Synthesis and Characterization of Branched fcc/hcp Ruthenium Nanostructures and Their Catalytic Activity in Ammonia Borane Hydrolysis

Several systems have shown the ability to stabilize uncommon crystal structures during the synthesis of metallic nanoparticles. By tailoring the nanoparticle crystal structure, the physical and chemical properties of the particles can also be controlled. Herein, we synthesized branched nanoparticles of mixed fcc/hcp ruthenium, which were formed using tungsten carbonyl [W(CO)6] as both a reducing agent and a source of carbon monoxide. The branched particles were formed from multiple particulates off a central core. High-resolution transmission electron microscopy (HRTEM) clearly showed that the branched structures consisted of aligned hcp crystal domains, a mixture of fcc and hcp crystal domains with several defects and misalignments, and particles that contained multiple cores and branches. Branched particles were also formed with molybdenum carbonyl [Mo(CO)6], and faceted particles of hcp and fcc were formed with rhenium carbonyl [Re2(CO)10] as a carbon monoxide source. Without metal carbonyls, small par...