CO2 Batteries Research Articles

Metal–CO2 Electrochemistry: From CO2 Recycling to Energy Storage

AbstractMetal–CO2 batteries are among the most intriguing techniques for addressing the severe climate crisis and have matured significantly to simultaneously realize adequate fixation of CO2, energy storage, and conversion. Although significant efforts have been made, the practical application of metal–CO2 battery techniques is still restricted by various tremendous challenges, namely high charge potential, poor rate capability, and reversibility. This review seeks to present a realistic assessment of the most advanced metal–CO2 systems to identify problems, and opportunities to conquer these challenges. The recent progress on understanding the reaction mechanism of CO2 reduction/evolution, cathode materials, electrocatalysts design strategies, interface construction of metal anode/electrolyte, and the role of electrolytes are systematically reviewed and discussed. Meanwhile, high‐performance electrode design principles and interface construction methods are also proposed. The effect of electrolyte and the difference between the nonaqueous and aqueous electrolyte systems in the context of the reaction mechanism, catalyst selection, metal anode protection, and corresponding enhancement strategies are also presented and evaluated. Finally, several perspectives on the opportunities and crucial challenges in the future development of metal–CO2 electrochemical systems for practical applications are proposed.

Rechargeable LiCO2 Batteries with Graphdiyne as Efficient Metal‐Free Cathode Catalysts

AbstractA rechargeable LiCO2 battery is one of the promising power sources for utilizing the greenhouse gas CO2 in a sustainable approach. However, highly efficient catalysts for reversible formation/decomposition of insulating discharge product, Li2CO3, are the main challenge, which can boost the cycle stability. Herein, 2D single‐atom‐thick graphdiyne (GDY) with abundant acetylenic bond sites is prepared by a bottom‐up cross‐coupling reaction strategy and used as metal‐free catalysts for reversible LiCO2 batteries. The prepared GDY has a rich diacetylenic unit and atomic‐level in‐plane pores in the network, which can chemically adsorb the CO2 molecules and easily promote the Li+ diffusion and thereby resulting in uniform nucleation and reversible formation/decomposition of the discharge product. The GDY hybrid cathodes show a small overpotential gap of 1.4 V at a current density of 50 mA · g−1, a high full discharge capacity of 18 416 mAh · g−1 at 100 mA · g−1, and outstanding long‐term stability of 158 cycles at 400 mA · g−1 with a curtailing capacity of 1000 mAh · g−1. Furthermore, a flexible belt‐shaped LiCO2 battery is fabricated as a proof of concept with a high gravimetric energy density of 165.5 Wh · kg−1 (based on the mass of the whole device) as well as excellent mechanical flexibility.

Promoting the Performance of Li-CO2 Batteries via Constructing Three-Dimensional Interconnected K+ Doped MnO2 Nanowires Networks.

Nowadays, Li–CO2 batteries have attracted enormous interests due to their high energy density for integrated energy storage and conversion devices, superiorities of capturing and converting CO2. Nevertheless, the actual application of Li–CO2 batteries is hindered attributed to excessive overpotential and poor lifespan. In the past decades, catalysts have been employed in the Li–CO2 batteries and been demonstrated to reduce the decomposition potential of the as-formed Li2CO3 during charge process with high efficiency. However, as a representative of promising catalysts, the high costs of noble metals limit the further development, which gives rise to the exploration of catalysts with high efficiency and low cost. In this work, we prepared a K+ doped MnO2 nanowires networks with three-dimensional interconnections (3D KMO NWs) catalyst through a simple hydrothermal method. The interconnected 3D nanowires network catalysts could accelerate the Li ions diffusion, CO2 transfer and the decomposition of discharge products Li2CO3. It is found that high content of K+ doping can promote the diffusion of ions, electrons and CO2 in the MnO2 air cathode, and promote the octahedral effect of MnO6, stabilize the structure of MnO2 hosts, and improve the catalytic activity of CO2. Therefore, it shows a high total discharge capacity of 9,043 mAh g−1, a low overpotential of 1.25 V, and a longer cycle performance.

