PtNi/NiO Clusters Coated by Hollow Sillica: Novel Design for Highly Efficient Hydrogen Production from Ammonia-Borane.

Ammonia-borane (NH3·BH3; AB) has been considered as an excellent chemical material for hydrogen storage. However, developing highly efficient catalysts for continuous hydrogen generation from AB is still a challenge for future fuel cell applications. The combination of Pt with Ni is an effective strategy to achieve active bimetallic nanocatalyst, and the particle size has proved to play a crucial role in determining its final activity. However, the synthesis of PtNi bimetallic catalyst in the size of highly dispersed clusters has always been a challenge. In this report, PtNi/NiO clusters coated by small-sized hollow silica (R-PtNi/NiO@SiO2) were designed for efficient hydrogen generation from the hydrolysis of ammonia-borane. The newly designed catalysis system showed extremely high activity with the initial turnover frequency value reaching 1240.3 mol of H2·mol-1 of Pt·min-1, which makes it one the most active Pt-based catalysts for this reaction. Detailed characterization by means of scanning transmission electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy element mapping, etc. revealed that the excellent performance of R-PtNi/NiO@SiO2 is derived from the highly dispersed PtNi/NiO clusters and the reduction of extra Pt4+ on the surface of PtNi/NiO clusters to Pt0 at relatively low temperature.