Mehmet Yurderi

Palladium(0) nanoparticles supported on hydroxyapatite nanospheres: active, long-lived, and reusable nanocatalyst for hydrogen generation from the dehydrogenation of aqueous ammonia-borane solution

Among the solid materials considered in the chemical hydrogen storage, ammonia–borane (NH3BH3) appears to be one of the promising candidates as it can release hydrogen throughout hydrolysis in the presence of suitable catalyst under mild conditions. Herein we report, for the first time, the preparation and characterization of palladium(0) nanoparticles supported on nanohydroxyapatite and their catalytic use in the hydrolysis of ammonia–borane under air at room temperature. These new palladium(0) nanoparticles were generated in situ during the catalytic hydrolysis of ammonia–borane starting with palladium(II) immobilized nanohydroxyapatite. The preliminary characterization of the palladium(0) nanoparticles supported on nanohydroxyapatite was done by the combination of complimentary techniques, which reveals that the formation of well-dispersed Pd(0)NPs nanoparticles (1.41xa0±xa00.52xa0nm) on the surface of hydroxyapatite nanospheres (60–150xa0nm). The resulting palladium nanocatalyst achieves hydrogen generation from the hydrolysis of ammonia–borane with an initial turnover frequency value (TOF) of 11xa0mol H2xa0mol−1 Pdxa0×xa0min at room temperature under air. In addition to their high activity, the catalytic lifetime experiment showed that they can also act as a long-lived heterogeneous catalyst for this reaction (TTONxa0=xa014,200xa0mol H2xa0mol−1 Pd) at room temperature under air. More importantly, nanohydroxyapatite-supported palladium(0) nanoparticles were found to be highly stable against to leaching and sintering throughout the catalytic runs that make them isolable, bottleable, and reusable heterogeneous catalyst for the hydrolysis of ammonia–borane.

Liquid Phase Chemical Hydrogen Storage: From Recent Developments to Future Objectives

Abstract The hydrolytic dehydrogenation of aqueous boron–nitrogen (B–N)-based compounds such as NaBH4 and NH3BH3 has received much attention, and because of their high hydrogen content they have been shown to be promising hydrogen carriers for storage and transportation. Formic acid (HCOOH), a major product formed in biomass processing, has been intensely investigated for liquid phase chemical hydrogen storage owing to its high energy density, stability, and nontoxicity. In this chapter, we focus on advances in research on hydrogen storage and release of these liquid phase hydrogen storage materials. Main advantages and drawbacks of these systems in liquid phase hydrogen storage are also discussed.

Amine-functionalized graphene nanosheet-supported PdAuNi alloy nanoparticles: efficient nanocatalyst for formic acid dehydrogenation

Formic acid (HCOOH), a major by-product of biomass processing with high energy density, stability and non-toxicity, has a great potential as a safe and a convenient liquid hydrogen (H2) storage material for combustion engines and fuel cell applications. However, high-purity hydrogen release from the catalytic decomposition of aqueous formic acid solution at desirable rates under mild conditions stands as a major challenge that needs to be solved for the practical use of formic acid in on-demand hydrogen generation systems. Described herein is a new nanocatalyst system comprised of 3-aminopropyltriethoxysilane-functionalized graphene nanosheet-supported PdAuNi alloy nanoparticles (PdAuNi/f-GNS), which can reproducibly be prepared by following double solvent method combined with liquid-phase chemical reduction, all at room temperature. PdAuNi/f-GNS selectively catalyzes the decomposition of aqueous formic acid through the dehydrogenation pathway (∼100% H2 selectivity), in the absence of any promoting additives (alkali formates, Bronsted bases, Lewis bases, etc.). PdAuNi/f-GNS nanocatalyst provides CO-free H2 generation with a turnover frequency of 1090 mol H2 mol metal−1 h−1 in the additive-free dehydrogenation of formic acid at almost complete conversion (≥92%) even at room temperature. The catalytic activity provided by PdAuNi/f-GNS nanocatalyst is higher than those obtained with the heterogeneous catalysts reported to date for the additive-free dehydrogenation of formic acid. Moreover, PdAuNi/f-GNS nanoparticles show high durability against sintering, clumping and leaching throughout the catalytic runs, so that the PdAuNi/f-GNS nanocatalyst retains almost its inherent catalytic activity and selectivity at the end of the 10th recycle.

Atomic Layer Deposition of Ruthenium Nanoparticles on Electrospun Carbon Nanofibers: A Highly Efficient Nanocatalyst for the Hydrolytic Dehydrogenation of Methylamine Borane

We report the fabrication of a novel and highly active nanocatalyst system comprising electrospun carbon nanofiber (CNF)-supported ruthenium nanoparticles (NPs) (Ru@CNF), which can reproducibly be prepared by the ozone-assisted atomic layer deposition (ALD) of Ru NPs on electrospun CNFs. Polyacrylonitrile (PAN) was electropsun into bead-free one-dimensional (1D) nanofibers by electrospinning. The electrospun PAN nanofibers were converted into well-defined 1D CNFs by a two-step carbonization process. We took advantage of an ozone-assisted ALD technique to uniformly decorate the CNF support by highly monodisperse Ru NPs of 3.4 ± 0.4 nm size. The Ru@CNF nanocatalyst system catalyzes the hydrolytic dehydrogenation of methylamine borane (CH3NH2BH3), which has been considered as one of the attractive materials for the efficient chemical hydrogen storage, with a record turnover frequency of 563 mol H2/mol Ru × min and an excellent conversion (>99%) under air at room temperature with the activation energy ( Ea) of 30.1 kJ/mol. Moreover, Ru@CNF demonstrated remarkable reusability performance and conserved 72% of its inherent catalytic activity even at the fifth recycle.