Hydrazine electrooxidation (HzOR) is considered one of the hydrogen production methodologies. For enhancing HzOR activity and reducing the use of PGM metals, we synthesized core-shell structured catalysts, varying by different transition metal species and pyrolysis temperature. As a result, Ni@NC-600, Fe@NC-600 and Co@NC-500, 600, 700, 800 and 900 are synthesized and tested for HzOR. Co@NC shows quite low onset potential, each trend of initial activity and durability is related to the graphitization of carbon shell and the ratio between hexgonal close packed (HCP) Co and face centered cubic (FCC) Co. The initial activity depends on the number of active sites, that is more blocked with the presence of highly graphitized carbon shell. However, Co@NC-900 didn’t show the best durability because too much graphitized carbon which block lots of active sites. In conclusion, Co@NC-800 is the most optimized catalyst for HzOR. Co@NC-800 shows Ponset at the potential of -0.134 V, which is much lower than Ponset of 40% Pt/C. However, the activity of 40% Pt/C is more higher than Co@NC-800 over the potential of 0.1 V, which could be attributed to the difference of the surface area of two catalysts.
Table Of Contents
Ⅰ. Introduction 1 1.1 Motivation 1 1.2 Theoretical background 2 1.2.1 Hydrazine Electrooxidation (HzOR) 2 1.2.2 HzOR fundamentals 3 1.2.3 Comparison of HzOR catalysts in alkaline 4 1.2.4 Direct Hydrazine Fuel Cell (DHFC) 6 1.2.5 Core shell catalyst – From PB to NC 7 1.3 Objectives 7 II. Experimental 9 2.1 Preparation of electrocatalysts 9 2.1.1 Chemicals 9 2.1.2 Synthetic approach 9 2.2 Characterization 11 2.2.1 X-ray diffraction (XRD) 11 2.2.2 Transmission electron microscopy (TEM) 11 2.2.3 X-ray photoelectron spectroscopic (XPS) 12 2.2.4 Electrochemical measurements 12 III. Results and discussion 13 3.1 M@NCs 13 3.1.1 Characterization 13 3.1.2 Morphology analysis 19 3.1.3 Electrochemical studies 22 3.2 Single phase metallic cobalt 30 3.2.1 HzOR activity 30 IV. Conclusions 31 References 32 국 문 요 약 문 38 Acknowledgement 39