Synergistic Heterostructure Catalyst for Enhanced CO 2 ‐to‐C2 Conversion and High‐Performance Aqueous Zn‐CO 2 Batteries

Hybrid Inorganic-Biological Systems: Faradaic and Quantum Efficiency, Necessary but Not Sufficient

The electrochemical reduction of CO₂ (CO₂RR) into valuable multi-carbon (C₂⁺) products offers a promising route for sustainable CO₂ conversion. However, many catalysts suffer from low Faradaic efficiency (FE) for C₂⁺ formation, limiting their practical application.In this study, we develop a scalable anodic oxidation method to fabricate Cu/Cu₂O heterostructured catalysts, where multifaceted Cu₂O nanoparticles form intimate interfaces with nanostructured Cu on a PTFE layer. This unique architecture significantly enhances CO₂RR selectivity, achieving a high C₂⁺ Faradaic efficiency of 58.1% and stable electrolysis for ~12 hours at 200 mA cm⁻² in a full-cell configuration with a NaOH electrolyte.Furthermore, we systematically investigate the effects of Cu film thickness and PTFE membrane pore size, along with the same key parameters for carbon paper as an alternative gas diffusion layer (GDL) in gas diffusion electrode (GDE) fabrication, to evaluate its stability and Faradaic efficiency compared to PTFE. Our findings provide valuable insights into how these factors influence product selectivity and catalyst stability. Structural and surface characterization (XRD, XPS, SEM) confirm the formation of stable Cu/Cu₂O interfaces, which enhance CO₂RR efficiency and catalyst durability.

Fast charging and discharging are keen focus areas of electric vehicles (EVs) in order to reduce vehicle down time and support the variable load requirement. In EVs, mainly lithium batteries with various chemistry such as NCA (nickel cobalt aluminum oxides), LTO (lithium titanate oxide), LFP (lithium iron phosphate), LNO (lithium nickel oxide) and NMC (nickel manganese cobalt oxides) are used as energy storage system. Performance of lithium batteries varies with the chemistry and temperature of batteries along with surrounding conditions. More heat is generated during fast charging and discharging of batteries which lead to high temperature rise and further impact the performance, life and safety of batteries. Thus, it’s essential to study the thermal behaviour for fast charging and discharging of various lithium batteries to provide desired thermal management system for safety and better performance. In this paper, the thermal characteristics of various 18650 lithium batteries including NCA, NMC and LFP are investigated experimentally and numerically from slow charging and discharging loading rate of 0.5C to fast charging and discharging loading rates of 1.5C and 2.5C at different surrounding temperature of 27°C and 45°C. In the numerical investigation, the internal resistance of the batteries is first measured experimentally at various SOCs and battery temperatures, and then the battery surface temperature is determined using an appropriate numerical method for solving the energy balance equation. From slow to fast loading rates at varying ambient temperatures, the numerical study approach presented in this work estimates the battery surface temperature with at least 90% accuracy for the whole duration of the load cycle. The thermal assessment of NCA, NMC, and LFP batteries in this work can help to determine battery management system operating strategies and, ultimately, to develop an appropriate thermal management system.

Developing sustainable and renewable energy sources along with efficient energy storage and conversion technologies is vital to address environmental and energy challenges. Electrochemical water splitting coupling with grid‐scale renewable energy harvesting technologies is becoming one of the most promising approaches. Besides, hydrogen with the highest mass‐energy density of any fuel is regarded as the ultimate clean energy carrier. The realization of practical water splitting depends heavily on the development of low‐cost, highly active, and durable catalysts for hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs). Recently, heterostructured catalysts, which are generally composed of electrochemical active materials and various functional additives, have demonstrated extraordinary electrocatalytic performance toward HER and OER, and particularly a number of precious‐metal‐free heterostructures delivered comparable activity with precious‐metal‐based catalysts. Herein, an overview is presented of recent research progress on heterostructured HER catalysts. It starts with summarizing the fundamentals of HER and approaches for evaluating HER activity. Then, the design and synthesis of heterostructures, electrochemical performance, and the related mechanisms for performance enhancement are discussed. Finally, the future opportunities and challenges are highlighted for the development of heterostructured HER catalysts from the points of view of both fundamental understandings and practical applications.

