Complex ferrite thin films for photoelectrochemical water splitting

Abstract

The traditional energy consumption that relies on fossil fuels has triggered a
number of issues, such as excessive carbon dioxide emission and poor sustainability.
Solar energy as a promising renewable source permits a free, universal, and secure
energy access. Photoelectrochemical water splitting technology can convert it into
solar fuel, achieving the effective usage of solar energy, which opens new avenues for
the transformation of the global energy system.
Transition metal oxide absorbers have made rapid progress in the field of
photoelectrochemical (PEC) water splitting over the past few decades, primarily due
to their chemical stability, low cost and tunability of electronic properties. However,
numerous formidable challenges obstruct their development in viable and scalable
PEC water splitting technology. The investigation of ferrite-based ternary oxides,
LaFeO3 and GaFeO3 for PEC water splitting is targeted in this thesis. A series of
strategies for the innovation of LaFeO3 photocathode are presented from the
modification of surface and the tuning of bulk electronic structure. The deposition of
TiO2 film as a hole blocking layer and heterojunction on LaFeO3 leads to the
photocurrent onset potential for the hydrogen evolution reaction of +1.47 V vs RHE,
which is one of the most positive values reported for a single absorber. The surface
co-catalyst loading also generates a 10-fold increase in the photocurrent responses,
compared with pristine LaFeO3. With regards to bulk tuning, the substitution of
divalent alkaline-earth metal cations into LaFeO3 thin films results in changes in the
electronic structure with a strong impact in PEC performance, achieving more than 3
times increase in the external quantum efficiency for solar oxygen reduction. Finally,
a novel ferrite-based photoanode, GaFeO3 is discovered for the first time. The
structural, optical, and PEC properties of GaFeO3 are systemically reported under the
combination of theoretical and experimental studies. These findings have important
implications on materials design in the field of solar energy conversion

Date of Award	26 Nov 2020
Original language	English
Awarding Institution	University of Bristol
Supervisor	David J Fermin (Supervisor)