Matter Paul H, Wang Eugenia, Arias Maria, Biddinger Elizabeth J, Ozkan Umit S
Department of Chemical Engineering, The Ohio State University, Columbus, OH 43210, USA.
J Phys Chem B. 2006 Sep 21;110(37):18374-84. doi: 10.1021/jp062206d.
Noble-metal-free active catalysts for the oxygen reduction reaction (ORR) in an acidic environment were prepared from the pyrolysis of acetonitrile at 900 degrees C over alumina and metal-doped alumina. This work includes analyses of the nitrogen-doped carbon preparation process, characterization of the carbon materials formed, and activity testing for the ORR. The nitrogen-containing carbon nanostructures that formed during the pyrolysis of acetonitrile could be purified by washing the product with hydrofluoric acid. A wide range of techniques were used to characterize the solid carbon products of the acetonitrile decomposition. While the samples have many similar physical properties, X-ray photoelectron spectroscopy and transmission electron microscopy showed evidence that differences in the nanostructure and surface functional groups of the samples are likely to account for observed differences in oxygen reduction activity. The most active catalysts were prepared over alumina impregnated with up to 2 wt % Fe, although the catalysts that were prepared by acetonitrile pyrolysis over alumina with no metal doping still had significant activity. In comparison to a 20 wt % platinum on Vulcan carbon catalyst, the most active samples only have an additional 100 mV overpotential. The selectivity of the catalysts for complete oxygen reduction to water followed a trend similar to activity. The best selectivity to water versus peroxide obtained was 99%, or equivalently, an n of 3.98 (i.e., 3.98 electrons transferred out of a maximum of 4 electrons per mole of oxygen that is reduced), as determined by rotating ring-disk electrode testing.
通过在900摄氏度下于氧化铝和金属掺杂氧化铝上热解乙腈，制备了用于酸性环境中氧还原反应（ORR）的无贵金属活性催化剂。这项工作包括对氮掺杂碳制备过程的分析、所形成碳材料的表征以及ORR活性测试。在乙腈热解过程中形成的含氮碳纳米结构可以通过用氢氟酸洗涤产物来纯化。使用了多种技术来表征乙腈分解的固体碳产物。虽然样品具有许多相似的物理性质，但X射线光电子能谱和透射电子显微镜显示，样品纳米结构和表面官能团的差异可能是观察到的氧还原活性差异的原因。活性最高的催化剂是在浸渍了高达2 wt%铁的氧化铝上制备的，不过通过在未掺杂金属的氧化铝上热解乙腈制备的催化剂仍具有显著活性。与Vulcan碳上负载20 wt%铂的催化剂相比，活性最高的样品仅具有额外100 mV的过电位。催化剂将氧完全还原为水的选择性遵循与活性相似的趋势。通过旋转环盘电极测试确定，对水相对于过氧化物的最佳选择性为99%，即n为3.98（即每摩尔被还原的氧最多4个电子中转移出3.98个电子）。
