CO2 Batteries Research Articles

Oxygen-reduced surface-terminated MXenes as cathodes for enhanced reversible Li–CO2 batteries

Li–CO2 batteries have garnered global attention due to their dual attributes of high energy density and effective CO2 capture. However, they still face a formidable challenge in decomposing the discharge products Li2CO3, resulting in subpar battery performance. MXene has been proposed as a promising candidate owing to its high electrical conductivity and effective CO2 activation performance. Nevertheless, unavoidable surface terminations (such as –O and –OH) during synthesis strongly influence their catalytic properties, posing a significant hurdle for high-performance Li–CO2 batteries. Herein, a thermal annealing approach is proposed to control the surface termination groups of MXene to reduce the generation of lithium hydroxide byproducts, thereby accelerating Li2CO3 decomposition kinetics and enhancing the reversibility of the battery. The systematic annealing of MXene in the range of 500–800 °C confirmed optimal surface terminations at 500 °C (TC500). The TC500, when tested as a catalyst in a Li–CO2 battery, exhibited enhanced performance metrics, such as low voltage gap (1.98 V), high specific capacity (15,740.38 mA h g−1 at 100 mA g−1), and prolonged cycle stability (700 h at 200 mA g−1). The proposed work offers an effective strategy for regulating MXene surface termination groups via simple annealing treatments to achieve high-performance Li–CO2 batteries.

Routes to Bidirectional Cathodes for Reversible Aprotic Alkali Metal–CO2 Batteries

AbstractAprotic alkali metal–CO2 batteries (AAMCBs) have garnered significant interest owing to fixing CO2 and providing large energy storage capacity. The practical implementation of AAMCBs is constrained by the sluggish kinetics of the CO2 reduction reaction (CO2RR) and the CO2 evolution reaction (CO2ER). Because the CO2ER and CO2RR take place on the cathode, which connects the internal catalyst with the external environment. Building a bidirectional cathode with excellent CO2ER and CO2RR kinetics by optimizing the cathode's internal catalyst and environment has attracted most of the attention to improving the electrochemical performance of AAMCBs. However, there remains a lack of comprehensive understanding. This review aims to give a route to bidirectional cathodes for reversible AAMCBs, by systematically discussing engineering strategies of both the internal catalyst (atomic, nanoscopic, and macroscopic levels) and the external environment (photo, photo‐thermal, and force field). The CO2ER and CO2RR mechanisms and the “engineering strategies from internal catalyst to the external environment–cathode properties–CO2RR and CO2ER kinetics and mechanisms–batteries performance” relationship are elucidated by combining computational and experimental approaches. This review establishes a fundamental understanding for designing bidirectional cathodes and gives a route for developing reversible AAMCBs and similar metal–gas battery systems.

Photo-Energized MoS2/CNT Cathode for High-Performance Li–CO2 Batteries in a Wide-Temperature Range

HighlightsThe unique layered structure and excellent photoelectric properties of MoS2 facilitate the abundant generation and rapid transfer of photo-excited carriers, which accelerate the CO2 reduction and Li2CO3 decomposition upon illumination.MoS2-based photo-energized Li–CO2 battery displays ultra-low charge voltage of 3.27 V, high energy efficiency of 90.2%, superior cycling stability after 120 cycles and high rate capability.The low-temperature Li–CO2 battery achieves an ultra-low charge voltage of 3.4 V at –30 °C with a round-trip efficiency of 86.6%.

Regulating Spin Polarization via Axial Nitrogen Traction at Fe−N5 Sites Enhanced Electrocatalytic CO2 Reduction for Zn−CO2 Batteries

AbstractSingle Fe sites have been explored as promising catalysts for the CO2 reduction reaction to value‐added CO. Herein, we introduce a novel molten salt synthesis strategy for developing axial nitrogen‐coordinated Fe‐N5 sites on ultrathin defect‐rich carbon nanosheets, aiming to modulate the reaction pathway precisely. This distinctive architecture weakens the spin polarization at the Fe sites, promoting a dynamic equilibrium of activated intermediates and facilitating the balance between *COOH formation and *CO desorption at the active Fe site. Notably, the synthesized FeN5, supported on defect‐rich in nitrogen‐doped carbon (FeN5@DNC), exhibits superior performance in CO2RR, achieving a Faraday efficiency of 99 % for CO production (−0.4 V vs. RHE) in an H‐cell, and maintaining a Faraday efficiency of 98 % at a current density of 270 mA cm−2 (−1.0 V vs. RHE) in the flow cell. Furthermore, the FeN5@DNC catalyst is assembled as a reversible Zn−CO2 battery with a cycle durability of 24 hours. In situ IR spectroscopy and density functional theory (DFT) calculations reveal that the axial N coordination traction induces a transformation in the crystal field and local symmetry, therefore weakening the spin polarization of the central Fe atom and lowering the energy barrier for *CO desorption.

