Slow Kinetics Research Articles

Coupling multifunctional ZnCoAl-layered double hydroxides on Ti-Fe2O3 photoanode for efficient photoelectrochemical water oxidation

The efficiency of photoelectrochemical (PEC) water splitting is hindered by the slow kinetics of the oxygen evolution reaction (OER). This study developed a composite photoanode for water oxidation by incorporating ternary LDHs (ZnCoAl-LDH) onto Ti-Fe2O3 as a cocatalyst. The ZnCoAl-LDH/Ti–Fe2O3 photoanode achieved a photocurrent density of 3.51 mA/cm2 at 1.23 V vs. RHE, which is 9.8 times higher than that of bare Ti-Fe2O3. Through a series of characterizations, the synergistic effects among the three metals were revealed. Furthermore, the addition of Zn can induce the formation of more high-valent Co, increasing the conductivity of CoAl-LDH and significantly reducing the surface charge transfer resistance. These advantages significantly enhance the injection efficiency of ZnCoAl-LDH/Ti-Fe2O3 (82 %), thereby accelerating the OER kinetics of Ti-Fe2O3. Our work introduces new approaches for selecting photoelectrochemical cocatalysts and designing high-performance photoanodes for water splitting.

Silicon-air batteries enabled by in-situ FeMn alloy-catalyzed nitrogen-doped carbon nanotube arrays as efficient air electrodes catalysts

Silicon-air batteries (SABs) have become promising candidates for energy conversion and storage devices due to their high theoretical energy density, cost-effectiveness, and inherent safety. However, the slow kinetics of the 4e− transfer in the oxygen reduction reaction (ORR) at the cathode during discharge, coupled with severe polarization, reduces the battery’s capacity and hinders the development of silicon-air batteries. The cathodes of currently developed SABs primarily rely on commercial Pt/C and MnO2, with limited research on low-cost, efficient, and stable air cathodes for SABs. To address this issue, we synthesized nitrogen-doped carbon nanotubes containing FeMn alloy particles (FeMn@NCNTs) as cathode ORR catalysts using a simple high-temperature pyrolysis method combined with chemical vapor deposition. In an alkaline medium, the catalyst’s half-wave potential (E1/2) reached 0.83 V. Moreover, the FeMn@NCNTs air cathode exhibited excellent compatibility with the silicon anode, and the constructed aqueous silicon-air battery demonstrated a high specific capacity (165 Ah kg−1) and power density (3.69 mW cm−2). Additionally, the quasi-solid-state SABs constructed with FeMn@NCNTs showed stable operation over a wide temperature range, providing a new solution for the development of low-cost, efficient silicon-air batteries suitable for a wide range of applications.

FeNi3 alloy doped carbon spheres for improving hydrogen storage performance of MgH2

MgH2 is one of the ideal hydrogen storage materials because of its high hydrogen storage density, but the thermodynamic stability and slow kinetics of Mg/MgH2 system hinder its practical application. Transition metal catalyst doping has become an important strategy to improve the hydrogen storage kinetics of MgH2. In this work, FeNi3@CS was prepared by solvothermal method with carbon spheres (CS) as the support, and introduced into Mg/MgH2 system to prepare MgH2–FeNi3@CS composite. The initial dehydrogenation temperature of MgH2–FeNi3@CS composite is 565 K, which is 100 K lower than additive-free MgH2. At 423 K, MgH2–FeNi3@CS composite could absorb 4.5 wt% H2, while the hydrogen absorption capacity of MgH2 without additives is only 2.0 wt%. After 10 cycles, the hydrogenation and dehydrogenation capacity could be maintained at 5.6 wt% and 4.5 wt%, respectively. In addition, the activation energy of MgH2–FeNi3@CS composite decreased by 52 kJ/mol compared with MgH2. FeNi3 was in situ converted to Mg2NiH4 and Fe after hydrogenation-ball milling, which were considered as the catalytic active substances in Mg/MgH2 system. The synergistic catalysis of Mg2Ni/Mg2NiH4, Fe and carbon materials has a positive effect on improving the hydrogen storage performance of Mg/MgH2 system.

Efficient Electrocatalytic Oxidation of Glycerol to Formate Coupled with Nitrate Reduction over Cu-Doped NiCo Alloy Supported on Nickel Foam.

