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    A Beginners’ Guide to Modelling of Electric Double Layer under Equilibrium, Nonequilibrium and AC Conditions
    Lu-Lu Zhang, Chen-Kun Li, Jun Huang
    Journal of Electrochemistry    2022, 28 (2): 2108471-.   DOI: 10.13208/j.electrochem.210847
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    In electrochemistry, perhaps also in other time-honored scientific disciplines, knowledge labelled classical usually attracts less attention from beginners, especially those pressured or tempted to quickly jam into research fronts that are labelled, not always aptly, modern. In fact, it is a normal reaction to the burden of history and the stress of today. Against this context, accessible tutorials on classical knowledge are useful, should some realize that taking a step back could be the best way forward. This is the driving force of this article themed at physicochemical modelling of the electric (electrochemical) double layer (EDL). We begin the exposition with a rudimentary introduction to key concepts of the EDL, followed by a brief introduction to its history. We then elucidate how to model the EDL under equilibrium, using firstly the orthodox Gouy-Chapman-Stern model, then the symmetric Bikerman model, and finally the asymmetric Bikerman model. Afterwards, we exemplify how to derive a set of equations governing the EDL dynamics under nonequilibrium conditions using a unifying grand-potential approach. In the end, we expound on the definition and mathematical foundation of electrochemical impedance spectroscopy (EIS), and present a detailed derivation of an EIS model for a simple EDL. We try to avoid the omission of supposedly ‘trivial’ information in the derivation of models, hoping that it can ease the access to the wonderful garden of physical electrochemistry.

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    Research Progress and Performance Improvement Strategies of Hard Carbon Anode Materials for Sodium-Ion Batteries
    Xiuping Yin, Yufeng Zhao, Jiujun Zhang
    Journal of Electrochemistry    DOI: 10.13208/j.electrochem.2204301
    Accepted: 13 June 2022

    In- Situ/ Operando 57Fe Mössbauer Spectroscopic Technique and Its Applications in NiFe-based Electrocatalysts for Oxygen Evolution Reaction
    Jafar Hussain Shah, Qi-Xian Xie, Zhi-Chong Kuang, Ri-Le Ge, Wen-Hui Zhou, Duo-Rong Liu, Alexandre I. Rykov, Xu-Ning Li, Jing-Shan Luo, Jun-Hu Wang
    Journal of Electrochemistry    2022, 28 (3): 2108541-.   DOI: 10.13208/j.electrochem.210854
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    The development of highly efficient and cost-effective electrocatalysts for the sluggish oxygen evolution reaction (OER) remains a significant barrier to establish effective utilization of renewable energy storage systems and water splitting to produce clean fuel. The current status of the research in developing OER catalysts shows that NiFe-based oxygen evolution catalysts (OECs) have been proven as excellent and remarkable candidates for this purpose. But it is critically important to understand the factors that influence their activity and underlying mechanism for the development of state-of-the-art OER catalysts. Therefore, the development of in-situ/operando characterizations is urgently required to detect key intermediates along with active sites and phases responsible for OER. 57Fe Mössbauer spectroscopy is one of the appropriate and suitable techniques for determining the phase structure of catalysts under their electrochemical working conditions, identifying the active sites, clarifying the catalytic mechanisms, and determining the relationship between catalytic activity and the coordination structure of catalysts. In this tutorial review, we have discussed the current status of research on NiFe-based catalysts with particular attention to introduce in detail the knowhow about the development and utilization of in-situ/operando57Fe Mössbauer-electrochemical spectroscopy for the study of OER mechanism. A brief overview using NiFe-(oxy)hydroxide catalysts, derived from ordered porous metal-organic framework (MOF) material NiFe-PBAs (Prussian blue analogues), as a typical model study case for the OER electrocatalyst and self-designed in-situ/operando57Fe Mössbauer-electrochemical instrument, has been provided for the better understanding of readers. Moreover, using in-situ/operando57Fe Mössbauer spectroscopy, the crucial role of Fe species during OER reaction has been explained very well.

