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Cyclic Voltammetry Coupled with Faradic Adsorption/Desorption Processes: A Finite Element Simulation
No full text法拉第吸脱附偶联过程的电化学行为较为复杂,难以定量获得其表界面反应动力学信息. 本文通过COMSOL有限元软件对法拉第吸脱附偶联过程的循环伏安行为进行数值分析,研究了反应物或产物不同吸附条件下的循环伏安行为. 结果表明：当反应物或产物弱吸附时,可通过阴、阳极峰电流之差实现饱和吸附量的定量表征. 随着吸附平衡常数的增大,反应由弱吸附向强吸附过渡,峰电流由扩散峰与吸脱附峰相互重叠过渡到相互分离的吸脱附“前波”或“后波”特征. 该吸脱附特征峰的形状和位置与电势依赖的吸附平衡常数有关. 吸附平衡常数及其电势依赖程度越大,吸脱附峰偏离扩散峰越远,吸脱附峰越尖锐. 该模型为法拉第吸脱附偶联过程的循环伏安研究提供了一种定量研究方法,能够帮助研究者从复杂的吸脱附伏安行为中定量获得饱和吸附量和吸附平衡常数等信息,并对涉及吸脱附的电催化研究具有一定指导意义.Heterogeneous electron transfer (HET) coupled with Faradic adsorption/desorption is the fundamental processes involved in hydrogen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, and methanol oxidation reaction. However, the electrochemical behaviors of HET coupled with Faradic adsorption/desorption are complicated, and difficult to get the interface reaction kinetics quantitatively. In this paper, finite element method was adopted to simulate the cyclic voltammetric behaviors of HET coupled with Faradic adsorption/desorption processes by using the Fick’s second law and Langmuir isotherm. The cyclic voltammograms when reactant or product adsorbed weakly or strongly were simulated, and they agreed well with the classical results. In addition, taking the reactant adsorption for example, the effects of scanning rate, saturated adsorption and adsorption equilibrium constant on cyclic voltammograms were investigated. The simulation demonstrates that weak adsorption can be magnified with the increasing scanning rate, and the peak current changes gradually from being proportional to the square root of scanning rate to being proportional to the scanning rate. The difference between anodic and cathodic peak currents is linearly related to saturated adsorption. Therefore, the quantitative characterization of saturated adsorption is realized by correlating the difference between anodic and cathodic peak currents to the saturated adsorption. With the increasing adsorption equilibrium constant, the weak adsorption transfers to strong adsorption, and the adsorption/desorption peaks separate from diffusion peaks to form prepeaks or postpeaks. The potential-dependent adsorption equilibrium constant was also simulated, which demonstrates that it can further change the shape and position of adsorption/desorption peaks. The quantitative method based on this model can help researchers to obtain saturated adsorption and adsorption equilibrium constant quantitatively from the cyclic voltammograms coupled with Faradic adsorption/desorption processes. The simulation can also help researchers to understand the different cyclic voltammetric behaviors between surface processes and diffusion processes, and would be constructive for the study of electrocatalysis involving adsorption/desorption processes.国家自然科学基金项目(51605404);湖南省自然科学基金项目(2018JJ3142);湖南科技大学博士科研启动基金(E51792);湖南省大学生研究性学习和创新性实验计划(No.201710534030)通讯作者:张杰E-mail:[email protected]:ZHANGJieE-mail:[email protected]. 湖南科技大学化学化工学院,湖南省普通高校化学与化工创新创业教育中心,湖南 湘潭 4112012. 固体表面物理化学国家重点实验室,厦门大学化学化工学院,福建 厦门 3610051. Chemistry and Chemical Engineering Innovation and Entrepreneurship Education Center of Hunan Province, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan, 411201, Hunan, China2. Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, Chin
Direct Carbon Solid Oxide Fuel Cells