Electrooxidation of biomass-derived glycerol which is regarded as a main byproduct of industrial biodiesel production, is an innovative strategy to produce value-added chemicals, but currently showcases slow kinetics, limited Faraday efficiency, and unclear catalytic mechanism. Herein, we report high-efficiency electrooxidation of glycerol into formate via a Cu doped NiCo alloy catalyst supported on nickel foam (Cu-NiCo/NF) in a coupled system paired with nitrate reduction. The designed Cu-NiCo/NF delivers only 1.23 V vs. RHE at 10 mA cm-2, and a record Faraday efficiency of formate of 93.8 %. The superior performance is ascribed to the rapid generation of NiIII-OOH and CoIII-OOH species and favorable coupling of surface *O with reactive intermediates. Using Cu-NiCo/NF as a bifunctional catalyst, the coupled system synchronously produces NH3 and formate, showing 290 mV lower than the coupling of hydrogen evolution reaction, together with excellent long-term stability for up to 144 h. This work lays out new guidelines and reliable strategies from catalyst design to system coupling for biomass-derived electrochemical refinery.

Efficient Electrocatalytic Oxidation of Glycerol to Formate Coupled with Nitrate Reduction over Cu‐Doped NiCo Alloy Supported on Nickel Foam

AbstractElectrooxidation of biomass‐derived glycerol which is regarded as a main byproduct of industrial biodiesel production, is an innovative strategy to produce value‐added chemicals, but currently showcases slow kinetics, limited Faraday efficiency, and unclear catalytic mechanism. Herein, we report high‐efficiency electrooxidation of glycerol into formate via a Cu doped NiCo alloy catalyst supported on nickel foam (Cu−NiCo/NF) in a coupled system paired with nitrate reduction. The designed Cu−NiCo/NF delivers only 1.23 V vs. RHE at 10 mA cm−2, and a record Faraday efficiency of formate of 93.8 %. The superior performance is ascribed to the rapid generation of NiIII−OOH and CoIII−OOH species and favorable coupling of surface *O with reactive intermediates. Using Cu−NiCo/NF as a bifunctional catalyst, the coupled system synchronously produces NH3 and formate, showing 290 mV lower than the coupling of hydrogen evolution reaction, together with excellent long‐term stability for up to 144 h. This work lays out new guidelines and reliable strategies from catalyst design to system coupling for biomass‐derived electrochemical refinery.

Stable Long‐Term Cycling of Room‐Temperature Sodium‐Sulfur Batteries Based on Non‐Complex Sulfurised Polyacrylonitrile Cathodes

The cost‐effectiveness and high theoretical energy density make room‐temperature sodium‐sulfur batteries (RT Na–S batteries) an attractive technology for large‐scale applications. However, these batteries suffer from slow kinetics and polysulfide dissolution, resulting in poor electrochemical performance. Thus, the sulfurised polyacrylonitrile (SPAN) cathode is postulated as a suitable material due to the retention of sulfur through covalent bonds and the increase in the conductivity of sulfur. Furthermore, in this work the synthesis of SPAN has been carried out using simple synthesis methods, making it scalable, economical, and without the use of toxic compounds. The incorporation of the SPAN material helps mitigate the shuttle effect, reducing the capacity loss and improving both the efficiency and lifespan of Na–S batteries. The SPAN‐based cathode demonstrates that this RT Na–S battery configuration shows high stability, reaching 1000 cycles with a capacity loss per cycle of 0.11% and a satisfactory specific capacity of 400 mAh/gs at a high rate of 2C. This study demonstrates that the utilisation of SPAN derived from a non‐complex synthesis can be a viable alternative for enhancing the future of Na–S batteries technology.

Leveraging Soft Acid-Base Interactions Alters the Pathway for Electrochemical Nitrogen Oxidation to Nitrate with High Faradaic Efficiency.

Electrocatalytic nitrogen oxidation reaction (N2OR) offers a sustainable alternative to the conventional methods such as the Haber-Bosch and Ostwald oxidation processes for converting nitrogen (N2) into high-value-added nitrate (NO3 -) under mild conditions. However, the concurrent oxygen evolution reaction (OER) and inefficient N2 absorption/activation led to slow N2OR kinetics, resulting in low Faradaic efficiencies and NO3 - yield rates. This study explored oxygen-vacancy induced tin oxide (SnO2-Ov) as an efficient N2OR electrocatalyst, achieving an impressive Faradaic efficiency (FE) of 54.2% and a notable NO3 - yield rate (22.05µg h-1 mgcat -1) at 1.7V versus reversible hydrogen electrode (RHE) in 0.1m Na2SO4. Experimental results indicate that SnO2-Ov possesses substantially more oxygen vacancies than SnO2, correlating with enhanced N2OR performance. Computational findings suggest that the superior performance of SnO2-Ov at a relatively low overpotential is due to reduced thermodynamic barrier for the oxidation of *N2 to *N2OH during the rate-determining step, making this step energetically favorable than the oxygen adsorption step for OER. This work demonstrates the feasibility of ambient nitrate synthesis on the soft acidic Sn active site and introduces a new approach for rational catalyst design.

