Fine AgPd Nanoalloys Achieving Size and Ensemble Synergy for High-Efficiency CO2 to CO Electroreduction

Alloying the active metal with a second metal is an effective way to tailor the adsorption of reaction intermediates through an ensemble effect. Herein, based on theoretical calculations validating that the ensemble sites composed of Ag and Pd atoms could reduce the energy gap for *COOH and *CO intermediates generated during electrocatalytic CO₂ reduction reaction (eCO₂RR) by either weakening the CO adsorption or enhancing the COOH adsorption, a strategy to produce AgPd alloy nanoparticles with fine sizes for synergizing the ensemble effect and size leverage toward high CO faradaic efficiency in eCO₂RR is reported. In particular, the AgPd alloy nanoparticles at an optimized Ag/Pd atomic ratio of 35/65 affords a maximum CO faradaic efficiency of 98.9% and a CO partial current density of 5.1 mA cm⁻² at the potential of −0.8 V (vs RHE) with satisfactory durability of up to 25 h, outperforming those of most Pd-based electrocatalysts recently reported and demonstrating great potential for further application in producing CO via eCO₂RR at ambient conditions.     

Enhanced Charge Transfer Kinetics for the Electroreduction of Carbon Dioxide on Silver Electrodes Functionalized with Cationic Surfactants

Cationic ammonium surfactants can be used together with a suitable catalyst to enhance the electroreduction of carbon dioxide (CO₂RR). However, the underlying reasons for the improvements are not yet well understood. In this study, it is shown that didodecyldimethylammonium bromide (DDAB; [(C₁₂H₂₅)₂N(CH₃)₂]Br), when added to the catholyte, can increase the rate of CO₂ reduction to CO on silver electrodes by 12-fold at −0.9 V versus reversible hydrogen electrode. More importantly, electrochemical impedance spectroscopy revealed that DDAB lowers the charge transfer resistance (R_CT) for CO₂RR on silver, and these changes can be correlated with enhancements in partial current densities of CO. Interestingly, when DDAB is added onto two other CO-producing metals, namely, zinc and gold, the CO₂RR charge transfer kinetics are improved only on Zn, but not on Au electrodes. By means of a semiempirical model combining density functional theory calculations and experimental data, it is concluded that DDAB generally strengthens the adsorption energies of the *COOH intermediate, which leads to enhanced CO production on silver and zinc, but not on gold.     

A New Strategy for Accelerating Dynamic Proton Transfer of Electrochemical CO2 Reduction at High Current Densities

Developing single-atom electrocatalysts with high activity and superior selectivity at a wide potential window for CO₂ reduction reaction (CO₂RR) still remains a great challenge. Herein, a porous Ni N C catalyst containing atomically dispersed Ni N₄ sites and nanostructured zirconium oxide (ZrO₂@Ni-NC) synthesized via a post-synthetic coordination coupling carbonization strategy is reported. The as-prepared ZrO₂@Ni-NC exhibits an initial potential of −0.3 V, maximum CO Faradaic efficiency (F.E.) of 98.6% ± 1.3, and a low Tafel slope of 71.7 mV dec⁻¹ in electrochemical CO₂RR. In particular, a wide potential window from −0.7 to −1.4 V with CO F.E. of above 90% on ZrO₂@Ni-NC far exceeds those of recently developed state-of-the-art CO₂RR electrocatalysts based on Ni N moieties anchored carbon. In a flow cell, ZrO₂@Ni-NC delivers a current density of 200 mA cm⁻² with a superior CO selectivity of 96.8% at −1.58 V in a practical scale. A series of designed experiments and structural analyses identify that the isolated Ni N₄ species act as real active sites to drive the CO₂RR reaction and that the nanostructured ZrO₂ largely accelerates the protonation process of *CO₂⁻ to *COOH intermediate, thus significantly reducing the energy barrier of this rate-determining step and boosting whole catalytic performance.     

