Constructing Metal(II)-Sulfate Site Catalysts toward Low Overpotential Carbon Dioxide Electroreduction to Fuel Chemicals

Precise regulation of the active site structure is an important means to enhance the activity and selectivity of catalysts in CO2 electroreduction. Here, we creatively introduce anionic groups, which can not only stabilize metal sites with strong coordination ability but also have rich interactions with protons at active sites to modify the electronic structure and proton transfer process of catalysts. This strategy helps to convert CO2 into fuel chemicals at low overpotentials. As a typical example, a composite catalyst, CuO/Cu-NSO4/CN, with highly dispersed Cu(II)-SO4 sites has been reported, in which CO2 electroreduction to formate occurs at a low overpotential with a high Faradaic efficiency (-0.5 V vs. RHE, FEHCOO-=87.4%). Pure HCOOH is produced with an energy conversion efficiency of 44.3% at a cell voltage of 2.8 V. Theoretical modeling demonstrates that sulfate promotes CO2 transformation into a carboxyl intermediate followed by HCOOH generation, whose mechanism is significantly different from that of the traditional process via a formate intermediate for HCOOH production.

High-Rate Nonaqueous Mg-CO2 Batteries Enabled by Mo2 C-Nanodot-Embedded Carbon Nanofibers

The widespread acceptance of nonaqueous rechargeable metal-gas batteries, known for their remarkably high theoretical energy density, faces obstacles such as poor reversibility and low energy efficiency under high charge-discharge current densities. To tackle these challenges, a novel catalytic cathode architecture for Mg-CO2 batteries, fabricated using a one-pot electrospinning method followed by heat treatment, is presented. The resulting structure features well-dispersed molybdenum carbide nanodots embedded within interconnected carbon nanofibers, forming a 3D macroporous conducting network. This cathode design enhances the volumetric efficiency, enabling effective discharge product deposition, while also improving electrical properties and boosting catalytic activity. This enhancement results in high discharge capacities and excellent rate capabilities, while simultaneously minimizing voltage hysteresis and maximizing energy efficiency. The battery exhibits a stable cycle life of over 250 h at a current density of 200 mA g-1 with a low initial charge-discharge voltage gap of 0.72 V. Even at incredibly high current densities, reaching 1600 mA g-1 , the battery maintains exceptional performance. These findings highlight the crucial role of cathode architecture design in enhancing the performance of Mg-CO2 batteries and hold promise for improving other metal-gas batteries that involve deposition-decomposition reactions.

Partially Nitrided Ni Nanoclusters Achieve Energy-Efficient Electrocatalytic CO2 Reduction to CO at Ultralow Overpotential

Electrocatalytic CO₂ reduction reaction (CO₂ RR) offers a promising strategy to lower CO₂ emission while producing value-added chemicals. A great challenge facing CO₂ RR is how to improve energy efficiency by reducing overpotentials. Herein, partially nitrided Ni nanoclusters (NiN_x ) immobilized on N-doped carbon nanotubes (NCNT) for CO₂ RR are reported, which achieves the lowest onset overpotential of 16 mV for CO₂ -to-CO and the highest cathode energy efficiency of 86.9% with CO Faraday efficiency >99.0% to date. Interestingly, NiN_x /NCNT affords a CO generation rate of 43.0 mol g^-1  h^-1 at a low potential of -0.572 V (vs RHE). DFT calculations reveal that the NiN_x nanoclusters favor *COOH formation with lower Gibbs free energy than isolated Ni single-atom, hence lowering CO₂ RR overpotential. As NiN_x /NCNT is applied to a membrane electrode assembly system coupled with oxygen evolution reaction, a cell voltage of only 2.13 V is required to reach 100 mA cm^-2 , with total energy efficiency of 62.2%.

Low Overpotential Electrochemical Reduction of CO2 to Ethanol Enabled by Cu/CuxO Nanoparticles Embedded in Nitrogen-Doped Carbon Cuboids

The electrochemical conversion of CO₂ into value-added chemicals is a promising approach for addressing environmental and energy supply problems. In this study, electrochemical CO₂ catalysis to ethanol is achieved using incorporated Cu/Cu_xO nanoparticles into nitrogenous porous carbon cuboids. Pyrolysis of the coordinated Cu cations with nitrogen heterocycles allowed Cu nanoparticles to detach from the coordination complex but remain dispersed throughout the porous carbon cuboids. The heterogeneous composite Cu/Cu_xO-PCC-0h electrocatalyst reduced CO₂ to ethanol at low overpotential in 0.5 M KHCO₃, exhibiting maximum ethanol faradaic efficiency of 50% at -0.5 V vs. reversible hydrogen electrode. Such electrochemical performance can be ascribed to the synergy between pyridinic nitrogen species, Cu/Cu_xO nanoparticles, and porous carbon morphology, together providing efficient CO₂ diffusion, activation, and intermediates stabilization. This was supported by the notably high electrochemically active surface area, rich porosity, and efficient charge transfer properties.

