Oxophilicity-Controlled CO2 Electroreduction to C2+ Alcohols over Lewis Acid Metal-Doped Cuδ+ Catalysts

Electrocatalytic conversion of 5-hydroxymethylfurfural to 5-methyl-2-furanmethanol by delocalization state-tuned bond cleavage

The electrocatalytic conversion of 5-hydroxymethylfurfural (HMF) represents a green strategy for valorizing biomass-derived platform molecules into renewable fuels and value-added chemicals. However, most current electrocatalysts focus on reducing HMF to 2,5-furandimethanol (BHMF), while the selective reduction of HMF into 5-methyl-2-furanmethanol (MFA) in neutral electrolytes has received much less progress. In this work, we developed a Cu3Ge intermetallic catalyst to modulate the electronic properties of Cu. Compared to pure Cu with the BHMF selectivity, the introduction of Ge atoms enhances the electron localization on the Cu lattice, facilitating the preferential CO bond cleavage and promoting the selective formation of MFA. The Cu3Ge catalyst demonstrated an enhanced MFA selectivity of 27% ± 4%, suggesting a potential strategy for tuning electrocatalyst properties to achieve different reduction products.

Low-Coordination Triangular Cu3 Motif Steers CO2 Photoreduction to Ethanol

Photoreduction of CO2 using copper-based multi-atom catalysts (MACs) offers a potential approach to achieve value-added C2+ products. However, achieving MACs with high metal contents and suppressing the thermodynamically favored competing ethylene production pathway remain challenging, thus leading to unsatisfactory performance in ethanol production. Herein, we developed a "pre-locking and nanoconfined polymerization" strategy for synthesis of an ultra-high-density Cu MAC with low-coordination triangular Cu3 motifs (Cu3 MAC) on polymeric carbon nitride mesoporous nanofibers. The Cu3 MAC with Cu contents of 36 wt% achieves a high reactivity of 117 µmol g-1 h-1 for ethanol production from CO2 and H2O, with a remarkable selectivity of 98% under simulated sunlight irradiation, representing one of the highest performances in ambient conditions without sacrificial reagents. The superior catalytic efficiency is attributed to the triangular Cu3 configuration, in which both Cu(I) and Cu(II) coexist, predominantly as Cu(I). Such Cu3 motifs act as strong alkaline sites that effectively chemisorb and activate CO2, extend visible-light absorption range, while accumulating high-density electrons and favoring 12-electron-transfer products. An accelerated asymmetric C─C coupling with adsorption configuration of the bridge-adsorbed *CO at paired Cu sites and atop-adsorbed *CO at adjacent single Cu atom was observed, enabling preferential formation of *CHCHOH intermediates to produce ethanol.

Interfacial Metal Oxides Stabilize Cu Oxidation States for Electrocatalytical CO2 Reduction

Modulating the oxidation state of copper (Cu) is crucial for enhancing the electrocatalytic CO2 reduction reaction (CO2RR), particularly for facilitating deep reductions to produce methane (CH4) or multi-carbon (C2+) products. However, Cuδ+ sites are thermodynamically unstable, fluctuating their oxidation states under reaction conditions, which complicates their functionality. Incorporating interfacial metal oxides has emerged as an effective strategy for stabilizing these oxidation states. This review provides an in-depth examination of the reaction mechanisms occurring at oxide-modified Cuδ+ sites, offering a comprehensive understanding of their behavior. We explore how Cu/metal oxide interfaces stabilize Cu oxidation states, showing that oxides-modified Cu catalysts often enhance selectivity for C2+ or CH4 products by stabilizing Cu+ or Cu2+ sites. In addition, we discuss innovative strategies for the rational design of efficient Cu catalytic sites tailored for specific deep CO2RR products. The review concludes with an outlook on current challenges and future directions, offering new insights into the rational design of selective and efficient CO2RR catalysts.

Boosting Urea Electrosynthesis via Asymmetric Oxygen Vacancies in Zn-Doped Fe2O3 Catalysts

Urea electrosynthesis from CO2 and nitrate (NO3 -) provides an attractive pathway for storing renewable electricity and substituting traditional energy-intensive urea synthesis technology. However, the kinetics mismatching between CO2 reduction and NO3 - reduction, as well as the difficulty of C─N coupling, are major challenges in urea electrosynthesis. Herein, we first calculated the free energy of *CO, *OCNO, and *NOH formation over defect-rich Fe2O3 catalysts with different metal dopants, which showed that Zn dopant was a promising candidate. Based on the theoretical study, we developed Zn-doped defect-rich Fe2O3 catalysts (Zn-Fe2O3/OV) containing asymmetric Zn-OV-Fe sites. It exhibited an outstanding urea faradaic efficiency of 62.4% and the remarkable recycling stability. The production rate of urea was as high as 7.48 mg h-1 mgcat -1, which is higher than most of the reported works to date. Detailed control experiments and in situ spectroscopy analyses identified *OCNO as a crucial intermediate for C─N coupling. The Zn-Fe2O3/OV catalyst with asymmetric Zn-OV-Fe sites showed enhanced *CO coverage and promoted *OCNO formation, leading to high efficiency toward urea production.

Rational Construction of Cu Active Sites for CO2 Electrolysis to C2+ Product

Electrocatalytic CO2 reduction reaction (CO2RR) has emerged as a promising approach in advancing towards carbon neutrality and addressing renewable energy intermittency. Copper-based catalysts have received much attention due to their high catalytic activity to convert CO2 into high value-added C2+ products. However, CO2RR exhibits a diversity of reduction products and unavoidable hydrogen precipitation side reactions due to the moderate adsorption strength of *CO on the copper surface and the fact that the electrode potential for CO2 reduction is very close to that for hydrogen precipitation reduction. Here, we summarize recent advances in the structural design and active site construction of copper-based catalysts for CO2RR, and investigate their effects on the improvement of CO2RR performance, with the aim of deepening the understanding of catalyst structure and active sites, thereby facilitating the design of more efficient copper-based catalysts for the sustainable production of value-added chemicals.

Ultrathin Palladium-loaded Cuprous oxide stabilises Copper(I) to facilitate electrochemical carbon dioxide reduction reaction

Cuprous oxide (Cu2O) exhibit significant potential for catalytic activity in the electrochemical carbon dioxide reduction reaction (CO2RR). However, the rapid reduction of Copper(I) (Cu+) to metallic Copper (Cu) leads to catalyst deactivation, significantly impacting product selectivity and stability. This study aims to stabilize the Cu+ valence state at a metal-Cu2O heterogeneous interface through interfacial engineering, ultimately enhancing the electrochemical CO2 reduction performance of Cu2O. Utilizing comprehensive in situ Raman spectroscopy, we observed that the addition of Palladium (Pd) effectively inhibited the reduction of Cu2O. Additionally, combined in situ attenuated total reflection Fourier-transform infrared spectroscopy and theoretical calculations revealed that Pd loading enhances *CO intermediate concentration and adsorption energy, and reduces the energy barrier for *CHO formation. The improved stability of the Cu+ valence state led to the coexistence of two CO adsorption modes including COatop and CObridge, promoting further CO hydrogenation and C-C coupling. Consequently, the Pd-loaded Cu2O catalyst demonstrated remarkable electrochemical CO2RR performance, achieving a methanol (CH3OH) Faradaic efficiency of 78 %.

