Hydrolytic dehydrogenation of amine-boranes catalyzed by graphene supported rhodium–nickel nanoparticles

The Hydrogen-Storage Challenge: Nanoparticles for Metal-Catalyzed Ammonia Borane Dehydrogenation

Dihydrogen is one of the sustainable energy vectors envisioned for the future. However, the rapidly reversible and secure storage of large quantities of hydrogen is still a technological and scientific challenge. In this context, this review proposes a recent state-of-the-art on H₂ production capacities from the dehydrogenation reaction of ammonia borane (and selected related amine-boranes) as a safer solid source of H₂ by hydrolysis (or solvolysis), catalyzed by nanoparticle-based systems. The review groups the results according to the transition metals constituting the catalyst with a mention to their current cost and availability. This includes the noble metals Rh, Pd, Pt, Ru, Ag, as well as cheaper Co, Ni, Cu, and Fe. For each element, the monometallic and polymetallic structures are presented and the performances are described in terms of turnover frequency and recyclability. The structure-property links are highlighted whenever possible. It appears from all these works that the mastery of the preparation of catalysts remains a crucial point both in terms of process, and control and understanding of the electronic structures of the elaborated nanomaterials. A particular effort of the scientific community remains to be made in this multidisciplinary field with major societal stakes.

Ultrafine RhNi Nanocatalysts Confined in Hollow Mesoporous Carbons for a Highly Efficient Hydrogen Production from Ammonia Borane

Ammonia borane (AB) has received growing research interest as one of the most promising hydrogen-storage carrier materials. However, fast dehydrogenation of AB is still limited by sluggish catalytic kinetics over current catalysts. Herein, highly uniform and ultrafine bimetallic RhNi alloy nanoclusters encapsulated within nitrogen-functionalized hollow mesoporous carbons (defined as RhNi@NHMCs) are developed as highly active, durable, and selective nanocatalysts for fast hydrolysis of AB under mild conditions. Remarkable activity with a high turnover frequency (TOF) of 1294 mol_H2 mol_Rh^-1 min^-1 and low activation energy (E_a) of 18.6 kJ mol^-1 is observed at room temperature, surpassing the previous Rh-based catalysts. The detailed mechanism studies reveal that when catalyzed by RhNi@NHMCs, a covalently stable O-H bond by H₂O first cleaves in electropositive H* and further attacks B-H bond of AB to stoichiometrically produce 3 equiv of H₂, whose catalytic kinetics is restricted by the oxidation cleavage of the O-H bond. Compositional and structural features of RhNi@NHMCs result in synergic electronic, functional, and support add-in advantages, kinetically accelerating the cleavage of the attacked H₂O (O-H bond) and remarkably promoting the catalytic hydrolysis of AB accordingly. This present work represents a new and effective strategy for exploring high-performance supported metal-based alloy nanoclusters for (electro)catalysis.

Synergism of ultrafine RuCo alloy nanoparticles on graphite carbon nitride for an efficient ammonia borane hydrolysis

Synergism of ultrafine RuCo alloy nanoparticles on graphite carbon nitride were achieved for an efficient ammonia borane hydrolysis.

Surfactant-aided synthesis of RhCo nanoclusters as highly effective and recyclable catalysts for the hydrolysis of methylamine borane and dimethylamine borane

In this study, the first ever and easy surfactant-aided synthesis of CTAB-stabilized Rh_0.63Co_0.37 and their employment as highly efficient, cost-saving, and recyclable catalysts to generate hydrogen from the hydrolysis of MeAB and DMAB are reported.