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    Brain Electrochemistry
    Cong Xu, Ying Jiang, Ping Yu, Lan-Qun Mao
    Journal of Electrochemistry    2022, 28 (3): 2108551-.   DOI: 10.13208/j.electrochem.210855
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    Brain, as the source of neural activities such as perceptions and emotions, consists of the dynamic and complex networks of neurons that implement brain functions through electrical and chemical interactions. Therefore, analyzing and monitoring neurochemicals in living brain can greatly contribute to uncovering the molecular mechanism in both physiological and pathological processes, and to taking a further step in developing precise medical diagnosis and treatment against brain diseases. Through collaborations across disciplines, a handful of analytical tools have been proven to be befitting in neurochemical measurement, spanning the level of vesicles, cells, and living brains. Among these, electrochemical methods endowed with high sensitivity and spatiotemporal resolution provide a promising way to precisely describe the dynamics of target neurochemicals during various neural activities. In this review, we expand the discussion on strategies to address two key issues of in vivo electrochemical sensing, namely, selectivity and biocompatibility, taking our latest studies as typical examples. We systematically elaborate for the first time the rationale behind engineering electrode/brain interface, as well as the unique advantages of potentiometric sensing methods. In particular, we highlight our recent progress on employing the as-prepared in vivo electrochemical sensors to unravel the molecular mechanism of ascorbate in physiological and pathological processes, aiming to draw a blueprint for the future development of in vivo electrochemical sensing of brain neurochemicals.

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    In Situ Characterization of Electrode Structure and Catalytic Processes in the Electrocatalytic Oxygen Reduction Reaction
    Ya-Chen Feng, Xiang Wang, Yu-Qi Wang, Hui-Juan Yan, Dong Wang
    Journal of Electrochemistry    2022, 28 (3): 2108531-.   DOI: 10.13208/j.electrochem.210853
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    As an electrochemical energy conversion system, fuel cell has the advantages of high energy conversion efficiency and high cleanliness. Oxygen reduction reaction (ORR), as an important cathode reaction in fuel cells, has received extensive attention. At present, the electrocatalysts are still one of the key materials restricting the further commercialization of fuel cells. The fundamental understanding on the catalytic mechanism of ORR is conducive to the development of electrocatalysts with the enhanced activity and high selectivity. This review aims to summarize the in situ characterization techniques used to study ORR. From this perspective, we first briefly introduce the advantages of various in situ techniques in ORR research, including electrochemical scanning tunneling microscopy, infrared spectroscopy, Raman spectroscopy, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. Then, the applications of various in situ characterization techniques in characterizing of the catalyst morphological evolution and electronic structure as well as the identification of reactants and intermediates in the catalytic process are summarized. Finally, the future development of in situ technology is outlooked.

