In Situ Infrared Spectroscopic Evidence of Enhanced Electrochemical CO2 Reduction and C-C Coupling on Oxide-Derived Copper

Amino-functionalization enhanced CO2 reduction reaction in pure water

The electrochemical reduction of carbon dioxide (CO2RR) to carbon monoxide represents a cost-effective pathway towards realizing carbon neutrality. To suppress the hydrogen evolution reaction (HER), the presence of alkali cations is critical, which can however lead to precipitate formation on the electrode, adversely impacting the device stability. Employing pure water as the electrolyte in zero-gap CO2 electrolyzers can address this challenge, albeit at the cost of diminished catalyst performance due to the absence of alkali cations. In this study, we introduce a novel approach by implementing amino modifications on the catalyst surface to mimic the function of alkali metal cations, while simultaneously working in pure water. This modification enhances the adsorption of carbon dioxide and protons, thereby facilitating the CO2RR while concurrently suppressing the HER. Utilizing this strategy in a zero-gap CO2 electrolyzer with pure water as the anolyte resulted in an impressive carbon monoxide faradaic efficiency (FECO) of 95.5% at a current density of 250 mA cm-2, while maintaining stability for over 180 hours without any maintenance.

Prebiotic Synthesis of Microdroplets from Formate over a Bimetallic Cobalt-Nickel Nanomotif

The hypothesis underlying the abiogenic origin of life suggests that the nonenzymatic synthesis of long-chain fatty acids led to the construction of vesicles for compartmentalization in an early stage during the transition from geochemistry to biochemistry. However, evidence for this theory remains elusive as C5+ carboxylic acids cannot be synthesized using current laboratory simulations. Here, we report the synthesis of long-chain carboxylic acids (C3-C7) with a 42 mmol/gCo+Ni yield and 87.7% selectivity from formate (an intermediate of the acetyl-CoA pathway) over a cobalt-nickel alloy under alkaline hydrothermal conditions and the subsequent formation of microdroplets from organics. Density functional theory (DFT) calculations confirmed that the synergistic effect of the bimetal catalyst is key for catalyzing C-C coupling. Investigations by infrared spectroscopy, electron paramagnetic resonance, and isotope-labeled experiments revealed that HCO* serves as a reaction intermediate and is involved in the subsequent elementary steps for synthesizing long-chain carboxylic acids from formate. Taken together, these findings may help explain how the first protocells emerged geochemically and provide support for the hypothesis of the abiogenic origin of life. The hydrothermal system developed may also be applicable for the sustainable synthesis of long-chain carboxylates from one-carbon substrates using nonnoble metal catalysts.

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

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

Identification of Degradation Reasons for a CO2 MEA Electrolyzer Using the Distribution of Relaxation Times Analysis

The application of membrane electrode assembly (MEA) in electrocatalytic CO2 reduction (ECO2R) technology is an essential step toward industrialization. Nevertheless, the issue of ECO2R failure in MEA during extended operation hinders its industrial application. In this work, we employed in situ, nondestructive electrochemical impedance spectroscopy (EIS) techniques combined with distribution of relaxation times (DRT) methodology to diagnose the causes of the failure. By systematically investigating the variations in polarization resistance throughout the degradation process and utilizing a controlled variable approach to identify the origin of polarization, we diagnosed the degeneration of ionomers as the primary cause of the performance degradation of ECO2R in this instance. We further confirmed the reliability of our findings through material characterization and respraying ionomers onto the catalyst surface. This research provides an effective diagnostic method for the failure analysis of ECO2R performance in MEA, which is crucial for advancing industrialization of ECO2R technology.

