Layered Transition Metal Oxynitrides for Solar Water Splitting
By Shivalingayya Gaddimath
The overexploitation of fossil fuels, rising greenhouse gas emissions, and global warming have intensified the search for renewable and sustainable energy sources, such as wind, solar, and biomass. Fossil fuels  including coal, oil, and natural gas are finite and release harmful pollutants, limiting their long-term viability in industrial applications, power generation, and transportation. Considerable research has focused on mitigating energy scarcity and environmental degradation by harnessing clean energy alternatives. Hydrogen (H2) energy is a promising candidate for achieving carbon-free energy conversion and building a sustainable society due to its high energy density, low molecular weight, abundance, and clean combustion. Among various hydrogen production methods, solar water splitting is a sustainable approach that directly splits water (H2O) into H2 and O2 using sunlight. Solar water splitting involves three key steps: (1) photon absorption and electron excitation from the valence band to the conduction band, generating electron-hole pairs, (2) charge separation and migration to active sites, and (3) redox reactions. The process consists of two half-reactions: hydrogen evolution reaction (HER) at the photocathode and oxygen evolution reaction (OER) at the photoanode. However, OER is a major bottleneck due to its sluggish reaction kinetics, requiring high energy input and expensive catalysts to facilitate the four-electron-involved oxidation process. Transition metal oxynitrides have emerged as promising photocatalysts due to their characteristic optoelectronic properties, strong visible-light absorption, small optical band gap energy, suitable band structures, and chemical stability. Particularly, two-dimensional layered oxynitrides possess several advantages, such as enhanced charge separation, minimized recombination losses, and improved efficiency compared to three-dimensional oxynitrides (AB(O,N)3). Additionally, their high crystallinity, two-dimensional nature, large surface area, high conductivity, and defect tolerance can further enhance their solar water-splitting activity. However, the main challenges remain in developing novel transition metal oxynitrides with high efficiency, long-term stability, and scalability. Therefore, our research aims to explore new members of two-dimensional layered oxynitrides, their synthesis methods, crystal structures, various properties, and solar water splitting activity for green hydrogen generation.
Supervisor: Mirabbos Khujamberdiev

By Mads Nibe Larsen
Infrared thermography is an imaging technique that records long-wave infrared light (8 – 14 µm) and it is often used for remote temperature determination of objects by measuring the amount of thermal radiation they give off. However, different materials have different emission spectra, and the camera must be calibrated to the specific material being imaged. A hyperspectral thermal imaging system can record spectra of every element in the scene, making it possible to segregate multiple materials simultaneously and determine their temperature. This project utilizes a first-order scanning Fabry-Pérot Interferometer (FPI) combined with a thermal camera to capture hyperspectral thermal images. The objective of the project can be split in two: Firstly, an existing prototype of the imaging system must be improved enough that it can become the world’s first commercially available FPI based hyperspectral thermal camera. This includes integration of RGB data in order to incorporate parts of the visible spectrum for improved data analysis. Furthermore, since hyperspectral imaging in the thermal regime is a relatively new and untested technique, finding new applications and associated data analysis tools is a priority. Examples could be detecting and identifying different organic gasses or detect wear and defects in buildings. Secondly, a new thermal radiation sensor will be developed. The highest performing commercially available solutions are very expensive and require cryogenic cooling such as Mercury Cadmium Telluride (MCT) detectors. Microbolometers are a less expensive alternative which do not require additional cooling, but they are, however, much less sensitive. The aim is to fabricate an uncooled graphene field-effect transistor, which utilizes the excellent bolometric properties of graphene and combines it with a partially reflecting Bragg mirror. The graphene is suspended inside a reflecting cavity formed by the mirror and a gold coated substrate, which allow incoming radiation to pass through the graphene multiple times, hereby increasing the probability of absorption. The aim is to fabricate a single pixel detector which will indicate the feasibility of future development of an entire graphene-based focal plane array. This is an industrial PhD-project carried out as a collaboration between Newtec Engineering A/S and SDU.
Supervisor: Jakob Kjelstrup-Hansen