Electrocatalytic CO2 Reduction to C2 Products via Enhanced C─C Coupling Over Cu-based Catalysts: Dynamic Reaction and Regulation Mechanism

Benefiting from the optimal interaction strength between Cu and reactants, Cu-based catalysts exhibit a unique capability of facilitating the formation of various multi-carbon products in electricity-driven CO2 reduction reactions (CO2ERR). Nonetheless, the CO2ERR process on these catalysts is characterized by intricate polyproton-electron transfer mechanisms that are frequently hindered by high energy barriers, sluggish reaction kinetics, and low C─C coupling efficiency. This review employs advanced characterization techniques, such as sum frequency generation technology, to provide a comprehensive analysis of the CO2ERR mechanism on the Cu surface, examining it from both spatial and temporal dimensions and proposing a spatial-temporal coupling reaction mechanism. To improve C─C coupling efficiency, a series of regulatory strategies are focused on surface microenvironment, catalyst surface structure, and internal electronic structure, thereby offering novel insights for the upcoming design and enhancement of Cu-based electrocatalysts.

Supercritical CO2 Activation Enables an Exceptional Methanol Synthesis Activity Over the Industrial Cu/ZnO/Al2O3 Catalyst

The ternary Cu/ZnO/Al2O3 catalyst is widely used in the industry for renewable methanol synthesis. The tenuous trade-off between the strong metal-support interaction (SMSI)-induced Cu-ZnOx interface and the accessible Cu surface strongly affects the activity of the final catalyst. Successes in the control of oxide migration on adsorbate-induced SMSI catalysts have motivated this to develop a supercritical CO2 activation strategy to synchronously perfect the Cu0-O-Znδ + interface and Cu0-Cu+ surface sites through the manipulation of the adsorbate diffusion kinetics, which involves *OC2H5 and "side-on" fixed CO2 species. This findings illustrate that the adsorbate on ZnOx can facilitate its secondary uniform nucleation and induce a ZnxAl2Oy spinel phase and that CO2 adsorption on metallic Cu0 produces an activated CuxO amorphous shell. Such a structural evolution unlocks a dual-response pathway in methanol synthesis, thus enabling Cu/ZnO/Al2O3 with a twofold increase in catalytic activity. This atomic-level design of active sites and understanding of supercritical CO2-induced structural evolution will guide the future development of high-performance supported metal catalysts.

Functional Group Engineering of Single-Walled Carbon Nanotubes for Anchoring Copper Nanoparticles Toward Selective CO2 Electroreduction to C2 Products

Electroreduction of carbon dioxide (CO2) is a key strategy for achieving net-zero carbon emissions. Copper (Cu)-based electrocatalysts have shown promise for CO2 conversion into valuable chemicals but are hindered by limited C2+ product selectivity due to competing hydrogen evolution and ineffective dimerization of adsorbed CO intermediate (*CO). Here, a functional-group-directed strategy is reported to enhance selectivity using single-walled carbon nanotubes (SWCNTs) as supports. The catalytic performance of Cu nanoparticles is strongly influenced by the type and density of functional groups on the SWCNTs. Optimized Cu/amine-functionalized SWCNTs achieved a Faradaic efficiency of 66.2% and a partial current density of -270 mA cm-2 for C2 products within a flow cell, outperforming Cu/SWCNTs and Cu/cyano-functionalized SWCNTs. Density functional theory calculations revealed that the electron-donating amine groups can facilitate electron transfer from the graphite sheet to Cu atoms, thereby shifting the d-band center of Cu upward. This shift enhances *CO and its hydrogenation derivative adsorption and promotes water splitting, leading to an increased tendency for the generation of C2 products. In situ infrared and Raman spectroscopy confirm the enhancement of key *CHO intermediate coverage, facilitating C─C coupling. This work provides a molecular framework for exploring interactions between functional groups and active metals in CO2 electrolysis, offering insights for designing catalysts for a broad range of electrocatalytic processes.

Internal lattice oxygen sites invert product selectivity in electrocatalytic alkyne hydrogenation over copper catalysts

Copper-based catalysts exhibit excellent performance of electrocatalytic alkynes hydrogenation, especially for the selective alkynes hydrogenation toward alkenes. However, the selective electrocatalytic alkynes hydrogenation toward alkanes is hard to achieve over copper-based catalysts because electron-rich Cu0 sites are unable to adsorb and activate nucleophilic alkenes. Herein, we report a metallic copper catalyst containing internal lattice oxygen atoms for steering the selectivity of alkynes hydrogenation toward alkanes. Internal lattice oxygen atoms protect Cuδ+ sites from being reduced during electrocatalytic alkynes hydrogenation so that alkenes intermediates can continually be adsorbed and converted to alkanes on stable Cuδ+ sites. Due to the synergy between Cu0 and Cuδ+ sites, metallic copper electrocatalyst containing internal lattice oxygen atoms shows an excellent selectivity for selective alkynes hydrogenation toward alkanes (2-methyl-3-butan-2-ol selectivity of 94.9%). This work opens a avenue for steering the selective alkynes hydrogenation, and more importantly, it fills in a gap on the selective electrocatalytic alkynes hydrogenation toward alkanes over copper-based catalysts.

Polymer-Halogen Pockets Steering *CO Adsorption Configurations for Highly Selective CO2 Electroreduction

The selective CO2 electroreduction (CO2R) toward specific C2 products represents a critical challenge for practical applicability, requiring precise control over *CO intermediates. Herein, a "polymer-halogen" pocketed Cu catalyst is proposed, wherein the adjustable concentration of Iodide ion (I-) within the pocket enables continuous modulation of *CO adsorption configurations on the Cu, thereby enabling tailored CO2R toward ethylene or ethanol production. A perfluorosulfonic acid (PFSA)-modified CuI catalyst is constructed, where I- is in situ leaching from CuI and subsequently confined by PFSA as an anion shielding layer to form polymer-halogen pockets. By tuning the thickness of PFSA shell, the amount of I- in the pocket can be controlled. The surface-enhanced in situ Raman spectroscopy demonstrates that the coverage of *CO intermediates on Cu surface increases and tends to adsorb at low coordination Cu sites in catalyst granule for dimerization reaction as the I- concentration in the pocket increases. Furthermore, the coordination environment exhibits distinct product selectivity. *CO at medium-coordinated sites favor ethanol production, while those at low-coordinated sites are conducive to ethylene formation. This strategy enables wide modulation of ethylene-to-ethanol ratios from 0.65 to 3.96, achieving peak Faradaic efficiencies (FE) of 60.3 ± 2.1% for ethylene and 48.3 ± 1.3% for ethanol.

Enhancing carbon enrichment by metal-organic cage to improve the electrocatalytic carbon dioxide reduction performance of silver-based catalyst

Electrochemical reduction of carbon dioxide (CO2) into value-added chemicals provide an alternative technology for achieving carbon neutrality. Limited mass transfer of CO2 in aqueous electrolyte and unsatisfied catalytic activity are the major determinants that inhibit the CO2 conversion at industrial current density level. Herein, an electroreduction-generated metallic Ag atomic clusters supported on metal organic cage (Ag AC/MOC) electrocatalyst is reported to improve the enrichment of inorganic carbon species over catalytic sites for efficient CO2 electroreduction. In-situ infrared spectroscopy and density functional theory studies reveal that the Ag AC/MOC induces the CO2-concentrating in the metal organic cage via a spontaneous ionization of the accumulated CO2, which dramatically enhances the coverage of inorganic carbon species for accelerated kinetic of CO2 conversion. The highly dispersed Ag atomic clusters further reduce the activation energy of CO2 and promote the protonation of CO2 to form carboxyl species, enabling high selectivity toward CO. Hence, the Ag AC/MOC achieves a high CO faradaic efficiency of 97.0 %, while the highest CO partial current reaches 231.6 mA cm-2, which is significantly higher than that of metallic Ag electrocatalyst. This work demonstrates a deep insight into high-performance electrocatalyst design in view of CO2 transfer and catalytic activity.