In situ ambient pressure x-ray photoelectron spectroscopy study on O2/H2O-assisted Na–CO2 batteries

Na–CO2 battery is considered a high-energy-density storage system with the ability to utilize CO2. However, unlike its Li counterpart, it suffers from an unclear reaction mechanism and poor battery performance. CO2 is an inert species and requires high activation energy. Moreover, the understanding of how additives such as O2 and H2O aid the cathode reaction remains lacking. Herein, the mechanism of the CO2 reduction reaction is unraveled through in situ ambient pressure X-ray photoelectron spectroscopy (APXPS). The oxidation states of the discharged products can be well revealed to understand the reactions. Unlike previous studies, a pure CO2 environment was found to have poor electrochemical activity. When additives, such as O2 and H2O, were introduced to the system, some Csp2 was formed. We propose that Csp2 should be attributed to the alkene formation as the decomposition product of ionic liquid, which serves as the electrolyte. The formation of elemental carbon as the discharge product is unlikely, which is in stark contrast to previous studies. As a result, the poor electrochemical activity of the pure CO2 system leads to the formation of CO, which escapes from the electrode surface and results in poor reversibility. Additives such as O2 and H2O are electrochemically active themselves, while CO2 participated in the reaction chemically, reducing the chemical reversibility. Therefore, a system without CO2 is more beneficial to the Na–air batteries.

Freestanding molybdenum carbide nanowires electrode for high specific capacity and superior rate performance Li–CO2 batteries

Li–CO2 batteries have attracted wide attention owing to unique CO2 capture ability and potential power source for Mars exploration. However, the practical application of Li–CO2 batteries are severely restricted by the sluggish reaction kinetics of 4–electron Li2CO3 as discharged products. Herein, we design efficient freestanding Mo2C nanowires electrode following low electron Li2C2O4–product route to achieve high–performance Li–CO2 batteries. More importantly, we propose a regulation and evolution mechanism of discharge products Li2C2O4 and Li2CO3 on Mo2C cathode in Li–CO2 battery with different discharge depths. Based on reasonable regulation of discharge products, Li–CO2 batteries with the Mo2C nanowires exhibit excellent electrochemical performance with an ultra–low overpotential 0.35 V at 0.05 mA cm–2 and a cycle life of 165 cycles below charge potential of 3.8 V. The Mo2C nanowires electrode also delivers high discharge capacity of 8.47 mAh cm–2 and superior rate capability compared to a conventional Mo2C cathode reported. Moreover, the superior flexibility and stability of the binder–free Mo2C nanowires electrode under different deformations assists in the development of wearable Li–CO2 batteries with safety and sustainability.

Revolutionizing RPAS logistics and reducing CO2 emissions with advanced RPAS technology for delivery systems

To manage remotely piloted aircraft system (RPAS) networks effectively, this research presents a multi-objective location-routing optimization model. This model integrates time window constraints, concurrent pick-up and delivery demands, and rechargeable battery functionality, and also introduces a standardized framework to clarify the RPAS CO2 emission model. These integrations significantly decrease battery consumption in Remotely Piloted Aircraft Systems (RPAS) and lower transportation costs, while also optimizing delivery times, reducing operational risks, and minimizing CO2 emissions. The model’s enhancement for optimizing delivery schedules takes into account uncertain traffic conditions, thus improving accuracy in dynamic environments and further contributing to environmental sustainability. Risk assessment employs the Specific Operations Risk Assessment (SORA) standard, adding a third objective function. This combination of the model, further enhance the efficiency and sustainability of RPAS operations, by optimizing delivery schedules, reducing CO2 emissions and battery consumption, and improving accuracy under dynamic conditions. Also, it make RPAS logistics more practical and effective in real-world applications. As result, the NSGA-II algorithm achieves significant reductions across all objectives: 33.3 % in cost, 6.48 % in time, 33.3 % in risk, and 35.7 % in battery usage within 250 generations. The use of the NSGA-II meta-heuristic method for validation enhances the credibility and practicality of the model. The optimization model’s performance over 250 generations shows rapid initial improvements in cost, time, risk, and battery usage, followed by stabilization, indicating efficient convergence and effective evolutionary computation. Also the findings show that with a CO2 emission rate of 3.773 × 104 kg of CO2 per Wh, highlighting the model’s efficiency and effectiveness.

