Per- and polyfluoroalkyl substances (PFASs) are a growing environmental concern. Efficient methods for degrading PFAS are urgently needed. In this thesis, we apply density functional theory (DFT) to better understand the molecular-scale process of PFAS degradation via catalytic hydrogenation on transition metal surfaces. We systematically investigate the adsorption configuration of PFAS molecules on catalyst surfaces composed of different metals. We find that the orientation of the PFAS molecule influences PFAS adsorption strength and removal rates, as the head group and tail group have a significantly different bonding strength to the surface. Adsorbate-adsorbate interactions between co-adsorbed PFAS molecules can promote PFAS adsorption through van der Waals forces among the tail groups of adjacent PFAS molecules, which can lead to the enhanced co-removal of differing PFAS molecules. Adsorbed hydrogen also influences the PFAS binding orientation by blocking the formation of metal-oxygen bonds between the surface and the PFAS head-group, thus promoting physisorption over chemisorption. Investigation of the hydrogenation mechanism responsible for activating C-F bonds shows that the reaction mechanism also is sensitive to the PFAS adsorption orientation. This mechanistic insight provides strategies for improving catalyst design to maximize PFAS uptake and degradation.