Self-Cleaning Catalyst Electrodes for Stabilized CO2 Reduction to Hydrocarbons

Surface Area-Enhanced Cerium and Sulfur-Modified Hierarchical Bismuth Oxide Nanosheets for Electrochemical Carbon Dioxide Reduction to Formate

Electrochemical carbon dioxide reduction reaction (ECO2RR) is a promising approach to synthesize fuels and value-added chemical feedstocks while reducing atmospheric CO2 levels. Here, high surface area cerium and sulfur-doped hierarchical bismuth oxide nanosheets (Ce@S-Bi2O3) are develpoed by a solvothermal method. The resulting Ce@S-Bi2O3 electrocatalyst shows a maximum formate Faradaic efficiency (FE) of 92.5% and a current density of 42.09 mA cm-2 at -1.16 V versus RHE using a traditional H-cell system. Furthermore, using a three-chamber gas diffusion electrode (GDE) reactor, a maximum formate FE of 85% is achieved in a wide range of applied potentials (-0.86 to -1.36 V vs RHE) using Ce@S-Bi2O3. The density functional theory (DFT) results show that doping of Ce and S in Bi2O3 enhances formate production by weakening the OH* and H* species. Moreover, DFT calculations reveal that *OCHO is a dominant pathway on Ce@S-Bi2O3 that leads to efficient formate production. This study opens up new avenues for designing metal and element-doped electrocatalysts to improve the catalytic activity and selectivity for ECO2RR.

Recent Progress on Copper-Based Bimetallic Heterojunction Catalysts for CO2 Electrocatalysis: Unlocking the Mystery of Product Selectivity

Copper-based bimetallic heterojunction catalysts facilitate the deep electrochemical reduction of CO2 (eCO2RR) to produce high-value-added organic compounds, which hold significant promise. Understanding the influence of copper interactions with other metals on the adsorption strength of various intermediates is crucial as it directly impacts the reaction selectivity. In this review, an overview of the formation mechanism of various catalytic products in eCO2RR is provided and highlight the uniqueness of copper-based catalysts. By considering the different metals' adsorption tendencies toward various reaction intermediates, metals are classified, including copper, into four categories. The significance and advantages of constructing bimetallic heterojunction catalysts are then discussed and delve into the research findings and current development status of different types of copper-based bimetallic heterojunction catalysts. Finally, insights are offered into the design strategies for future high-performance electrocatalysts, aiming to contribute to the development of eCO2RR to multi-carbon fuels with high selectivity.

Dual-Ion Co-intercalation Mechanism on a Na2V6O16·3H2O Cathode with a Commercial-Level Mass Loading for Aqueous Zinc-Ion Batteries with High Areal Capacity

A proton (H⁺) and zinc ion (Zn²⁺) co-insertion model is put forward in this study to elucidate the capacity origin of an aqueous zinc ion battery (ZIB) based on a heavily loaded (∼15 mg cm^-2) cathode, which consists of Na₂V₆O₁₆·3H₂O (NVO) embedded particularly in the macropores of activated carbon cloth (ACC), coupled with a highly stable Zn/In anode. The confinement effect of these porous channels not only prevents the detachment of NVO from ACC but also well mitigates its volume change resulting from H⁺ and Zn²⁺ co-intercalation, which collectively render the stability of NVO/ACC markedly enhanced. Moreover, the bicontinuous structure of NVO/ACC, as a result of the self-interlacing of intrapore NVO, which is first engineered into the nanobelts, and their interlocking with the carbon fibers of ACC, simultaneously giving rise to a solid and a holey framework, is favorable to the electron and ion transport throughout the entire electrode. The synergistic effect of such facile charge transfer kinetics and the high packing density of NVO in the cathode endows ZIBs with not only a good rate performance but also an exceptional areal capacity amounting to 4.6 mAh cm^-2, far surpassing those reported for additional vanadium-based counterparts reported in the literature.