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    Development Status of Copper Electroplating Filling Technology in Through Glass Via for 3D Interconnections
    Zhi-Jing Ji, Hui-Qin Ling, Pei-Lin Wu, Rui-Yi Yu, Da-Quan Yu, Ming Li
    Journal of Electrochemistry    2022, 28 (6): 2104461-.   DOI: 10.13208/j.electrochem.210446
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    With the slow development of Moore's Law, the high density and miniaturization of microelectronic devices put forward higher requirements for advanced packaging technology. As a key technology in 2.5D/3D packaging, interposer technology has been extensively studied. According to different interposer materials, it is mainly divided into organic interposer, silicon interposer and glass interposer. Compared with the through silicon via (TSV) interconnection, the through glass via (TGV) interposer has received extensive attention in the 2.5D/3D advanced packaging field for its advantages of excellent high-frequency electrical characteristics, simple process, low cost, and adjustable coefficient of thermal expansion (CTE). However, the thermal conductivity of glass (about 1 W·m-1·K-1) is much lower than that of silicon (about 150 W·m-1·K-1), thus, the glass interposer has serious heat dissipation problems. In order to obtain a high-quality TGV interposer, not only an efficient and low-cost via preparation process, but also a defect-free filling process is required. The challenges faced by glass interposer is mainly concentrated in these two aspects. This review firstly introduces the preparation process of TGV, such as ultra-sonic drilling (USD), ultra-sonic high speed drilling (USHD), wet etching, deep reactive ion etching (DRIE), photosensitive glass, laser etching, laser induced deep etching (LIDE), etc. Then it summarizes the defect-free filling of TGV, and outlines several filling mechanisms and some current filling processes of TGV, such as bottom-up filling mechanisms, butterfly filling mechanisms and conformal filling mechanisms. Among the filling mechanisms of the above three filling methods, the filling method of bottom-up is the most studied one, and many scholars have given relevant explanations. Currently, the main ones that are commonly used are the diffusion-consumption mechanism, curvature enhanced adsorbate coverage mechanism (CEAC), convection dependent adsorption mechanism (CDA), and S-shaped negative differential resistance theory. In the process of TGV filling, the type and concentration of base bath, additives and electroplating process will affect the filling status of TGV. At present, the constant current plating mode is most commonly used in the process of TGV filling. Then the research progress of TGV electroplating additives is introduced, including the action mechanism of typical additives and the current research status of some new additives. Through glass via technology can be filled with the synergistic action of accelerators, suppressors and levelers. Finally, the practical application of TGV is briefly reviewed, for example, glass interposer is used in 3D integrated passive device (IPD), embedded glass fan-out technology (eGFO), integrated antenna packaging, micro-electro-mechanical system (MEMS), multi-chip module packaging, as well as the applications in the field of optical integration technology.

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    Alkaline Water Electrolysis for Efficient Hydrogen Production
    Wen-Fu Xie, Ming-Fei Shao
    Journal of Electrochemistry    2022, 28 (10): 22014008-.   DOI: 10.13208/j.electrochem.2214008
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    Hydrogen production from water electrolysis is a sustainable and environmentally benign strategy in comparison with fossil fuel-based hydrogen. However, this promising technique suffers from the high energy consumption and unsatisfactory cost due to the sluggish kinetics of both half reaction and inferior stability of electrocatalysts. To address this challenge, herein, we present a timely and comprehensive review on advances in alkaline water electrolysis that is already commercialized for large scale hydrogen production. The design principles and strategies with aiming to promote the performance of hydrogen generation are discussed from the view of electrocatalyst, electrode, reaction and system. The challenges and related prospects are presented at last, hopefully to provide essential ideas and to promote the wide application of hydrogen production.

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    Magnetic Resonance in Metal-Ion Batteries: From NMR (Nuclear Magnetic Resonance) to EPR (Electron Paramagnetic Resonance)
    Bing-Wen Hu, Chao Li, Fu-Shan Geng, Ming Shen
    Journal of Electrochemistry    2022, 28 (2): 2108421-.   DOI: 10.13208/j.electrochem.210842
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    Metal-ion batteries have changed our quotidian lives. The research on the electrode materials for metal-ion battery is the key to improve the performance of the battery. Therefore, understanding the structure-performance relationship of the electrode materials can help to improve the energy density and power density of the materials. Magnetic resonance, including nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR), has been continuously improved during the past three decades, and has gradually become one of the important technologies to study the structure-performance relationship of electrode materials. This paper summarizes the progress of magnetic resonance research from our group on several interesting electrode materials and demonstrates the important role of NMR and EPR in the study of electrode materials. This article will help to grasp the important value of magnetic resonance technology for battery research, which will promote the further development of advance magnetic resonance technology.

