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Combinatorial synthesis and high throughput screening of Perovskite Electrocatalysts

Combinatorial synthesis and high throughput screening of Perovskite Electrocatalysts
Combinatorial synthesis and high throughput screening of Perovskite Electrocatalysts
Compositionally graduated films of a SrTi1-xFexO3-y (STFO) perovskite electrocatalyst were successfully prepared by High Throughput Physical Vapour Deposition (HT-PVD). X-ray diffraction measurements confirmed a cubic perovskite structure for all values of x as well as an increase in the cubic lattice parameter with increasing x from 0.392 ± 0.001 nm for SrTiO3 to 0.386 ± 0.001 nm for SrFeO3 in accordance with Vegard’s Law. A Raman mode corresponding to an O-stretching vibration was observed which is disallowed by symmetry in the cubic structure and suggests a localised lattice distortion. The films were highly resistive, < 7 x 10-8 S cm-1, at low x but conductivity increased with increasing x before reaching a plateau at 0.041 S cm-1 for x > 0.75.High electrocatalytic activity towards the oxygen evolution reaction (OER), characterised by over-potentials below 0.2 V, was found for STFO electrode compositions with x > 0.5. The high OER activity was however found to correlate with low electrode stability, consistent with the participation of lattice oxygen in the OER mechanism. This was supported by the observed redox electrochemistry which showed evidence of reversible oxygen intercalation. An optimal electrode composition of SrTi0.5Fe0.5O3-y is recommended as OER activity showed no significant increase for higher Fe content whilst electrode stability decreases. Low electrocatalytic activity towards the oxygen reduction reaction (ORR) was observed for all compositions. The ORR did not occur until after surface reduction of the films suggesting that the surface reduction is required for the creation of active surface sites.The STFO perovskite system was also investigated on Fe doped STO (110) surfaces. A series of reconstructed surfaces were prepared and characterised by low energy electron diffraction (LEED) in agreement with the literature. X-ray photo-electron spectroscopy (XPS) and low energy ion scattering spectroscopy (LEISS) confirmed that Fe doping was successful in incorporation of Fe into the perovskite structure. Fe incorporation was observed to improve the ORR electrocatalytic activity of the surface however no OER electrocatalytic activity was observed
University of Southampton
Rogers, Fiona, Kate
d2becf09-43dc-4550-b06e-ff22a5b581b9
Rogers, Fiona, Kate
d2becf09-43dc-4550-b06e-ff22a5b581b9
Hayden, Brian
aea74f68-2264-4487-9d84-5b12ddbbb331

Rogers, Fiona, Kate (2016) Combinatorial synthesis and high throughput screening of Perovskite Electrocatalysts. University of Southampton, Doctoral Thesis, 279pp.

Record type: Thesis (Doctoral)

Abstract

Compositionally graduated films of a SrTi1-xFexO3-y (STFO) perovskite electrocatalyst were successfully prepared by High Throughput Physical Vapour Deposition (HT-PVD). X-ray diffraction measurements confirmed a cubic perovskite structure for all values of x as well as an increase in the cubic lattice parameter with increasing x from 0.392 ± 0.001 nm for SrTiO3 to 0.386 ± 0.001 nm for SrFeO3 in accordance with Vegard’s Law. A Raman mode corresponding to an O-stretching vibration was observed which is disallowed by symmetry in the cubic structure and suggests a localised lattice distortion. The films were highly resistive, < 7 x 10-8 S cm-1, at low x but conductivity increased with increasing x before reaching a plateau at 0.041 S cm-1 for x > 0.75.High electrocatalytic activity towards the oxygen evolution reaction (OER), characterised by over-potentials below 0.2 V, was found for STFO electrode compositions with x > 0.5. The high OER activity was however found to correlate with low electrode stability, consistent with the participation of lattice oxygen in the OER mechanism. This was supported by the observed redox electrochemistry which showed evidence of reversible oxygen intercalation. An optimal electrode composition of SrTi0.5Fe0.5O3-y is recommended as OER activity showed no significant increase for higher Fe content whilst electrode stability decreases. Low electrocatalytic activity towards the oxygen reduction reaction (ORR) was observed for all compositions. The ORR did not occur until after surface reduction of the films suggesting that the surface reduction is required for the creation of active surface sites.The STFO perovskite system was also investigated on Fe doped STO (110) surfaces. A series of reconstructed surfaces were prepared and characterised by low energy electron diffraction (LEED) in agreement with the literature. X-ray photo-electron spectroscopy (XPS) and low energy ion scattering spectroscopy (LEISS) confirmed that Fe doping was successful in incorporation of Fe into the perovskite structure. Fe incorporation was observed to improve the ORR electrocatalytic activity of the surface however no OER electrocatalytic activity was observed

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Published date: September 2016
Organisations: University of Southampton, Chemistry

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Local EPrints ID: 409725
URI: http://eprints.soton.ac.uk/id/eprint/409725
PURE UUID: fbe6d602-4b5f-4688-b1e0-3d614c315b21
ORCID for Brian Hayden: ORCID iD orcid.org/0000-0002-7762-1812

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Date deposited: 01 Jun 2017 04:07
Last modified: 02 Apr 2020 04:01

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Thesis advisor: Brian Hayden ORCID iD

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