Pulsed laser deposition of cluster-assembled films for catalysis and the photocatalysis relevant to energy and the environment

Nanoparticles (NPs) catalysts are under intense investigation in the catalysis community due to their exceptional activity and selective nature in catalytic processes as compared to the corresponding bulk counterpart, especially because of their large surface-to-volume atomic ratio, size-and shape-dependent properties, and high concentration of low-coordinated active surface sites. However, there is no general strategy to synthesize NPs of various materials with narrow size distribution, tailored properties, and desired morphologies. The development of a technique able to prepare NPs is thus a goal of great importance to avoid present trial and error approaches. Here we report on selected examples where pulsed laser deposition (PLD) technique greatly contributes toward NPs synthesis. Co NPs embedded in B matrix films have been synthesized by PLD technique by taking advantage of the phase explosion process of superheated liquid where a mixture of vapor and liquid droplets leave the irradiated target surface and get deposited on the substrate. The deposited NPs exhibit catalytic properties comparable to that of precious metals in hydrogen production by hydrolysis of NaBH4 and NH3BH3. These NPs, when supported on rough carbon film prepared by PLD, show about 30% increase in catalytic activity for H-2 production as compared to unsupported NPs. Co3O4 NPs assembled coating has been produced by reactive PLD in oxygen atmosphere at various substrate temperatures from room temperature to 250 degrees C. It was proved that the Co3O4 NPs can be obtained in a single step at low temperatures with mixed disordered-nanocrystalline phase that is a relevant feature for catalysis. The Co3O4 NPs assembled thin coating, employed in degradation of methylene blue solution, in water, via photo Fenton reaction in presence of H2O2, exhibits significantly higher activity as compared to the corresponding homogeneous catalyst. (C) 2012 Elsevier B. V. All rights reserved.