Constructing atomically dispersed Ni-Mn catalysts for electrochemical CO2 reduction over the wide potential window

Single-atom catalysts (SACs), known for their high atomic utilization efficiency, are highly attractive for electrochemical CO2 conversion. Nevertheless, it is struggling to use a single active site to overcome the linear scaling relationship among intermediates. Herein, an isolated diatomic Ni-Mn dual-sites catalyst was anchored on nitrogenated carbon, which exhibits remarkable electrocatalytic performance towards CO2 reduction. The catalyst achieves CO Faradaic efficiency (FECO) over 90 % within the potential range of -0.6 to -1.4 V vs. reversible hydrogen electrode (RHE), and a nearly 100 % FECO at a current density of 325 mA cm-2 in the flow cell. The Ni-Mn-NC also exhibits long-term stability, maintaining FECO above 96 % for over 14 h. The density functional theory (DFT) studies further reveal that the synergistic effect of adjacent Ni-Mn centers effectively reduces the reaction barriers for the formation of *COOH and thus accelerates the reduction of CO2.

Optimizing C─C Coupling on Cu0/Cu+/Ga Interfaces by Enhancing Active Hydrogen Absorption for Excellent CO2-to-C2+ Electrosynthesis

The electrocatalytic reduction of CO2 (CO2RR) to high-value chemicals and fuels offers a promising route for a clean carbon cycle. However, it often suffers from low catalytic activity and poor selectivity. Heterostructure construction has been shown to be an effective strategy for producing multi-carbon products, but the synergistic mechanisms between multiple active sites resulting from the reconstruction process remain unclear. In this study, a Ga2O3/CuO heterostructure is established via a simple sol-gel method to produce C2+ products. Experimental results demonstrate that Ga2O3 stabilizes Cu+ to form Cu0/Cu+/Ga active centers and enhances water-splitting ability during the reaction. The improved hydrogen absorption on the Ga site shifts the C─C coupling reaction pathway from *OCCO to the asymmetric *OCCHO coupling path with a lower energy barrier. As a result, the catalysts exhibit superior CO2RR performance, achieving a 70.1% C2+ Faradaic efficiency at -1.2 VRHE in a flow cell, with ethylene Faradaic efficiency reaching 58.3% and remaining stable for 10 h.

Progress in Cu-Based Catalyst Design for Sustained Electrocatalytic CO2 to C2+ Conversion

The electrocatalytic conversion of CO2 into valuable multi-carbon (C2+) products using Cu-based catalysts has attracted significant attention. This review provides a comprehensive overview of recent advances in Cu-based catalyst design to improve C2+ selectivity and operational stability. It begins with an analysis of the fundamental reaction pathways for C2+ formation, encompassing both established and emerging mechanisms, which offer critical insights for catalyst design. In situ techniques, essential for validating these pathways by real-time observation of intermediates and material evolution, are also introduced. A key focus of this review is placed on how to enhance C2+ selectivity through intermediates manipulation, particularly emphasizing catalytic site construction to promote C─C coupling via increasing *CO coverage and optimizing protonation. Additionally, the challenge of maintaining catalytic activity under reaction conditions is discussed, highlighting the reduction of active charged Cu species and materials reconstruction as major obstacles. To address these, the review describes recent strategies to preserve active sites and control materials evolution, including novel catalyst design and the utilization and mitigation of reconstruction. By presenting these developments and the challenges ahead, this review aims to guide future materials design for CO2 conversion.

Electrochemical CO2 Reduction in Acidic Media: A Perspective

The electrochemical CO2 reduction reaction (eCO2RR) is a promising approach for converting CO2 to useful chemicals and, hence, achieving carbon neutrality. Though high selectivity and activity of products have been achieved recently, all are reported in neutral or alkaline electrolytes. Although these electrolyte media give high selectivity and activity, they face the major challenge of low CO2 utilization because of carbonate formation, which lowers the overall efficiency of the process. Conducting the eCO2RR in acidic media can help overcome the issue of carbonate formation and hence can increase the CO2 utilization efficiency. However, there are many challenges associated with acidic eCO2RR. Two major concerns are the highly competitive hydrogen evolution reaction in acidic media and salt precipitation issues. This Perspective focuses on the fundamentals of acidic eCO2RR, recent catalyst development strategies, and relevant problems that need to be addressed in the future. In the end, we provide a future outlook that will give an idea about the problems to focus on in the future in the field of acidic eCO2RR.

Marked CO2 Reduction to Generate C1-C3 Products Using Pt0.9Ru0.1/C-Based Membrane Electrode Assembly at Extremely Low Overpotentials

The electrochemical CO2 reduction reaction (CO2RR) over Pt electrocatalysts in an aqueous solution system yields mainly H2 and a slight amount of carbon-based products. This limitation can be overcome by using a membrane electrode assembly (MEA) containing a Pt/C electrocatalyst without any overpotential. However, the obtained CO2RR product was only CH4. In this study, we investigated the CO2RR using MEA containing a Pt0.9Ru0.1/C electrocatalyst. Consequently, not only methane as a C1 product but also ethanol as a C2 product and acetone as a C3 product were produced at extremely small overpotentials. This is the first time in the literature that ethanol and acetone were produced from the CO2RR over a Pt-Ru-based electrocatalyst. This fact was confirmed through mass spectrometry, gas chromatography, and isotope labeling experiments. The Faradaic efficiencies of CH4, C2H5OH, and CH3COCH3 were 20.6%, 5.9%, and 5.2%, respectively, and the total Faradaic efficiency was 31.7%. The three products were generated via the Langmuir-Hinshelwood mechanism involving adsorbed CO (COads) and H atoms on the electrocatalyst. The adsorption configuration of COads determines the generation of methane, ethanol, and acetone. The C-C coupling reactions occurred through the formation of COads clusters. Our findings promote the production of valuable C2+ compounds from the CO2RR, which is an important CO2 capture, utilization, and storage technology for realizing carbon neutrality.

Fluorine Doping-Assisted Reconstruction of Isolated Cu Sites for CO2 Electroreduction Toward Multicarbon Products

The electrocatalytic synthesis of multicarbon compounds from CO2 is a promising method for storing renewable electricity and addressing global CO2 issues. Single-atom catalysts are promising candidates for CO2 reduction, but producing high-value multicarbon (C2+) products using a single-atom structure remains a significant challenge. In this study, a fluorine doping strategy is proposed to facilitate the reconstruction of isolated Cu atoms, promoting multicarbon generation. The in situ formed Cu nanocrystals contain a substantial amount of stable Cu+ species, demonstrating remarkable activity for CO2-to-multicarbon conversion. Notably, they achieve the highest Cu utilization, with a C2+ partial current density of -2.01 A mgper Cu -1and a C2+ formation rate of 7.03 mmol h-1 mgper Cu -1at ≈-1 V versus RHE. In situ Raman spectroscopy and density functional theory calculations confirm the crucial role of fluorine atoms in structural evolution and electrolysis.

Electronic metal-support interaction modulates Cu electronic structures for CO2 electroreduction to desired products

In this work, the Cu single-atom catalysts (SACs) supported by metal-oxides (Al2O3-CuSAC, CeO2-CuSAC, and TiO2-CuSAC) are used as theoretical models to explore the correlations between electronic structures and CO2RR performances. For these catalysts, the electronic metal-support interaction (EMSI) induced by charge transfer between Cu sites and supports subtly modulates the Cu electronic structure to form different highest occupied-orbital. The highest occupied 3dyz orbital of Al2O3-CuSAC enhances the adsorption strength of CO and weakens C-O bonds through 3dyz-π* electron back-donation. This reduces the energy barrier for C-C coupling, thereby promoting multicarbon formation on Al2O3-CuSAC. The highest occupied 3dz2 orbital of TiO2-CuSAC accelerates the H2O activation, and lowers the reaction energy for forming CH4. This over activated H2O, in turn, intensifies competing hydrogen evolution reaction (HER), which hinders the high-selectivity production of CH4 on TiO2-CuSAC. CeO2-CuSAC with highest occupied 3dx2-y2 orbital promotes CO2 activation and its localized electronic state inhibits C-C coupling. The moderate water activity of CeO2-CuSAC facilitates *CO deep hydrogenation without excessively activating HER. Hence, CeO2-CuSAC exhibits the highest CH4 Faradaic efficiency of 70.3% at 400 mA cm-2.

