Graphene-Supported Trimetallic Core-Shell Cu@CoNi Nanoparticles for Catalytic Hydrolysis of Amine Borane

Waste-biomass-derived activated carbon supported Co-Cu-P nanocatalysts for hydrolytic dehydrogenation of ammonia borane

Hydrolytic dehydrogenation of ammonia borane is a significant and promising approach for on-site hydrogen production at ambient conditions, and developing highly efficient and low-cost catalysts has attracted considerable attention. Herein, waste-biomass-derived activated carbon (AC) was prepared by hydrothermal carbonization and alkali-assisted activation, and non-precious bimetal phosphides (Co-Cu-P) nanocatalysts with a series of different Co/Cu ratios were synthesized on the AC surface through in situ phosphidation method. Owing to the synergetic effects, the optimal Co_0.8Cu_0.2P/AC presents an outstanding turnover frequency of 26.5 min^-1 (25 °C), which is much higher than that of many reported catalysts. The reaction activation energy was measured to be 34.6 kJ mol^-1. Benefiting from the ferromagnetic nature of the phosphides, the Co_0.8Cu_0.2P/AC can be magnetically separated and reused again. After recycling six times, the catalyst still retains 72% of the initial activity, thus indicating great potential for practical applications.

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.

Current Research Trends and Perspectives on Solid-State Nanomaterials in Hydrogen Storage

Hydrogen energy, with environment amicable, renewable, efficiency, and cost-effective advantages, is the future mainstream substitution of fossil-based fuel. However, the extremely low volumetric density gives rise to the main challenge in hydrogen storage, and therefore, exploring effective storage techniques is key hurdles that need to be crossed to accomplish the sustainable hydrogen economy. Hydrogen physically or chemically stored into nanomaterials in the solid-state is a desirable prospect for effective large-scale hydrogen storage, which has exhibited great potentials for applications in both reversible onboard storage and regenerable off-board storage applications. Its attractive points include safe, compact, light, reversibility, and efficiently produce sufficient pure hydrogen fuel under the mild condition. This review comprehensively gathers the state-of-art solid-state hydrogen storage technologies using nanostructured materials, involving nanoporous carbon materials, metal-organic frameworks, covalent organic frameworks, porous aromatic frameworks, nanoporous organic polymers, and nanoscale hydrides. It describes significant advances achieved so far, and main barriers need to be surmounted to approach practical applications, as well as offers a perspective for sustainable energy research.

Noble-metal-free nanocatalysts for hydrogen generation from boron- and nitrogen-based hydrides

We focus on the recent advances in non-noble metal catalyst design, synthesis and applications in dehydrogenation of chemical hydrides (e.g. NaBH₄, NH₃BH₃, NH₃, N₂H₄, N₂H₄BH₃) due to their high hydrogen contents and CO-free H₂ production.

TiN nanotube supported Ni catalyst Ni@TiN-NTs: experimental evidence of structure–activity relations in catalytically hydrolyzing ammonia borane for hydrogen evolution

With commercial TiO₂ as the precursor, titanium nitride nanotubes (TiN-NTs) were fabricated through a hydrothermal – ammonia nitriding route, and next non-noble metal nanosized Ni particles were evenly and firmly anchored on the surface of the TiN-NTs via a PVP-mediated non-aqueous phase reduction–deposition strategy, to obtain the supported catalyst Ni@TiN-NTs. The X-ray powder diffraction (PXRD), field emission scanning and transmission electron microscopy (FE-SEM/TEM) and specific surface area measurements were used to characterize and analyze the phase composition, surface microstructure and morphological features of the product. The catalytic activity of the Ni@TiN-NTs for hydrolyzing ammonia borane to generate hydrogen (H₂) under different conditions was evaluated systematically. The results reveal that the as-fabricated TiN-NTs are composed of TiN and a small amount of TiN_xO_y with the approximate molar atomic ratio of Ti to N at 1 : 1, existing as hollow microtubules with mean tube diameter of 130 nm and length of about 1 μm. Via in situ reduction and deposition, Ni nanoparticles can be uniformly anchored on the surface of TiN-NTs. The catalytic activities of Ni(x)@TiN-NTs with different Ni loading amounts are all higher than that of single metal Ni nanoparticles. The temperature has a positive effect on the catalytic activity of Ni(20)@TiN-NTs, and its total turnover frequency for hydrolyzing ammonia borane is 11.73 mol(H₂) (mol Ni)⁻¹ min⁻¹, with an apparent activation energy of 52.05 kJ mol⁻¹ at 303 K. After 5 cycles, the Ni(20)@TiN-NTs catalyst still maintains 87% of the initial catalytic activity. It could be suggested that these tactics can also be extended to the fabrication of other metal or alloy catalysts supported by TiN-NTs, with great application potential and development prospects.

