Synthesis and modification of p(VI) microgels for in situ metal nanoparticle preparation and their use as catalyst for hydrogen generation from NaBH4 hydrolysis

Poly(vinyl imidazole) (p(VI)) and poly(VI)-silica (p(VI)-Si) composites were synthesized in an oil-in-water micro emulsion system. Additional pores were generated inside p(VI)-Si composites by removing the silica by HF treatment to obtain poly(VI)-porous (p(VI)-por) particles. The size of p(VI)-based particles ranged between 300 and 800 nm. Co and Ni metal nanoparticles were prepared inside p(VI)-based particles by the absorption of the corresponding metal ions from aqueous solution, and reduction with NaBH4 in situ. Different parameters such as temperature, metal nanoparticle types, NaOH concentration, and metal ion reloading for metal nanoparticle formation for hydrogen generation were investigated. The activation energy, the enthalpy, and the entropy for the NaBH4 hydrolysis reaction were calculated to be 37.578 kJ mol(-1), 34.146 kJ mol(-1), and -191.22 kJ mol(-1) K-1, respectively. It was found that the hydrogen production rate increased drastically by five times repetitive metal ion loading-reduction cycles that increased the amount of metal nanoparticle inside p(VI) particles. (c) 2013 Elsevier B.V. All rights reserved.