Adsorption of water on TiN (1 0 0), (1 1 0) and (1 1 1) surfaces: A first-principles study

[Display omitted] ► We study dependence of adsorption of H 2O at TiN on its surface orientation. ► H 2O adsorbs molecularly on TiN (1 0 0) and (1 1 1) surfaces with energies −0.94 and −0.78 eV respectively. ► H 2O adsorbs dissociatively on TiN (1 1 0) surface with stronger binding (−2.44 eV). ► General trends seen above explain H 2O adsorption on other surfaces (e.g. ZrN/MgO). We use first-principles density functional theory-based calculations in the analysis of the interaction of H 2O with (1 0 0), (1 1 0) and (1 1 1) surfaces of TiN, and develop understanding in terms of surface energies, polarity of the surface and chemistry of the cation, through comparison with H 2O adsorption on ZrN. While water molecule physisorbs preferentially at Ti site of (1 0 0) and (1 1 1) surfaces, it adsorbs dissociatively on (1 1 0) surface of TiN with binding stronger than almost 1.32 eV/molecule. Our analysis reveals the following general trends: (a) surfaces with higher energies typically lead to stronger adsorption, (b) dissociative adsorption of H 2O necessarily occurs on a charge neutral high energy surface and (c) lower symmetry of the (1 1 0) plane results in many configurations of comparable stability, as opposed to the higher symmetry (1 0 0) and (1 1 1) surfaces, which also consistently explain the results of H 2O adsorption on MgO available in literature. Finally, weaker adsorption of H 2O on TiN than on ZrN can be rationalized in terms of greater chemical stability of Ti arising from its ability to be in mixed valence.