石墨烯基燃料电池催化剂的高性能化设计、原位可控制备与应用研究

Proton exchange membrane fuel cell (PEMFC) shows a broad application prospect in various fields such as traffic, transportation, communication due to its simple structure, high energy conversion efficiency, cleanness, environmental friendliness, quick response and other advantages. However, the cost of PEMFC and the short life resulting from the instability are the bottlenecks of the large-scale commercialization, which are mainly ascribed to the catalyst materials. Currently the exploration of highly efficient, stable and low-cost new catalysts becomes one of the key technologies in PEMFC. Graphene owns various unique excellent properties (such as high specific surface area and high electrical conductivity), and therefore, in recent years the research on graphene for supporting catalysts has drawn wide attention. However, the aggregation of graphene causes a large amount of catalyst particles embedding in graphene layers and it is difficult for the catalysts to be made full use of. This project will design vertically oriented reduced graphene oxide and three-dimensional graphene/carbon nanotubes to support catalysts towards the maximum exposure of the catalytic active sites, and at the same time control the microstructures of catalyst particles and modifying the graphene surface towards achieving stable anchoring of catalysts to the supports. This project aims to develop simple and controllable electrochemical methods to in situ construct graphene-based nanostructured catalysts on electrode surfaces and also precisely regulate the morphologies and structures of the catalysts, effectively realizing the synchronous ascension of both activity and stability of the catalysts.

质子交换膜燃料电池(PEMFC)以其结构简单、能量转换效率高、清洁环保、响应迅速等优势，在未来交通、运输、通讯等领域展示了广阔的应用前景。然而，PEMFC的成本以及稳定性引发的寿命问题是制约其大规模商业化的瓶颈，其中催化剂材料是根本。研究开发高效、稳定及低成本的新型催化剂成为当前发展PEMFC的关键技术之一。鉴于石墨烯的各种独特优异的性能（如：高比表面积、高导电性等），近年来石墨烯担载催化剂的研究广受关注。但石墨烯的聚集致使大量催化剂粒子包埋于石墨烯片层间而难以发挥催化性能，本项目设计采用垂直取向的还原氧化石墨烯和三维石墨烯/碳纳米管担载催化剂，使催化剂材料的表面活性位点最大程度地暴露，同时控制粒子微观形貌或修饰石墨烯表面，实现电催化剂的稳定担载。本项目旨在开发简单、可控的电化学方法在电极表面原位构筑石墨烯基纳米催化剂并精确调控催化剂的形态结构，有效实现催化剂活性与稳定性的同步提升。

石墨烯具有优异的电子传输性能、超高的比表面积和良好的稳定性，而且，石墨烯二维平面上的碳原子可以被其它元素取代形成掺杂石墨烯，呈现出高电催化活性，石墨烯的这些特点使石墨烯兼具载体和催化剂的双重功能，在催化领域引起了高度关注。然而，由于二维石墨烯的易聚集特性，即便其表面负载了纳米催化剂，仍倾向于面对面堆垛，致使大量催化剂被包埋在石墨烯片层之间，无法接触反应物分子，催化剂的性能远未充分发挥。因此，对石墨烯基电催化剂宏观形貌的控制是非常有必要的，合理设计、简单制备催化剂活性中心尽可能暴露的石墨烯基电催化剂材料，不仅可以显著提高催化剂的利用效率，而且可以加快反应物在电催化剂中的传质过程，提高电化学反应动力学。.本项目通过电化学沉积方法制备了垂直取向的石墨烯基电催化剂和三维网络结构的石墨烯/碳纳米管基电催化剂，得到了完全开放的结构。具体研究内容及结果如下：.（1）采用简单的循环伏安法制备了垂直取向石墨烯负载的Pd纳米粒子催化剂（Pd/VrGO），Pd/VrGO对甲醇氧化的质量活性为620.1 A g−1，分别是平躺石墨烯-Pd和商业Pd/C催化剂的1.9倍和6.2倍；.（2）将垂直取向石墨烯负载单一金属催化剂延伸到负载合金催化剂，制备的Pd-Cu/VrGO催化剂对甲醇氧化的质量活性高达762.8 A g−1，是商业Pd/C催化剂的7.1倍；.（3）制备了垂直取向石墨烯-聚苯胺载体（PANI@VrGO），在PANI上实现Pd纳米粒子的牢固锚定，对甲醇氧化的质量电流是商业Pd/C催化剂的3.6倍，催化耐久性极大提升；.（4）制备了垂直取向的石墨烯-Fe2P非贵金属催化剂，在析氢方面表现出了优异的性能，电流密度为10 mA cm−2时过电位低至101 mV，Tafel 斜率为 55.2 mVdec−1, 交换电流密度为0.146 mA cm−2；.（5）采用一步电沉积方法合成出三维网络结构的还原态氧化石墨烯-碳纳米管复合材料（rGO@CNTs），作为Pd、Cu-Pt核-壳结构纳米粒子的载体，表现出了优异的甲醇电催化性能，如Pd- rGO@CNTs对甲醇电催化氧化的质量活性是商业Pd/C催化剂的7.47倍；.本项目设计了高效石墨烯基电催化剂的新形貌、提出了电化学原位可控制备的新技术和石墨烯基电催化剂稳定负载的新思路。