Classical, phenomenological analysis of the kinetics of reactions at the gas-exposed surface of mixed ionic electronic conductors

The kinetics of reactions occurring at the gas-exposed surfaces of charged mixed ionic electronic conductors (MIECs) are examined from theoretical first principles. Analysis based on the classical electrochemical potential-transition state theory model reveals that the nature of the reactions is electrochemical in general. However, the influence of the surface potential on the reaction rate is opposite for adsorption and incorporation reactions. Two-dimensional finite volume models of an MIEC as working electrode in a half-cell configuration are presented. The results for a simple, two-step reduction process show that the effect of the surface potential on the rate of reactions is minimal for incorporation-limited reactions but more influential for adsorption-limited reactions. An erratum to this article is available at .     

Effects of Cathode and Anode on Deposition of Trimethylsilane in Glow Discharge

DC cathodic polymerization of trimethylsilane (TMS) was carried out in plasma reactors with and without using anode assembly. In DC cathodic polymerization, the TMS plasma polymers are mainly deposited on the cathode (substrate) surface. As a result, fast deposition of TMS plasma polymers was easily achieved in DC cathodic polymerization as compared with AF or RF plasma polymerization. DC cathodic polymerization without using anode assembly has its advantageous features that the size and number of substrates (as cathodes) are not restricted by the size and the location of anode assembly. It was found that the maximum deposition rate on the cathode surfaces was obtained without anode assembly. The DC cathodic polymerization of TMS was conducted also in a large volume reactor with multiple cathodes (substrates). The same deposition mechanisms for DC cathodic polymerization with a single cathode also apply to the multiple cathodes. Uniform deposition on each cathode could be obtained with appropriate spacing of multiple cathodes and by adjusting the operational parameters, which are based on the current density and the system pressure.     

固体氧化物电解池直接电解CO2的研究进展

固体氧化物电解池是一种高效、环境友好型的能量转换器件,可以直接将电能转化为化学能. 本文介绍了近年来作者课题组在固体氧化物电解池直接用于CO₂还原的研究进展,并以阴极材料为主着重讨论了金属陶瓷电极和混合导电型钙钛矿氧化物电极的研究工作,最后展望了未来固体氧化物电解池直接电解CO₂的研究思路和方向.     

Erosion of Thin Foils by Sputtering in Hollow Cathodes

A thin copper foil placed diagonally in a cylindrical copper hollow cathode undergoes fast erosion caused by cathode sputtering. Changes in the foil shape are related to current distribution along the hollow cathode axis. The experimental results aid in understanding the increase in spectral lines intensities emitted from conical bottom hollow cathode lamps.     

Cathodes for Aqueous Zn-Ion Batteries: Materials,Mechanisms, and Kinetics

As concerns about the safety of lithium-ions batteries (LIBs) increases, aqueous zinc-ion batteries (ZIBs) with a lower cost, higher safety, and higher co-efficiency have attracted more and more interest. However, finding suitable cathode materials is still an urgent problem in ZIBs. In recent years, a lot of significant works have been reported, including manganese-based cathodes, vanadium-based cathodes, Prussian blue analog-based materials, and sustainable quinone cathodes. In this review, some typical cathode materials are introduced. The detailed storage mechanisms and methods for improving the reaction kinetics of the zinc ions are summarized. Finally, the issues, challenges, and the research directions are provided.     

Fervent Hype behind Magnesium Batteries: An Open Call to Synthetic Chemists—Electrolytes and Cathodes Needed

Magnesium metal is a superior anode which has double the volumetric capacity of lithium metal and has a negative reduction potential of −2.37 V vs. the standard hydrogen electrode. A major benefit of magnesium is the apparent lack of dendrite formation during charging which is one of the crucial concerns of using a lithium metal anode. In this Review, we highlight the foremost research in the development of electrolytes and cathodes and discuss some of the significant challenges which must be overcome in realizing a practical magnesium battery.     

