The properties of epitaxially grown 2D materials such as hexagonal boron nitride (hBN) and graphene are highly dependent on the growth mechanism and on the presence of defects in the epitaxial layer. In our study we employ Density Functional Theory (DFT) calculations to examine the epitaxial growth of hBN on a Ru(0001) surface; we aim to develop a detailed understanding of the formation of hBN from borazine. Our results predict the formation of a (3 × 3) meta-stable structure, consistent with results from helium atom scattering experiments. Our findings may have implications for CVD processes, the creation of defect sites and the design of new nanomaterials based on exploiting the growth phases of hBN. We have also investigated the effect of defects on the catalytic activities of hBN. hBN has many advantages for heterogeneous catalysis, including high surface area, high thermal stability, and high durability whilst being more sustainable than the ubiquitously employed precious and transition metal-based catalysts. Through DFT simulations, we have explored metal-free hBN as a valid alternative to precious metal catalysts for producing H2 via the reaction of ammonia with a surface boron and nitrogen divacancy (VBN), achieving a decomposition barrier of 0.52 eV. Furthermore, the reaction of ammonia with epitaxially grown hBN on a Ru(0001) substrate was investigated, and we observed similar NH3 decomposition energy barriers (0.61 eV), but a much more facile H2 desorption barrier (0.69 eV vs 5.89 eV). Next, we intend to explore the possibilities of hydrogenated hBN defects in hydrogenation reactions. Through completing this work, we hope to discover sustainable alternatives to fossil fuels.