Graduate School of Energy Science and Technology (GEST), Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Republic of Korea.
Nanoscale. 2019 Mar 14;11(11):5038-5047. doi: 10.1039/c8nr10327e.
N-Doped carbon materials have been intensively studied to replace Pt catalysts for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs). However, the low doping level in these catalysts results in a limited number of ORR active sites, so high catalyst loading is still required. Hence, the electrode thickness becomes extra thick, causing large mass transfer resistance in AEMFCs. In this study, we propose a unique hybrid catalyst concept utilizing charge redistribution at the graphene-transition metal interface to modify the electronic structure of graphene and simultaneously create multiple carbon active sites. The hybrid catalyst consists of n-type nano-graphene shells (NGS) three-dimensionally coated on the surface of transition metal nanoparticles highly dispersed on carbon supports. The n-type NGS catalysts efficiently facilitate oxygen adsorption owing to facile charge transfer from the metal nanoparticles underneath and provide abundant active carbon sites owing to their structural benefits. As a result, despite the same catalyst loading, the NGS catalyst shows high ORR activity and greater durability than a carbon-supported Pt (Pt/C) catalyst.
N 掺杂碳材料已被深入研究，以替代 Pt 催化剂用于阴离子交换膜燃料电池（AEMFC）中的氧还原反应（ORR）。然而，这些催化剂中的掺杂水平较低，导致 ORR 活性位点数量有限，因此仍然需要高催化剂负载量。因此，电极厚度变得额外厚，在 AEMFC 中导致较大的质量传递阻力。在本研究中，我们提出了一种独特的混合催化剂概念，利用在石墨烯-过渡金属界面处的电荷重新分布来修饰石墨烯的电子结构，同时创建多个碳活性位点。该混合催化剂由三维覆盖在高度分散在碳载体上的过渡金属纳米颗粒表面上的 n 型纳米石墨烯壳（NGS）组成。n 型 NGS 催化剂由于来自下方金属纳米颗粒的易于电荷转移而有效地促进氧气吸附，并由于其结构优势而提供丰富的活性碳位点。因此，尽管催化剂负载量相同，NGS 催化剂表现出比碳负载 Pt（Pt/C）催化剂更高的 ORR 活性和更好的耐久性。
