Electrochemical behavior of Ir_xRu_{1鈭?span style='font-style: italic'>x}O₂ oxides as anodic electrocatalyst for electrosynthesis of dinitrogen pentoxide

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• 作者：Qingfa Wang ; ^{qingfaw@yahoo.com.cn} ; Fangmin Wu ; Nan Wang ; Li Wang ; Xiangwen Zhang
• 关键词：Electrochemical synthesis ; Dinitrogen pentoxide ; N2O4 oxidation ; IrxRu1&minus ; xO2 oxides ; Anodic electrocatalyst
• 刊名：Electrochimica Acta
• 出版年：2012
• 期刊代码：30_00134686
• 类别：ch
• 出版时间：15 July, 2012
• 卷：74
• 期：Complete
• 页码：227-234
• 文件大小：1249 K

摘要

The Ir_xRu_1鈭?em>xO₂/Ti electrodes (x = 0-1) were prepared by thermal decomposition of non-aqueous solutions of H₂IrCl₆ and RuCl₃. The surface morphology and microstructure of the Ir_xRu_1鈭?em>xO₂ coatings were characterized by XRD and SEM. The electrochemical characterization of the surface was carried out in a 0.5 mol L^鈭? H₂SO₄ solution. The Ir_xRu_1鈭?em>xO₂ coating with x = 0.5 showed a minimal nanocrystalline particle size and a maximum surface charge (q*). The electrochemical behaviors of the Ir_xRu_1鈭?em>xO₂ coatings for oxidation of N₂O₄ were determined by cyclic voltammetry (CV), the open circuit potential (OCP) and Tafel plot in 1.7 mol L^鈭? N₂O₄/HNO₃ solutions. The open-circuit potential (E_ocp) in N₂O₄/HNO₃ solution was about 1.18 V and it was almost independent of the surface composition. Cyclic voltammetry showed a broad wave feature at 1.4-1.8 V in the anodic scan, which was attributed to the oxidation of NO₂ derived from N₂O₄ to NO₂⁺. The redox couple of NO₂/NO₂⁺ showed a quasi-reversible behavior and the process was under diffusion control. The electrocatalytic activities of various Ir_xRu_1鈭?em>xO₂ coatings for oxidation of N₂O₄ were evaluated by potentiostatic polarization curves under the quasi-steady state conditions. The Ru_0.5Ir_0.5O₂ coating showed the lowest Tafel slope, 35.7 mV, in the low current densities, indicating that this coating had the highest electrocatalytic activity. The experiments of electrochemical synthesis of N₂O₅ from N₂O₄ in nitric acid also indicated that the Ru_0.5Ir_0.5O₂ coating had the best electrocatalytic performance.