液体丙烯腈低聚物制备石墨烯碳微米管及其负载非贵金属作为氧气还原反应催化剂的研究

In proton exchange membrane fuel cell (PEMFC), a large amount of platinum based catalyst is used both at the anode to catalyze the oxidation of hydrogen or other liquid fuel and at the cathode to catalyze oxygen reduction reaction (ORR). However, the commercialization and wide application of PEMFC are limited due to the high cost and low durability of the platinum based ORR catalyst. In this project, we put forward a new way to develop highly active and stable ORR catalyst based on non-precious-metal. The main research works is as follows:.A novel carbon precursor, liquid acrylonitrile polymer with low molecular weight (LANP) is synthesized by radical telomerization using 3-mercapto propionic acid as chain transfer agent. LANP is a brown serup-like liquid which is miscible with acetone. The solvent-free synthesis is environmentally friendly. At high temperature, LANP can be carbonized to form the carbon micro-tube with graphene wall (GW-CMT), which has large porosity and nitrogen doping and can be used as excellent ORR catalyst carrier. The reason lies in the formation of Fe-Nx at the site on the graphene wall of carbon tube and the strong electron-donation of graphene wall. By using LANP, FeCl3 and GW-CMT, through pre-oxidation and carbonization, we obtained a highly active non-precious-metal catalyst for ORR. The ORR activity of Fe/LANP/ GW-CMT is comparable with commercial Pt/C in basic electrolyte with a good stability. The synthetic technique is simple, environmentally friendly and cost-effective, exhibiting the wide prospect of commercialization.

质子交换膜燃料电池在工作过程中，大量的Pt基催化剂被用作催化氢气及其他液态燃料氧化的阳极催化剂和催化氧气还原反应 (ORR) 的阴极催化剂。目前的Pt基ORR催化剂成本高、耐久性不足，大大限制了质子交换膜燃料电池的性能和商业化前景。本项目提出了一种新的石墨烯碳微米管负载非贵金属作为ORR催化剂的制备方法。采用3-巯基丙酸作为链转移剂通过自由基调聚制备液态丙烯腈低聚物 (LANP)。高温下，LANP可以碳化生成管壁具有石墨烯结构的碳微米管（GW-CMT）。GW-CMT具有大的孔隙率和氮掺杂，能够为过渡金属的配位提供理想的位点。同时碳微米管壁的石墨烯结构具有强大的供电子能力，对这种配位有重要的稳定作用。将过渡金属盐、LANP、GW-CMT三者混合通过一定的烧结程序制备得到过渡金属/(LANP)/(GW-CMT)可作为ORR催化剂，该催化剂成本低、活性高、稳定性好，具有潜在的商业化前景。

质子交换膜燃料电池在工作过程中，大量的Pt基催化剂被用作催化氢气及其他液态燃料氧化的阳极催化剂和催化氧气还原反应 (ORR) 的阴极催化剂。目前的Pt基ORR催化剂成本高、耐久性不足，大大限制了质子交换膜燃料电池的性能和商业化前景。针对上述问题，本项目主要研究和结果如下：.（1）用液体丙烯腈低聚物作为前驱体，通过一步高温炭化形成硫、氮双掺杂Co-Nx-C结构。电镜和X射线光电子能谱结果表明，高温炭化后液体丙烯腈低聚物形成石墨化的碳结构，并且掺杂于石墨碳中的Co和N具有很强的相互作用。在碱性条件下的氧还原反应遵循四电子机理，氧还原反应的半波电位和极限扩散电流密度与商用20% Pt/C相近，并且具有优异的稳定性和耐久性，在质子交换膜燃料电池中具有潜在的应用价值；（2）通过一步高温炭化，制备得到硫、氮、铁掺杂的多孔碳材料。通过锌在高温下汽化作用使碳材料在烧结过程中致孔，显著增大碳材料的比表面积，从而增大反应活性位点数和活性物质的传质，促进氧还原反应的进行，在酸性和碱性条件下均具有比商业Pt/C更优的氧还原催化活性以及甲醇耐受性能；（3）合成了氮、氧双掺杂石墨烯包覆的纳米立方结构，具有优异的氧还原、析氧和析氢催化性能，在锌-空气电池和电解水领域具有重要的应用价值。