Enhancing Catalyzed Decomposition of Na2CO3 with Co2MnO x Nanowire-Decorated Carbon Fibers for Advanced Na-CO2 Batteries

Multiscale Defective Interfaces for Realizing Na-CO2 Batteries With Ultralong Lifespan

Despite their favorable high energy density and potential for CO2 recycling, Na-CO2 batteries have been held back by limitations in cycling capability, stemming from the sluggish CO2 reduction/evolution reaction (CO2RR/CO2ER) kinetics at CO2 cathode and unmanageable deposition/stripping of metallic Na at the anode upon cycling. Herein, a "two-in-one" electrode with multiscale defective FeCu interfaces (CP@FeCu) is presented, which is capable of improving the CO2RR/CO2ER kinetics of CO2-breathing cathode, while modulating sodium deposition behavior. Experimental and theoretical investigations reveal multiscale defective FeCu interfaces are responsible for the enhancement of sodiophilicity and catalytic properties. The defect and valence oscillation effects originate in multiscale defective FeCu interfaces, effectively facilitating the adsorption of reactants and decomposition of Na2CO3 during CO2RR/CO2ER processes, along with exceptional cycling stability of 2400 cycles (4800 h) at 5 µA cm-2. Meanwhile, the CP@FeCu with sodium affinity creates a uniform electric field and robust adsorption for Na, making initial nucleation sites more conducive to Na deposition and achieving dendrite-resistant and durable anodes. This work offers a scientific insight into the functionalization design of "two-in-one" electrodes, which is essential for a unified solution to the challenges in sodium anodes and CO2 cathodes.

A Long-Cycle-Life Reversible Li-CO2 Battery Enabled by Engineering the Active Sites of Graphene with Pd Nanoparticles

Li-CO2 batteries have been recognized as an emerging technology for energy storage systems owing to their high theoretical specific energy and environmentally friendly CO2 fixation ability. However, their development for applications requires a high energy efficiency and long cycle-life, this is currently limited to the formation of wide-bandgap insulator Li2CO3 during discharge. Here, nanoparticle Pd supported on reduced graphene oxide (rGO) is utilized as cathodes for Li-CO2 batteries, Pd nanoparticles as active centers significantly enhance CO2RR/CO2ER reaction activity, which can support the fast formation and decomposition of Li2CO3 in organic electrolytes and achieve a high discharge capacity of 7500 mAh g-1. It also performs remarkably high cycling stability of over 500 cycles with a long cycle-life of 5000 hours. The observed super electrochemical performance is attributable to the thick electrode design and uniform distribution of ultrafine catalyst nanoparticle Pd. When Li2CO3 is adsorbed on Pd particle, the Li-O bond in Li2CO3 will be elongated due to the interactions of two nucleophilic O atoms with Pd, resulting in a weakening of the Li-O bond and activation of Li2CO3. Our work suggests a way to design catalysts with high activity that can be used to activate the performance of Li-CO2 batteries.

Low-Overpotential Rechargeable Na-CO2 Batteries Enabled by an Oxygen-Vacancy-Rich Cobalt Oxide Catalyst

Rechargeable sodium-carbon dioxide (Na-CO2) batteries have been proposed as a promising CO2 utilization technique, which could realize CO2 reduction and generate electricity at the same time. They suffer, however, from several daunting problems, including sluggish CO2 reduction and evolution kinetics, large polarization, and poor cycling stability. In this study, a rambutan-like Co3O4 hollow sphere catalyst with abundant oxygen vacancies was synthesized and employed as an air cathode for Na-CO2 batteries. Density functional theory calculations reveal that the abundant oxygen vacancies on Co3O4 possess superior CO2 binding capability, accelerating CO2 electroreduction, and thereby improving the discharge capacity. In addition, the oxygen vacancies also contribute to decrease the CO2 decomposition free energy barrier, which is beneficial for reducing the overpotential further and improving round-trip efficiency. Benefiting from the excellent catalytic ability of rambutan-like Co3O4 hollow spheres with abundant oxygen vacancies, the fabricated Na-CO2 batteries exhibit extraordinary electrochemical performance with a large discharge capacity of 8371.3 mA h g-1, a small overpotential of 1.53 V at a current density of 50 mA g-1, and good cycling stability over 85 cycles. These results provide new insights into the rational design of air cathode catalysts to accelerate practical applications of rechargeable Na-CO2 batteries and potentially Na-air batteries.

