Water-soluble poly(4-styrenesulfonic acid-co-maleic acid) stabilized ruthenium(0) and palladium(0) nanoclusters as highly active catalysts in hydrogen generation from the hydrolysis of ammonia–borane

Abstract

Abstract Water-soluble poly(4-styrenesulfonic acid-co-maleic acid), PSSA-co-MA, stabilized ruthenium(0) and palladium(0) nanoclusters were for the first time prepared in situ from the reduction of ruthenium(III) chloride and potassium tetrachloropalladate(II), respectively, by ammonia–borane during its hydrolysis at room temperature. PSSA-co-MA stabilized ruthenium(0) and palladium(0) nanoclusters having average particle size of 1.9 ± 0.5 and 3.5 ± 1.6 nm, respectively, were isolated from the reaction solution and characterized by TEM and UV–visible electronic absorption spectroscopy. PSSA-co-MA stabilized ruthenium(0) and palladium(0) nanoclusters are highly active catalysts for hydrogen generation from the hydrolysis of ammonia–borane at low temperature. PSSA-co-MA stabilized ruthenium(0) and palladium(0) nanoclusters provide 51,720 and 8720 turnovers, respectively, in the hydrogen generation from the hydrolysis of ammonia–borane at 25 °C before deactivation. Catalytic hydrolysis of ammonia–borane is first order with respect to the catalyst concentration, but zero order with respect to the substrate concentration in the case of both ruthenium(0) and palladium(0) nanoclusters. Activation energies for the hydrolysis of ammonia–borane in the presence of PSSA-co-MA stabilized ruthenium(0) or palladium(0) nanoclusters (54 ± 2 kJ mol−1 and 44 ± 2 kJ mol−1, respectively) are smaller than most of the values reported for the same reaction in the presence of other catalyst systems.