Free energy relationships in electrochemistry: a history that started in 1935

This article is a historical overview of free energy relationships in electrochemistry with the purpose of giving the reader an integrated view on how these correlations are interconnected in various aspects starting with free energy correlations for outer-sphere and inner-sphere processes, Tafel correlations, the Butler?CVolmer equation, and electron transfer theories. The citation of the literature is far from complete and is aimed to stimulate the reader to further reading.     

锂离子电池多孔电极理论的回顾与新思考

本文总结了Newman多孔电极理论的基本内容,提出若干改进思路. 提出基于离子-空穴耦合传输机制描述浓电解质中的离子输运过程,在此基础上引入离子-电子耦合转移反应的思想处理电极材料中的离子传输问题,并通过计算嵌锂材料的离子扩散系数验证其合理性. 总结了描述多孔电极多尺度结构的相关理论和技术,表明均质化方法和基于结构重建的介观模拟方法均能给出比较合理的有效输运参数,从而提高多孔电极理论模拟结果的准确性.     

电极金属和电解质溶液界面势垒研究

本文根据肖特基效应和弗兰克-康东原理得到了近似理想极化电极体系赫姆荷尔茨双电层内势垒高度和宽度与电极电荷密度间的关系式。并用Hg-HCl电极电荷密度的文献值作了具体计算。计算表明,电极电势对电子转移势垒形状的影响是很大的。     

Molecular electronics at electrode–electrolyte interfaces

Four contemporary examples, all published in recent years, of studies of molecular electronics at electrode–electrolyte interfaces are reviewed in this opinion article. The first illustrative example involves the switching of the redox active molecular wire between redox states, with concomitant changes in molecular conductance. This example illustrates how molecular electronics at electrode–electrolyte interfaces can be used to analyse mechanisms of electron transfer, to distinguish electrolyte effects and to provide details not readily available from ensemble measurements. The second example shows that the fluctuations of molecular conductance of a redox active molecular wire can be followed as a function of electrode potential. This shows how the stochastic kinetics of individual reaction events at electrode–electrolyte interfaces can be followed. The third example demonstrates how electrochemistry can be used to control quantum interference in single molecular wires. The fourth example shows a single-molecule electrochemical transistor concept for well-defined metal cluster containing molecular wires.     

Electrochemistry at High Pressures: A Review

High pressure electrochemical studies are potentially dangerous and less immediately implemented than conventional investigations. Technical obstacles related to properties of the working electrode material, preparation of its surface, availability of suitable reference electrodes, and the need for specially designed high pressure equipment and cells may account for the relative lack of experimental data on electrochemistry at high pressures. However, despite the stringent requirements for system and equipment stability, significant developments have been made in recent years and the combination of electrochemical methods with high hydrostatic pressure has provided useful insights into the thermodynamics, kinetics, and other physico‐chemical characteristics of a wide range of redox reactions. In addition to fundamental information, high pressure electrochemistry has also lead to a better understanding of a variety of processes under non‐classical conditions with potential applications in today's industrial environment from extraction and electrosynthesis in supercritical fluids to measurement of the pH at the bottom of the ocean. The purpose of this article is to detail the experimental pressurizing apparatus for electroanalytical measurements at high pressures and to review the relevant literature on the effect of pressure on electrode processes and on the properties of aqueous electrolyte solutions.     

Challenges and recent progress in unraveling the intrinsic pH effect in electrocatalysis

The kinetics of many electrode reactions, especially those involving the consumption/production of H⁺/OH^?, show significant pH dependence. Systematic studies of the pH effect over a wide pH range can provide very useful information about their reaction mechanism(s) and help figure out the optimum reaction conditions. For fast electrode reactions in solutions of medium pH and low buffer capacity, correcting the effects induced from the shift of local pH near the electrode?electrolyte interface (pH^s) is a prerequisite for unraveling the intrinsic kinetics and its pH dependence. In this review, recent progress on how to estimate the pH^s, how to eliminate the effect induced by pH^s shift and how to deduce the pH dependent intrinsic reaction kinetics are summarized. Mechanistic and kinetic implication of pH effect on electrocatalytic processes will be discussed by taking formic acid/formate oxidation at Pt electrode as an example.     

