이산화티타늄 나노튜브 어레이에 로딩된 이산화루테늄 전극의 전기화학적 기체발생 촉매특성

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 재료공학부, 2018. 8. 김진영.Ruthenium dioxide (RuO2) has an advantage of various chemical reactions like dehydrogenation, gas phase oxidation of HCl, and chloro-alkali process. In order to enhance stability of RuO2-based catalysts, the use of TiO2 is successful in recent years. In general, nanostructured scaffolds with the large relative surface area are adopted in the catalytic reactions for maximizing the number of active sites. For the electrocatalytic reactions, however, the scaffold should be conducting enough so that the charges required for the redox reaction can be transported to the surface of the loaded RuO2 catalysis. In the same context, TiO2 nanotube arrays (NTAs) can be a promising scaffold for the CER reaction, because it can transport charges (as evidenced in the solar cell or PEC applications) and it can be a good combination with RuO2 (as evidenced by DSA®). In addition, the nanoscale morphologies (e.g. tube length, pore diameter, and wall thickness), crystalline structure (e.g. crystalline phase and preferred orientation), and the electrical properties (e.g. conductivity) can be precisely controlled by the processing parameters. In this study, we firstly report the RuO2-loaded TiO2 NTAs as an efficient nanostructure electrode for the electrocatalytic CER process. Nanostructruring is well-known for enhancing the catalysts activity, we design TiO2 based nanostructure to investigate more active catalysts. The samples have been prepared electrochemically (i.e. electrochemical anodization for preparing TiO2 NTAs and electrochemical deposition for loading RuO2) and the dependence of the CER performance on the materials properties of the composite electrodes such as the crystallinity and electrical conductivity have been investigated. It has been found that the conductivity of the electrode under the anodic polarization is essential for achieving good CER performance, and the black TiO2 prepared by annealing as-anodized NTAs under an Ar atmosphere has been found to be the best scaffold for the RuO2 catalysis.1. Introduction 1 1.1 Chlorine Evolution Reaction (CER) 1 1.1.1 Chlor alkali process 1 1.1.2 Mechanism of chlorine evolution reaction 8 1.1.3 Recent research trend and literature review 12 1.2 TiO2 nanotube arrays (TiO2 NTAs) 22 1.2.1 Brief outline of TiO2 22 1.2.2 Self organized TiO2 Nanotube arrays 25 1.2.2.1 Factors affecting the morphology of TiO2 NTAs 29 1.2.3 Mechanistic regime 35 1.2.4 Black TiO2 and modification of physical properties of TiO2 NTAs 37 2. Experimental Details 44 2.1. Preparation of TiO2 nanotube arrays (TiO2 NTAs) 44 2.2. Preparation of the RuO2 NTAs electrode 45 2.3. Materials Characterization 46 2.4. Electrochemical measurements 47 3. Results and discussion 55 3.1 Preparation of TiO2 NTAs 55 3.1.1 voltage dependence of TiO2 NTAs 55 3.1.2 effect of pore widening 60 3.2 Preparation of TiO2@RuO2 electrodes 62 3.2.1 pulse electrodeposition and constant current electrodeposition 62 3.2.2 effect of annealing condition 71 3.3 Characterization of TiO2@RuO2 electrodes 73 3.3.1 Materials characterization 73 3.3.2 Electrochemical analysis 79 3.3.2.1 Evaluation of catalytic activity 79 3.3.2.2 Evaluation of conductivity under different bias 89 4. Conclusions 95 References 96 Abstract in Korean 115Maste