Surface and Interface Engineering for the Catalysts of Electrocatalytic CO2 Reduction

The massive use of fossil fuels releases a great amount of CO₂ , which substantially contributes to the global warming. For the global goal of putting CO₂ emission under control, effective utilization of CO₂ is particularly meaningful. Electrocatalytic CO₂ reduction reaction (eCO₂ RR) has great potential in CO₂ utilization, because it can convert CO₂ into valuable carbon-containing chemicals and feedstock using renewable electricity. The catalyst design for eCO₂ RR is a key challenge to achieving efficient conversion of CO₂ to fuels and useful chemicals. For a typical heterogeneous catalyst, surface and interface engineering is an effective approach to enhance reaction activity. Herein, the development and research progress in CO₂ catalysts with focus on surface and interface engineering are reviewed. First, the fundaments of eCO₂ RR is briefly discussed from the reaction mechanism to performance evaluation methods, introducing the role of the surface and interface engineering of electrocatalyst in eCO₂ RR. Then, several routes to optimize the surface and interface of CO₂ electrocatalysts, including morphology, dopants, atomic vacancies, grain boundaries, surface modification, etc., are reviewed and representative examples are given. At the end of this review, we share our personal views in future research of eCO₂ RR.

Electrochemical conversion of CO2 to value-added chemicals over bimetallic Pd-based nanostructures: Recent progress and emerging trends

Electrochemical conversion of CO₂ to fuels and chemicals as a sustainable solution for waste transformation has garnered tremendous interest to combat the fervent issue of the prevailing high atmospheric CO₂ concentration while contributing to the generation of sustainable energy. Monometallic palladium (Pd) has been shown promising in electrochemical CO₂ reduction, producing formate or CO depending on applied potentials. Recently, bimetallic Pd-based materials strived to fine-tune the binding affinity of key intermediates is a prominent strategy for the desired product formation from CO₂ reduction. Herein, the recent emerging trends on bimetallic Pd-based electrocatalysts are reviewed, including fundamentals of CO₂ electroreduction and material engineering of bimetallic Pd-electrocatalysts categorized by primary products. Modern analytical techniques on these novel electrocatalysts are also thoroughly studied to get insights into reaction mechanisms. Lastly, we deliberate over the challenges and prospects for Pd-based catalysts for electrochemical CO₂ conversion.

Steering surface reconstruction of copper with electrolyte additives for CO2 electroreduction

Electrocatalytic CO₂ reduction to value-added hydrocarbon products using metallic copper (Cu) catalysts is a potentially sustainable approach to facilitate carbon neutrality. However, Cu metal suffers from unavoidable and uncontrollable surface reconstruction during electrocatalysis, which can have either adverse or beneficial effects on its electrocatalytic performance. In a break from the current catalyst design path, we propose a strategy guiding the reconstruction process in a favorable direction to improve the performance. Typically, the controlled surface reconstruction is facilely realized using an electrolyte additive, ethylenediamine tetramethylenephosphonic acid, to substantially promote CO₂ electroreduction to CH₄ for commercial polycrystalline Cu. As a result, a stable CH₄ Faradaic efficiency of 64% with a partial current density of 192 mA cm⁻², thus enabling an impressive CO₂-to-CH₄ conversion rate of 0.25 µmol cm⁻² s⁻¹, is achieved in an alkaline flow cell. We believe our study will promote the exploration of electrochemical reconstruction and provide a promising route for the discovery of high-performance electrocatalysts.

Cu metal suffers from unavoidable and uncontrollable surface reconstruction during electrocatalysis. The authors here guide the reconstruction process in a favorable direction using trace amount of electrolyte additives, promoting CO₂ electroreduction to CH₄.

Effects of the Catalyst Dynamic Changes and Influence of the Reaction Environment on the Performance of Electrochemical CO2 Reduction

Electrochemical reduction of carbon dioxide (CO₂ ) is substantially researched due to its potential for storing intermittent renewable electricity and simultaneously helping mitigating the pressing CO₂ emission concerns. The major challenge of electrochemical CO₂ reduction lies on having good controls of this reaction due to its complicated reaction networks and its unusual sensitivity to the dynamic changes of the catalyst structure (chemical states, compositions, facets and morphology, etc.), and to the non-catalyst components at the electrode/electrolyte interface, in another word the reaction environments. To date, a comprehensive analysis on the interplays between the above catalyst-dynamic-changes/reaction environments and the CO₂ reduction performance is rare, if not none. In this review, the catalyst dynamic changes observed during the catalysis are discussed based on the recent reports of electrochemical CO₂ reduction. Then, the above dynamic changes are correlated to their effects on the catalytic performance. The influences of the reaction environments on the performance of CO₂ reduction are also discussed. Finally, some perspectives on future investigations are offered with the aim of understanding the origins of the effects from the catalyst dynamic changes and the reaction environments, which will allow one to better control the CO₂ reduction toward the desired products.

