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Preparation and Electrochemical Characteristics of Titanium-supported NanoAg, Ag-Ni and Ag-Cu Electrodes

Author: LiLei
Tutor: YiQingFeng
School: Hunan University of Science and Technology
Course: Applied Chemistry
Keywords: Silver electrode Hydrothermal method Titanium substrate Hydrazine hydrate Sodium borohydride Nickel silver bimetallic Bimetallic silver and copper
CLC: O646.54
Type: Master's thesis
Year: 2009
Downloads: 280
Quote: 0
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Abstract


Hydrazine hydrate is an important chemical raw material, has a wide range of applications in the industrial production of pesticides. It is also an ideal raw material of the fuel cell, this is mainly because the hydrazine hydrate in the reaction does not produce CO 2 of greenhouse gases, the reaction, it produces very low overpotential, and this The cell has a high theoretical decomposition voltage of 1.56v; addition, studies show that the hydrazine hydrate in the electrochemical oxidation process does not suffer from poisoning effect. However, hydrazine hydrate is also considered to be a carcinogen and neurotoxin, which will cause great harm to the health of the human body, especially the liver and brain damage. Electrochemical research methods as a reliable and sensitive means of research, it can be the mechanism and kinetics of the oxidation of hydrazine hydrate research and detection of hydrazine hydrate. Therefore, the search for the electrochemical oxidation of hydrazine hydrate has good catalytic activity of the catalyst and its carrier has important research value. Sodium borohydride is a stable, non-flammable, easy to deal with non-toxic chemicals. Also direct borohydride fuel cell materials, direct borohydride fuel cell has a high theoretical in capacity (5.7Ahg -1 ), and relatively negative balance potentials (-1.24VvsSHE,) and in Many of the metal surface faster reaction speed, has been attached great importance to many domestic and foreign research workers. But using direct borohydride fuel cell is also needed to overcome the problem of borohydride hydrolysis reaction occurs at the surface of the catalytic material itself, which would reduce the release of energy and to reduce the utilization of the borohydride. Therefore, there is a need to find a suitable material for the anode, it has to have a good catalytic activity, the sodium borohydride, but also to reduce the hydrolysis of the sodium borohydride. The main work of this thesis is: hydrazine hydrate, polyethylene glycol as the reductant approximation nanometer-size metal particles are deposited on a titanium substrate by hydrothermal method, thereby preparing a novel titanium-based silver series electrically catalyst (Ag / Ti, AgNi / Ti, AgCu / Ti), they show a high electrocatalytic activity of the oxidation reaction of hydrazine hydrate and sodium borohydride. A comparative study was titanium base silver electrode catalytic oxidation performance by electrochemical test methods to arrive at the higher catalytic performance, better stability of the electrode catalyst. In addition, the use of electrochemical deposition technique, directly never a low concentration of the supporting electrolyte of AgNO 3 and Cu (NO , 3 ) 2 mixed solution, In the bi-metal is deposited on the surface of a titanium sheet having a dendritic structure and Ag-Cu nanoparticles, and the ultra-low concentration of hydrazine were detected. The main content of the paper and the following conclusions: the the silver electrode application and research progress overview elaborated the electric catalytic mechanism of the oxidation of hydrazine hydrate and sodium borohydride, catalyst nano is the catalyst for the research and development of the main ideas. 2. Determine the specific process for the preparation of titanium-based silver electrode series. Hydrazine hydrate and polyethylene glycol as a reducing agent in the present study, EDTA as additive Hydrothermal Synthesis of Ag / Ti, AgNi / Ti, AgCu / Ti electrode. The main characteristics of this process is: the metal catalyst can be provided to the nano-size particles are directly deposited on the surface of the titanium substrate, which step is completed the preparation of the type of electrode material, not only the process is simple, and the catalyst particles is stable. Electrodeposition Preparation of the titanium-based dendritic silver and copper particles, its main feature is that the preparation method and the process is simple, and the special structure of the catalyst particle, and stable performance. Using