A Rechargeable “Rocking Chair” Type Zn−CO2 Battery

AbstractRising global temperatures and critical energy shortages have spurred researches into CO2 fixation and conversion within the realm of energy storage such as Zn−CO2 batteries. However, traditional Zn−CO2 batteries employ double‐compartment electrolytic cells with separate carriers for catholytes and anolytes, diverging from the “rocking chair” battery mechanism. The specific energy of these conventional batteries is constrained by the solubility of discharge reactants/products in the electrolyte. Additionally, H2O molecules tend to trigger parasitic reactions at the electrolyte/electrode interfaces, undermining the long‐term stability of Zn anodes. In this report, we introduce an innovative “rocking chair” type Zn−CO2 battery that utilizes a weak‐acidic zinc trifluoromethanesulfonate aqueous electrolyte compatible with both cathode and anode. This design minimizes side reactions on the Zn surface and leverages the high catalytic activity of the cathode material, allowing the battery to achieve a substantial discharge capacity of 6734 mAh g−1 and maintain performance over 65 cycles. Moreover, the successful production of pouch cells demonstrates the practical applicability of Zn−CO2 batteries. Electrode characterizations confirm superior electrochemical reversibility, facilitated by solid discharge products of ZnCO3 and C. This work advances a “rocking chair” Zn−CO2 battery with an enhanced specific energy and a reversible pathway, providing a foundation for developing high‐performance metal‐CO2 batteries.

Advancements in covalent organic framework‐based nanocomposites: Pioneering materials for CO2 reduction and storage

AbstractThe persistent increase in atmospheric carbon dioxide (CO2) concentration poses a significant contemporary challenge. Contemporary chemistry is heavily focused on sustainable solutions, particularly the photo‐/electrocatalytic reduction of CO2 and its utilization for energy storage. Despite promising prospects, efficient chemical CO2 conversion faces obstacles such as ineffective CO2 uptake/activation and catalyst mass transport. Covalent organic frameworks (COFs) have emerged as potential catalysts due to their precise structural design, functionalizable chemical environments, and robust architectures. COF‐based materials, especially those incorporating diverse active sites like single metal sites, metal nanoparticles, and metal oxides, hold promise for CO2 conversion and energy storage. This review sheds light on CO2 photoreduction/electroreduction and storage in Li‐CO2 batteries catalyzed by COF‐based composites, focusing on recent advancements in integrating COFs with nanoparticles for CO2 reduction. It discusses design principles, synthesis methods, and catalytic mechanisms driving the enhanced performance of COF‐based nanocomposites across various applications, including electrochemical reduction, photocatalysis, and lithium CO2 batteries. The review also addresses challenges and prospects of COF‐based catalysts for efficient CO2 utilization, aiming to steer the development of innovative COF‐based nanocomposites, thus advancing sustainable energy technologies and environmental stewardship. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Metal/Covalent Organic Framework Encapsulated Lead-Free Halide Perovskite Hybrid Nanocatalysts: Multifunctional Applications, Design, Recent Trends, Challenges, and Prospects.

Perovskites are bringing revolutionization in a various fields due to their exceptional properties and crystalline structure. Most specifically, halide perovskites (HPs), lead-free halide perovskites (LFHPs), and halide perovskite quantum dots (HPs QDs) are becoming hotspots due to their unique optoelectronic properties, low cost, and simple processing. HPs QDs, in particular, have excellent photovoltaic and optoelectronic applications because of their tunable emission, high photoluminescence quantum yield (PLQY), effective charge separation, and low cost. However, practical applications of the HPs QDs family have some limitations such as degradation, instability, and deep trap states within the bandgap, structural inflexibility, scalability, inconsistent reproducibility, and environmental concerns, which can be covered by encapsulating HPs QDs into porous materials like metal-organic frameworks (MOFs) or covalent-organic frameworks (COFs) that offer protection, prevention of aggregation, tunable optical properties, flexibility in structure, enhanced biocompatibility, improved stability under harsh conditions, consistency in production quality, and efficient charge separation. These advantages of MOFs-COFs help HPs QDs harness their full potential for various applications. This review mainly consists of three parts. The first portion discusses the perovskites, halide perovskites, lead-free perovskites, and halide perovskite quantum dots. In the second portion, we explore MOFs and COFs. In the third portion, particular emphasis is given to a thorough evaluation of the development of HPs QDs@MOFs-COFs based materials for comprehensive investigations for next-generation materials intended for diverse technological applications, such as CO2 conversion, pollutant degradation, hydrogen generation, batteries, gas sensing, and solar cells. Finally, this review will open a new gateway for the synthesis of perovskite-based quantum dots.