Iron phthalocyanine (FePc) with unique FeN4 site has attracted increasing interests as a promising non‐precious catalyst. However, the plane symmetric structure endows FePc with undesired catalytic performance toward the oxygen reduction reaction (ORR). Here, we report a novel one‐dimensional heterostructured ORR catalyst by coupling FePc at polyoxometalate‐encapsulated carbon nanotubes (FePc‐{PW12}@NTs) using host‐guest chemistry. The encapsulation of polyoxometalates can induce a local tensile strain of single‐walled NTs to strengthen the interactions with FePc. Both the strain and curvature effects of {PW12}@NT scaffold tune the geometric structure and electronic localization of FeN4 centers to enhance the ORR catalytic performance. As expected, such a heterostructured FePc‐{PW12}@NT electrocatalyst exhibits prominent durability, methanol tolerance, and ORR activity with a high half‐wave potential of 0.90 V and a low Tafel slope of 30.9 mV dec−1 in alkaline medium. Besides, the assembled zinc‐air battery demonstrates an ultrahigh power density of 280 mW cm−2, excellent charge/discharge ability and long‐term stability over 500 h, outperforming that of the commercial Pt/C+IrO2 cathode. This study offers a new strategy to design novel heterostructured catalysts and opens a new avenue to regulate the electrocatalytic performance of phthalocyanine molecules.

Iron phthalocyanine (FePc) with unique FeN4 site has attracted increasing interests as a promising non-precious catalyst. However, the plane symmetric structure endows FePc with undesired catalytic performance toward the oxygen reduction reaction (ORR). Here, we report a novel one-dimensional heterostructured ORR catalyst by coupling FePc at polyoxometalate-encapsulated carbon nanotubes (FePc-{PW12}@NTs) using host-guest chemistry. The encapsulation of polyoxometalates can induce a local tensile strain of single-walled NTs to strengthen the interactions with FePc. Both the strain and curvature effects of {PW12}@NT scaffold tune the geometric structure and electronic localization of FeN4 centers to enhance the ORR catalytic performance. As expected, such a heterostructured FePc-{PW12}@NT electrocatalyst exhibits prominent durability, methanol tolerance, and ORR activity with a high half-wave potential of 0.90 V and a low Tafel slope of 30.9 mV dec-1 in alkaline medium. Besides, the assembled zinc-air battery demonstrates an ultrahigh power density of 280 mW cm-2, excellent charge/discharge ability and long-term stability over 500 h, outperforming that of the commercial Pt/C+IrO2 cathode. This study offers a new strategy to design novel heterostructured catalysts and opens a new avenue to regulate the electrocatalytic performance of phthalocyanine molecules.

Energy storage systems (ESSs) are required for stable electricity supply from power plants and efficient usage of generated electricity. ESSs are also needed to accommodate fluctuations in renewable energy generation. Redox flow batteries (RFBs) are considered as one of the reliable choices for ESSs. Since 1970s, RFB technologies have been developed mainly on the basis of aqueous electroytes, which show a critical drawback; limited working voltage (< 1.23 V) due to a narrow electrochemical stability window of water.1 This constraint can, however, be relieved if electrochemical stability window is widened by deliberately controlling the composition of non-aqueous electrolyte systems. Redox couple is the core component in non-aqueous electrolyte systems, which should satisfy at least the following requirements; (i) high working voltage, (ii) high solubility in non-aqueous solvents, (iii) stability for high couloumbic efficiency and cycle retention, and (iv) facile molecular diffusion in solutions. It must be additionally beneficial if it can be used for both catholyte and anolyte. When such a single electrolyte component is used for RFBs, the loss of redox couple by side reactions can be greatly suppressed. A metal-multidentate complex, (nickel(II)-1,4,8,11-tetracyclotetradecane, Ni(cyclam)2+) has been tested if or not it satisfies the above requirements. The nickel complex is reduced and oxidized at -1.78 V and 0.74 V (vs. Fc/Fc+), respectively (Fig. 1). Hence, this redox couple can be used as a single electrolyte component for non-aqueous RFBs. The expected working voltage is as high as 2.52 V, which is much larger than those for conventional aqueous RFBs. The maximum solubility is ~0.4 M at room temperature. This value is again higher than those for the conventional metal-ligand complexes (0.1 M).2 A much enlarged energy density is thus expected with this RFB since it shows larger values for both cell voltage and capacity. This redox couple also exhibits a stable cycle performances. As seen in Fig. 1, the current profiles are not changed even after 50 cycles. Galvanostatic charge-discharge cycling is carried out in a non-flowing static cell. The coulombic efficiency is ~ 75% after 3 cycles.