Potential-driven structural distortion in cobalt phthalocyanine for electrocatalytic CO2/CO reduction towards methanol

Cobalt phthalocyanine immobilized on carbon nanotube has demonstrated appreciable selectivity and activity for methanol synthesis in electrocatalytic CO2/CO reduction. However, discrepancies in methanol production selectivity and activity between CO2 and CO reduction have been observed, leading to inconclusive mechanisms for methanol production in this system. Here, we discover that the interaction between cobalt phthalocyanine molecules and defects on carbon nanotube substrate plays a key role in methanol production during CO2/CO electroreduction. Through detailed operando X-ray absorption and infrared spectroscopies, we find that upon application of cathodic potential, this interaction induces the transformation of the planar CoN4 center in cobalt phthalocyanine to an out-of-plane distorted configuration. Consequently, this potential induced structural change promotes the transformation of linearly bonded *CO at the CoN4 center to bridge *CO, thereby facilitating methanol production. Overall, these comprehensive mechanistic investigations and the outstanding performance (methanol partial current density over 150 mA cm-2) provide valuable insights in guiding the activity and selectivity of immobilized cobalt phthalocyanine for methanol production in CO2/CO reduction.

Altering the CO2 Electroreduction Pathways Towards C1 or C2+ Products via Engineering the Strength of Interfacial Cu-O Bond

Copper (Cu)-based catalysts have established their unique capability for yielding wide value-added products from CO2. Herein, we demonstrate that the pathways of the electrocatalytic CO2 reduction reaction (CO2RR) can be rationally altered toward C1 or C2+ products by simply optimizing the coordination of Cu with O-containing organic species (squaric acid (H2C4O4) and cyclohexanehexaone (C6O6)). It is revealed that the strength of Cu-O bonds can significantly affect the morphologies and electronic structures of derived Cu catalysts, resulting in the distinct behaviors during CO2RR. Specifically, the C6O6-Cu catalysts made up from organized nanodomains shows a dominant C1 pathway with a total Faradaic efficiency (FE) of 63.7 % at -0.6 V (versus reversible hydrogen electrode, RHE). In comparison, the C4O4-Cu with an about perfect crystalline structure results in uniformly dispersed Cu-atoms, showing a notable FE of 65.8 % for C2+ products with enhanced capability of C-C coupling. The latter system also shows stable operation over at least 10 h with a high current density of 205.1 mA cm-2 at -1.0 VRHE, i.e., is already at the boarder of practical relevance. This study sheds light on the rational design of Cu-based catalysts for directing the CO2RR reaction pathway.

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.

Modulating the Electrolyte Microenvironment in Electrical Double Layer for Boosting Electrocatalytic Nitrate Reduction to Ammonia

Electrochemical nitrate reduction reaction (NO3RR) is a promising approach to achieve remediation of nitrate-polluted wastewater and sustainable production of ammonia. However, it is still restricted by the low activity, selectivity and Faraday efficiency for ammonia synthesis. Herein, we propose an effective strategy to modulate the electrolyte microenvironment in electrical double layer (EDL) by mediating alkali metal cations in the electrolyte to enhance the NO3RR performance. Taking bulk Cu as a model catalyst, the experimental study reveals that the NO3 --to-NH3 performance in different electrolytes follows the trend Li+ Collapse

Key Words

• alkali metal cation
• electrical double layer
• nitrate reduction
• proton transport
• reaction kinetics

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MESH Headings Collapse

Grants

• GXXT-2022-026 University Synergy Innovation Program of Anhui Province
• 2022AH050112 and 2022AH010004 Project of Anhui Provincial Department of Education
• KJ2021A0070 and KJ2021A1168 Natural Science Research Project of Universities in Anhui Province

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Affiliation(s)

Weidong Wen School of Materials Science and Engineering, Anhui University, Hefei, 230601, P. R. China
Shidong Fang Institute of Energy, Hefei Comprehensive National Science Centre (Anhui Energy Laboratory), Hefei, 230051, P. R. China Hefei Institutes of Physical Science, Chinese Academy of Sciences (CAS), Hefei, 230031, P. R. China
Yitong Zhou Institutes of Physical Science and Information Technology, Anhui University, Hefei, 230601, P. R. China
Ying Zhao School of Pharmacy, Anhui Xinhua University, Hefei, 230088, P. R. China
Peng Li School of Materials Science and Engineering, Anhui University, Hefei, 230601, P. R. China
Xin-Yao Yu School of Materials Science and Engineering, Anhui University, Hefei, 230601, P. R. China