Superstructures of Zeolitic Imidazolate Frameworks to Single- and Multiatom Sites for Electrochemical Energy Conversion

The exploration of electrocatalysts with high catalytic activity and long-term stability for electrochemical energy conversion is significant yet remains challenging. Zeolitic imidazolate framework (ZIF)-derived superstructures are a source of atomic-site-containing electrocatalysts. These atomic sites anchor the guest encapsulation and self-assembly of aspheric polyhedral particles produced using microreactor fabrication. This review provides an overview of ZIF-derived superstructures by highlighting some of the key structural types, such as open carbon cages, 1D superstructures, hollow structures, and the interconversion of superstructures. The fundamentals and representative structures are outlined to demonstrate the role of superstructures in the construction of materials with atomic sites, such as single- and dual-atom materials. Then, the roles of ZIF-derived single-atom sites for the electroreduction of CO₂ and electrochemical synthesis of H₂ O₂ are discussed, and their electrochemical performance for energy conversion is outlined. Finally, the perspective on advancing single- and dual-atom electrode-based electrochemical processes with enhanced redox activity and a low-impedance charge-transfer pathway for cathodes is provided. The challenges associated with ZIF-derived superstructures for electrochemical energy conversion are discussed.

Sn Dopants with Synergistic Oxygen Vacancies Boost CO2 Electroreduction on CuO Nanosheets to CO at Low Overpotential

Using the electrochemical CO₂ reduction reaction (CO₂RR) with Cu-based electrocatalysts to achieve carbon-neutral cycles remains a significant challenge because of its low selectivity and poor stability. Modulating the surface electron distribution by defects engineering or doping can effectively improve CO₂RR performance. Herein, we synthesize the electrocatalyst of V_o-CuO(Sn) nanosheets containing oxygen vacancies and Sn dopants for application in CO₂RR-to-CO. Density functional theory calculations confirm that the incorporation of oxygen vacancies and Sn atoms substantially reduces the energy barrier for *COOH and *CO intermediate formation, which results in the high efficiency, low overpotential, and superior stability of the CO₂RR to CO conversion. This electrocatalyst possesses a high Faraday efficiency (FE) of 99.9% for CO at a low overpotential of 420 mV and a partial current density of up to 35.22 mA cm^-2 at -1.03 V versus reversible hydrogen electrode (RHE). The FE_CO of V_o-CuO(Sn) could retain over 95% within a wide potential area from -0.48 to -0.93 V versus RHE. Moreover, we obtain long-term stability for more than 180 h with only a slight decay in its activity. Therefore, this work provides an effective route for designing environmentally friendly electrocatalysts to improve the selectivity and stability of the CO₂RR to CO conversion.

Defects engineering on CrOOH by Ni doping for boosting electrochemical oxygen evolution reaction

The design and construction of active centres are key to exploring advanced electrocatalysts for oxygen evolution reaction (OER). In this work, we demonstrate thein situconstruction of point defects on CrOOH by Ni doping (Ni-CrOOH/NF). Compared with pure CrOOH/NF, Ni-CrOOH/NF showed enhanced OER activity. The effect of the amount of Ni introduced on the OER performance was investigated. Ni_0.2-CrOOH/NF, the best introduction of Ni, uses a low overpotential of 253 mV to achieve a current density of 10 mA cm^-2with a high turnover frequency of 0.27 s^-1in 1.0 M NaOH. In addition, the electrocatalytic performance of Ni_0.2-CrOOH/NF showed little deterioration after 1000-cycle cyclic voltammetry scanning. In the potentiostatic test, activity was stable for at least 20 h.

Grain Boundary-Derived Cu+ /Cu0 Interfaces in CuO Nanosheets for Low Overpotential Carbon Dioxide Electroreduction to Ethylene

Electrochemical CO₂ reduction reaction can be used to produce value-added hydrocarbon fuels and chemicals by coupling with clean electrical energy. However, highly active, selective, and energy-efficient CO₂ conversion to multicarbon hydrocarbons, such as C₂ H₄ , remains challenging because of the lack of efficient catalysts. Herein, an ultrasonication-assisted electrodeposition strategy to synthesize CuO nanosheets for low-overpotential CO₂ electroreduction to C₂ H₄ is reported. A high C₂ H₄ Faradaic efficiency of 62.5% is achieved over the CuO nanosheets at a small potential of -0.52 V versus a reversible hydrogen electrode, corresponding to a record high half-cell cathodic energy efficiency of 41%. The selectivity toward C₂ H₄ is maintained for over 60 h of continuous operation. The CuO nanosheets are prone to in situ restructuring during CO₂ reduction, forming abundant grain boundaries (GBs). Stable Cu⁺ /Cu⁰ interfaces are derived from the low-coordinated Cu atoms in the reconstructed GB regions and act as highly active sites for CO₂ reduction at low overpotentials. In situ Raman spectroscopic analysis and density functional theory computation reveal that the Cu⁺ /Cu⁰ interfaces offer high *CO surface coverage and lower the activation energy barrier for *CO dimerization, which, in synergy, facilitates CO₂ reduction to C₂ H₄ at low overpotentials.

