AbstractRenewable and sustainable alternatives to fossil fuels are needed to limit the impact of global warming and to meet increasing energy demands. Electricity generation through solar energy storage using metal oxide semiconductors as photoelectrodes within photoelectrochemical (PEC) cells is one such alternative. For example, PEC water reduction can be completed in order to produce H2 which can then be used as a fuel or within fuel cell devices. Finding suitable semiconductors can be challenging with persistent and common limitations arising such as high rates of electron-hole recombination, poor light absorption and poor stability. For example, some metal oxides are restricted due to wide band gaps and hence inactivity in the visible light region, which encompasses about 40 % of the solar light spectrum. Additionally, with reference to photocathodes, there are common issues arising from instability (e.g. Cu2O and Cu2S), thus it is advantageous to investigate alternative materials that have smaller band gaps and are highly stable.
Hence, perovskite oxides (ABO3) such as lanthanum iron oxide (LaFeO3) and praseodymium iron oxide (PrFeO3) have been investigated here, due to their benefits of visible light absorption, abundancy and good stability. The effects of film fabrication method on film quality and ultimate performance had been rarely discussed. In this work, various film fabrication methods have been explored for LaFeO3 photocathodes, including doctor blading, spray pyrolysis of precursors and spin coating with polymer templates. The best overall PEC performance was found for LaFeO3 films prepared through a sacrificial templating method using a non-ionic surfactant, polyoxyethylene octyl phenyl ether (Triton X-100). A photocurrent density of -161±6 µA cm-2 at +0.43 VRHE was recorded, with an impressive onset potential of +1.4 VRHE for cathodic photocurrent, with increased electrochemically active surface area and charge separation compared to other methods. This is a substantial increase on many literature values and is comparable to the highest achieved photocurrent reported. PrFeO3 photocathodes prepared through spray pyrolysis were also examined, which achieved a photocurrent density of -130±0.6 µA cm-2 at +0.43 VRHE with an onset potential of +1.4 VRHE for cathodic photocurrent. This is believed to be the first demonstration of PrFeO3 photocathodes.
|Date of Award||24 Jun 2020|
|Supervisor||Emma Emanuelsson Patterson (Supervisor), Michael Bird (Supervisor), David J. Fermin (Supervisor) & Salvador Eslava (Supervisor)|