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Liquid Metal-Enabled Tunable Synthesis of Nanoporous Polycrystalline Copper for Selective CO2-to-Formate Electrochemical Conversion

Copper-based catalysts exhibit high activity in electrochemical CO2 conversion to value-added chemicals. However, achieving precise control over catalysts design to generate narrowly distributed products remains challenging. Herein, a gallium (Ga) liquid metal-based approach is employed to synthesize hierarchical nanoporous copper (HNP Cu) catalysts with tailored ligament/pore and crystallite sizes. The nanoporosity and polycrystallinity are generated by dealloying intermetallic CuGa2 formed after immersing pristine Cu foil in liquid Ga in a basic or acidic solution. The liquid metal-based approach allows for the transformation of monocrystalline Cu to the polycrystalline HNP Cu with enhanced CO2 reduction reaction (CO2RR) performance. The dealloyed HNP Cu catalyst with suitable crystallite size (22.8 nm) and nanoporous structure (ligament/pore size of 45 nm) exhibits a high Faradaic efficiency of 91% toward formate production under an applied potential as low as -0.3 VRHE. The superior CO2RR performance can be ascribed to the enlarged electrochemical catalytic surface area, the generation of preferred Cu facets, and the rich grain boundaries by polycrystallinity. This work demonstrates the potential of liquid metal-based synthesis for improving catalysts performance based on structural design, without increasing compositional complexity.

Boosting Solar-Driven CO2 Conversion to Ethanol via Single-Atom Catalyst with Defected Low-Coordination Cu-N2 Motif

Cu-based catalysts have been shown to selectively catalyze CO2 photoreduction to C2+ solar fuels. However, they still suffer from poor activity and low selectivity. Herein, we report a high-performance carbon nitride supported Cu single-atom catalyst featuring defected low-coordination Cu-N2 motif (Cu-N2-V). Lead many recently reported photocatalysts and its Cu-N3 and Cu-N4 counterparts, Cu-N2-V exhibits superior photocatalytic activity for CO2 reduction to ethanol and delivers 69.8 μmol g-1 h-1 ethanol production rate, 97.8 % electron-based ethanol selectivity, and a yield of ~10 times higher than Cu-N3 and Cu-N4. Revealed by the extensive experimental investigation combined with DFT calculations, the superior photoactivity of Cu-N2-V stems from its defected Cu-N2 configuration, in which the Cu sites are electron enriched and enhance electron delocalization. Importantly, Cu in Cu-N2-V exist in both Cu+ and Cu2+ valence states, although predominantly as Cu+. The Cu+ sites support the CO2 activation, while the co-existence of Cu+/Cu2+ sites are highly conducive for strong *CO adsorption and subsequent *CO-*CO dimerization enabling C-C coupling. Furthermore, the hollow microstructure of the catalyst also promotes light adsorption and charge separation efficiency. Collectively, these make Cu-N2-V an effective and high-performance catalyst for the solar-driven CO2 conversion to ethanol. This study also elucidates the C-C coupling reaction path via *CO-*CO to *COCOH and rate-determining step, and reveals the valence state change of partial Cu species from Cu+ to Cu2+ in Cu-N2-V during CO2 photoreduction reaction.