Revealing the Reaction and Fading Mechanism of FeSe2 Cathodes for Rechargeable Magnesium Batteries

Rechargeable Mg batteries (RMBs) are advantageous large-scale energy-storage devices because of the high abundance and high safety, but exploring high-performance cathodes remains the largest difficulty for their development. Compared with oxides and sulfides, selenides show better Mg-storage performance because the weaker interaction with the Mg²⁺ cation favors fast kinetics. Herein, nanorod-like FeSe₂ was synthesized and investigated as a cathode for RMBs. Compared with microspheres and microparticles, nanorods exhibit higher capacity and better rate capability with a smaller particle size. The FeSe₂ nanorods show a high capacity of 191 mAh g⁻¹ at 50 mA g⁻¹ and a good rate performance of 39 mAh g⁻¹ at 1000 mA g⁻¹. Ex situ characterizations demonstrate the Mg²⁺ intercalation mechanism for FeSe₂, and a slight conversion reaction occurs on the surface of the particles. The capacity fading is mainly because of the dissolution of Fe²⁺, which is caused by the reaction between Fe²⁺ and Cl⁻ of the electrolyte during the charge process on the surface of the particles. The surface of FeSe₂ is mainly selenium after long cycling, which may also dissolve in the electrolyte during cycling. The present work develops a new type of Mg²⁺ intercalation cathode for RMBs. More importantly, the fading mechanism revealed herein has considered the specificity of Mg battery electrolyte and would assist a better understanding of selenide cathodes for RMBs.     

Ozone-based electrochemical advanced oxidation processes

Novel processes have recently been developed that provide for the enhancement of ozonation through combination with electrochemical treatments. These are processes that can be included among those defined as advanced oxidation processes as they proceed via electrogeneration of highly oxidizing radical species.These processes are generally carried out by sparging ozone in both divided and undivided electrochemical cells in order to promote its decomposition through different mechanisms, depending on the electrode materials adopted, and in some cases still debated.This mini review presents the most recent advances in the field of electrochemically assisted ozonation.In particular, the first section is focused on the process known as electroperoxone (EP) where the ozone decomposition is enhanced by the adoption of carbon-based cathodes, due to the electrogeneration of hydrogen peroxide, while the second section is focused on the process that implies ozonation in a cell adopting metal-based cathodes.     

Beyond the Polysulfide Shuttle and Lithium Dendrite Formation: Addressing the Sluggish Sulfur Redox Kinetics for Practical High-Energy Li-S Batteries

Electrolyte modulation simultaneously suppresses polysulfide the shuttle effect and lithium dendrite formation of lithium–sulfur (Li-S) batteries. However, the sluggish S redox kinetics, especially under high S loading and lean electrolyte operation, has been ignored, which dramatically limits the cycle life and energy density of practical Li-S pouch cells. Herein, we demonstrate that a rational combination of selenium doping, core–shell hollow host structure, and fluorinated ether electrolytes enables ultrastable Li stripping/plating and essentially no polysulfide shuttle as well as fast redox kinetics. Thus, high areal capacity (>4 mAh cm⁻²) with excellent cycle stability and Coulombic efficiency were both demonstrated in Li metal anode and thick S cathode (4.5 mg cm⁻²) with a low electrolyte/sulfur ratio (10 μL mg⁻¹). This research further demonstrates a durable Li-Se/S pouch cell with high specific capacity, validating the potential practical applications.     

锂硫电池硫正极催化转换反应的研究进展

单质硫作为电池的正极材料,其电化学过程历经多个步骤,完全放电生成最终产物是一个2电子反应. 低阶多硫化锂的生成需克服一定的能垒,且由Li₂S₂得到一个电子还原生成Li₂S的反应是速控步骤. 硫正极的反应动力学是决定锂硫电池电化学性能,如比能量、比功率、低温性能等的关键因素. 提高速控步骤的反应动力学还能加速可溶性多硫化锂Li₂S₄向不溶性Li₂S₂和Li₂S的转化,有利于减缓或消除多硫化锂的“穿梭效应”. 近年,已有大量的过渡金属氧化物、硫化物、碳化物、氮化物、磷化物,单原子催化剂和氧化还原电子中继体等被应用于催化硫正极反应,提高了电极的电化学性能和循环稳定性. 但是,目前详细的催化反应机制尚不完全清晰. 本文重点综述了这些化合物在硫正极反应中的作用机制,总结了近年来的研究进展,并对硫正极催化转换反应的研究和发展进行了展望.