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    Structural Degradation of Ni-Rich Layered Oxide Cathode for Li-Ion Batteries
    Jia-Yi Wang, Sheng-Nan Guo, Xin Wang, Lin Gu, Dong Su
    Journal of Electrochemistry    2022, 28 (2): 2108431-.   DOI: 10.13208/j.electrochem.210843
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    Nickel(Ni)-rich layered oxide has been regarded as one of the most important cathode materials for the lithium-ion batteries because of its low cost and high energy density. However, the concerns in safety and durability of this compound are still challenging for its further development. On this account, the in-depth understanding in the structural factors determining its capacity attenuation is essential. In this review, we summarize the recent advances on the degradation mechanisms of Ni-rich layered oxide cathode. Progresses in the structure evolution of Ni-rich oxide are carefully combed in terms of inner evolution, surface evolution, and the property under thermal condition, while the state-of-the-art modification strategies are also introduced. Finally, we provide our perspective on the future directions for investigating the degradation of Ni-rich oxide cathode.

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    Research Progresses of Cobalt Interconnect and Superfilling by Electroplating in Chips
    Li-Jun Wei, Zi-Han Zhou, Yun-Wen Wu, Ming Li, Su Wang
    Journal of Electrochemistry    2022, 28 (6): 2104431-.   DOI: 10.13208/j.electrochem.210443
    Abstract801)   HTML54)    PDF(pc) (2665KB)(608)       Save

    Copper interconnect using dual damascene technology has always been the main means for metallization in the back end of line process. However, with the size effect becoming more and more obvious due to feature size reduction, copper interconnect can no longer meet the demand for high circuit speed in Post-Moore era. Following copper interconnection, cobalt interconnection in chips attracts much attention as an interconnect technology by the next generation, which has been introduced in 7 nm node of integrated circuit manufacturing and below. The electron mean free path of cobalt (~10 nm) is much shorter than copper’s (39 nm), thus exhibiting the potential to further shrink the critical dimension without increasing line resistance and RC delay especially for contacts or local interconnects in the first few stack layers. Also, cobalt is considered as a suitable barrier/liner material, which means implementing cobalt interconnects needs no such layers and gives more space for conductive metal. Besides, higher melting point of cobalt makes it more favorable with good electromigration resistance compared with copper interconnects. Cobalt interconnection mainly adopts the wet electrodeposition method and the quality of the electrodeposite matters a lot to the reliability of the metal interconnects. For the reason of confidentiality and the limitation of research conditions, there are few research reports about cobalt interconnection. Based on existing patents and literature reports, this paper systematically introduces the advantages and current developments of cobalt interconnection. To better understand the behavior of the metal ions during electroplating process, this paper reviews the basic technology, bath composition and additives used in the electrolyte for cobalt electroplating from the point of view of solution chemistry and electrochemistry. For superconformal electroplating, there are several superfilling mechanisms for bottom-up electrodeposition with different emphasis, this paper gives a brief summary about three mechanisms and makes a comparison. Furthermore, this paper introduces the annealing control of cobalt deposition and the influence of impurities, since the evolution of grains and migration of impurities determine the sheet resistance. Finally, further study of cobalt interconnection technology is prospected. Cobalt interconnect is expected to be a proper alternative to extend Moore’s Law and promises to play a part in next advanced technology node. More researches about cobalt interconnection are worthwhile to be carried out in the future.