Transient Solid-State Laser Activation of Indium for High-Performance Reduction of CO2 to Formate

Deficiencies in understanding the local environment of active sites and limited synthetic skills challenge the delivery of industrially-relevant current densities with low overpotentials and high selectivity for CO₂ reduction. Here, a transient laser induction of metal salts can stimulate extreme conditions and rapid kinetics to produce defect-rich indium nanoparticles (L-In) is reported. Atomic-resolution microscopy and X-ray absorption disclose the highly defective and undercoordinated local environment in L-In. In a flow cell, L-In shows a very small onset overpotential of ≈92 mV and delivers a current density of ≈360 mA cm^-2 with a formate Faradaic efficiency of 98% at a low potential of -0.62 V versus RHE. The formation rate of formate reaches up to 6364.4 µmol h^-1mgIn-1$mg_{{\rm{In}}}^{--1}$ , which is nearly 39 folds higher than that of commercial In (160.7 µmol h^-1mgIn-1$mg_{{\rm{In}}}^{--1}$ ), outperforming most of the previous results that have been reported under KHCO₃ environments. Density function theory calculations suggest that the defects facilitate the formation of *OCHO intermediate and stabilize the *HCOOH while inhibiting hydrogen adsorption. This study suggests that transient solid-state laser induction provides a facile and cost-effective approach to form ligand-free and defect-rich materials with tailored activities.

Revealing the Potential of Ternary Medium-Entropy Alloys as Exceptional Electrocatalysts toward Nitrogen Reduction: An Example of Heusler Alloys

With less energy consumption and environmental pollution, electrochemical ammonia synthesis is regarded as the most promising way to replace the industrial Haber-Bosch process, which greatly contributes to global energy consumption and CO₂ emission. At present, the best metal electrocatalyst for N₂ fixation is ruthenium although its performance still suffers from a low Faradaic efficiency and a high overpotential. Alloy engineering is a promising way to discover more metal-based electrocatalysts for dinitrogen reduction reaction (N2RR), and almost all reported alloy catalysts so far are binary alloys. In this work, we proposed a large group of ternary alloy electrocatalysts (Heusler alloys) for N2RR and demonstrated their superior catalytic performance. As an example, alloying Ru with Mn and Si led to a reduced Ru-Ru distance on the surface, which facilitates an uncommon horizontal adsorption mode of N₂ and results in effective activation of N₂ molecules. The theoretical overpotential of N2RR on Ru₂MnSi(100-Ru) is only around 0.28 V, which ranks among the best reported results, and the usage of precious Ru is greatly reduced. Meanwhile, the adsorption of N₂ on Ru₂MnSi(100-Ru) was much stronger than that of protons, and it also took less energy to drive N2RR than the hydrogen evolution reaction (HER), making HER less competitive on this catalyst. Considering the successful synthesis of numerous Heusler alloys including the six members mentioned here, our work provided a wider range of practical and excellent N2RR electrocatalysts in terms of both catalytic performance and economical cost.

Ordered Vacancies on the Body-Centered Cubic PdCu Nanocatalysts

Defect engineering has become one of the important considerations in today's electrocatalyst design. However, the vacancies in the ordered crystal structure (especially body-centered cubic (bcc) and the effect of ordered vacancies (OVs) on the electronic fabric have not been researched yet. In this work, we report the inaugural time of the generation of OVs in the bcc architecture and discuss the insight of the modulation system of the material and its part in the electrochemical N₂ reduction reaction (NRR). OV-PdCu-2 achieves the highest Faradaic efficiency value of 21.5% at 0.05 V versus RHE. When the potential increases to 0 V versus RHE, the highest ammonia yield is 55.54 μg h^-1 mg_cat^-1, which is significantly better than the unetched PdCu nanoparticles (12.83 μg h^-1 mg_cat^-1). It is the latest reported catalyst to date in the NRR process at 0 V versus RHE (see Supporting Information).

