Monodispersed p(2-VP) and p(2-VP-co-4-VP) particle preparation and their use as template for metal nanoparticle and as catalyst for H2 production from NaBH4 and NH3BH3 hydrolysis

The monodispersed poly(2-vinyl pyridine) (p(2-VP)) and poly(2-vinyl pyridine-co-4-vinyl pyridine) (p(2-VP-co-4-VP)) particles of different compositions were synthesized by a surfactant-free emulsion polymerization system using divinyl benzene (DVB) as cross-linker. The diameter of p(2-VP) and p(2-VP-co-4-VP) particles were measured between 370 and 530 nm. Co, Ni and Cu metal nanoparticles were prepared inside these microgels after quaternization with HCl and loading of metal salts, such as CoCl₂, NiCl₂, and CuCl₂, in ethyl alcohol followed by reduction with NaBH₄. The prepared metal nanoparticles within these particles were used as catalyst for H₂ production via hydrolysis of NaBH₄ and NH₃BH₃. Various parameters of the polymeric microgels such as template, metal types, reuse, the amount of NaOH, and temperature were investigated. From hydrolysis reactions the activation energy (E_a), enthalpy (ΔH), and entropy (ΔS) were calculated for Co metal nanoparticles as catalyst for the NaBH₄ hydrolysis reaction in the temperature range of 0–50 °C. The activation parameters of NaBH₄ hydrolysis catalyzed by Co nanoparticle composite systems were calculated as 46.44 ± 1.1 kJ mol⁻¹ for E_a, 36.39 ± 6.5 kJ mol⁻¹ for ΔH and −170.56 ± 20.1 kJ mol⁻¹ K⁻¹ for ΔS.