Enhancing CO2 Electroreduction to Multicarbon Products by Modulating the Surface Microenvironment of Electrode with Polyethylene Glycol

Modulating the surface microenvironment of electrodes stands as a pivotal aspect in enhancing the electrocatalytic performance for CO2 electroreduction. Herein, we propose an innovative approach by incorporating a small amount of linear oligomer, polyethylene glycol (PEG), into Cu2O catalysts during the preparation of the CuPEG electrode. The Faradaic efficiency (FE) toward multicarbon products (C2+) increases from 69.3 % over Cu electrode without PEG to 90.3 % over CuPEG electrode at 500 mA cm-2 in 1 M KOH in a flow cell. In situ investigations and theoretical calculations reveal that PEG molecules significantly modify the microenvironment on the Cu surface through hydrogen bond interactions. This modification leads to the relaxation of Nafion, increasing the availability of active sites and enhancing the adsorption of *CO and *OH, which in turn promotes C-C coupling. Concurrently, the reconstructed hydrogen bond network reduces the presence of active hydrogen species, thereby inhibiting the hydrogen evolution reaction.

Polymeric ionic liquid promotes acidic electrocatalytic CO2 conversion to multicarbon products with ampere level current on Cu

The acidic electroreduction of CO2 into multicarbon (C2+) products is much attractive for the improved carbon utilization than alkaline or neutral electroreduction. How to improve the efficiency of C2+ products generation by acidic electroreduction of CO2, is important, especially at high current density and in electrolyte with low K+ concentration. Herein, we propose a strategy of capping Cu surface with a polymeric ionic liquid (PIL) adlayer for boosting the acidic electrocatalytic CO2 conversion to C2+ products at high current densities (ampere-level) and low K+ concentration. In the electrolyte with a relatively low K+ concentration (1.0 M), the Faradaic efficiency (FE) for C2+ products reaches 82.2% under a current density 1.0 A·cm-2 in acidic environment (pH=1.8). Particularly, when the current density is as high as 1.5 A·cm-2, the C2+ FE still keeps 75.8%. Experimental and theoretical studies reveal that the presence of PIL adlayer on Cu catalyst can well inhibit H+ diffusion to catalyst surface, enrich more K+ and facilitate C-C coupling reaction.

Cuδ+ Site-Enhanced Adsorption and Crown Ether-Reconfigured Interfacial D2O Promote Electrocatalytic Dehalogenative Deuteration

Electrocatalytic dehalogenative deuteration is a sustainable method for precise deuteration, whereas its Faradaic efficiency (FE) is limited by a high overpotential and severe D2 evolution reaction (DER). Here, Cuδ+ site-adjusted adsorption and crown ether-reconfigured interfacial D2O are reported to cooperatively increase the FE of dehalogenative deuteration up to 84% at -100 mA cm-2. Cuδ+ sites strengthen the adsorption of aryl iodides, promoting interfacial mass transfer and thus accelerating the kinetics toward dehalogenative deuteration. The crown ethers disrupt the hydration effect of K·D2O and reconstruct the hydrogen bond with the interfacial D2O, lowering the content K·D2O of the electric double layer and hindering the interaction between D2O and the cathode, thus inhibiting the kinetics of the competitive DER. A linear relationship between the matched sizes of crown ethers and alkali metal cations is demonstrated for universally increasing FEs. This method is also suitable for the deuteration of various halides with high easily reducible functional group compatibility and improved FEs at -100 mA cm-2.

Steering the Absorption Configuration of Intermediates over Pd-Based Electrocatalysts toward Efficient and Stable CO2 Reduction

Palladium (Pd) catalysts are promising for electrochemical reduction of CO2 to CO but often can be deactivated by poisoning owing to the strong affinity of *CO on Pd sites. Theoretical investigations reveal that different configurations of *CO endow specific adsorption energies, thereby dictating the final performances. Here, a regulatory strategy toward *CO absorption configurations is proposed to alleviate CO poisoning by simultaneously incorporating Cu and Zn atoms into ultrathin Pd nanosheets (NSs). As-prepared PdCuZn NSs can catalyze CO production at a wide potential window (-0.28 to -0.78 V vs RHE) and achieve a maximum FECO of 96% at -0.35 V. Impressively, it exhibits stable CO production of 100 h under ∼95% FECO with no decay. Combined results from X-ray analysis, in situ spectroscopy, and theoretical simulations suggest that the codoping strategy not only optimizes the electronic structure of Pd but also weakens the binding strengths of *CO and increases the proportion of weak-binding linear *CO absorption configuration on catalysts' surfaces. Such targeted adoption of weakly bound configurations abates the energy barrier of *CO desorption and facilitates CO production. This work confers a useful design tactic toward Pd-based electrocatalysts, codoping for steering adsorption configuration to achieve highly selective and stable CO2-to-CO conversion.

Regulating Interfacial Hydrogen-Bonding Networks by Implanting Cu Sites with Perfluorooctane to Accelerate CO2 Electroreduction to Ethanol

Efficient CO2 electroreduction (CO2RR) to ethanol holds promise to generate value-added chemicals and harness renewable energy simultaneously. Yet, it remains an ongoing challenge due to the competition with thermodynamically more preferred ethylene production. Herein, we presented a CO2 reduction predilection switch from ethylene to ethanol (ethanol-to-ethylene ratio of ~5.4) by inherently implanting Cu sites with perfluorooctane to create interfacial noncovalent interactions. The 1.83 %F-Cu2O organic-inorganic hybrids (OIHs) exhibited an extraordinary ethanol faradaic efficiency (FEethanol) of ∼55.2 %, with an impressive ethanol partial current density of 166 mA cm-2 and excellent robustness over 60 hours of continuous operation. This exceptional performance ranks our 1.83 %F-Cu2O OIHs among the best-performing ethanol-oriented CO2RR electrocatalysts. Our findings identified that C8F18 could strengthen the interfacial hydrogen bonding connectivity, which consequently promotes the generation of active hydrogen species and preferentially favors the hydrogenation of *CHCOH to *CHCHOH, thus switching the reaction from ethylene-preferred to ethanol-oriented. The presented investigations highlight opportunities for using noncovalent interactions to tune the selectivity of CO2 electroreduction to ethanol, bringing it closer to practical implementation requirements.