Surface Engineering of a Mg Electrode via a New Additive to Reduce Overpotential

In nonaqueous Mg batteries, inactive adsorbed species and the passivation layer formed from the reactive Mg with impurities in the electrolyte seriously affect the Mg metal/electrolyte interface. These adlayers can impede the passage of Mg²⁺ ions, leading to a high Mg plating/stripping overpotential. Herein, we report the properties of a new additive, bismuth triflate (Bi(OTf)₃), for synthesizing a chlorine-free Mg electrolyte to enhance Mg plating/stripping from initial cycles. The beneficial effect of Bi(OTf)₃ can be ascribed to Bi/Mg₃Bi₂ formed in situ on the Mg metal surface, which increases the charge transfer during the on-off transition by reducing the adsorption of inactive species on the Mg surface and enhancing the resistance of the reactive surface to passivation. This simple method provides a new avenue to improve the compatibility between the Cl-free Mg electrolyte and the Mg metal anode.

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.

Engineering Ag-Nx Single-Atom Sites on Porous Concave N-Doped Carbon for Boosting CO2 Electroreduction

The electrochemical CO₂ reduction reaction (CO₂RR) offers an environmentally benign pathway for renewable energy conversion and further regulation of the environmental CO₂ concentration to achieve carbon cycling. However, developing desired electrocatalysts with high CO Faradaic efficiency (FE_CO) at an ultralow overpotential remains a grand challenge. Herein, we report an effective CO₂RR electrocatalyst that features Ag single-atom coordinated with three nitrogen atoms (Ag₁-N₃) anchored on porous concave N-doped carbon (Ag₁-N₃/PCNC), which is identified by X-ray absorption spectroscopy. Ag₁-N₃/PCNC shows a low CO₂RR onset potential of -0.24 V, high maximum FE_CO of 95% at -0.37 V, and high CO partial current density of 7.6 mA cm^-2 at -0.55 V, exceeding most of the previous Ag electrocatalysts. The in situ infrared absorption spectra technique proves that Ag₁-N₃ single-atom sites have sole linear-adsorbed CO and can easily desorb *CO species to achieve the highest CO selectivity in comparison with the corresponding counterparts. This work provides significant inspiration on boosting CO₂RR by tuning the active center at an atomic level to achieve a specific absorption with an intermediate.

In situsynthesis of Fe-doped CrOOH nanosheets for efficient electrocatalytic water oxidation

The oxygen evolution reaction (OER) is a process in electrochemical water splitting with sluggish kinetics that needs efficient non-noble-metal electrocatalysts. There have been few studies of CrOOH electrocatalysts for water oxidation due to their low performance. Herein,in situsynthesized Fe-doped CrOOH nanosheets on Ni foam (Fe-CrOOH/NF) were designed as electrocatalysts and performance in the OER was obviously improved. The effect of the amount of Fe doping was also investigated. Experiments revealed that the best performance of Fe-CrOOH/NF requires low overpotentials of 259 mV to reach 20 mA cm^-2together with a turnover frequency of 0.245 s^-1in 1.0 M KOH, which may suggest a new direction for the development of Fe-doped OER electrocatalysts.

A Bifunctional Photo-Assisted Li-O2 Battery Based on a Hierarchical Heterostructured Cathode

Photo-assisted charging is considered an effective approach to reducing the overpotential in lithium-oxygen (Li-O₂ ) batteries. However, the utilization of photoenergy during the discharge process in a Li-O₂ system has been rarely reported, and the functional mechanism of such a process remains unclear. Herein, a novel bifunctional photo-assisted Li-O₂ system is established by employing a hierarchical TiO₂ -Fe₂ O₃ heterojunction, in which the photo-generated electrons and holes play key roles in reducing the overpotential in the discharging and charging processes, respectively. Moreover, the morphology of the discharge product (Li₂ O₂ ) can be modified via the dense surface electrons of the cathode under illumination, resulting in promoted decomposition kinetics of Li₂ O₂ during the charging progress. Accordingly, the output and input energies of the battery can be tuned by illumination, giving an ultralow overpotential of 0.19 V between the charge and discharge plateaus with excellent cyclic stability (retaining a round-trip efficiency of ≈86% after 100 cycles). The investigation of the bifunctional photo-assisted process presented here provides significant insight into the mechanism of the photo-assisted Li-O₂ battery and addresses the overpotential bottleneck in this system.