Electrocatalysts by Electrodeposition: Recent Advances, Synthesis Methods, and Applications in Energy Conversion

AbstractThe conventional environment polluting energy sources and the continuous growing energy demand compelled researchers to find alternative energy sources. Therefore, in recent years, extensive research has been carried out in synthesizing catalysts for energy conversion applications. This review focuses on the application of various electrodeposition methods in the synthesis of energy‐related electrocatalyst and briefly discusses different electrocatalyst characterization techniques. Further, the influence of various parameters on the electrocatalyst activity and stability is highlighted. Electrocatalyst application in clean energy conversion reactions, such as the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, nitrogen reduction reaction along with the metal‐air/CO2 battery, are reviewed. Finally, the comparative experimental data are provided as a reference to synthesize the next‐generation electrodeposited electrocatalyst in clean energy conversions and beyond.

Na–CO2 battery with NASICON-structured solid-state electrolyte

Abstract Utilizing CO2 as cathode gas, Na–CO2 battery has been intensively studied due to its potential application in the exploration of Mars, where CO2 takes up 96% of the atmosphere. However, evaporation of the flammable liquid electrolyte restricts the practical application of the Na–CO2 battery. Herein, a solid-state Na–CO2 battery has been fabricated with the help of a plastic crystal electrolyte and kinetically stable interphase. The succinonitrile-based plastic crystal electrolyte interphase makes an intimate contact between Na3Zr2Si2PO12(NZSP) and cathode, thereby promotes the interfacial charge transfer. Simultaneously, the kinetically stable interphase on the anode side is revealed by the cooperation of theoretical calculation and experiments. The kinetically stable interphase protects the NZSP from the continuous interfacial parasitic reaction. The as-proposed solid-state Na–CO2 battery delivers a life span of 50 cycles at 100 mA g−1 with a potential gap of 1.4 V. This study makes solid-state electrolyte Na–CO2 battery an attractive prospect in future applications.

Rechargeable K‐CO2 Batteries with a KSn Anode and a Carboxyl‐Containing Carbon Nanotube Cathode Catalyst

AbstractMetal K‐CO2 batteries suffer from large polarization and safety hazards, which mainly result from the difficult decomposition of K2CO3 and dendrite growth. Moreover, the battery redox mechanism remains not fully understood. Here we report K‐CO2 batteries with KSn alloy as the anode and carboxyl‐containing multi‐walled carbon nanotubes (MWCNTs‐COOH) as the cathode catalyst, proving the redox mechanism to be 4 KSn + 3 CO2 ⇄ 2 K2CO3 + C + 4 Sn. Compared with K metal, the less active and dendrite‐free KSn anode effectively enhances the safety and stability of CO2 batteries. More importantly, the strong electrostatic interaction between MWCNTs‐COOH and K2CO3 weakens the C=O bond in K2CO3 and thus facilitates K2CO3 decomposition. As a result, the K‐CO2 batteries show excellent cycling stability (an overpotential increase of 0.89 V after 400 cycles) and good rate performance (up to 2000 mA g−1). This work paves a way to develop highly stable and safe CO2‐based batteries.

Rechargeable K-CO2 Batteries with a KSn Anode and a Carboxyl-Containing Carbon Nanotube Cathode Catalyst.

Metal K-CO2 batteries suffer from large polarization and safety hazards, which mainly result from the difficult decomposition of K2 CO3 and dendrite growth. Moreover, the battery redox mechanism remains not fully understood. Here we report K-CO2 batteries with KSn alloy as the anode and carboxyl-containing multi-walled carbon nanotubes (MWCNTs-COOH) as the cathode catalyst, proving the redox mechanism to be 4 KSn + 3 CO2 ⇄ 2 K2 CO3 + C + 4 Sn. Compared with K metal, the less active and dendrite-free KSn anode effectively enhances the safety and stability of CO2 batteries. More importantly, the strong electrostatic interaction between MWCNTs-COOH and K2 CO3 weakens the C=O bond in K2 CO3 and thus facilitates K2 CO3 decomposition. As a result, the K-CO2 batteries show excellent cycling stability (an overpotential increase of 0.89 V after 400 cycles) and good rate performance (up to 2000 mA g-1 ). This work paves a way to develop highly stable and safe CO2 -based batteries.

