Catalytic reduction of U(VI) to U(IV) using hydrogen with platinum loaded on alumina and silica

During the reprocessing of spent nuclear fuel, uranium (U) and plutonium (Pu) are together extracted by employing tri-n-butyl phosphate (TBP)/dodecane mixture and their partitioning is achieved by adding uranous nitrate. The partitioning agent, uranous is conventionally produced by the electrolytic reduction of uranyl nitrate. An alternate route for the reduction of U from (VI) to (IV) using hydrogen (H₂) as reductant was developed using platinum (Pt) based catalyst. Improvements in the development of the catalyst have been carried out in order to reduce the requirement of Pt without affecting the reduction performance. Experiments using 2 wt% Pt loaded on alumina beads and alumina powder have been performed and results are discussed. As the catalyst supported on alumina was found to be unstable in acidic environment, Pt loaded on silica powder has also been developed. Pt loaded on alumina and silica substrates have been tried to envisage the reduction behaviour using H₂ as reductant in presence of hydrazine nitrate which acts as U(IV) stabiliser as well as reductant. Parametric studies have been carried out to optimise the process parameters namely pressure, temperature, U concentration, free acidity, hydrazine concentration and catalyst to U (C/U) ratio. 2 wt% Pt loaded on silica has been selected for further scale up studies for making uranous.     

A novel method for measuring the effective conductivity and the contact resistance of porous electrodes for lithium-ion batteries

The performance of a porous electrode is strongly related to its electrical properties, such as the effective conductivity of the coating and the contact resistance between the coating and the current collector. This work presents a new method to measure both the effective conductivity and the contact resistance with a single measurement. No preparation is necessary for this, other than cutting a disk shaped electrode and measuring the thickness of the coating. The method is applied to three different cathodes and an anode as a proof of concept.     

Condition optimization of amperometric determination of chemical oxygen demand using boron-doped diamond sensor

The amperometric determination of chemical oxygen demand (COD) reported by Quan Xie??s group (Electrochem Commun 9:2281, 14), was a rapid, green and simple COD evaluation method. This work focused on testing and verifying this method by using a home-made boron-doped diamond (BDD) film as anode and optimizing the experiment conditions. The BDD thin film electrode was employed as anode and the electrochemical process was run with different experimental parameters including counter electrode, electrode gap, applied potential, electrolyte pH, and temperature. Standard samples were determined in the optimum conditions, a linear range of 19.2?C11,600?mg l^?1 COD and a low detection limit of 0.192?mg l^?1 COD were well established with the present approach. The COD value of the simulated organic wastewater determined by this method agreed well with the standard dichromate method, and it showed good accuracy, stability, and reproducibility.     

Effects of solid polymer electrolyte coating on the composition and morphology of the solid electrolyte interphase on Sn anodes

In order to discuss the effect of polymer coating layer on the Sn anode, the composition and morphology of the solid electrolyte interphase (SEI) film on the surface of Sn and Sn@PEO anode materials have been investigated. Compared with the bare cycled Sn electrode, the SEI on the surface of cycled Sn@PEO electrode is thinner, smoother, and more stable. Therefore, the Sn@PEO nanoparticles can basically keep the original appearance during cycling. Based on the results obtained from X-ray photoelectron spectroscopy (XPS), the SEI formed on the Sn@PEO electrode is characterized by inorganic components (Li₂CO₃)-rich outer layer and organic components-rich inner which could make the SEI more stable and inhibit the electrolyte immerging into the active materials. In particular, the elastic ion-conductive polyethylene oxide (PEO) coating could increase the toughness of SEI and allow the SEI to endure the stress variation in repetitive lithium insertion and extraction process. As a result, the Sn@PEO electrodes show significantly better capacity retention than bare Sn electrodes. The findings can serve as the theoretical foundation for the design of lithium-ion battery electrode with high energy density and long cycle life.     

Efficient uranous nitrate production using membrane electrolysis

Electrochemical reduction of uranyl nitrate is a green, simple way to make uranous ion. In order to improve the ratio of uranous ion to the total uranium and maintain high current efficiency, an electrolyser with very thin cathodic and anodic compartment, which were separated by a cation exchange membrane, was setup, and its performance was tested. The effects of various parameters on the reduction were also evaluated. The results show that the apparatus is quite positive. It runs well with 120 mA/cm² current density (72 cm² cathode, constant current batch operation). U(IV) yield can achieve 93.1 % (500 mL feed, total uranium 199 g/L) after 180 min electrolysis. It was also shown that when U(IV) yield was below 80 %, very high current efficiency was maintained, and there was almost a linear relationship between uranous ion yield and electrolysis time; under the range of experimental conditions, the concentration of uranyl nitrate, hydrazine, and nitric acid had little effect on the reduction.     