Constructing Favorable Microenvironment on Copper Grain Boundaries for CO2 Electro-conversion to Multicarbon Products

The electrochemical CO2 reduction reaction (eCO2RR) to multicarbon chemicals provides a promising avenue for storing renewable energy. Herein, we synthesized small Cu nanoparticles featuring enriched tiny grain boundaries (RGBs-Cu) through spatial confinement and in situ electroreduction. In-situ spectroscopy and theoretical calculations demonstrate that small-sized Cu grain boundaries significantly enhance the adsorption of the *CO intermediate, owing to the presence of abundant low-coordinated and disordered atoms. Furthermore, these grain boundaries, generated in situ under high current conditions, exhibit excellent stability during the eCO2RR process, thereby creating a stable *CO-rich microenvironment. This high local *CO concentration around the catalyst surface can reduce the energy barrier for C-C coupling and significantly increase the Faradaic efficiency (FE) for multicarbon products across both neutral and alkaline electrolytes. Specifically, the developed RGBs-Cu electrocatalyst achieved a peak FE of 77.3% for multicarbon products and maintained more than 134 h stability at a constant current density of -500 mA cm-2.

Efficient CO2 electroreduction to ethanol enabled by tip-curvature-induced local electric fields

Electrocatalytic reduction of CO2 into multicarbon (C2+) products offers a promising pathway for CO2 utilization. However, achieving high selectivity towards multicarbon alcohols, such as ethanol, remains a challenge. In this work, we present a novel CuO nanoflower catalyst with engineered tip curvature, achieving remarkable selectivity and efficiency in the electroreduction of CO2 to ethanol. This catalyst exhibits an ethanol faradaic efficiency (FEethanol) of 47% and a formation rate of 320 μmol h-1 cm-2, with an overall C2+ product faradaic efficiency (FEC2+) reaching ∼77.8%. We attribute this performance to the catalyst's sharp tip, which generates a strong local electric field, thereby accelerating CO2 activation and facilitating C-C coupling for deep CO2 reduction. In situ Raman spectroscopy reveals an increased *OH coverage under operating conditions, where the enhanced *OH adsorption facilitates the stabilization of *CHCOH intermediates through hydrogen bonding interaction, thus improving ethanol selectivity. Our findings demonstrate the pivotal role of local electric fields in altering reaction kinetics for CO2 electroreduction, presenting a new avenue for catalyst design aiming at converting CO2 to ethanol.

Bottom-up Growth of Convex Sphere with Adjustable Cu(0)/Cu(I) Interfaces for Effective C2 Production from CO2 Electroreduction

One challenge confronting the Cu2O catalysts in the electrocatalysis of carbon dioxide reduction reaction (CO2RR) is the reduction of active Cu(I) species, resulting in low selectivity and quick deactivation. In this study, we for the first time introduce a bottom-up growth of convex sphere with adjustable Cu(0)/Cu(I) interfaces (Cux@Cu2O convex spheres). Interestingly, the interfaces are dynamically modulated by varying hydrothermal time, thus regulating the conversion of C1 and C2 products. In particular, the 4 h hydrothermal treatment applied to Cu0.25@Cu2O convex sphere with the favorable Cu(0)/Cu(I) interface results in the highest selectivity for C2 products (90.5 %). In situ Fourier-transform infrared spectroscopy measurements and density functional theory calculations reveal that the Cu(0)/Cu(I) interface lowers the energy barrier for the production of ethylene and ethanol while increasing the coverage of localized *CO adsorbate for increased dimerization. This work establishes a novel approach for transforming the state of valence-sensitive electrocatalysts into high-value energy-related engineering products.

Surface Reconstruction of La2CuO4 during the Electrochemical Reduction of Carbon Dioxide to Ethylene and Its Benefits for Enhanced Performance