Cycling mechanism of Li2MnO3: Li–CO2 batteries and commonality on oxygen redox in cathode materials

Summary Li2MnO3 has been considered to be a representative Li-rich compound with active debates on oxygen activities. Here, by evaluating the Mn and O states in the bulk and on the surface of Li2MnO3, we clarify that Mn(III/IV) redox dominates the reversible bulk redox in Li2MnO3, while the initial charge plateau is from surface reactions with oxygen release and carbonate decomposition. No lattice oxygen redox is involved at any electrochemical stage. The carbonate formation and decomposition indicate the catalytic property of the Li2MnO3 surface, which inspires Li-CO2/air batteries with Li2MnO3 acting as a superior electrocatalyst. The absence of lattice oxygen redox in Li2MnO3 questions the origin of the oxygen redox in Li-rich compounds, which is found to be of the same nature as that in conventional materials based on spectroscopic comparisons. These findings provide guidelines on understanding and controlling oxygen activities toward high-energy cathodes and suggest opportunities on using alkali-rich materials for catalytic reactions.

Rational Fabrication of Low-Coordinate Single-Atom Ni Electrocatalysts by MOFs for Highly Selective CO2 Reduction.

Single-atom catalysts (SACs) have attracted tremendous interests due to their ultrahigh activity and selectivity. However, the rational control over coordination microenvironment of SACs remains a grand challenge. Herein, a post-synthetic metal substitution (PSMS) strategy has been developed to fabricate single-atom Ni catalysts with different N coordination numbers (denoted Ni-Nx -C) on pre-designed N-doped carbon derived from metal-organic frameworks. When served for CO2 electroreduction, the obtained Ni-N3 -C catalyst achieves CO Faradaic efficiency (FE) up to 95.6 %, much superior to that of Ni-N4 -C. Theoretical calculations reveal that the lower Ni coordination number in Ni-N3 -C can significantly enhance COOH* formation, thereby accelerating CO2 reduction. In addition, Ni-N3 -C shows excellent performance in Zn-CO2 battery with ultrahigh CO FE and excellent stability. This work opens up a new and general avenue to coordination microenvironment modulation (MEM) of SACs for CO2 utilization.

Rational Fabrication of Low‐Coordinate Single‐Atom Ni Electrocatalysts by MOFs for Highly Selective CO2 Reduction

AbstractSingle‐atom catalysts (SACs) have attracted tremendous interests due to their ultrahigh activity and selectivity. However, the rational control over coordination microenvironment of SACs remains a grand challenge. Herein, a post‐synthetic metal substitution (PSMS) strategy has been developed to fabricate single‐atom Ni catalysts with different N coordination numbers (denoted Ni‐Nx‐C) on pre‐designed N‐doped carbon derived from metal‐organic frameworks. When served for CO2 electroreduction, the obtained Ni‐N3‐C catalyst achieves CO Faradaic efficiency (FE) up to 95.6 %, much superior to that of Ni‐N4‐C. Theoretical calculations reveal that the lower Ni coordination number in Ni‐N3‐C can significantly enhance COOH* formation, thereby accelerating CO2 reduction. In addition, Ni‐N3‐C shows excellent performance in Zn–CO2 battery with ultrahigh CO FE and excellent stability. This work opens up a new and general avenue to coordination microenvironment modulation (MEM) of SACs for CO2 utilization.