Reducing Oxygen Evolution Reaction Overpotential in Cobalt-Based Electrocatalysts via Optimizing the "Microparticles-in-Spider Web" Electrode Configurations

Sluggish kinetics of the multielectron transfer process is still a bottleneck for efficient oxygen evolution reaction (OER) activity, and the reduction of reaction overpotential is crucial to boost reaction kinetics. Herein, a correlation between the OER overpotential and the cobalt-based electrode composition in a "Microparticles-in-Spider Web" (MSW) superstructure electrode is revealed. The overpotential is dramatically decreased first and then slightly increased with the continuous increase ratio of Co/Co₃ O₄ in the cobalt-based composite electrode, corresponding to the dynamic change of electrochemically active surface area and charge-transfer resistance with the electrode composition. As a proof-of-concept, the optimized electrode displays a low overpotential of 260 mV at 10.0 mA cm^-2 in alkaline conditions with a long-time stability. This electrochemical performance is comparable and even superior to the most currently reported Co-based OER electrocatalysts. The remarkable electrocatalytic activity is attributed to the optimization of the electrochemically active sites and electron transfer in the MSW superstructure. Theoretical calculations identify that the metallic Co and Co₃ O₄ surface catalytic sites play a vital role in improving electron transport and reaction Gibbs free energies for reducing overpotential, respectively. A general way of boosting OER kinetics via optimizing the electrode configurations to mitigate reaction overpotential is offered in this study.

Self-Supportive Mesoporous Ni/Co/Fe Phosphosulfide Nanorods Derived from Novel Hydrothermal Electrodeposition as a Highly Efficient Electrocatalyst for Overall Water Splitting

Low cost and highly efficient bifuctional catalysts for overall water electrolysis have drawn considerable interests over the past several decades. Here, rationally synthesized mesoporous nanorods of nickel-cobalt-iron-sulfur-phosphorus composites are tightly self-supported on Ni foam as a high-performance, low cost, and stable bifunctional electrocatalyst for water electrolysis. The targeted designing and rational fabrication give rise to the nanorod-like morphology with large surface area and excellent conductivity. The NiCoFe-PS nanorod/NF can reach 10 mA cm^-2 at a small overpotential of 195 mV with a Tafel slope of 40.3 mV dec^-1 for the oxygen evolution reaction and 97.8 mV with 51.8 mV dec^-1 for the hydrogen evolution reaction. Thus, this bifunctional catalyst shows low potentials of 1.52 and 1.76 V at 10 and 50 mA cm^-2 toward overall water splitting with excellent stability for over 200 h, which are superior to most non-noble metal-based bifunctional electrocatalysts recently. This work provides a new strategy to fabricate multiple metal-P/S composites with the mesoporous nanorod-like structure as bifunctional catalysts for overall water splitting.

A 4 V Class Potassium Metal Battery with Extremely Low Overpotential

K metal anodes usually have a low Coulombic efficiency and poor safety owing to their large volume variation and high chemical reactivity. In this study, a three-dimensional K (3D-K) anode is formed by plating metallic K into hollow N-doped C polyhedrons/graphene (HNCP/G). Then a Sn-based solid-electrolyte interphase layer is conformably coated onto the surface of 3D-K to construct Sn@3D-K. Compared with the typical K-foil anode, the Sn@3D-K anode can significantly reduce the interfacial resistance, improve the K⁺ ion transport mobility, reduce parasitic reactions, and suppress the formation of K dendrites. Meanwhile, HNCP/G serves as a chemically stable, conductive host to accommodate the volume expansion/shrinkage of Sn@3D-K. Owing to these merits, the symmetric Sn@3D-K cell exhibits low voltage hysteresis (9 mV at 0.2 mA cm^-2 after 500 h; 31 mV at 1 mA cm^-2 after 100 h). When paired with a Prussian blue (PB)/graphene cathode, the K_1.56Mn[Fe(CN)₆]_1.08/G∥Sn@3D-K battery delivers an average discharge plateau of 4.02 V, an ultralow overpotential of 0.01 V, and a high specific capacity of 147.2 mAh g^-1, approaching the theoretical value of K₂MnFe(CN)₆ (156 mAh g^-1). A 4 V class K metal battery that exhibits extremely low overpotential and high specific capacity, which are the best among previously reported PB-based K batteries, is proposed.

A Co-Doped MnO2 Catalyst for Li-CO2 Batteries with Low Overpotential and Ultrahigh Cyclability

Li-CO₂ batteries can not only capture CO₂ to solve the greenhouse effect but also serve as next-generation energy storage devices on the merits of economical, environmentally-friendly, and sustainable aspects. However, these batteries are suffering from two main drawbacks: high overpotential and poor cyclability, severely postponing the acceleration of their applications. Herein, a new Co-doped alpha-MnO₂ nanowire catalyst is prepared for rechargeable Li-CO₂ batteries, which exhibits a high capacity (8160 mA h g^-1 at a current density of 100 mA g^-1 ), a low overpotential (≈0.73 V), and an ultrahigh cyclability (over 500 cycles at a current density of 100 mA g^-1 ), exceeding those of Li-CO₂ batteries reported so far. The reaction mechanisms are interpreted depending on in situ experimental observations in combination with density functional theory calculations. The outstanding electrochemical properties are mostly associated with a high conductivity, a large fraction of hierarchical channels, and a unique Co interstitial doping, which might be of benefit for the diffusion of CO₂ , the reversibility of Li₂ CO₃ products, and the prohibition of side reactions between electrolyte and electrode. These results shed light on both CO₂ fixation and new Li-CO₂ batteries for energy storage.

