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Palladium on carbon fiber chain silver alloy nanoparticles Preparation and Hydrogen Sensing Properties

Author: ZhouBaoPing
Tutor: YuGang
School: Hunan University
Course: Physical and chemical
Keywords: Palladium- silver alloy Nanoparticle Chains Hydrogen Sensing Carbon fiber Electrodeposition
CLC: TB383.1
Type: Master's thesis
Year: 2010
Downloads: 52
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Abstract


In this paper, polyacrylonitrile (PAN) carbon fibers as a template prepared by electrodeposition of the Pd-Ag Alloy Nanoparticle Chains, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) and other testing methods to characterize the alloy particle chains The morphology and composition, study their morphology and the relationship between process parameters; CHI660B electrochemical workstation and applied to detect the hydrogen gas sensing performance obtained by studying the following conclusions: (1) PAN-based carbon fiber surface Electrodeposition required before pretreated. Preferably the carbon fiber surface pretreatment conditions: at a temperature of about 400 ℃ ignition to glue 30-60 min; 40 ~ 50 ℃ under the conditions of roughening 40-80 min. After stripping, degreasing, roughening treatment, similar to the carbon fiber surface showing a stepped surface of highly oriented graphite morphology and stairs neat, is conducive to the formation of alloy nano-chain array. (2) In the three-pulse potentiostatic electrodeposition process, the growth time and growth potential of the alloy composition has a great influence. In 0.5 mmol · dm-3 Pd (NO3) 2 0.033 mmol · dm-3 AgNO3 2 mol · dm-3 NH4N03 electrolyte obtained in palladium silver, when growing time exceeds 200s, the potential growth of -0.25 ~ -0.45 V between its silver content in the alloy to meet the requirements (16 to 25%). (3) a nuclear potential and time directly affects the ability to nanoparticle chain synthesis. The nucleation time control in 10 ~ 50 ms, a nuclear potential control at -10 ~ -1.5 V when the chain can be synthesized nanoparticles. (4) 0.5 mmol · dm-3 Pd (NO3) 2 0.033 mmol · dm-3 AgNO3 2 mol · dm-3 NH4NO3 electrolyte, using potentiostatic three pulse electrodeposition method of the carbon fiber template prepared silver palladium alloy nanoparticles chain, the process conditions were: 0.8 ~ 1.0 V oxidation 3-5 s; -1.0 ~ -1.5 V nucleation 10 ~ 50 ms, -0.25 ~ -0.35 V Growth 250-300 s. In this condition, the range of the alloy nanoparticles obtained distribution chain, parallel, mainly concentrated in the particle diameter of 80 ~ 120 nm in between, and the silver content of 16 to 25% range. (5) at room temperature, the Pd-Ag alloy nanoparticles chain volume fraction of the sensor to hydrogen 0.30-5.00% or less have any concentration response, and the response time varies with the concentration increased sharply reduced when the concentration exceeds 3.50% Response time is no longer with the concentration changes; palladium silver alloy nanoparticles chain fastest hydrogen sensor response time is about 300 s, sensitivity up to 31.4%; in hydrogen concentration from 0.30 to 2.20% and the response current in this range Hydrogen was a linear relationship between the concentration of more than 4.00% when the response electric current no longer increases with increasing hydrogen concentration change; the hydrogen concentration is less than 3.50%, the hydrogen sensor reproducibility and stability, when the concentration exceeds 3.50% When the hydrogen sensor over a long time to return to the original state. (6) H2 and Pd alloy nano-chain action principle for the solution - diffusion mechanism is a surface chemical adsorption, surface penetration and diffusion, desorption process. Volume expansion after palladium alloy hydrogen, close contact between the particles, the total resistance becomes small when the dehydrogenation, the crystal revert to the original state, the resistance increased.

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