XRD and XPS Study of Cu−Ni Interactions on Reduced Copper−Nickel−Aluminum Oxide Solid Solution Catalysts

Abstract

Copper−nickel−aluminum oxide solid solutions were reduced in hydrogen to produce alumina-supported copper−nickel alloy catalysts. XRD patterns of reduced oxides showed that the type of active metals which emerged upon reduction were sensitive to the reduction temperature and the copper content. Variations from +0.8 to +1 eV were found in the experimental Ni 2p3/2 binding energy (BE) of nickel in the solid solutions compared to the experimental Ni 2p3/2 BE of bulk nickel, attributed to the Ni−Ni arrangements in the solid solution. Also, when the curve-fitted BE values of Ni 2p3/2 and Cu 2p3/2 of different reduced solid solutions were compared, it was found that copper and nickel were in different chemical states depending on reduction temperature and the amount of the copper. Changes in Ni 2p3/2 BE in the reduced solid solutions were also discussed in terms of the filling of nickel d-hole bands due to nickel−copper d−d band interactions. At both high copper content and reduction temperature, copper had a tendency to segregate in order to reduce the interfacial surface energies. This was postulated based on the observation that the Ni 2p3/2 curve-fitted BE values were restored to somewhat close to bulk nickel at a copper content of 11 mol % and reduction temperature of 700 °C.

Carbon nanotubes supported Cu–Ni bimetallic catalysts and their properties for the direct synthesis of dimethyl carbonate from methanol and carbon dioxide

“…9b and c, the binding energy (BE) of Cu (sp 2/3 ) was centered at 932.9 eV (Cu 0 species) and Ni (sp 2/3 ) at 852.7 eV (Ni 0 species), suggesting that Cu and Ni metals were produced under the reduction and activation step, these results were in accordance with XRD observations. Such BE values were slightly different from those reported in literature [35]. These differences indicated that some changes in electron density and chemical environmental of Cu and Ni took place in catalyst preparation.…”

Enhanced chemoselective hydrogenation of dimethyl oxalate to methyl glycolate over bimetallic Ag–Ni/SBA-15 catalysts

“…Notably, the temperature at the maximum reduction peak was 644 K, which was lower than that for the reduction of unsupported pristine NiO (703 K) [33]. This phenomenon illustrated the interaction between nickel species and silica support [12].…”

Influence of copper on nickel-based catalysts in the conversion of glycerol

“…The peaks at around 2e = 37. [33,35,38,[43][44][45]. Diffraction peaks of Ni species are not observed in all the XRD patterns.…”

“…In addition, the difference in the position of reduction peaks reported here can be related to the fact that reduction peaks strongly depend on the particle dimension and the interaction strength between metal particles and the support. Previous work dealing with TPR studies on the reduction of Ni-Cu/y-Al 2 O 3 catalysts suggested that the addition of Cu to Ni precursors can dramatically decrease the reducing temperature of Ni oxides, and might markedly enhance the reducibility of the mixed oxide catalysts [23,38,39]. The promotion effect was stronger as the amount of Cu introduced increased [40][41][42].…”