三相电极法研究液/液界面离子转移的进展

三相电极法作为研究液/液界面离子转移的一种新方法,具有简单、快速、经济的特点。文章回顾了液/液界面离子转移的发展历史,介绍了三相电极法的实验原理,并对其在电化学中的研究进展和应用进行了评述,引用文献48篇。     

A Chemical Reaction to the Historiography of Biology

This article examines the often-overlooked role of chemical ideas and practices in the history of modern biology. The first section analyses how the conventional histories of the life sciences have, through the twentieth century, come to focus nearly exclusively on evolutionary theory and genetics, and why this storyline is inadequate. The second section elaborates on what the restricted neo-Darwinian history of biology misses, noting a variety of episodes in the history of biology that relied on developments in – or tools from – chemistry, including an example from the author’s own work. The diverse ways in which biologists have used chemical approaches often relate to the concrete, infrastructural side of research; a more inclusive history thus also connects to a historiography of materials and objects in science.     

The Pre‐exponential Factor in Electrochemistry

Like many branches of science, not to mention culture in general, electrochemistry has a number of recurring topics: Areas of research that are popular for a certain time, then fade away as their possibilities seem to have been exhausted, only to return decades later as progress in experimental or theoretical techniques offer new possibilities for their investigation. A prime example are fuel cells, which have undergone five such cycles, but here we discuss a general concept of kinetics—the pre‐exponential factor of a rate constant—which has undergone two such cycles. The first cycle was in the 1950–1980s, when the methods of electrochemical kinetics were developed, and the interpretation was based on transition‐state theory. The second was triggered by the re‐discovery of Kramers theory for reactions in condensed phases. This Minireview will show that the time has come for a third cycle based on recent progress in electrocatalysis.     

《界面电化学》专辑序言

界面电化学是以研究电极-电解液界面的结构和性质以及各种电极过程为特点的电化学科学的重要方向. 随着能源科学的迅猛发展,围绕各种复杂电化学界面、探讨其在能源电化学过程中的特殊作用显得十分重要,而发展和运用各种原位和非原位表征方法研究复杂界面的结构和性能关系也日益受到关注. 本专辑收录论文9篇,包括7篇研究论文和2篇综述,侧重于锂基电池、电催化和离子液体电化学体系中的界面问题,反映我国学者在电化学界面基础和应用研究方面所取得的最新进展,并评述有关能源电化学界面所存在的问题、挑战和解决策略.希望籍此促进我国电化学研究的进一步发展. 在此,谨对所有为本专辑撰稿的作者所给予的大力支持和贡献表示诚挚谢意！ 同时对审稿人及编辑部工作人员为本专缉的出版所付出的辛勤劳动表示衷心感谢！     

探测束偏转光谱电化学

评述了探测束偏转光与电化学手段相结合作为一种现场的光谱化学技术关研究电极／电解质界面上的应用。分别从实验装置、偏转原理、影响因素及其应用等方面加以论 。共引用文献５６篇。     

Problems in interfacial electrochemistry that have been swept under the carpet

A critical view of interfacial electrochemistry in the past 50?years is discussed, with emphasis on tacit assumptions, which are sometimes hard to justify. The important role of the Tafel equation in studies of the mechanism of electrode reactions and in the development of electrode kinetics in the past century is recognized. However, it is shown that the validity of the ways it was implemented can be questioned, particularly in view of the uncertainty in the value of the symmetry factor commonly assumed. For example, the value of β pertinent to a species in the outer-Helmholtz plane cannot be the same as that applicable to a species already adsorbed on the surface. Three factors are involved in considering charge transfer to an adsorbed species: (a) The electrostatic field at the adsorption site is highly distorted; thus, the overpotential imposed may not apply at the point where the reaction takes place; (b) the effective charge on the adsorbed species may not equal the nominal charge assigned to it; and (c) the metal surface may already be modified by a monolayer of adsorbed species of the same kind, which is, however, inactive with respect to the reaction taking place. Similarly, in studies of the kinetics of metal deposition and dissolution, where charge is transferred across the interface by the ions, one cannot legitimately assume a value of β, although it can be measured experimentally. It is very risky to predict the future of interfacial electrochemistry, but one might extrapolate present trends. Thus, the importance of the fundamental aspects of the field may have declined in the past two or three decades, and this trend will probably continue. On the other hand, the importance of understanding interfacial electrochemistry as a basis for related fields such as nano-science, biology, micro- and nano-implanted biosensors, interaction of tissue with metal implants, materials science, as well as technologies such as corrosion and alloy plating is likely to increase.     