Thermal conversion engineering of vanadium nitride-oxide cathode for high-rate aqueous Zn-ion battery

Vanadium-based materials are promising cathodes for high electrochemical performance aqueous Zn-ion batteries (AZIBs) due to their high specific capacity and multielectron redox reactions. However, vanadium-based materials suffer from low intrinsic conductivities and slow reaction kinetics, leading to poor rate performance. Here, we introduce vanadium nitride-oxide (VOVN) composites fabricated through a thermal conversion strategy, which exhibit high capacity and superior rate performance. The interface regulation of V2O3 and VN composite promotes charge carrier transport and enhances cathode reaction kinetics. Additionally, the dual energy storage mechanism in VOVN composites facilitates highly reversible Zn2+ storage processes. Consequently, the VOVN cathode demonstrates high discharge capacity (445.3 mAh g−1 at 0.1 A g−1), excellent rate performance (151.4 mAh g−1 at 30 A g−1), and fast diffusion coefficient (10−9–10−10 cm2 s−1). This study provides a straightforward and effective approach to developing high-performance cathodes for AZIBs.

Capacitive deionization and electrochemical performance of a hierarchical porous electrodes enabled by nitrogen and phosphorus doped CNTs and removable NaCl template

Capacitive Deionization (CDI) is an electrochemical desalination technique based on the electrical double layer, which accumulate salts from the water stream; however, achieving higher salt adsorption for low-concentration salt is hindered due to several obstacles, such as low adsorption capacity and slow kinetics on the electrode surface. In this study, we reported a novel electrode fabrication method designed to enhance the hydrophilicity of the electrode material and activate hierarchical porosity, making a more accessible adsorption surface area. This modification enables more than 210 % improvement in salt adsorption capacity, achieving 17.5 mg g-1 in a single pass process with good stability in an 850 mg/L NaCl solution at 1.2 V, surpassing most reported carbon-based electrodes under similar operating conditions. Electrode formulation consists of Nitrogen (N) and Phosphorus (P) doped hierarchical carbon nanotubes (CNTs) network blended with additional NaCl as a green and removable template to reach higher levels of porosity. The electrochemical sorption behavior of the sample was characterized over a voltage range of –0.5 to 0.7 V. Furthermore, the electrode materials were characterized utilizing various characterization methods, including Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Raman Spectroscopy, Fourier Transformed Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) to explore the correlation between microstructure, morphology, and properties. Our finding reveals that not only N and P can affect adsorption, but also the novel cathode preparation method, which employs a removable NaCl templated hierarchical porous electrode, has a profound effect on the electrochemical and CDI results. This finding will open a new perspective in designing electrodes for all electrochemical systems.

Coupling (NixCo1-x)0.85Se with N-doped MoSe2 for hybrid supercapacitors with remarkable cyclic durability

Despite being a novel supercapacitive material, the widespread application of layered molybdenum diselenide has been hindered by its low specific capacity, significant volume changes during electrochemical reactions, and slow kinetics. In this study, we successfully combined (NixCo1-x)0.85Se nanoparticles with N-MoSe2 to create (NixCo1-x)0.85Se/N-MoSe2 hybrids (labeled as AxB1-xC). The electrochemical performance of AxB1-xC was dramatically improved due to the synergistic effects between nickel and cobalt, as well as between (NixCo1-x)0.85Se and N-MoSe2. Among the various AxB1-xC electrodes, the A0.8B0.2C electrode exhibited the best electrochemical performance when the Ni/Co ratio was 0.8/0.2. It provided a specific capacity of 397.9 C g−1 at 0.5 A/g and retained 220.0 C g−1 after 2,000 cycles at 10 A/g. Furthermore, we constructed an A0.8B0.2C//AC hybrid supercapacitor to assess its energy storage capability. The A0.8B0.2C//AC device achieved a specific capacitance of 72.6 F g−1 at 0.5 A/g with an energy density of 25.8 Wh kg−1 at 400 W kg−1. The capacitive retention of the A0.8B0.2C//AC device was 92.9 % after 40,000 cycles at 3 A/g. Impressively, a self-constructed A0.8B0.2C//AC device could power a timer for about 24 min, demonstrating its potential for practical applications.

