Rapid technological advances have revolutionized the industrial sector. These advances range from automation of industrial processes to autonomous industrial processes, where a human input is not required. Internet of Things (IoT), which has emerged a few years ago, has been embraced by industry, resulting in what is known as the Industrial Internet of Things (IIoT). IIoT refers to making industrial processes and entities part of the Internet. Restricting the definition of IIoT to manufacturing yields another subset of IoT, known as Industry 4.0. IIoT and Industry 4.0, will consist of sensor networks, actuators, robots, machines, appliances, business processes, and personnel. Hence, a lot of data of diverse nature would be generated. The industrial process requires most of the tasks to be performed locally because of delay and security requirements and structured data to be communicated over the Internet to web services and the cloud. To achieve this task, middleware support is required between the industrial environment and the cloud/web services. In this context, fog is a potential middleware that can be very useful for different industrial scenarios. Fog can provide local processing support with acceptable latency to actuators and robots in a manufacturing industry. Additionally, as industrial big data are often unstructured, it can be trimmed and refined by the fog locally, before sending it to the cloud. We present an architectural overview of IIoT and Industry 4.0. We discuss how fog can provide local computing support in the IIoT environment and the core elements and building blocks of IIoT. We also present a few interesting prospective use cases of IIoT. Finally, we discuss some emerging research challenges related to IIoT.
Abstract Smart manufacturing based on cyber-physical manufacturing systems (CPMS) has become the development trend and been widely recognized all over the world. Throughout the development trend of CPMS, one of the key issues is industrial Internet-of-Things (IIoT) with the characteristics of automation, smart connected, real-time monitoring, and collaborative control. Along with the permeation and applications of advanced technologies in manufacturing, massive amounts of data have been generated in the manufacturing process. However, the current 3th generation mobile network (3G), 4G and other communication technologies cannot meet the demands of CPMS for high data rate, high reliability, high coverage, low latency, etc., which hinders the development and implementation of CPMS. As a future advanced wireless transmission technology, 5G has a significant potential to promote IIoT and CPMS. Based on the architecture and characteristics of 5G wireless communication technology, this paper proposes the architecture of 5G-based IIoT, and describes the implementation methods of different advanced manufacturing scenarios and manufacturing technologies under the circumstances of three typical application modes of 5G, respectively, i.e., enhance mobile broadband (eMBB), massive machine type communication (mMTC), ultra-reliable and low latency communication (URLLC). Besides, the characteristics, key technologies and challenges of the 5G based IIoT are also analyzed.
Abstract Phenol and its derivatives from various man-made activities pose threats to public health and aquatic ecosystems. A number of technologies (e.g., adsorption, oxidation, and biological methods) have been proposed and tested to remove phenolic compounds from waste water. Among these technologies, membrane separation is considered one of the most efficient tools for abating phenolic compounds from waste water because of low capital cost, easy scalability, and ecofriendly production with the lowest emission of noxious compounds. In this review, we aim to address the potent role of membrane technology by evaluating its performance in separating various phenolic compounds from industrial effluents.
Given the tremendous success of the Internet of Things in interconnecting consumer devices, we observe a natural trend to likewise interconnect devices in industrial settings, referred to as industrial Internet of Things or Industry 4.0. While this coupling of industrial components provides many benefits, it also introduces serious security challenges. Although sharing many similarities with the consumer Internet of Things, securing the industrial Internet of Things introduces its own challenges but also opportunities, mainly resulting from a longer lifetime of components and a larger scale of networks. In this article, we identify the unique security goals and challenges of the industrial Internet of Things, which, unlike consumer deployments, mainly follow from safety and productivity requirements. To address these security goals and challenges, we provide a comprehensive survey of research efforts to secure the industrial Internet of Things, discuss their applicability, and analyze their security benefits.
Luís Fernando de Souza Cardoso, Flávia Cristina Martins Queiroz Mariano, E. Zorzal
Abstract This article aims to evaluate the impact of Augmented Reality (AR) applicability and usefulness on real industrial processes by employing a systematic literature review (SLR). The SLR was performed in five digital libraries to identify articles and reviews concerning the AR applicability from 2012 to 2018. A patent search in Google’s patents database was also conducted, for the same period. This paper describes how AR has been applied, which industries are most interested in the technology, how the technology has been developed to meet industry needs, as well as the benefits and challenges of AR. This survey concludes by providing a starting point for companies interested in integrating AR into their processes and proposing future directions for AR developers and researchers.