Vibrational Stark shift spectroscopy of catalysts under the influence of electric fields at electrode–solution interfaces

External control of chemical processes is a subject of widespread interest in chemical research, including control of electrocatalytic processes with significant promise in energy research. The electrochemical double-layer is the nanoscale region next to the electrode/electrolyte interface where chemical reactions typically occur. Understanding the effects of electric fields within the electrochemical double layer requires a combination of synthesis, electrochemistry, spectroscopy, and theory. In particular, vibrational sum frequency generation (VSFG) spectroscopy is a powerful technique to probe the response of molecular catalysts at the electrode interface under bias. Fundamental understanding can be obtained via synthetic tuning of the adsorbed molecular catalysts on the electrode surface and by combining experimental VSFG data with theoretical modelling of the Stark shift response. The resulting insights at the molecular level are particularly valuable for the development of new methodologies to control and characterize catalysts confined to electrode surfaces. This Perspective article is focused on how systematic modifications of molecules anchored to surfaces report information concerning the geometric, energetic, and electronic parameters of catalysts under bias attached to electrode surfaces.

Heterogeneous electrocatalysis: characterization of interfacial electric field within the electrochemical double layer.     

State of ions near a cathode: Adions or adatoms?

It is the intent of this article to illustrate certain aspects of the present status of electrochemistry as regards theoretical interpretations. First a brief critical review of classical electrochemical kinetics is given and the directions are indicated in which improvement in theoretical treatments are hardly needed. Next, experimental results on the cathodic discharge of tin in darkness and in light are presented, and a tentative explanation based on the assumption that adatoms (and not adions) diffuse on the electrode surface as a result of stabilization by light is presented.     

Electrochemical potentials from first principles

The electrochemical potential is the fundamental parameter in the theory of electrochemistry. Not only does it determine the position of electrochemical equilibria but also it acts as the driving force for electron transfer reactions, diffusion-migration phenomena, and phase transformations of all kinds. In the present work, the electrochemical potential is defined as the total work done in transferring a single particle of a substance from a universal reference state to a specified location, at constant temperature and pressure. It is the sum of two scalar fields: the electrostatic potential energy and the chemical potential energy. The electrochemical potential is widely underutilized within the fields of solid-state science and electrochemical engineering. For historical reasons, many authors prefer to analyze driving forces in terms of electrode potentials, concentration gradients, or Gibbs free energies. In this paper, the author provides a short introduction to the electrochemical potential and then shows how some of the major branches of electrochemistry can benefit from using it. Topics examined include the Volta potential difference, the membrane potential difference, the scanning Kelvin probe microscope, the electromotive force, the proton motive force, and the activation of electron transfer.

     

固液界面双电层的理论计算模拟

固液界面双电层在电化学中处于核心地位. 如何发展一个理论方法,在该方法的框架下计算双电层的平衡性质和动力学性质一直以来都是理论研究的难点和热点. 本文总结了最近十几年第一性原理计算方法在计算双电层平衡性质和电催化反应的进展,如热力学方法、反应中心模型以及双参考方法. 并进一步详细地阐述了基于周期性均匀介质溶剂化模型 ( DFT/CM-MPB)对于固液界面双电层的研究,该方法能够计算双电层的平衡性质(零电荷电势和微分电容)和表面相图,在此基础上能深入研究基元反应的电荷转移系数,并结合微观动力学推导出宏观的Tafel(电流-电势)曲线. 并列举了该方法对于重要电化学反应(如氢电极反应)的应用实例.     