Bridge Sites of Au Surfaces Are Active for Electrocatalytic CO2 Reduction

Prior in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) studies of electrochemical CO2 reduction catalyzed by Au, one of the most selective and active electrocatalysts to produce CO from CO2, suggest that the reaction proceeds solely on the top sites of the Au surface. This finding is worth updating with an improved spectroelectrochemical system where in situ IR measurements can be performed under real reaction conditions that yield high CO selectivity. Herein, we report the preparation of an Au-coated Si ATR crystal electrode with both high catalytic activity for CO2 reduction and strong surface enhancement of IR signals validated in the same spectroelectrochemical cell, which allows us to probe the adsorption and desorption behavior of bridge-bonded *CO species (*COB). We find that the Au surface restructures irreversibly to give an increased number of bridge sites for CO adsorption within the initial tens of seconds of CO2 reduction. By studying the potential-dependent desorption kinetics of *COB and quantifying the steady-state surface concentration of *COB under reaction conditions, we further show that *COB are active reaction intermediates for CO2 reduction to CO on this Au electrode. At medium overpotential, as high as 38% of the reaction occurs on the bridge sites.

Selective, Stable Production of Ethylene Using a Pulsed Cu-Based Electrode

Ethylene (C₂H₄) is an important product in carbon dioxide electroreduction (CO₂RR) because of the essential role it plays in chemical industry. While several strategies have been proposed to tune the selectivity of Cu-based catalysts in order to achieve high C₂H₄ faradaic efficiency, maintaining high selectivity toward C₂H₄ in CO₂RR remains an unresolved problem hampering the deployment of CO₂ conversion technology due to the lack of stable electrocatalysts. Here, we develop a facile method to deposit a layer of Cu₂O on Cu foil by an electrochemical pulsed potential treatment. This method is capable to easily scale up and synthesize multiple electrodes in one step. After the synthesis, the pulsed copper foil, denoted as P-Cu, exhibits good C₂H₄ faradaic efficiency of ∼50% in CO₂RR at a potential around -1.0 V vs. RHE. The C₂H₄ selectivity is also found to be quantitatively correlated with the roughness factor (RF) of Cu-based catalysts. More importantly, for the first time, we demonstrate that the P-Cu electrode is quite durable in CO₂RR to produce C₂H₄ for more than 6 months.

Photocatalytic activity study of ZnO modified with nitrogen–sulfur co-doped carbon quantum dots under visible light

Enhanced degradation rate of RhB under visible light by N,S-CQDs-modified ZnO.

Recent Advances in Interface Engineering for Electrocatalytic CO2 Reduction Reaction

Electrocatalytic CO₂ reduction reaction (CO₂RR) can store and transform the intermittent renewable energy in the form of chemical energy for industrial production of chemicals and fuels, which can dramatically reduce CO₂ emission and contribute to carbon-neutral cycle. Efficient electrocatalytic reduction of chemically inert CO₂ is challenging from thermodynamic and kinetic points of view. Therefore, low-cost, highly efficient, and readily available electrocatalysts have been the focus for promoting the conversion of CO₂. Very recently, interface engineering has been considered as a highly effective strategy to modulate the electrocatalytic performance through electronic and/or structural modulation, regulations of electron/proton/mass/intermediates, and the control of local reactant concentration, thereby achieving desirable reaction pathway, inhibiting competing hydrogen generation, breaking binding-energy scaling relations of intermediates, and promoting CO₂ mass transfer. In this review, we aim to provide a comprehensive overview of current developments in interface engineering for CO₂RR from both a theoretical and experimental standpoint, involving interfaces between metal and metal, metal and metal oxide, metal and nonmetal, metal oxide and metal oxide, organic molecules and inorganic materials, electrode and electrolyte, molecular catalysts and electrode, etc. Finally, the opportunities and challenges of interface engineering for CO₂RR are proposed.