Nanoscale Management of CO Transport in CO2 Electroreduction: Boosting Faradaic Efficiency to Multicarbon Products via Nanostructured Tandem Electrocatalysts

Tandem catalysis presents a promising strategy to improve the selectivity toward multicarbon products in the electrocatalytic carbon dioxide reduction reaction (CO₂RR). For CO₂RR, CO is a critical intermediate for producing multicarbon products. However, the management of CO localization and CO diffusion remains underexplored despite its critical role. Herein, a 3D tandem catalyst electrode with silver nanoparticles (Ag NPs) is designed to generate CO as an intermediate product within a copper (Cu) nanoneedle array. Via this nanostructured design, CO₂ forms C²⁺ products with a high Faradaic efficiency (FEC²⁺) of 64% in an H-cell and 70% in a flow cell with a current density of 350 mA cm⁻². These figures-of-merit are currently among the top literature reports. More importantly, in situ Raman spectroscopy and finite-element method calculations are employed to elucidate the origins of enhanced selectivity. These approaches reveal the crucial role of prolonging the CO diffusion path length for improving CO utilization during CO₂ conversion with tandem catalyst systems. The favorable CO2RR FEC²⁺ in two distinct environments (H-cell and flow cell) further corroborates that this effect is not limited to a particular reactor environment. Overall, this study provides new insights for designing tandem catalysts for improved CO₂RR selectivity to C²⁺ products.     

Molecular Modulation of Sequestered Copper Sites for Efficient Electroreduction of Carbon Dioxide to Methane

The sustainable production of methane (CH₄) via the electrochemical conversion of carbon dioxide (CO₂) is an appealing approach to simultaneously mitigating carbon emissions and achieving energy storage in chemical bonds. Copper (Cu) is a unique material to produce hydrocarbons and oxygenates. However, selective methane generation on Cu remains a great challenge due to the preferential *CO dimerization pathway toward multi-carbon (C₂₊) products at neighboring catalytic sites. Herein, a conjugated copper phthalocyanine polymer (CuPPc) is designed by a facile solid-state method for highly selective CO₂-to-CH₄ conversion. The spatially isolated Cu N₄ sites in CuPPc favor the *CO protonation to generate the key *CHO intermediate, thus significantly promoting the formation of CH₄. As a result, the CuPPc catalyst exhibits a high CH₄ Faradaic efficiency of 55% and a partial current density of 18 mA cm⁻² at −1.25 V versus the reversible hydrogen electrode. It also stably operates for 12 h. This study may offer a new solution to regulating the chemical environment of the active sites for the development of highly efficient copper-based catalysts for electrochemical CO₂ reduction.     

Highly Dispersed NiO Clusters Induced Electron Delocalization of Ni?N?C Catalysts for Enhanced CO2 Electroreduction

Oxygen-regulated Ni-based single-atom catalysts (SACs) show great potential in accelerating the kinetics of electrocatalytic CO₂ reduction reaction (CO₂RR). However, it remains a challenge to precisely control the coordination environment of Ni O moieties and achieve high activity at high overpotentials. Herein, a facile carbonization coupled oxidation strategy is developed to mass produce NiO clusters-decorated Ni N C SACs that exhibit a high Faradaic efficiency of CO (maximum of 96.5%) over a wide potential range (−0.9 to −1.3 V versus reversible hydrogen electrode) and a high turnover frequency for CO production of 10 120 h⁻¹ even at the high overpotential of 1.19 V. Density functional theory calculations reveal that the highly dispersed NiO clusters induce electron delocalization of active sites and reduce the energy barriers for *COOH intermediates formation from CO₂, leading to an enhanced reaction kinetics for CO production. This study opens a new universal pathway for the construction of oxygen-regulated metal-based SACs for various catalytic applications.     

Hybrid Catalyst Coupling Zn Single Atoms and CuNx Clusters for Synergetic Catalytic Reduction of CO2

Reverse water-gas shift (RWGS) reaction is the initial and necessary step of CO₂ hydrogenation to high value-added products, and regulating the selectivity of CO is still a fundamental challenge. In the present study, an efficient catalyst (CuZnN_x@C-N) composed by Zn single atoms and Cu clusters stabilized by nitrogen sites is reported. It contains saturated four-coordinate Zn-N₄ sites and low valence CuN_x clusters. Monodisperse Zn induces the aggregation of pyridinic N to form Zn-N₄ and N₄ structures, which show strong Lewis basicity and has strong adsorption for *CO₂ and *COOH intermediates, but weak adsorption for *CO, thus greatly improves the CO₂ conversion and CO selectivity. The catalyst calcined at 700 °C exhibits the highest CO₂ conversion of 43.6% under atmospheric pressure, which is 18.33 times of Cu-ZnO and close to the thermodynamic equilibrium conversion rate (49.9%) of CO₂. In the catalytic process, CuN_x not only adsorbs and activates H₂, but also cooperates with the adjacent Zn-N₄ and N₄ structures to jointly activate CO₂ molecules and further promotes the hydrogenation of CO₂. This synergistic mechanism will provide new insights for developing efficient hydrogenation catalysts.     