No full text碳是重要的能量载体. 直接碳固体氧化物燃料电池（DC-SOFC）是一种直接使用固体碳为燃料的能量转换装置,通过电化学反应,DC-SOFC可将碳所蕴含的化学能直接而连续地转换成电能,转换效率高,产生的CO2浓度高,易于捕集和后续处理. 本文系统地介绍DC-SOFC的结构组成、工作原理、研究现状和发展趋势,重点介绍了作者课题组在DC-SOFC研究方面的成果和进展,包括单电池和电池组的研制、采用生物质碳和煤炭为燃料时的性能和DC-SOFC在气电联产中的应用探索.Carbon is richly reserved in coal, biomasses, and many other nature resources. It is usually used as an energy source through oxygen oxidation reaction. The oxidation is generally realized through combustion which causes serious air pollution. Besides, the conversion efficiency of generating electricity through the combustion process is limited by Carnot efficiency. A direct carbon solid oxide fuel cell (DC-SOFC) is a solid oxide fuel cell (SOFC) directly operated with solid carbon as the fuel. It can convert the chemical energy of carbon into electricity with high efficiency. The concentration of produced CO2 from a DC-SOFC is so high that enables easy capture and segregation of CO2. Here we systematically introduce the configuration, reaction process, research and development status, and prospects of DC-SOFC. Especially, we give a comprehensive review concerning research progress in DC-SOFC, including development and fabrication of single cells and stacks, DC-SOFC operating with biomass char and coal as the fuel, and gas-electricity cogeneration using DC-SOFC.国家自然科学基金项目(No.91745203);国家自然科学基金项目(No.U1601207);广东省引进创新团队项目(No.2014ZT05N200)通讯作者:刘江E-mail:[email protected]:LIUJiangE-mail:[email protected]华南理工大学,环境与能源学院, 广东 广州 510006School of Environment and Energy, South China University of Technology, Guangzhou 510006, Chin
Electrochemical Oxidation of Metal Chromium in odium Hydroxide Aqueous Solution
No full text铬铁电氧化溶出技术是一种全新的制备铬酸钠的方法,具有反应条件温和、过程可控、工艺环保等优点,然而金属铬在NaOH水溶液中的电化学氧化过程尚不明确. 本文采用循环伏安法（CV）和阳极极化法（LSV）对金属铬在NaOH水溶液中的电化学氧化过程进行研究. 使用EDS、SEM、XRD和XPS对电解前后的金属铬表征,判断中间物的产生,使用紫外可见分光光度计验证电解液中生成了铬酸钠. 结果表明,金属铬和中间产物Cr(OH)3可能依次发生电化学氧化直接生成Na2CrO4,阳极极化为金属铬的活化. 随着NaOH溶液浓度的增加,Cr(OH)3和Na2CrO4的生成量在增加,金属铬电化学氧化制备铬酸钠的适宜条件为碱浓度≥ 2 mol·L-1,阳极电势≥ 1.6 V（vs. SCE）.Ferrochrome electrolysis technology is a novel method for preparing sodium chromate (Na2CrO4). Although the method performs well at soft reaction conditions, controllable process, environmentally friendly production process, etc., the electrochemical oxidation process of metal chromium in NaOH aqueous electrolyte is still unclear. At present, there are few research articles about specific electrochemical oxidation of metal chromium in NaOH aqueous electrolyte. It is, therefore, meaningful to carry out the research in electrochemical oxidation mechanism of chromium. The electrochemical oxidation of metal chromium in 0.01 mol·L-1 ~ 10 mol·L-1 NaOH aqueous electrolytes at 20 °C was studied by cyclic voltammetry (CV, Scan rate: 100 mV·s-1) and linear sweep voltammetry (LSV, Scan rate: 1 mV·s-1) through controlling the potential range. The working electrode (WE) was a chromium rod, the counter electrode (CE) was a platinum sheet, and the reference electrode (RE) was a saturated calomel electrode (SCE). EDS, SEM, XRD and XPS were used to characterize the metal chromium before and after the electrolysis to determine intermediate during electrochemical oxidation. Ultraviolet-visible (UV) spectrophotometer was used to analyze the electrolyte solution after the electrolysis to confirm the formation of Na2CrO4. The results indicated that Cr(0) and Cr(OH)3 might undergo electrochemical oxidations in sequence to directly form