Understanding Catalytic Mechanisms and Cathode Interface Kinetics in Nonaqueous Mg-CO2 Batteries

We leverage first-principles density functional theory (DFT) calculations to understand the electrocatalytic processes in Mg-CO2 batteries, considering ruthenium oxide (RuO2) as an archetypical cathode catalyst. Our goal is to establish a mechanistic framework for understanding the charging and discharging reaction pathways and their influence on overpotentials. On the RuO2 (211) surface, we found reaction initiation through thermodynamically favorable adsorption of Mg followed by interactions with CO2. However, we found that the formation of carbonate (CO32-) and oxalate (C2O42-) intermediates via the activation of CO2 at the catalytic site is thermodynamically unfavorable. We predict that MgC2O4 will form as the discharge product due to its lower overpotential compared to MgCO3. However, MgC2O4 is thermodynamically unstable and is expected to decompose into MgCO3, MgO, and C as final discharge products. Through Bader charge analysis, we investigate the covalent interactions between intermediates and catalyst sites. Moreover, we study the electrochemical free energy profiles of the most favorable reaction pathways and determine discharge and charge overpotentials of 1.30 and 1.35 V, respectively. Our results underscore the importance of catalyst design for the cathode material to overcome performance limitations in nonaqueous Mg-CO2 batteries.

Recent Advances in Rechargeable Metal-CO2 Batteries with Nonaqueous Electrolytes

This review article discusses the recent advances in rechargeable metal-CO2 batteries (MCBs), which include the Li, Na, K, Mg, and Al-based rechargeable CO2 batteries, mainly with nonaqueous electrolytes. MCBs capture CO2 during discharge by the CO2 reduction reaction and release it during charging by the CO2 evolution reaction. MCBs are recognized as one of the most sophisticated artificial modes for CO2 fixation by electrical energy generation. However, extensive research and substantial developments are required before MCBs appear as reliable, sustainable, and safe energy storage systems. The rechargeable MCBs suffer from the hindrances like huge charging-discharging overpotential and poor cyclability due to the incomplete decomposition and piling of the insulating and chemically stable compounds, mainly carbonates. Efficient cathode catalysts and a suitable architectural design of the cathode catalysts are essential to address this issue. Besides, electrolytes also play a vital role in safety, ionic transportation, stable solid-electrolyte interphase formation, gas dissolution, leakage, corrosion, operational voltage window, etc. The highly electrochemically active metals like Li, Na, and K anodes severely suffer from parasitic reactions and dendrite formation. Recent research works on the aforementioned secondary MCBs have been categorically reviewed here, portraying the latest findings on the key aspects governing secondary MCB performances.

Fundamental Understanding of Nonaqueous and Hybrid Na-CO2 Batteries: Challenges and Perspectives

Alkali metal-CO₂ batteries, which combine CO₂ recycling with energy conversion and storage, are a promising way to address the energy crisis and global warming. Unfortunately, the limited cycle life, poor reversibility, and low energy efficiency of these batteries have hindered their commercialization. Li-CO₂ battery systems have been intensively researched in these aspects over the past few years, however, the exploration of Na-CO₂ batteries is still in its infancy. To improve the development of Na-CO₂ batteries, one must have a full picture of the chemistry and electrochemistry controlling the operation of Na-CO₂ batteries and a full understanding of the correlation between cell configurations and functionality therein. Here, recent advances in CO₂ chemical and electrochemical mechanisms on nonaqueous Na-CO₂ batteries and hybrid Na-CO₂ batteries (including O₂ -involved Na-O₂ /CO₂ batteries) are reviewed in-depth and comprehensively. Following this, the primary issues and challenges in various battery components are identified, and the design strategies for the interfacial structure of Na anodes, electrolyte properties, and cathode materials are explored, along with the correlations between cell configurations, functional materials, and comprehensive performances are established. Finally, the prospects and directions for rationally constructing Na-CO₂ battery materials are foreseen.

