The making and breaking of bonds involving hydrogen atoms at the surfaces of materials plays a major role in nature. For example, the formation and activation of C-H, N-H, and O-H bonds lies at the heart of heterogeneous catalysis and is no less important to other disciplines such as electrochemistry and astrophysics, not to mention the widely discussed “hydrogen economy” of the future. When dealing with hydrogen, quantum nuclear effects - tunnelling and quantum delocalization - can be significant at room temperature and below. Despite this fact, and despite growing economic and environmental incentives to carry out hydrogenation and dehydrogenation reactions at lower temperatures most theoretical studies neglect the role quantum nuclear effects play in such processes. Here, we will address this by developing and applying ab initio path integral techniques for the rigorous treatment of quantum nuclear effects in elementary diffusion and reaction events at solid surfaces. The path integral formalism of quantum mechanics provides a powerful approach for treating quantum nuclear effects and when done with an ab initio determination of the underlying potential energy surface highly accurate predictions can be achieved. This project will begin with ab initio path integral simulations of time independent quantum properties such as addressing the extent of quantum delocalisation of adsorbed hydrogen atoms and hydrogen atoms incorporated in molecules adsorbed on solid surfaces. Following this ab initio centroid molecular dynamics techniques specifically designed for the determination of quantum transition state theory rate constants and mechanisms of elementary reaction and diffusion processes at solid surfaces will be developed. This highly ambitious project will culminate in the fully quantum treatment of several elementary reactions at metal surfaces and in so doing open up a new research frontier: the fully quantum path integral treatment of surface chemistry.