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    Study and Improvement on Expansion Property of Silicon Oxide
    Wei-Chuan Qiao, Fang-Ru Li, Jin-Lin Xiao, Li-Juan Qu, Xiao Zhao, Meng Zhang, Chun-Lei Pang, Zi-Kun Li, Jian-Guo Ren, Xue-Qin He
    Journal of Electrochemistry    2022, 28 (5): 2108121-.   DOI: 10.13208/j.electrochem.210812
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    The silicon-based anode materials have the potential to meet the ever-increasing demand for energy density in lithium-ion batteries market owing to their high theoretical specific capacity. Unfortunately, their commercialization was hindered by the continuous volume expansion. Herein, the expansion characteristics and corresponding mechanism of the silicon oxide and graphite-silicon oxide composites were investigated by in-situ displacement detection systematically. The results showed that the expansion property was improved by material process modifications. During the de/lithiation processes of graphite, the expansion ratio in 30% ~ 50% SOC changed little because of the small interlayer spacing variation of the intercalated graphite. Unlike the graphite anode, there was no obvious platform in the expansion ratio curve of silicon oxide except for the first lithiation process. As for the graphite-silicon oxide composite, the expansion ratio was influenced by two-component materials. In order to figure out how the expansion ratio of the composite changed, the capacity contributions of graphite and silicon oxide at various states of charge were calculated. It was found that the graphite dominated the initial stage of the first and second delithiation processes, while delithiation of silicon oxide started from 36% SOC, leading to the steep decline of the expansion ratio curves. During the second lithiation process, the capacity of the first 20% SOC mainly came from silicon oxide, after which the capacity proportion of graphite increased gradually. In 40% ~ 50% SOC region, the capacity contribution of silicon oxide was negligible, resulting in the reduction of expansion increase rate. The calculated capacity contribution of the component materials corresponded to the evaluation of expansion ratio, indicating the reliability of the calculation method, which could be applied in other graphite-silicon oxide composites with different proportions. The irreversible expansion of graphite mainly occurred at the first three charges processes, while the irreversible expansion of silicon oxide increased significantly over all cycling processes. The reversible expansion of silicon oxide decreased gradually as the capacity fading. And the total expansion of silicon oxide tended to be decreased from the third cycle because the decrement of reversible expansion surpassed the increment of irreversible expansion. Finally, the expansion ratio especially the irreversible expansion of silicon oxide was effectively reduced by optimizing the surface coating, prelithiation and particle size. These results could provide favorable guidance for developing high-performance silicon-based anode materials with stable structure and low expansion ratio.

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    Multi-Scale Simulation Revealing the Decomposition Mechanism of Electrolyte on Lithium Metal Electrode
    Yan-Yan Zhang, Yue Liu, Yi-Ming Lu, Pei-Ping Yu, Wen-Xuan Du, Bing-Yun Ma, Miao Xie, Hao Yang, Tao Cheng
    Journal of Electrochemistry    2022, 28 (4): 2105181-.   DOI: 10.13208/j.electrochem.210518
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    Lithium metal is considered as an ideal anode material for next-generation high energy density batteries with its high specific capacity and low electrode potential. However, the high activity of lithium metal can lead to a series of safety issues. For example, lithium metal will continuously react chemically with the electrolyte, forming unstable the solid electrolyte (SEI) films. In addition, lithium dendrites can be formed during cycling, which can puncture the SEI film and cause short circuits in the battery. These drawbacks greatly hinder the commercial application of lithium metal. To solve the above problems, it is important to understand the structure of SEI and the underlying mechanism of its formation as a guide for rational design. Quantum mechanics (QM) has been demonstrated as an effective tool to investigate the chemical reactions and microscopic atomic structures of SEI. However, QM is computationally too expensive to be used for large-scale and long-term theoretical simulations. Instead, the molecular mechanics (MM) method has much orders higher computational efficiency than QM, and can be used for large-scale and long-time theoretical simulations. However, the accuracy of MM is usually not guaranteed, especially for complex SEI. Therefore, a practical solution is to combine the advantages of both. In this work, we use the hybrid ab initio and reactive molecule dynamics (HAIRs) approach to describe chemical reactions with the accuracy of quantum chemistry and improve the computational efficiency by more than 10 times with mixing QM and MM. Using this method, we have investigated the interfacial reaction mechanism of two electrolyte solutions, 1 mol·L-1 LiTFSI-DME (dimethoxyethane) and 1 mol·L-1 LiTFSI-EC (ethylene carbonate) with the lithium metal anode. The simulation results show that TFSI anion prefers to be decomposed, while DME does not, thus, TFSI plays the vital role of protecting DME. However, in the LiTFSI-EC system, both TFSI anion and EC are decomposed, indicating that EC is less stable and not suitable to the formation of stable SEI. Thanks to the computational efficiency of the HAIRs method, we have completed the 1 ns simulation in a few days. Using the hardware, the above calculation would take at least one to two months if only the QM method was employed. Meanwhile the long HAIRs calculation shows that for the simulation of chemical reactions in SEI, at least 1 ns is essential. Instead, previous molecular dynamics (MD) simulations with a few ps, or tens of ps, are insufficient to fully capture the critical chemical reactions. The above simulation results provide reliable experience for the computational simulation study of SEI formation, and lay the theoretical foundation for the rational design of electrolytes and the development of high-performance electrolyte solution systems.