Restrained interfacial resistance Co5.47N@C derived from metal-organic frameworks for advanced Li–CO2 batteries cathodes

Lithium–carbon dioxide (Li–CO2) batteries are novel high energy density energy storage devices that can simultaneously enrich and convert CO2, but their widespread implementation is hindered by the continuous accumulation of lithium carbonate at the cathode. Herein, we developed non-precious metal cobalt-based nitride matrix composite Co[Formula: see text]N@C based on metal-organic frameworks precursor for the catalytic cathode of advanced Li–CO2 batteries. The highly stable Co[Formula: see text]N achieves favorable adsorption and catalysis of CO2 molecules by virtue of the excellent electronic structure on the surface, while the nanoscale high dispersion also effectively promotes interfacial electron transfer. As expected, the assembled Li–CO2 battery exhibits excellent electrochemical performance in the discharge capacity of 10,000 mAh g[Formula: see text] and a cycling capability of about 400 h. Further density functional theory (DFT) calculations explored the relationship between electronic structure and electrochemical activity. This work promotes the development of catalytic materials for Li–CO2 batteries cathode.

Transforming Cu into Cu2O/RuAl intermetallic heterojunction for lowering the thermodynamic energy barrier of the CO2 reduction and evolution reactions in Li-CO2 battery

The Li–CO2 battery has been under the spotlight of future battery technologies since it can achieve CO2 utilization and energy conversion simultaneously. However, its advancement is hampered by poor energy efficiency and limited reversibility due to the sluggish kinetics of the CO2 reduction and evolution reactions. Herein, a multiscale nanoporous interpenetrating‑phase nanohybrid of RuAl intermetallic and Cu2O (MP-Cu2O/RuAl) was carved by driving synchronous phase and microstructure evolutions through dealloying of one RuCuAl master alloy. The built-in RuAl intermetallic and Cu2O closely stack to form abundant nano-interfaces with revolutionized electronic structure. The theoretical simulations reveal that the Cu2O/RuAl interface can distinctly reduce the energy barrier of the Li2CO3 decomposition reaction. The interconnected pore channels with large surface area can enhance catalytic site accessibility, mass transfer, and uniform deposition of the discharge products. In situ differential electrochemical mass spectrometry discloses that the CO2-to-electron ratio during charging coincides with the theoretical value of 3/4, demonstrating the high efficacy of MP-Cu2O/RuAl in achieving the recycling of CO2. The dealloying protocol provides an affordable platform to empower transition metal oxides into high-efficiency electrocatalysts by hybridizing with metallic nano-sponge for advancing the application of Li–CO2 batteries.

High-efficiency metal-free CO2 mineralization battery using organic redox catalysts

CO2 batteries offer a promising avenue for mitigating CO2 emissions and conversion, but encounter challenges such as high costs, dendrite, corrosion, flooding and slow kinetics stemming from the use of metal electrodes. CO2 mineralization is thermodynamically favorable (ΔGCO2), presenting an opportunity for processing solid waste and reducing CO2 emissions while potentially producing energy. However, the lack of direct electron transfer in the CO2 mineralization reaction hinders the direct generation of electrical energy. Here, we propose an organic CO2 mineralization battery (OCMB) without using metal, which efficiently harnesses CO2 to mineralize solid waste carbide slag, maximizing the recovery of mineralization reaction energy to generate electricity and produce carbonate products, without requiring renewable electricity charging. We employ a high-solubility, stable under strong alkaline conditions, and fast kinetics organic phenazine derivative—DSPZ as the electron and proton carrier, which facilitates the conversion of ΔpH between electrodes by interacting with alkaline wastes and CO2 into electricity. Simultaneously, the OCMB undergoes regeneration cycles through mineralization reactions. The theoretical model predicted the open circuit voltage (OCV) and discharge behavior of OCMB, offering insights for improved battery engineering. We demonstrate an impressive peak power density exceeding 227.5 W/m2 for the OCMB, with an estimated electricity production of ∼ 178.03 kWh per ton of CO2 mineralization. This research underscores the potential integration of OCMBs into CO2 energy systems, waste treatment processes, and chemical production, offering both economic and environmental benefits.

