Journal of Electrochemistry

Table of Contents

2017, 23(3): 0.

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Organic ElectroChemistry（OEC） is an interdiscipline of Organic Chemistry and Electrochemical Technology. Compared with conventional chemical synthesis, organic electrosynthesis eliminates the utilization of toxic and / or dangerous redox reagents and proceeds under mild conditions with higher reaction selectivity, thereby has been widely used in synthesis of fine chemicals of drug, flavor, dyes and synthetic fibers. With the increasing concern of environmental problems, increasing attention has been paid to organic electrosynthesis. In the electrochemical oxidation and reduction processes, electron is used as a reagent to remove from and add to the substrates. Without utilization of stoichiometric chemical reagents and without generating the associated waste products, organic electrochemistry in nature is regarded as the “green and sustainable” chemistry.

Electrocarboxylation: an Effective Process for Fixation of CO₂ into Organic Carboxylic Acids

WANG Huan, LU Jia-xing

2017, 23(3): 250-261. doi:10.13208/j.electrochem.161041

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Conversion and utilization of greenhouse gas carbon dioxide (CO₂) have become more and more significant to the sustainable development of the global economy. Among them, electrocarboxylation of organic substrates is an effective process. Under mild conditions such as ambient temperature and pressure, carbocations generated by electroreduction of organic substrates can react with CO₂ into corresponding carboxylic acids. This paper introduces the recent progress of our group in electrochemical carboxylation, including electrocarboxylation of varies active organic substrates and asymmetric electrocarboxylation.

Research Progresses of α-C—H Bond Functionalizations under Electrochemical Conditions

QIAN Peng, BI Mei-xiang, WANG Yu-kang, ZHA Zheng-gen, WANG Zhi-yong

2017, 23(3): 262-275. doi:10.13208/j.electrochem.161052

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Recently, organic electrochemical synthesis has emerged as the most important and attractive method to construct carbon-carbon bond and carbon-heteroatom bonds in organic synthetic chemistry. This review mainly summarizes the electrochemical syntheses at present, especially focused on the recent progresses in our research group using an iodine radical as a mediator to promote α-C?H bond functionalization. The organic electrosynthesis provides an alternative approach and a new research direction in the development of green organic synthesis.

Selective Direct Electro-Oxidation of C-H Bond

Liao Yan-mei， Wu Qian-qian， Zhang An-lun，Zhu Ying-hong，Ma Chun-an

2017, 23(3): 276-282. doi:10.13208/j.electrochem.161046

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Carbon-hydrogen (C-H) bond is the most basic chemical bond in organic compounds. The activation and direct conversion of C-H bond are the effective methodology for synthesis of different kinds of organic compounds from alkane compounds. The oxidative activation and functionalization of C-H bonds constitute an important and challenging area of investigation. The electro-oxidative activation of C-H bonds to form new C-O, C-C and C-N bonds has proven to be interesting and important in organic chemistry using the clean electron as the oxidant. The target C-O, C-C and C-N compounds could be selectively achieved by choosing the appropriate electrode, supporting electrolyte and solvent, as well as reaction temperature via the constant current or constant potential electrolysis technology.

Wastewater Treatment Process Based on Microbial Electrochemistry: Opportunities and Challenges

HE Wei-hua, LIU Jia, WANG Hai-man, FENG Yu-jie

2017, 23(3): 283-296. doi:10.13208/j.electrochem.161054

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Microbial electrochemical technology (MET) has drawn great attention for its characteristics of synergetic pollution removal and energy recovery of wastewater. In the last decade, significant developments in microbial electrochemical system (MES) have been made in the aspects of electron transfer mechanism, microbial community analysis, function expansion, low-cost electrode materials and scaled-up constructions. However, the feasibility of MET as a wastewater treatment process has been controversial so far. In this paper, the characteristics of MET were systematically compared with anaerobic and aerobic processes from the application point of view in the aspects of pollution degradation and energy recovery processes. The MET-based water treatment technology revealed some comparative advantages for applications because of its low sludge yield rate, energy self-sufficiency operation and current-assisted pollutant removal capability. The better understanding of these advantages would be helpful in finding the proper application scope of MET for wastewater treatment. However, in the process of advancing the practical application of MET, challenges remained require more effort such as the construction simplification, development of low-cost material and maintenance of electrode performance in long-term operation. More considerations were also needed to determine the appropriate application position of MET in a series of water treatment units to overcome shortcomings and take advantages of technical advances.