Polypyrrole-multi walled carbon nanotube hybrid material supported Pt NPs for hydrogen evolution from the hydrolysis of MeAB at mild conditions

Herein, we report a facile method for the preparation of polypyrrole-multi walled carbon nanotube hybrid material including Pt nanoparticles (Pt@PPy-MWCNT NPs) and the use in methylamine borane (MeAB) for hydrolysis reaction at mild conditions. The prepared catalyst of Pt@PPy-MWCNT NPs was characterized by some advanced analytical methods. The catalytic experiments showed the Pt@PPy-MWCNT NPs can catalyze MeAB in aquatic solution with high catalytical performance at mild conditions. The reaction rate of catalytic hydrolysis with Pt@PPy-MWCNT NPs was found to be -d[CH3NH2BH3]/dt = + d[H2]/3dt = kobs[Pt@PPy-MWCNT]1.19 [MeAB]0.88. The TOF value for the hydrolysis of MeAB catalyzed with Pt@PPy-MWCNT NPs was detected to be 10234.2 1/h (170.57 1/min) which is very high compared with TOF values found for other catalysts. Enthalpy, entropy and activation energy for the hydrolysis of MeAB were calculated to be 31.57 kJ mol-1, -119.97 J mol-1 K and 34.27 kJ mol-1, respectively.

Single-walled carbon nanotube supported Pt-Ru bimetallic superb nanocatalyst for the hydrogen generation from the methanolysis of methylamine-borane at mild conditions

Several metal nanoparticle based catalysts have been synthesized for catalyzing the hydrogen production process by hydrolysis of methylamine-borane (MeAB). However, there was only one study that catalyzes the producing of hydrogenvia the methanolysis of MeAB, and it was carried out by our research group. For this reason, in this work, a new catalyst system entitled by single-walled carbon nanotube (SWCNT) supported bimetallic platinum-ruthenium nanoparticles were developed and called as PtRu@SWCNT. These NPs were characterized by several techniques (XRD, XPS, Raman, and TEM), and they were performed for the methanolysis of MeAB with high catalytic activity. The prepared PtRu@SWCNT NPs were also tested in the methanolysis of MeAB at different parameters including different temperatures, catalyst and substrate concentrations, and reusability performance. Experimental results revealed that the new PtRu@SWCNT NPs had excellent catalytic activity and reusability for removing of hydrogen from the methanolysis of MeAB at ambient conditions. According to the obtained data, the turnover frequency is 136.25 mole H₂/mole PtRu × min, and the activation energy (Ea) is 17.29 kJ/mole. More than 99% of conversion was observed at room temperature.

Influence of the Water/Titanium Alkoxide Ratio on the Morphology and Catalytic Activity of Titania-Nickel Composite Particles for the Hydrolysis of Ammonia Borane

This work reports the influence of the water/titanium alkoxide ratio during the preparation of titania–nickel composite particles on their morphology and catalytic activity toward the hydrolysis of ammonia borane. The titania–nickel composite particle catalysts were fabricated by using a sol‐gel method, followed by an activation process in aqueous solution containing sodium borohydride and ammonia borane. From the scanning electron microscopy images and pore‐size distributions calculated from nitrogen sorption data, the particle dispersion was significantly enhanced at ratios above 6000, and increased with increasing water/titanium alkoxide ratio. Stoichiometric amounts of hydrogen were evolved in the presence of all of the prepared titania–nickel composite particle catalysts. The particle dispersion influenced the hydrogen evolution rate from aqueous ammonia borane solution, and the samples with the most highly dispersed particles showed the highest hydrogen evolution rate. The most active catalyst showed an apparent activation energy comparable to that of other reported catalysts and high cycle ability for the hydrolysis of ammonia borane.

Cu/Ni nanoparticles supported on TiO2(B) nanotubes as hydrogen generation photocatalysts via hydrolysis of ammonia borane

Cu_0.64Ni_0.36-TiO₂(B) NTs with a lower bandgap energy show a high H₂ generation rate in the hydrolysis of AB.

Hyper-cross-linked polymer supported rhodium: an effective catalyst for hydrogen evolution from ammonia borane

In situ formation of HCP-PPh₃-Rh and concomitant catalytic AB hydrolysis was performed for efficient hydrogen generation from AB hydrolysis.

Synthesized polyvidone-stabilized Rh(0) nanoparticles catalyzed the hydrolytic dehydrogenation of methylamine-borane in ambient conditions

Polyvidone (PVP40)-stabilized Rh nanoparticles (Rh@PVP40) were synthesized via a classical alcohol reduction technique and were characterized by carrying out TEM, HR-TEM, TEM/EDX, P-XRD analysis, UV/Vis and XPS spectroscopy investigations.