Effect of alkali leaching on the surface structure of Ni3Al catalyst

The surface structure of the alkali-leached single-phase Ni3Al powder was investigated by X-ray diffraction, BET (Brunauer–Emmett–Teller) surface area analysis, electron microscopy, X-ray photoelectron spectroscopy, and temperature-programmed reduction. It was found that fine Ni particles of several nm in diameter were formed on the outer surface layer of the Ni3Al powder after the alkali leaching process. The surface of the Ni particles was covered with a thin layer of Ni oxides and hydroxide, Ni2O3, NiO and Ni(OH)2, and these Ni oxides and hydroxide can be easily reduced by hydrogen to the metallic nickel that is catalytically active. The inside of the Ni3Al powder remained as the original Ni3Al ordered structure after alkali leaching. Having heat resistant properties, the Ni3Al phase can serve as a support of the fine Ni particles and provide the structural and thermal stabilities to the fine Ni particles.