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An Oxofluoride Catalyst Comprised of Transition Metals and a Metalloid for Application in Water Oxidation
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
Vise andre og tillknytning
2015 (engelsk)Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, nr 37, s. 12991-12995Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The application of the recently discovered oxofluoride solid solution (CoxNi1-x)(3)Sb4O6F6 as a catalyst for water oxidation is demonstrated. The phase exhibits a cubic arrangement of the active metal that forms oxo bridges to the metalloid with possible catalytic participation. The Co3Sb4O6F6 compound proved to be capable of catalyzing 2H(2)OO(2)+4H(+)+4e(-) at 0.33V electrochemical and 0.39V chemical overpotential with a TOF of 4.410(-3), whereas Ni3Sb4O6F6 needs a higher overpotential. Relatively large crystal cubes (0.3-0.5mm) are easily synthesized and readily handled as they demonstrate both chemical resistance to wear after repeated insitu tests under experimental conditions, and have a mechanical hardness of 270V0.1 using Vickers indentation. The combined properties of this compound offer a potential technical advantage for incorporation to a catalytic interface in future sustainable fuel production.

sted, utgiver, år, opplag, sider
2015. Vol. 21, nr 37, s. 12991-12995
Emneord [en]
cobalt, nickel, oxofluorides, solid solutions, water oxidation catalysts
HSV kategori
Forskningsprogram
oorganisk kemi
Identifikatorer
URN: urn:nbn:se:su:diva-136190DOI: 10.1002/chem.201501452ISI: 000360583000022PubMedID: 26219925OAI: oai:DiVA.org:su-136190DiVA, id: diva2:1050891
Tilgjengelig fra: 2016-11-30 Laget: 2016-11-30 Sist oppdatert: 2017-10-18bibliografisk kontrollert
Inngår i avhandling
1. Water splitting by heterogeneous catalysis
Åpne denne publikasjonen i ny fane eller vindu >>Water splitting by heterogeneous catalysis
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

A sustainable solution for meeting the energy demands at our planet is by utilizing wind-, solar-, wave-, thermal-, biomass- and hydroelectric power. These renewable and CO2 emission-free energy sources are highly variable in terms of spatial and temporal availability over the Earth, introducing the need for an appropriate method of storing and carrying energy. Hydrogen has gained significant attention as an energy storage- and carrier media because of the high energy density that is exploited within the ‘power-to-gas’ process chain. A robust way of producing sustainable hydrogen is via electrochemical water splitting.

In this work the search for new heterogeneous catalyst materials with the aim of increasing energy efficiency in water splitting has involved methods of both electrochemical water splitting and chemical water oxidation. Some 21 compounds including metal- oxides, oxofluorides, oxochlorides, hydroxide and metals have been evaluated as catalysts. Two of these were synthesized directly onto conductive backbones by hydrothermal methods. Dedicated electrochemical cells were constructed for appropriate analysis of reactions, with one cell simulating an upscale unit accounting for realistic large scale applications; in this cell gaseous products are quantified by use of mass spectrometry. Parameters such as real time faradaic efficiency, production of H2 and O2 in relation to power input or overpotentials, Tafel slopes, exchange current density and electrochemical active surface area as well as turnover numbers and turnover frequencies have been evaluated.

Solubility, possible side reactions, the role of the oxidation state of catalytically active elements and the nature of the outermost active surface layer of the catalyst are discussed. It was concluded that metal oxides are less efficient than metal based catalysts, both in terms of energy efficiency and in terms of electrode preparation methods intended for long time operation. The most efficient material was Ni-Fe hydroxide electrodeposited onto Ni metal foam as conductive backbone. Among the other catalysts, Co3Sb4O6F6 was of particular interest because the compound incorporate a metalloid (Sb) and redox inert F and yet show pronounced catalytic performance.

In addition, performance of materials in water splitting catalysis has been discussed on the basis of results from electron microscopy, solubility experiments and X-ray diffraction data.

sted, utgiver, år, opplag, sider
Stockholm: Department of Materials and Environmental Chemistry, Stockholm University, 2017. s. 93
Emneord
Faradaic efficiency, electrocatalysis, electrolysis, water oxidation, hydrogen reduction, H2, O2, mass spectrometry
HSV kategori
Forskningsprogram
oorganisk kemi
Identifikatorer
urn:nbn:se:su:diva-148181 (URN)978-91-7797-039-2 (ISBN)978-91-7797-040-8 (ISBN)
Disputas
2017-12-06, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2017-11-13 Laget: 2017-10-17 Sist oppdatert: 2017-11-03bibliografisk kontrollert

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