Chemical Vapour Deposition of Metal Oxide Photoelectrode Materials for Water-Splitting Applications

Abstract

The research described in this dissertation has been concerned with the synthesis and characterisation of precursors for the chemical vapour deposition of metal oxide thin films, targeting nanostructured morphologies that can facilitate a high surface-area-to-volume ratio. The interest in these materials was for their utilisation as photoanode materials in photoelectrochemical cells, which can be used to produce a sustainable source of hydrogen from water-splitting.

Chapter 1—Introduction: background as to why new, sustainable energy sources are required, and what characteristics an energy source must have to be considered sustainable. The fundamentals of semiconductor materials in the context of photoelectrochemical water-splitting will be covered, including material selection for devices, and the basics of assessing device performance.

Chapter 2—Iron oxide: novel precursors of the iron(II) β-ketoiminate and iron(III) tripodal alkoxide classes were synthesised and used to deposit α-Fe2O3 by aerosol-assisted chemical vapour deposition. Films produced by the iron(III) tripodal alkoxide precursors performed better under front-side illumination, but produced lower overall photocurrent densities. Neither of the precursors produced films with beneficial nanostructured morphologies.

Chapter 3—Bismuth vanadate: novel precursors for the aerosol-assisted chemical vapour deposition of BiVO4 were synthesised and used to grow nanostructured, phase-pure monoclinic scheelite BiVO4. The BiVO4 films produced a photocurrent density of 1.23mAcm−2 at 1.23V vs. normal hydrogen electrode under simulated sunlight. To the author’s knowledge, this is the highest photocurrent density produced by chemical vapour deposition-grown BiVO4 to date.

Chapter 4—Tungsten-doped bismuth vanadate: a novel precursor suitable for tungsten doping the BiVO4 films reported in chapter 3 was synthesised. The introduction of this precursor did not disrupt the nanostructured morphology, but did retard the growth rate of the films. The front-side illumination performance was significantly improved by the tungsten doping, most likely due to increased electron mobility and electron-hole separation.

Date of Award	22 Jun 2022
Original language	English
Awarding Institution	University of Bath
Supervisor	Andrew Johnson (Supervisor) & Michael Hill (Supervisor)