Cu-ZnS Modulated Multi-Carbon Coupling Enables High Selectivity Photoreduction CO2 to CH3CH2COOH

The direct photocatalytic conversion of CO2 and H2O into high-value C3 chemicals holds great promise but remains challenging due to the intrinsic difficulty of C1-C1 and C2-C1 coupling processes and the lack of clarity regarding the underlying reaction mechanisms. Here, the design and synthesis of a Cu-ZnS photocatalyst featuring dispersed Cu single atoms are reported. These Cu single atoms are coordinated with S atoms, forming unique Cu-S-Zn active units with tunable charge distributions that interact favorably with surface-adsorbed intermediates. This configuration stabilizes the *COHCO intermediate and facilitates its subsequent coupling with *CO to form *COCOHCO both thermodynamically and kinetically favorable on the Cu-ZnS surface. Notably, multiple critical C3 intermediates, including *COCOHCO, *OCCCO, and *CHCHCO, are identified, providing a clear reaction pathway for CO2 to CH3CH2COOH conversion. The Cu-ZnS photocatalyst achieves a CO2 to CH3CH2COOH conversion rate of 0.45 µmol h-¹ with an electron selectivity of 91.2%. Remarkably, in the presence of triethanolamine, the production rate increases to 16.9 µmol h-¹ with a selectivity of 99.8%. These findings underscore the importance of modulating multicarbon coupling processes to enable the efficient photocatalytic transformation of CO2 into C3 products, paving the way for future advancements in sustainable chemical synthesis.

Metal-organic framework-derived silver/copper-oxide catalyst for boosting the productivity of carbon dioxide electrocatalysis to ethylene

Electrochemical reduction of CO2 into valuable multi-carbon (C2) chemicals holds promise for mitigating CO2 emissions and enabling artificial carbon cycling. However, achieving high selectivity remains challenging due to the limited activity and active sites of CC coupling catalysts. Herein, we report an Ag-modified Cu-oxide catalyst (CuO/Ag@C) derived from metal-organic frameworks (MOF), capable of efficiently converting CO2 to C2H4. The MOF-derived porous carbon confines the size of metal nanoparticles, ensuring sufficient exposure of active sites. Remarkably, the CuO/Ag@C catalyst achieves an impressive Faradaic efficiency of 48.6% for C2H4 at -0.7 V vs. RHE, demonstrating excellent stability. Both experimental results and theoretical calculations indicate that Ag sites promote the production of CO, enhancing the coverage of *CO on Cu sites. Furthermore, the reconfiguration of charge density at the Cu-Ag interface optimizes the electronic states of the reaction sites, reducing the formation energy of the key intermediate *OCCHO, thereby favoring C2H4 production effectively. This work provides insight into structurally rational catalyst design for highly active and selective multiphase catalysts.

Understanding the CO2 Reduction Selectivity toward Ethanol on Single Atom Doped Cu/Cu2O Catalysts: Insights from Bader Charge as a Descriptor

In the CO2 reduction reactions (CO2RR), the product selectivity is strongly dependent on the binding energy differences of the key intermediates. Herein, we systematically evaluated the CO2RR reaction pathways on single transition metal atom doped catalysts TM1Cu/Cu2O by density functional theory (DFT) methods and found that *CO is more likely to undergo C-O bond cleavage rather than be hydrogenated on TM1Cu/Cu2O (TM = Sc, Ti, V, Cr, Mn, Fe, Co), which facilitates C2+ production with a low-energy pathway of OC-C coupling, while it prefers to be hydrogenated to form CHO on TM1Cu/Cu2O (TM = Ni, Cu). The defects of Cu in TM1Cu/Cu2O were confirmed to enhance the production of ethanol. Furthermore, we established a scaling relationship between binding free energies of the key intermediates with the Bader charges of the active sites TM on TM1Cu/Cu2O and defective TM1Cu/Cu2O surfaces. This relationship facilitates a rational and efficient design of Cu/Cu2O-based catalysts.

Unravelling the Effect of Crystal Facet of Derived-Copper Catalysts on the Electroreduction of Carbon Dioxide under Unified Mass Transport Condition

Altering the physical structure and chemical property of copper, i.e., particle size, surface morphology, composition or crystal facet, has been demonstrated to be effective in steering the selectivity of products in electrochemical reduction of carbon dioxide. However, these modifications generally result in the change of active surface area, leading to differences in geometric current density and local pH, which are also demonstrated to be the key factors for observed selectivity change. In this work, we deconvolute the effect of mass transport and local pH from the effect of crystal facet by investigating five copper-based catalysts with identical roughness factor for electrochemical reduction of carbon dioxide in an H-cell. Interestingly, CuO-derived catalyst stands out as the best catalyst for C-C coupling. At -1.07 V vs. RHE, the faradaic efficiency of C2+ product reaches 44.3 %, with a partial current density of -21.6 mA cm-2. Electrochemical adsorption of *OH reveals that the C2+ product selectivity of derived-copper catalysts correlates positively with the ratio of Cu(100)/Cu(110) of five catalysts. Additionally, in situ Raman spectroscopy reveals that the percentage of low-frequency-band linear CO (LFB-CO), which is attributed to the adsorbed *CO on Cu(100) facet, increases with the C-C coupling efficiency.

Switching CO-to-Acetate Electroreduction on Cu Atomic Ensembles

The electrocatalytic reaction pathway is highly dependent on the intrinsic structure of the catalyst. CO2/CO electroreduction has recently emerged as a potential approach for obtaining C2+ products, but it is challenging to achieve high selectivity for a single C2+ product. Herein, we develop a Cu atomic ensemble that satisfies the appropriate site distance and coordination environment required for electrocatalytic CO-to-acetate conversion, which shows outstanding overall performance with an acetate Faradaic efficiency of 70.2% with a partial current density of 225 mA cm-2 and a formation rate of 2.1 mmol h-1 cm-2. Moreover, a single-pass CO conversion rate of 91% and remarkable stability can be also obtained. Detailed experimental and theoretical investigations confirm the significant advantages of the Cu atomic ensembles in optimizing C-C coupling, stabilizing key ketene intermediate (*CCO), and inhibiting the *HOCCOH intermediate, which can switch the CO reduction pathway from the ethanol/ethylene on the conventional metallic Cu site to the acetate on the Cu atomic ensembles.

Switching CO2 Electroreduction Pathways between Ethylene and Ethanol via Tuning Microenvironment of the Coating on Copper Nanofibers

Engineering the microenvironment of electrode surface is one of the effective means to tune the reaction pathways in CO2RR. In this work, we prepared copper nanofibers with conductive polypyrrole coating by polymerization of pyrrole using polyvinyl pyrrolidone (PVP) as template. As a result, the obtained copper nanofibers Cu/Cu2+1O/SHNC, exhibited a superhydrophobic surface, which demonstrated very high selectivity for ethanol with a Faraday efficiency (FE) of 66.5 % at -1.1 V vs reversible hydrogen electrode (RHE) in flow cell. However, the catalyst Cu/Cu2+1O/NC, which was prepared under the same conditions but without PVP, possessed a hydrophobic surface and exhibited high selectivity towards ethylene at the given potentials. The mechanism for switch of reaction pathways from ethylene to ethanol in CO2RR was studied. Incorporating pyrrolidone groups into the polymer coating results in the formation of a superhydrophobic surface. This surface weakens the hydrogen bonding interaction between interfacial water molecules and facilitates the transfer of CO2, thereby enhancing the local CO2/H2O ratio. The high coverage of *CO promotes the coupling of *CO and *CHO to form C2 intermediates, and reduces the reaction energy for the formation of *CHCHOH (ethanol path) at the interface. This ensures that the reaction pathway is directed towards ethanol.

Tailoring Interlayer Microenvironment of 2D Layered Double Hydroxides for CO2 Reduction with Enhanced C2+ Production

Both the physicochemical properties of catalytic material and the structure of loaded catalyst layer (CL) on gas diffusion electrode (GDE) are of crucial importance in determining the conversion efficiency and product selectivity of carbon dioxide reduction reaction (CO2RR). However, the highly reducing reaction condition of CO2RR will lead to the uncontrollable structural and compositional changes of catalysts, making it difficult to tailor surface properties and microstructure of the real active species for favored products. Herein, the interlayer microenvironment of copper-based layered double hydroxides (LDHs) is rationally tuned by a facile ink solvent engineering, which affects both the surface characters and microstructure of CL on GDE, leading to distinct catalytic activity and product selectivity. According to series of in situ and ex situ techniques, the appropriate surface wettability and thickness of porous CL are found to play critical roles in controlling the local CO2 concentration and water dissociation steps that are key for hydrogenation during CO2RR, leading to a high Faradaic efficiency of 75.3% for C2+ products and a partial current density of 275 mA cm-2 at -0.8 V versus RHE. This work provides insights into rational design of efficient electrocatalysts toward CO2RR for multi-carbon generation.

