有机电极材料固定化策略

有机电极材料因其理论比容量高、低成本、环境友好以及分子结构可设计性强等特点,有望成为下一代可持续和多功能能量储存设备的有效电极材料。然而,根据“相似相溶”原理,该类材料极易溶解在有机电解液中,导致电池容量衰减快、循环稳定性和倍率性能也较差。目前已有许多研究致力于通过“固定化”过程解决有机电极材料的溶解问题。本综述针对有机电极材料的固定化策略展开评述,介绍了有机电极材料的固定化机理,以及各种固定化策略在不同种类有机电极材料中所起的作用,指出了有机电极材料面临的挑战,并对未来的研究和改进方向进行展望。     

膜电极构型CO2还原电解单池的稳定性研究

电化学还原CO₂可实现CO₂的资源化转化,是缓解因其过度排放所导致诸多环境问题的关键技术. 本文提出了一种膜电极（membrane electrode assembly,MEA）构型CO₂还原电解单池的结构设计,可同步实现气体扩散阴极两侧CO₂的供给与电解质液层的更新. 基于该MEA构型电解池,实验考察了电解质液层中KHCO₃浓度和更新与否对氮掺杂石墨烯锚定的Ni电极表面CO₂电还原制备CO的反应活性、产物分布与稳定性的影响. 结果表明,若电流密度低于5 mA·cm^-2,KHCO₃浓度显著影响电解电势而非产物分布. CO₂还原电解单池在稳定运行中存在着“可逆”与“不可逆”两种衰减模式. 其中,阴极/电解质界面处催化剂的流失是 “不可逆”衰减形成的原因;而电解质液层中KHCO₃溶液的流失导致了MEA构型CO₂还原单池的“可逆”衰减,周期性更新KHCO₃电解质是降低其“可逆”衰减的有效方法.     

单晶电极界面反应过程的电化学原位拉曼光谱研究

自20世纪70年代起,人们利用原位光谱技术（拉曼、红外等）对电化学界面进行了系统的研究,进而发展出原位谱学电化学的研究方向,由于其具有良好的表面灵敏度和能量分辨率,可以提供更多的表面反应信息,进而从微观上揭示反应机理. 伴随着纳米技术的兴起,表面增强拉曼光谱技术取得了快速的发展. 近来,壳层隔绝纳米粒子增强拉曼光谱（shell-isolated nanoparticle-enhanced Raman spectroscopy,SHINERS）技术更是得到人们的广泛关注. SHINERS的出现为研究单晶模型电极上的催化反应提供了一种非常好的原位光谱技术. 本文主要对原位电化学SHINERS技术在单晶电极界面研究的具体应用及其发展前景进行相关论述.     

基于非贵金属氧还原催化剂的质子交换膜燃料电池性能

质子交换膜燃料电池的成本和寿命问题是制约其商业化的主要瓶颈. 开发高效稳定的新型非铂氧还原催化剂是降低电池成本的重要途径. 过渡金属-氮-碳型非贵金属催化剂具有较高催化活性、资源丰富、价格低廉等优点, 被认为是未来最有希望替代铂的氧还原催化剂. 本综述从催化剂的设计构筑、催化层结构优化以及电池测试等方面, 对过渡金属-氮-碳型非贵金属催化剂的国内外最新研究进展进行了重点讨论, 并对未来其发展趋势提出展望.     

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.     

Observations and theories of quantum effects in proton transfer electrode processes

Quantum tunneling effects play an important role in a variety of chemical reactions considerably affecting the reaction rates via opening the classically forbidden paths and emerging as highly efficient or selective processes. However, in the case of electrochemical reactions, quantum tunneling effects are less investigated due to complicated nature of chemical interactions at the electrified interfaces. In this review, we summarize the experimental/theoretical concept of electrochemical quantum proton tunneling (EQPT), which is a key element in microscopic electrode processes. First, we review the experimental observations of EQPT, and next, we discuss possible theoretical pictures of the process. This review shows that a combination of a wide spectrum of scientific efforts is required to understand microscopic mechanism of EQPT including development of the precise electrochemistry-oriented experimental techniques and methodologies, formulation of the appropriate theoretical models for specific systems, and performance of the advanced computational simulations.     

