Ni nanoparticles modified with a Mo dopant have been synthesized on graphene sheets via a facile chemical reduction route, which show the highest catalytic activity reported to date for noble-metal-free catalysts for hydrogen evolution from the hydrolysis of ammonia borane with a turnover frequency value as high as 66.7 mol H₂ (mol metal min)⁻¹.

Ultrafine copper nanoparticles (Cu NPs) within porous silica nanospheres (Cu@SiO₂) were prepared via a simple one-pot synthetic route in a reverse micelle system and characterized by SEM, TEM, EDX, XRD, N₂ adsorption-desorption, CO-TPD, XPS, and ICP methods. The characterized results show that ultrafine Cu NPs with diameter of around 2 nm are effectively embedded in the center of well-proportioned spherical SiO₂ NPs of about 25 nm in diameter. Compared to commercial SiO₂ supported Cu NPs, SiO₂ nanospheres supported Cu NPs, and free Cu NPs, the synthesized core-shell nanospheres Cu@SiO₂ exhibit a superior catalytic activity for the hydrolytic dehydrogenation of ammonia borane (AB, NH₃BH₃) and hydrazine borane (HB, N₂H₄BH₃) under ambient atmosphere at room temperature. The turnover frequencies (TOF) for the hydrolysis of AB and HB in the presence of Cu@SiO₂ nanospheres were measured to be 3.24 and 7.58 mol H₂ (mol Cu min)⁻¹, respectively, relatively high values for Cu nanocatalysts in the same reaction. In addition, the recycle tests show that the Cu@SiO₂ nanospheres are still highly active in the hydrolysis of AB and HB, preserving 90 and 85% of their initial catalytic activity even after ten recycles, respectively.

Hydrogen is a potentially ideal alternative energy source for both environmental and economic reasons. The development of sustainable, efficient, and economical catalysts towards hydrogen generation from hydrogen storage materials (e.g., ammonia borane, AB) has been one of the active and challenging research areas. In this work, noble-metal-free CuCoMo nanoparticles (NPs) without any surfactant or support have been prepared via a facile co-reduction method at room temperature and used as highly efficient catalysts for hydrogen generation from an aqueous AB solution. Compared to their monometallic and bimetallic counterparts, the obtained trimetallic Cu_0.72Co_0.18Mo_0.1 NPs exhibit the highest catalytic activity for the hydrolysis of AB with a total turnover frequency (TOF) value of 46.0 min⁻¹ at room temperature under ambient atmosphere. The Cu_0.72Co_0.18Mo_0.1 NPs only needed 0.63 min to completely hydrolyse AB in the presence of a basic solution (NaOH, 1 M) with a TOF value as high as 119.0 min⁻¹ at room temperature, which is among the highest values of all the noble-metal-free catalysts ever reported for the same reaction, wherein NaOH plays an important role in improving the catalytic activity. In addition, it is found that the hydrogen generation rate can be improved by adding a base (e.g., NaOH, KOH, etc.) into the reaction solution, while the presence of NH₄ ⁺ species (e.g., NH₃·H₂O, NH₄Cl, etc.) is unfavorable for the hydrolysis of AB.

Development of low-cost and high-performance catalysts for hydrogen generation via hydrolysis of ammonia borane (NH₃BH₃, AB) is a highly desirable pathway for future hydrogen utilization. In this work, Ni nanocatalysts doped with CeO_x and supported on graphene (Ni-CeO_x/graphene) were synthesized via a facile chemical reduction route and applied as robust catalysts for the hydrolysis of AB in aqueous solution at room temperature. The as-synthesized Ni-CeO_x/graphene nanocomposites (NCs) exhibited excellent catalytic activity with a turnover frequency (TOF) as high as 68.2 min⁻¹, which is 49-fold higher than that for a simple Ni nanoparticle catalyst and is among the highest values reported for non-noble metal catalysts in AB hydrolysis. The development of efficient and low-cost Ni-CeO_x/graphene catalysts enhances the feasibility of using ammonia borane as a chemical hydrogen storage material, which may find application ina hydrogen fuel-cell based economy.

Amorphous CeO_x-doped Rh-Ni NPs grown on reduced graphene oxide nanosheets have been used as highly efficient and recyclable catalysts for complete hydrogen generation from aqueous solution of N₂H₄BH₃or N₂H₄.