First principles study on electronic structures of Ni/H/ZrO₂ triple phase boundary

We have investigated the electronic structures of Ni/H/ZrO₂ triple phase boundary (TPB) from first principles. For this purpose, we constructed a novel computational model for the TPB having a point contact of a Ni-tip and ZrO₂(111) surface. We examined several locations of the tip with respect to the ZrO₂(111) surface, and found that the fee location of the Ni-tip is the most stable point contact TPB. The projected density of states (PDOS) of the apex Ni atom of the point contact TPB shows a large and sharp peak at 0.5 eV above the Fermi level. Such a large peak, on the other hand, is not seen in Ni(111) surface without Ni protrusions. We also revealed that the adsorption of hydrogen atom at the Ni-tip leads to a wider peak of PDOS of the apex Ni atom. The change in the shape of the PDOS suggests that the adsorption of hydrogen atom at the Ni-tip will alter the reactivity of the TPB of Ni-tip/ZrO₂(111).