Na2CrO4. When the anode potential was negative, chromium generated Cr(OH)3 film through electrochemical oxidation, while hydroxide ions (OH-) underwent electrochemical oxidation to form oxygen. On the othere hand, when the anode potential was positive, two electrochemical reactions: (1) Cr(0) → Cr(VI); (2) Cr(OH)3 → Cr(VI) took place. Thus, the anodic polarization included activation of Cr(0). The dissolution reaction of chromium was stimulated by OH- at a higher concentration of NaOH aqueous solution. Futhremore, the amounts of Cr(OH)3 and Na2CrO4 formed were increased with the increased concentration of NaOH aqueous solutions. At the same time, a large amount of oxygen was deposited on the anode electrode surface with the alkaline concentration ≥ 2 mol·L-1 and anodic potential ≥ 1.6 V (vs. SCE).青海省科技厅基础研究项目（No.2017-ZJ-786）和青海省重大科技专项（No.2016-GX-A10）资助通讯作者:冯海涛E-mail:[email protected]:FENGHai-taoE-mail:[email protected]. 中国科学院青海盐湖研究所,中国科学院盐湖资源综合高效利用重点实验室,西宁 8100082. 青海省盐湖资源开发工程技术研究中心,西宁 8100083. 中国科学院大学,北京 1000491. Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China2. Qinghai Engineering and Technology Research Center of Salt Lake Resources Development, Xining 810008, China3. University of Chinese Academy of Sciences, Beijing 100049, Chin
Electrolyte Tailoring for Electrocatalytic Reduction of Stable Molecules
No full text本文概述了惰性小分子电催化还原反应（如二氧化碳还原反应和氮气还原反应）中电解液的组成和作用机制,介绍了相关电解液研究的最新进展,并讨论了电解液调控在揭示反应机理、改善催化性能中的重要作用.Reduction of stable molecules such as CO2 and N2 is important process in electrochemical energy conversion and storage technologies for electrofuels production. However, for the inert nature of CO2/N2 molecule and competitive proton reduction in conventional aqueous electrolytes, selective electrochemical carbon/nitrogen fixation suffers from high overpotential, low reaction rate and low selectivity. While addressing these issues has witnessed substantial advances in electrocatalysts, much less attention has been placed on the electrolytes, which play an important role in regulating the local environment and thus the performance of catalysts under operating conditions. Rational design of electrolytes has received increasing interest to boost the activity and selectivity of stable molecule electrocatalysis. In this review, we overview recent progress in mechanistic understanding and strategies development in tailoring electrolytes for electrocatalytic CO2 and N2 reduction. We highlight the ion effect, local environment, and interface structure of electrocatalysts and electrolytes based on experimental and computational studies on representative examples. Particular discussion is provided on the effect of local pH modulation, electrolyte concentrating, selective ionic adsorption and nonaqueous electrolyte.国家自然科学基金项目(21925503);国家自然科学基金项目(21871149);国家重点研发计划纳米科技专项(2017YFA0206700);中央高校基本科研业务费专项资金项目资助通讯作者:程方益E-mail:[email protected]:CHENGFang-yiE-mail:[email protected]南开大学化学学院,先进能源材料化学教育部重点实验室,新能源转化与存储交叉科学中心,天津 300071Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center (ReCast), College of Chemistry, Nankai University, Tianjin 300071, Chin
Electrochemical Carbon Dioxide Reduction in Flow Cells