Controlling Reversible Expansion of Li2O2 Formation and Decomposition by Modifying Electrolyte in Li-O2 Batteries

Peering into Batteries: Electrochemical Insight Through In Situ and Operando Methods over Multiple Length Scales

The proportion of renewable power generation in the world has been increasing in recent years. However, the fluctuations and uncertainties of renewable power generation bring a considerable challenge to future unit scheduling. Therefore, the generation flexibility in power systems becomes more critical as a large amount of renewable generation is integrated into power systems. The use of flexible generators with energy storage systems is one of the most efficient methods of improving power system flexibility. The primary purpose of this study is to explore the effect of generation flexibility on the cost of unit scheduling. A flexibility index is used to evaluate the generation flexibility in the Taiwan power system, and a multi-scenario analysis for renewable power integration is considered. This study also considers various system constraints, such as the unit commitment of actual hydro and thermal units, the scheduling of flexible internal combustion engines (ICEs) and energy storage systems, and possible curtailments of renewable power generation. According to the seasonable characteristics of renewable power generation, this study provides a suitable capacity for flexible ICE units and energy storage systems. Furthermore, this study demonstrates that the cost of unit scheduling is effectively reduced by increasing flexible ICE units and energy storage systems. The results of this study can be used as a reference for power systems in preparing flexible generating units and energy storage systems under the integration of a large amount of renewable power generation in the future.

The use of stationary electrochemical energy storage systems utilizing lithium-ion batteries has increased rapidly as the production scale has grown and price for lithium-ion batteries has decreased. These energy storage systems are crucial for maintaining grid resiliency, especially for grids operating with high penetration of renewable energy generation assets or with a variety of distributed energy generation and storage systems. One challenging factor for the adoption of battery energy storage systems is estimating the proper sizing, in terms of both power and energy, that minimizes total cost; properly sizing energy storage systems is difficult in simple cases, where a battery is costed independently of any other systems, but is extremely challenging when building loads and electrical generation by photovoltaic resources are also considered. REopt® is a techoeconomic optimization tool developed by NREL to address these challenges. Previously, battery degradation has been priced by simply assuming a 10-year replacement schedule for battery systems. However, this does not account for varying degradation trends observed across real-world batteries, or inform degradation-aware control strategies to optimize battery dispatch and extend lifetime.This work incorporates a battery life model into REopt. The battery life model is linearized so that it may be solvable within the constrains of a mixed-integer linear optimization problem. To achieve the best possible accuracy for lifetime estimates given these constraints, parameters for the battery life model in REopt are estimated by fitting 20-year simulations of battery life after identifying a state-space battery degradation model from accelerated aging data. Comparisons of battery life predicted in REopt and from the state-space battery degradation model are made to ensure validity of lifetime estimates made by REopt.Battery life impacts system cost through three decision variables: battery sizing, daily state-of-charge, and daily energy-throughput. The cost of battery degradation as a function of these control variables is then estimated assuming two possible maintenance strategies: replacement, where the entire battery system is replaced if cells reach an end-of-life capacity threshold; and augmentation, which establishes a fund to pay for continual purchase of new batteries to maintain the initial energy capacity of the system. These two strategies offer conservative (for replacement) and optimistic (for augmentation) bounds for total system cost. The degradation cost incurred by these strategies is then used to inform battery dispatch decisions, operating the battery in a degradation-aware manner that maximizes battery lifetime while also providing energy when economically favorable. Because the mixed-integer linear program has perfect foresight of future energy needs, batteries are often operated using ‘just-in-time’ charging, which is unrealistic, as no energy is left in the storage system to perform other energy services or to serve as emergency back-up power. To combat this, an inequality constraint on the average annual state-of-charge is imposed, and the sensitivity of system cost to average stored energy, e.g., the cost of system resiliency, can be quantified. Analysis of results has several conclusions, for instance, increasing battery capacity to provide more flexibility for dispatch, enabling the extension of useful life beyond 10 years and resulting in greater avoided utility costs per unit for energy storage while providing more energy storage for grid resiliency.