Ironing Controllable Lithium into Lithiotropic Carbon Fiber Fabric: A Novel Li-Metal Anode with Improved Cyclability and Dendrite Suppression

Lithium metal as an anode in lithium-ion batteries is attracting more attention because of the high gravimetric/volumetric energy density and low electrochemical potential. However, the irreversible Li plating/striping can reduce the cycling capability and very possibly introduce dendrite growth, thus leading to a series of issues such as infinite volume change, low Coulombic efficiency, and uncontrollable solid electrolyte interphase. Here, we report a novel, single-side Li-infused carbon fiber fabric (LiCFF) with a controllable, minimized Li loading, which shows a highly reversible plating/stripping with an extremely low overpotential of less than 30 mV (Li foil: >1.0 V over 50 cycles) upon >3000 cycles (6000 and 2000 h) at 1 and 3 mA/cm² in symmetric cells, respectively. With a high areal capacity up to 10 mA h/cm² and a high current density of 10 mA/cm², the cell still shows a minimum overpotential of 150-175 mV after 250 cycles (500 h). Full-cell batteries using the LiCFF as "all-in-one" anodes without the additional slurry-making process and nickel-manganese-cobalt oxide (NMC) as cathodes exhibit an improved capacity retention when compared with Li foil: 32% at 0.5 C and 119% at 1.0 C capacity improved after 100 cycles. In parallel, the mossy/dendritic Li on the LiCFF was largely suppressed, which was confirmed using in situ observations of Li plating/striping in a capillary cell. The excellent electronic conductivity of the carbon fabric leads to small contact/transfer resistances of 3.4/3.8 Ω (Li foil: 4.1/44.4 Ω), enabling a drastically lowered energy barrier for Li nucleation/growth. Thus, a uniform current distribution results in forming a homogeneous Li layer instead of forming dendrites. The current LiCFF as the anode with controllable Li (n/p ratio), improved cycling stability, mitigated dendrite formation, and flexibility displays promising applications in versatile Li-metal batteries such as Li-NMC, Li-S, and Li-O₂.

Electrocatalytic CO2 Reduction with a Ruthenium Catalyst in Solution and on Nanocrystalline TiO2

A Ru^II complex [Ru(PO₃ Et₂ -ph-tpy)(6-mbpy)(NCCH₃ )]²⁺ [PO₃ Et₂ -ph-tpy=diethyl(4-[(2,2':6',2''-terpyridin)-4'-yl]phenyl)phosphonate; 6-mbpy=6-methyl-2,2'-bipyridine] is explored as a molecular catalyst for electrocatalytic CO₂ reduction in both a homogeneous solution and, as a phosphonated derivative, on nanocrystalline-TiO₂ surfaces. In CH₃ CN, the complex acts as a selective electrocatalyst for reduction of CO₂ to CO at a low overpotential of 340 mV but with a limited turnover number (TON). An enhancement in reactivity was observed by immobilizing the phosphonated derivative of the catalyst on a nanocrystalline-TiO₂ electrode surface, with the catalyst surface protected by a thin overlayer of NiO. The surface-functionalized electrode was characterized by X-ray photoelectron and diffuse reflectance spectroscopies (XPS and DRS). Electrocatalytic reduction of CO₂ to CO occurred at -1.65 V versus Fc^+/0 with a TON of 237 per catalyst site during 4 h of electrocatalysis. Post-catalysis XPS measurements reveal that the molecular structure of the catalyst is retained on TiO₂ after the long-term electrocatalysis.

Ultrafine Metallic Nickel Domains and Reduced Molybdenum States Improve Oxygen Evolution Reaction of NiFeMo Electrocatalysts

An electrocatalyst for oxygen evolution reaction (OER) is essential in the realization of renewable energy conversion technologies, but its large overpotential, slow charge transfer, and degradation of surface reaction sites are yet to be overcome. Here, it is found that the metallic nickel domains and high-valence reduced molybdenum ions of NiFeMo electrocatalysts grown on a 3D conductive and porous electrode without using binders enable ultrahigh performance in OER. High resolution-transmission electron microscope and extended X-ray absorption fine structure analyses show that metallic nickel domains with Ni-Ni bonds are generated on the catalyst surface via a dry synthesis using nitrogen plasma. Also, Mo K-edge X-ray absorption near-edge spectroscopy reveals that Mo⁶⁺ ions are reduced into high-valence modulating Mo⁴⁺ ions. With the metallic nickel domains facilitating the adsorption of oxygen intermediates to low-coordinated Ni⁰ and the Mo⁴⁺ pulling their electrons, the catalyst exhibits about 60-fold higher activity than a Mo-free NiFe catalyst, while giving about threefold faster charge transfer along with longer stability over 100 h and repeated 100 cycles compared to a bare NiFeMo catalyst. Additionally, these metallic domains and high-valence modulating metal ions are exhibited to give high Faradaic efficiency over 95%.