No full text采用电化学方法将二氧化碳（CO2）还原转化为基础化学品或碳基燃料是目前极具前景的碳资源利用新方式. 考虑到该技术未来的发展方向和大规模应用需求,人们亟需开发具有高转化效率和高稳定性的电解设备. 在本文中,作者详细介绍了现阶段发展的两种流动池的结构特点及性能优势,阐述了每种反应体系的内在局限性, 深入分析了整个反应体系所用组件（电解池、气体扩散电极、离子交换膜）对于性能的影响. 最后,针对目前该领域存在的挑战及未来发展趋势进行了总结与展望.Electrochemical carbon dioxide reduction (CO2RR) is an appealing approach to convert atmospheric CO2 to value-added fuels and industrial chemicals, and may play an important role during the transition to a carbon-neutral economy. In order to make this technology commercially viable, it is essential to pursue CO2RR in flow reactors instead of conventional H-type reactors, and to combine electrocatalyst development with system engineering. In this review, we overview the cell configurations and performance advantages of the two types of flow reactors, analyze their shortcomings, and discuss the effects of their different components including gas diffusion electrode and ion exchange membrane. A brief perspective is offered at the end for the possible future research directions in this emerging field.国家科技部基金项目(2017YFA0204800);国家自然科学基金项目资助(2190020225)通讯作者:韩娜,李彦光E-mail:[email protected];[email protected]:HANNa,LIYan-guangE-mail:[email protected];[email protected]苏州大学功能纳米与软物质研究院,江苏 苏州 215123Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, Jiangsu, Chin
Regulation and Criminal Punishment of Internet Financial Behavior
No full text时延安，中国人民大学法学院教授、博士生导师，法学博士；中国人民大学刑事法律科学研究中心特聘研究员。【中文摘要】对互联网金融犯罪的治理，应当通过确立合理有效的行政规制和必要的刑事惩罚来实施。互联网金融行为具有“互联网风险+金融风险”这种风险叠加的特点，因而应采取比传统金融规制更为严格的规制方式。对互联网金融犯罪的认定，应从违反行政规制的角度界定其非法性，同时应结合行政规制和风险的视角区分互联网金融领域的行政违法与犯罪。在司法实践中，应摈弃“刑事规制”的思路，避免刑事法制对市场经济活动进行过度的干预。
【Abstract】Internet financial crimes should be governed by establishing reasonable and effective administrative regulations and necessary criminal sanctions. Internet finance has the characteristic of “Internet risk plus financial risk”，resulting in a superimposed risk. Therefore，regulations on Internet finance should be more stringent than regulations on traditional finance. Internet financial crimes should be defined as “illegality” from the perspective of violating administrative regulations. Meanwhile，administrative violations and crimes in Internet finance should be distinguished from the perspective of administrative regulations and risks. In practice，the idea of “criminal regulations” should be discarded to avoid excessive intervention by the criminal legal system in market economic activities.国家社会科学基金重大项目“网络金融犯罪的综合治理”（17ZDA148
Ties matter: Improving efficiency in course allocation by allowing ties
No full text李梦玲的论文在多对多匹配的框架下研究课程分配问题，主要考虑到学生对于选修课程有弱偏好。从理论的角度，文章提出了两种稳定且帕累托有效的匹配机制。从实践的角度，基于大学的实际选课数据，该论文借助这些提出的匹配机制并且通过反事实校准揭示了允许学生显示弱偏好可以显著提高匹配效率。此外，在随机环境中的进一步数值模拟再次证实了论文结论的一般性。
李梦玲，新加坡南洋理工大学博士，现为厦门大学经济学院经济学系与WISE双聘副教授。主要研究领域为博弈论、市场设计、行为与实验经济学等。主持国家自然科学基金青年项目以及教育部人文社会科学研究青年项目各1项。【Abstract】This paper studies course allocation as a multi-unit allocation problem with weak pref- erences under a homogeneous and weak priority structure. While ties are widespread in students’ preferences, most existing mechanisms either restrict students to rank courses in strict orderings or break ties in reported preferences as part of the mechanism, which leads to efficiency loss. To take weak preferences into account, we propose two new com- peting mechanisms, referred as the Pareto-improving draft and dictatorship mechanisms. Both mechanisms are stable and Pareto efficient, and the latter is strategyproof for stu- dents. With these proposed mechanisms, we document substantial efficiency improvement by allowing ties in preference revelation in a counterfactual calibration based on course allocation data at Nanyang Technological University in Singapore. Further numerical simu- lations in a random environment reconfirm our findings.This research is supported by the National Natural Science Foundation of China (grant number 71703132) and the Ministry of Education of China (grant number 17YJC790074)
