Study On Preparation Of Ti-based Ir_xSi_1-xO₂Coating Anodes And Its Application To Electrosynthesis Of N₂O₅

Dinitrogen pentoxide (N2O5) is a green nitrating agent. The electrochemical synthesis of N2O5by oxidation of N2O4is the most promising one to be industrialized due to its cleanness, safety and accordance with green chemistry, and becomes the main research orientation. The anode material is one of the key materials which directly affect the current efficiency, specific energy and the stable operation of electrolysis system. In order to meet the above requirements, SiO2was doped into IrO2coatings to enhance the electrochemical stability and improve the electrocatalyticactivity. In this thesis, a series of IrxSi1-xO2coatings were prepared on Ti plates by thermal decomposition method. The surface morphology, coating structure, electrocatalysis performance and electrochemical stability of these anodes prepared in different compositions were characterized by SEM, XRD, electrochemical measurement and accelerated life test. The doping of SiO2inhibited the growth of IrO2crystal, changed the structure of coating and made the coating porous. This approach increased the surface area of the coating and also made more active sites exposed in the electrolyte. Consequently, the electrocatalytic activity and electrochemical stability were improved. With the increase of SiO2in composition, the electrochemical activity and the accelerated life increased firstly and then decreased. The Ir0.5Si0.5O2/Ti electrode had the highest electrochemical stability and its accelerated life was about370h. Therefore, the optimal composition of SiO2in IrxSi1-xO2coatings was between40%and50%. The influence of calcination temperature on properties of Ir0.5Si0.5O2/Ti anodes was investigated. With the increase of calcination temperature, more and more rutile IrO2crystal was formed and the particle size increased continuely at the same time. In addition, the electrochemical activity decreased. The accelerated life increased firstly and then decreased. When the temperature was600°C, the lifetime reached the maximum. Considering the electrochemical activity and the lifetime, the appropriatecalcination temperature was500°C-600°C, At last, the electrocatalysis performance in N2O4/HNO3system and the electro-oxidation reaction of N2O4to produce N2O5catalyzed by a series of IrxSi1-xO2/Ti electrodes was performed. With the increase of calcination temperature and the content of SiO2, the voltammetric charge and the current efficiency increased firstly and then decreased, while the specific energy showed a contrary variation. The Ir0.6Si0.4O2/Ti electrode calcinated at500°C had the best performance in electrosynthesis of N2O5from N2O4with the maximal current efficiency being79%and the minimal special energy being0.94kWh kg1N2O5.