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 Li2CO3 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

Heterojunction-composited architecture for Li–O2 batteries with low overpotential and long-term cyclability.

The crucial issue among lithium−oxygen batteries (LOBs) lies in the development of highly efficient catalysts to improve their large discharge−charge polarization, poor rate capability, and short cycle life. Herein, a composite of three-dimensional honeycomb graphene-supported a Mo/Mo2C heterojunction has been synthesized and can be utilized as a self-supported LOB cathode directly. The LOBs based on the Mo/Mo2C heterojunction composite cathode show a low overpotential of 0.52 V, a high discharge capacity of about 12016 mAh g−1 at 100 mA g−1, and a long-term cyclability (about 360 cycles) under a restricted capacity of 1000 mAh g−1 at 100 mA g−1, which exceeds the features of the majority of Mo-based catalysts for LOBs reported so far. Based on both experimental tests and density functional calculations, it is confirmed that the outstanding electrochemical performance is closely associated with a hierarchical porous structure for convenient oxygen/electrolyte diffusion, a large number of activity sites (interfaces/defects) for high capacity, and a high conductivity with metallic bonds for good rate capability. The method can be extended to prepare other metal based heterojunctions

In-situ atomic-scale phase transformation of Mg under hydrogen conditions.

Magnesium hydrogenation issue poses a serious obstacle to designing strong and reliable structural materials, as well as offering a safe alternative for hydrogen applications. Understanding phase transformation of magnesium under hydrogen gas plays an essential role in developing high performance structural materials and hydrogen storage materials. Herein, we report in-situ atomic-scale observations of phase transformation of Mg and Mg-1wt.%Pd alloy under hydrogen conditions in an aberration-corrected environmental transmission electron microscopy. Compare with magnesium hydrogenation reaction, magnesium oxidation reaction predominately occurs at room temperature even under pure hydrogen gas (99.9%). In comparison, magnesium hydrogenation is readily detected in the interface between Mg and Mg6Pd, due to catalytic role of Mg6Pd. Note that the nanoscale MgH2 compound transfers into MgO spontaneously, and the interface strain remarkably varies during phase transformation. These atomic-level observations and calculations provide fundamental knowledge to elucidate the issue of magnesium hydrogenation

Self-reductive synthesis of MXene/Na0.55Mn1.4Ti0.6O4 hybrids for high-performance symmetric lithium ion batteries.

Increasing environmental problems and energy challenges have created an urgent demand for the development of green and efficient energy-storage systems. The search for new materials that could improve the performance of Li-ion batteries (LIBs) is one of today's most challenging tasks. Herein, a stable symmetric LIB based on the bipolar material-MXene/Na0.55Mn1.4Ti0.6O4 was developed. This bipolar hybrid material showed a typical MXene-type layered structure with high conductivity, containing two electrochemically active redox couples, namely, Mn4+/Mn3+ (3.06 V) and Mn2+/Mn (0.25 V). This MXene/Na0.55Mn2O4-based symmetric full cell exhibited the highest energy density of 393.4 W h kg−1 among all symmetric full cells reported so far, wherein it is bestowed with a high average voltage of 2.81 V and a reversible capacity of 140 mA h g−1 at a current density of 100 mA g−1. In addition, it offers a capacity retention of 79.4% after 200 cycles at a current density of 500 mA g−1. This symmetric lithium ion full battery will stimulate further research on new LIBs using the same active materials with improved safety, lower costs and a long life-span

Porous Polymer Materials for CO₂ Capture and Electrocatalytic Reduction

Efficient capture of CO2 and its conversion into other high value-added compounds by electrochemical methods is an effective way to reduce excess CO2 in the atmosphere. Porous polymeric materials hold great promise for selective adsorption and electrocatalytic reduction of CO2 due to their high specific surface area, tunable porosity, structural diversity, and chemical stability. Here, we review recent research advances in this field, including design of porous organic polymers (POPs), porous coordination polymers (PCPs), covalent organic frameworks (COFs), and functional nitrogen-containing polymers for capture and electrocatalytic reduction of CO2. In addition, key issues and prospects for the optimal design of porous polymers for future development are elucidated. This review is expected to shed new light on the development of advanced porous polymer electrocatalysts for efficient CO2 reduction

An arginine-functionalized stationary phase for hydrophilic interaction liquid chromatography

An arginine-functionalized stationary phase for hydrophilic interaction liquid chromatography (HILIC) has been prepared for the first time by clicking arginine onto silica gel. It offers an efficient separation of organic acids, nucleotides and sugars. More interestingly, it exhibited excellent selectivity and enrichment toward acidic glycopeptides, even at a ratio of 1 : 150 to non-glycopeptides

Freestanding MXene–MnO2 films for Li–CO2 cathodes with low overpotential and long-term cycling.