Facile Synthesis of Nitrogen-Doped Graphene-Like Active Carbon Materials for High Performance Lithium-Sulfur Battery
Get PDF锂硫电池由于具有较高的理论容量被视为一种最具发展潜力的储能装置. 然而,硫的利用率较低及循环寿命短等问题限制着其商业化进程. 本文通过一种简单易行的方法将三聚氰胺（C3H6N6）和L半胱氨酸(C3H7NO2S)碳化,制备出一种氮掺杂类石墨烯活性碳材料（NGC）. 该材料的类石墨烯结构能够有效抑制锂硫电池在充放电过程中产生的体积效应,以此提升其循环性能. 不仅如此,材料中含有的含氮官能团还可以促进离子转移,抑制多硫化物的溶解,进而提升硫的利用率. 其中,制备出的NGC-8/PS复合电极用于锂硫电池时在0.2 C的电流密度下初始容量为1164.1 mAh·g-1,在经过400圈的充放电循环之后依然具有909.4 mAh·g-1的比容量,每圈容量衰减仅为0.05%,甚至在2C的电流密度下也能达到820 mAh·g-1的高比容量.Lithium-sulphur (Li-S) battery is regarded as a promising energy storage device because of its high theoretical capacity. However, the low S utilization and short cycling life limit the commercial applications. In this work, nitrogen-doped graphene-like carbon (NGC) materials were synthesized by simply pyrolyzing and carbonizing the mixture of melamine (C3H6N6) and L-cysteine (C3H7NO2S). The graphene-like structure in NGC effectively buffered the volume change of S during the discharge/charge process and improved the cycling stability. Meanwhile, nitrogen-containing functional groups in NGC facilitated the transportation of ions and suppressed the dissolution of polysulphide (PS), enabling a high utilization of S. As expected, the NGC-8 (the mass ratio of melamine and L-cysteine being 8:1)/PS cathode delivered a high initial discharge capacity of 1164.1 mAh·g-1 at 0.2 C and still retained 909.4 mAh·g-1 capacity after 400 cycles with a slow capacity decay rate of 0.05% per cycle. Even at as high as 2 C, a high-rate capacity of 820 mAh·g-1 could be achieved.通讯作者:李长明E-mail:[email protected]:LIChang-mingE-mail:[email protected].西南大学材料与能源学院,洁净能源和先进材料研究所,重庆 4007152.苏州科技大学材料科学与工程学院,江苏 苏州 2150093.青岛大学生命科学学院,先进跨学科科学研究所,山东 青岛,2660711. Institute for Clean Energy & Advanced Materials, School of Materials and Energy, Southwest University, Chongqing 400715, P.R. China;2. Institute for Materials Science & Devices, School of Materials Science and Engineering, Suzhou University of Science & Technology, Suzhou 215009, P.R. China;3. Institute for Advanced Cross-field Sciences, College of Life Science, Qingdao University, Qingdao 266071, P.R. Chin
Pitting Behaviors of Passivated and Trans-Passivated 304 Stainless Steel
No full text为了进一步了解不锈钢钝化膜与过钝化膜的性质,本文对比研究了在不同电位下极化处理后304不锈钢样品的点蚀及表面膜性质,发现空白对照组样品的点蚀电位和1.1 V过钝化处理后样品的点蚀电位相近,而0.5 V钝化处理后样品的点蚀电位较高. 扫描Kelvin探针（SKP）实验结果也验证了这一现象. 扫描电子显微镜（SEM）结果显示,空白对照组样品表面只呈现一般样品抛光后形貌;0.5 V钝化处理后的样品表面被颗粒状钝化膜所覆盖,该膜层决定了样品具有较好的耐蚀性;而1.1 V过钝化处理后的样品表面出现裂缝,导致不锈钢基体继续发生严重的局部腐蚀,可能成为过钝化膜保护性变差的主要原因.In order to further understand the passivation and trans-passivation behaviors of 304 stainless steels, the samples were pretreated under different polarization potentials and their corrosion behaviors were investigated. It was found that the pitting potential of the untreated sample was the same as that of the sample treated with 1.1 V trans-passivation potential, while the pitting potential of the sample treated with 0.5 V passivation treatment was the highest. This observation was further verified by the SKP results. According to SEM observations, the surface of the untreated sample preserved a polishing morphology, while the surface of the 0.5 V passivation treated sample was covered by a passivation film decorated with small corrosion particles, performing good corrosion resistance. However, cracks appeared on the surface of the 1.1 V trans-passivation treated sample, leading to severe localized corrosion of the matrix and resulting in the deterioration of the trans-passivation film.