Macroporous cryogel metal nanoparticle composites for H2 generation from NaBH4 hydrolysis in seawater

Abstract

Poly(2-hydroxy ethyl methacrylate) p(HEMA), poly(acrylic acid) p(AAc), poly(3-sulfopropyl methacrylate) p(SPM), and poly(4-vinylpyridine) p(4-VP) cryogels from various monomers containing functional groups such as COOH, SO3H, and OH, and N monomer were synthesized under cryogenic conditions via free radical polymerization technique. The synthesized cryogels were used as templates for metal nanoparticle synthesis using Co and Ni, and the prepared composite cryogels were utilized in hydrogen (H2) generation from the hydrolysis reaction of NaBH4. It was found that the hydrolysis reaction of NaBH4 in seawater is much faster than in DI water when using the p(SPM)-Co catalyst system. Parameters such as water and metal types for different cryogels, concentration of NaBH4, amount of metal catalyst, and temperature were investigated. The hydrogen generation rate (HGR) and turnover frequency (TOF) values were also investigated for temperature dependency. It was found that as the temperature increased from 30 to 70°C, the HGR and TOF increased from 1288.0±61.2 (ml H2) (g of metal min)−1 and 3.1±0.1mol H2 (mol metal min)−1 to 7707.8±179.4 (ml H2) (g of metal min)−1, and 16.1±0.4mol H2 (mol metal min)−1, respectively. The activation energy, enthalpy, and entropy were 31.1kJ (molK)−1, 27.7kJ (molK)−1, and −196.4J (molK)−1, respectively, for NaBH4 hydrolysis catalyzed in seawater by p(SPM)-Co composite system.