过渡金属掺杂管状rGO载Pd复合结构的可控合成及催化性能研究

Transition metal-doped tubular reduced graphene oxide (rGO) can improve the characteristic of rGO support, which can be seen as a new support of Pd-based catalyst in proton exchange membrane fuel cells and has important academic and practical value. In our proposed work, graphene oxide and transition metal ions are co-reduced by electronchemical method. After the tubular reduced graphene oxide support doped with transition metal is controllably synthesized, small Pd nanoparticles are loaded on the surface of the support. Consequently, the tubular M-rGO/Pd catalysts are obtained. The formation mechanism and control synthesis of M-doped rGO network structure with “C-O-M” bond will be researched. M-doped structure (doping sites, bonding, chemical states, etc.) and rGO structure (multilayer or stack, crystal structure, sp2 bond structure, etc.) will be characterized and analyzed. The comprehensive relationship will be further researched, including the adsorption and desorption properties of the catalyst, reaction paths in electrochemical process, electro-catalytic performance, and the relationship among the adsorption energy, charge transfer, energy band and state density in theoretical simulation. The relationship of d electron transfer, rGO electronic structure change and the interaction among M-rGO-Pd will be researched systematically. Finally, the mechanism on rGO and Pd by adjusting d electronic structure of Pd, improvement support performance, and enhance Pd electrocatalystic will be explored. Finally, the mechanism on the improvement of electrocatalytic performance, which is caused by the interactions among transition metal, rGO and Pd by adjusting d electronic structure of Pd, will be explored. This project will be great helpful in providing the technical support and theory basis for the development of new catalyst with tubular M-rGO support in the future.

利用过渡金属(M)对还原氧化石墨烯(rGO)掺杂并构建管状结构，可改善石墨烯的载体特性，以其作为碱性质子交换膜燃料电池Pd基催化剂的新型载体具有重要的学术与应用价值。本项目采用电化学法使GO与M离子共还原，借助模板可控合成管状M-rGO并负载小尺寸Pd粒子，获得管状M-rGO/Pd复合催化剂。研究M以“C-O-M式”化学键在rGO网状结构中掺杂的形成机理与结构控制方法；对M掺杂结构(掺杂位、键合方式、化学状态等)、rGO结构(多层或叠层、结晶结构、sp2键结构)等进行表征与测试，结合电化学过程吸脱附性能、反应路径、催化性能、以及理论模拟计算中吸附能、电荷转移、能带和态密度等，深入分析Pd的d电子转移、rGO电子结构变化、M-rGO-Pd三者之间构效关系等，探究过渡金属掺杂管状rGO对调整电子结构、改善载体特性、促进Pd催化性能提高的机制，为开发rGO基新型载体催化剂提供技术支持与理论依据。

质子交换膜燃料电池（PEMFC）具有很好的应用前景，然而，高的制造成本和缓慢的反应动力学过程限制了Pt 基催化剂在PEMFC 中的大规模商业化应用，低成本、高性能的非铂催化剂是未来发展PEMFC 催化剂的重要研究方向。由于Pd 在碱性介质中具有较Pt更好的抗CO 中毒性能，Pd基纳米复合催化剂已成为研发碱性PEMFC 非铂催化剂的首选。众所周知，将小尺寸的纳米粒子均匀负载在具有巨大比表面积和良好导电性的载体上可有效降低成本、提高催化活性和改善催化稳定性。因此，寻求理想的新型载体并在表面均匀负载适宜尺寸的催化剂纳米粒子一直是PEMFC的研究重点。本项目通过过渡金属掺杂rGO，利用过渡金属离子与GO发生电化学共还原,或通过水热还原法将过渡金属离子以过渡金属氧化物的形式负载，可控合成了具有高催化性能的过渡金属掺杂（或氧化物改性）rGO载Pd（或Pt）的复合结构催化剂，获得了可控合成这些催化剂的方法；主要开展了以下几个方面的研究：（1）电化学沉积法制备过渡金属M（Fe、Co、Ni等）掺杂的rGO载Pd复合结构催化氧化甲醇的研究；（2）管状Pt-rGO、过渡金属掺杂的rGO载Pd复合结构催化剂的合成及电催化性能研究；（3）Pd/TMxOy-rGO/CFP (TMxOy = Co3O4, Mn3O4, Ni(OH)2)催化剂的制备及电催化性能研究。结果表明：TMxOy不仅可诱导分散Pd纳米粒子在载体TMxOy-rGO表面的锚定，而且显著增强载体TMxOy-rGO与Pd纳米粒子之间的电子效应，进而有效提高了催化剂的催化活性；修饰在rGO表面的TMxOy，相对于Pd更易吸附CO等中间产物，可以减弱催化剂的中毒；阐明了因过渡金属掺杂引起rGO电子结构、载体特性改变，促进活性成分Pd电子转移从而提高电催化性能的机制，为开发低成本、高性能“M-rGO/Pd”新型电催化剂提供技术支持和理论依据。