Show simple item record

Files in this item

Thumbnail

Item metadata

dc.contributor.advisorIrvine, John T. S.
dc.contributor.authorNeagu, Dragos
dc.coverage.spatial257en_US
dc.date.accessioned2013-06-04T16:11:34Z
dc.date.available2013-06-04T16:11:34Z
dc.date.issued2013-06-26
dc.identifieruk.bl.ethos.574803
dc.identifier.urihttp://hdl.handle.net/10023/3606
dc.description.abstractThe development of technologies that enable efficient and reliable energy inter-conversion and storage is of key importance for tempering the intermittent availability of renewable energy sources, and thus for developing an energy economy based on sustainable, clean energy production. Solid oxide electrolysis cells (SOECs) may be used to store excess electrical energy as hydrogen, while solid oxide fuel cells (SOFCs) could convert back hydrogen into electricity, thus balancing energy availability and demand. However, the current state-of-the-art hydrogen electrode used in both SOECs and SOFCs, the Ni-yttria-stabilised zirconia cermet (Ni-YSZ), is unreliable in conjunction with intermittent energy sources, in particular due to its innate redox instability. This thesis explores the fundamental properties of various inherently redox stable A-site deficient titanate perovskite systems (A1-αBO3, B = Ti), seeking to uncover the principles that enhance their properties so that they may be used to replace Ni-YSZ. In particular, this work demonstrates that the versatility of perovskites with respect to the introduction of lattice defects such as vacancies and cation substitutions enables considerable improvements in the extent of reduction, electronic conductivity and overall electrochemical activity. Most importantly, the defect chemistry context set by the presence of A-site vacancies was found to trigger the exsolution of electrocatalytically active nanoparticles from the parent perovskite, upon reduction. This is an entirely new phenomenon which was explored and exploited throughout this study to produce perovskite surfaces decorated with uniformly distributed catalytically active nanoparticles. As demonstrated in this study, the exsolution phenomenon excels in terms of producing nanoparticles with uniform size, distribution, diverse composition and ‘unconventional’ surface anchorage. The resulting enhanced properties, and especially the exsolution phenomenon, contributed coherently towards improving the suitability of the perovskites developed here towards their application as hydrogen electrode materials. Consequently, when integrated into SOEC button cells as hydrogen electrodes, they exhibited a step-change increase in performance compared to other perovskites considered to date. Many of the principles and perovskite defect chemistry explored and exemplified in this study on perovskite titanates may be extended to other perovskites as well. In particular the advanced control and understanding achieved in this work over the exsolution phenomenon may inspire the formulation of new and sophisticated oxide materials with advanced functionality.en_US
dc.language.isoenen_US
dc.publisherUniversity of St Andrews
dc.subjectPerovskitesen_US
dc.subjectMicrostructuresen_US
dc.subjectDefect chemistryen_US
dc.subjectNonstoichiometryen_US
dc.subjectElectrolysisen_US
dc.subjectSolid oxide steam electrolysisen_US
dc.subjectExsolutionen_US
dc.subjectNanoparticlesen_US
dc.subject.lccQD181.T6N4
dc.subject.lcshPerovskite--Propertiesen_US
dc.subject.lcshTitanates--Propertiesen_US
dc.subject.lcshOxidation-reduction reactionen_US
dc.subject.lcshNanoparticlesen_US
dc.subject.lcshElectrodes, Hydrogen--Materialsen_US
dc.titleMaterials and microstructures for high temperature electrochemical devices through control of perovskite defect chemistryen_US
dc.typeThesisen_US
dc.type.qualificationlevelDoctoralen_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US
dc.publisher.institutionThe University of St Andrewsen_US


This item appears in the following Collection(s)

Show simple item record