Dissertation > Industrial Technology > Automation technology,computer technology > Automation technology and equipment > Automation components,parts > Transmitter ( converter),the sensor > Chemical sensors

Amperometric ammonia sensor

Author HanYiPing
Tutor LuTianHong
School Nanjing Normal University
Course Physical and chemical
Keywords Amperometric ammonia sensor Pt catalyst Ir catalyst Ir-Pt catalyst Neutral electrolyte Ionic liquids Lithium chloride
CLC TP212.2
Type Master's thesis
Year 2008
Downloads 136
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Ammonia have a wide range of applications in the industrial production and life, and ammonia toxicity even trace concentration will cause harm to humans. Monitoring of ammonia in the working and living environment of great significance development can online ammonia monitoring, low cost, high sensitivity and good selectivity amperometric ammonia sensor has become the hot spot of the current research and development this thesis neutral solution of ammonia oxidation electrocatalytic The performance of the catalyst, the best components of the electrolyte, to develop and assemble the practical application of amperometric ammonia sensor main results obtained are as follows: 1.NH 3 and NH to 4 < / sub> OH electrochemical properties found in the neutral of NaClO 4 solution, the electrochemical properties of the NH 3 and NH 4 OH and therefore, available NH 4 OH instead of NH 3 catalyst .2 NH 3 oxidation electrocatalytic properties. Pt comparison of the electrocatalytic properties of the the Ir catalyst of NH 4 OH oxidation of Pt and Ir catalysts were prepared by liquid phase reduction, and compared their neutral electrolyte NH 4 OH oxidation electrocatalytic properties and selectivity, NaClO 4 solution, Ir catalyst, NH 4 OH oxidation peak current density than Pt catalyst on 2.5 times larger, and CO of NH 4 OH detected on the Ir catalyst there is no interference, but significant interference on the Pt catalyst., Ir catalyst is more suitable as a current-NH 3 sensor the anode catalyst .3. research Ir catalyst structure their electrocatalytic properties electrodeposition method, NH 4 F the complexation restore law and THF complex reduction method were prepared surface Ir catalyst, and to study the impact of the electrocatalytic properties of the structure of these catalysts for ammonia oxidation. (1) electrodeposition prepared Ir catalyst, cyclic voltammetry, make Ir particles smaller active area increase of NH 4 OH electro-catalytic oxidation performance is improved. the NH 4 OH Ir catalyst oxidation peak potentials in the 0.85V about. NH 4 OH oxidation current density and the square root of the scan rate was a good linear relationship, the response is controlled by diffusion Therefore, NH , 4 OH Ir catalyst oxidation current density NH 4 OH concentration into a good linear relationship curve (2) found in NH 4 F complex reduction Ir catalyst prepared NH 4 F with IrCl 3 of forming a complex, therefore, obtained in the Ir-1 catalyst Ir particles small average particle diameter of 2.8 nm, a lower degree of crystallinity, while the conventional liquid phase reduction prepared IR-2 catalyst of Ir particles have an average particle size of 7.5nm, a higher degree of crystallinity, therefore, the IR-1 catalyst for ammonia oxidation electrocatalytic activity and stability are better than IR-2 Catalyst , is expected to be obtained in the electrochemical ammonia sensor the actual application (3) the THF complex reduction prepared a series of Ir different from the average particle size of the Ir catalyst and found that the average particle diameter of the obtained Ir catalyst Ir particles and degree of crystallinity decreases with THF and H 2 O volume ratio increases, which is due to THF with IrCl 3 of forming a complex, and can reduce Ir particles aggregation caused, but the smaller the average particle diameter and degree of crystallinity of not the Ir, the the NH 4 OH oxidation electrocatalytic properties better when THF and H 2 O ratio of 5:5, the average particle diameter of the Ir catalyst of Ir is 3.8nm, the Ir catalyst the NH 4 OH oxidation electrocatalytic properties preferably .4. The structure and properties of the different proportion to the Ir-Pt catalyst prepared THF complex reduction Ir-Pt mass ratio different Ir-Pt catalyst. found Ir and Pt have been formed of the average particle diameter of the alloy, Ir-Pt with Ir and Pt mass ratio of the reduction increases the Ir-Pt catalyst NH 4 0H oxidation of the electrocatalytic activity and stability is substantially better than that of the Ir catalyst, in particular the mass ratio of Ir-2 electrocatalytic properties of Pt catalyst NH 4 OH oxidation. although the poor performance of Pt resistance to CO interference in the Ir-Pt catalyst, CO interfere with the quality of the Ir-Pt ratio increased is reduced when the quality of the Ir-Pt ratio of 2, CO substantially interference does not occur, therefore, the mass ratio of 2 Ir-Pt catalyst performance is preferably .5. the catalyst and the electrolyte of the current-NH 3 Properties sensor (1) Compare the LiCl solution and the aqueous solution and an ionic liquid of the ionic liquid as the electrolyte of the sensor anti-dry performance. LiCl solution and an ionic liquid as the electrolyte, have good resistance to dry performance. ( 2) Compare the LiCl solution and the ionic liquid as the electrolyte sensors NH 3 of the response signal, found that the response signal of the ionic liquid as the electrolyte sensor NH 3 compromise in stability, but the rapid return to zero, the better the overall performance. (3) Compare the 45% Ir-Pt / C, 30% of the Ir-Pt / C and 20% Ir / C catalyst on the sensor performance. find the best 20% Ir / C catalyst stability of the sensor (4) CO and H 2 S interference tests show that the interference of CO gas can be basically negligible, while H 2 S interference, but by additional filter to eliminate interference gas adsorbents.

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