Nitrogen-Doped Carbon Polyhedrons Confined Fe-P Nanocrystals as High-Efficiency Bifunctional Catalysts for Aqueous Zn-CO2 Batteries

Emerging Fe bonded with heteroatom P in carbon matrix (FePC) holds great promise for electrochemical catalysis, but the design of highly active and cost-efficient FePC structure for the electrocatalytic CO₂ reduction reaction (CO₂ RR) and aqueous ZnCO₂ batteries (ZCBs) is still challenging. Herein, polyhedron-shaped bifunctional electrocatalysts, FeP nanocrystals anchored in N-doped carbon polyhedrons (Fe-P@NCPs), toward a reversible aqueous ZnCO₂ battery, are reported. The Fe-P@NCPs are synthesized through a facile strategy by using self-templated zeolitic imidazolate frameworks (ZIFs), followed by an in situ high-temperature calcination. The resultant catalysts exhibit aqueous CO₂ RR activity with a CO Faradaic efficiency up to 95% at -0.55 V versus reversible hydrogen electrode (RHE), comparable to the previously best-reported values of FeNC structure. The as-constructed ZCBs with designed Fe-P@NCPs cathode, show the peak power density of 0.85 mW cm^-2 and energy density of 231.8 Wh kg^-1 with a cycling durability over 500 cycles, and outstanding stability in terms of discharge voltage for 7 days. The high selectivity and efficiency of the battery are attributed to the presence of highly catalytic FeP nanocrystals in N-doped carbon matrix, which can effectively increase the number of catalytically active sites and interfacial charge-transfer conductivity, thereby improving the CO₂ RR activity.

Recent Advances in Metal-Gas Batteries with Carbon-Based Nonprecious Metal Catalysts

Metal-gas batteries draw a lot of attention due to their superiorities in high energy density and stable performance. However, the sluggish electrochemical reactions and associated side reactions in metal-gas batteries require suitable catalysts, which possess high catalytic activity and selectivity. Although precious metal catalysts show a higher catalytic activity, high cost of the precious metal catalysts hinders their commercial applications. In contrast, nonprecious metal catalysts complement the weakness of cost, and the gap in activity can be made up by increasing the amount of the nonprecious metal active centers. Herein, recent work on carbon-based nonprecious metal catalysts for metal-gas batteries is summarized. This review starts with introducing the advantages of carbon-based nonprecious metal catalysts, followed by a discussion of the synthetic strategy of carbon-based nonprecious metal catalysts and classification of active sites, and finally a summary of present metal-gas batteries with the carbon-based nonprecious metal catalysts is presented. The challenges and opportunities for carbon-based nonprecious metal catalysts in metal-gas batteries are also explored.

Molybdenum Disulfide/Tin Disulfide Ultrathin Nanosheets as Cathodes for Sodium-Carbon Dioxide Batteries

Metal-CO₂ rechargeable batteries are of great importance due to their higher energy density and carbon capture capability. In particular, Na-CO₂ batteries are potential energy-storage devices that can replace Li-based batteries due to their lower cost and abundance. However, because of the slow electrochemical processes owing to the carbonated discharge products, the cell shows a high overpotential. The charge overpotential of the Na-CO₂ battery increases because of the cathode catalyst's inability to break down the insulating discharge product Na₂CO₃, thereby resulting in poor cycle performance. Herein, we develop an ultrathin nanosheet MoS₂/SnS₂ cathode composite catalyst for Na-CO₂ battery application. Insertion of SnS₂ reduces the overpotential and improves the cyclic stability compared to pristine MoS₂. As shown by a cycle test with a restricted capacity of 500 mAh/g at 50 mA/g, the battery is stable up to 100 discharge-charge cycles as the prepared catalyst successfully decomposes Na₂CO₃. Furthermore, the battery with the MoS₂/SnS₂ cathode catalyst has a discharge capacity of 35 889 mAh/g. The reasons for improvements in the cycle performance and overpotential of the MoS₂/SnS₂ composite cathode catalyst are examined by a combination of Raman, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure analysis, which reveals an underneath phase transformation and changes in the local atomic environment to be responsible. SnS₂ incorporation induces S-vacancies in the basal plane and 1T character in 2H MoS₂. This combined impact of SnS₂ incorporation results in undercoordinated Mo atoms. Such a change in the electronic structure and the phase of the MoS₂/SnS₂ composite cathode catalyst results in higher catalytic activity and reduces the cell overpotential.

