基于石墨烯及导电高分子复合的三维多孔电极材料的构筑及其电催化性能研究

One of the major challenges in the successful commercialization of low temperature fuel cells is the development of cost-effective anode catalysts with high catalytic activity, efficiency, and durability. In this context, the present study aims at preparing a novel three-dimentional (3D) porous composite electrocatalyst, consisting of graphene, conducting polymers and noble metal nanoparticles by different methods. As-prepared composites are expected to retain the excellent conductive properties, high specific surface area and stability of graphene, the good processability and porous structures of conducting polymers, and the high catalytic activity of noble metal nanoparticles. The synergistic interaction between graphene and conducting polymers can effectively prevent the agglomeration of graphene sheets and enhance the electrical conductivity and stability of conducting polymers, thus being beneficial to the high dispersion and stability of noble metal nanoparticles. Especially, for the 3D porous composites, network- or granular-structured conducting polymers are dispersed between graphene layers forming a "sandwich" structure, which will consequently modulate the 3D distribution of metal nanoparticles in the composites as well as their high catalytic efficiency. In this project, special attention will be focused on the interactions between the composite supports and the deposited noble metal nanoparticles. The correlations between the nanoarchitectures and functional properties and the effects of different preparation methods and conditions on the catalytic performance of the composite catalysts will also be studied in detail. We suggest that the accomplishment of this project will provide valuable fundamental knowledge for the development of novel composite electrode materials for fuel cells in experiments and theory.

如何提高阳极催化剂催化活性、稳定性及贵金属的利用率是低温燃料电池产业化的关键因素之一。本项目设想利用石墨烯、导电高分子及贵金属，构筑新型三维(3D)多孔结构的石墨烯/导电高分子/贵金属复合电极催化剂材料，冀望该复合材料能秉承石墨烯的高导电性、大比表面积及高稳定性，导电高分子优良的可加工性，以及贵金属纳米粒子的高催化活性等优点。优化复合条件，克服石墨烯组装中易层层堆积的难点，提高导电高分子的稳定性，增强纳米粒子在3D多孔结构中的分散性及稳定性。特别是研究电化学方法制备3D多孔结构的石墨烯，利用导电高分子将贵金属纳米粒子均匀分散和稳定在3D结构的表面及缝隙中，从而实现复合催化剂高催化活性及高稳定性。研究3D多孔复合材料与贵金属纳米粒子之间相互作用，以及不同方法和合成条件对3D复合材料催化性能的影响，总结影响复合材料性能的规律及其促进电催化活性的机理，为发展新型复合电极材料提供实验和理论的支持。

该项目实施过程中，我们主要开展了以下面三个方面的研究工作：.（1）还原石墨烯和改性石墨烯负载的贵金属催化剂的电催化氧化性能研究。将PEDOT和GE复合，作为钯催化剂载体，应用在乙醇的电催化氧化上，发现Pd，PEDOT和GE的协同效应可以使乙醇的电催化氧化性能显著增强：Pd纳米粒子高的电化学活性面积及其与PEDOT聚合物之间的协同作用；石墨烯的引入加快了电极表面和电解质之间的电子传递，加强了与PEDOT纳米微球的作用；PEDOT纳米微球则避免了石墨烯的聚集。.（2）氮掺杂石墨烯负载的贵金属催化剂的电催化氧化性能研究。在甲酸的电催化氧化过程中，以氮掺杂石墨烯为载体，其大的比表面积可以提供较多的表面活性位点，加快电子的传输；而以银种子为中间体借助超声辅助制备的有特殊树突结构的中空PtAg纳米复合催化剂，有更大的表面体积比和更低的材料密度，可极大的增强催化活性和维持长久的稳定性。氮掺杂石墨烯负载的中空 PtAg 纳米树突催化剂对甲酸的电催化氧化的催化活性是商业Pt/C催化剂的3.7倍。.（3）石墨烯和二维复合材料负载贵金属催化剂对甲醇的电催化氧化性能研究。利用阳极氧化法在Ti基底表面合成了高度有序的TiO2纳米管阵列，然后通过电沉积方法合成了Pt纳米花点缀的TiO2纳米管，最后通过电化学还原的方法用还原氧化石墨烯修饰Pt-TNTs得到Pt-TNTs/RGO三元纳米复合物。比较Pt-TNTs/RGO和TNTs的紫外可见漫反射光谱发现，Pt-TNTs/RGO吸收带明显红移大约23 nm，拓展至可见光区域，大大提高了复合催化剂对太阳光的利用效率。其次，与电催化过程相比，可见光和RGO的引入，提高了Pt-TNTs/RGO催化剂的电催化活性、抗毒化性和长期稳定性。.通过该项目实施，我们对石墨烯类载体负载的贵金属催化剂性能有了比较清晰的认识，发现石墨烯类载体对贵金属粒子在电催化和光电化学催化性能方面有较大的提升作用，复合材料中诸元间的协同作用是性能提高的关键因素之一，且其在光电化学方面具有更宽广的潜在应用前景。