Perovskite nanofibers for electrochemical and catalysis applications

Abstract

The ever increasing demand for renewable energy encourages people to search for technique creation. The development of efficient materials is of key importance for various reliable technologies, including catalysis, photocatalysis and energy conversion and storage (such as fuel cell, electrolyser and battery). Perovskite attracts much attention because of its versatility and flexibility. However, understanding the relationship among composition, structure (both morphological and crystal) of perovskite is still of a crucial role in tuning the properties of materials. Fibre structure opens new scenarios for designing perovskite-based materials with intriguing properties in this work. This thesis explores the versatility of electrospinning with respect to fabricating various titanium perovskite fibre, from aristotype SrTiO3 to A/B-site co-doping material. The perovskite fibres were employed in photocatalysis, CO oxidation and solid oxide cells. In particular, this work demonstrates that the fibre structure offers a unique platform to observe the surface reconstruction. Besides, the grain-grain connected fiber structure sets a unique context for the cation ordering stabilisation. The continuous fibre structure also render a fast delivering pathway for the B-site cation diffusion. As demonstrated in this study, the exsolution of Ni-cation is faster in fibre structure than powder and bulk materials. The synergetic effect of bi-metal exsolution was also investigated by introducing Fe and Co into the B-site of perovskite. Bi-metal doping was found to enhance the reducibility of the perovskite and facilitate the formation of alloy nanoparticles. Consequently, the egressed bimetallic nanoparticles contribute to an enhanced CO2 electrolysis performance. Furthermore, the interwoven fibres material provides space for reactant transport and acts well as a framework for Pt deposition. The reactive interaction between the Pt nanoparticles and the perovskite support facilitates the exsolution of Ni from the support. The exsolved Ni in turn prompts the in-situ formation of PtNi bimetallic nanoparticles. Controlling and understanding of the formation of the PtNi may inspire the development of a new driven force of exsolution. Moreover, the method developed in this study may be extended to other metals and supports.