A Quasi-Solid-State Flexible Fiber-Shaped Li-CO2 Battery with Low Overpotential and High Energy Efficiency

The rapid development of wearable electronics requires a revolution of power accessories regarding flexibility and energy density. The Li-CO₂ battery was recently proposed as a novel and promising candidate for next-generation energy-storage systems. However, the current Li-CO₂ batteries usually suffer from the difficulties of poor stability, low energy efficiency, and leakage of liquid electrolyte, and few flexible Li-CO₂ batteries for wearable electronics have been reported so far. Herein, a quasi-solid-state flexible fiber-shaped Li-CO₂ battery with low overpotential and high energy efficiency, by employing ultrafine Mo₂ C nanoparticles anchored on a carbon nanotube (CNT) cloth freestanding hybrid film as the cathode, is demonstrated. Due to the synergistic effects of the CNT substrate and Mo₂ C catalyst, it achieves a low charge potential below 3.4 V, a high energy efficiency of ≈80%, and can be reversibly discharged and charged for 40 cycles. Experimental results and theoretical simulation show that the intermediate discharge product Li₂ C₂ O₄ stabilized by Mo₂ C via coordinative electrons transfer should be responsible for the reduction of overpotential. The as-fabricated quasi-solid-state flexible fiber-shaped Li-CO₂ battery can also keep working normally even under various deformation conditions, giving it great potential of becoming an advanced energy accessory for wearable electronics.

Fabrication of Lithiophilic Copper Foam with Interfacial Modulation toward High-Rate Lithium Metal Anodes

Although metallic lithium is regarded as an ideal anode material for high-energy-density batteries, the low cycling efficiency and safety issues hinder its practical application. In this study, a three-dimensional (3D) lithium composite anode was developed through infusing molten lithium inside the Cu foam anchored by ZnO nanoparticles. The introduced ZnO layer provides the driving force for infusion, leading to the spontaneous wetting of molten lithium. Benefiting from well-confined preloaded lithium in the Cu network, the anode displays ultralow internal resistance and stabilized interface. The fabricated anode for the symmetric cell shows extraordinarily low overpotential at high current densities (15, 33, and 50 mV at 3, 5, and 8 mA cm^-2 after 100 cycles, respectively). When paired with Li₄Ti₅O₁₂ electrode, the half-type cell demonstrates superior rate capability and long-term cycling stability after 1000 cycles at an ultrahigh rate of 10C. To the best of our knowledge, this anode shows the lowest overpotential and the highest rate capacity ever reported for 3D design anodes, confirming their great potential as lithium metal anodes.

Textile Inspired Lithium-Oxygen Battery Cathode with Decoupled Oxygen and Electrolyte Pathways

The lithium-air (Li-O₂ ) battery has been deemed one of the most promising next-generation energy-storage devices due to its ultrahigh energy density. However, in conventional porous carbon-air cathodes, the oxygen gas and electrolyte often compete for transport pathways, which limit battery performance. Here, a novel textile-based air cathode is developed with a triple-phase structure to improve overall battery performance. The hierarchical structure of the conductive textile network leads to decoupled pathways for oxygen gas and electrolyte: oxygen flows through the woven mesh while the electrolyte diffuses along the textile fibers. Due to noncompetitive transport, the textile-based Li-O₂ cathode exhibits a high discharge capacity of 8.6 mAh cm^-2 , a low overpotential of 1.15 V, and stable operation exceeding 50 cycles. The textile-based structure can be applied to a range of applications (fuel cells, water splitting, and redox flow batteries) that involve multiple phase reactions. The reported decoupled transport pathway design also spurs potential toward flexible/wearable Li-O₂ batteries.