Research progress on 5-hydroxymethylfurfural electrocatalytic or photocatalytic oxidation coupling with hydrogen production

Biomass and hydrogen serve as crucial alternatives to fossil fuels, addressing climate change and the shortage of fossil fuels. Hydrogen offers high energy density and emits no carbon, while biomass is abundant and renewable. Nevertheless, green hydrogen production via electrocatalysis or photocatalysis faces challenges such as slow kinetics and low efficiency. Oxidation catalysis of biomass derivatives, particularly 5-hydroxymethylfurfural (HMF), has the potential to substitute for the oxygen evolution reaction (OER) in hydrolysis, leading to a significant increase in hydrogen evolution and the production of valuable products such as 2,5-diformylfuran (DFF), 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), and 2,5-furan dicarboxylic acid (FDCA). This review explores recent advancements in electrocatalytic, photocatalytic, and photoelectrocatalytic HMF oxidation coupled with hydrogen production. This study provides a theoretical basis and practical guidance for catalyzing HMF oxidation coupled with hydrogen production through a detailed analysis of the reaction mechanism of HMF oxidation coupled with hydrogen generation and the performance of bifunctional catalysts.

A potential strategy for eco-friendly and efficient copper recovery: Ferricyanide-enhanced glycine leaching of copper

E-waste contains significant amounts of metal elements, particularly copper. Efficient and eco-friendly recovery of copper is essential for both the resourceful utilization of e-waste and the mitigation of environmental pollution. Glycine leaching is a green method for copper recovery, but the use of conventional oxidants suffers from slow reaction kinetics and low leaching yields. Herein, by introducing ferricyanide ([Fe(CN)6]3−) as an oxidant in the glycine leaching of copper, the efficient dissolution of copper was realized. Electrochemical measurements and various physical characterizations demonstrate that the [Fe(CN)6]3− oxidant effectively increases the initial potential of the solution by forming a [Fe(CN)6]3−/ [Fe(CN)6]4− redox couple. This promotes the rapid oxidation of Cu to Cu2+, facilitates the formation of soluble copper complexes with gly−, and prevents the development of an oxidized passivation layer on the copper surface, resulting in efficient copper dissolution. Compared to 0.15 M H2O2, the addition of 0.01 M [Fe(CN)6]3− increased the initial potential of the solution from 192.33 mV to 489.30 mV and raised the dissolved copper concentration from 225.60 ppm to 330.40 ppm after 24 h. The “potential enhancement” effect of ferricyanide in this work provides an effective strategy for efficient copper recovery.

Enhancing the dehydrogenation properties of LiAlH4 through the addition of ZrF4 for solid-state hydrogen storage

Hydrogen energy is emerging as an essential alternative to fossil fuels due to its clean energy profile, generating energy without greenhouse gas emissions. Solid-state hydrogen storage, particularly using complex hydrides like LiAlH4, holds promise due to high hydrogen capacities. However, practical applications of LiAlH4 face obstacles due to slow dehydrogenation kinetics and high decomposition temperatures. This study investigates the catalytic effect of ZrF4 on LiAlH4 to improve hydrogen storage properties. Incorporating 10wt.% ZrF4 has significantly lowered the onset desorption temperature from 160 °C to 80 °C. Desoption kinetic result showed that the addition of 10wt.% ZrF4 can enables the release of 5.6wt.% hydrogen in 120min at 100 °C, which is 50 times faster than in undoped samples. X-ray diffraction analysis indicated that ZrF4 facilitated the in-situ formation of Al3Zr and LiF phases during dehydrogenation, thereby enhancing catalytic efficiency. The desorption activation energies for first two reactions decreased significantly by ~ 16kJ/mol and ~24kJ/mol with ZrF4 doping. These findings suggest that ZrF4 effectively improves the hydrogen storage properties of LiAlH4, positioning it as a potential catalyst for solid-state hydrogen storage systems.