Dual-Anion-Stabilized Cuδ+ Sites in Cu2(OH)2CO3 for High C2+ Selectivity in the CO2 Electroreduction Reaction

The excessive emission of CO2 has aroused increasingly serious environmental problems. Electrochemical CO2 reduction reaction (CO2RR) is an effective way to reduce CO2 concentration and simultaneously produce highly valued chemicals and fuels. Cuδ+ species are regarded as promising active sites to obtain multi-carbon compounds in CO2RR, however, they are easily reduced to Cu0 during the reaction and fail to retain the satisfying selectivity for C2+ products. Herein, via a one-step method, we synthesize Cu2(OH)2CO3 microspheres composed of nanosheets, which has achieved a superior Faraday efficiency for C2+ products as high as 76.29 % at -1.55 V vs. RHE in an H cell and 78.07 % at -100 mA cm-2 in a flow cell. Electrochemical measurements, in situ Raman spectra and attenuated total reflectance infrared spectra (ATR-IR) as well as the theoretic calculation unveil that, compared with Cu(OH)2 and CuO, the dual O-containing anionic groups (OH- and CO3 2-) in Cu2(OH)2CO3 can effectively stabilize the Cuδ+ species, promote the adsorption and activation of CO2, boost the coverage of *CO and the coupling of *CO-*COH, thus sustain the flourishment of C2+ products.

Highly Selective CO2 Electroreduction to Multi-Carbon Alcohols via Amine Modified Copper Nanoparticles at Acidic Conditions

Electroreduction of CO2 into multi-carbon (C2+) products (e.g. C2+ alcohols) offers a promising way for CO2 utilization. Use of strong alkaline electrolytes is favorable to producing C2+ products. However, CO2 can react with hydroxide to form carbonate/bicarbonate, which results in low carbon utilization efficiency and poor stability. Using acidic electrolyte is an efficient way to solve the problems, but it is a challenge to achieve high selectivity of C2+ products. Here we report that the amine modified copper nanoparticles exhibit high selectivity of C2+ products and carbon utilization at acidic condition. The Faradaic efficiency (FE) of C2+ products reach up to 81.8 % at acidic media (pH=2) with a total current density of 410 mA cm-2 over n-butylamine modified Cu. Especially the FE of C2+ alcohols is 52.6 %, which is higher than those reported for CO2 electroreduction at acidic condition. In addition, the single-pass carbon efficiency towards C2+ production reach up to 60 %. Detailed studies demonstrate that the amine molecule on the surface of Cu cannot only enhance the formation, adsorption and coverage of *CO, but also provide a hydrophobic environment, which result in the high selectivity of C2+ alcohols at acidic condition.

Cooperative Use of N-Heterocyclic Carbenes and Thiols on a Silver Surface: A Synergetic Approach to Surface Modification

Surface modification through the formation of a self-assembled monolayer (SAM) can effectively engineer the physicochemical properties of the surface/material. However, the precise design of multifunctional SAMs at the molecular level is still a major challenge. Here, we jointly use N-heterocyclic carbenes (NHCs) and thiols to form multifunctional hetero-SAM systems that demonstrate excellent chemical stability, electrical conductivity, and, in silico, catalytic activity. This synergistic effect is facilitated by the high surface mobility and electron-rich nature of NHCs, combined with the strong binding strength of thiols. Scanning tunneling microscopy, electrical conductivity, and scanning electron microscope measurements, as well as density functional theory calculations, were employed to explore the synergistic interactions in the supramolecular SAMs. The van der Waals integration of ballbot-type NHCs and thiols enables the SAMs to exhibit both superior surface anticorrosion properties (attributing to the shift in the d-band center) and low surface resistance originating from the band alignment. Moreover, we find that the deposition sequence of flat-lying NHCs and thiols results in SAMs with different configurations, which can further tune the mechanistic pathway in silico in the acetylene hydrogenation process. Our results provide essential molecular insights into the local electronic control of the new SAM/metal interface and the high stability of the emergent multifunctionality (NHC/thiol)-SAMs forming self-assembled lamellae structures in the nanometer regime.

Promoting Water Activation via Molecular Engineering Enables Efficient Asymmetric C-C Coupling during CO2 Electroreduction

Water activation plays a crucial role in CO2 reduction, but improving the electrocatalytic performance through controlled water activation presents a significant challenge. Herein, we achieved electrochemical CO2 reduction to ethene and ethanol with high selectivity by promoting water dissociation and asymmetric C-C coupling by engineering Cu surfaces with N-H-rich molecules. Direct spectroscopic evidence, coupled with density functional theory calculations, demonstrates that the N-H-rich molecules accelerate interfacial water dissociation via hydrogen-bond interactions, and the generated hydrogen species facilitate the conversion of *CO to *CHO. This enables the efficient asymmetric *CHO-*CO coupling to C2 products with a faradaic efficiency (FE) ∼ 30% higher than that of the unmodified catalyst. Moreover, by adjustment of the relative *CHO/*CO coverage via Cu surface facet regulation, the selectivity can be entirely switched between C2 products and CH4. These mechanistic insights further guided the development of a more efficient catalyst by directly modifying Cu2O nanocubes with the N-H-rich molecule, achieving remarkable C2 product (mainly ethene and ethanol) FEs of 85.7% at a current density of 800 mA cm-2 and excellent stability under nearing industrial conditions. This study advances our understanding of the CO2 reduction mechanisms and offers an effective and general strategy for enhancing electrocatalytic performance by accelerating water dissociation.

Dual-Metal Sites Drive Tandem Electrocatalytic CO2 to C2+ Products

The electrochemical conversion of CO2 into valuable chemicals is a promising route for renowable energy storage and the mitigation of greenhouse gas emission, and production of multicarbon (C2+) products is highly desired. Here, we report a 1.4 %Pd-Cu@CuPz2 comprising of dispersive CuOx and PdO dual nanoclusters embedded in the MOF CuPz2 (Pz=Pyrazole), which achieves a high C2+ Faradaic efficiency (FEC2+) of 81.9 % and C2+ alcohol FE of 47.5 % with remarkable stability when using 0.1 M KCl aqueous solution as electrolyte in a typical H-cell. Particularly, the FE of alcohol is obviously improved on 1.4 %Pd-Cu@CuPz2 compared to Cu@CuPz2. Theoretical calculations have revealed that the enhanced interfacial electron transfer facilitates the adsorption of *CO intermediate and *CO-*CO dimerization on the Cu-Pd dual sites bridged by Cu nodes of CuPz2. Additionally, the oxophilicity of Pd can stabilize the key intermediate *CH2CHO and promote subsequent proton-coupled electron transfer more efficiently, confirming that the formation pathway is skew towards *C2H5OH. Consequently, the Cu-Pd dual sites play a synergistic tandem role in cooperatively improving the selectivity of alcohol and accelerating reductive conversion of CO2 to C2+.

