Acid properties of WOx/t-ZrO2 under hydrothermal environments: A periodic DFT study

The acid properties of WOx/t-ZrO2 under hydrothermal environments were theoretically investigated with density functional theory calculations. The calculations indicate that water molecules can be readily chemisorbed on t-Zr (1 1 0), followed by spontaneous dissociation to form a fully hydrated surface. The structural parameters of the WOx species anchored on t-Zr (1 1 0) are determined mainly by the coordination of central W atoms, and surface hydration has no essential effect on the configuration of WOx species. The thermodynamic equilibrium among WOx species is found to be closely relevant to the applied hydrothermal environments. The transformation of WOx species to the condensated configurations with higher Lewis acidity tends to occur at high temperature and low partial pressure of water, while the configurations with multiple Brّnsted sites are preferentially formed at moderate temperature and high partial pressure of water.