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

Double-confined nickel nanocatalyst Ni/Ni-(Al)O-x/AlOx, with metal Ni nanoparticles implanted in the weakly crystalline Ni(Al)O-x 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 Ni-0 clusters nucleate initially in the Ni(Al)O-x matrix. Subsequent growth of Ni-0 clusters proceeds at the expense of the surrounding Ni(Al)O-x, accompanied by consecutive transfer of Al3+ from the central part to the near-surface, suggesting a mechanism of ion reverse migration. The Ni(Al)O-x 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.