Electrochemical Synthesis of Homoallylic Alcohols and Homoallylic Amines

ZHONG Wei-qiang, LIANG Xiang-hui, HUANG Jing-mei

2017, 23(3): 297-306. doi:10.13208/j.electrochem.161047

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Electrochemical technique has been widely applied in the organic synthesis. This review focuses on the electrochemical synthesis of homoallylic alcohols and homoallylic amines from the allylation of carbonyl compounds and imines. This method has been developed impressively, especially in the field of electrochemical allylation in a green solvent of aqueous media. Improvement of the efficiency of the electricity, regio-selectivity and chiral synthesis are expected.

Cathodic Electrochemiluminescence of Meso-tetra(4-sulfophenyl)porphyrin/Potassium Peroxydisulfate System

WANG Yan-feng, LUO Di, SHAN Duo-liang, LU Xiao-quan*

2017, 23(3): 307-315. doi:10.13208/j.electrochem.161042

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A new electrochemiluminescence (ECL) system in aqueous solution was constructed by using meso-tetra(4-sulfophenyl)porphyrin (TSPP) as a luminophoreand potassium peroxydisulfate (K2S2O8) as a reductive–oxidative coreactant. Upon sweeping from 0 V to -1.5 V, two cathodic ECL peaks were found simultaneously. One appeared at -0.8 V, which is corresponding to the reduction of TSPP, another at -1.2 V, that is attributed to the reduction of K2S2O8. And methylene blue could quench the ECL of TSPP effectively. In accordance with the linearity between quenching efficiency and the concentration of methylene blue, a method to determine methylene blue was established. The ECL mechanism was also studied through a series of experiments.

Characteristics and Mechanism for the Simons Electrochemical Fluorination of Methanesulfonyl Fluoride

XU Wen-lin, LI Bao-tong, WANG Da-wei, WANG Ya-qiong

2017, 23(3): 316-321. doi:10.13208/j.electrochem.161043

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The characteristics and mechanism for the Simons electrochemical fluorination processes were investigated during the electrochemical fluorination of CH₃SO₂F to CF₃SO₂F. The results showed that the reaction mechanism for the electrochemical fluorination of organic compounds to organic fluorides was the same as that of chemical fluorination processes using fluorinating agents such as CoF₃. The electrochemical fluorination in anhydrous HF was a heterogeneous process, and nickel fluorides on the surface of the nickel anode played the role of a mediator in the Simons process to transfer oxidation potential from the anode to the substrate and fluorine from HF to the organic substance. Nickel fluorides were formed electrochemically on the surface of the nickel anode by oxidation of Ni in anhydrous HF to a high valence (with the oxidation stage more than +2) nickel fluorides. The fluorinating agents in electrochemical fluorination processes were NiF_n（n≥3）, high valences of nickel produced at the anode, which is much more reactivie than CoF₃ and instable under the experimental conditions. The decomposion of NiFn to F2 would take place, and NiF_ncould also react with organic fluoride. Because F₂ is a strong fluorinating agent, NiF_ncould be decomposed into low molecular weight organic compounds fluorinated products, leading to low current efficiency in process yield and by-products. Therefore, an effective method to improve the process is by increasing the molar ration of organic matter to NiF_n on the anode/electrolyte interface.

Ionic Liquid-Supported TEMPO/Polymeric Ionic-liquid/Carbon Black Ternary Composites: Preparations and Applications in Electrochemical Oxidation of Alcohols

LIN Xin, SUN Cao-cao,LIU Zhi-rong, ZENG Cheng-chu

2017, 23(3): 322-326. doi:10.13208/j.electrochem.161051

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To effectively recover redox catalyst and supporting electrolyte, a novel ternary composite consisting of ionic liquid-supported TEMPO, polymeric ionic-liquid and carbon black was prepared. The ionic-liquid supported redox catalyst TEMPO-IL-BF₄was firstly synthesized from 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, and followed by the reaction of polydimethyldiallylammonium chloride (PDDA) and bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) to form poly[diallyldimethylammonium bis(trifluoromethanesulfonyl)imide] (PDDA(Tf₂N)). A combination of the above mentioned two synthesized materials and carbon black afforded to obtain the ternary composite, which was used as the recoverable supporting electrolyte and mediator for the electrochemical oxidation of alcohol. The results indicate that various alcohols could be oxidized efficiently to the corresponding aldehydes or ketones with the more than 80% yields in the presence of the ternary composite under electrochemical conditions. In addition, the composite could be recovered with 95% recovery after being used for 4 times in experiments. The development of the ternary composite provides an efficient and sustainable approach for the recovery of supporting electrolyte and redox catalyst.