Examination of wet coating and co-sintering technologies for micro-SOFCs fabrication

Preparation conditions to obtain a dense electrolyte layer on a micro-tubular electrode support were investigated using wet coating and subsequent co-firing techniques. An anode-supported micro-tubular SOFC with 1.5 mm diameter was successfully fabricated by careful control of the co-sintering process of electrolyte/anode support laminates. The densification of the electrolyte layer deposited on the support surface was greatly affected by the shrinkage of tubular support during the co-sintering process. Support shrinkage above 15% was found to produce a fully densified electrolyte layer on the anode support. In contrast, the use of an anode support with shrinkage below 10% constrained gadolinium-doped ceria (GDC) sintering, resulting in a poorly densified GDC microstructure. Finally, we obtained a micro-tubular cell composed of a dense GDC and a porous (La,Sr)(Co,Fe)O₃–GDC multi-layered structure on a NiO–GDC micro-tubular anode support. The cell, with a dense and ≈15 μm thick GDC electrolyte layer, was electrochemically evaluated in a temperature range from 450 to 550 °C. This micro-tubular cell with an electrode length of 6.3 mm showed a power density above 0.1, 0.2 and 0.4 W/cm² at 450, 500 and 550 °C, respectively, in wet H₂ fuel flow.     

Enhancing the performances of Li-ion batteries by carbon-coating: present and future

With progress of knowledge of electrode materials, it has been found that their surface structures are of great importance to the electrochemical performance of Li-ion batteries. Carbon coating can effectively increase the electrode conductivity, improve the surface chemistry of the active material, and protect the electrode from direct contact with electrolyte, leading to enhanced cycle life of the batteries. Carbon coating together with nanotechnology provides good conductivity as well as fast Li-ion diffusion, and thus also results in good rate capabilities. The recent development of carbon coating techniques in lithium-ion batteries is discussed with detailed examples of typical cathode and anode materials. The limitation of current technology and future perspective of the new concept of "hybrid coating" are also pointed out.     

g-C3N4-TiO2光催化电极耦合生物产电阳极还原硝酸根

以g-C₃N₄-TiO₂为光催化阴极,耦合生物阳极进行光催化还原硝酸盐研究。考察了空穴清除剂、曝气条件、生物阳极对光催化还原硝酸盐的影响,并对还原机理进行分析。结果表明在曝氮气、有生物阳极时硝酸盐去除效果最好,空穴清除剂对硝酸盐还原影响较小。反应210 min后硝酸盐去除率为72.57%,副产物亚硝酸盐浓度为0.31 mg·L^-1,氨氮未检出。经重复实验后,负载的催化剂不脱落,催化剂活性基本不变,可重复使用。     

g-C_3N_4-TiO_2光催化电极耦合生物产电阳极还原硝酸根

以g-C_3N_4-TiO_2为光催化阴极,耦合生物阳极进行光催化还原硝酸盐研究。考察了空穴清除剂、曝气条件、生物阳极对光催化还原硝酸盐的影响,并对还原机理进行分析。结果表明在曝氮气、有生物阳极时硝酸盐去除效果最好,空穴清除剂对硝酸盐还原影响较小。反应210 min后硝酸盐去除率为72.57%,副产物亚硝酸盐浓度为0.31 mg·L~(-1),氨氮未检出。经重复实验后,负载的催化剂不脱落,催化剂活性基本不变,可重复使用。     

Nanoporous gold electrode prepared from gold compact disk as the anode for the microbial fuel cell

The electrodes (anode and cathode) have an important role in the efficiency of a microbial fuel cell (MFC), as they can determine the rate of charge transfer in an electrochemical process. In this study, nanoporous gold electrode, prepared from commercially available gold-made compact disk, is utilized as the anode in a two-chamber MFC. The performance of nanoporous gold electrode in the MFC is compared with that of gold film, carbon felt and acid-heat-treated carbon felt electrodes which are usually employed as the anode in the MFCs. Electrochemical surface area of nanoporous gold electrode exhibits a 7.96-fold increase rather than gold film electrode. Scanning electron microscopy analysis also indicates the homogeneous biofilm is formed on the surface of nanoporous gold electrode, while the biofilm formed at the surface of acid-heat-treated carbon felt electrode shows rough structure. Electrochemical studies show although modifications applied on carbon felt electrodes improve its performance, nanoporous gold electrode, due to its structure and better electrochemical properties, acts more efficiently as the MFC’s anode. The maximum power density produced by nanoporous gold anode is 4.71 mW m^?2 at current density of 16.00 mA m^?2, while this value for acid-heat-treated carbon felt anode is 3.551 mW m^?2 at current density of 9.58 mA m^?2.     