The Li−CO2 battery is a potential energy storage device that not only possesses a theoretical energy density as high as 1876 W h kg−1 but also alleviates the consumption of fossil resources by converting the greenhouse gas CO2 into electric energy. However, some technique bottlenecks, such as high overpotential, low recyclability, and low energy density, severely prohibit its application rhythm. Here, we prepare a binder-free MXene−MnO2 composite film using vacuum-assisted filtration and in situ reduction, which can be used as a freestanding cathode for Li−CO2 batteries. This MXene−MnO2 film electrode bestows good cycle stability (∼220 cycles), high specific capacity, and lower overpotential (∼0.89 V) in Li−CO2 batteries. Both experimental tests and first-principles calculations reveal that the enhanced electrochemical properties are associated with three aspects. First, the MXene−MnO2 film offers a high electrical conductivity and porous structure, which provide fast transport channels for electrons and ions. Then, the replacement of Mn by Ti increases the adsorption of Li ions, which facilitates the rapid decomposition of Li2CO3. Finally, the synergistic effect of MXene and MnO2 exposes a large number of active sites, which increases the capacity of Li−CO2 batteries. Therefore, this self-supporting strategy on the MXene composite paves a way to develop high-performance Li−CO2 batteries

Determination of Polyamines in Serum by High-Performance Capillary Zone Electrophoresis with Indirect Ultraviolet Detection

A method for determining polyamines in serum by capillary zone electrophoresis (CZE) with indirect ultraviolet detection was established. The concentrations of polyamines in the sera of six healthy adults were determined and the results were in accordance with those obtained previously by high-performance liquid chromatography (HPLC). However, the CZE method is superior to HPLC in that it has high sensitivity, small sample consumption and easy sample pretreatment

Engineering current collectors for advanced alkali metal anodes: A review and perspective

Abstract Alkali metal batteries (AMBs) are promising next‐generation high‐density electrochemical energy storage systems. In addition, current collectors play important roles in enhancing their electrochemical performances. Thus, it is essential to have a critical review of the most recent advances in engineering the current collectors for high‐performance AMBs. In this review paper, the fundamentals of alkali metal deposition on current collectors will be introduced first. Then recent advances in the development of advanced metal and carbon‐based current collectors are examined for boosting the stability and cycle life of lithium metal batteries (LMBs) in terms of various strategies including 3D architectural design and functional modifications. Thereafter, the research progress in design of advanced current collectors will be analyzed for sodium/potassium metal batteries, especially the counterparts that do not follow the paradigms established in LMBs. Finally, the major challenges and key perspectives will be discussed for the future development of current collectors in AMBs

Engineering triple-phase interfaces around the anode toward practical alkali metal-air batteries.

Alkali metal-air batteries (AMABs) promise ultrahigh gravimetric energy densities, while the inherent poor cycle stability hinders their practical application. To address this challenge, most previous efforts are devoted to advancing the air cathodes with high electrocatalytic activity. Recent studies have underlined the solid-liquid-gas triple-phase interface around the anode can play far more significant roles than previously acknowledged by the scientific community. Besides the bottlenecks of uncontrollable dendrite growth and gas evolution in conventional alkali metal batteries, the corrosive gases, intermediate oxygen species, and redox mediators in AMABs cause more severe anode corrosion and structural collapse, posing greater challenges to the stabilization of the anode triple-phase interface. This work aims to provide a timely perspective on the anode interface engineering for durable AMABs. Taking the Li-air battery as a typical example, this critical review shows the latest developed anode stabilization strategies, including formulating electrolytes to build protective interphases, fabricating advanced anodes to improve their anti-corrosion capability, and designing functional separator to shield the corrosive species. Finally, the remaining scientific and technical issues from the prospects of anode interface engineering are highlighted, particularly materials system engineering, for the practical use of AMABs