Preparations and Applications of IrSnOx Electrode in Electrochemical Synthesis of 2,5-dichlorophenol

MA Xiang-yu, TU Xu-guo, HE Rui-nan, CHEN Ya, ZHU Gui-sheng, SHAO Shou-yan, CHEN Song

2017, 23(3): 327-331. doi:10.13208/j.electrochem.161050

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The electrodes of titanium based iridium tin oxides (IrSnOx) have been prepared by traditional thermal decomposition method and further applied to the electrosynthsis of 2,5-dichlorophenol in order to explore a green and high efficient synthesis route. The results showed that the electrode surface existed apparent cracks, while the intermediate layer prepared with Sn:Sb=94:6 existed less cracks and longer life time. The main products of the electrolytic reaction were 2,5-dichlorophenol, p-chlorophenol, and 1,2,4-trichlorobenzene. The electrosynthsis yield of 2,5-dichlorophenol reached 57% and the selectivity of 2,5-dichlorophenol was as high as 93% by using the IrSnOx as an anode, which is obviously better than those obtained by using the commercial chlorine evolution electrode, oxygen evolution electrode and Pt electrode as anodes. The selectivity of 89%, 27%, 87% and the yields of 30%, 15%, 49% were obtained by the commercial chlorine evolution electrode, oxygen evolution electrode and Pt electrode, respectively. The excellent electrocatalytic oxidation performance of the IrSnOx electrode was achieved.

Electrochemical Deposition of Cr from Cr³⁺ in the Mixed Electrolyte of [BMIM]OAc/H₂O

LUO Wei, NIU Dong-fang, DU Rong-bin, WANG Jun-wei, WANG Zhu-qing, XU Heng, ZHANG Xin-sheng

2017, 23(3): 332-339. doi:10.13208/j.electrochem.161053

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The electrochemical reduction of trivalent chromium ion (Cr³⁺) to Cr in 1-butyl-3-methylimidazolium acetate ([BMIM]OAc)-H₂O mixed electrolyte was investigated. The cyclic voltammograms showed that the electroreduction of Cr³⁺ in the mixed electrolyte occurred in a two-step process, namely, Cr³⁺+ e → Cr²⁺ and Cr²⁺+ 2e→ Cr⁰, controlled by the diffusion of Cr³⁺to the electrode. The diffusion coefficient of Cr³⁺ was 1.2×10^-8cm²/s at 40 ℃ obtained by Rendle-Sevcik equation. The chronoamperomograms of the Cr³⁺electrodeposition confirmed the three-dimensional instantaneous nucleation mechanism of Cr. The XRD and SEM characterizations on the Cr coating after calcining in argon atmosphere at 600℃ revealed that the coating was composed of Cr and chromium oxide (Cr₂O₃) nanoparticles with an average particle size of 0.48 μm. The elements of Cr and O were obviously detected from the coating obtained at 40℃ and -3.0V by EDX and the mass fraction of Cr reached 83.8%. Comparison in the qualities of coating layers prepared by Cr electrodepositions in [BMIM]OAc, [BMIM]BF₄and [BMIM]PF₆ electrolytes indicated that the OAc^- was presented in favor of Cr³⁺ reduction.

