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

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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.