Nanostructured Ni-YSZ Anode By Atomic Layer Deposition for Solid Oxide Fuel Cells

Nickel yttria-stabilized zirconia (Ni-YSZ) is the most commonly used anode for solid oxide fuel cells (SOFCs). The electrochemical performance of Ni-YSZ anodes can be improved when the size of constituent particles is reduced. However, under SOFC operating environment, nano-sized Ni particles suffer from sintering; nanoscale Ni-YSZ anodes can undergo structure changes, which constrain the development of nanoscale Ni-YSZ anodes.

In this work, nanoscale nanostructured Ni-YSZ anode was successfully fabricated by combining atomic layer deposition (ALD) and glancing angle deposition (GLAD). Prior to atomic layer deposition of YSZ, the porous Ni nanorod electrode was firstly prepared by GLAD. ALD was applied to deposit a uniform nanoscale YSZ coating layer over the nickel nanorods. The morphology of the nanostructured Ni-YSZ anode was examined with scanning electron microscopy (SEM). The surface area was increased to more than 3 times as large as plane area and the triple phase boundary (TPB) extended to the entire nickel surface. The surface composition was examined with X-ray photoelectron spectroscopy (XPS). The atomic composition of YSZ film was controlled by the ALD process and not affected by the post-deposition annealing process. ALD coating approach combined ionic conductive YSZ electrolyte phase with electrical conductive Ni phase flexibly and controlled the porosity of the nano-composite electrode just through deposition and post-deposition annealing process. Electrical conductivity measurements were performed using a 4-point probe method. The Ni-YSZ anodes maintained resistivity in the 10^-4 cm·S^-1 magnitude, which is sufficiently conductive as an SOFC anode. The ALD YSZ coating layer showed sintering-resistance on the nanostructured electrode with an as thin as 1.9 nm YSZ coating layer and excellent anode performance under SOFC operating conditions.