“Water-in-salt” and NASICON Electrolyte-Based Na–CO2 Battery

Super concentrated electrolytes, referred to as “water-in-salt (WiS) electrolytes”, are being increasingly employed because of their wide electrochemical stability window, cost-effectiveness, and non-flammability. However, the free water molecules present in WiS electrolytes prevent the use of highly abundant, low-cost Na metal as the anode for various Na–gas batteries. In this study, we develop a WiS-based hybrid Na–CO2 battery that utilizes CO2 and serves as an energy storage cell, where a Na super-ionic conductor enables us to directly use Na metal as the anode component and a WiS electrolyte for the cathode electrolyte. In particular, linear sweep voltammetry with corresponding differential electrochemical mass spectrometry ensures an expanded electrochemical stability window, which guarantees Na–CO2 operation without electrolyte degradation during the charge process. Furthermore, we introduce a nano-sized Ru catalyst to the current collector using the Joule-heating method for lowering the discharge–charge gap. Consequently, the Na–CO2 batteries with these Ru@carbon current collectors reduce the overpotential gap and exhibit a cycling endurance of over 75 cycles (50 days) without significant alteration. These promising results demonstrate the potential of cost-effective, WiS-based Na–CO2 batteries that utilize CO2 and can be employed as energy storage cells.

Highly Boosted Reaction Kinetics in Carbon Dioxide Electroreduction by Surface‐Introduced Electronegative Dopants

AbstractEffectively improving the selectivity while reducing the overpotential over the electroreduction of CO2 (CO2ER) has been challenging. Herein, electronegative N atoms and coordinatively unsaturated NiN3 moieties co‐anchored carbon nanofiber (NiN3NCNFs) catalyst via an integrated electrospinning and carbonization strategy are reported. The catalyst exhibits a maximum CO Faradaic efficiency (F.E.) of 96.6%, an onset potential of −0.3 V, and a low Tafel slope of 71 mV dec−1 along with high stability over 100 h. Aberration corrected scanning transmission electron microscopy, X‐ray absorption spectroscopy, and X‐ray photoelectron spectroscopy identify the atomically dispersed NiN3 sites with Ni atom bonded by three pyridinic N atoms. The existence of abundant electronegative N dopants adjoin the NiN3 centers in NiN3NCNFs. Theoretical calculations reveal that both, the undercoordinated NiN3 centers and their first neighboring C atoms modified by extra N dopants, display the positive effect on boosting CO2 adsorption and water dissociation processes, thus accelerating the CO2ER kinetics process. Furthermore, a designed ZnCO2 battery with the cathode of NiN3NCNFs delivers a maximum power density of 1.05 mW cm−2 and CO F.E. of 96% during the discharge process, thus providing a promising approach to electric energy output and chemical conversion.

Nano‐Sized Au Particle‐Modified Carbon Nanotubes as an Effective and Stable Cathode for Li−CO2 Batteries

AbstractLithium‐carbon dioxide (Li−CO2) batteries show a great potential in the fields of CO2 fixation and energy storage, and moreover the research of Li−CO2 batteries is of great significance to the practical application of Lithium‐air (Li‐air) batteries. However, the sluggish kinetics and high charging potential causing by the wide band gap insulator Li2CO3 make it extremely important to research cathode catalysts that can promote the decomposition of Li2CO3 and reduce the charge potential. Here, we prepared a composite of Au nanoparticles uniformly distribute on carbon nanotubes (CNTs) network (AuNPs/CNTs) as an efficient cathode catalyst. Benefitted by the small sized Li2CO3 which is easier to decompose during charge process, the AuNPs/CNTs‐based batteries exhibit a high specific capacity of 6399 mAh g−1, a low overpotential of 1.53 V and a stable cycling performance of 46 cycles, demonstrating the conspicuous catalytic performance of AuNPs/CNTs.

A Modeling Study of the Cycling Behavior of Non-Aqueous Li-O2/CO2 Batteries

A non-aqueous lithium-oxygen/carbon dioxide (Li-O2/CO2) battery model is developed with the consideration of lithium peroxide (Li2O2) and lithium carbonated (Li2CO3) depositions during the discharge-charge cycles. By comparing with Li-O2 batteries, the presence of CO2 increases the discharge voltage and capacity at a not very high current density. The effects of transport properties of O2 and CO2 in the electrolyte on the battery cycling performance are explored. The increases of diffusivity and solubility of O2 are beneficial to increase the battery capacity but worsen the cycling capacity decay. Conversely, the increase of CO2 diffusivity promotes the battery capacity and weakens the capacity loss with cycling. The solubility of CO2 plays a more complicated role than CO2 diffusivity on the cycling performance of Li-O2/CO2 batteries. A moderate CO2 solubility leads to the most severe decay of the capacity with cycles, but an enough higher CO2 solubility qualifies the battery a much better reversible capacity. These results present that the capacity decay of Li-O2/CO2 batteries with cycles is primarily determined by the accumulation of undecomposed Li2CO3 near the cathode outer boundary. Therefore, the promotion of Li2CO3 decomposition near the cathode outer boundary is critical to improving the Li-O2/CO2 battery’s cycling performance.

