Micro poly(3-sulfopropyl methacrylate) hydrogel synthesis for in situ metal nanoparticle preparation and hydrogen generation from hydrolysis of NaBH₄

Polymeric hydrogels derived from SPM (3-sulfopropyl methacrylate) of micrometer size were used in the preparation of a composite-catalyst system for hydrogen generation from hydrolysis of NaBH₄. In situ Co and Ni nanoparticles were prepared by chemical reduction of absorbed Co (II) and Ni (II) ions inside the hydrogel networks, and the whole composite was used as a catalyst system. The catalytic activity of the metal nanoparticles within the p(SPM) hydrogel matrix was better and faster using Co than with Ni. Additionally, other parameters that affect the hydrogen generation rate, such as temperature, metal reloading, the catalyst amounts as well as reusability, were also investigated. It was found that p(SPM)-Co micro hydrogels were even effective for hydrogen generation at 0 °C with a hydrogen generation rate of 966 (mL H₂) (min)^-1 (g of Co)^-1. The activation energy, activation enthalpy, and activation entropy for the hydrolysis reaction of NaBH₄ with micro p(SPM)-Co catalyst system were calculated as 44.3 kJ/mol, 43.26 kJ/mol K, and -150.93 J/mol K, respectively.