Recent Development of Electrocatalytic CO2 Reduction Application to Energy Conversion

Carbon dioxide (CO₂ ) emission has caused greenhouse gas pollution worldwide. Hence, strengthening CO₂ recycling is necessary. CO₂ electroreduction reaction (CRR) is recognized as a promising approach to utilize waste CO₂ . Electrocatalysts in the CRR process play a critical role in determining the selectivity and activity of CRR. Different types of electrocatalysts are introduced in this review: noble metals and their derived compounds, transition metals and their derived compounds, organic polymer, and carbon-based materials, as well as their major products, Faradaic efficiency, current density, and onset potential. Furthermore, this paper overviews the recent progress of the following two major applications of CRR according to the different energy conversion methods: electricity generation and formation of valuable carbonaceous products. Considering electricity generation devices, the electrochemical properties of metal-CO₂ batteries, including Li-CO₂ , Na-CO₂ , Al-CO₂ , and Zn-CO₂ batteries, are mainly summarized. Finally, different pathways of CO₂ electroreduction to carbon-based fuels is presented, and their reaction mechanisms are illustrated. This review provides a clear and innovative insight into the entire reaction process of CRR, guiding the new electrocatalysts design, state-of-the-art analysis technique application, and reaction system innovation.

A Brief Review of Catalytic Cathode Materials for Na-CO2 Batteries

As an emerging energy storage technology, Na-CO2 batteries with high energy density are drawing tremendous attention because of their advantages of combining cost-effective energy conversion and storage with CO2 clean recycle and utilization. Nevertheless, their commercial applications are impeded by unsatisfactory electrochemical performance including large overpotentials, poor rate capability, fast capacity deterioration, and inferior durability, which mainly results from the inefficient electrocatalysts of cathode materials. Therefore, novel structured cathode materials with efficient catalytic activity are highly desired. In this review, the latest advances of catalytic cathode materials for Na-CO2 batteries are summarized, with a special emphasis on the electrocatalysts for CO2 reduction and evolution, the formation and decomposition of discharge product, as well as their catalytic mechanism. Finally, an outlook is also proposed for the future development of Na-CO2 batteries.

Tunable MXene-Derived 1D/2D Hybrid Nanoarchitectures as a Stable Matrix for Dendrite-Free and Ultrahigh Capacity Sodium Metal Anode

Although sodium (Na) is one of the most promising alternatives to lithium as an anode material for next-generation batteries, uncontrollable Na dendrite growth still remains the main challenge for Na metal batteries. Herein, a novel 1D/2D Na₃Ti₅O₁₂-MXene hybrid nanoarchitecture consisting of Na₃Ti₅O₁₂ nanowires grown between the MXene nanosheets is synthesized by a facile approach using cetyltrimethylammonium bromide (CTAB)-pretreated Ti₃C₂ MXene. Used as a matrix for the Na metal anode, the Na₃Ti₅O₁₂ nanowires, formed benefiting from the CTAB stabilization, have chemical interaction with Na and thus provide abundant Na nucleation sites. These 1D nanostructures, together with the unique confinement effect from the 2D nanosheets, effectively guide and control the Na deposition within the interconnected nanochannels, preventing the "hot spot" formation for dendrite growth. A stable cycling performance can be achieved at a high current density up to 10 mA cm^-2 along with an ultrahigh capacity up to 20 mAh cm^-2.

Li-CO2 and Na-CO2 Batteries: Toward Greener and Sustainable Electrical Energy Storage

Metal-CO₂ batteries, especially Li-CO₂ and Na-CO₂ batteries, offer a novel and attractive strategy for CO₂ capture as well as energy conversion and storage with high specific energy densities. However, some scientific issues and challenges existing restrict their practical applications. Here, recent progress of crucial reaction mechanisms on cathodes in Li-CO₂ and Na-CO₂ batteries are summarized. The detailed reaction pathways can be modified by operation conditions, electrolyte compositions, and catalysts. Besides, specific discussions from aspects of catalyst design, stability of electrolytes, and anode protection are presented. Perspectives of several innovative directions are also put forward. This review provides an intensive understanding of Li-CO₂ and Na-CO₂ batteries and gives a useful guideline for the practical development of metal-CO₂ batteries and even metal-air batteries.

Designing an All-Solid-State Sodium-Carbon Dioxide Battery Enabled by Nitrogen-Doped Nanocarbon

All-solid-state sodium-carbon dioxide (Na-CO₂) battery is an emerging technology that effectively utilizes the greenhouse gas, CO₂, for energy storage with the virtues of minimized electrolyte leakage and suppressed Na dendrite growth for the Na metal anode. However, the sluggish reduction/evolution reactions of CO₂ on the solid electrolyte/CO₂ cathode interface have caused premature battery failure. Herein, nitrogen (N)-doped nanocarbon derived from metal-organic frameworks is designed as a cathode catalyst to solve this challenge. The porous and highly conductive N-doped nanocarbon possesses superior uptake and binding capability with CO₂, which significantly accelerates the CO₂ electroreduction and promotes the formation of thin sheetlike discharged products (200 nm in thickness) that can be easily decomposed upon charging. Accordingly, reduced discharge/charge overpotential, high discharge capacity (>10 000 mAh g^-1), long cycle life, and high energy density (180 Wh kg^-1 in pouch cells) are achieved at 50 °C.

