Density functional theory analysis of the stability of H2O and CO2-derived surface species over low-index Ni facets

Analysis of stability of chemical species over catalytic surfaces is crucial for understanding the surface-specific effects to reach optimal catalyst composition. With reference to CO2 hydration, we undertook the task of unravelling the same over Ni surfaces, and examined the effect of exposed surface facets on the stability of relevant surface species. By examining H2O and CO2-derived surface species over Ni(100), Ni(110), and Ni(111) surface facets, we investigated the adsorption and dissociation of H2O and CO2-derived surface, enabling a thorough comparison of facet effects. A linear scaling relationship between the adsorption energy of the adsorbates and Bader charges was observed, providing an evidence that the binding energy of surface species originating from H2O and CO2 was closely correlated to the degree of electron transfer from Ni to the adsorbed species. Understanding of the binding and stability of H2O and CO2-derived species over Ni surfaces was furthered by the analysis of the charge density iso-surfaces. Stability plots and reaction paths highlighted Ni(100) and Ni(110) to be superior to Ni(111). Ni(110) exhibited the lowest H2O dissociation barrier, while Ni(100) showed favourable CO2 dissociation barriers citing Ni(110) surface facet as the most suited plane for selective CO2 hydration.