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    Facet Dependent Oxygen Evolution Activity of Spinel Cobalt Oxides
    Li-Hua Zhang, Hong-Yuan Chuai, Hai Liu, Qun Fan, Si-Yu Kuang, Sheng Zhang, Xin-Bin Ma
    Journal of Electrochemistry    2022, 28 (2): 2108481-.   DOI: 10.13208/j.electrochem.210848
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    Water splitting is a promising technology to produce clean hydrogen if powered by renewable energies, where oxygen evolution is the rate determining step at an anode. Here we adjust the different crystal planes of the cobalt oxides catalyst to expose more effective active sites through a hydrothermal process, so as to improve the reaction activity for oxygen evolution. The samples were well characterized by TEM, SEM and XRD. Among the three synthetic crystal planes (100), (111) and (110) of spinel cobalt oxides, the (100) crystal plane has the highest intrinsic activity. Combining in-situ infrared and DFT calculations, we observed that the oxygen evolution reaction reached the lowest energy barrier on the (100) plane of the cobalt oxide crystal. Further XPS analysis showed that the highest Co 3+/Co2+ ratio was observed on the surface of the nanocube samples, indicating that Co3+ is a more active site for oxygen evolution catalytic activity.

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    Recent Development of Low Iridium Electrocatalysts toward Efficient Water Oxidation
    Jing Ni, Zhao-Ping Shi, Xian Wang, Yi-Bo Wang, Hong-Xiang Wu, Chang-Peng Liu, Jun-Jie Ge, Wei Xing
    Journal of Electrochemistry    2022, 28 (9): 2214010-.   DOI: 10.13208/j.electrochem.2214010
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    Developing high-performance and low-cost electrocatalysts for oxygen evolution reaction (OER) is the key to implementing polymer electrolyte membrane water electrolyzer (PEMWE) for hydrogen production. To date, iridium (Ir) is the state-of-the-art OER catalyst, but still suffers from the insufficient activity and scarce earth abundance, which results in high cost both in stack and electricity. Design low-Ir catalysts with enhanced activity and stability that can match the requirements of high current and long-term operation in PEMWE is thus highly desired, which necessitate a deep understanding of acidic OER mechanisms, unique insights of material design strategies, and reliable performance evaluation norm, especially for durability. With these demand in mind, we in this review firstly performed a systematic summary on the currently recognized acidic OER mechanism on both activity expression (i.e. the adsorbate evolution mechanism, the lattice oxygen mediated mechanism and the multi-active center mechanism) and inactivation (i.e. active species dissolution, evolution of crystal phase and morphology, as well as catalyst shedding and active site blocking), which can provide guidance for material structural engineering towards higher performance in PEMWE devices. Subsequently, we critically reviewed several types of low-Ir OER catalysts recently reported, i.e. multimetallic alloy oxide, supported, spatially structured and single site catalysts, focusing on how the performance has been regulated and the underlying structure-performance relationship. Lastly, the commonly used indicators for catalyst stability evaluation, wide accepted deactivation characterization techniques and the lifetime probing methods mimicking the practical operation condition of PEMWE are introduced, hoping to provide a basis for catalyst screening. In the end, few suggestions on exploring future low-Ir OER catalysts that can be applied in the PEMWE system are proposed.