Impact of electrolyte solutions on carbon dioxide fixation in single chamber Al–CO2 battery

Governments and research & development (R&D) organizations are actively initiating various programs and research strategies for CO2 capture, its utilization, and integration with long duration energy storage from renewable sources worldwide. In line with the carbon capture goals, here we report a novel electrochemical Al-CO2 battery cell, that can simultaneously capture CO2 and convert it into value-added products, in addition to long-duration energy generation and storage. This innovative approach employs cost-effective Al metal as an anode and an in-house synthesized Ni–Fe based bimetallic double hydroxide catalyst as the cathode, with meticulously optimized compositions and morphologies. We explore the impact of different aqueous electrolyte solutions compositions on the cell performance, demonstrating up to 10 h of stable long duration energy storage with a stable voltage profile. The cell exhibits low polarization even at high current densities of up to 12 mA cm−2 and maintains stable cycling over 500 h. Through Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray Diffraction and X-ray photoelectron spectroscopy (XPS) analysis, we determined that the discharge product is either NaAlCO3(OH)2 or KAlCO3(OH)2, distinct from the Al2(CO3)3 typically reported in conventional Al–CO2 batteries.

Multi-scale synergistic regulation of hierarchical porous Ni@NiSe cathodes with low voltage gap, high capacity and long-term cycling stability in Li–CO2 battery

Multi-scale synergistic regulation of hierarchical porous Ni@NiSe cathodes with low voltage gap, high capacity and long-term cycling stability in Li–CO2 battery

Functional polymers-coated Cu hollow microspheres for CO2 conversion in primary Zn–CO2 batteries

Zn–CO2 batteries are attracting much attention because the CO2 reduction reaction (CO2RR) to hydrocarbon products takes place during the discharge process. However, the CO2RR products in Zn–CO2 batteries are almost exclusively C1 products (CO and HCOOH) without exploring high energy density products. Therefore, in this work, the functional polymers-coated Cu hollow microspheres are prepared as the cathodic catalysts in the primary Zn–CO2 batteries with the aim of obtaining the high energy density product of CH4. Functional polymers composed of polyethyleneimine (PEI) and perfluorinated sulfonic acid (PFSA) are orderly coated on the Cu hollow microspheres prepared by using the colloidal self-assembly technique to form a Cu/PEI/PFSA cathodic catalyst. According to the results of the finite element analysis, PFSA enables CO2 diffusion length to reach more than 200 nm, while the PEI gives rise to a high steady-state CO2 concentration of 0.726 mol m−3 on the Cu surface. Hence, as compared to the Cu nanoparticles and bare Cu hollow microspheres catalysts, the Cu/PEI/PFSA-based primary Zn–CO2 battery exhibits a maximum power density of 1.36 mW cm−2 and a high Faraday efficiency of 42.78 % towards CH4 at 5 sccm of CO2 flow rate and 1.25 mA cm−2 of current density. In addition, a homemade in-situ Raman device displays the evolution of the CO2RR intermediates during the operation of the primary Zn–CO2 batteries, revealing the direction of CO2 conversion to hydrocarbon products.

Origin of deactivation of aqueous Na–CO2 battery and mitigation for long-duration energy storage

The development of long-duration energy storage technology is crucial to facilitate the efficient utilization of renewable energy sources while mitigating carbon dioxide production. In this study, we investigate the deactivation and reactivation mechanisms of the aqueous Na–CO2 battery during extended cycling. We have designed the cathode to include non-precious intermetallic catalysts. As the cell undergoes repeated cycles, the voltage polarization during discharge progressively rises, eventually leading to the cell's deactivation and formation of decomposition products clogging the electrode surface. Results obtained from comprehensive characterization techniques, including conductive atomic force microscopy (cAFM), Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and inductively coupled plasma-mass spectrometry provide insight into the decomposition products. We also showcase an electrochemical approach for regeneration of these aqueous cells. Our findings, along with the insights we have gained, provide a path toward creating long-duration systems with self-healing properties.