Delithiation-accelerating and self-healing strategies realizes high-capacity and high-rate black phosphorus anode in wide temperature range

Black phosphorus (BP) anode with high capacity (2596 mAh g−1) and suitable lithiation potential (0.7 V vs. Li+/Li) is an ideal candidate for high-energy-density and high-safety lithium-ion batteries, however, the pratical implementation is greatly limited by its slow reaction kinetics and huge volume expansion. Here, inspired by nature, liquid metal (LM) is explored as a self-heal agent, which can well stabilize the BP anode through buffering the volumetric expansion and re-activating “dead P and LixP”. Moreover, LM also acts as a good catalyst, which can adjust Li ion concentration and reduce the activation energy of delithiation reaction, thus prolonging the cycling life. Therefore, the LM modified BP/graphite (G) composite delivers an excellent high-rate performance of 1123 mAh g−1 at 4 C with 80.0% capacity retention after 200 cycles, a superior wide-temperature performance of 1547.5 mAh g−1 and 569.0 mAh g−1 at 50 oC and −20 oC, respectively.

Enhanced dynamics of Al3+/H+ ions in aqueous aluminum ion batteries: Construction of metastable structures in vanadium pentoxide upon oxygen vacancies

In recent years, aqueous aluminum ion batteries have been widely studied owing to their abundant energy storage and high theoretical capacity. An in-depth study of vanadium oxide materials is necessary to address the precipitation of insoluble products covered cathode surface and the slow reaction kinetics. Therefore, a method using a simple one-step hydrothermal preparation and oxalic acid to regulate oxygen vacancies has been reported. A high starting capacity (400 mAh g−1) can be achieved by Ov-V2O5, and it is capable of undergoing 200 cycles at 0.4 A g−1, with a termination discharge capacity of 103 mAh g−1. Mechanism analysis demonstrated that metastable structures (AlxV2O5 and HxV2O5) were constructed through the insertion of Al3+/H+ during discharging, which existed in the lattice intercalation with V2O5. The incorporation of oxygen vacancies lowers the reaction energy barrier while improving the ion transport efficiency. In addition, the metastable structure allows the electrostatic interaction between Al3+ and the main backbone to establish protection and optimize the transport channel. In parallel, this work exploits ex-situ characterization and DFT to obtain a profound insight into the instrumental effect of oxygen vacancies in the construction of metastable structures during in-situ electrochemical activation, with a view to better understanding the mechanism of the synergistic participation of Al3+ and H+ in the reaction. This work not only reports a method for cathode materials to modulate oxygen vacancies, but also lays the foundation for a deeper understanding of the metastable structure of vanadium oxides.

Development and Characterization of Mesoporous Silica-MgSO4-MgCl2 Binary Salt Composites for Low-Grade Heat Storage in Fluidized Bed Systems

Achieving nearly zero-energy buildings requires efficient utilization and storage of renewable energy. Salt-hydrate-based thermochemical energy storage (TCES) systems are promising due to their high heat storage capacity and minimal seasonal heat loss. However, challenges remain for their commercialization and large-scale application. For example, TCES systems using magnesium sulfate (MgSO4) provide low temperature lifts due to slow reaction kinetics. Incorporating deliquescent salts like magnesium chloride (MgCl2) can enhance sorption performance but may introduce stability issues such as agglomeration and decomposition. This study proposes a novel binary-salt composite that combines MgSO4 and MgCl2 within commercial mesoporous silica (CMS) to address these challenges and enhance overall performance. The binary-salt composite powder, with a particle size range of 150 to 300 μm, is suitable for use in fluidized-bed reactors, where fast mass and heat transfer promote efficient moisture adsorption, prevent uneven temperature distribution, and reduce agglomeration. Measured using thermogravimetric analysis (TGA), the MgCl2-MgSO4@CMS binary-salt composites, with a total salt content of 50 wt% and salt mixing ratios of 3:1, 1:1, and 1:3, exhibited water sorption capacities of 0.95, 0.68, and 0.57 g/g, respectively. In comparison, the MgSO4@CMS single-salt composite showed a lower water adsorption capacity of 0.47 g/g and required higher temperatures above 150 °C for complete regeneration. Reactor-scale experiments demonstrated that the MgCl2-MgSO4(1:1)@CMS composite can be fluidized at low gas velocities on the order of 10-2 m/s, providing a maximum temperature lift of 24.7 °C and an energy density of 1018 kJ/kg during hydration at 80% relative humidity and 30 °C. The binary-salt composite also showed good cyclic stability with less particle agglomeration compared to the MgCl2@CMS single-salt composite.

