Core-shell Fe-cross-linked biopolymer as nanohybrid catalyst and Ni particle: kinetics and thermodynamics of hydrogen generation via NaBH4 hydrolysis

In this work, Fe and Ni supported on extracted Glucomannan (Glu) from Orchis Mascula roots were prepared. N,N''-Methylenebisacrylamide as a cross-linker and methacrylic acid as a monomer were used to convert soluble extract to insoluble glucomannan. Synthesized catalysts were characterized by XRD, XPS, FE-SEM, EDS, and TEM techniques. Significant TEM shows polymer chains formed as a circular structure including metal/metal boride species. Indeed, iron particles are entrapped in the cavities of glucomannan polymer as a core-shell structure. Average size of the entrapped Fe is 11 nm while Ni particle is 256 nm. The efficacy of the synthesized catalysts is evaluated for hydrogen production. Kinetic investigations were conducted to ascertain the partial order concerning catalyst dosage and NaBH4 concentration. Results cleared that totally order of hydrolysis reaction is approximately near to 1 and 1.5 for Fe/Glu and Ni/Glu, respectively. The activation energy values of Fe/Glu and Ni/Glu catalysts were estimated at 28 and 63 kJ/mol, respectively. ∆H# and ∆S# values of Fe/Glu and Ni/Glu catalysts were calculated at 35.75 kJ/mol and -170.6 J/molK and 74.41 kJ/mol and -63.8 J/molK, respectively.