The interaction of materials with hydrogen-containing atmospheres inevitably involves surface processes such as dissociative adsorption of hydrogen molecules, direct chemisorption of atomic hydrogen or even direct penetration of energetic hydrogen species, for example from a plasma, into the material. In addition to the types of hydrogen species and the physical properties of the atmosphere such as temperature, pressure, etc., the specific surface chemistry is of course also decisive in determining whether hydrogen interacts strongly with a particular material.

This has important implications for a broad range of applications where hydrogen can have both beneficial and detrimental effects on materials. Here, we present recent modelling activities mainly based on density functional theory (DFT) and microkinetic modelling addressing the interaction of hydrogen with surfaces in the contexts of i) tailored materials modification by hydrogen treatment and ii) tribology.

The hydrogenation of metal oxides is currently a very active field of research that promises tailored materials modifications in terms of electronic structure, catalytic properties and proton conductivity, to name just a few examples. Corresponding applications include photoelectrochemical water splitting, solid-state fuel cell electrolytes or nanoelectronics. We will show how the efficiency of hydrogenation processes for the prototypical TiO$_2$ has increased tremendously over the last decade and how some major advancements have been supported and underpinned by our modeling activities of hydrogen-surface interactions. [1,2]

The significance of hydrogen atmospheres is also gaining importance in tribological contexts, as hydrogen is being considered as a future fuel for combustion engines in certain applications and many tribological aspects arise in the context of the infrastructure for a hydrogen economy. Here too, the modeling of surface and interface processes can play an important role in understanding the influence of hydrogen atmospheres on friction and wear of various relevant material systems, as we will show.

[1] X. Wang, L. Mayrhofer, M. Hoefer et al., Facile and Efficient Atomic Hydrogenation Enabled Black TiO2 with Enhanced Photo-Electrochemical Activity via a Favorably Low-Energy-Barrier Pathway. Adv. Energy Mater. 9, 1900725 (2019).

[2] X. Wang, L. Mayrhofer, M. Keunecke et al., Low-Energy Hydrogen Ions Enable Efficient Room-Temperature and Rapid Plasma Hydrogenation of TiO2 Nanorods for Enhanced Photoelectrochemical Activity. Small 18, 2204136 (2022).