Influence of mixing time during glycine-nitrate process on the structural properties and reducibility of a dual-phase Ni-Cu-Mn spinel catalyst

The potential of Ni-Cu-Mn spinels as methane reforming catalysts for hydrocarbon-fueled solid oxide fuel cell (SOFC) applications is highly dependent on its catalytic properties, particularly reducibility. The reducibility of a spinel-structured catalyst is often correlated with its structural properties and fabrication processes. In this work, the structural properties and reducibility of a Ni-Cu-Mn spinel catalyst was evaluated on the basis of mixing time during the glycine-nitrate process. Phase analysis results showed that Ni0.4Cu0.6Mn2.0O4 and (Cu, Mn)(3)O-4 in normal or inversed spinel structures were observed in GNP-produced Ni-Cu-Mn spinel catalyst powders. Distortion in inverse spinel structures enhanced the reducibility of the spinel catalyst. Morphological analysis results showed that complete nitrate binding occurred at a minimum mixing time of 24 h and resulted in homogenous particle size distribution and uniform elemental distribution. Furthermore, the Ni-Cu-Mn spinel catalyst produced after 24 h of mixing was fully reduced at 450 degrees C. The reducing pattern of the Ni-Cu-Mn spinel catalyst produced after 24 h of mixing time showed strong metal-support interaction and the fast adsorption of reactants. These effects were due to either the distribution of divalent cations in octahedral sites or large amounts of bulk pores. In conclusion, a minimum mixing time of 24 h is sufficient to produce the desired structural properties and reducibility of Ni-Cu-Mn spinel catalysts for SOFC applications.