Self-Supported Nickel Iron Layered Double Hydroxide-Nickel Selenide Electrocatalyst for Superior Water Splitting Activity

The design of efficient, low-cost, and stable electrocatalyst systems toward energy conversion is highly demanding for their practical use. Large scale electrolytic water splitting is considered as a promising strategy for clean and sustainable energy production. Herein, we report a self-supported NiFe layered double hydroxide (LDH)-NiSe electrocatalyst by stepwise surface-redox-etching of Ni foam (NF) through a hydrothermal process. The as-prepared NiFe LDH-NiSe/NF catalyst exhibits far better performance in alkaline water oxidation, proton reduction, and overall water splitting compared to NiSe_x/NF or NiFe LDH/NF. Only 240 mV overpotential is required to obtain a water oxidation current density of 100 mA cm^-2, whereas the same for the hydrogen evolution reaction is 276 mV in 1.0 M KOH. The synergistic effect from NiSe and NiFe LDH leads to the evolution of a highly efficient catalyst system for water splitting by achieving 10 mA cm^-2 current density at only 1.53 V in a two-electrode alkaline electrolyzer. In addition, the designed electrode produces stable performance for a long time even at higher current density to demonstrate its robustness and prospective as a real-life energy conversion system.

Encapsulation of Metallic Na in an Electrically Conductive Host with Porous Channels as a Highly Stable Na Metal Anode

Room-temperature Na ion batteries (NIBs) have attracted great attention because of the widely available, abundant sodium resources and potentially low cost. Currently, the challenge of the NIB development is due primarily to the lack of a high-performance anode, while the Na metal anode holds great promise considering its highest specific capacity of 1165 mA h/g and lowest anodic potential. However, an uneven deposit, relatively infinite volume change, and dendritic growth upon plating/stripping cycles cause a low Coulombic efficiency, poor cycling performance, and severe safety concerns. Here, a stable Na carbonized wood (Na-wood) composite anode was fabricated via a rapid melt infusion (about 5 s) into channels of carbonized wood by capillary action. The channels function as a high-surface-area, conductive, mechanically stable skeleton, which lowers the effective current density, ensures a uniform Na nucleation, and restricts the volume change over cycles. As a result, the Na-wood composite anode exhibited flat plating/stripping profiles with smaller overpotentials and stable cycling performance over 500 h at 1.0 mA/cm² in a common carbonate electrolyte system. In sharp comparison, the planar Na metal electrode showed a much shorter cycle life of 100 h under the same test conditions.

Direct Growth of MoS2 Microspheres on Ni Foam as a Hybrid Nanocomposite Efficient for Oxygen Evolution Reaction

MoS2 microspheres are directly grown on the conductive Ni foam and the as-obtained MoS2 -Ni electrodes exhibit highly efficient electrocatalytic performances for oxygen evolution in 1.0 m NaOH, displaying a rather low overpotential of 0.310 V at 20.0 mA cm(-2) , a high current density, good cyclic stability, and excellent flexibility.

Incorporation of Nitrogen Defects for Efficient Reduction of CO2 via Two-Electron Pathway on Three-Dimensional Graphene Foam

The practical recycling of carbon dioxide (CO2) by the electrochemical reduction route requires an active, stable, and affordable catalyst system. Although noble metals such as gold and silver have been demonstrated to reduce CO2 into carbon monoxide (CO) efficiently, they suffer from poor durability and scarcity. Here we report three-dimensional (3D) graphene foam incorporated with nitrogen defects as a metal-free catalyst for CO2 reduction. The nitrogen-doped 3D graphene foam requires negligible onset overpotential (-0.19 V) for CO formation, and it exhibits superior activity over Au and Ag, achieving similar maximum Faradaic efficiency for CO production (∼85%) at a lower overpotential (-0.47 V) and better stability for at least 5 h. The dependence of catalytic activity on N-defect structures is unraveled by systematic experimental investigations. Indeed, the density functional theory calculations confirm pyridinic N as the most active site for CO2 reduction, consistent with experimental results.

Achieving Highly Efficient, Selective, and Stable CO2 Reduction on Nitrogen-Doped Carbon Nanotubes

The challenge in the electrosynthesis of fuels from CO2 is to achieve durable and active performance with cost-effective catalysts. Here, we report that carbon nanotubes (CNTs), doped with nitrogen to form resident electron-rich defects, can act as highly efficient and, more importantly, stable catalysts for the conversion of CO2 to CO. The unprecedented overpotential (-0.18 V) and selectivity (80%) observed on nitrogen-doped CNTs (NCNTs) are attributed to their unique features to facilitate the reaction, including (i) high electrical conductivity, (ii) preferable catalytic sites (pyridinic N defects), and (iii) low free energy for CO2 activation and high barrier for hydrogen evolution. Indeed, DFT calculations show a low free energy barrier for the potential-limiting step to form key intermediate COOH as well as strong binding energy of adsorbed COOH and weak binding energy for the adsorbed CO. The highest selective site toward CO production is pyridinic N, and the NCNT-based electrodes exhibit no degradation over 10 h of continuous operation, suggesting the structural stability of the electrode.