Lithium Germanate (Li2GeO3): A High‐Performance Anode Material for Lithium‐Ion Batteries

A simple, cost‐effective, and easily scalable molten salt method for the preparation of Li₂GeO₃ as a new type of high‐performance anode for lithium‐ion batteries is reported. The Li₂GeO₃ exhibits a unique porous architecture consisting of micrometer‐sized clusters (secondary particles) composed of numerous nanoparticles (primary particles) and can be used directly without further carbon coating which is a common exercise for most electrode materials. The new anode displays superior cycling stability with a retained charge capacity of 725 mAh g^?1 after 300 cycles at 50 mA g^?1. The electrode also offers excellent rate capability with a capacity recovery of 810 mAh g^?1 (94 % retention) after 35 cycles of ascending steps of current in the range of 25–800 mA g^?1 and finally back to 25 mA g^?1. This work emphasizes the importance of exploring new electrode materials without carbon coating as carbon‐coated materials demonstrate several drawbacks in full devices. Therefore, this study provides a method and a new type of anode with high reversibility and long cycle stability.     

Low-cost SiO-based anode using green binders for lithium ion batteries

The influence of environmentally friendly aqueous binders and carbon coating on the electrochemical performance of SiO powder anodes for lithium ion batteries has been investigated in detail. The SiO anode with sodium alginate (Alg), styrene butadiene rubber/sodium carboxymethyl cellulose (SCMC) or polyacrylic acid binder exhibits fairly good cycling stability. However, use of polyvinyl alcohol as binder results in rapid capacity loss during cycling. The positive effect of the former binders could be attributed to the amorphous structures and ester-like bond, which were detected by X-ray diffraction and Fourier transform infrared. The cycling performance is further enhanced by carbon coating on the surface of the SiO. The reversible capacity of SiO/C electrode with either Alg or SCMC can retain ca. 940 mAh g^?1 after 100 cycles. In particular, a long-term cycling stability can be achieved for SiO/C electrode using SCMC binder. Additionally, the high irreversibility of SiO/C electrode at the first cycle can be completely compensated by a simple pretreatment.     

Self-accelerating chlorine evolution on porous anodes of finite thickness

Operation of a finite-thickness porous electrode under the chlorine evolution conditions is analyzed in the framework of the convective diffusion model. According to calculations, the gas evolution in the anode’s porous coating is a necessary but insufficient condition for the self-acceleration of the electrode process. Despite the gas evolution process in the anode pores, the anodic process on the low-activity electrodes decelerates, which is externally manifested in an increased Tafel slope of the polarization curve as compared with that for a smooth electrode. Self-acceleration of the anodic chlorine evolution takes place only on electrodes with true exchange currents in excess of 10^-4 A cm^-2. Externally, the self-acceleration effect manifests itself in the emergence of a low-polarizability portion in the high-current region of the polarization curve. Such a different effect of the gas evolution process on the chlorine reaction kinetics at porous electrodes of different catalytic activity is due to an altered balance between the diffusive and convective current constituents in the overall process rate following a change in the exchange current for either electrode.     

Gd_(0.2)Ce_(0.8)O_2包覆固体氧化物燃料电池Ni-ScSZ复合阳极制备及性能表征

应用双层流延法制备Ni-ScSZ阳极支撑体-ScSZ电解质复合膜素坯,经共烧结得到复合膜.以硝酸铈和硝酸钆为原料,柠檬酸作燃料,由燃烧合成法制备Gd0.2Ce0.8O2(GDC)包覆的Ni-ScSZ阳极.X-射线衍射(XRD)和电子显微镜(TEM和SEM)分析显示,Ni-ScSZ阳极颗粒表面的包覆层是由直径小于100 nm的GDC微粒构成,并与Ni-ScSZ阳极颗粒紧密烧结在一起.实验表明,2.0%(by mass)GDC包覆的Ni-ScSZ阳极具有较佳的性能,以其组装的单电池在850℃用H2或CH4作燃料的最大功率密度分别是825和848 mW/cm2,而由无包覆的Ni-ScSZ作阳极的单电池,功率密度分别是584和586 mW/cm2.由两种阳极材料组装的单电池,分别在700℃于CH4气氛下作长时间发电实验,发现2.0%(by mass)GDC包覆的Ni-ScSZ阳极比Ni-ScSZ阳极具有较好的抗碳沉积性能.     