Boosting carbon monoxide production during CO2 reduction reaction via Cu-Sb2O3 interface cooperation

Development of multiple-component catalyst materials is a new trend in electrochemical CO₂ reduction reaction (eCO₂RR). A new type of metal-oxide interaction is reported here to improve carbon monoxide production via synergistic effect between the CO₂-to hydrocarbon selective metal material and CO₂-to hydrogen generation oxide material. Cu/Sb₂O₃ material originates from the hetero-structured CuO/Sb₂O₃ by a facile two-step hydrolysis and precipitation method, cooperative to inhibit hydrogen evolution or methane product, achieving CO Faradaic efficiency to 92% in CO₂ saturated KCl electrolyte at -0.99 V with good stability. The formation of a stable *COOH intermediate by electronic and geometric effects via Cu and Sb₂O₃ are responsible to promote CO selectivity. Cu-Sb₂O₃ interface interaction also destabilizes the adsorption *H as well, an intermediate for H₂ evolution. This study proposes a versatile design strategy for construction and utilization of metal-oxide interface for eCO₂RR.

Low coordination number copper catalysts for electrochemical CO2 methanation in a membrane electrode assembly

The electrochemical conversion of CO2 to methane provides a means to store intermittent renewable electricity in the form of a carbon-neutral hydrocarbon fuel that benefits from an established global distribution network. The stability and selectivity of reported approaches reside below technoeconomic-related requirements. Membrane electrode assembly-based reactors offer a known path to stability; however, highly alkaline conditions on the cathode favour C-C coupling and multi-carbon products. In computational studies herein, we find that copper in a low coordination number favours methane even under highly alkaline conditions. Experimentally, we develop a carbon nanoparticle moderator strategy that confines a copper-complex catalyst when employed in a membrane electrode assembly. In-situ XAS measurements confirm that increased carbon nanoparticle loadings can reduce the metallic copper coordination number. At a copper coordination number of 4.2 we demonstrate a CO2-to-methane selectivity of 62%, a methane partial current density of 136 mA cm-2, and > 110 hours of stable operation.

Residual Chlorine Induced Cationic Active Species on a Porous Copper Electrocatalyst for Highly Stable Electrochemical CO2 Reduction to C2

Electrochemical carbon dioxide (CO₂ ) reduction reaction (CO₂ RR) is an attractive approach to deal with the emission of CO₂ and to produce valuable fuels and chemicals in a carbon-neutral way. Many efforts have been devoted to boost the activity and selectivity of high-value multicarbon products (C₂₊ ) on Cu-based electrocatalysts. However, Cu-based CO₂ RR electrocatalysts suffer from poor catalytic stability mainly due to the structural degradation and loss of active species under CO₂ RR condition. To date, most reported Cu-based electrocatalysts present stabilities over dozens of hours, which limits the advance of Cu-based electrocatalysts for CO₂ RR. Herein, a porous chlorine-doped Cu electrocatalyst exhibits high C₂₊ Faradaic efficiency (FE) of 53.8 % at -1.00 V versus reversible hydrogen electrode (V_RHE ). Importantly, the catalyst exhibited an outstanding catalytic stability in long-term electrocatalysis over 240 h. Experimental results show that the chlorine-induced stable cationic Cu⁰ /Cu⁺ species and the well-preserved structure with abundant active sites are critical to the high FE of C₂₊ in the long-term run of electrochemical CO₂ reduction.

Direct and continuous generation of pure acetic acid solutions via electrocatalytic carbon monoxide reduction

Electrochemical CO₂ or CO reduction to high-value C₂₊ liquid fuels is desirable, but its practical application is challenged by impurities from cogenerated liquid products and solutes in liquid electrolytes, which necessitates cost- and energy-intensive downstream separation processes. By coupling rational designs in a Cu catalyst and porous solid electrolyte (PSE) reactor, here we demonstrate a direct and continuous generation of pure acetic acid solutions via electrochemical CO reduction. With optimized edge-to-surface ratio, the Cu nanocube catalyst presents an unprecedented acetate performance in neutral pH with other liquid products greatly suppressed, delivering a maximal acetate Faradaic efficiency of 43%, partial current of 200 mA⋅cm^-2, ultrahigh relative purity of up to 98 wt%, and excellent stability of over 150 h continuous operation. Density functional theory simulations reveal the role of stepped sites along the cube edge in promoting the acetate pathway. Additionally, a PSE layer, other than a conventional liquid electrolyte, was designed to separate cathode and anode for efficient ion conductions, while not introducing any impurity ions into generated liquid fuels. Pure acetic acid solutions, with concentrations up to 2 wt% (0.33 M), can be continuously produced by employing the acetate-selective Cu catalyst in our PSE reactor.