scanning electron microscopy (SEM) and energy dispersive analysis (EDS) testing technology, prepared Ag / Ti, AgNi / Ti, AgCu / Ti electrode morphology, structure and composition were characterized and analyzed. The main conclusions of the study are as follows: (1) Ag / Ti electrode of SEM and EDS image display, uniform size of silver metal spherical small particles deposited on the surface of the titanium base, about the size of 200 ~~ 300 nm, and the spherical particles are mutually connected, is formed three-dimensional network structure, has a huge surface area. (2) AgNi / Ti electrode of SEM and EDS image display, the surface of the titanium-based silver nickel deposited uniformly sized spherical metal particles and the spherical small particles are closely connected to each other the form of a porous net-like structure, the size of about 100 to 250nm, The more dense sphere connected, forming a porous structure having a large active sites. (3) AgCu / Ti electrode of SEM and EDS image display, is deposited at the surface of the titanium base were the shape of a small ball-like particles, the metal particles have a diameter of approximately of 500 ~~ 800nm. SEM and EDS image display (4) Electrodeposition AgCu / Ti electrode, rendered the surface of the titanium-based nanostructure similar branches shape, length of approximately 100 ~ 110nm, the foliage top was stamens core structure, this structure greatly increases the specific surface area . 4. Using cyclic voltammetry and potential step method, sodium hydroxide alkaline medium in Ag / Ti, AgNi / Ti the Electrocatalytic Oxidation process hydrazine hydrate AgCu / Ti electrode, and the electrode process dynamics analysis, and also studied Ag / Ti electrode electro-catalytic oxidation reaction of sodium borohydride, as well as the detection of hydrazine hydrate in the electrodeposition of silver on the copper electrode. The main conclusions are as follows: (1) voltage characteristics show that the obvious differences in alkaline solution, Ag / Ti electrode and polycrystalline silver electrode electrocatalytic activity for the oxidation of hydrazine hydrate and sodium borohydride. Polycrystalline silver electrode, Ag / Ti electrode respectively on the initial potential of the electrochemical oxidation of hydrazine hydrate and sodium borohydride-0.60V and-0.70V, and the former-0.30V and-0.35V respectively;, Ag / Ti electrode on the oxidation of hydrazine hydrate and sodium borohydride oxidation peak current density were 212.8mA/cm -2 and 230.4mA/cm -2 , the former nearly 8 times and 12 times. The potential step experiments show that polycrystalline silver electrode and Ag / Ti step of steady-state current on the electrode with the concentration of hydrazine hydrate and sodium borohydride increases, and a good linear growth. (2) Hydrothermal Method AgNi / Ti electrode was prepared in the same way as the Ag / Ti electrode comparing electrochemical test results showed that: a mix of Ni Ag 86 Ni 14 / Ti electrode oxidation of hydrazine hydrate showed superior catalytic performance compared with Ag / Ti electrode, Ag 86 Ni 14 / Ti electrode 0.09V, ahead of the starting potential of oxidation of hydrazine hydrate (60mmol / L), the oxidation peak current density of 257mA/cm -2 -0.60V, Ag / Ti electrode 2 times. The Ni added significantly improve the performance of the catalyst for the electrochemical oxidation of hydrazine hydrate. (3) Hydrothermal Method AgCu / Ti electrode electrochemical oxidation of hydrazine hydrate, also has a high electro-catalytic performance. The electrochemical test results demonstrate that compared to the Ag / Ti electrode, AgCu / Ti has a higher rate of oxidation reaction and the beginning of the lower oxidation potential of the electrode on hydrazine. Ag: Cu ratio of 79:21 of the electrode, electrode the AgCu / Ti exhibit better catalytic activity. (4) the use of electrodeposition prepared AgCu / Ti electrode, the ultra-low concentrations of hydrazine hydrate were detected, under the anodic peak current of approximately-0.1V with the hydrazine concentration increased showed regular decrease is due to the hydrazine in these electrically multilayer adsorption of the catalyst surface is caused, and the reciprocal of the peak current density of the anodic peak (i ?? -1 ), a good linear relationship with hydrazine concentration, can be used for ultra-low concentration hydrazine detection.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Electrochemical,electrolytic,magnetic,chemical > Electrolysis and Electrode role > Electrode process
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