Development of novel photocatalytic materials by magnetron sputtering for photoelectrochemical hydrogen production via solar activated water splitting

Pomone, Thomas (2025) Development of novel photocatalytic materials by magnetron sputtering for photoelectrochemical hydrogen production via solar activated water splitting. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Hydrogen is a promising green source of energy, and its use could be one of the solutions against the global threats such as global warming. However, its current production ways mainly use fossil fuels in different processes, releasing a high amount of greenhouse gases. There is then a need to turn to renewable and sustainable ways to produce hydrogen. Among those methods, photoelectrochemical water splitting appears to be an interesting alternative, as it relies on the use of the most renewable and abundant source of energy on Earth (solar energy) to produce hydrogen from the water molecule H2O, the most abundant source of hydrogen on Earth. To use photoelectrochemical water splitting, photocatalyst semiconductors must be produced. The most common and studied photocatalyst is titanium dioxide (TiO2), but it is rather limited by its bandgap, reducing its absorption properties to the UV part of the solar spectrum. Novel photocatalysts, such as BiVO4 and CuBi2O4, are more and more studied as candidates to be used as photoelectrodes. In this work, both BiVO4 and CuBi2O4 photocatalysts were produced using pulsed direct current reactive magnetron co-sputtering to be studied as visible light active photoelectrodes in a PEC tandem cell. Then, the produced materials were studied by several analytical techniques to determine their crystallinity (XRD, Raman Spectroscopy), their morphology (SEM, 3D Optical profilometry, AFM) or their chemical composition (EDX, XPS). Their photocatalytic abilities under UV irradiation were successfully assessed by methylene blue dye degradation tests. Their photoelectrochemical properties were assessed in a PEC cell to study the oxygen evolution reaction, the proton reduction reaction and the overall water splitting reaction. Monoclinic scheelite BiVO4 was identified by XRD and Raman analysis, with impressive performances regarding MB dye degradation and photocurrent production. Tetragonal CuBi2O4 was also successfully produced as an efficient photocathode. Both materials present similar behaviour regarding their efficiencies, due to the presence of oxygen vacancies implemented in the lattice during the production process. It results in increasing their charge transport efficiency but does not enable them to have a good charge transfer efficiency. This piece of work describes the use of reactive magnetron co-sputtering to deposit efficient photocatalytic coatings for photoelectrochemical purposes, with a study of the production parameters to determine the optimised deposition conditions. The photoelectrodes produced were used to study a first approach for a PEC tandem cell to study the production of hydrogen via solar activated water splitting. The results of this work address the viability and the challenges faced by this process.