Investigation of Electrolyte-Dependent Carbonate Formation on Gas Diffusion Electrodes for CO2 Electrolysis

The electrochemical reduction of CO₂ (ECO₂R) is a promising method for reducing CO₂ emissions and producing carbon-neutral fuels if long-term durability of electrodes can be achieved by identifying and addressing electrode degradation mechanisms. This work investigates the degradation of gas diffusion electrodes (GDEs) in a flowing, alkaline CO₂ electrolyzer via the formation of carbonate deposits on the GDE surface. These carbonate deposits were found to impede electrode performance after only 6 h of operation at current densities ranging from -50 to -200 mA cm^-2. The rate of carbonate deposit formation on the GDE surface was determined to increase with increasing electrolyte molarity and became more prevalent in K⁺-containing as opposed to Cs⁺-containing electrolytes. Electrolyte composition and concentration also had significant effects on the morphology, distribution, and surface coverage of the carbonate deposits. For example, carbonates formed in K⁺-containing electrolytes formed concentrated deposit regions of varying morphology on the GDE surface, while those formed in Cs⁺-containing electrolytes appeared as small crystals, well dispersed across the electrode surface. Both deposits occluding the catalyst layer surface and those found within the microporous layer and carbon fiber substrate of the electrode were found to diminish performance in ECO₂R, leading to rapid loss of CO production after ∼50% of the catalyst layer surface was occluded. Additionally, carbonate deposits reduced GDE hydrophobicity, leading to increased flooding and internal deposits within the GDE substrate. Electrolyte engineering-based solutions are suggested for improved GDE durability in future work.

Towards the Large-Scale Electrochemical Reduction of Carbon Dioxide

The severe increase in the CO2 concentration is a causative factor of global warming, which accelerates the destruction of ecosystems. The massive utilization of CO2 for value-added chemical production is a key to commercialization to guarantee both economic feasibility and negative carbon emission. Although the electrochemical reduction of CO2 is one of the most promising technologies, there are remaining challenges for large-scale production. Herein, an overview of these limitations is provided in terms of devices, processes, and catalysts. Further, the economic feasibility of the technology is described in terms of individual processes such as reactions and separation. Additionally, for the practical implementation of the electrochemical CO2 conversion technology, stable electrocatalytic performances need to be addressed in terms of current density, Faradaic efficiency, and overpotential. Hence, the present review also covers the known degradation behaviors and mechanisms of electrocatalysts and electrodes during electrolysis. Furthermore, strategic approaches for overcoming the stability issues are introduced based on recent reports from various research areas involved in the electrocatalytic conversion.

Grain-Boundary-Engineered La2CuO4 Perovskite Nanobamboos for Efficient CO2 Reduction Reaction

Electroreduction of carbon dioxide (CO₂RR) has been regarded as a promising approach to realize the production of useful fuels and to decrease greenhouse gas levels simultaneously, where high-efficiency catalysts are required. Herein, we report La₂CuO₄ nanobamboo (La₂CuO₄ NBs) perovskite with rich twin boundaries showing a high Faraday efficiency (FE) of 60% toward ethylene (C₂H₄), whereas bulk La₂CuO₄ exhibits a FE_CO of 91%. X-ray absorption spectroscopy (XAS) reveals that the Cu in La₂CuO₄ NBs is in the Cu²⁺ state, and no obvious change can be observed during the catalytic process, as monitored by in situ XAS. Density functional theory calculations reveal that the superior FE_C2H4 of La₂CuO₄ NBs originates from the active (113) surfaces with intrinsic strain. The formation of gap states annihilates the electron transfer barrier of C-C coupling, resulting in the high FE_C2H4. This work provides a new perspective for developing efficient perovskite catalysts via grain boundary engineering.

