Speaker: Valerii Okatenko, Skolkovo Institute of Science and Technology, Center for Electrochemical Energy Storage, Russia.
Title: Oxide materials with tetrahedrally coordinated d-metal as bifunctional catalysts for oxygen reduction and oxygen evolution reactions.
Abstract: Alkaline fuel cells are energy storage devices which store energy by decomposing water into hydrogen and oxygen (oxygen evolution reaction, OER,) and generate it by the oxidation of hydrogen producing water (oxygen reduction reaction, ORR). The practical application of these systems is hampered by slow kinetics of OER and ORR. This problem can be solved by usage of bifunctional catalyst, which is equally effective for both reactions. Modern catalysts (precious metals and complex d-metal oxides) have disadvantages, mainly related to their high cost and insufficient electrocatalytic efficiency of metal oxides in OER. Investigated oxide compounds usually have octahedrally coordinated d-metal in their crystal structure. Lattice-oxygen mediated mechanism (LOM), introduced by K. Stevenson’s group, is one of the proposed mechanisms for oxide catalysts OER and ORR and involves processes which include oxygen vacancies transformation.
That leads to the assumption that oxygen non-stoichiometry is desired feature of the catalyst’s crystal structure and can facilitate the processes of oxygen exchange. My work is aimed at the investigation of tetrahedrally-coordinated d-metal oxide materials as bifunctional catalysts. In particular, YBaCo4O7+δ and its derivatives are the point of focus, as the compound possesses high oxygen non-stoichiometry index (up to 1.5) and high electronic conductivity (σ ~ 2,5 S/cm at 50°C). Mainly the aspects of synthesis process will be covered in the talk.
Speaker: Daria Burova, Skolkovo Institute of Science and Technology, Center for Electrochemical Energy Storage, Russia.
Title: Microwave-assisted hydrothermal syntesis of NASICON-based cathode materials for Na-ion batteries.
Abstract: Na-ion batteries are a rapidly developing technology of electrochemical energy storage, which, in its commercial appeal, can be a worthy competition for the already widely used Li-ion technology. Microwave hydrothermal methods of the cathode materials synthesis with the NASICON-type structure Na3V2(PO4)2F3 (NVPF) and its derivatives are developed. The microwave hydrothermal synthesis was carried out with the Anton Paar Microwave reactor. The choice of this method is due to its ability to provide control over the chemical composition and microstructure of the product by varying a large number of experimental parameters. This will make it possible to obtain a range of materials with different morphological and microstructural characteristics. We succeeded in preparation of several cathode materials based on mixed vanadium sodium fluorophosphate Na3V2(PO4)2F3-xOx and solid solutions Na3V2-yMy(PO4) 2F3-xOx (M=Fe, Mn). In experiments we varied temperature (from 180 C to 220 C) and time (from 15 to 30 minutes). The obtained materials were characterized by various methods.
Date: February 7, 2018
Place: TPOC-3, Nobel str., Blue Building, 4th floor, Room 404CL.