Periodic DFT and atomistic thermodynamic modeling of reactivity of H ₂, O₂, and H₂O molecules on bare and oxygen modified ZrC (100) surface

A comprehensive study was carried out using DFT calculation, together with statistical thermodynamics study of oxygen, hydrogen, and water sorption on the bare and ZrO-modified ZrC (100) surface. The bare ZrC (100) surface is found to be fully covered by oxygen whatever the temperature and pressure whereas it is free of hydrogen. Water adsorbs on the bare surface at temperatures below 200 K and dissociates into surface hydroxyl groups, but all water induced features are lost at room temperature. Oxygen modification further activates the (100) surface, and water adsorbs strongly as either atomic O with H₂ release or into surface OH and H groups. Thermodynamic stability plots at 300 K for different water coverage predict coverage of 0.75 ML at >10^-8 bar. These findings compare well with experimental photoemission studies published in the literature.