Three-Dimensional Cathodes for Electrochemical Reduction of CO2: From Macro- to Nano-Engineering

Rising anthropogenic CO2 emissions and their climate warming effects have triggered a global response in research and development to reduce the emissions of this harmful greenhouse gas. The use of CO2 as a feedstock for the production of value-added fuels and chemicals is a promising pathway for development of renewable energy storage and reduction of carbon emissions. Electrochemical CO2 conversion offers a promising route for value-added products. Considerable challenges still remain, limiting this technology for industrial deployment. This work reviews the latest developments in experimental and modeling studies of three-dimensional cathodes towards high-performance electrochemical reduction of CO2. The fabrication-microstructure-performance relationships of electrodes are examined from the macro- to nanoscale. Furthermore, future challenges, perspectives and recommendations for high-performance cathodes are also presented.

A Corrosion-Resistant and Dendrite-Free Zinc Metal Anode in Aqueous Systems

Rechargeable aqueous zinc (Zn) ion-based energy storage systems have been reviving recently because of their low cost and high safety merits; however, they still suffer from the problems of corrosion and dendrite growth on Zn metal anodes that cause gas generation and early battery failure. Unfortunately, the corrosion problem has not received sufficient attention until now. Here, it is pioneeringly demonstrated that decorating the Zn surface with a dual-functional metallic indium (In) layer, acting as both a corrosion inhibitor and a nucleating agent, is a facile but effective strategy to suppress both drastic corrosion and dendrite growth. Symmetric cells assembled with the treated Zn electrodes can sustain up to 1500 h of plating/stripping cycles with an ultralow voltage hysteresis (54 mV), and a 5000 cycle-life is achieved for a prototype full cell. This work will instigate the further development of aqueous metal-based energy storage systems.

Magnesium oxide anchored into a hollow carbon sphere realizes synergistic adsorption and activation of CO2 for electrochemical reduction

We report the synergistic adsorption and activation of CO₂ by using magnesium oxide anchored into a hollow carbon sphere (MgO/HCS) as an efficient catalyst for electrochemical reduction of CO₂ (ERC). The MgO/HCS catalyst exhibits a high selectivity for CO production with a faradaic efficiency of 81.7% at -1.0 V vs. RHE and a partial current density (PCD) of 16.7 mA cm^-2 in aqueous electrolyte.

Stability and Degradation Mechanisms of Copper-Based Catalysts for Electrochemical CO2 Reduction

To date, copper is the only monometallic catalyst that can electrochemically reduce CO₂ into high value and energy-dense products, such as hydrocarbons and alcohols. In recent years, great efforts have been directed towards understanding how its nanoscale structure affects activity and selectivity for the electrochemical CO₂ reduction reaction (CO₂ RR). Furthermore, many attempts have been made to improve these two properties. Nevertheless, to advance towards applied systems, the stability of the catalysts during electrolysis is of great significance. This aspect, however, remains less investigated and discussed across the CO₂ RR literature. In this Minireview, the recent progress on understanding the stability of copper-based catalysts is summarized, along with the very few proposed degradation mechanisms. Finally, our perspective on the topic is given.

Synergy effects on Sn-Cu alloy catalyst for efficient CO2 electroreduction to formate with high mass activity

To acquire the synergy effects between Sn and Cu for the jointly high Faradaic efficiency and current density, we develop a novel strategy to design the Sn-Cu alloy catalyst via a decorated co-electrodeposition method for CO₂ electroreduction to formate. The Sn-Cu alloy shows high formate Faradaic efficiency of 82.3% ± 2.1% and total C₁ products Faradaic efficiency of 90.0% ± 2.7% at -1.14 V vs. reversible hydrogen electrode (RHE). The current density and mass activity of formate reach as high as (79.0 ± 0.4) mA cm^-2 and (1490.6 ± 7.5) mA mg^-1 at -1.14 V vs. RHE. Theoretical calculations suggest that Sn-Cu alloy can obtain high Faradaic efficiency for CO₂ electroreduction by suppressing the competitive hydrogen evolution reaction and that the formate formation follows the path of CO₂ → HCOO* → HCOOH. The stepped (2 1 1) surface of Sn-Cu alloy is beneficial towards selective formate production.