Effect of Ionic Liquid Structure on the Electrochemical Response of Dopamine at Room Temperature Ionic Liquid‐modified Carbon Paste Electrodes (IL–CPE)

In this work 12 different ionic liquids (ILs) have been used added as co‐binders in the preparation of modified carbon paste electrodes (IL–CPEs) used for the voltammetric analysis of dopamine in Britton‐Robinson buffer. The ionic liquids studied were selected based on three main criteria: (1) increasing chain length of alkyl substituents (studying 1‐ethylimidazolium and ethyl, propyl, butyl, hexyl and decylmethylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids); (2) nature of the counter ion (dicyanamide, bis(trifluoromethylsulfonyl)imide and hexafluorophosphate) in 1‐butyl‐3‐methylimidazolium ionic liquids; and (3) cation ring structures (1‐butyl‐3‐methylimidazolium, 1‐butyl‐1‐methylpiperidinium, 1‐butyl‐1‐methylpyrrolidinium and 1‐butyl‐3‐methylpyridinium) in bis(trifluoromethylsulfonyl)imide or hexafluorophosphate (1‐butyl‐3‐methylimidazolium or 1‐butyl‐3‐methylpyridinium as cations) ionic liquids. The use of IL as co‐binders in IL–CPE results in a general enhancement of both the sensitivity and the reversibility of dopamine oxidation. In square wave voltammetry experiments, the peak current increased up to a 400 % when 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide was used as co‐binder, as compared to the response found with the unmodified CPE. Experimental data provide evidence that electrostatic and steric effects are the most important ones vis‐à‐vis these electrocatalytic effects on the anodic oxidation of dopamine on IL–CPE. The relative hydrophilicity of dicyanamide anions reduced the electrocatalytic effects of the corresponding ionic liquids, while the use of 1‐ethyl‐3‐methylimidazolium hexafluorophosphate or 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (two relatively small and highly hydrophobic ionic liquids) as co‐binders in IL–CPE resulted in the highest electrocatalytic activity among all of the IL–CPE studied.     

Natural Melanin Nanoparticle‐decorated Screen‐printed Carbon Electrode: Performance Test for Amperometric Determination of Hexavalent Chromium as Model Trace

A biosensor was prepared with natural melanin nanoparticles (MNP) decorated on a screen‐printed carbon electrode (SPCE). Hexavalent chromium was selected as a well‐known heavy metal ion to be detected for testing the performance of novel biosensor. Natural MNP was extracted from cuttlefish (Sepia officinalis) ink. Surface decoration of SPCEs with MNP was performed by two different methods. The first one was layer‐by‐layer assembly (LBL‐A) for different cycle times(n). In the second one, plasma treatment of SPCE incorporated with evaporation‐induced self‐assembly (EI‐SA) techniques including different incubation times in MNP solutions. The performance of both modified SPCEs were tested for amperometric detection of Cr(VI) in various water samples, and peak reduction of Cr(VI) was determined at 0.33 V. Amperometric results showed wide linear ranges of 0.1–2 μM and 0.1–5 μM of Cr(VI) for SPCEs modified with 14n‐LBL‐A and 12h‐EI‐SA, respectively. The sensitivities of SPCEs modified with 14n‐LBL‐A and 12h‐EI‐SA techniques were 0.27 μA μM^?1 and 0.52 μA μM^?1, respectively. In addition, both modified SPCEs selectively detected Cr(VI) in a model aqueous system composed of certain other heavy metals and minerals, and tap and lake water samples. The LOD and LOQ values for 12h‐EI‐SA were 0.03 μM and 0.1 μM, respectively. This showed that MNP‐modified‐SPCEs generated via EI‐SA techniques have the potential to be an alternative to conventional detection methods such as ICP‐MS.     

In situ Growth of a Cobalt‐based Metal‐organic Framework on Multi‐walled Carbon Nanotubes for Simultaneously Detection of Hydroquinone and Catechol.

In the present study, we report a facile method for preparing a porous MWCNTs/ZIF‐67 nanocomposite with the help of a morphology‐maintained ZIF‐67 in situ growth on multi‐walled carbon nanotubes. Interesting, the MWCNTs/ZIF‐67 nanocomposite demonstrated excellent electrochemical activity for hydroquinone (HQ) and catechol (CC) attribute to the effective interconnections ZIF‐67 crystals and MWCNTs. The analytical curves for HQ and CC obtained by differential pulse voltammetry (DPV) were linear in the range from 0.5 to 100 μM. Benefitting from the excellent conductivity of MWCNTs as well as the high surface area and porosity of ZIF‐67, the advanced nanocomposite displayed good reproducibility, high selectivity and excellent stability, and was successfully employed to assay the content of dihydroxybenzene isomers in the lake water samples.