We report the synthesis and characterization of new Ni(x)Ru(1-x) (x = 0.56-0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet-chemistry method using a rapid lithium triethylborohydride reduction of Ni(2+) and Ru(3+) precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). We found that the as-prepared Ni-Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni-Ru alloy NPs, and in particular the Ni(0.74)Ru(0.26) sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core-shell NPs. The hydrolysis activation energy for the Ni(0.74)Ru(0.26) alloy catalyst was measured to be approximately 37 kJ mol(-1). This value is considerably lower than the values measured for monometallic Ni (≈70 kJ mol(-1)) and Ru NPs (≈49 kJ mol(-1)), and for Ni@Ru (≈44 kJ mol(-1)), and is also lower than the values of most noble-metal-containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal.

Thermal stability and dispersion of CeO 2 supported on Al 2 O 3 is greatly improved by insertion of ZrO 2 into the CeO 2 lattice. It is shown that homogeneous nanosized Ce x Zr 1-x O 2 solid solutions can be prepared on the Al 2 O 3 surface by using a citrate complexation synthesis method. Investigation of effects of Ce x Zr 1-x O 2 composition and loading of the Ce 0.2 Zr 0.8 O 2 phase on thermal stability and nanostructure of the prepared materials revealed that strong interactions between the supported phase and Al 2 O 3 are induced by the high-temperature treatment. High contents of ZrO 2 , choice of the Ce x Zr 1-x O 2 precursors, and loading of the mixed oxide are critical factors leading to nanocomposite systems with high thermal and structural stability, consisting of particles of Ce 0.2 Zr 0.8 O 2 as small as 9-20 nm in close contact with a θ-Al 2 O 3 matrix even after calcination at 1373 K. The enhanced stability of the present materials was confirmed also under hydrothermal conditions.

Core-shell structured Ni@Ru bimetallic nanoparticles are demonstrated as a bifunctional nanoplatform system for the hydrolysis reaction of ammonia-borane and also for magnetic separation.

No abstract

Hollow Ru nanoparticles with ~14 nm diameter and ~2 nm shell thickness are reported for the first time, by removal of Ni from the delicately designed Ni@Ru core@shell NPs. Such hollow Ru NPs exhibit enhanced catalytic activity in the dehydrogenation of ammonia borane with respect to solid ones.