Electrochemical reduction (ECR) of CO2 to C2H4 has a potential key role in realizing the carbon neutral future, which ultimately relies on the availability of an efficient electrocatalyst that can exhibit a high Faradaic efficiency (FE) for C2H4 production and robust, long-term operational stability. Here, for the first time, we report that upon applying reductive potential and electrolyte to the benchmark La2CuO4 catalyst, surface reconstruction occurred, i.e., the appearance of a distinctive phase evolution process over time, which was successfully monitored using ex situ powder XRD and operando Mott-Schottky (M-S) measurements of La2CuO4 samples that were soaked into the electrolyte and subjected to CO2-ECR for different durations. At the end of such a reconstruction process, an outermost layer consisting of lanthanum carbonate, a thin outer layer made of an amorphous Cu+ material formed over the core bulk La2CuO4, as confirmed by various characterization techniques, which resulted in the redistribution of interfacial electrons and subsequent formation of electron-rich and electron-deficient interfaces. This contributed to the enhancement in FE for C2H4, reaching as much as 58.7%. Such surface reconstruction-induced electronic structure tuning gives new explanations for the superior catalytic performance of La2CuO4 perovskite and also provides a new pathway to advance CO2-ECR technology.

The Tandem Nitrate and CO2 Reduction for Urea Electrosynthesis: Role of Surface N-Intermediates in CO2 Capture and Activation

Electrochemical reduction of CO2 and nitrate offers a promising avenue to produce valuable chemicals through the using of greenhouse gas and nitrogen-containing wastewater. However, the generally proposed reaction pathway of concurrent CO2 and nitrate reduction for urea synthesis requires the catalysts to be both efficient in both CO2 and nitrate reduction, thus narrowing the selection range of suitable catalysts. Herein, we demonstrate a distinct mechanism in urea synthesis, a tandem NO3 - and CO2 reduction, in which the surface amino species generated by nitrate reduction play the role to capture free CO2 and subsequent initiate its activation. When using the TiO2 electrocatalyst derived from MIL-125-NH2, it intrinsically exhibits low activity in aqueous CO2 reduction, however, in the presence of both nitrate and CO2, this catalyst achieves an excellent urea yield rate of 43.37 mmol ⋅ g-1 ⋅ h-1 and a Faradaic efficiency of 48.88 % at -0.9 V vs. RHE in a flow cell. Even at a low CO2 level of 15 %, the Faradaic efficiency of urea synthesis remains robust at 42.33 %. The tandem reduction procedure was further confirmed by in situ spectroscopies and theoretical calculations. This research provides new insights into the selection and design of electrocatalysts for urea synthesis.

Regulating Reactive Oxygen Species over M-N-C Single-Atom Catalysts for Potential-Resolved Electrochemiluminescence

The development of potential-resolved electrochemiluminescence (ECL) systems with dual emitting signals holds great promise for accurate and reliable determination in complex samples. However, the practical application of such systems is hindered by the inevitable mutual interaction and mismatch between different luminophores or coreactants. In this work, for the first time, by precisely tuning the oxygen reduction performance of M-N-C single-atom catalysts (SACs), we present a dual potential-resolved luminol ECL system employing endogenous dissolved O2 as a coreactant. Using advanced in situ monitoring and theoretical calculations, we elucidate the intricate mechanism involving the selective and efficient activation of dissolved O2 through central metal species modulation. This modulation leads to the controlled generation of hydroxyl radical (·OH) and superoxide radical (O2·-), which subsequently trigger cathodic and anodic luminol ECL emission, respectively. The well-designed Cu-N-C SACs, with their moderate oxophilicity, enable the simultaneous generation of ·OH and O2·-, thereby facilitating dual potential-resolved ECL. As a proof of concept, we employed the principal component analysis statistical method to differentiate antibiotics based on the output of the dual-potential ECL signals. This work establishes a new avenue for constructing a potential-resolved ECL platform based on a single luminophore and coreactant through precise regulation of active intermediates.