Governing Role of Solvent on Discharge Activity in Lithium-CO2 Batteries

Non-aqueous Li-CO₂ batteries reported in  literature have almost exclusively relied upon glyme-based electrolytes, leading to a hypothesis that they are uniquely active for CO₂ discharge. Here, we study the effect of electrolyte composition on CO₂ activity to examine whether this is the case. The results indicate that TEGDME-based electrolytes containing moderate concentrations of Li⁺ salts (roughly within the range of 0.7-2 M examined herein) are most conducive to CO₂ activation, especially compared to dimethyl sulfoxide and propylene carbonate-based electrolytes. Through electrochemical, spectroscopic, and computational methods, we determine that glymes have lower desolvation energies for Li⁺  compared to other solvent candidates, whereas high salt concentrations increase the local density of Li⁺ surrounding CO₂ and reduction intermediates. These attributes collectively increase the availability of Li⁺, crossing a threshold necessary to support CO₂  activation. Discharge voltage and reaction rates are also sensitive to the alkali cation identity, further invoking its key role in enabling or suppressing reactivity.

Highly Efficient CO2 Utilization via Aqueous Zinc- or Aluminum-CO2 Systems for Hydrogen Gas Evolution and Electricity Production

Atmospheric carbon dioxide (CO₂ ) has increased from 278 to 408 parts per million (ppm) over the industrial period and has critically impacted climate change. In response to this crisis, carbon capture, utilization, and storage/sequestration technologies have been studied. So far, however, the economic feasibility of the existing conversion technologies is still inadequate owing to sluggish CO₂ conversion. Herein, we report an aqueous zinc- and aluminum-CO₂ system that utilizes acidity from spontaneous dissolution of CO₂ in aqueous solution to generate electrical energy and hydrogen (H₂ ). The system has a positively shifted onset potential of hydrogen evolution reaction (HER) by 0.4 V compared to a typical HER under alkaline conditions and facile HER kinetics with low Tafel slope of 34 mV dec^-1 . The Al-CO₂ system has a maximum power density of 125 mW cm^-2 which is the highest value among CO₂ utilization electrochemical system.

A compatible anode/succinonitrile-based electrolyte interface in all-solid-state Na-CO2 batteries

A compatible anode/succinonitrile-based electrolyte interface is achieved owing to the in situ formed NaF-rich interphase through an extremely simple approach.

All-solid-state sodium batteries have great potential for large-scale energy storage applications. However, constructing a compatible Na anode/solid-state electrolyte (SSE) interface is still challenging because most SSEs are unstable toward Na metal. A succinonitrile (SN) SSE shows high room-temperature ionic conductivity (10^–3 S cm^–1) but easily deteriorates if in contact with Na metal, leading to continuously increased interfacial resistance. Here we present an extremely simple approach to introduce a compact NaF-rich interphase on a Na surface via chemical reactions between fluoroethylene carbonate–Na⁺ and Na metal, resulting in a compatible Na anode/SN-based electrolyte interface. The in situ formed NaF-rich interphase can not only prevent side reactions between the SN-based electrolyte and Na anode but also regulate the uniform deposition of dendrite-free Na. As a result, the symmetric cells show a low overpotential of 150 mV after cycling for 4000 h. Furthermore, all-solid-state Na–CO₂ batteries (4Na + 3CO₂ ↔ 2Na₂CO₃ + C) with the compatible interface can run for 50 cycles with a small overpotential increase of 0.33 V. This work provides a promising method to build a stable interface that enables the use of an SSE which is unstable toward Na in Na metal batteries.

Advanced rechargeable Na–CO2 batteries enabled by a ruthenium@porous carbon composite cathode with enhanced Na2CO3 reversibility

Porous ketjen black-supported ruthenium nanoparticles (Ru@KB) as a cathode for reversible Na–CO₂ batteries with excellent cycling performance.