Cu/Cu2O Interconnected Porous Aerogel Catalyst for Highly Productive Electrosynthesis of Ethanol from CO2

Use of Cu and Cu⁺ is one of the most promising approaches for the production of C₂ products by the electrocatalytic CO₂ reduction reaction (CO₂RR) because it can facilitate CO₂ activation and C C dimerization. However, the selective electrosynthesis of C₂₊ products on Cu⁰ Cu⁺ interfaces is critically limited due to the low electrocatalytic production of ethanol relative to ethylene. In this study, a novel porous Cu/Cu₂O aerogel network is introduced to afford high ethanol productivity by the electrocatalytic CO₂RR. The aerogel is synthesized by a simple chemical redox reaction of a precursor and a reducing agent. CO₂RR results reveal that the Cu/Cu₂O aerogel produces ethanol as the major product, exhibiting a Faradaic efficiency (FE_EtOH) of 41.2% and a partial current density (J_EtOH) of 32.55 mA cm⁻² in an H-cell reactor. This is the best electrosynthesis performance for ethanol production reported thus far. Electron microscopy and electrochemical analysis results reveal that this dramatic increase in the electrosynthesis performance for ethanol can be attributed to a large number of Cu⁰ Cu⁺ interfaces and an increase of the local pH in the confined porous aerogel network structure with a high-surface-area.     

Hierarchical Cross-Linked Carbon Aerogels with Transition Metal-Nitrogen Sites for Highly Efficient Industrial-Level CO2 Electroreduction

Developing highly efficient carbon aerogels (CA) electrocatalysts based on transition metal-nitrogen sites is critical for the CO₂ electroreduction reaction (CO₂RR). However, simultaneously achieving a high current density and high Faradaic efficiency (FE) still remains a big challenge. Herein, a series of unique 3D hierarchical cross-linked nanostructured CA with metal-nitrogen sites (M N, M = Ni, Fe, Co, Mn, Cu) is developed for efficient CO₂RR. An optimal CA/N-Ni aerogel, featured with unique hierarchical porous structure and highly exposed M-N sites, exhibits an unusual CO₂RR activity with a CO FE of 98% at −0.8 V. Notably, an industrial current density of 300 mA cm⁻² with a high FE of 91% is achieved on CA/N-Ni aerogel in a flow-cell reactor, which outperforms almost all previously reported M-N/carbon based catalysts. The CO₂RR activity of different CA/N-M aerogels can be arranged as Ni, Fe, Co, Mn, and Cu from high to low. In situ spectroelectrochemistry analyses validate that the rate-determining step in the CO₂RR is the formation of *COOH intermediate. A Zn CO₂ battery is further assembled with CA/N-Ni as the cathode, which shows a maximum power density of 0.5 mW cm⁻² and a superior rechargeable stability.     

Reaching the Fundamental Limitation in CO2 Reduction to CO with Single Atom Catalysts

The electrochemical CO₂ reduction reaction (CO₂RR) to value-added chemicals with renewable electricity is a promising method to decarbonize parts of the chemical industry. Recently, single metal atoms in nitrogen-doped carbon (MNC) have emerged as potential electrocatalysts for CO₂RR to CO with high activity and faradaic efficiency, although the reaction limitation for CO₂RR to CO is unclear. To understand the comparison of intrinsic activity of different MNCs, two catalysts are synthesized through a decoupled two-step synthesis approach of high temperature pyrolysis and low temperature metalation (Fe or Ni). The highly meso-porous structure results in the highest reported electrochemical active site utilization based on in situ nitrite stripping; up to 59±6% for NiNC. Ex situ X-ray absorption spectroscopy (XAS) confirms the penta-coordinated nature of the active sites. The catalysts are amongst the most active in the literature for CO₂ reduction to CO. The density functional theory calculations (DFT) show that their binding to the reaction intermediates approximates to that of Au surfaces. However, it is found that the turnover frequencies (TOFs) of the most active catalysts for CO evolution converge, suggesting a fundamental ceiling to the catalytic rates.     