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    Electrochemical Deposition of Copper Pillar Bumps with High Uniformity
    Bai-Zhao Tan, Jian-Lun Liang, Zi-Liang Lai, Ji-Ye Luo
    Journal of Electrochemistry    2022, 28 (7): 2213004-.   DOI: 10.13208/j.electrochem.2213004
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    Electrochemical deposition of copper pillar bumps (CPBs) is one of the key technologies for the advanced packaging. In this study, the effects of the additive concentration, the electrolyte convection, the current density, and the electroplating system on the uniformity of the CPBs have been systematically investigated. The results showed that the profiles of the CPBs were mainly determined by the additive concentration, the bath convection and the current density, while the heights of the CPBs were mainly affected by the electroplating system. For the CPBs profiles, it was found that the low leveler concentration and high current density would generally result in domed shape, while the uneven agitation would lead to inclined surface. For the heights of CPBs, the macroscopic uniformity could be dramatically improved by a sophisticatedly designed electroplating system. These results can provide basic guidance for the optimization of the CPBs electroplating.

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    Mass Loading Optimization for Ethylene Glycol Oxidation at Different Potential Regions
    Sheng-Nan Sun, Zhi-Chuan Xu
    Journal of Electrochemistry    2022, 28 (2): 2108411-.   DOI: 10.13208/j.electrochem.210841
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    Designing and fabricating the electrocatalysts is attracting more and more attention in recent years due to a global interest in developing techniques for electrochemical energy conversion and storage, as well as elelectro-synthesis of valuable chemicals. The activity is one of the key performance parameters for electrocatalysts, while the observed activity can be affected by mass loading of electrocatalysts. Here, we take cobalt oxide (Co3O4)/graphite paper electrode (Co3O4/GPE) as a model electrode to demon-strate how the mass loading of Co3O4 catalyst influences ethylene glycol (EG) oxidation in alkaline (KOH) by cyclic votammetry (CV) and chronopentiometry (CP) approaches. Analyses from redox peaks and double layer capacitances reveal that increasing the mass loading provided more electrochemical active sites. Increasing loading made a positive contribution to EG oxidation at the low oxidation potential, while less significant improvement at the high oxidation potential. The results will provide some insight for optimzing the mass loading of electrocatalysts for electrocatalysis of small organic molecules.

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    Investigation of Through-Hole Copper Electroplating with Methyl Orange as A Special Leveler
    Jia-Ying Xu, Shou-Xu Wang, Yuan-Zhang Su, Yong-Jie Du, Guo-Dong Qi, Wei He, Guo-Yun Zhou, Wei-Hua Zhang, Yao Tang, Yu-Yao Luo, Yuan-Ming Chen
    Journal of Electrochemistry    2022, 28 (7): 2213003-.   DOI: 10.13208/j.electrochem.2213003
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    Methyl Orange (MO) with two kinds of functional groups can act as both an accelerator and an inhibitor, which has been used as a special leveler to simplify the electroplating additive system in the through-hole (TH) copper electroplating experiments. In this work, the role of MO in TH electroplating is characterized by molecular dynamics simulations and quantum chemical calculations. It is suggested that MO can spontaneously flatten the copper surface and be well adsorbed on the cathode surface, which inhibit the copper electrodeposition on the cathode. Electrochemical behavior of MO was evaluated by galvanostatic measurements (GM) and cyclic voltammetry (CV) to confirm that MO hardly affects the potential due to its duel functions of depolarizing and polarizing effects from the molecular structure of sulfonic acid group and other groups to achieve the internal Cu2+ reduction acceleration and mass transfer inhibition. Throw power value of TH with the aspect ratio of 10:1 could reach 92.34% from the base plating solution bath with the additions of only EO/PO and MO. The study of MO could provide new ideas for the development of electroplating additive system.

