Sustainable metal-free carbogels as oxygen reduction electrocatalysts
Sustainable metal-free carbogels as oxygen reduction electrocatalysts
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DOI：
10.1039/c7ta02001e
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发表时间：
2017-08-21
影响因子：
11.9
通讯作者：
Titirici, M-M.
中科院分区：
文献类型：
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作者：
Preuss, K.;Tanase, L. C.;Titirici, M-M.
可调谐的氮掺杂碳凝胶已经通过简单的一锅水热碳化，然后在1000摄氏度下热解，使用高度可用和低成本的前体，如葡萄糖和卵清蛋白合成。不同的物理活化比的氮气/氧气被用来证明一个可持续的和简单的方法，改变表面积，孔径和元素组成，以研究它们的效果，氧气还原反应时，用作电催化剂。发现氮与2%的氧混合的比例最有利于通过产生874 m2/g的高表面积以及吡啶氮与石墨氮的有利比例来提高催化活性。研究了硫掺杂和/或硼掺杂对碳凝胶结构的影响。硫的掺入不干扰结构形成，但降低了表面积和氮含量，导致ORR性能降低。然而，用硼酸掺杂硼通过充当催化剂产生不同的碳凝胶结构，通过充分利用卵清蛋白作为氮源而不是作为结构导向/表面稳定剂产生改变的形态、表面积、孔性质和更高的氮含量。发现氮含量决定极限电流，而氧含量对起始电位的影响很小。假设氮和硼之间的协同效应产生更高的电子转移数和更低的过氧化氢产率在硼氮共掺杂的碳凝胶比纯氮掺杂的系统中观察到的。
Tuneable nitrogen doped carbogels have been synthesised by a simple one-pot hydrothermal carbonisation, followed by pyrolysis at 1000 degrees C, using highly available and low cost precursors such as glucose and ovalbumin. Different physical activation ratios of nitrogen/oxygen were used to demonstrate a sustainable and easy method for changing surface area, pore size and elemental composition in order to investigate their effect on the oxygen reduction reaction when used as electrocatalysts. A ratio of nitrogen mixed with 2% of oxygen was found to be most beneficial for enhancing the catalytic activity by creating a high surface area of 874 m(2) g(-1) as well as a favourable ratio of pyridinic to graphitic nitrogen. The influence of sulphur doping and/or boron on the carbogel structure was investigated. Incorporation of sulphur does not interfere with the structure formation, but decreases the surface area and nitrogen content resulting in diminished ORR performance. However, boron doping with boric acid results in a different carbogel structure by acting as a catalyst, creating an altered morphology, surface area, pore properties and higher nitrogen content by fully utilising ovalbumin as a nitrogen source instead of as a structure directing/surface stabilising agent. Nitrogen content is found to determine the limiting current, while the oxygen content has a small influence on the onset potential. An assumed synergistic effect between nitrogen and boron generates higher electron transfer numbers and lower hydrogen peroxide yields in boron nitrogen co-doped carbogels than those observed in purely nitrogen doped systems.