Plasmonic Imaging of the Interfacial Potential Distribution on Bipolar Electrodes

Bipolar electrochemistry is based on the gradient distribution of free‐electron density along an electrically isolated electrode, which causes a positive electrode potential at one end and a negative potential at the other, allowing for wide applications in analytical chemistry and materials science. To take full advantage of its wireless and high‐throughput features, various types of optical probes, such as pH indicators and fluorescence and electrochemiluminescence reagents, have often been used to indirectly monitor the interfacial electron transfer through chromogenic or fluorogenic reactions. Herein, we report the first probe‐free imaging approach that can directly visualize the distribution of the interfacial potential in bipolar electrodes, providing essential information for the validation and development of the theory and applications of bipolar electrochemistry. This approach is based on the sensitive dependence of surface plasmon resonance imaging on the local electron density in the electrode, which enables the direct mapping of potential with a spatial resolution close to the optical diffraction limit, a temporal resolution of 50 ms, and a sensitivity of 10 mV. In addition, in contrast to previous optical readouts that relied on faradaic reactions, the present work achieved the impedance‐based measurements under non‐faradaic conditions. It is anticipated that this technique will greatly expand the application of bipolar electrochemistry as a platform for chemical and biosensing.     

Convolution potential sweep voltammetry V. Determination of charge transfer kinetics deviating from the Butler-Volmer behaviour

Convolution potential sweep voltammetry is applied to the analysis of charge transfer kinetics. The possibility of using the method without assuming a priori the validity of a given kinetic law, e.g. the Butler-Volmer law as usually done, is illustrated on the example of the reduction of tert-nitrobutane in acetonitrile and dimethylformamide. It is found that the post-factum experimental kinetics indeed deviate significantly from the Butler-Volmer behavior, involving a dependence of the transfer coefficient α upon the electrode potential. It is shown that the experimental variations of α match the orders of magnitude predicted by the Marcus theory. A procedure is proposed and applied for determining the reversible half-wave potential for redox couples in which one species is not quite stable chemically by combining the cyclic voltammetry and CPSV data.     

Ultra-high vacuum techniques in the study of single-crystal electrode surfaces

The development of powerful, surface-sensitive analytical methods has led to spectacular advances in the field of gas-solid interfacial science over the past two decades. Earlier research had been based upon thermodynamic and kinetic methods that portrayed only the macroscopic properties of the interfacial ensemble. The dearth of atomic-level information at that time is remarkably similar to what presently handicaps classical electrochemistry. In search of a more fundamental, microscopic view of electrode processes, research in modern electrochemistry has incorporated non-traditional approaches to the study of the electrode-solution interface. One approach, motivated by the overwhelming successes in vacuum-metal surface science, is the adaptation of ultra-high vacuum (UHV) surface spectroscopic techniques; such approach is the subject of the present review. This article describes the capabilities and limitations of coupled UHV-electrochemistry (UHV-EC) as a means to extract an atomic-level picture of the solid-electrolyte interface. After a brief introduction that outlines the experimental and theoretical obstacles in electrochemical surface science, this review presents a detailed discussion on experimental protocols (sample preparation, surface analytical techniques, instrument design) and critical processes (emersion, evacuation, surface characterization) inherent in the UHV-EC methodology. The final segment of this article summarizes selected studies with single-crystal electrode surfaces that showcase the power and elegance of the UHV-EC strategy; a more extensive bibliography of published investigations is provided in the Appendix. This review is concluded with a commentary on the future prospects of the UHV-EC approach.     

Kinetics of electroreduction of S<Subscript>2</Subscript>O<Stack><Subscript>8</Subscript><Superscript>2−</Superscript></Stack> anions on mechanically renewable silver electrode

The kinetics of electroreduction of peroxodisulfate anions on a mechanically renewed silver electrode is studied by voltammetric and impedance methods. Impedance diagrams obtained in the region of negatively charged metal surface are successfully modeled by the equivalent circuit formed by the solution resistance and also the reaction resistance connected in parallel with the constant-phase element substituted for the double layer capacitance. The analysis of experimental data carried out in terms of this circuit and their comparison with the literature data makes it possible to assume that the reduction kinetics of S₂O ₈ ^2? anions on this electrode can be adequately described in the framework of the phenomenological theory of slow discharge. The reasons for deviation of the literature data on the kinetics of this reaction on polycrystalline Ag electrode from the relationships following from the slow discharge theory are put forward and substantiated.