Synthesis of wafer-scale graphdiyne/graphene heterostructure for scalable neuromorphic computing and artificial visual systems

Graphdiyne (GDY) is emerging as a promising material for various applications owing to its unique structure and fascinating properties. However, the application of GDY in electronics and optoelectronics are still in its infancy, primarily owing to the huge challenge in the synthesis of large-area and uniform GDY film for scalable applications. Here a modified van der Waals epitaxy strategy is proposed to synthesize wafer-scale GDY film with high uniformity and controllable thickness directly on graphene (Gr) surface, providing an ideal platform to construct large-scale GDY/Gr-based optoelectronic synapse array. Essential synaptic behaviors have been realized, and the linear and symmetric conductance-update characteristics facilitate the implementation of neuromorphic computing for image recognition with high accuracy and strong fault tolerance. Logic functions including “NAND” and “NOR” are integrated into the synapse which can be executed in an optical pathway. Moreover, a visible information sensing-memory-processing system is constructed to execute real-time image acquisition, in situ image memorization and distinction tasks, avoiding the time latency and energy consumption caused by data conversion and transmission in conventional visual systems. These results highlight the potential of GDY in applications of neuromorphic computing and artificial visual systems.

     

Non-Volatile Electrolyte-Gated Transistors Based on Graphdiyne/MoS2 with Robust Stability for Low-Power Neuromorphic Computing and Logic-In-Memory

Artificial synapses are the key building blocks for low-power neuromorphic computing that can go beyond the constraints of von Neumann architecture. In comparison with two-terminal memristors and three-terminal transistors with filament-formation and charge-trapping mechanisms, emerging electrolyte-gated transistors (EGTs) have been demonstrated as a promising candidate for neuromorphic applications due to their prominent analog switching performance. Here, a novel graphdiyne (GDY)/MoS₂-based EGT is proposed, where an ion-storage layer (GDY) is adopted to EGTs for the first time. Benefitting from this Li-ion-storage layer, the GDY/MoS₂-based EGT features a robust stability (variation < 1% for over 2000 cycles), an ultralow energy consumption (50 aJ µm⁻²), and long retention characteristics (>10⁴ s). In addition, a quasi-linear conductance update with low noise (1.3%), an ultrahigh G_max/G_min ratio (10³), and an ultralow readout conductance (<10 nS) have been demonstrated by this device, enabling the implementation of the neuromorphic computing with near-ideal accuracies. Moreover, the non-volatile characteristics of the GDY/MoS₂-based EGT enable it to demonstrate logic-in-memory functions, which can execute logic processing and store logic results in a single device. These results highlight the potential of the GDY/MoS₂-based EGT for next-generation low-power electronics beyond von Neumann architecture.     

Bi-Atom Electrocatalyst for Electrochemical Nitrogen Reduction Reactions

The electrochemical nitrogen reduction reaction(NRR)to directly produce NH3 from N2 and H2O under ambient conditions has attracted significant attention due to ...     

Architecting Freestanding Sulfur Cathodes for Superior Room-Temperature Na–S Batteries

Room-temperature sodium–sulfur (RT Na–S) batteries have attracted extensive attention because of their low cost and high specific energy. RT Na–S batteries, however, usually suffer from sluggish reaction kinetics, low reversible capacity, and short lifespans. Herein, it is shown that chain-mail catalysts, consisting of porous nitrogen doped carbon nanofibers (PCNFs) encapsulating Co nanoparticles (Co@PCNFs), can activate sulfur via electron engineering. The chain-mail catalysts Co@PCNFs with a micrograde hierarchical structure as a freestanding sulfur cathode (Co@PCNFs/S) can provide space for high mass loading of sulfur and polysulfides. The electrons can rapidly transfer from chain-mail catalysts to sulfur and polysulfides during discharge–charge processes, therefore boosting its conversion kinetics. As a result, this freestanding Co@PCNFs/S cathode achieves a high sulfur loading of 2.1 ± 0.2 mg cm⁻², delivering a high reversible capacity of 398 mA h g⁻¹ at 0.5 C (1 C = 1675 mA g⁻¹) over 600 cycles and superior rate capability of an average capacity of 240 mA h g⁻¹ at 5 C. Experimental results, combined with density functional theory calculations, demonstrate that the Co@PCNFs/S can efficiently improve the conversion kinetics between the polysulfides and Na₂S via transferring electrons from Co to them, thereby realizing efficient sulfur redox reactions.     

The study of AlN ceramics sintered at superhigh pressure with belt-type press technology

The effects of Y₂O₃ content, sintering time, sintering temperature, sintering pressure on thermal conductivity of AlN ceramics had been studied. X-ray diffraction (XRD), scanning electron microscope (SEM), laser conductometer and laser granularity dimension analysis measurer were respectively used to measure the phases, microstructure, thermal conductivity and particle size distribution of the samples. These studies reveal that the Y₂O₃ is an effective sintering addtive, and the best conditions of sintering are that the pressure is 5.15× 10⁹ Pa, the temperature is 1700∘C and the sintering time is 115 min. Under these conditions, the sintered body has reasonable structure and its thermal conductivity is 200 w/(m⋅k).     

Atomically Dispersed Dual-Site Cathode with a Record High Sulfur Mass Loading for High-Performance Room-Temperature Sodium–Sulfur Batteries

Room-temperature sodium–sulfur (RT-Na/S) batteries possess high potential for grid-scale stationary energy storage due to their low cost and high energy density. However, the issues arising from the low S mass loading and poor cycling stability caused by the shuttle effect of polysulfides seriously limit their operating capacity and cycling capability. Herein, sulfur-doped graphene frameworks supporting atomically dispersed 2H-MoS₂ and Mo₁ (S@MoS₂-Mo₁/SGF) with a record high sulfur mass loading of 80.9 wt.% are synthesized as an integrated dual active sites cathode for RT-Na/S batteries. Impressively, the as-prepared S@MoS₂-Mo₁/SGF display unprecedented cyclic stability with a high initial capacity of 1017 mAh g⁻¹ at 0.1 A g⁻¹ and a low-capacity fading rate of 0.05% per cycle over 1000 cycles. Experimental and computational results including X-ray absorption spectroscopy, in situ synchrotron X-ray diffraction and density-functional theory calculations reveal that atomic-level Mo in this integrated dual-active-site forms a delocalized electron system, which could improve the reactivity of sulfur and reaction reversibility of S and Na, greatly alleviating the shuttle effect. The findings not only provide an effective strategy to fabricate high-performance dual-site cathodes, but also deepen the understanding of their enhancement mechanisms at an atomic level.