金屬有機骨架於超級電容器與氧氣還原反應之應用

Electrochemical Applications of Metal-organic Frameworks for Supercapacitors and Oxygen Reduction Reaction

馮 浩(Hao Feng)

指導教授 ： 何國川

國立臺灣大學/工學院/化學工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201701260

摘要

在所有分類的孔洞材料中擁有最高表面積的金屬有機骨架在本論文被選作電極材料，利用其特有的特性(高比表面積、高孔隙度、有序晶體結構…等)與在水溶液中的穩定性，開闢將此金屬有機骨架運用於各種水相系統中的電化學應用之機會，包含超電容器(第三章)與氧氣還原反應(第四章)。
在第三章中，金屬有機骨架/導電高分子奈米複合材料被選為雙電層電容器之電極材料。由鋯金屬節點與芘類有機連結器所組成的金屬有機骨架材料，具有高比表面積特性，其高比表面積可形成電雙層電容，同時，藉由導電高分子的加入，可克服金屬有機骨架導電性不佳之缺點，進而提升電容表現。另外，透過不同導電高分子的添加量，可同時控制奈米複合材料的比表面積與導電性。電化學實驗結果顯示，其可在2 A/g 的充放電電流密度之下達到680 F/g的比電容值，同時在6,000圈的充放電循環後，仍可維持85 %的初始比電容值。此研究成果顯示此奈米複合材料具有作為雙電層電容器之電極材料的潛力。
在第四章中，由鋯金屬節點與芘類有機連結器所組成的金屬有機骨架材料被選為自犧牲模板，將其在氮氣下經由高溫轉換成奈米級多孔碳。經高溫鍛燒後，奈米級多孔碳不僅提升導電度，更維持高比表面積。藉由高比表面積的碳材對於氧氣還原之催化性，將所製備之奈米級多孔碳作為氧氣還原反應之催化電極，並探討其在強鹼下之催化效能。電化學實驗結果顯示，其催化能力能與白金(鉑)電極作為匹比，顯示此奈米級多孔碳具有作為氧氣還原反應之催化電極材料的潛力。

關鍵字

金屬有機骨架 ； 超級電容器 ； 氧氣還原反應 ； 能量儲存與轉換 ； 孔洞材料

並列摘要

In this thesis, expect for the introduction (Chapter 1), experimental (Chapter 2), and conclusions and suggestions (Chapter 5), in the rest of the thesis, we will put our effort to introduce our development on the electrochemical applications of metal-organic frameworks. There are two different but related chapter, discussing about the application of metal-organic framework/PEDOT:PSS nanocomposite as high-performance electrode materials for supercapacitors (Chapter 3) and nanoporous carbon derived from porphyrinic-based metal-organic frameworks as non-precious electrocatalysts for oxygen reduction reaction (Chapter 4).
In chapter 3, the metal-organic framework (MOF)/conducting polymer nanocomposites used as an electrode material in non-carbon-based electric double layer capacitors (EDLCs) exhibiting high BET surface area (2018 m2g-1) and reasonably good electrical conductivity. In brief, porphyrinic zirconium metal–organic frameworks (MOF-525) nanocrystals were incorporated with conducting polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) which interconnect isolated particles to enhance both conductivity and capacitance performance. By controlling the amount of PEDOT:PSS loaded to the MOF-525, the conductivity can be modulated as well as the porosity of the composite. Electrochemical studies showed that as-prepared nanocomposite exhibits an outstanding specific capacitance of 680 F g-1 at a current density of 2 A g-1, which exceeds that of its individual constituents and the capacity retention is greater than 85% over 6000 cycles. These results demonstrate a promising application for MOF/conducting polymer nanocomposites which have high BET surface area and electrical conductivity for the highly efficient supercapacitor.

In chapter 4, developing non-precious electrocatalysts for oxygen reduction reaction (ORR) is of critical importance on the performance of several electrochemical devices. In this work, porphyrin-based metal-organic framework (MOF-525) was chosen as a self-sacrificial template to synthesize porous carbon by direct carbonization for the first time. The MOF-derived porous carbon (MDPC) using MOF-525 has comparable performance on ORR electrocatalysis with that of the commercial platinum on carbon (Pt/C) catalyst under alkaline conditions in the presence of saturated oxygen. After pyrolysis, the MDPC not only keep the high surface area of its mother material, MOF-525, but also has significantly increased electrical conductivity. These results demonstrate a promising strategy to fabricate a nitrogen-doped meso-microporous hierarchical carbon derived from MOF-525 as non-precious electrocatalysts for ORR by a facile and cost-effective MOF-templated process.

並列關鍵字

energy storage and conversion ； metal–organic frameworks ； oxygen reduction reaction ； porous materials ； supercapacitor

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