Chen Teng, Guo Siqi, Yang Jie, Xu Yida, Sun Jie, Wei Dali, Chen Zhaoxu, Zhao Bin, Ding Weiping
Key Lab of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu, 210093, China.
Chemphyschem. 2017 Dec 6;18(23):3454-3461. doi: 10.1002/cphc.201700834. Epub 2017 Oct 24.
The development of low-cost non-precious-metal electrocatalysts with high activity and stability in the oxygen reduction reaction (ORR) remains a great challenge. Heteroatom-doped carbon materials are receiving increased attention in research as effective catalysts. However, the uncontrolled doping of heteroatoms into a carbon matrix tends to inhibit the activity of a catalyst. Here, the in situ activation of a uniquely structured nitrogen-doped carbon/Ni composite catalyst for the ORR is demonstrated. This well-designed catalyst is composed of a nitrogen-doped carbon shell and embedded metallic nickel. The embedded Ni nanoparticles, dispersed on stable alumina with a high specific surface area for protecting them from agglomeration and in an unambiguous composite structure, are electron-donating and are shielded by the nitrogen-doped carbon from oxidation/dissolution in harsh environments. The electronic structure of the nitrogen-doped carbon shell is modulated by the transfer of electrons at the interface of nitrogen-doped carbon-Ni heterojunctions owing to the Mott-Schottky effect. The electrochemically active surface area result implies that the active sites do not relate to Ni directly and the enhanced catalytic activity mainly arises from the modulation of nitrogen-doped carbon by nickel. XPS and theoretical calculations suggest that the donated electrons are transferred to pyridinic N primarily, which ought to enhance the catalytic activity intrinsically. Benefiting from these transferred electrons, the half-wave potential of the nitrogen-doped carbon/Ni composite catalyst is 94 mV positively shifted compared to the Ni-free sample.
开发在氧还原反应（ORR）中具有高活性和稳定性的低成本非贵金属电催化剂仍然是一项巨大挑战。杂原子掺杂的碳材料作为有效的催化剂在研究中受到越来越多的关注。然而，将杂原子无控制地掺杂到碳基体中往往会抑制催化剂的活性。在此，展示了一种用于ORR的独特结构的氮掺杂碳/Ni复合催化剂的原位活化。这种精心设计的催化剂由氮掺杂碳壳和嵌入的金属镍组成。嵌入的Ni纳米颗粒分散在具有高比表面积的稳定氧化铝上，以防止它们团聚，并且处于明确的复合结构中，具有给电子性，并且被氮掺杂碳屏蔽，以免在恶劣环境中氧化/溶解。由于莫特-肖特基效应，氮掺杂碳壳的电子结构通过在氮掺杂碳-Ni异质结界面处的电子转移而被调制。电化学活性表面积结果表明，活性位点与Ni没有直接关系，增强的催化活性主要源于镍对氮掺杂碳的调制。X射线光电子能谱（XPS）和理论计算表明，捐赠的电子主要转移到吡啶型N上，这应该从本质上提高催化活性。受益于这些转移的电子，与无Ni样品相比，氮掺杂碳/Ni复合催化剂的半波电位正向偏移了94 mV。
