Department of Chemical Engineering & Materials Science, Michigan State University East Lansing, MI 48824, USA.
Phys Chem Chem Phys. 2014 Mar 14;16(10):4576-85. doi: 10.1039/c3cp54751e.
Iron based nitrogen doped carbon (FeNC) catalysts are synthesized by high-pressure pyrolysis of carbon and melamine with varying amounts of iron acetate in a closed, constant-volume reactor. The optimum nominal amount of Fe (1.2 wt%) in FeNC catalysts is established through oxygen reduction reaction (ORR) polarization. Since the quantity of iron used in FeNCs is very small, the amount of Fe retained in FeNC catalysts after leaching is determined by UV-VIS spectroscopy. As nitrogen is considered to be a component of active sites, the amount of bulk and surface nitrogen retention in FeNC catalysts are measured using elemental analysis and X-ray photoelectron spectroscopy, respectively. It is found that increasing nominal Fe content in FeNC catalysts leads to a decreased level of nitrogen retention. Thermogravimetric analysis demonstrates that increasing nominal Fe content leads to increased weight loss during pyrolysis, particularly at high temperatures. Catalysts are also prepared in the absence of iron source, and with iron removed by washing with hot aqua regia post-pyrolysis. FeNC catalysts prepared with no Fe show high retained nitrogen content but poor ORR activity, and aqua regia washed catalysts demonstrate similar activity to Fe-free catalysts, indicating that Fe is an active site component.
铁基氮掺杂碳 (FeNC) 催化剂是通过在封闭、恒容反应器中高温热解碳和三聚氰胺，并加入不同量的醋酸铁合成的。通过氧还原反应 (ORR) 极化，确定了 FeNC 催化剂中最佳的名义铁含量 (1.2wt%)。由于 FeNC 中使用的铁量非常小，因此通过 UV-VIS 光谱法测定了浸出后 FeNC 催化剂中残留的铁量。由于氮被认为是活性位的组成部分，因此使用元素分析和 X 射线光电子能谱法分别测量了 FeNC 催化剂中体相和表面氮的保留量。结果发现，增加 FeNC 催化剂中的名义铁含量会导致氮保留水平降低。热重分析表明，增加名义铁含量会导致热解过程中重量损失增加，尤其是在高温下。还在没有铁源的情况下制备了催化剂，并在热王水后通过浸出除去铁。没有 Fe 制备的 FeNC 催化剂表现出高的氮保留含量，但 ORR 活性差，而王水洗涤的催化剂与无铁催化剂具有相似的活性，表明 Fe 是活性位组成部分。