Preparations and Characterizations of Ti/PbO₂ Electrodes Modified with Rare Earth of Praseodymium and PVP in Electrochemical Degradation of Organics

XU Mai, WANG Feng-wu, LIANG Xian, WEI Yi-jun, FANG Wen-yan, ZHU Chuan-Gao, HUN Yun-hu

2017, 23(3): 340-346. doi:10.13208/j.electrochem.161048

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The titanium (Ti) based lead oxide (PbO₂) electrodes doped with praseodymium oxide (Pr₂O₃) and polyvinylpyrrolidone (PVP) were prepared by electrodeposition. The surface morphologies and structures of the as-prepared thin films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) technique, respectively. The results showed that the denser and more uniform coatings with smaller particles and larger surfaces were obtained by doping, which modified the micro-structure of the Ti/SnO₂-Sb₂O₃/Pr₂O₃-PVP-PbO₂electrode. Cyclic voltammetry (CV) was also used to study the electrocatalytic activity of electrodes and higher oxidation capacity was obtained with the Ti/SnO₂-Sb₂O₃/Pr₂O₃-PVP-PbO₂electrode. The accelerated life of Ti/SnO₂-Sb₂O₃/Pr₂O₃-PVP-PbO₂ electrode was considerably longer than that of undoped anode. Compared with conventional Ti/PbO₂ electrodes, the Ti/SnO₂-Sb₂O₃/Pr₂O₃-PVP-PbO₂ electrodes exhibited higher decolorization rate and removal rate of COD, reaching 99% and 87.9%, respectively, after the electrolysis time of 120 min during the process of degrading simulative dyeing wastewater of methylene blue. The good electrocatalytic performance of Ti/SnO₂-Sb₂O₃/Pr₂O₃-PVP-PbO₂makes it a promising anode for treatment of organic pollutants in aqueous solutions.

Study on the Electrochemical Redox Mechanism of Emodin

LI Dan, JIN Bao-kang

2017, 23(3): 347-355. doi:10.13208/j.electrochem.161045

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The electrochemical reduction of emodin (Q) has been investigated in acetonitrile by cyclic voltammetry (CV), IR spectroelectrochemistry cyclic voltabsorptometry (CVA) and derivative cyclic voltabsorptometry (DCVA) techniques. It was found that anion radical Q^•− interacted with neutral Q to form dimer Q₂^•− which was further reduced to Q₂²⁻ at more negative potentials. A two-step one-electron process involving electrochemical reductions of Q₂²⁻ to form Q₂³⁻ in the first step and Q₂⁴⁻ in the second step, corresponding to the two cathodic peaks of C₃ and C₄ in CV curves was confirmed. When the scan range was between 1.0 and -2.0 V, there were two new anodic peaks (A₁, A₂) formed at more positive potentials. When the scan range was 0.3~-1.4 V, the current value of A₂ increased with the added scan cycles, indicating that Q₂^•− accumulated in the solution. The C₁ and C₂ peaks still appeared in the second and third scans in CV curves under the consecutive scans from 1.0 to -2.0 V, suggesting the regainer of Q after each potential cycle. And Q₂^•− would be oxidized to Q at the potential corresponding to A₁. As a result, the electrochemical redox mechanism of emodin has been proposed.

Electrocatalysis of NanoTin Dioxide in the Battery Reaction of Zinc-Nitrobenzene

TU Xu-guo, MA Xiang-yu, HE Rui-nan, WANG Xiao-juan, LING Chen, SUN Yun-xia, CHEN Song

2017, 23(3): 356-363. doi:10.13208/j.electrochem.161049

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The tin dioxide (SnO₂) nanoparticles were synthesized by using a simple hydrothermal route in the presence of tetrapropyl ammonium bromide (TPAB) as a surfactant. Accordingly, the titanium mesh based SnO₂ catalyst electrode was prepared. The morphologies and structures of SnO₂ nanostructures were characterized by scanning electron microscopy and X-ray diffraction spectrometry. The influences of reactant concentration, reaction temperature and time on the morphology of the products were investigated in detail. The electrocatalytic performance of SnO₂ for the reduction of nitrobenzene with zinc was studied. Possible formation process and growth mechanism for such hierarchical SnO₂ nanostructures have been proposed based on the experimental results. The results showed　that when the concentration of NaOH was 0.5 mol•L^-1, the hydrothermal reaction temperature was 160 ℃, hydrothermal reaction time was 9 h, the as-prepared SnO₂ catalyst appeared thorny spheric particles consisting of nanosheets with the particle size as small as 17 nm. Compared with Pt electrode, the catalyst electrode exhibited higher catalytic activity toward the electrochemical reduction of nitrobenzene. The conversion rate of nitrobenzene was up to 74% and the maximum discharge power density was 21.9 mW•cm^-2, which are much better than those with platinum electrode. The main reduction products of nitrobenzene were aniline, p-phenetidine and p-chloroaniline.