Titanium nitride nanotubes (TiN-NTs) were fabricated using a hydrothermal – ammonia nitriding route, and non-noble metal nanosized Ni particles were anchored on the surface via a non-aqueous phase reduction–deposition strategy, to obtain the supported catalyst Ni@TiN-NTs.

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.

Hexagonal CuCo₂O₄ Nanoplatelets, a Highly Active Catalyst for the Hydrolysis of Ammonia Borane for Hydrogen Production

Catalytic hydrolysis of ammonia borane (AB) has been considered as an effective and safe method to generate hydrogen. Development of highly active and low-cost catalysts is one of the key tasks for this technology. In this work, hexagonal CuCo₂O₄ nanoplatelets with a thickness of approximately 55 nm were prepared. In AB hydrolysis, those nanoplatelets exhibited ultrahigh catalytic activity with turnover frequency (TOF) of 73.4 molhydrogen min-1 molcat-1. As far as we know, this is one of the highest TOF values ever reported for non-noble metal catalysts. In addition, the effects of viscosity and different alkalis on the hydrolysis were also investigated. It is revealed that high viscosity of the reaction medium will retard the hydrolysis reaction. The presence of NaOH, KOH, and Na₂CO₃ in the reaction solution is favorable for hydrolytic process. In contrast, NH₃·H₂O will slow down the hydrolysis rate of ammonia borane. This work can provide some novel insight into the design of catalysts with both high performance and low cost. Besides, some findings in the present study can also offer us some information about how to improve the hydrolysis rates by optimizing the hydrolysis condition.

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.

Construction of cost-effective bimetallic nanoparticles on titanium carbides as a superb catalyst for promoting hydrolysis of ammonia borane

Bimetallic cost-effective CoNi nanoparticles (NPs) are conveniently supported on titanium carbides (MXene) by a simple one-step wet-chemical method. The synthesized CoNi/MXene catalysts are characterized by XPS, TEM, STEM-HAADF and ICP-AES. The as-prepared CoNi NPs with a size of 2.8 nm are well dispersed on the MXene surface. It is found that among the CoNi bimetallic system, Co_0.7Ni_0.3 shows the best performance toward catalyzing ammonia borane (AB) decomposition with a turnover frequency value of 87.6 mol_H2 mol_cat⁻¹ min⁻¹ at 50 °C. The remarkable catalytic performance is attributed to the mild affiliation of MXene to NPs, which not only stabilizes NPs to maintain a good dispersion but also leaves sufficient surface active sites to facilitate the catalytic reaction.

Bimetallic cost-effective CoNi nanoparticles are supported on MXene by a simple one-step wet-chemical method. The Co_0.7Ni_0.3/MXene shows the best performance toward catalyzing AB decomposition with TOF of 87.6 mol_H2 mol_cat⁻¹ min⁻¹ at 50 °C.

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.

Core-shell nanoparticles: synthesis and applications in catalysis and electrocatalysis

Core-shell nanoparticles (CSNs) are a class of nanostructured materials that have recently received increased attention owing to their interesting properties and broad range of applications in catalysis, biology, materials chemistry and sensors. By rationally tuning the cores as well as the shells of such materials, a range of core-shell nanoparticles can be produced with tailorable properties that can play important roles in various catalytic processes and offer sustainable solutions to current energy problems. Various synthetic methods for preparing different classes of CSNs, including the Stöber method, solvothermal method, one-pot synthetic method involving surfactants, etc., are briefly mentioned here. The roles of various classes of CSNs are exemplified for both catalytic and electrocatalytic applications, including oxidation, reduction, coupling reactions, etc.

Highly efficient hydrogen generation from methanolysis of ammonia borane on CuPd alloy nanoparticles

A low-cost and facile route has been developed for the synthesis of monodisperse CuPd nanoparticles with tunable composition. (Scanning transmission electron microscopy-energy-dispersive x-ray spectroscopy) STEM-EDX results verified the structure of the alloy for the obtained nanoparticles. These CuPd nanoparticles supported on carbon were active catalysts for hydrogen generation from the methanolysis of ammonia borane (AB) at room temperature, and their activities were closely related with the compositions. Cu48Pd52 NPs exhibited the highest activity among the tested catalysts. Moreover, their activity can be further improved by thermal annealing at 300 °C under nitrogen flow, with a very high total turnover frequency value of 53.2 min(-1). The reusability test indicated that the Cu48Pd52/C catalyst retains 86% of its initial activity and 100% conversion after 8 cycles. The catalyst, which features lost cost and high efficiency, may help move forward the practical application of AB as a sustainable hydrogen storage material.

Graphene-supported metal/metal oxide nanohybrids: synthesis and applications in heterogeneous catalysis

This minireview outlines recent advances in the design and catalytic applications of graphene-supported metal/metal oxide nanohybrids.