Matej Prijatelj, Ambrož Kregar, Andraž Kravos
et al.
Numerical modeling of bimetallic (BM) alloyed core‐shell catalyst degradation is particularly important, since it enables the evaluation of the complex interplay between the shell thickness‐dependent specific activity (SA), the resistance to electrochemical degradation, and the derivation of mitigation of poisoning resulting from dissolution of the alloying metal. Current state‐of‐the‐art BM particle degradation models rely on a discrete approach, which is restricted to the simulation of a limited selection of core‐shell particles rather than a full 2D distribution. In this study these challenges are overcome by developing a new BM catalyst degradation model based on the continuity equation and the rate of change of particle radii. Its applicability has been demonstrated by modeling the evolution of a 2D distribution of core and shell nanoparticles, and evaluating the loss of catalyst activity, not only in terms of changes in the catalyst's surface area, but also due to shell thickness‐dependent SA variation. These new features of the model are further utilized to design a degradation mitigation strategy based on mixing BM and pure platinum catalysts in order to limit the alloying metal dissolution, as well as to minimize the loss of electrochemical activity.
With the increasing adoption of lithium-ion batteries (LIBs) as the batteries of choice in electromobility, personal electronic devices, and so on, comes the challenge of ageing, which prevents the batteries from performing optimally and meeting the design intent. This is observed in the form of declining power capability due to the increase in resistance and the reduction in capacity that can be stored or discharged from them. Unfortunately, the cost of assessing batteries after the first use remains a daunting challenge. In our work, we propose an approach that carries out fast preliminary grading based on resistance and capacity by first connecting old cells of the same chemistry and model in series with resistors to limit the branch current, then connecting the branches in parallel to equalise the voltages. A Simulink model of NCR18650PF Panasonic cells with adaptive-series resistance is compared with a fixed-series resistance and found to improve the balancing time from over 24 h to just 8 h. Electrochemical impedance spectroscopy (EIS) was carried out on the individual balanced cells between 0.1 Hz and 5 kHz so that the real impedance, imaginary impedance, absolute impedance, and phase were compared with the SOH of the cells at each frequency. Results show that the imaginary impedance in the 6.6 Hz frequency range shows a good correlation coefficient > 0.98 with the SOH, especially with a state of charge (SOC) of about 75–85% for the LCO cells. By selecting only a sample from all the cells that covers a wide range of ages and carrying out a full-capacity checkup on them, a simple correlation with the SOH and the EIS measurements for different frequencies can be used to estimate the SOH of the other cells that were connected in the same parallel connection. This is a considerable time saving in the charge and discharge time on the other cells in facilities that lack the capacity for simultaneous cycling of all cells. There are also huge energy savings in not having to cycle all the cells. Therefore, it offers a more efficient approach to grading spent cells than carrying out full capacity tests.
Production of electric energy or power. Powerplants. Central stations, Industrial electrochemistry
Verena Šućurović, Nives Vladislavić, Ivana Škugor Rončević
Cigarette butts are an increasing environmental burden worldwide, and the quantities discarded each year could continue to rise. The chemical composition of cigarette butts, which comprises about 4000 different toxic chemicals, as well as their persistence in the environment and their potential negative effects pose a major threat to the environment as they regularly enter aquatic habitats and endanger water supplies and aquatic species. One effective way to reduce pollution is to recycle cigarette butts. The aim of this study is to evaluate the possibility of using extracts from cigarette butts (filter extract and extract from tobacco residues) as corrosion inhibitors for the Cu10Ni alloy in a 3.5% NaCl solution with a pH of 8 at different temperatures (12 °C, 20 °C and 25 °C). The determination of the electrochemical parameters, i.e., the corrosion behavior of the Cu10Ni alloy in a 3.5% NaCl solution and pH of 8, with and without modification of the alloy surface by cigarette butt extracts was tested using electrochemical measurements (electrochemical impedance spectroscopy and linear and potentiodynamic polarization methods). The surface properties of the Cu10Ni alloy modified with cigarette butt extracts were evaluated by goniometry, SEM analysis and FTIR spectrophotometry. The modification of the surface of the Cu10Ni alloy with an extract of tobacco residue and a filter extract separated from cigarette butts, whose presence on the surface was confirmed by the surface analysis methods, increased the corrosion resistance of the alloy, indicating that these substances have an inhibitory effect. The better inhibition properties (at all temperatures: 12 °C, 20 °C and 25 °C) were exhibited by the filter extract, and the highest inhibition effect was exhibited by the filter extract at 12 °C.