Electrochemical devices such as fuel cell, battery and supercapacitors are potential alternatives for energy conversion and storage apart from the burning of fossil fuels. Among the different energy storage systems, the rechargeable zinc-air battery displays great promise due to many attractive features; for example, high energy density, cost-effective and environmentally friendly design, as well as low operating risks 1. The excellent properties of rechargeable zinc-air batteries lead to potential applications in areas, such as stationary and portable power applications including electric vehicles 2,3. In a rechargeable zinc-air battery, oxygen evolution (OER) and oxygen reduction (ORR) reactions occur on the air electrode during battery charge and discharge, respectively. The sluggish reaction kinetics and large overpotential associated with OER and ORR greatly limit the performance of rechargeable zinc-air batteries 2,4. Among them, manganese oxide is a particularly interesting candidate due to its rich oxidation states, chemical compositions and crystal structures. MnO2 is the most common ORR electrocatalyst in commercial zinc–air batteries. As a result, an affordable, active and stable bifunctional catalyst is in great demands to improve to the performance of rechargeable zinc-air batteries. A rotating disc electrode (RDE) half-cell setup was used to investigate the ORR and OER catalytic activity of the samples. The working electrode was fabricated by casting Nafion-impregnated catalyst ink onto a glassy carbon disk electrode (5.6 mm in diameter). 10 mg of the catalyst was ultrasonically dispersed into 1mL ethanol 8 and uL 5 wt% Nafion solution to form a catalyst ink. 5uL of the catalyst ink was deposited on the disk and dried at room temperature. The working electrode was allowed to achieve a catalyst loading of 0.1 mg▪cm-2. Electrochemical activity of the samples was studied using linear sweep voltammetry. The working electrode was immersed in a glass cell containing 0.1 M KOH aqueous electrolyte. A platinum foil and an Hg/HgO electrode were used as the counter and reference electrodes, respectively. Catalyst activity toward the ORR and OER was evaluated in oxygen-saturated electrolyte solution from 1.67 to 0.1 V vs. RHE. The potential of the reference electrode was normalized with respect to the potential of the reversible hydrogen electrode (RHE). The rotation rate is 1600 rpm and the scan rate is 5 mV s-1. A commercial Pt/C catalyst (30 wt% platinum on carbon) was tested using the same procedure.First，in a typical synthesis of MnO2 nanotubes, 0.7902g KMnO4 and 2mL concentrated HCl(37%) were added to 50mL deionized water to form a precursor solution, then the solution was transferred into a 100mL Teflon-lined stainless steel autoclave. The autoclave was sealed and hydrothermally treated at 100，140，180 and 220oC for 12 hours. After the autoclave was cooled down to room temperature naturally, the MnO2 nanotube sample was collected and washed for 3-5 times with ethanol and deionized water, and dried in air at 70oC 24hours. The resulting products. were separated by centrifugation, washed with deionized water, dried at 60 for 5 h, and then calcined in air at 400℃ for 1 h. As shown in Fig.1, the onset potential for was detected at 0.94 V for MnO2 by 140℃, whereas it was 1.08 V and 0.78 V for MnO2 by 100,180 and 220℃, respectively. At 0.2 V, MnO2 by 100, 140,180 and 220℃afforded an ORR current density of 1.2mA cm-2 , 5.8mA cm-2, 5.8mA cm-2 and 5.2mA cm-2. Apart from the ORR activity, excellent OER activity is particularly critical for bi-functional catalysts. As shown , the onset potential for was detected at 1.45V for MnO2 by 140℃, whereas it was 1.51V,1.56V and 1.53Vfor MnO2by100,180and 220℃,the OER current density of MnO2 by 100, 140,180 and 220℃at 1. 7 V was 16, 9, 12 and 14mA cm- 2. The battery had an open circuit voltage of 1.35 V. At a voltage of 732 mV, it showed a high current density of 450mA cm-2. The peak power density was 293mW cm-2. the battery discharge and discharge performance noticeably at lower current densities and through long cycle times. In summary, MnO2 a new air electrode material have been synthesized. These hybrid nanomaterials display good bifunctional ORR/OER activity and cyclic stability in the discharge and charge process. Further studies are ongoing to improve the ZABs performance by manipulating the hybrid structure. References 1 S.I. Smedley, X.G. Zhang, J. Power Sources 165,897 (2007). 2 V. Neburchilov, H.J. Wang, J.J. Martin, W. Qu, J. Power Sources 195,1271 (2010). 3 J. Goldstein, I. Brown, B. Koretz, J. Power Sources 80 ,171 (1999) . 4 P. Sapkota, H. Kim, J. Ind. Eng. Chem. 15, 445(2009). Figure 1

The heat and/or mass transfer is crucial in various energy conversion and storage systems such as heat exchangers and energy storage systems, since they highly affect the efficiency of energy conversion and transport. Enhancing the heat and/or mass transfer within these systems is the most important means to improve system efficiency. Porous media have found wide application in enhancing the heat conduction, mass diffusion, or both, for different energy conversion and storage systems. In this chapter, a brief review on the application of different porous media for transport enhancement in various systems was made, indicating that using porous media is capable of enhancing the transport ability appreciably, sometimes being up to hundreds of times in some physical problems. This review could provide some insight into the transport enhancement design of various energy conversion and storage systems, which is especially important in the background of carbon neutralization.

