Metal Ruthenate Perovskites as Heterogeneous Catalysts for the Hydrolysis of Ammonia Borane

Reducible tungsten(VI) oxide-supported ruthenium(0) nanoparticles: highly active catalyst for hydrolytic dehydrogenation of ammonia borane

Reducible WO3 powder with a mean diameter of 100 nm is used as support to stabilize ruthenium(0) nanoparticles. Ruthenium(0) nanoparticles are obtained by NaBH4 reduction of ruthenium(III) precursor on the surface of WO3 support at room temperature. Ruthenium(0) nanoparticles are uniformly dispersed on the surface of tungsten(VI) oxide. The obtained Ru0/WO3 nanoparticles are found to be active catalysts in hydrolytic dehydrogenation of ammonia borane. The turnover frequency (TOF) values of the Ru0/WO3 nanocatalysts with the metal loading of 1.0%, 2.0%, and 3.0% wt. Ru are 122, 106, and 83 min-1, respectively, in releasing hydrogen gas from the hydrolysis of ammonia borane at 25.0 °C. As the Ru0/WO3 (1.0% wt. Ru) nanocatalyst with an average particle size of 2.6 nm provides the highest activity among them, it is extensively investigated. Although the Ru0/WO3 (1.0% wt. Ru) nanocatalyst is not magnetically separable, it has extremely high reusability in the hydrolysis reaction as it preserves 100% of initial catalytic activity even after the 5th run of hydrolysis. The high activity and reusability of Ru0/WO3 (1.0% wt. Ru) nanocatalyst are attributed to the favorable metal-support interaction between the ruthenium(0) nanoparticles and the reducible tungsten(VI) oxide. The high catalytic activity and high stability of Ru0/WO3 nanoparticles increase the catalytic efficiency of precious ruthenium in hydrolytic dehydrogenation of ammonia borane.

Coffee ground derived biochar embedded Ov-NiCoO2 nanoparticles for efficiently catalyzing a boron‑hydrogen bond break

The catalytic boron‑hydrogen bond break is usually regarded as an important reaction both in the area of environment treatment and hydrogen energy, attracting increasing attention in the past decades. Due to the limitation of conventional noble metal-based catalyst, cost-effective transition metal-based catalysts with high activity have been recently developed to become the promising candidates. Herein, the coffee ground waste was utilized as the biochar substrate loaded with ultrafine NiCoO₂ nanoparticles. The abundant function groups on the biochar substrate efficiently adsorbed the metal ions and confined the crystal growth spatially, making the NiCoO₂ nanoparticles highly dispersed on the surface. Moreover, the oxygen vacancies were further created in the catalysts by a vacuum-calcination strategy to boost their catalytic activity towards boron‑hydrogen bond break both in the systems of 4-nitrophenol reduction by NaBH₄ and hydrogen release from NH₃BH₃. The results indicated that the moderate presence of oxygen vacancies could effectively accelerate the boron‑hydrogen bond break and the catalytic activity performed a satisfied stability during several recycles. The theoretical calculation method was adopted to analysis and discuss the mechanism within this process. This design strategy on active catalysts not only offered a novel solution of biowaste resource reuse but also demonstrated the significant role of oxygen vacancies in energy and environmental catalysis.

SiO2-Encompassed Co@N-Doped Porous Carbon Assemblies as Recyclable Catalysts for Efficient Hydrolysis of Ammonia Borane

The development of earth-abundant catalysts for efficient hydrolysis of ammonia borane is of great importance in the conversion and utilization of hydrogen energy. Here, we report the synthesis of SiO₂-encompassed Co@N-doped porous carbon assemblies as a new type of recyclable catalyst for the purpose by calcination of zeolitic imidazolate framework-67@SiO₂ microtubes at high temperatures under an N₂ atmosphere. We find that the surface layer of SiO₂ in the precursor microtubes is essential for the production of efficient catalysts by supplying an additional surface for Co nanoparticle dispersion in an effort to reduce their size. In addition, the SiO₂ layer renders a highly ordered arrangement of Co@N-doped porous carbon within the catalysts, possibly allowing the ease of mass transfer of ammonia borane within the catalysts. The optimized catalysts obtained via calcination at 800 °C show a set of remarkable catalytic benefits, including a high hydrogen generation rate of 8.4 mol min^-1 mol_(Co)^-1, a relatively low activation energy of 36.1 kJ mol^-1, and a remarkable reusability (at least 10 times). Our results can provide new insight into the design and synthesis of highly ordered SiO₂-supported catalysts for different reactions.

Assessing the Potential of Sodium 1-Oxa-nido-dodecaborate NaB11H12O for Energy Storage

In the recent years, polyborate anions have been considered as possible candidates for energy. In aqueous solutions, they have been studied as either hydrogen carriers or anodic fuels. In the solid state (as an alkali salt), they have been seen as solid electrolytes. Herein, we focus on sodium 1-oxa-nido-dodecaborate NaB₁₁H₁₂O, a novel possible candidate for the aforementioned applications. The compound is soluble in water, and its stability depends on pH: under acidic conditions, it readily hydrolyzes while liberating hydrogen, and under alkaline conditions, it is stable, which is a feature searched for an anodic fuel. Over bulk platinum, gold, or silver electrode, oxidation takes place. The best performance has been noticed for the silver electrode. In the solid state, NaB₁₁H₁₂O shows Na⁺ conductivity at a high temperature of up to 150 °C. All of these properties are presented in detail, and hereafter they are discussed while giving indications of what have to be developed to open up more realistic prospectives for NaB₁₁H₁₂O in energy.