  Understanding surface reactivity is crucial in many fields, going from
heterogeneous catalysis to materials oxidation and corrosion. In order to
decipher the surface reactions of ZrB2 exposed to the harsh environment of
aerospace components, the chemical activity of both Zr- and B-surfaces is
predicted and compared by using density functional theory and nudged elastic
band methods. In particular the adsorption, dissociation and diffusion of O2,
CO and H2O are extensively examined through the calculation of surface
adsorption energies and reaction pathways. We find the dissociative adsorption
of O2 dominating the reactivity of ZrB2 surfaces, while the dissociation of H2O
and CO is weakly active on Zr-surfaces, and even less activated on B-terminated
ones. Importantly, we discover that the reaction of O2 and H2O can trigger
strong surface reconstruction at B-surfaces. Our work thus provides significant
insights into the diverse adsorption and reaction mechanisms of ZrB2 surfaces.