Cobalt−Iron Oxide Nanosheets for High‐Efficiency Solar‐Driven CO2−H2O Coupling Electrocatalytic Reactions

Solar‐driven electrochemical overall CO₂ splitting (OCO₂S) offers a promising route to store sustainable energy; however, its extensive implementation is hindered by the sluggish kinetics of two key reactions (i.e., CO₂ reduction reaction and oxygen evolution reaction (CO₂RR and OER, respectively)). Here, as dual‐functional catalysts, Co₂FeO₄ nanosheet arrays having high electrocatalytic activities toward CO₂RR and OER are developed. When the catalyst is applied to a complete OCO₂S system driven by a triple junction GaInP₂/GaAs/Ge photovoltaic cell, it shows a high photocurrent density of ≈13.1 mA cm^?2, corresponding to a remarkably high solar‐to‐CO efficiency of 15.5%. Density functional theory studies suggest that the Co sites in Co₂FeO₄ are favorable to the formation of *COOH and *O intermediates and thus account for its efficient bifunctional activities. The results will facilitate future studies for designing highly effective electrocatalysts and devices for OCO₂S.     

Understanding Boosted Selective CO2-to-CO Photoreduction with Pure Water Vapor over Hierarchical Biomass-Derived Carbon Matrix

Solar-driven CO₂ reduction reaction (CO₂RR) with water into carbon-neutral fuels is of great significance but remains challenging due to thermodynamic stability and kinetic inertness of CO₂. Biomass-derived nitrogen-doped carbon (N-C_b) have been considered as promising earth-abundant photocatalysts for CO₂RR, although their activities are not ideal and the reaction mechanism is still unclear. Herein, an efficient catalyst is developed for CO₂-to-CO conversion realized on diverse N-C_b materials with hierarchical pore structures. It is demonstrated that the CO₂-to-CO conversion preferentially takes place on positively charged carbon atoms next to pyridinic-N using two representatives treated pollens with the largest difference in pyridinic-N density and N content as model photocatalysts. Systematic experimental results indicate that surface local electric field originating from charge separation can be boosted by hierarchical pore structures, doped N, as well as pyridinic-N. Mechanistic studies reveal that positively charged carbon atoms next to pyridinic-N serve as active sites for CO₂RR, reduce the energy barrier on the formation of CO*, and facilitate the CO₂RR performance. All these benefits cooperatively contribute to treated chrysanthemum pollen catalyst exhibiting excellent CO formation rate of 203.2 µmol h⁻¹ g⁻¹ with 97.2% selectivity in pure water vapor. These results provide a new perspective into CO₂RR on N-C_b, which shall guide the design of nature-based photocatalysts for high-performance solar-fuel generation.     

Pre-Activation of CO2 at Cobalt Phthalocyanine-Mg(OH)2 Interface for Enhanced Turnover Rate

Cobalt phthalocyanine (CoPc) anchored on heterogeneous scaffold has drawn great attention as promising electrocatalyst for carbon dioxide reduction reaction (CO₂RR), but the molecule/substrate interaction is still pending for clarification and optimization to maximize the reaction kinetics. Herein, a CO₂RR catalyst is fabricated by affixing CoPc onto the Mg(OH)₂ substrate primed with conductive carbon, demonstrating an ultra-low overpotential of 0.31 ± 0.03 V at 100 mA cm⁻² and high faradaic efficiency of >95% at a wide current density range for CO production, as well as a heavy-duty operation at 100 mA cm⁻² for more than 50 h in a membrane electrode assembly. Mechanistic investigations employing in situ Raman and attenuated total reflection surface-enhanced infrared absorption spectroscopy unravel that Mg(OH)₂ plays a pivotal role to enhance the CO₂RR kinetics by facilitating the first-step electron transfer to form anionic *CO₂⁻ intermediates. DFT calculations further elucidate that introducing Lewis acid sites help to polarize CO₂ molecules absorbed at the metal centers of CoPc and consequently lower the activation barrier. This work signifies the tailoring of catalyst-support interface at molecular level for enhancing the turnover rate of CO₂RR.     

Identifying Active Sites of Nitrogen‐Doped Carbon Materials for the CO2 Reduction Reaction

Nitrogen‐doped carbon materials are proposed as promising electrocatalysts for the carbon dioxide reduction reaction (CRR), which is essential for renewable energy conversion and environmental remediation. Unfortunately, the unclear cognition on the CRR active site (or sites) hinders further development of high‐performance electrocatalysts. Herein, a series of 3D nitrogen‐doped graphene nanoribbon networks (N‐GRW) with tunable nitrogen dopants are designed to unravel the site‐dependent CRR activity/selectivity. The N‐GRW catalyst exhibits superior CO₂ electrochemical reduction activity, reaching a specific current of 15.4 A g_catalyst^?1 with CO Faradaic efficiency of 87.6% at a mild overpotential of 0.49 V. Based on X‐ray photoelectron spectroscopy measurements, it is experimentally demonstrated that the pyridinic N site in N‐GRW serves as the active site for CRR. In addition, the Gibbs free energy calculated by density functional theory further illustrates the pyridinic N as a more favorable site for the CO₂ adsorption, *COOH formation, and *CO removal in CO₂ reduction.     

