Ultrafine Pd nanoparticles stabilized on magnetic Fe3O4@SiO2-g-C3N4 composites for the hydrolytic dehydrogenation of ammonia borane

Abstract

The magnetic composites consisting of a porous graphitic carbon nitride (g-C3N4) and the core-shell Fe3O4@SiO2 were facilely prepared. Subsequently, the Pd nanoparticles (NPs) were stabilized on the composites by the in-situ reduction of PdCl2 with sodium borohydride. The mass ratio of Fe3O4@SiO2 to g-C3N4 was optimized in view of the catalytic activity of the corresponding Pd-based catalysts for ammonia borane (AB) hydrolysis. The results showed that the catalyst fabricated with a mass ratio of 1:1 (Fe3O4@SiO2: g-C3N4) displayed the highest catalytic activity. The Pd NPs were mainly distributed in the region of 5.4–9.8 nm in the optimal Pd/Fe3O4@SiO2-g-C3N4 catalyst, which had a specific surface area of 47.5 m2 g−1 and a total pore volume of 0.126 cm3 g−1. Catalyzed by the optimal catalyst, the turnover frequency was 33.7molH2·molPd−1·min−1, and the apparent activation energy was 31.4 kJ mol−1. Also, the recycling experiments indicated that the optimal catalyst still maintained a high catalytic activity even after eight runs. The superior catalytic performance is presumably due to the highly dispersed Pd NPs and the stably porous structure with large specific surface area. The excellent catalytic and magnetic properties endow Pd/Fe3O4@SiO2-g-C3N4 exciting potential in the hydrogenation generation from the hydrolysis of solid hydrogen storage materials.