Courtney Pellett

Brigham Young University

Project Title: Use of Raney Nickel in Anode Development of Solid Oxide Fuel Cells
Advisors: Prof. Trumble and Prof. Slamovich

Introduction:

Fuel cells in general produce electricity by a chemical reaction that results from a concentration gradient or different oxidation states of chemicals. Solid Oxide Fuel Cells in particular work under a concentration gradient of Oxygen ions that move across an electrolyte to combine with Hydrogen ions. This process allows the SOFC to produce energy and useful waste products, such as water, which makes this method of energy production highly favorable. Solid Oxide Fuel Cells have the potential to be very useful and economical investments because of their extremely high output of energy. Furthermore, they are more reliable and proficient than other fuel cells because of their solid state and convenient size. Unfortunately, these fuel cells cannot measure up to their full aptitude until a process to separate the hydrogen, or other gas that runs through the anode into ions and electrons at an unrestricted rate is discovered.

Project Objectives:

  • Employ Raney nickel, a catalyst with an extremely high surface area, in the anode of a Solid Oxide Fuel cell by infiltrating it into a Zirconia preform.
  • Characterize resulting infiltrated YSZ disk to determine if infiltration occurred on a macro and/or micro scale and methods to improve infiltration product.

Experimental Approach:

  • Cast an alloy by melting 52 weight % Aluminum with 48 weight % Nickel to for a two-phase metal with a 1:1 ratio of Al3Ni and Al3Ni2 Aluminides
  • Sintered a 7% Yttrium Stabilized Zirconia disk by heating YSZ powder at 1400∞C for 4 hours in furnace
  • Heated experimental Set up to 1350∞C, then applied 1 atmosphere of pressure of 5% Hydrogen/ Argon gas for 5 minutes at temperature and cooled under pressure
  • Cut experiment crucible with diamond saw, polished and characterized results before leaching with caustic
  • Leached metal and infiltrated perform with 10% NaOH solution at 50∞C by submersion and characterized sample at intervals

Research Findings:

  • In formation of alloy, an even distribution of porosity occurred even before leaching due to shrinkage
  • In characterization of the cast alloy, Al3Ni formed first as a lighter phase followed by Al3Ni2, and a small amount of eutectic Al3Ni/AlNi solid solution was dispersed sporadically
  • The alloy did infiltrate the YSZ perform on a macroscopic scale and infiltrated portion of the disk remained in tact while the remaining portion did not
  • Infiltration occurred both in between the sintered granules of YSZ as well as in some of the granules themselves, which was not expected after sintering at such a high temperature
  • Impurities found in the cast alloy were multiplied after the alloy was infiltrated into the YSZ preform
  • Leaching the alloy in alkaline solution favorably created higher porosity and a greater surface area of Raney Nickel at interfaces with YSZ as was anticipated

Figure 1: Infiltrated YSZ disk
(magnification of 2000X)
Figure 2: Raney Nickel alloy
(magnification 500X)