Recent Progresses in Electrochemical Carbon Dioxide Reduction on Copper-Based Catalysts toward Multicarbon Products

Electrochemical carbon dioxide reduction reaction (CO₂RR) offers a promising way of effectively converting CO₂ to value-added chemicals and fuels by utilizing renewable electricity. To date, the electrochemical reduction of CO₂ to single-carbon products, especially carbon monoxide and formate, has been well achieved. However, the efficient conversion of CO₂ to more valuable multicarbon products (e.g., ethylene, ethanol, n-propanol, and n-butanol) is difficult and still under intense investigation. Here, recent progresses in the electrochemical CO₂ reduction to multicarbon products using copper-based catalysts are reviewed. First, the mechanism of CO₂RR is briefly described. Then, representative approaches of catalyst engineering are introduced toward the formation of multicarbon products in CO₂RR, such as composition, morphology, crystal phase, facet, defect, strain, and surface and interface. Subsequently, key aspects of cell engineering for CO₂RR, including electrode, electrolyte, and cell design, are also discussed. Finally, recent advances are summarized and some personal perspectives in this research direction are provided.     

Selenium‐Doped Hierarchically Porous Carbon Nanosheets as an Efficient Metal‐Free Electrocatalyst for CO2 Reduction

Electrochemical carbon dioxide reduction reaction (CO₂RR) provides a promising pathway for both decreasing atmospheric CO₂ concentration and producing valuable carbon‐based fuels. To explore efficient and cost‐effective catalysts for electrochemical CO₂RR is of great importance, but remains challenging. Se‐doped carbon nanosheets (Se‐CNs) with a micro‐, meso‐, and macroporous structure are proposed for electrochemical CO₂RR. Such an electrocatalyst combines the advantages of Se optimized active sites, hierarchical pores for facilitating reactant or ion penetration, transport and reaction, and large surface area for more accessible active sites. This Se‐CNs electrocatalyst exhibits over 11‐times enhanced partial current density of CO than the CNs without Se doping and high selectivity (90%) for CO₂ electroreduction to CO at a low potential of ?0.6 V versus the reversible hydrogen electrode (vs RHE). Density function theoretical calculations reveal that the Se introduction in CNs lowers the free energy barrier of CO₂RR and inhibits hydrogen evolution reaction effectively, thus improving the selectivity for CO₂ reduction to CO. This work presents a new member of the metal‐free electrocatalyst family, which is easily prepared, low cost, adjustable, and highly efficient for CO₂RR.     

Efficient Electrocatalytic Reduction of CO2 to Ethanol Enhanced by Spacing Effect of Cu?Cu in Cu2-xSe Nanosheets

It is highly desired yet challenging to strategically steer carbon dioxide (CO₂) electroreduction reaction (CO₂ER) toward ethanol (EtOH) with high activity, which provides a promising way for intermittent renewable energy reservation. Controlling spatial distance between the adjoining active centers and promoting the C C coupling progress are crucial to realize this purpose. Herein, ultrathin 2D Cu_2-xSe is prepared with abundant Se vacancies, where the spatial distance between the Cu Cu around the Se vacancies is effectively shortened because of the lattice stress. Besides, the moderate spatial distance induced by Se vacancies can significantly decrease the Gibbs free energy of asymmetric *CO *CHO coupling progress, effectively change the local charge distribution, decrease the valence state of Cu atoms and increase the electron-donating capacity of the dual active sites. Combining experimental observations and density functional theory   simulations, the Cu Cu dual sites with spatial distance of 2.51 Å in V_Se-Cu_2-xSe sample can catalyze CO₂ER to EtOH with high selectivity in a potential range from −0.4 to −1.6 V, and reach the highest faradaic efficiency of 68.1% at −0.8 V. This work reveals the influence of spacing effect on ethanol selectivity, and provides a new idea for future design of catalysts with chain elongation reaction, which can bring extensive attention.     

