Design of Anode Materials for IT SOFC: Effect of Complex Oxide Promoters and Pt Group Metals on Activity and Stability in Methane Steam Reforming of Ni/YSZ (ScSZ) Cermets

Abstract

Ni/YSZ or Ni/ScCeSZ cermets were promoted by up to 10 wt % of fluoritelike (Pr–Ce–Zr–О, La–Ce–Zr–О, and Ce–Zr–О) or perovskitelike (La–Pr–Mn–Cr–O) oxides and small (up to 1.4 wt %) amounts of Pt group metals (Pd, Pt, or Ru). Reactivity of samples, their lattice oxygen mobility, and their ability to activate methane were characterized by temperature-programed reduction by CH4. The catalytic properties of these samples in methane steam reforming were studied at 500–850°C and short contact times (10 ms) in feeds with 8 mol % of CH4 and steam/methane ratio of 1:3. Oxide promoters ensure stable performance of cermets in stoichiometric feeds at T>650°C by suppressing carbon deposition. Copromotion with precious metals enhances performance in the intermediate temperature (450–600°C) range due to more efficient activation of methane. Factors determining specificity of these cermet materials’ performance (chemical composition, microstructure, oxygen mobility in oxides, interaction between components, and reaction media effect) are considered. The most promising systems for practical application are Pt/Pr–Ce–Zr–O/Ni/YSZ and Ru/La–Pr–Mn–Cr–O/Ni/YSZ cermets demonstrating a high performance in the intermediate temperature range under broad variation in steam/CH4 ratio.