国家自然科学基金项目资助No(51671163);国家自然科学基金项目资助No(51731008)通讯作者:宋光铃E-mail:[email protected]:SONGGuang-lingE-mail:[email protected]. 厦门大学材料学院,海洋材料腐蚀与防护中心,福建 厦门3610052. 厦门大学固体表面物理化学国家重点实验室,福建 厦门3610051. Center for Marine Materials Corrosion and Protection, College of Materials, Xiamen University, Xiamen 361005, Fujian, China2. State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen 361005, Fujian, Chin
Preparations and Properties of Low Cost Sulfide Solid Electrolytes Li6-xPS5-xClx
No full text硫化物固体电解质以其室温电导率高,热稳定性好,电化学窗口宽等特点,在高功率及室温固态电池方面优势突出,是极具潜力的固态电解质材料. 但制备其所需的高纯度Li2S原料高昂的价格使其实际应用受到掣肘,故本文使用单质锂金属（99.9%）、升华硫、氯化锂和五硫化二磷等低成本原料,采用球磨法和高温热处理制备得到了Li6-xPS5-xClx（x = 0.5）固态电解质粉末,通过X射线衍射（XRD）、拉曼（Raman）、扫描电子显微镜（SEM）及能谱仪（EDS）对Li6-xPS5-xClx（x = 0.5）固态电解质进行了表征,并使用交流阻抗法测试了其电导率,电导率可达8.29×10 -4 S·cm -1,将Li6-xPS5-xClx（x = 0.5）固态电解质粉末进行冷压制片,制成Li对Li半电池后显示了良好的循环性能.With the shortage of energy and environmental pollution, the storage of electric energy is getting more attention all over the world. In order to improve the energy density and safety performance of batteries, uses of solid electrolyte become more and more popular. However, because the conductivity of solid electrolyte is not comparable to that of liquid electrolyte, the solid electrolyte application has certain limitations. With the efforts of researchers from various countries, there are several different solid electrolytes having better conductivity, for instance, sulfide solid electrolyte and oxide solid electrolyte. Sulfide solid electrolyte is a highly promising solid electrolyte material because of its high room temperature conductivity, good thermal stability and wide electrochemical window. It has outstanding advantages in high power and normal temperature solid state batteries. However, the application of expensive Li2S raw materials required high-purity has been hampered. In this paper, Li6-xPS5-xClx (x = 0.5) solid electrolyte was prepared by ball milling using low-cost raw materials such as elemental lithium metal (99.9%), sublimed sulfur (CP), P2S5 (AR) and LiCl (AR). The as-prepared Li6-xPS5-xClx solid electrolyte powder was characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), and the cold-pressed Li6-xPS5-xClx tablets were tested for cycle performance and electrical conductivity in Li6-xPS5-xClx/Li half-cell. The results showed that through the pressure-free sintering at 550 oC, the total lithium-ion conductivity of the solid electrolyte at room temperature was 8.29×10 -4 S·cm -1, making commercialization of solid-state batteries possible.国家重点研发计划No(2016YFB0300801);国家自然科学基金重大科研仪器设备研制专项资助No(51327902)通讯作者:陈康华E-mail:[email protected]:CHENKang-huaE-mail:[email protected]. 中南大学粉末冶金研究院,湖南 长沙 4100832. 中南大学粉末冶金国家重点实验室,湖南 长沙 4100833. 中南大学轻合金研究院,湖南 长沙 4100831. State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China2. National Key Laboratory of Science and Technology for National Defence on High-strength Structural Materials, Central South University, Changsha 410083, China3. Light Metal Research Institute, Central South University, Changsha 410083, Chin