In Situ Structure Refactoring of Bismuth Nanoflowers for Highly Selective Electrochemical Reduction of CO2 to Formate

The electrocatalytic CO₂ reduction reaction (CO₂RR) has been considered a promising route toward carbon neutrality and renewable energy conversion. At present, most bismuth (Bi) based electrocatalysts are adopted to reduce CO₂ to formate (HCOOH). However, the mechanism of different Bi nanostructures on the electrocatalytic performance requires more detailed exposition. Herein, a combined chemical replacement and electrochemical reduction process is reported to realize in situ morphology reconstruction from Bi@Bi₂O₃ nanodendrites (Bi@Bi₂O₃-NDs) to Bi nanoflowers (Bi-NFs). The Bi@Bi₂O₃-NDs are proven to undergo a two-step transformation process to form Bi-NFs, aided by Bi₂O₂CO₃ as the intermediate in KHCO₃ solution. Extensive surface reconstruction of Bi@Bi₂O₃-NDs renders the realization of tailored Bi-NFs electrocatalyst that maximize the number of exposed active sites and active component (Bi⁰), which is conducive to the adsorption and activation of CO₂ and accelerated electron transfer process. The as-prepared Bi-NFs exhibit a Faradaic efficiency (FE_formate) of 92.3% at −0.9 V versus RHE and a high partial current density of 28.5 mA cm⁻² at −1.05 V versus RHE for the electroreduction of CO₂ to HCOOH. Moreover, the reaction mechanism is comprehensively investigated by in situ Raman analysis, which confirms that *OCHO is a key intermediate for the formation of HCOOH.     

Boosting Industrial-Level CO2 Electroreduction of N-Doped Carbon Nanofibers with Confined Tin-Nitrogen Active Sites via Accelerating Proton Transport Kinetics

The development of highly efficient robust electrocatalysts with low overpotential and industrial-level current density is of great significance for CO₂ electroreduction (CO₂ER), however the low proton transport rate during the CO₂ER remains a challenge. Herein, a porous N-doped carbon nanofiber confined with tin-nitrogen sites (Sn/NCNFs) catalyst is developed, which is prepared through an integrated electrospinning and pyrolysis strategy. The optimized Sn/NCNFs catalyst exhibits an outstanding CO₂ER activity with the maximum CO FE of 96.5%, low onset potential of −0.3 V, and small Tafel slope of 68.8 mV dec⁻¹. In a flow cell, an industrial-level CO partial current density of 100.6 mA cm⁻² is achieved. In situ spectroscopic analysis unveil the isolated Sn N site acted as active center for accelerating water dissociation and subsequent proton transport process, thus promoting the formation of intermediate *COOH in the rate-determining step for CO₂ER. Theoretical calculations validate pyrrolic N atom adjacent to the Sn N active species assisted reducing the energy barrier for *COOH formation, thus boosting the CO₂ER kinetics. A Zn-CO₂ battery is designed with the cathode of Sn/NCNFs, which delivers a maximum power density of 1.38 mW cm⁻² and long-term stability.     

Decoupling Interfacial Reactions at Anode and Cathode by Combining Online Electrochemical Mass Spectroscopy with Anode-Free Li-Metal Battery

It is essential to decouple the interfacial reactions taking place at the anode and cathode in rechargeable batteries. However, due to the reactive nature of Li, it is challenging to use Li-metal batteries (LMBs) protocol to decouple the interfacial reactions. The by-products from the anode or cathode become mixed in Li/NMC111 cells, which make decoupling interfacial reactions difficult. Here, reactions at electrodes are successfully decoupled and demystified using a protocol combining anode-free LMB (AFLMB) with online electrochemical mass spectroscopy. LiPF₆ in ethylene carbonate (EC)/diethyl carbonate (DEC) and EC/ethyl methyl carbonate (1:1 v/v%) electrolytes are used to compare interfacial reactions in Li/NMC111 and Cu/NMC111 cells. In Cu/NMC111, the evolution of CO₂, CO, and C₂H₄ gases at the initial stage of first charging is due to interfacial reactions at Cu surface due to solid–electrolyte-interphase formation. However, the evolution of CO₂ and CO gases at high voltage in the entire cycles is associated with chemical and/or electrochemical electrolyte oxidation at the cathode. This work paves a new concept to decouple interfacial reactions at electrodes for developing electrochemically stable electrolytes to improve the performance with the long-cycling life of AFLMBs and LMBs.