Controlled Synthesis of Transition Metal Oxide Mesocrystals on Graphene Oxide and the Application in Electrocatalysis

氧还原反应（ORR）是氧电极反应的阴极分支，动力学缓慢，是限制金属-空气电池、燃料电池等电化学能量转换和储存应用的主要因素之一。铂的稀缺性和高成本阻碍了它们的大规模商业化，并且寻找高效和廉价的非贵金属催化剂是优选的。过渡金属氧化物/碳复合材料表现出固有的ORR活性。即便如此，与Pt相比，这些报道的材料显示出相形见绌的活性和耐久性。介晶是由晶体学取向的纳米晶体构成的一类新型超结构材料，具有有序的超结构，由Helmut Cölfen教授（德国申请人）首先提出。由于介晶具有高孔隙率和暴露高能晶面的优点，它们在与能源相关的应用中吸引了大量的研究兴趣。中国申请人（黄明华副教授）正在领导一个研究小组，以制造基于过渡金属氧化物的催化剂，并研究其对ORR的电催化活性。她的团队开发了一系列具有高活性和良好稳定性的空心碳球/金属氧化物纳米材料。德国申请人（Helmut Cölfen教授）及其团队在生物和生物启发矿化中的无机和有机组分以及研究各种介晶的生长机制和结构表征方面具有长期和杰出的背景。2007-2008年，中国申请人是赫尔穆特·科尔芬教授小组的洪堡研究员。聚合物编码纳米颗粒组织的生物启发矿化原理已被转移到诱导芳香分子的自组装。在该项目中，他们将专注于在氧化石墨烯片上控制过渡金属氧化物介晶的生长，并研究最终金属氧化物介晶-石墨烯催化剂的ORR催化活性，特别是阐明生长机制并深入研究催化剂结构与活性之间的关系。

The oxygen reduction reaction (ORR), the cathodic branch of oxygen electrode reactions with sluggish kinetics, is considered as one of the limiting factors for the application of electrochemical energy conversion and storage such as metal-air batteries and fuel cells. The scarcity and high cost of Pt are impeding their mass commercialization, and searching for efficient and cheap non-precious-metal catalysts is preferable. Transition metal oxide/carbon composites exhibit intrinsic activity for ORR. Even so, compared with Pt, these reported materials show dwarfed activity and durability. Mesocrystals, constructed by crystallographically oriented nanocrystals, can be regarded as a new class of superstructured materials with an available ordered superstructure, which was first proposed by Prof. Helmut Cölfen (German applicant). Due to the advantages of mesocrystals with high porosity and exposition of high energy crystal faces, they have attracted a great deal of research interest in energy-related applications. The Chinese applicant (Associated Prof. Minghua Huang) is leading a research group to fabricate transition metal oxide-based catalysts and to study their electrocatalytic activity for ORR. Her team has developed a series of hollow carbon sphere/metal oxide nanomaterials with high activity and good stability. The German applicant (Prof. Helmut Cölfen) and his group have a long and distinguished background on the inorganic and organic components in bio- and bioinspired mineralization as well as on investigating growth mechanisms and structure characterization of various mesocrystals. In 2007-2008, the Chinese applicant was a Humboldt Fellow in the group of Prof. Helmut Cölfen. The bioinspired mineralization principle of polymer-coded nanoparticle organization has been transferred to induce the self-assembly of an aromatic molecule. In this project, they will focus on the controlled growth of transition metal oxide mesocrystals on graphene oxide sheets and investigation of the ORR catalytic activity of the final metal oxide mesocrystal-graphene catalysts, especially on clarifying the growth mechanism and providing thorough investigation of the relationship between the catalyst structures and the activities.