Steering the Site Distance of Atomic Cu-Cu Pairs by First-Shell Halogen Coordination Boosts CO2-to-C2 Selectivity

Electrocatalytic reduction of CO2 into C2 products of high economic value provides a promising strategy to realize resourceful CO2 utilization. Rational design and construct dual sites to realize the CO protonation and C-C coupling to unravel their structure-performance correlation is of great significance in catalysing electrochemical CO2 reduction reactions. Herein, Cu-Cu dual sites with different site distance coordinated by halogen at the first-shell are constructed and shows a higher intramolecular electron redispersion and coordination symmetry configurations. The long-range Cu-Cu (Cu-I-Cu) dual sites show an enhanced Faraday efficiency of C2 products, up to 74.1 %, and excellent stability. In addition, the linear relationships that the long-range Cu-Cu dual sites are accelerated to C2H4 generation and short-range Cu-Cu (Cu-Cl-Cu) dual sites are beneficial for C2H5OH formation are disclosed. In situ electrochemical attenuated total reflection surface enhanced infrared absorption spectroscopy, in situ Raman and theoretical calculations manifest that long-range Cu-Cu dual sites can weaken reaction energy barriers of CO hydrogenation and C-C coupling, as well as accelerating deoxygenation of *CH2CHO. This study uncovers the exploitation of site-distance-dependent electrochemical properties to steer the CO2 reduction pathway, as well as a potential generic tactic to target C2 synthesis by constructing the desired Cu-Cu dual sites.

Anionic Metal-Organic Framework Derived Cu Catalyst for Selective CO2 Electroreduction to Hydrocarbons

Metal-organic frameworks (MOFs)-related Cu materials are promising candidates for promoting electrochemical CO2 reduction to produce valuable chemical feedstocks. However, many MOF materials inevitable undergo reconstruction under reduction conditions; therefore, exploiting the restructuring of MOF materials is of importance for the rational design of high-performance catalyst targeting multi-carbon products (C2). Herein, a facile solvent process is choosed to fabricate HKUST-1 with an anionic framework (a-HKUST-1) and utilize it as a pre-catalyst for alkaline CO2RR. The a-HKUST-1 catalyst can be electrochemically reduced into Cu with significant structural reconstruction under operating reaction conditions. The anionic HKUST-1 derived Cu catalyst (aHD-Cu) delivers a FEC2H4 of 56% and FEC2 of ≈80% at -150 mA cm-2 in alkaline electrolyte. The resulting aHD-Cu catalyst has a high electrochemically active surface area and low coordinated sites. In situ Raman spectroscopy indicates that the aHD-Cu surface displays higher coverage of *CO intermediates, which favors the production of hydrocarbons.

In Situ Defect Engineering of Fe-MIL for Self-Enhanced Peroxidase-Like Activity

Defect engineering is an effective strategy to enhance the enzyme-like activity of nanozymes. However, previous efforts have primarily focused on introducing defects via de novo synthesis and post-synthetic treatment, overlooking the dynamic evolution of defects during the catalytic process involving highly reactive oxygen species. Herein, a defect-engineered metal-organic framework (MOF) nanozyme with mixed linkers is reported. Over twofold peroxidase (POD)-like activity enhancement compared with unmodified nanozyme highlights the critical role of in situ defect formation in enhancing the catalytic performance of nanozyme. Experimental results reveal that highly active hydroxyl radical (•OH) generated in the catalytic process etches the 2,5-dihydroxyterephthalic acid ligands, contributing to electronic structure modulation of metal sites and enlarged pore sizes in the framework. The self-enhanced POD-like activity induced by in situ defect engineering promotes the generation of •OH, holding promise in colorimetric sensing for detecting dichlorvos. Utilizing smartphone photography for RGB value extraction, the resultant sensing platform achieves the detection for dichlorvos ranging from 5 to 300 ng mL-1 with a low detection limit of 2.06 ng mL-1. This pioneering work in creating in situ defects in MOFs to improve catalytic activity offers a novel perspective on traditional defect engineering.

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 -0.6 V 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.

Tri-site Synergistic Cu(I)/Cu(II)─N Single-Atom Catalysts for Additive-Free CO2 Conversion

As the highly stable and abundant carbon source in nature, the activation and conversion of CO2 into high-value chemicals is highly desirable yet challenging. The development of Cu(I)/Cu(II)─N tri-site synergistic single-atom catalysts (TS-SACs) with remarkable CO2 activation and conversion performance is presented, eliminating the need for external additives in cascade reactions. Under mild conditions (40 °C, atmospheric CO2), the catalyst achieves high yields (up to 99%) of valuable 2-oxazolidinones from CO2 and propargylamine. Notably, the catalyst demonstrates easy recovery, short reaction times, and excellent tolerance toward various functional groups. Supported by operando techniques and density functional theory calculations, it is elucidated that the spatially proximal Cu(I)/Cu(II)─N sites facilitate the coupling of multiple chemical transformations. This surpasses the performance of supported isolated Cu(I) or Cu(II) catalysts and traditional organic base-assisted cascade processes. These Cu(I)/Cu(II)─N tri-site synergistic atom active sites not only enable the co-activation of CO2 at the Cu(II)─N pair and alkyne at the Cu(I) site but also induce a di-metal locking geometric effect that accelerates the ring closure of cyclic carbamate intermediates. The work overcomes the limitations of single metal sites and paves the way for designing multisite catalysts for CO2 activation, especially for consecutive activation, tandem, or cascade reactions.

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.

Tensile-Strained Cu Penetration Electrode Boosts Asymmetric C-C Coupling for Ampere-Level CO2-to-C2+ Reduction in Acid

The synthesis of multicarbon (C2+) products remains a substantial challenge in sustainable CO2 electroreduction owing to the need for sufficient current density and faradaic efficiency alongside carbon efficiency. Herein, we demonstrate ampere-level high-efficiency CO2 electroreduction to C2+ products in both neutral and strongly acidic (pH=1) electrolytes using a hierarchical Cu hollow-fiber penetration electrode (HPE). High concentration of K+ could concurrently suppress hydrogen evolution reaction and facilitate C-C coupling, thereby promoting C2+ production in strong acid. By optimizing the K+ and H+ concentration and CO2 flow rate, a faradaic efficiency of 84.5 % and a partial current density as high as 3.1 A cm-2 for C2+ products, alongside a single-pass carbon efficiency of 81.5 % and stable electrolysis for 240 h were demonstrated in a strong acidic solution of H2SO4 and KCl (pH=1). Experimental measurements and density functional theory simulations suggested that tensile-strained Cu HPE enhances the asymmetric C-C coupling to steer the selectivity and activity of C2+ products.

Optimal Oxophilicity at the Fe-Nx Interface Enhances the Generation of Singlet Oxygen for Efficient Fenton-Like Catalysis

In the pursuit of efficient singlet oxygen generation in Fenton-like catalysis, the utilization of single-atom catalysts (SACs) emerges as a highly desired strategy. Here, a discovery is reported that the single-atom Fe coordinated with five N-atoms on N-doped porous carbon, denoted as Fe-N5/NC, outperform its counterparts, those coordinated with four (Fe-N4/NC) or six N-atoms (Fe-N6/NC), as well as state-of-the-art SACs comprising other transition metals. Thus, Fe-N5/NC exhibits exceptional efficacy in activating peroxymonosulfate for the degradation of organic pollutants. The coordination number of N-atoms can be readily adjusted by pyrolysis of pre-assembly structures consisting of Fe3+ and various isomers of phenylenediamine. Fe-N5/NC displayed outstanding tolerance to environmental disturbances and minimal iron leaching when incorporated into a membrane reactor. A mechanistic study reveals that the axial ligand N reduces the contribution of Fe-3d orbitals in LUMO and increases the LUMO energy of Fe-N5/NC. This, in turn, reduces the oxophilicity of the Fe center, promoting the reactivity of *OO intermediate-a pivotal step for yielding singlet oxygen and the rate-determining step. These findings unveil the significance of manipulating the oxophilicity of metal atoms in single-atom catalysis and highlight the potential to augment Fenton-like catalysis performance using Fe-SACs.

