to a comprehensive analysis from adjustable adsorption capacity, tunable electronic structure, strong synergistic effect, and enhanced spacing effect, elucidating their respective superiorities in CO2RR. Subsequently, the application of DACs in CO2RR is discussed in detail. Conclusively, the prospective trajectories and inherent challenges of CO2RR are expounded upon concerning the continued advancement of DACs. This thorough review not only enhances the comprehension of DACs within CO2RR but also accentuates the prospective developments in the design of sophisticated catalytic materials.

Controlling the Phase Composition of Pre-Catalysts to Obtain Abundant Cu(111)/Cu(200) Grain Boundaries for Enhancing Electrocatalytic CO2 Reduction Selectivity to Ethylene.

The preparation of ethylene (C2H4) by electrochemical CO2 reduction (ECO2R) has dramatically progressed in recent years. However, the slow kinetics of carbon-carbon (C-C) coupling remains a significant challenge. A generalized facet reconstruction strategy is reported to prepare a 3-phase mixed pre-catalyst (Cu3N-300) of Cu3N, Cu2O, and CuO by controlling the calcination temperature and to obtain the derived Cu catalyst (A-Cu3N-300-0.5) enriched with Cu(111)/Cu(200) grain boundaries (GBs) by subsequent constant potential reduction. Its Faraday efficiency (FE) toward C2H4 at a low reaction potential of -1.07V (vs reversible hydrogen electrode (RHE)) is 46.03%, which is much higher than the other 3 derived Cu catalysts containing single Cu(111) facets (24.89% and 24.52%) and Cu(111)/Cu(111) GBs (28.66%). Combining in situ experimental and theoretical computational studies, abundant Cu(111)/Cu(200) GBs is found to enhance CO2 activation and significantly promote the formation and adsorption of *CO intermediates, thereby lowering the activation energy barrier of C-C coupling and increasing the FE of C2H4.

Specific Adsorption of Alkaline Cations Enhances CO-CO Coupling in CO2 Electroreduction.

Electrolyte alkaline cations can significantly modulate the reaction selectivity of electrochemical CO2 reduction (eCO2R), enhancing the yield of the valuable multicarbon (C2+) chemical feedstocks. However, the mechanism underlying this cation effect on the C-C coupling remains unclear. Herein, by performing constant-potential AIMD simulations, we studied the dynamic behavior of interfacial K+ ions over Cu surfaces during C-C coupling and the origin of the cation effect. We showed that the specific adsorption of K+ readily occurs at the surface sites adjacent to the *CO intermediates on the Cu surfaces. Furthermore, this specific adsorption of K+ during *CO-*CO coupling is more important than quasi-specific adsorption for enhancing coupling kinetics, reducing the coupling barriers by approximately 0.20 eV. Electronic structure analysis revealed that charge redistribution occurs between the specifically adsorbed K+, *CO, and Cu sites, and this can account for the reduced barriers. In addition, we identified excellent *CO-*CO coupling selectivity on Cu(100) with K+ ions. Experimental results show that suppressing surface K+-specific adsorption using the surfactant cetyltrimethylammonium bromide (CTAB) significantly decreases the Faradaic efficiency for C2 products from 41.1% to 4.3%, consistent with our computational findings. This study provides crucial insights for improving the selectivity toward C2+ products by rationally tuning interfacial cation adsorption during eCO2R. Specifically, C-C coupling can be enhanced by promoting K+-specific adsorption, for example, by confining K+ within a coated layer or using pulsed negative potentials.