  Amidst the growing importance of hydrogen in a sustainable future, it is
crucial to develop coatings that can protect hydrogen-sensitive system
components in reactive hydrogen environments. However, the prediction of the
chemical stability of materials in hydrogen is not fully understood. In this
study, we show that the work function is a key parameter determining the
reducibility (i.e., de-nitridation) of transition metal nitrides (TMNs) in
hydrogen radicals (H*) at elevated temperatures. We demonstrate that when the
work function of a TMN system drops below a threshold limit, its reduction
effectively stops. We propose that this is due to the preferential binding of
H* to TM-atoms rather than N-atoms, which makes the formation of volatile
species (NHx) unfavourable. This finding provides a novel perspective for
comprehending the interaction of hydrogen with transition metal compounds and
allows predicting the chemical stability of hydrogen-protective coatings.
