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Study Of Electro-catalytic Properties Of Ammonia Oxidation Of Ir Catalyst

Posted on:2014-05-31Degree:MasterType:Thesis
Country:ChinaCandidate:M Z YuFull Text:PDF
GTID:2261330401469340Subject:Analytical Chemistry
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NH3is an alkaline substance, it is present in the air with the free form. NH3is widely used in the industry and in our daily life. For example, oil refinery, pharmaceutical, fuel, plastic et al. NH3is a colorless and pungent gas. Its density is less than air. NH3has a greater harm to the human body. When the concentration is low, it can absorb the skin moisture, leading to protein denaturation and decrease in the body’s resistance. When the concentration is high, it can cause cardiac arrest and respiratory arrest. Therefore, the investigation of NH3sensor has been became a hot area.This thesis-mainly investigated the electrocatalytic performance of different forms of noble metal Ir for oxidation of ammonia in sodium perchlorate neutral electrolyte.The main results obtained are as follows:1.Electrocatalytic performance of Ir-P/XC catalyst for oxidation of ammoniaIr/XC and Ir-P/XC catalysts were prepared with the same method and were characterized with XRD method. Ir particles in the two catalysts have the similar size and crystallinity. However, the electrocatalytic activity of Ir-P/XC catalyst for oxidation of ammonia is higher than that of the Ir/XC catalyst. Ammonia current density on the electrode has the good linear relation, the correlation coefficient R is0.99709.2.Electrocatalytic Performance of Ir catalyst supported with WC and XC for oxidation of ammoniaThe Ir-WC/XC-0.25、Ir-WC/XC-0.5、Ir-WC/XC-1.0、Ir-WC/XC-2.0and Ir-WC/XC-3.0catalysts were prepared with general liquid phase reduction methd. Due to the dopping of WC, lattice volume becomes large, the specific diffractive peaks shift negatively, the average particle size of Ir particles becomes small. For example, the average particle size of Ir particles in the Ir-WC/XC-0.25catalyst is1.1nm. Among5catalysts, the electrocatalytic activity of the Ir-WC/XC-0.25catalyst for oxidation of ammonia is best. The current density of ammonia oxidation at the Ir-WC/XC-0.25catalyst electrode has the good linear relation, The correlation coefficient R is0.9728. Thus, it really shows that Ir-WC/XC-0.25could be used as the working electrode in current-type electrochemical ammonia sensor.3. Electrocatalytic Performance of C supported Ir-Cu catalyst for oxidation of ammoniaThe experimental results showed no obvious electrocatalytic activity of Cu for oxidation of ammonia. The Ir-Cu/XC-1:2, Ir-Cu/XC-3:1and Ir-Cu/XC-2:1catalysts were prepared with dopping different proportion of Cu. In addition, the Ir/XC and Cu/XC catalysts were also prepared. Among these catalysts, the electrocatalytic activity and stability of the Ir-Cu/XC-3:1catalyst is better than that of the Ir/XC catalyst. However, the increase is not obvious. The reason for the good electrocatalytic stability may be due to that the addition of Cu improves the catalyst dispersion.4.Electrocatalytic performance of C supported Ir-Fe catalyst for oxidation of ammoniaThe size of Fe particles is smaller than that of Ir particles. The Ir-Fe/XC and Ir/XC catalysts showed the similar specific diffraction peaks. The results suggest that Fe enters into the lattice and forms the Ir-Fe alloy. The increase of the electrocatalytic activity of the Ir-Fe/XC catalyst for oxidation of ammonia is not obvious. However, its electrocatalytic stability is obviously improved. It is similar to Ir-Cu alloy.
Keywords/Search Tags:Current-type ammonia sensor, Ir/XC catalyst, Ir-P/XC catalyst, Ir-WC/XC catalyst, Ir-Cu/XC catalyst, Ir-Fe/XC cataly
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