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2. Manganese oxide catalysts for secondary zinc air batteries: from

Author

Mainar, Aroa R., Colmenares, Luis C., Leonet, Olatz, Alcaide, Francisco, Iruin, Juan J., Weinberger, Stephan, Hacker, Viktor, Iruin, Elena, Urdanpilleta, Idoia, Blazquez, J. Alberto, and European Commission

Subjects
Bifunctional air electrode, Manganese oxide based catalysts (MnxOy), Secondary zinc-air battery, Oxygen evolution reaction (OER), Oxygen reduction reaction (ORR)
Abstract

An efficient, durable and low cost air cathode with low polarization between the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential for a high performance and durable secondary zinc-air battery. Different valence states and morphologies of MnxOy catalysts were synthetized via thermal treatment of EMD (generating Mn2O3 and Mn3O4) and acid digestion of synthetized Mn2O3 (producing a-MnO2) in order to develop an efficient Bifunctional Air Electrode (BAE). Change in the ratio H+ to Mn2O3 during the acid digestion affects the sample microporosity, the crystallographic plane distribution, as well as the physical and chemical adsorbed water which was related to defects, i.e. cation vacancies (Mn4+) and Mn3+. These characteristics were discussed and linked to the electrocatalytic activity. The best ORR performing catalyst was that with the higher surface water content (associated to material BET surface area) and a (310) surface as the 2nd more contributing plane (after 211). On the other hand, the catalyst with the higher structural water and with (110) and (200) crystallographic planes being the most intensity contributors (after 211) was the most OER active material. In this work, it was able to find a relationship between catalyst structure and air-efficiency through a volcano-like relationship between air-efficiency and surface water content. Air-efficiency (also take as round-efficiency discharge/charge in battery context) can be taken as a good descriptor of potentially good materials for Zn-Air secondary batteries technology. In this term, we were able to prepare a Bifunctional Air Electrode based on the selected a-MnO2 sample which demonstrated a roundefficiency of 53%, a DV around 1 V and a neglected loss of the charge potential (about 2.1 V) over the entire lifecycle test (more 200 cycles over 30 hours) with a capacity retention superior to 95%. European Commission H2020: Proyecto ZAS “Zinc Air Secondary innovative nanotech based batteries for efficient energy storage” (Grant Agreement 646186)

Published
2017

3. Novel ultrathin composite membranes of Nafion/PVA for PEMFCs

Author

Universitat Politècnica de València. Departamento de Termodinámica Aplicada - Departament de Termodinàmica Aplicada, Universitat Politècnica de València. Departamento de Ingeniería Mecánica y de Materiales - Departament d'Enginyeria Mecànica i de Materials, European Commission, Generalitat Valenciana, Mollá Romano, Sergio, Compañ Moreno, Vicente, Giménez Torres, Enrique, Blazquez, Alberto, Urdanpilleta, Idoia, Universitat Politècnica de València. Departamento de Termodinámica Aplicada - Departament de Termodinàmica Aplicada, Universitat Politècnica de València. Departamento de Ingeniería Mecánica y de Materiales - Departament d'Enginyeria Mecànica i de Materials, European Commission, Generalitat Valenciana, Mollá Romano, Sergio, Compañ Moreno, Vicente, Giménez Torres, Enrique, Blazquez, Alberto, and Urdanpilleta, Idoia

Abstract

The electrospinning approach is an easy and useful method to fabricate porous supports with tailored properties for the preparation of impregnated membranes with enhanced characteristics. Therein, this technique was used to obtain polyvinyl alcohol (PVA) nanofiber mats in which Nafion (R) polymer was infiltrated. These Nafion/PVA membranes were characterized in their mechanical properties, proton conductivity and fuel cell performance. Conductivity of the composite membranes was below the showed by pristine Nafion (R) due to the non-ionic conducting behaviour of the PVA phase, although the incorporation of the PVA nanofibers strongly reinforced the mechanical properties of the membranes. Measurements carried out in a single cell fed with H-2/Air confirmed the high performance exhibited by a 19 mu m thick nanofiber reinforced membrane owing to its low ionic resistance. These reasons make ultrathin (<20 mu m) Nafion/PVA composite membranes promising candidates as low cost ion-exchange membranes for fuel cell applications.

Published
2011

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