Controlled synthesis of a hexagonal-shaped NiO nanocatalyst with highly reactive facets {1-1-0} and its catalytic activity

A new facile chemical approach has been developed to produce hexagonal-shaped NiO nanocrystals with high-energy facets {1-1-0} under hydrothermal synthesis followed by annealing in the presence of air. The phase purity, crystallinity, shape/size, and mesostructure of NiO nanocrystals were investigated by powder XRD and high-resolution transmission electron microscopy. The size, shape, and exposed crystal facets of the nanocrystals are the key factor for their physical and chemical properties. Herein, the chemical properties of hexagonal-shaped NiO nanocrystals have been tested for the reduction of carbonyl compounds in comparison with NiO nanoparticles and bulk NiO materials. The reactivity of the NiO nanocrystals is enhanced dramatically through morphology evolution. In particular, hexagonal-shaped NiO nanocrystals with highly reactive {1-1-0} facets exhibit approximately 12 and 25-% higher catalytic activity than NiO nanoparticles and bulk NiO, respectively. These hexagonal-shaped NiO nanocrystals are active over several cycles for the reduction of carbonyl compounds to their respective alcohol in the presence of 2-propanol. Effect of the crystal shape: Hexagonal-shaped NiO nanocrystals with highly reactive {1-1-0} facets show approximately 12 and 25-% higher catalytic activity than NiO nanoparticles and bulk NiO, respectively, in the catalytic reduction of benzaldehyde with 2-propanol as a solvent and hydride-donating agent.