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Ru-based bimetallic alloy nanoparticles (NPs) have been demonstrated as efficiently catalytic sites for hydrogen evolution from ammonia borane (AB) hydrolysis, but their facile syntheses with ultrafine sizes and superior activity are still challengeable. Herein, we report the in situ fabrication of ultrafine RuCo alloy NPs and concomitant AB hydrolysis using graphite carbon nitride (g-C3N4) as a supporting matrix. Notably, the catalytic activity of Ru1Co1−x/g-C3N4 is mostly dependent on the composition of Ru and Co metals and an optimal synergistic catalysis for AB hydrolysis is achieved using Ru0.1Co0.9/g-C3N4 as a catalyst. An extraordinary turnover frequency of 1260 min−1 is obtained at 25 °C without the use of any basic additives, which surpasses most of the noble metal heterogeneous catalysts. The efficient catalytic activity of Ru0.1Co0.9/g-C3N4 is attributed to the synergistic alloying effect between Ru and Co NPs, and the abundant nitrogen-containing functional groups on g-C3N4 serve as the anchoring sites for ultrafine and uniformly distributed RuCo alloy NPs. The high catalytic activity endows Ru0.1Co0.9/g-C3N4 with desirable potential in hydrogen generation from the hydrolysis of chemical storage materials.

Hydrogen production from ammonia borane (AB) hydrolysis catalyzed by efficient heterogenous catalysts is regarded as a compelling strategy to meet the increasing requirement for clean energy. Palladium (Pd) nanoparticle (NP)-based catalysts have stimulated intensive attention for AB hydrolysis, while their catalytic performances still need to be significantly improved. By exploiting sodium hydroxide and three-dimensional (3D) architecture of interconnected porous carbon nanosheets (IPCNs) as a NP carrier, a simple yet efficient strategy is developed to synthesize uniformly distributed ligand-free Pd NPs (2.17 nm in diameter) for hydrogen generation from AB hydrolysis. The particle size and spatial dispersion control of Pd NPs on the IPCNs surface supply an abundance of surface-active sites and thus remarkable improve the catalytic performance for AB hydrolysis to hydrogen evolution. Specifically, the achieved Pd/IPCNs reveals an extremely high catalytic activity with a turnover frequency (TOF) of 122.8 min−1 toward AB hydrolysis, which is higher than that of many reported Pd-based catalysts. This simple, straightforward and efficient method is of significant importance for preparing metal NP catalysts with high catalytic activities for catalytic applications.

Compared with the traditional gear reduction mechanism of the asynchronous motor, the permanent magnet synchronous motor (PMSM) direct drive technology has obvious advantages and has attracted increasing attention. We analyzed the advantages of the PMSM direct drive technology and put forward the hollow shaft structure of the coupling to reduce the impact force of the wheel and rail, additional noise, vibration, and loss. We deeply studied the topology and mathematical model of the PMSM. To keep the maximum running speed unchanged, it is necessary to conduct a flux weakening control above the rated speed to increase the speed regulation range of the PMSM. To prevent frequent switching jitter at the transition point and smooth the transition between different weak magnetic fields, we designed a new flux-weakening controller to control the current. Simulation results have been presented to verify the proposed approach efficiency. Taking the PMSM system train on Suzhou Metro line 3 as an example, the on-site energy consumption test was carried out. The energy consumption of the PMSM direct drive and asynchronous motor gear mechanism was compared. The energy consumption of the PMSM direct drive is increased by 16.50%. The flexible plate coupling can alleviate the adverse effects of vibration and improve the reliability of train operation. Finally, we put forward the technical difficulties and challenges of the PMSM direct drive technology. We need to optimize the mass distribution of the direct drive bogie to improve the dynamic performance of the bogie, the heat dissipation conditions, and the accurate control of the PMSM. It will have reference value for the development of the PMSM direct drive in the future.

Supported metal nanoparticles (MNPs) have shown great promise in catalytic hydrogen evolutions because of the highly efficient utilization of metal atoms, while the low binding strength between MNPs and supports results in the agglomeration of MNPs into larger particles, considerably decreasing the catalytic efficiency. Herein, we smartly develop a universal, green, and sustainable low-temperature oxidative thermal redispersion strategy to fabricate metal oxide precursors and subsequently well dispersing and stabilizing MNPs (M = Rh, Ru, Ir) over oxygenated carbons (Mesoporous carbon, Ketjen black, and Vulcan carbon), which can be utilized as efficient catalysts for hydrogen production from ammonia borane (AB) hydrolysis and hydrogen evolution reaction (HER). Such flexible modulation strategy enables the formation of oxidized metal species on oxygenated carbons, which is the key to synthesize ultrasmall MNPs against sintering and agglomeration during the reduction process. Attributing to the innately structural/componential/surficial superiorities, the optimal Rh/C-300A-350H exhibits the highest catalytic activity toward hydrogen evolution from AB hydrolysis and HER with turnover frequencies of 3308/5040 min−1 in aqueous/basic solutions and an overpotential of 29 mV at 10 mA cm−2 in 1.0 M KOH, respectively. With the similar activation mechanism for dissociation of O–H bond in H2O, the highly dispersed Rh NPs with ultrafine sizes and electronic metal-support interaction are responsible for the excellent catalytic activity toward the hydrogen evolution reactions. This study presents an extremely facile and sustainable modulation strategy for increasing the adhesion of MNP catalysts on oxygenated carbons for catalytic applications.

Supported metal nanoclusters (NCs) have become highly attractive in catalytic applications because of their maximum atom utilization with superior catalytic property. The main challenge in fabricating metal NC catalysts is their low binding strength with carriers, which induces transformation of metal NCs to large nanoparticles. In this study, a facile, effective, and eco-friendly synthetic strategy for O/N-doped hollow carbon (ONC) is developed through direct steaming commercial Vulcan carbon in nitric acid vapour. The strong binding strength between abundant O/N functional groups of hollow structure of carbon matrix and Ru precursors enables the production of highly dispersed Ru NCs on ONC (Ru/ONC). The achieved Ru/ONC with highly distributed Ru NCs (1.69 nm in diameter) exhibits a significant activity improvement for catalytic AB dehydrogenation compared with Ru/C without modification. High turnover frequencies of 556 and 1837 min−1 (with NaOH) are achieved under the optimal conditions, surpassing most of previous developed Ru catalysts. Homogenously distributed Ru NCs with rich surface-active sites and the O/N functional groups of hollow structured carbon induced fast mass transfer are responsible for the superior activity. The facile strategy shows great application prospects for the preparation of efficient supported metal catalysts by modifying the structure and surface properties of carbon carriers.