Effect of Al₂O₃ inter-layer grown on FeCrAl alloy foam to improve the dispersion and stability of NiO catalysts

NiO catalysts/Al₂O₃/FeCrAl alloy foam for hydrogen production was prepared using atomic layer deposition (ALD) and subsequent dip-coating methods. FeCrAl alloy foam and Al₂O₃ inter-layer were used as catalyst supports. To improve the dispersion and stability of NiO catalysts, an Al₂O₃ inter-layer was introduced and their thickness was systematically controlled to 0, 20, 50 and 80 nm using an ALD technique. The structural, chemical bonding and morphological properties (including dispersion) of the NiO catalysts/Al₂O₃/FeCrAl alloy foam were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy and scanning electron microscopy-energy dispersive spectroscopy. In particular, to evaluate the stability of the NiO catalysts grown on Al₂O₃/FeCrAl alloy foam, chronoamperometry tests were performed and then the ingredient amounts of electrolytes were analyzed via inductively coupled plasma spectrometer. We found that the introduction of Al₂O₃ inter-layer improved the dispersion and stability of the NiO catalysts on the supports. Thus, when an Al₂O₃ inter-layer with a 80 nm thickness was grown between the FeCrAl alloy foam and the NiO catalysts, it indicated improved dispersion and stability of the NiO catalysts compared to the other samples. The performance improvement can be explained by optimum thickness of Al₂O₃ inter-layer resulting from the role of a passivation layer.