Dendritic and flowerlike Ni–Co alloy microstructures: a comparison study of their catalytic activities

In this Letter, the catalytic activities of dendritic and flowerlike Ni-Co alloy microstructures (AMs) are evaluated by using a model reaction based on the reducing of 4-nitrophenol (4-NP) to 4-amitrophenol by NaBH₄. The activation energy, the entropy of activation and the pre-exponential factor for each type of Ni-Co AMs were determined, based on the average reaction rate constants at three different temperatures. The kinetic data indicate that dendritic Ni_33.0Co_67.0 AMs were catalytically more active than flowerlike Ni_32.7Co_67.3 AMs probably due to their having more surface-to-volume ratio and surface areas under the nearly same sizes, since the Brunauer-Emmett-Teller surface areas were determined as 33.21-m²/g for dendritic Ni_33.0Co_67.0 AMs and 21.06 m²/g for the flowerlike Ni_32.7Co_67.3 AMs, respectively. Excitingly, the NiCo₂ AMs showed good catalytic activities in reduction of 4-NP, which revealed potential application in catalytic reduction of aromatic nitro compounds by NaBH₄.