Plasma electrolytic oxidation (PEO) produces an oxide coating containing pores and cracks lowering corrosion protection. The defects can be sealed by in-situ or post-treatment methods. This work compares the sealing effect of SiO2 particles and post-alkali treatment on the corrosion resistance of PEO coatings formed on AZ31 magnesium (Mg) alloy. PEO was conducted in a phosphate-based electrolyte containing 2 g/l nanoparticle SiO2 at a constant current density of 300 A/m2 for 10 min. The post-alkali treatment was performed in 0.5 M NaOH solution at 80 °C for 30 min. The corrosion resistance was evaluated using polarization, electrochemical impedance spectroscopy, and weight loss tests. The SiO2 particles were successfully embedded uniformly in the Mg3(PO4)2 coating, enhancing the coating compactness and stability. The reinforced coating exhibited ten times higher impedance modulus and lower corrosion current density. The post-alkali treatment improved corrosion resistance but not as high as the SiO2 reinforcement. The impedance modulus of the alkali-treated specimen increased five times, and the corrosion current density decreased three times of the base coating. The weight loss test consistently showed that the SiO2-reinforced coating generated lower mass loss during 14 days of immersion in simulated body fluid.
Materials of engineering and construction. Mechanics of materials, Industrial electrochemistry
Kun-Ling Liu, Chung-Hsiang Chao, Hsin-Chieh Lee
et al.
A lithium-ion conducting triblock copolymer bearing pendant lithium sulfonates, termed as SSEBS-Li, is derived from commercial synthetic rubber poly(styrene-block-(ethylene-ran-butylene)-block-styrene); and free-standing quasi-solid polymer electrolyte (QSPE) membranes made of demonstrate high efficiency and high safety in the application for lithium metal batteries (LMBs). SSEBS-Li possesses a hybrid molecular structure containing “soft” segments that enable seamless contact with the lithium metal; and “hard” segments possessing anchored anions that offer continuous pathways to benefit lithium ion conduction and homogeneous lithium deposition. The unique molecular architecture features the QSPE membranes interpenetrated network microstructures to provide good mechanical strengths and ductility at a thickness of 25 µm. A high lithium ion conductivity of up to 5 × 10-4 S cm−1 at ∼ 35 wt% liquid electrolyte uptake is achieved, along with a high lithium transference number of 0.92 at room temperature. Galvanostatic cycling studies prove the excellent capability of SSEBS-Li QSPE in suppressing lithium dendrite growth. The Li//QSPE//LFP cell exhibits a high discharge capacity and excellent long-term stability after 300 cycles at 0.5C and room temperature without deleterious decay, elucidating a feasible and economical approach to improve the stability and safety of LMBs.
Poor cycling performance caused by massive volume expansion of silicon (Si) has always hindered the widespread application of silicon-based anode materials. Herein, bi-continuous silicon/carbon (Si/C) anode materials are prepared via magnesiothermic reduction of silica aerogels followed by pitch impregnation and carbonization. To fabricate the expected bi-continuous structure, mesoporous silica aerogel is selected as the raw material for magnesiothermic reduction. It is successfully reduced to mesoporous Si under the protection of NaCl. The as-obtained mesoporous Si is then injected with molten pitch via vacuuming, and the pitch is subsequently converted into carbon at a high temperature. The innovative point of this strategy is the construction of a bi-continuous structure, which features both Si and carbon with a cross-linked structure, which provides an area to accommodate the colossal volume change of Si. The pitch-derived carbon facilitates fast lithium ion transfer, thereby increasing the conductivity of the Si/C anode. It can also diminish direct contact between Si and the electrolyte, minimizing side reactions between them. The obtained bi-continuous Si/C anodes exhibit excellent electrochemical performance with a high initial discharge capacity of 1481.7 mAh g<sup>−1</sup> at a current density of 300 mA g<sup>−1</sup> and retaining as 813.5 mAh g<sup>−1</sup> after 200 cycles and an improved initial Coulombic efficiency of 82%. The as-prepared bi-continuous Si/C anode may have great potential applications in high-performance lithium-ion batteries.
