Narrow Results

We investigated the stability of aminoborane with electron withdrawing groups such as –CF₃ and –CN using density functional theory calculations. For the electron withdrawing groups of –CF₃ and –CN, we observed similar tendency of B–N bond strength: electron withdrawal from the N atom reduces the strength of B–N bonds. And we find that the electron density localized on B and N is also reduced through the charge analysis. These electron withdrawing substituents make cyclic dimers and trimers stabilized less than electron donating ones.

By adding surfactant polyvinyl alcohol (PVA) and controlling the preparation process, we successfully synthesized Co–Mo catalysts. For further improving the dispersion, reduced graphene oxide sheets as catalyst carrier were introduced to synthesize Co–Mo@rGO composite catalyst as highly efficient catalysts for hydrolytic dehydrogenation of ammonia borane. The introduction of Mo for preparing Co–Mo@rGO catalyst helped to form alloy catalyst with better structure, better dispersity and smaller particle size. When the molar ratio of Co and Mo was 0.75:0.25, the bimetallic composite catalyst exhibited superior activity with TOF value of 16.29mol${}_{\mathrm{\text{H2}}}\cdot {\mathrm{\text{min}}}^{-1}\cdot {{\mathrm{\text{mol}}}_{\mathrm{\text{Co-Mo}}}}^{-1}$. The activation energy of the reaction was calculated to be 43.72kJ$\cdot {\mathrm{\text{mol}}}^{-1}$. Furthermore, the reusability tests reveal that waxberry-like Co–Mo still show good catalytic activity with 80.3% of their initial activity in five successive runs. The enhanced catalytic activities were due to the synergistic interaction between graphene sheets and waxberry-like Co–Mo NPs, which was beneficial to improve the dispersion and stability of bimetallic NPs. Also, ligand effects on the formation of waxberry-like structure and amorphous state further promoted the catalytic activity.

In this work, we investigated fabrication of porous nickel–silica composite particles through catalytic hydrogen evolution reaction from aqueous solution including sodium borohydride and ammonia borane. Aggregated nickel species were observed in the samples with high nickel content from scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) results, indicating that dispersion of active nickel species was significantly influenced by nickel content. The dispersion influenced hydrogen evolution amount and rate from aqueous solution including sodium borohydride and ammonia borane, and the samples with highly dispersed active nickel species showed high hydrogen evolution amount. The particles after the hydrogen evolution process showed significantly high specific surface area with large number of nanopores. UV-Vis spectra of the samples after the hydrogen evolution process indicated that the particles with high hydrogen evolution amount from aqueous solution including sodium borohydride and ammonia borane included high amount of reduced nickel species.

As promising hydrogen carriers, sodium borohydride (SB) and ammonia borane (AB) can controllably release pure hydrogen by means of catalytic hydrolysis at mild condition. In this work, we introduced a novel and facile method for transformation of commercial nickel foam (NF) to highly active 3D porous Ni–Zn catalyst. The method consisted of three steps including electroplating zinc on NF, alloying treatment and chemical etching. Catalyst microstructure and component were characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Hydrogen generation measurement indicates that the prepared Ni–Zn catalyst is highly efficient for catalytic hydrolysis of SB and AB to generate hydrogen. Moreover, recycling performance of the catalyst was also investigated.