N, S Co-doped carbon anchored Co9S8 cathode: Advancing sustainable energy through efficient Li–CO2 Mars batteries

Owing to their higher capacity and ability to address global warming, Li–CO2 batteries have potential for next-generation energy storage systems on Earth and for space applications. However, the key drawbacks of high overpotential and low cyclability of Li–CO2 batteries substantially hinder their practicality. In this study, we develop uniquely designed cobalt sulfide (Co9S8) nanoparticles anchored onto the N, S dual-doped hetero atoms graphitized mesoporous carbon (NSC) as a low-cost but highly effective cathodic catalyst for Li–CO2 batteries with a large number of active sites with enhanced conductivity. The as-developed Li–CO2 batteries under simulated Martian gas atmosphere conditions (Li–CO2 Mars) display a high discharge capacity and exceptional rate performance. The Li–CO2 Mars battery offers a high discharge capacity of 15147 mAh g−1 at 500 mA g−1 current density and maintains a stable performance over 120 cycles for a limited capacity of 500 mAh g−1. Further, the first-principle calculations provide a deeper understanding of the reaction pathways during discharging and charging. These results create new avenues for designing novel catalysts for high-performance Li–CO2 Mars batteries for their use in interplanetary missions.

Ultrafine Ru nanoparticles anchored on N-doped mesoporous hollow carbon spheres as a highly efficient bifunctional catalyst for Li–CO2 batteries

Rechargeable Li–CO2 battery is a facilitative and promising device for the conversion of CO2 to electrochemical energy. However, it remains a challenge to enhance the sluggish decomposition kinetics of lithium carbonate as the discharge product. Herein, the Ru nanoparticles anchored on N-doped mesoporous hollow carbon nanospheres (Ru-AHCNs) are designed as cathode to enhance the electrochemical performance of Li–CO2 battery. The Ru-AHCNs cathode displays a high discharge specific capacity of 11194.4 mA h g−1 at the current density of 100 mA g−1. In addition, the Ru-AHCNs cathode can stably run over 50 cycles and maintain a small overpotential (<1.38 V) with a limited capacity of 1000 mA h g−1 at 100 mA g−1. The excellent stability and catalytic activity of the cathode are ascribed to the following factors: (i) Uniform deposition of Ru nanoparticles in hollow carbon nanospheres can enhance the decomposition of Li2CO3 and provide considerable exposure to active sites. (ii) N-doped mesoporous hollow carbon nanospheres can provide abundant electron transport channels and promote the nucleation of discharge products. These results evidently prove the reversible formation and decomposition of the discharge products, indicating that Ru-AHCNs cathode possesses excellent bifunctional catalytic activity.

Synergy of Ni Nanoclusters and Single Atom Site: Size Effect on the Performance of Electrochemical CO2 Reduction Reaction and Rechargeable Zn−CO2 Batteries

AbstractThe design of bifunctional electrocatalysts toward reduction reaction of carbon dioxide (ECO2RR) and oxygen evolution reaction (OER) in aqueous rechargeable Zn─CO2 batteries (ZABs) still poses a significant challenge. Herein, Ni clusters (Nix) of 0.5 and 0.8 nm in diameter coupled with single Ni site (Ni−N4−C), denoted as Ni−N4/Ni5 and Ni−N4/Ni8, respectively, are synthesized and the size effect of Ni nanoclusters are studied. Ni−N4/Ni5 exhibits an ≈100% Faradaic efficiency (FECO) toward ECO2RR for CO from −0.4 to −0.8 V versus the reversible hydrogen electrode, superior to that of Ni−N4−C (FECO = 55.0%) and Ni−N4/Ni8 (FECO = 80.0%). The OER performance of Ni−N4/Ni5 and Ni−N4/Ni8 are superior or comparable to that of commercial RuO2 but outperform that of Ni−N4−C. Theoretical calculation indicates that *COOH of ECO2RR intermediates bond synergistically with Nix clusters and Ni−N4−C single atom site, promoting the activation of CO2 and reducing the energy barrier of the potential determining step of ECO2RR. Such effect is strongly size‐dependent and larger Nix nanoclusters result in too strong binding of *COOH intermediates, impede the formation of *CO. As a bifunctional cathode electrocatalyst of rechargeable alkaline aqueous ZABs, Ni−N4/Ni5 exhibits a peak power density of 11.7 mW cm−2 and cycling durability over 1200 cycles and 420 h.