Production of electric energy or power. Powerplants. Central stations, Industrial electrochemistry
Expanding energy generation from renewables is inevitable to reduce the impact of man-made climate change. With that, the need for intermediate energy storage is gaining in significance. Today, lithium-ion batteries (LIBs) are dominating mobile drive-trains and also play a key role in stationary energy storage. LIBs are incorporating critical raw materials in view of availability and economic importance, such as cobalt, lithium, copper and graphite. Sodium-based batteries, in which sodium replaces lithium as ionic charge-carrier, utilize the same working principles but substitute critical raw materials for abundant and cost-effective alternatives. Hard carbon replaces graphite as anode active material, copper foils are substituted by aluminum current collectors and manganese-based cobalt-free layered host lattices offer promising performance as cathode active material 1,2. By applying established production processes, investment costs are reduced and a rapid scale-up is enabled (Drop-In technology) 3, making SIBs a sustainable, efficient and cost-effective complementary technology to LIBs 4. Among various known cathode active materials for SIBs, the family of layered sodium transition metal oxides (NaxMO2, 1>x>0) offers promising electrochemical performance 2,5–7. These compounds show a wide structural variety (O3, P3, P2) due to the ionic radius of sodium and the tendency for Na+/vacancy ordering 8. The scope of our presentation will be low-cost manganese-based, cobalt-free layered NaxMnyNi1-yO2 cathode active materials for SIBs. We will discuss the influence of the transition metal stoichiometry y on the structure based on Neutron and X-ray diffraction experiments. Using advanced electrochemical methods and diffraction experiments, these structural models are then correlated with physical and electrochemical properties such as Na+/vacancy orderings, solid diffusion coefficients and potential profiles. For y = 3/4, a synthesis phase diagram will be presented covering a broad range of sodium content x and calcination temperature. For phase-pure P2-NaxMn3/4Ni1/4O2, we will present the influence of the calcination process on the structure and discuss the electrochemical properties in half-cells in-depth. For optimized materials, attractive initial specific discharge capacities beyond 220 mAh g-1 are obtained in sodium half-cells between 1.5 – 4.3 V. A capacity decay occurs during electrochemical cycling within this full voltage window. The origin of the capacity decay will be discussed based on electrochemical studies and ex-situ investigations of the morphology with SEM and local structure with HRTEM. Finally, we will present the influence of storage in ambient air to gain insights on the large-scale processability of the materials. The chosen synthesis route adapts industrially established processes for NCM production for SIB cathode materials, enables to tune powder properties to technical specifications and is highly scalable. The broad scope of this work addresses raw material questions, fundamental investigations and industrially relevant production processes. ACKNOWLEDMENTS: The German Federal Ministry of Education and Research (BMBF) supported this work within the project TRANSITION (03XP0186C) and ExcellBattMat (03XP0257A and 03XP0257C). REFERENCES Larcher, D. & Tarascon, J.-M. Towards greener and more sustainable batteries for electrical energy storage. Nature Chem 7, 19–29; 10.1038/nchem.2085 (2015). Hasa, I. et al. Challenges of today for Na-based batteries of the future: From materials to cell metrics. Journal of Power Sources 482, 228872; 10.1016/j.jpowsour.2020.228872 (2021). Tarascon, J.-M. Na-ion versus Li-ion Batteries: Complementarity Rather than Competitiveness. Joule 4, 1616–1620; 10.1016/j.joule.2020.06.003 (2020). Vaalma, C., Buchholz, D., Weil, M. & Passerini, S. A cost and resource analysis of sodium-ion batteries. Nat Rev Mater 3, 1–11; 10.1038/natrevmats.2018.13 (2018). Nagore Ortiz-Vitoriano, Nicholas E. Drewett, Elena Gonzalo & Teófilo Rojo. High performance manganese-based layered oxide cathodes: overcoming the challenges of sodium ion batteries. Energy Environ. Sci. 10, 1051–1074; 10.1039/C7EE00566K (2017). Nuria Tapia-Ruiz et al. 2021 roadmap for sodium-ion batteries. J. Phys. Energy 3, 31503; 10.1088/2515-7655/ac01ef (2021). Gonzalo, E., Zarrabeitia, M., Drewett, N. E., López del Amo, Juan Miguel & Rojo, T. Sodium manganese-rich layered oxides: Potential candidates as positive electrode for Sodium-ion batteries. Energy Storage Materials 34, 682–707; 10.1016/j.ensm.2020.10.010 (2021). Kubota, K., Kumakura, S., Yoda, Y., Kuroki, K. & Komaba, S. Electrochemistry and Solid‐State Chemistry of NaMeO 2 (Me = 3d Transition Metals). Adv. Energy Mater. 8, 1703415; 10.1002/aenm.201703415 (2018).
