Double-Confined Nickel Nanocatalyst Derived from Layered Double Hydroxide Precursor: Atomic Scale Insight into Microstructure Evolution

Double-confined nickel nanocatalyst Ni/Ni(Al)Ox/AlOx, with metal Ni nanoparticles implanted in the weakly crystalline Ni(Al)Ox matrix and embedded in amorphous AlOx networks, was facilely fabricated by hydrogen reduction of the NiAl-LDH precursor at a controlled temperature. Direct structure imaging of Ni and Al species revealed that subnanometer Ni0 clusters nucleate initially in the Ni(Al)Ox matrix. Subsequent growth of Ni0 clusters proceeds at the expense of the surrounding Ni(Al)Ox, accompanied by consecutive transfer of Al3+ from the central part to the near-surface, suggesting a mechanism of ion reverse migration. The Ni(Al)Ox interfacial shell is proposed to provide a strong connection with the metallic Ni and the AlOx network, improving the hydrogen adsorption capacity of the double-confined Ni catalyst and consequently the catalytic activity for dimethyl terephthalate hydrogenation to dimethyl cyclohexane-1,4-dicarboxylate, a prominent modification reagent and intermediate in the polymer industry. The findings should be of great importance to both designing novel confined catalysts and understanding the structure–activity correlation.