Demonstration of Controlled Hydrogen Release Using Rh@GQDs during Hydrolysis of NH3BH3

Anion modulation enhances the internal electric field of CuCo2O4 to improve the catalysis in ammonia borane hydrolysis

Ammonia borane (NH3BH3, AB) is considered a promising chemical hydrogen storage material. The development of efficient, stable, and economical catalysts for AB hydrolysis is essential for realizing the hydrogen energy economy. In this study, a series of p-p heterojunction catalysts, labeled M (P/S/Cl)-CuCo2O4, were fabricated using the high-temperature vapor phase method to achieve anionic interface gradient doping. Due to the differences in electronegativity among the anions P/S/Cl-O, electron-rich and electron-deficient regions are generated at the interface, inducing the formation of local p-p heterojunctions with built-in electric fields (BIEF). The difference in work function (ΔWf) at the interface enhances the strength of the BIEF. Because of the positive influence of the BIEF on the adsorption of intermediates and interfacial behavior, the catalytic performance of P-CuCo2O4, characterized by a hydrogen evolution rate (HER) of 1125 mLH2(gcat·min)-1, is significantly higher than that of intrinsic CuCo2O4, which has an HER of 705 mLH2(gcat·min)-1. Its apparent activation energy of only 32.25 kJ/mol is superior to that of previous non-precious metal catalysts. Density functional theory (DFT) further confirms that the construction and enhancement of the BIEF can reduce the band gap, accelerate electron transfer, regulate the metal d-band center, and enhance the adsorption of AB and H2O molecules. This process facilitates the elongation and breakage of the O-H bond length in H2O and the B-H bond length in AB, thereby promoting the release of H2.

Encapsulating Ammonia Borane in Cobalt Decorated Kaolinite Monolith Aerogel for Hydrogen Storage and Controllable Release

Achieving the "on-off" control of hydrogen release remains a huge challenge in efficiently harnessing hydrogen energy on demand. In this work, a controlled hydrogen production strategy is proposed. Hydrogen carrier ammonia borane (AB) and Co catalyst are loaded into kaolinite aerogel (KA) to obtain a composite AB@Co/KA monolith. The results show that Co particles with surface-oxidized species are uniformly decorated on the surface of aerogel, and AB can fill the pores of aerogel to form a composite hydrogen storage material. Hydrogen generation is modulated on AB@Co/KA by tuning the amount of water added, which achieves an "on-off" hydrogen release on demand. The Co-modified KA (Co/KA) can be repackaged multiple times for recycling use after the AB is completely hydrolyzed. This work provides a promising approach for controlling the release of hydrogen neither the input of additional energy nor foreign reagents added to the reaction system.

Ultrafast joule-heating-assisted O, N dual-doping of unfunctionalized carbon enhances Ru nanoparticle-catalyzed hydrogen production

The development of a rapid and convenient strategy to regulate the surface microenvironment of inert carbon supports, along with the physicochemical properties of their supported metal nanoparticles, is essential for enhancing catalytic performance. In this study, we describe a straightforward and efficient solid-state microwave method that utilizes a household microwave oven to achieve the co-doping of oxygen and nitrogen in unfunctionalized carbon black (ONCB) using urea as a nitrogen source. The microwave solid-state treatment of commercial carbon black (CB) with urea not only introduces a significant number of heteroatomic functional groups but also substantially increases the pore size and pore volume of the matrix. These enhancements facilitate the uniform growth and dispersion of ultrafine Ru nanoparticles on the surface of ONCB. Consequently, the Ru/ONCB catalyst provides abundant catalytic active sites and mass transfer channels, thereby improving catalytic performance for hydrogen evolution from ammonia borane hydrolysis (ABH). The turnover frequency of Ru/ONCB for ABH reaches 4529 ± 238 min-1 (determined based on Ru dispersion), surpassing a range of analogues and many previously reported carbon-supported Ru catalysts. This study presents a simple and rapid strategy to regulate the surface microenvironment of unfunctionalized carbon support, thereby enhancing the catalytic performance of its supported metal nanoparticles for catalytic hydrogen generation.

Hydrogen Production from Chemical Hydrides via Porous Carbon Particle Composite Catalyst Embedding of Metal Nanoparticles

Porous carbon particles (PCPs) prepared from sucrose via the hydrothermal method and its modified forms with polyethyleneimine (PEI) as PCP-PEI were used as templates as in situ metal nanoparticles as M@PCP and M@PCP-PEI (M:Co, Ni, or Cu), respectively. The prepared M@PCP and M@PCP-PEI composites were used as catalysts in the hydrolysis of NaBH4 and NH3BH3 to produce hydrogen (H2). The amount of Co nanoparticles within the Co@PCP-PEI structure was steadily increased via multiple loading/reducing cycles, e.g., from 29.8 ± 1.1 mg/g at the first loading/reducing cycles to 44.3 ± 4.9 mg/g after the third loading/reducing cycles. The Co@PCP-PEI catalyzed the hydrolysis of NaBH4 within 120 min with 251 ± 1 mL H2 production and a 100% conversion ratio with a 3.8 ± 0.3 mol H2/(mmol cat·min) turn-over frequency (TOF) and a lower activation energy (Ea), 29.3 kJ/mol. In addition, the Co@PCP-PEI-catalyzed hydrolysis of NH3BH3 was completed in 28 min with 181 ± 1 mL H2 production at 100% conversion with a 4.8 ± 0.3 mol H2/(mmol cat·min) TOF value and an Ea value of 32.5 kJ/mol. Moreover, Co@PCP-PEI composite catalysts were afforded 100% activity up to 7 and 5 consecutive uses in NaBH4 and NH3B3 hydrolysis reactions, respectively, with all displaying 100% conversions for both hydrolysis reactions in the 10 successive uses of the catalyst.

Functional Group Regulated Ni/Ti3C2Tx (Tx = F, -OH) Holding Bimolecular Activation Tunnel for Enhanced Ammonia Borane Hydrolysis

Developing economical and efficient catalyst for hydrogen generation from ammonia borane (AB) hydrolysis is still a huge challenge. As an alternative strategy, the functional group regulation of metal nanoparticles (NPs)-based catalysts is believed to be capable of improving the catalytic activity. Herein, a series of Ni/Ti₃C₂T_x-Y (T_x = F, -OH; Y denotes etching time (d)) catalysts are synthesized and show remarkably enhanced catalytic activity on the hydrolysis of AB in contrast to the corresponding without regulating. The optimized Ni/Ti₃C₂T_x-4 with a turnover frequency (TOF) value of 161.0 min^-1 exhibits the highest catalytic activity among the non-noble monometallic-based catalyst. Experimental results and theory calculations demonstrate that the excellent catalytic activity benefits from the bimolecular activation channels formed by Ni NPs and Ti₃C₂T_x-Y. H₂O and AB molecules are activated simultaneously in the bimolecular activation tunnel. Bimolecular activation reduces the activation energy of AB hydrolysis, and hydrogen generation rate is promoted. This article provides a new approach to design effective catalysts and further supports the bimolecular activation model for the hydrolysis of AB.

Pd, Rh and Ru Nanohybrid-catalyzed Tetramethyldisiloxane Hydroysis for H2 Generation, Nitrophenol Reduction and Suzuki-Miyaura Cross-Coupling

The hydrolysis of tetramethyldisiloxane, which is a silicone industrial refuse, provides a convenient method to generates H2 on demand. Herein, the highly selective and efficient 2D graphene-like carbon nanosheets (GCN)...