Durable Cathodes and Electrolyzers for the Efficient Aqueous Electrochemical Reduction of CO2

The world emits over 14 gigatons of CO₂ in excess of what can be remediated by natural processes annually, contributing to rising atmospheric CO₂ levels and increasing global temperatures. The electrochemical reduction of CO₂ (CO₂ RR) to value-added chemicals and fuels has been proposed as a method for reusing these excess anthropogenic emissions. While state-of-the-art CO₂ RR systems exhibit high current densities and faradaic efficiencies, research on long-term electrode durability, necessary for this technology to be implemented commercially, is lacking. Previous reviews have focused mainly on the CO₂ electrolyzer performance without considering durability. In this Review, the need for research into high-performing and durable CO₂ RR systems is stressed by summarizing the state-of-the-art with respect to durability. Various failure modes observed are also reported and a protocol for standard durability testing of CO₂ RR systems is proposed.

In Situ Reconstruction of a Hierarchical Sn-Cu/SnOx Core/Shell Catalyst for High-Performance CO2 Electroreduction

The electrochemical CO₂ reduction reaction (CO₂ RR) to give C₁ (formate and CO) products is one of the most techno-economically achievable strategies for alleviating CO₂ emissions. Now, it is demonstrated that the SnO_x shell in Sn_2.7 Cu catalyst with a hierarchical Sn-Cu core can be reconstructed in situ under cathodic potentials of CO₂ RR. The resulting Sn_2.7 Cu catalyst achieves a high current density of 406.7±14.4 mA cm^-2 with C₁ Faradaic efficiency of 98.0±0.9 % at -0.70 V vs. RHE, and remains stable at 243.1±19.2 mA cm^-2 with a C₁ Faradaic efficiency of 99.0±0.5 % for 40 h at -0.55 V vs. RHE. DFT calculations indicate that the reconstructed Sn/SnO_x interface facilitates formic acid production by optimizing binding of the reaction intermediate HCOO* while promotes Faradaic efficiency of C₁ products by suppressing the competitive hydrogen evolution reaction, resulting in high Faradaic efficiency, current density, and stability of CO₂ RR at low overpotentials.

Selective reduction of CO to acetaldehyde with CuAg electrocatalysts

Electrochemical CO reduction can serve as a sequential step in the transformation of CO₂ into multicarbon fuels and chemicals. In this study, we provide insights on how to steer selectivity for CO reduction almost exclusively toward a single multicarbon oxygenate by carefully controlling the catalyst composition and its surrounding reaction conditions. Under alkaline reaction conditions, we demonstrate that planar CuAg electrodes can reduce CO to acetaldehyde with over 50% Faradaic efficiency and over 90% selectivity on a carbon basis at a modest electrode potential of -0.536 V vs. the reversible hydrogen electrode. The Faradaic efficiency to acetaldehyde was further enhanced to 70% by increasing the roughness factor of the CuAg electrode. Density functional theory calculations indicate that Ag ad-atoms on Cu weaken the binding energy of the reduced acetaldehyde intermediate and inhibit its further reduction to ethanol, demonstrating that the improved selectivity to acetaldehyde is due to the electronic effect from Ag incorporation. These findings will aid in the design of catalysts that are able to guide complex reaction networks and achieve high selectivity for the desired product.

Self-Supported Nanoporous Au3 Cu Electrode with Enriched Gold on Surface for Efficient Electrochemical Reduction of CO2

The key to the electrochemical conversion of CO₂ lies in the development of efficient electrocatalysts with ease of operation, good conductivity, and rich active sites that fulfil the desired reaction direction and selectivity. Herein, an oxidative etching of Au₂₀ Cu₈₀ alloy is used for the synthesis of a nanoporous Au₃ Cu alloy, representing a facile strategy for tuning the surface electronic properties and altering the adsorption behavior of the intermediates. HRTEM, XPS, and EXAFS results reveal that the curved surface of the synthesized nanoporous Au₃ Cu is rich in gold with unsaturated coordination conditions. It can be used directly as a self-supported electrode for CO₂ reduction, and exhibits high Faradaic efficiency (FE) of 98.12 % toward CO at a potential of -0.7 V versus the reversible hydrogen electrode (RHE). The FE is 1.47 times that over the as-made single nanoporous Au. Density functional theory reveals that *CO has a relatively long distance on the surface of nanoporous Au₃ Cu, making desorption of CO easier and avoiding CO poisoning. The Hirshfeld charge distribution shows that the Au atoms have a negative charge and the Cu atoms exhibit a positive charge, which separately bond to the C atom and O atom in the *COOH intermediate through a bidentate mode. This affords the lowest *COOH adsorption free energy and low desorption energy for CO molecules.