Polarized Ultrathin BN Induced Dynamic Electron Interactions for Enhancing Acidic Oxygen Evolution

Developing ruthenium-based heterogeneous catalysts with an efficient and stable interface is essential for enhanced acidic oxygen evolution reaction (OER). Herein, we report a defect-rich ultrathin boron nitride nanosheet support with relatively independent electron donor and acceptor sites, which serves as an electron reservoir and receiving station for RuO2, realizing the rapid supply and reception of electrons. Through precisely controlling the reaction interface, a low OER overpotential of only 180 mV (at 10 mA cm-2) and long-term operational stability (350 h) are achieved, suggesting potential practical applications. In situ characterization and theoretical calculations have validated the existence of a localized electronic recycling between RuO2 and ultrathin BN nanosheets (BNNS). The electron-rich Ru sites accelerate the adsorption of water molecules and the dissociation of intermediates, while the interconnection between the O-terminal and B-terminal edge establishes electronic back-donation, effectively suppressing the over-oxidation of lattice oxygen. This study provides a new perspective for constructing a stable and highly active catalytic interface.

Unveiling pH-Dependent Adsorption Strength of *CO2 - Intermediate over High-Density Sn Single Atom Catalyst for Acidic CO2-to-HCOOH Electroreduction

The acidic electrochemical CO2 reduction reaction (CO2RR) for direct formic acid (HCOOH) production holds promise in meeting the carbon-neutral target, yet its performance is hindered by the competing hydrogen evolution reaction (HER). Understanding the adsorption strength of the key intermediates in acidic electrolyte is indispensable to favor CO2RR over HER. In this work, high-density Sn single atom catalysts (SACs) were prepared and used as catalyst, to reveal the pH-dependent adsorption strength and coverage of *CO2 - intermediatethat enables enhanced acidic CO2RR towards direct HCOOH production. At pH=3, Sn SACs could deliver a high Faradaic efficiency (90.8 %) of HCOOH formation and a corresponding partial current density up to -178.5 mA cm-2. The detailed in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic studies reveal that a favorable alkaline microenvironment for CO2RR to HCOOH is formed near the surface of Sn SACs, even in the acidic electrolyte. More importantly, the pH-dependent adsorption strength of *CO2 - intermediate is unravelled over the Sn SACs, which in turn affects the competition between HER and CO2RR in acidic electrolyte.

Dynamic Restructuring of Cu7S4/Cu for Efficient CO2 Electro-reduction to Formate

Optimized catalytic properties and reactant adsorption energy played a crucial role in promoting CO2 electrocatalysis. Herein, Cu7S4/Cu underwent in situ dynamic restructuring to generate S-Cu2O/Cu hybrid catalyst for effective electrochemical CO2 reduction to formate that outperformed Cu2O/Cu and Cu7S4. Thermodynamic and in situ Raman spectra revealed that the optimized adsorption of the HCOO* intermediate on S-Cu2O/Cu was regulated and the H2 pathway (surface H) was suppressed by S-doping. Meanwhile, Cu7S4/Cu nanoflowers created abundant boundaries for ECR and strengthened the CO2 adsorption by inducing Cu. These findings provide a new perspective on synthetic methods for various electrocatalytic reduction processes.

Customizing catalyst surface/interface structures for electrochemical CO2 reduction

Electrochemical CO2 reduction reaction (CO2RR) provides a promising route to converting CO2 into value-added chemicals and to neutralizing the greenhouse gas emission. For the industrial application of CO2RR, high-performance electrocatalysts featuring high activities and selectivities are essential. It has been demonstrated that customizing the catalyst surface/interface structures allows for high-precision control over the microenvironment for catalysis as well as the adsorption/desorption behaviors of key reaction intermediates in CO2RR, thereby elevating the activity, selectivity and stability of the electrocatalysts. In this paper, we review the progress in customizing the surface/interface structures for CO2RR electrocatalysts (including atomic-site catalysts, metal catalysts, and metal/oxide catalysts). From the perspectives of coordination engineering, atomic interface design, surface modification, and hetero-interface construction, we delineate the resulting specific alterations in surface/interface structures, and their effect on the CO2RR process. At the end of this review, we present a brief discussion and outlook on the current challenges and future directions for achieving high-efficiency CO2RR via surface/interface engineering.