Spectrophotometric analysis of nickel colloid performances as catalysts for hydrogenation of nitro-phenol: Influence of the stabilizing agents

• Ni nanoparticles are prepared through thermolysis and polyol procedures.
• Ni colloids have similar dimensions and structure but different capping agents.
• The reduction of 4-NPh catalysed by Ni NPs is spectrophotometrically monitored.
• Alkyl amine-stabilized NPs show the higher reaction rate and TON value.
• Azocompounds are also formed when the catalyst is stabilized by alkyl amines.

Nickel nanoparticles are prepared through thermolysis or polyol procedures and they are fully characterized through TEM and XRD. The catalytic efficiencies are tested toward the hydrogenation reaction of 4-nitrophenol, which was spectrophotometrically detected. A significant improvement of the reaction rate and turnover number (TON) and frequency (TOF) is observed using alkyl amine-stabilized nanoparticles, likely due to their reduced surface steric hindrance. However, the polymer stabilized-nanocatalysts show a better selectivity for product formation, since only hydrogenation products are observed, while azo-benzene derivatives are detected when alkyl amine-stabilized nanoparticles are used. The findings indicate an important impact of surface properties of colloids on the catalysed reaction.

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