Titration of Potentiometric NH4VO3, KH2PO4, K2HPO4, and their Mixture in Molten NaNO3 at 350°C Using a Novel Solid‐State Glass/TiO2 pH Indicator Electrode

A solid‐state Glass/TiO₂ electrode was fabricated using a transparent conductive titanium oxide film on a glass substrate. The coating of the glass substrate was achieved by a novel simple chemical vapor deposition (CVD) procedure. This electrode can be used as an indicator electrode in potentiometric acid‐base titration. This electrode behaves reversibly and responds to the oxide ion concentration in molten nitrate. NH₄VO₃, KH₂PO₄, K₂HPO₄, and their mixture were titrated with Na₂O₂ at 350°C using the glass/TiO₂ electrode in molten NaNO₃.     

High-efficiency ozone generation via electrochemical oxidation of water using Ti anode coated with Ni–Sb–SnO<Subscript>2</Subscript>

Ozone (O₃) has been generated on Ni–Sb–SnO₂/Ti electrode as anode immersed in acidic media at 25 °C by electrochemical process. The anode was electrochemically characterized by cyclic voltammetry and morphologically characterized by scanning electron microscopy (SEM) and X-ray diffraction. The concentration of dissolved ozone was determined by a UV/Vis spectrophotometer. The type of electrode with different times coating on the titanium mesh and different acid type and various concentrations (C _acid) were used, and the stability of the electrode was investigated under the experimental conditions by SEM images. Results shows that higher efficiency (53.7%) for O₃ generation by electrochemical oxidation of water were obtained in HClO₄ (1 M) and an applied potential of 2.4 V vs. Ag/AgCl in 150 ml volume undivided electrochemical cell.     

The mosaic structure design to improve the anchoring strength of SiOx@C@Graphite anode

Silicon oxide (SiO_x)-based anodes have aroused great interest as the most promising alternative anode in the practical application of high-performance lithium-ion batteries. However, the electrochemical performance is inhibited because of the large volume change, and the electrode structure deteriorates during the cycling process, which hinders their practical application. In this article, a novel fabrication method for the synthesis of high-performance SiO_x@C@Graphite composites is presented. SiO_x particles are anchored on the graphite surface by chemical vapor deposition and compression molding. This structure makes up the shortcomings of poor electrical conductivity and poor bonding strength between SiO_x and graphite particles. It is beneficial to form a stable solid electrolyte interface and helps to maintain the structural integrity of electrode materials. As a result, the synthetic SiO_x@C@Graphite anode shows a high reversible capacity (2698.8 mA h), excellent cycle stability (about 76.9% capacity retention for 500 cycles) and a superior rate ability. Our research hopes to provide a new idea for improving the bonding strength of the surface coating.     

烟气吸收液中亚硝酸铵的电化学氧化处理技术

为实现燃煤电厂烟气脱硫、硝和汞一体化工艺中吸收液副产物亚硝酸铵的废物利用,采用电化学氧化处理技术将吸收液中亚硝酸铵转化为硝酸铵. 采用极化曲线、循环伏安曲线和恒电流法等多种电化学测试方法评价和选取电极材料,探讨电解液组成的影响,得到优化的电化学氧化工艺参数,并用化学分析法验证了电化学氧化处理效果.     

Metal-organic frameworks derived carbon-coated ZnSe/Co0.85Se@N-doped carbon microcuboid as an advanced anode material for sodium-ion batteries

Transition metal selenides attract significant attention as advanced anode materials for sodium-ion batteries（SIBs） in recent years due to their appropriate working potential and high theoretic capacity. However, the poor structural stability and rate capability limit their further practical applications. Herein,zeolite imidazole framework-8/zeolite imidazole framework-67 is used as a template to prepare Co_0.85Se and Zn Se nanoparticles embed in N-doped carbon matrix successfully, and...     

新型复合电极与偶氮染料分子的氧化降解反应的研究

介绍了具有合成H_2O_2和光催化性能的双功能型复合电极、双功能复合电极是 将TiO_2/C光催化剂负载在具有合成H_2O_2性能的新型载体上形成的。在光反应器 中,复合电极作阴极,钌-钛不溶性电极作阳极,低压汞灯作光源,实现了光化学 氧化与光催化氧化在同一电极/溶液界面上的联合作用。当反应器工作时,复合电 极中的TiO_2/C光催化层表面进行着光催化反应,在载体的三相界面上进行着O_2的 2电子H_2O_2的电化学反应,电流效率达82%（J = 15 mA/cm~2）,为·OH自由基的 生成提供了物质源,而且氧的2电子还原反应电位使其表面的TiO_2获得相对于平带 电位约+0.5 V的阳极偏压,改善了TiO_2的光催化活性。实验结果表明,复合电极 对提高偶氮染料分子活性艳红（K-2BP）的氧化降解速度起了重要作用。实验发现 偶氮染料分子在复合电极表面的吸附量与反应速度密切相关。文中讨论了复合电极 的作用原理及偶氮染料分子的氧化降解过程。