Thesis-2011-SaremiYarahmadi.pdf (9.63 MB)
Download filePreparation and performance of nanostructured iron oxide thin films for solar hydrogen generation
thesis
posted on 2011-02-24, 12:19 authored by Sina Saremi-YarahmadiNowadays, energy and its resources are of prime importance at the global level. During
the last few decades there have been several driving forces for the investigation of new
sources of energy. Hydrogen has long been identified as one of the most promising carriers
of energy. Photoelectrochemical (PEC) water splitting is one of the most promising means
of producing hydrogen through a renewable source. Hematite (α-Fe2O3) is a strong candidate
material as photoelectrode for PEC water splitting as it fulfils most of the selection criteria of
a suitable photocatalyst material for hydrogen generation such as bandgap, chemical and
photelectrochemical stability, and importantly ease of fabrication. This work has explored different preparation techniques for undoped and Si-doped iron
oxide thin films using microwave-assisted and conventional preparation methods. Two
distinct strategies towards improving PEC performance of hematite photoelectrodes were
examined: retaining a finer nanostructure and enhancing the photocatalytic behaviour
through doping.
By depositing thin films using atmospheric pressure chemical vapour deposition
(APCVD) and aerosol-assisted CVD (AACVD) at high temperature, it was shown that a
combination of different factors (such as silicon incorporation into the hematite structure
and formation of lattice defects, along with a nanostructure of small agglomerate/cluster
enhancing hole transportation to the surface) were the contributing factors in improving the
PEC performance in hematite films. The role of the Si-containing precursors and their
consecutive effect on nanostructure of the hematite films were investigated. Further work is
needed to study the decomposition pattern of precursors and consequent effects of Si
additives as well as co-dopants on fundamental physical and electrical properties of hematite
electrodes. In addition, the feasibility of using microwave annealing for the fabrication of iron oxide
thin films prepared by electrodeposition at low temperature was also investigated. Hematite
films showed improved PEC performance when microwave assisted annealing was used.
Microwave heating decreased the annealing temperature by ~40% while the PEC
performance was increased by two-fold. The improved performance is attributed to the
lower processing temperatures and rapidity of the microwave method that help to retain the
nanostructure of the thin films whilst restricting the grain coalescence to a minimum.
Around 60% of the energy can be saved using this low carbon foot-print approach
compared to conventional annealing procedures for the lab-scale preparation of hematite
films – a trait that will have significant implications for scale-up production. The lower
processing temperature requirements of the microwave process can also open up the
possibility of fabricating hematite thin films on conducting, flexible, plastic electronic
substrates.
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Materials
Publisher
© S. Saremi YarahmadiPublication date
2011Notes
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.EThOS Persistent ID
uk.bl.ethos.545735Language
- en