Abstract Alzheimer disease is a progressive age-related neurodegenerative disorder estimated to affect up to 107 million people by 2050, its pathology being associated with the dysfunction of amyloid β (Aβ) peptide mechanism, among others. Electrochemical methods were successfully applied for Aβ electrochemical characterisation, and have received increased attention in Aβ research. This review discusses the recent advances on the direct electrochemical detection of Aβ redox mechanisms, fibrilization, and interaction with metal ions, based on the electrochemical detection of the Aβ’s , and amino acid residues oxidation peaks.
Nick Sleegers, A. V. van Nuijs, M. A. van den Berg
et al.
The electrochemical detection of cephalosporins is a promising approach for the monitoring of cephalosporin levels in process waters. However, this class of antibiotics, like penicillins, is composed of chemically active molecules and susceptible to hydrolysis and aminolysis of the four membered β-lactam ring present. In order to develop a smart monitoring strategy for cephalosporins, the influence of degradation (hydrolysis and aminolysis) on the electrochemical fingerprint has to be taken into account. Therefore, an investigation was carried out to understand the changes of the voltammetric fingerprints upon acidic and alkaline degradation. Changes in fingerprints were correlated to the degradation pathways through the combination of square wave voltammetry and liquid chromatography quadrupole time-of-flight analysis. The characteristic electrochemical signals of the β-lactam ring disappeared upon hydrolysis. Additional oxidation signals that appeared after degradation were elucidated and linked to different degradation products, and therefore, enrich the voltammetric fingerprints with information of the state of the cephalosporins. The applicability of the electrochemical monitoring system was explored by the analysis of the intact and degraded industrial process waters containing the key intermediate 7-aminodeacetoxycephalosporanic acid (7-ADCA). Clearly, the intact process samples exhibited the expected core signals of 7-ADCA and could be quantified, while the degraded samples only showed the newly formed degradation products.
In 2016, an Editorial in ACS Nano, entitled “The Rising and Receding Fortunes of Electrochemists”, reflected the growing scientific consensus that existing initiatives in fundamental research were undermatched to the fact that electrochemistry was becoming ubiquitous in applications in energy, thus handicapping progress toward social impact. That same year, Next Generation Electrochemistry (NGenE) hosted its first edition at the University of Illinois at Chicago (UIC). NGenE is an annual summer workshop focused on describing emerging challenges at the frontiers of research in electrochemistry and the application of innovative strategies to address them. The original premise behind NGenE was also that, despite its reach and importance, fundamental electrochemistry had gone through a rather slow period of activity in the early 21st century compared to many companion fields. Back in 2016, one of the causes was ascribed to a deficit in electrochemistry training at the graduate level, leading to calls for increased emphasis in research in this area. Since 2016, NGenE has tackled these deficiencies by broadening the knowledge and perspective of senior graduate students and postdoctoral researchers. A series of world-renowned experts in various walks of electrochemistry examine fundamental phenomena at an advanced level, identifying critical gaps in our understanding and innovative strategies to address them. The program assumes baseline knowledge and prior experience in electrochemistry. NGenE does not ask, “What is electrochemistry?” but instead, “What will electrochemistry become?”. As such, it addresses the very same issues raised in the aforementioned Editorial. Fast-forwarding five years, support and activities in fundamental electrochemical research have undergone very significant growth. Furthermore, new applications of electrochemistry that were not on our radar in 2016 have emerged, especially among organic chemists. It is an exciting time to be an electrochemist, and new generations of leaders in research are increasingly pursuing this path. Simultaneously, NGenE has evolved from a program with a focus on rather specific topics, such as batteries, to expose the major diversity of fields interested in electrochemistry and finding common elements between their challenges. In 2020, the world ground to a halt with the onset of the COVID-19 pandemic, and NGenE had to adapt to the reality that meetings in person were not possible. The program migrated from a format of interactive lectures led by individual researchers to panel discussions involving multiple researchers talking to each other and with the attendees, who were provided the virtual floor to ask questions. The outcome was a series of highly dynamic discussions that are now free to watch on demand by anyone in the world. NGenE 2021 was divided into a series of panels, each