Efficient and durable OER electrocatalysts through vacancy engineering and core-shell structure design in acidic environment

The electrocatalytic conversion of water into green hydrogen energy through overall water splitting advances sustainable energy goals. However, it is limited by the slow kinetics of the oxygen evolution reaction (OER) and durability challenges at high potentials. Here, we rationally develop a series of Mn-doped RuO2-coated Ru (Mn-Ru@RuO2) catalysts involving unique core-shell structures and abundant lattice distortions induced by oxygen defects. The optimal Mn-Ru@RuO2 sample demonstrated robust activity, achieving a low overpotential of 220 mV at 10 mA cm−2. Notably, this sample exhibited minimal degradation after 220 h and a 25.5-fold increase in mass activity (1.37 A mgRu−1) compared to commercial RuO2 at an overpotential of 300 mV. These results suggest that regulated oxygen deficiencies and optimal Ru3+/Ru4+ ratios facilitate the lattice oxygen oxidation (LOM) mechanism and the formation of a high concentration of ∗OH radicals, enhancing acidic OER performance. Additionally, the unique core-shell structures effectively prevent over-oxidation of the RuO2 shell, ensuring superior durability. This research not only breaks the trade-off of electrochemical activity and durability, but also provides valuable insights into the design of highly efficient and stable electrocatalysts.

A dynamical calo-porosimeter to characterize wetting and drying processes in lyophobic nanometric pores.

Lyophobic heterogeneous systems, based on porous fluids made of ordered nanoporous particles immersed in a non-wetting liquid, constitute systems of interest for exploring wetting, drying, and coupled transport phenomena in nanometric confinement. To date, most experimental studies on the forced filling and spontaneous emptying of lyophobic nanometric pores, at pressures of several tens of MPa, have been conducted in a quasi-static regime. However, some studies have shown that dynamical measurements are essential to shed light on the rich physics of these phenomena. We describe here a dynamical calo-porosimeter that allows for the simultaneous mechanical and calorimetric characterization of filling and emptying cycles over four decades of timescales, ranging from a few milliseconds to 10 seconds. This thermally regulated instrument can be operated between -5 and 70°C. It also enables the study of a given porous material successively with different liquids by switching from one to another. The characterization of wetting dynamics, the study of slow kinetics due to changes in solute concentration, and the rapid measurement of the heat of wetting, among other thermal properties, are presented as examples of the possible applications of this apparatus.

Tip-like copper sites on high curvature supports for non-covalent to covalent interaction tuning in CO2 photoreduction

Single-atom engineering offers a promising method to transform CO2 into high-value chemicals. The local coordination structure design of the metal-support is crucial for overcoming slow reaction kinetics. In this study, Cu single atoms are immobilized on curved Bi12O17Br2 surface to create a tip-like metal site structure named Cutip-Bi12O17Br2. Due to the high curvature Bi12O17Br2 surface with tensile strain, the tip Cu creates significant electronegativity differences between adjacent Bi atomic sites, creating the vigorous polarization centers. The strong charge redistribution character of tip asymmetric Cu-Bi site favor the polarization of CO bond in nonpolar CO2 and adjust the noncovalent to covalent interaction of reaction intermediates. Benefiting from these features, the optimized Cutip-Bi12O17Br2 enhance the CO production rate by a factor of 34 relative to bulk-Bi12O17Br2, reaching a rate of 96.99 μmol g−1 h−1. This work provides a comprehensive understanding of the structural regulation of single-atom on high curvature surface for CO2 photoreduction.

Cu2+ intercalation bolstering the rate capability of δ-MnO2 cathode for aqueous zinc-ion battery

Cost-effective manganese dioxide (MnO2) promises the economical advantage of rechargeable aqueous zinc-ion batteries (ZIBs) but suffers its low electrical conductivity, the irreversibility of structural transformations during electrochemical reactions, and the slow kinetics of the reactions. This study employs a one-step co-precipitation technique to synthesize Cu2+ intercalated δ-MnO2 nanoflower. The intercalation of Cu2+ not only enlarges the interlayer spacing through the interaction with water molecules, but also strengthens the interlayer structure with Cu2+ as the pillars, improves the ionic conductivity, and enhances the rate capability of δ-MnO2. It is attributed to the co-insertion/extraction mechanism of Zn2+/H+. Therefore, the Cu2+ intercalation δ-MnO2 developed for ZIBs demonstrates a high specific capacity (300 mAh g−1 at 0.1 A g−1), long cycling stability (179 mAh g−1 until 2000 cycles at 1 A g−1 89.9 % capacity retention), and superior rate capability (195 mAh g−1 at 1 A g−1). Meanwhile, the flexible ZIBs assembled with this cathode material have wider commercial applicability.