Regulating the Critical Intermediates of Dual-Atom Catalysts for CO2 Electroreduction

Electrocatalysis is a very attractive way to achieve a sustainable carbon cycle by converting CO2 into organic fuels and feedstocks. Therefore, it is crucial to design advanced electrocatalysts by understanding the reaction mechanism of electrochemical CO2 reduction reaction (eCO2RR) with multiple electron transfers. Among electrocatalysts, dual-atom catalysts (DACs) are promising candidates due to their distinct electronic structures and extremely high atomic utilization efficiency. Herein, the eCO2RR mechanism and the identification of intermediates using advanced characterization techniques, with a particular focus on regulating the critical intermediates are systematically summarized. Further, the insightful understanding of the functionality of DACs originates from the variable metrics of electronic structures including orbital structure, charge distribution, and electron spin state, which influences the active sites and critical intermediates in eCO2RR processes. Based on the intrinsic relationship between variable metrics and critical intermediates, the optimized strategies of DACs are summarized containing the participation of synergistic atoms, engineering of the atomic coordination environment, regulation of the diversity of central metal atoms, and modulation of metal-support interaction. Finally, the challenges and future opportunities of atomically dispersed catalysts for eCO2RR processes are discussed.

Urea Synthesis via Coelectrolysis of CO2 and Nitrate over Heterostructured Cu-Bi Catalysts

Electrocatalytic coupling of CO2 and NO3- to urea is a promising way to mitigate greenhouse gas emissions, reduce waste from industrial processes, and store renewable energy. However, the poor selectivity and activity limit its application due to the multistep process involving diverse reactants and reactions. Herein, we report the first work to design heterostructured Cu-Bi bimetallic catalysts for urea electrosynthesis. A high urea Faradaic efficiency (FE) of 23.5% with a production rate of 2180.3 μg h-1 mgcat-1 was achieved in H-cells, which surpassed most reported electrocatalysts in the literature. Moreover, the catalyst had a remarkable recycling stability. Experiments and density functional theory calculations demonstrated that introduction of moderate Bi induced the formation of the Bi-Cu/O-Bi/Cu2O heterostructure with abundant phase boundaries, which are beneficial for NO3-, CO2, and H2O activation and enhance C-N coupling and promote *HONCON intermediate formation. Moreover, favorable *HNCONH2 protonation and urea desorption processes were also validated, further explaining the reason for high activity and selectivity toward urea.

Multivalent Cu sites synergistically adjust carbonaceous intermediates adsorption for electrocatalytic ethanol production

Copper (Cu)-based catalysts show promise for electrocatalytic CO2 reduction (CO2RR) to multi-carbon alcohols, but thermodynamic constraints lead to competitive hydrocarbon (e.g., ethylene) production. Achieving selective ethanol production with high Faradaic efficiency (FE) and current density is still challenging. Here we show a multivalent Cu-based catalyst, Cu-2,3,7,8-tetraaminophenazine-1,4,6,9-tetraone (Cu-TAPT) with Cu2+ and Cu+ atomic ratio of about 1:2 for CO2RR. Cu-TAPT exhibits an ethanol FE of 54.3 ± 3% at an industrial-scale current density of 429 mA cm-2, with the ethanol-to-ethylene ratio reaching 3.14:1. Experimental and theoretical calculations collectively unveil that the catalyst is stable during CO2RR, resulting from suitable coordination of the Cu2+ and Cu+ with the functional groups in TAPT. Additionally, mechanism studies show that the increased ethanol selectivity originates from synergy of multivalent Cu sites, which can promote asymmetric C-C coupling and adjust the adsorption strength of different carbonaceous intermediates, favoring hydroxy-containing C2 intermediate (*HCCHOH) formation and formation of ethanol.

Strategies for overcoming challenges in selective electrochemical CO2 conversion to ethanol

The electrochemical conversion of carbon dioxide (CO2) to valuable chemicals is gaining significant attention as a pragmatic solution for achieving carbon neutrality and storing renewable energy in a usable form. Recent research increasingly focuses on designing electrocatalysts that specifically convert CO2 into ethanol, a desirable product due to its high-energy density, ease of storage, and portability. However, achieving high-efficiency ethanol production remains a challenge compared to ethylene (a competing product with a similar electron configuration). Existing electrocatalytic systems often suffer from limitations such as low energy efficiency, poor stability, and inadequate selectivity toward ethanol. Inspired by recent progress in the field, this review explores fundamental principles and material advancements in CO2 electroreduction, emphasizing strategies for ethanol production over ethylene. We discuss electrocatalyst design, reaction mechanisms, challenges, and future research directions. These advancements aim to bridge the gap between current research and industrialized applications of this technology.

Highly Selective Electrocatalytic CO2 Conversion to Tailored Products through Precise Regulation of Hydrogenation and C-C Coupling

The electrochemical reduction reaction of carbon dioxide (CO2RR) into valuable products offers notable economic benefits and contributes to environmental sustainability. However, precisely controlling the reaction pathways and selectively converting key intermediates pose considerable challenges. In this study, our theoretical calculations reveal that the active sites with different states of copper atoms (1-3-5-7-9) play a pivotal role in the adsorption behavior of the *CHO critical intermediate. This behavior dictates the subsequent hydrogenation and coupling steps, ultimately influencing the formation of the desired products. Consequently, we designed two model electrocatalysts comprising Cu single atoms and particles supported on CeO2. This design enables controlled *CHO intermediate transformation through either hydrogenation with *H or coupling with *CO, leading to a highly selective CO2RR. Notably, our selective control strategy tunes the Faradaic efficiency from 61.1% for ethylene (C2H4) to 61.2% for methane (CH4). Additionally, the catalyst demonstrated a high current density and remarkable stability, exceeding 500 h of operation. This work not only provides efficient catalysts for selective CO2RR but also offers valuable insights into tailoring surface chemistry and designing catalysts for precise control over catalytic processes to achieve targeted product generation in CO2RR technology.

Tailoring Cu-Based Electrocatalysts for Enhanced Electrochemical CO2 Reduction to Alcohols: Structure-Selectivity Relationship

The use of CO2 as a feedstock for the production of carbon-based fuels and value-added chemicals offers a promising route toward carbon neutrality. In this study, two Cu-based electrocatalysts, namely, Cu24/N-C and Cu2/N-C, are successfully prepared by thermal treatment of Cu24 metal-organic polyhedron-loaded zeolitic imidazolate framework-8 (ZIF-8) nanocrystals (Cu24/ZIF-8) and Cu2 dinuclear compound-loaded ZIF-8 nanocrystals (Cu2/ZIF-8), respectively. Extensive structural and compositional analyses were conducted to confirm the formation of Cu nanocluster-loaded N-doped porous carbon supports in both Cu24/N-C and Cu2/N-C and Cu nanoparticles encapsulated by graphitic carbons in Cu2/N-C as well. These two Cu-based electrocatalysts exhibited different behaviors in the electrochemical CO2 reduction reaction (CO2RR). The Cu24/N-C electrocatalyst showed high selectivity for CO production, while Cu2/N-C showed a preference for alcohol generation. The excellent stability of Cu2/N-C over a 30 h continuous electrochemical reduction further highlights its potential for practical applications. The difference in electrocatalytic performance observed in the two catalysts for CO2RR was attributed to distinct catalytic sites associated with Cu nanoclusters and nanoparticles. This research reveals the significance of their structures and compositions for the development of highly selective electrocatalysts for CO2 reduction.