dedicated to a specific topic at the frontiers of electrochemical research. In this status report, we summarize the key messages emerging from the discussions. While some panels covered aspects not limited to energy technology, the commonality of lessons and challenges highlights the many opportunities ahead for cross-pollination to establish electrochemistry as central to our current transition away from the fossil-fuel paradigm. By sharing them here, we strive to motivate the community to pursue directions that move us beyond the current frontiers. This summary is divided in themes that map out of the specific panel topics. Can Electrochemistry Replace Thermochemistry? In thermochemistry, temperature and pressure are major driving forces for chemical transformations. Existing high-temperature thermochemical processes rely on burning fossil fuels to achieve high temperatures in the furnace, reactor, or kiln. By burning fossil fuels to achieve the desired chemical transformation, CO2 is emitted, which adds to its toll as a major greenhouse gas. Steel and cement manufacturing, steammethane reforming, and the Haber−Bosch process are some of the examples of thermochemical processes at high temperatures that are challenging to decarbonize. These industries rely on mature technologies that have evolved over decades and have not changed significantly in the past decade. With the sustained declines in the cost of installing and using renewable sources of energy, electricity continues its transition to becoming a sustainable energy carrier free of emissions of greenhouse gases. All the major sources of renewable and carbon-neutral energy (solar, wind, nuclear) generate electricity, ensuring that a renewably powered society will be electrified. Shifting from thermochemistry to electrochemistry in industrial production could accelerate this transition by relying on electricity free of emissions. Electrifying the generation of heat is one way that could enable an electrified thermochemical industry. However, estimates suggest that if all thermal needs were electrified, it would be necessary to double the electricity running through the distribution system. This transition will be challenging without a tremendous increase in electrical transmission and
[Electrochemistry exploits local current heterogeneities at various scales ranging from the micrometer to the nanometer. The last decade has witnessed unprecedented progress in the development of a wide range of electroanalytical techniques allowing to reveal and quantify such heterogeneity through multiscale and multifonctionnal operando probing of electrochemical processes. However most of these advanced electrochemical imaging techniques, employing scanning probes, suffer from either low imaging throughput or limited imaging size. In parallel, optical microscopies, which can image a wide field of view in a single snapshot, have made considerable progress in terms of sensitivity, resolution and implementation of detection modes. Optical microscopies are then mature enough to propose, with basic bench equipment, to probe in a non destructive way a wide range of optical (and therefore structural) properties of a material in situ, in real time: under operating conditions. They offer promising alternative strategies for quantitative high-resolution imaging of electrochemistry. The first sections recall the optical properties of materials and how they can be probed optically. They discuss fluorescence, Raman, surface plasmon resonance, scattering or refractive index. Then the different optical microscopes used to image electrochemical processes are examined along with some strategies to extract quantitative electrochemical information from optical images. Finally the last section reviews some examples of in situ imaging, at microto nanometer resolution, and quantification of electrochemical processes ranging from solution diffusion to the conversion of molecular interfaces or solids.]
Abstract An increasing number of strategies and tools have been proposed to endow the electrochemical interphase with chirality, to achieve enantiodiscrimination in analytical and/or preparative applications. So far, chirality has mostly been implemented not only at the electrode surface side but also on the medium one. Recently, the attractiveness of the latter approach has remarkably increased on account of the increasing availability of advanced chiral molecular media with intrinsic attractive features for electrochemistry applications, such as chiral ionic liquids, chiral ionic liquid crystals, and chiral deep eutectic solvents. With respect to solid layer/fixed chiral networks, advanced chiral media can still offer a reasonably high degree of local structuring, while being less demanding concerning preparation and management protocols, as well as less sensitive to fouling/regeneration issues. Different ways to implement chirality in advanced molecular media, including cases of powerful ‘inherent chirality,’ will be presented and discussed, particularly focusing on recent applications in the electrochemical field.