CONNEXX SYSTEMS developed a novel hybrid energy storage system, bindbattery™, with a unique overcharge protection capability, high power and high energy capability and long cycle life at low cost without complex battery management system. bindbattery™ consists of lithium-ion battery units and aqueous electrolyte battery units. The two units are connected in parallel and form a virtual cell. The multiple virtual cells are connected in series and in parallel to meet specifications of each application. An aqueous electrolyte battery could be chosen from a nickel-hydride battery, lead-acid battery or other form of aqueous batteries depending on requirements of applications. Hybridization with an aqueous electrolyte battery makes bindbattery™ tolerable to abusive conditions such as reverse directional high current pulse or overcharge current. Benefits of bindbattery™ include: 1) Safety: The lithium-ion battery is protected from the devastating overcharge by aqueous batteries connected in parallel. The aqueous battery unit consumes overcharge energy through the aqueous electrolyte decomposition (electrolysis). The oxygen evolved at the positive electrode recombines with hydrogen on the negative electrode and reforms water. By connecting the lead-acid battery and lithium-ion battery in parallel, the lead-acid battery effectively protects lithium-ion battery from overcharge by absorbing the overcharge current through the chemical reaction. Thus, bindbattery™ does not require complex electronic protection circuit to protect from overcharge. In other words, the bindbattery™ configuration makes the battery system intrinsically safe. This simplifies construction of the bindbattery™, and reduces both the cost and the weight and makes the battery suitable for large scale stationary applications. 2) Power performance: As a result of high power characteristics of both high power lithium-ion batteries and lead-acid batteries, bindbattery™ has a high power capability. 3) Cycle life improvement: The lead-acid battery is an inexpensive battery but its cycle life is poor compared to the lithium-ion battery. The lithium-ion battery has higher discharge voltage than the lead-acid battery, therefore lithium-ion battery discharges prior to the lead-acid battery in bindbattery™. Thus bindbattery™ provides an excellent cycle life in the same manner as the lithium-ion battery. 4) High energy density: bindbattery™ can provide a larger energy compared to the lead-acid battery alone as a result of the hybridization with lithium-ion battery. 5) Low temperature performance improvement: The lead-acid battery has excellent low temperature capability. At subzero temperature, lithium-ion battery is not able to discharge immediately. In bindbattery™, the lead-acid battery discharges first and provides warm-up time for the lithium-ion battery. 6) Float charge capability: Like other aqueous batteries, bindbattery™ can be used in the float-charge mode. 7) Cost improvement: Use of lead-acid battery as an aqueous battery units lowers the cost significantly. Elimination of electrical protection switches and battery management units contribute to the cost reduction. These unique features make bindbattery™ the most suitable energy storage system for stationary applications including storage system for renewable energy, demand shifting and frequency regulation. We developed 20 kWh bindbattery™ module for stationary applications such as solar energy or wind energy storage. The module will comprise a larger scale storage system by connecting multiple of the modules in parallel or in series. The simplified control method and low cost also make bindbattery™ a remarkable choice for car applications.

Developing efficient energy storage and conversion applications is vital to address fossil energy depletion and global warming. Li–O2 batteries are one of the most promising devices because of their ultra-high energy density. To overcome their practical difficulties including low specific capacities, high overpotentials, limited rate capability and poor cycle stability, an intensive search for highly efficient electrocatalysts has been performed. Recently, it has been reported that heterostructured catalysts exhibit significantly enhanced activities toward the oxygen reduction reaction and oxygen evolution reaction, and their excellent performance is not only related to the catalyst materials themselves but also the special hetero-interfaces. Herein, an overview focused on the electrocatalytic functions of heterostructured catalysts for non-aqueous Li–O2 batteries is presented by summarizing recent research progress. Reduction mechanisms of Li–O2 batteries are first introduced, followed by a detailed discussion on the typical performance enhancement mechanisms of the heterostructured catalysts with different phases and heterointerfaces, and the various heterostructured catalysts applied in Li–O2 batteries are also intensively discussed. Finally, the existing problems and development perspectives on the heterostructure applications are presented.