基于氧化石墨烯层层自组装和模板法构筑石墨烯/无机纳米颗粒空心复合微球及其催化性能研究

Due to the unique structure and properties of graphene, its applications in a broad range of research fields such as catalysis, sensing and battery were extensively explored, hence, it is of great importance and significance to develop graphene-based functional materials and composite materials. In the present project, a series of graphene-based catalytic materials were fabricated on the basis of layer-by-layer (LbL) self-assembly of graphene oxide and template method. That is, graphene oxide with opposite surface charge and nanometer size ( ca. 50 nm ) was alternately assembled on the surface of cationic polyelectrolyte (PDDA) modified silica microsphere through LbL process under ultrasonicationon; then inorganic nanoparticles (such as metal oxide nanoparticles, metal sulfide nanoparticles, noble metal nanoparticles etc.) were deposited on the surface of the resultant composite microspheres; afterwards, the graphene oxide component in the composite microspheres was reduced to graphene by chemical reductant or via hydrothermal process; finally, by removal of the inner silica core, graphene/inorganic-nanoparticle composite hollow microspheres with high dispersity and surface area were obtained, whose catalytic properties on catalytic degradation of organic dyes and phenol, catalytic reduction of 4-nitrophenol, electrocatalytic oxidation of methanol, as well as hydrogen production from water photosplitting were also systematically investigated. The current study is able to establish the basis for the assembly of graphene oxide on the substrate with more complicated morphologies, and open a door to fabricate graphene-based multifunctional composite materials with high dispersity and complicated morphologies.

石墨烯独特的结构和性质，使其在催化、传感、电池等众多研究领域得以应用，发展基于石墨烯的功能材料和复合材料具有重要科学价值和现实意义。本项目拟通过氧化石墨烯的层层自组装并借助模板法设计构筑基于石墨烯的催化材料，即以阳离子聚电解质修饰的SiO2微球为模板，在超声条件下先于其表面交替组装带有相反电荷的小尺寸氧化石墨烯片(平均径向尺寸约50 nm)，再引入无机纳米颗粒(如金属氧化物、金属硫化物、贵金属纳米颗粒)，然后通过还原剂或水热过程将氧化石墨烯组分还原成石墨烯，之后再溶解去除SiO2内核，从而制备得到分散性好、比表面积大的石墨烯/无机纳米颗粒空心复合微球，并系统研究其对有机染料、酚类物质催化降解，对4-硝基苯酚催化还原，对甲醇电催化氧化，对光解水产氢的催化性能。该研究可以为氧化石墨烯在形貌更为复杂基底表面的组装奠定基础，为制备高分散性、复杂形貌的基于石墨烯多功能复合材料提供一种新的思路和方法。

在以往的报道中，人们常将各种纳米颗粒负载于尺寸较大的石墨烯片(径向尺寸为微米级)的表面来合成石墨烯/纳米颗粒复合材料。如此一来，在其制备过程中，纳米颗粒作为客体物质沉积或生长于作为主体物质的石墨烯表面，石墨烯充当了基底或支撑材料的角色。采取这种策略不但容易引发聚集行为，而且也不利于制备形貌更为复杂、性能更为优异的石墨烯基复合材料。相比之下，在微米或者纳米尺度的固体微基底表面引入石墨烯或氧化石墨烯来构筑石墨烯基复合材料的研究则相对较少。基于这一研究现状，本项目借助强力超声作用，实现了小尺寸氧化石墨烯（径向尺寸小于200 nm）在正电化二氧化硅微球表面的静电自组装，并有效克服了常见的聚集和粘连现象，首先获得了具有优异水分散性的二氧化硅/氧化石墨烯复合微球。通过以其为基底或模板，再采用原位还原、水热、溶剂热等手段进一步成功构筑了多种石墨烯基复合材料包括兼具良好水分散性和优异催化活性的树莓状二氧化硅/石墨烯/银纳米颗粒复合微球、二氧化钛/石墨烯、二硫化钼/石墨烯、硅酸镍氢氧化物/石墨烯、二氧化锰空心微球等，并应用于非均相的有机催化反应、染料的光催化降解、超级电容器等领域，且都表现出出色的催化效果或电化学性能。因此，通过本项目研究一方面实际上开发了一种通过氧化石墨烯在固体微基底表面的自组装来构建具有独特结构、复杂形貌及优异性能的石墨烯基复合材料的新方法；另一方面在本项目研究中我们合成了上述多种石墨烯基复合材料，并应用于多个领域，其表现(催化或电化学性能)已可媲美甚至超过许多已经公开报道的同类型材料的性能，因而丰富了石墨烯基复合材料的种类，拓展了其应用范围，具有良好的研究价值和应用潜能。