Papers by Keyword: Electrochemical Reduction

Abstract: The direct electrochemical reduction of solid titanium dioxide (TiO₂) is conducted in [BMIM]BF₄-CaCl₂ ionic liquid (IL) at 100 °C using sintered TiO₂ as cathode and graphite rod as anode at an electrolysis potential of 3.2 V. Cyclic voltammetry is used to investigate the mechanism and feasibility of the direct electrochemical reduction of solid TiO₂ in [BMIM]BF₄-CaCl₂ IL at 100 °C. The surface morphologies of the cathode are examined by scanning electron microscopy（SEM）. The crystal phase structure of the cathode is examined using a D8 Advance X-ray diffractometer(XRD). The results indicate that the direct electrochemical reduction of solid TiO₂ in [BMIM]BF₄-CaCl₂ IL is feasible. A significant increase in conductivity is obtained by doping graphite into the cathode, thereby enhancing deoxidation. TiO₂ reduction is conducted step by step, from outside to inside, and from high to low valence variation.

Abstract: Electrochemical reduction of carbon dioxide (CO₂) to useful organic compounds is of great significance to decrease CO₂ emission. The electrochemical reduction of CO₂ is carried out in acetonitrile with tetrabutylammonium perchlorate as the electrolyte on a stainless steel cathode in a single cell; by using a sacrificial zinc anode, the product is zinc oxalate when the cathode potential is between 2.5 V and 3.5 V vs. Ag rod electrode. When the potential is less than 3.5 V, acetonitrile is decomposed, and the product is mainly zinc cyanide; when it is higher than 2.5 V, the main product is a basic zinc carbonate. Therefore, only when the cathode potential is in a proper range can CO₂ molecule obtain an electron and dimerize to form C₂O₄², which combines Zn²⁺ from the anode to form zinc oxalate.

Abstract: The Au electrode plated nanostructure Pd was used to study the reaction mechanism of C.I. reactive blue 19 and reactive brilliant blue K-GR with atomic hydrogen in 0.2M H2SO4 solution by the electrochemical method. The nanostructured Pd/Au electrode showed the various forms of hydrogen. Through the result of cyclic voltammetry, Tafel curve and EIS, the protonation of dye molecule could accelerate the production of atomic hydrogen and the adsorption of dye on Pd/Au electrode. The decolorization efficiency using potentiostatic polarization at -0.18V was highest than that at other polarization potential because the proportion between adsorbed dye and adsorbed atomic hydrogen on electode was optimum.

Abstract: The present paper studies the removal of the nitrogen in the form of nitrate in water by electrochemical catalysis reduction. The influence of electrode materials and various test conditions on the removal efficiency was studied. The experimental results show that the removal rate of nitrate can reach above 90% by using a three-dimensional permeable electrode of Fe-Si alloy under the condition of flowrate of 600ml/h, current density of 10mA/cm² and reaction time of 2h.

Abstract: The FFC-Cambridge process is a molten salt electrochemical deoxidation method that was invented at the Department of Materials Science and Metallurgy of the University of Cambridge one decade ago. It is a generic technology that allows the direct conversion of metal oxides into the corresponding metals through cathodic polarisation of the oxide in a molten salt electrolyte based on calcium chloride. The process is rather universal in its applicability, and numerous studies on metals, semimetals, alloys and intermetallics have since been performed at the place of its invention and worldwide. The electro-winning of titanium metal is a particularly rewarding target because of the disadvantages of the existing extraction methods. This article summarises the research work performed on the FFC-Cambridge process at the University of Cambridge and its industrial partners with a focus on the electro-winning of titanium metal from titanium dioxide. Topics addressed encompass the invention of the process, early proof-of-concept work, the identification of the reaction pathway, and the investigation and optimisation of the key process parameters. Also discussed are aspects of technology transfer and some of the development work undertaken to date.

Abstract: The cathodic reduction of SiO2 in KCl-CaCl2-NaCl-MgCl2 melt was studied using tungsten wires as working electrodes. The results of cyclic voltammetry
square wave voltammetry and chronopotentiometry showed that the cathodic deposition of silicon is a quasi-reversible diffusion-controlled reaction, followed by a four electrons transfer step. The results of current reversal chronopotentiometry and thermodynamic data showed that both the silicon deposition and the side reaction between SiO2 and magnesium result in the loss of magnesium and low current efficiency. A 35.2% current efficiency was obtained with the content of SiO2 0.2% at 700 .

Abstract: Synthesis of iron nanopowder by room-temperature electrochemical reduction process of α-Fe2O3 nanopowder was investigated in terms of phase evolution and microstructure. As process variables, reduction time and applied voltage were changed in the range of 1~20 h and 30~40 V, respectively. From XRD analyses, it was found that volume of Fe phase increased with increasing reduction time and applied voltage, respectively. The crystallite size of Fe phase in all powder samples was less than 30 nm, implying that particle growth was inhibited by the reaction at room temperature. Based on the distinct equilibrium shape of crystalline particle, phase composition of nanoparticles was identified by TEM observation.

Abstract: It is known that anthraquinone derivatives act as aqueous sulphide oxidation catalysts, so the redox chemistry of the compound anthraquinone 2,7-disulphonate (AQ27DS) stimulated our interest, as reported here. AQ27DS was reduced in aqueous solution at pH 9.0 to give a deep red coloured air-sensitive solution. Cyclic voltammetry and exhaustive electrolysis indicated that the anthraquinone was reversibly reduced in a two electron, one proton process at a variety of electrode surfaces. From limiting current results at a rotating disc electrode, the diffusion coefficient of AQ27DS was calculated to be 3.37 x 10-10 m2 s-1. Spectroscopic results confirmed that AQ27DSH- was the major reduced species, but also indicated that the di-anion (AQ27DS2-) and radical species AQ27DS• were also present. ESR spectroscopy showed that the radical was formed via a comproportionation reaction between the di-anion and the AQ27DS starting material. The peak separation from voltammetry enabled the comproportionation constant (Kc) to be estimated, and it was found to be in the range of 0.4 to 4.

Abstract: This work has attempted to find a new low temperature reduction process for fabrication of Cu nanopowder from fine CuO powder. For this purpose, we used electrochemical reduction method which is conducted in an electrolyte of NaCl aqueous solution at room temperature. It was found that ball-milled CuO powder (particle size ~100 nm and grain size ~40 nm) was completely reduced under the conditions of 20 V power, 0.5 mol NaCl solution and 2 h reaction time, producing Cu nanopowder (particle size ~80 nm and crystallite size ~25 nm). Simultaneously, we observed that sintering of nanopowders occurred during the reduction process, leading to agglomeration of nanopowder. Based upon the experimental results, the correlation between electrochemical reduction process and its related powder characteristics was discussed in terms of material transport.