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    Recent Advances in Electrochemical Kinetics Simulations and Their Applications in Pt-based Fuel Cells
    Ji-Li Li, Ye-Fei Li, Zhi-Pan Liu
    Journal of Electrochemistry    2022, 28 (2): 2108511-.   DOI: 10.13208/j.electrochem.210851
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    Theoretical simulations of electrocatalysis are vital for understanding the mechanism of the electrochemical process at the atomic level. It can help to reveal the in-situ structures of electrode surfaces and establish the microscopic mechanism of electrocatalysis, thereby solving the problems such as electrode oxidation and corrosion. However, there are still many problems in the theoretical electrochemical simulations, including the solvation effects, the electric double layer, and the structural transformation of electrodes. Here we review recent advances of theoretical methods in electrochemical modeling, in particular, the double reference approach, the periodic continuum solvation model based on the modified Poisson-Boltzmann equation (CM-MPB), and the stochastic surface walking method based on the machine learning potential energy surface (SSW-NN). The case studies of oxygen reduction reaction by using CM-MPB and SSW-NN are presented.

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    A Co Porphyrin with Electron-Withdrawing and Hydrophilic Substituents for Improved Electrocatalytic Oxygen Reduction
    Hong-Bo Guo, Ya-Ni Wang, Kai Guo, Hai-Tao Lei, Zuo-Zhong Liang, Xue-Peng Zhang, Rui Cao
    Journal of Electrochemistry    2022, 28 (9): 2214002-.   DOI: 10.13208/j.electrochem.2214002
    Abstract608)   HTML44)    PDF(pc) (1852KB)(534)       Save

    Understanding factors that influence the catalyst activity for oxygen reduction reaction (ORR) is essential for the rational design of efficient ORR catalysts. Regulating catalyst electronic structure is commonly used to fine-tune electrocatalytic ORR activity. However, modifying the hydrophilicity of catalysts has been rarely reported to improve ORR, which happens at the liquid/gas/solid interface. Herein, we report on two Co porphyrins, namely, NO2-CoP (Co complex of 5,10,15,20-tetrakis(4-nitrophenyl)porphyrin) and 5F-CoP (Co complex of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin), and their electrocatalytic ORR features. By simultaneously controlling the electronic structure and hydrophilic property of the meso-substituents, the NO2-CoP showed higher electrocatalytic activity than the 5F-CoP by shifting the ORR half-wave potential to the anodic direction by 60 mV. Compared with the 5F-CoP, the complex NO2-CoP was more hydrophilic. Theoretical calculations suggest that NO2-CoP is also more efficient than 5F-CoP to bind with an O2 molecule to form CoIII-O2·-. This work provides a simple but an effective strategy to improve ORR activity of Co porphyrins by using electron-withdrawing and hydrophilic substituents. This strategy will be also valuable for the design of other ORR molecular electrocatalysts.

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    Effect of Corrosion Inhibitors on Copper Etching to Form Thick Copper Line of PCB in Acidic Etching Solution
    Xiao-Li Wang, Wei He, Xian-Ming Chen, Hong Zeng, Yuan-Zhang Su, Chong Wang, Gao-Sheng Li, Ben-Xia Huang, Lei Feng, Gao Huang, Yuan-Ming Chen
    Journal of Electrochemistry    2022, 28 (7): 2213007-.   DOI: 10.13208/j.electrochem.2213007
    Abstract606)   HTML34)    PDF(pc) (1574KB)(401)       Save

    The chemical compounds of 2-mercaptobenzothiazole (2-MBT), benzotriazole (BTA) and phenoxyethanol (MSDS) as corrosion inhibitors were used to inhibit the copper etching to form the thick copper line of PCB in the acidic etching solution. The inhibition status was characterized with contact angle measurement, electrochemical test and etch factor calculation, while the corrosion morphology of copper surface was studied by scanning electron microscope. The adsorption mechanism of corrosion inhibitors on copper surface is analyzed by molecular dynamics and quantum chemistry calculations. The results indicated that the synergistic function of the two inhibitors could effectively promote their adsorption on the copper surface in parallel, while their adsorption energy could be higher than that of the single inhibitor. The etch factor of the thick copper line with about 33 μm in thickness increased to 6.59 from the etching solution with 2-MBT and MSDS for good agreement of PCB manufacture.

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