Electrochemical reduction of CO2 in ionic liquid: Mechanistic study of Li–CO2 batteries via in situ ambient pressure X-ray photoelectron spectroscopy

In-depth mechanistic understanding of CO 2 reduction reaction (CRR) and CO 2 evolution reaction (CER) is the prerequisite to develop stable and efficient Li–CO 2 batteries. In this study, we investigate the redox reaction of CO 2 on the porous carbon surface in ionic liquid electrolyte via synchrotron-based in situ ambient pressure X-ray photoelectron spectroscopy (APXPS) technique. We used ionic liquid to facilitate CO 2 capture and stabilize CRR intermediate anions owing to its strong solvation for Li + . We demonstrate that pure CO 2 reduction is not electrochemically active at room temperature on porous carbon electrode and its kinetics can be remarkably improved by H 2 O, which could be responsible for the discrepancy on CRR kinetics in the literature. However, in the presence of H 2 O, the formed LiOH gradually converted to Li 2 CO 3 leading to severe electrolyte degradation in charging reaction. With the assistance of O 2 in the ionic liquid -based electrolyte, we show, for the first time, CRR yields a low-valence amorphous carbon and Li 2 O 2 /Li 2 O in the Li–CO 2 batteries. The formed amorphous carbon, Li 2 O 2 and Li 2 O exhibit higher rechargeability and faster kinetics compared with Li 2 CO 3 -oxidation. These new findings provide direct evidence of CRR mechanism and insights in resolving the discrepancy on CRR kinetics in Li–CO 2 batteries. • Synchrotron-based in-situ APXPS is developed to probe the Li–CO 2 reaction chemistry in ionic liquid electrolyte. • Pure CO 2 reduction is not electrochemically active at room temperature and its kinetics can be significantly improved by H 2 O. • CO 2 reduction in ionic liquid yields amorphous carbon and Li 2 O 2 /Li 2 O which are more reversible than Li 2 CO 3 .

A rechargeable all-solid-state Li–CO2 battery using a Li1.5Al0.5Ge1.5(PO4)3 ceramic electrolyte and nanoscale RuO2 catalyst

A rechargeable all-solid-state Li–CO2 battery using a RuO2 catalyst and LAGP solid-state electrolyte was demonstrated.

Kinetics of the CO2 reduction reaction in aprotic Li–CO2 batteries: a model study

In this study, we propose a critical kinetics descriptor, i.e., the adsorption energy of the LiCO2 intermediate on the cathode surface, to reveal the interplay and competition between the solution- and the surface-mediated pathways toward better Li–CO2 batteries.

Ultrathin p–n type Cu2O/CuCoCr-layered double hydroxide heterojunction nanosheets for photo-assisted aqueous Zn–CO2 batteries

Photo-assisted Zn–CO2 batteries over a Cu2O/CuCoCr-LDH photocathode were fabricated successfully, which allowed the achievement of the outstanding photoelectric catalytic conversion of CO2 to CO and remarkable round trip efficiency.

Coralloid Au enables high-performance Zn–CO2 battery and self-driven CO production

Coralloid Au is reported as an efficient and stable electrocatalyst for catalyzing membrane electrode assembly with 94.2% FECO, Zn–CO2 battery with 0.7 mW cm−2 power density and self-driven CO2 electrolysis with 0.44 ml h−1 CO productivity.

In/ZnO@C hollow nanocubes for efficient electrochemical reduction of CO2 to formate and rechargeable Zn–CO2 batteries

In/ZnO@C hollow nanocubes derived from In(OH)3-doped Zn-MOFs were developed for the electrochemical reduction of CO2 to formate and rechargeable aqueous Zn–CO2 batteries.