Preparation of superporous poly(4-vinyl pyridine) cryogel and their templated metal nanoparticle composites for H2 production via hydrolysis reactions

The superporous cryogels of poly(4-vinylpyridine) p(4-VP) were prepared via free radical polymerization technique under cryogenic conditions (T = − 18 °C). The prepared p(4-VP) cryogel was used as template for in situ metal nanoparticle preparation using Co, Ni and Cu by loading these ions into the p(4-VP) network from their corresponding metal (II) ion aqueous solutions, and then treating with a reducing agent, sodium borohydride (NaBH4). The prepared cryogel p(4-VP)-M (M: Co, Ni, Cu) composite catalysts were successfully used in hydrogen (H2) generation from the hydrolysis of NaBH4 and ammonia borane (AB). The physicochemical structure and the thermal behavior of the prepared superporous p(4-VP) cryogels were analyzed via optical microscopy, FT-IR spectroscopy and thermogravimetric analyzer (TGA). The amounts of metal nanoparticles within superporous p(4-VP)-M cryogel composites were determined by atomic absorption spectroscopy (AAS) and TGA measurements. Multiple metal ion loading-reduction cycles were completed for superporous p(4-VP) cryogels to increase the amount of Co content. The activation energies for NaBH4 and AB hydrolysis catalyzed by superporous p(4-VP)-Co cryogel composites were calculated as 28.75 and 34.98 kJ/mol, respectively.