Overview

This dissertation, Iron-nitrogen-doped Carbon With Hierarchical Porous Structures: Synthesis, Characterization, and Electrochemical Applications by Ming, Zhou, 周明, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled IRON-NITROGEN-DOPED CARBON WITH HIERARCHICAL POROUS STRUCTURES: SYNTHESIS, CHARACTERIZATION, AND ELECTROCHEMICAL APPLICATIONS submitted by ZHOU MING for the degree of Doctor of Philosophy at The University of Hong Kong in December 2015 Synthetic hierarchical porous carbons have been extensively investigated due to their narrow pore size distribution, well-defined and tunable pores, and large surface area. Hard template methods are the most effective synthesis approach and iron-nitrogen doping introduces unique properties to the carbon materials. In this thesis, iron-nitrogen-doped macro hollow core mesoporous shell (HCMS) carbons are synthesized for the first time using solid core mesoporous shell silica as hard template. Both core diameter and shell thickness can be adjusted and additional metal oxide nanoparticle catalyst is deposited onto the carbons using a thermal oxidation method. The synthesized iron-nitrogen-doped carbons demonstrate almost the best overall performance in supercapacitor, aqueous oxygen reduction reaction (ORR), and Li-O battery applications. i The HCMS has a mesopore size of 2 4 nm while iron-nitrogen-doped carbon (Fe-N-HCMS) has larger mesopores (8 nm) and higher pore volume than non-doped carbon (HCMS). When applied as supercapacitor electrodes, Fe-N-HCMS presents excellent performance with a capacitance of 352 F/g (0.5 A/g) from heteroatom pseudocapacitances and high surface area. An improved high-rate performance is observed for Fe-N-HCMS due to well-defined mesopores reducing transport resistance and thin layer shortening diffusion distance. After 8000 cycles, the capacitance retention of Fe-N-HCMS is 92% due to improved mechanical strength and higher graphitic structure while that of HCMS is only 85%. Fe-N-HCMS performs much better in organic electrolyte than HCMS, giving a capacitance of 189.4 F/g (0.5 A/g) and maintaining a value of 127 F/g (10 A/g) while the capacitance of HCMS (0.5 A/g) is only 82 F/g. The power and energy densities have been greatly enhanced in organic electrolyte. Fe-N-HCMS presents excellent ORR activity with an onset potential of 0.83 V (vs RHE) and a limiting current density of -7.0 mA/cm (2025 rpm). Fe-N-HCMS also displays high tolerance to methanol cross-over and high stability with of reduction potential at -2.5 mA/cm after 1000 cycling tests. At low potential, the number of electrons transferred is 3.8. High current density of Fe-N-HCMS is attributed to a regular core-shell structure with high surface area which leads to enhanced mass- and charge-transfer. Strong methanol tolerance arises from the intrinsic advantage of Fe-N-C active sites. High stability is due to the partially crystalline lattice of Fe-N-C, leading to enhanced mechanical strength and higher resistance to degradation. Fe-N-HCMS also performs excellent as catalyst for ORR and support for OER catalyst (RuO ) in Li-O battery with a durable, reversible, and high capacity, as well 2 2 as high voltage efficiency. A 3.5 V charging potential and a 2.5 V discharge potential are observed over 10,000 mAh/g and over 50 cycles at 1.0 A/g. These values are also maintained at 3.6 V and 2.5 V at a higher current density of 2.0 A/g. ii Well-defined core-shell structure provides excellent mass transport for oxygen and Li ion diffus

Full Product Details

9781361034941

Table of Contents

Reviews

Author Information

Tab Content 6

Customer Reviews

Recent Reviews

Countries Available