Department of Chemistry and Biochemistry, and ‡Department of Materials Science and Engineering, University of California-Los Angeles , Los Angeles, California 90095, United States.
ACS Appl Mater Interfaces. 2016 Oct 12;8(40):26769-26774. doi: 10.1021/acsami.6b08320. Epub 2016 Sep 28.
An efficient non-noble metal catalyst for the oxygen reduction reaction (ORR) is of great importance for the fabrication of cost-effective fuel cells. Nitrogen-doped carbons with various transition metal co-dopants have emerged as attractive candidates to replace the expensive platinum catalysts. Here we report the preparation of various copper- and nitrogen-doped carbon materials as highly efficient ORR catalysts by pyrolyzing porphyrin based metal organic frameworks and investigate the effects of air impurities during the thermal carbonization process. Our results indicate that the introduction of air impurities can significantly improve ORR activity in nitrogen-doped carbon and the addition of copper co-dopant further enhances the ORR activity to exceed that of platinum. Systematic structural characterization and electrochemical studies demonstrate that the air-impurity-treated samples show considerably higher surface area and electron transfer numbers, suggesting that the partial etching of the carbon by air leads to increased porosity and accessibility to highly active ORR sites. Our study represents the first example of using air or oxygen impurities to tailor the ORR activity of metal and nitrogen co-doped carbon materials and open up a new avenue to engineer the catalytic activity of these materials.
一种高效的非贵金属氧还原反应（ORR）催化剂对于制造具有成本效益的燃料电池至关重要。具有各种过渡金属共掺杂剂的氮掺杂碳已成为替代昂贵的铂催化剂的有吸引力的候选物。在这里，我们报告了通过热解卟啉基金属有机骨架来制备各种铜和氮掺杂碳材料作为高效 ORR 催化剂，并研究了热碳化过程中空气杂质的影响。我们的结果表明，空气杂质的引入可以显著提高氮掺杂碳中的 ORR 活性，并且添加铜共掺杂剂进一步增强了 ORR 活性，超过了铂的活性。系统的结构表征和电化学研究表明，经空气处理的样品具有更高的比表面积和电子转移数，这表明空气对碳的部分刻蚀导致了更高的孔隙率和对高活性 ORR 位点的可及性。我们的研究代表了首例使用空气或氧气杂质来调整金属和氮共掺杂碳材料的 ORR 活性的例子，并为这些材料的催化活性的工程设计开辟了新途径。
