Poly(4-styrenesulfonic acid-co-maleic acid) stabilized nickel(0) nanoparticles: Highly active and cost effective catalyst in hydrogen generation from the hydrolysis of hydrazine borane

摘要

When hydrazine borane is added to the solution of nickel(Ⅱ) chloride and poly(4-styrenesulfonic acid-co-maleic acid), PSSMA, both reduction of nickel(Ⅱ) ions to nickel(0) nanoparticles and hydrogen release from the hydrolysis of hydrazine borane occur concomitantly at room temperature. Using the hydrogen evolution from the hydrolysis of hydrazine borane as reporter reaction provides valuable insights to the formation kinetics of nickel(0) nanoparticles. Nickel(0) nanoparticles are in situ formed from the reduction of precursor nickel(Ⅱ) chloride by hydrazine borane and stabilized by PSSMA present in the solution. The in-situ generated, PSSMA-stabilized nickel(0) nanoparticles (PSSMA-Ni) with an average particle size of 8.3 ± 2.3 nm were isolated from reaction medium by centrifu-gation and characterized by UV-Vis., TEM, EDX, XRD, and XPS techniques. PSSMA-stabilized nickel(0) nanoparticles were found to be highly active and stable catalyst in hydrogen generation from the hydrolytic dehydrogenation of hydrazine borane releasing 2.6-3.0 mol H_2 per mol of hydrazine borane. They provide 1600 turnovers in hydrogen generation from the hydrolysis of hydrazine borane over 18 h before deactivation with an initial TOF value of 3.05 min~(-1) at 25 ± 0.5 ℃. Carbon disulnde poisoning experiments show that the hydrolytic dehydrogenation of hydrazine borane catalyzed by PSSMA-stabilized nickel(0) nanoparticles is a heterogeneous catalysis. This report also includes the detailed kinetic study of the hydrolytic dehydrogenation of hydrazine borane catalyzed by PSSMA-stabilized nickel(0) nanoparticles depending on the catalyst concentration, substrate concentration and temperature. The apparent activation energy of the catalytic reaction was calculated from the evaluation of temperature dependent kinetic data: E_a~(appa) ＝ 73± 2 kJ/mol.