Beijing Graphene Institute

ABSTRACTThe transfer-free synthesis of inch-scale high-quality graphene on insulators is of paramount importance for emerging electronic and optoelectronic applications. Nevertheless, recent efforts at direct growth via the chemical-vapor-deposition route failed to produce monolayer graphene with a large wafer size (i.e. 6 inches) affording scalable uniformity and batch repeatability. Here, we report a co-field-reconciled synthetic strategy in which the synergistic optimization of thermal and gas-flow fields readily allows the uniform growth of 6-inch monolayer graphene over a sapphire wafer with batch-production capability. The temperature and flow fields are dictated via the concurrent deployment of a graphite gasket and a gas distributor plate, with the effectiveness evidenced by simulation and wafer-level characterization results. Theoretical calculations reveal that our route lowers the methane-decomposition barrier and restrains multilayer nucleation. The thus-prepared graphene exhibits impressive crystal quality, spatial uniformity and electrical performance. Six-inch wafer-scale top-gated graphene field-effect transistor arrays showcase the consistent device characteristics, with a room-temperature mobility average rivaling the state-of-the-art examples. The generality of such a route could be extended to other insulating substrates, including SiC, WC, Si3N4 and SiO2. This work achieves co-field optimization during wafer-level graphene growth over insulators and lays the foundation for advancing the large-scale integration of graphene.

Single-crystal metal foil with high-index facets is an emerging metastable platform for 2D epitaxy, catalysis and electronics. However, its controlled growth has been plagued by the lack of a selective mechanism for driving diverse high-index facets. Here, we report a versatile strategy for the deterministic growth of single-crystal metal foils with diverse high-index facets. By incorporating dislocation energy differences to lift the free energy of strong (100) texture, we selectively activated the abnormal growth of high-index facets with an enhanced driving force, thus enabling the deterministic growth of single-crystal Cu, Ni and Au foils with dozens of high-index facets. Such energized growth leads to a counterintuitive discovery that increasing the driving force reduces the retarding force of ubiquitous thermal groove, which allows one order of magnitude improvement in the growth rate by greatly improving the net driving force. This work provides both thermodynamic and kinetic insights into precise metastability engineering strategies and points to a pathway to expand the library of high-quality single-crystal metal foils with high-index facets for various applications.

High-quality, thick turbostratic graphene offers a promising route to robust, reliable applications while retaining monolayer-like properties. However, its preparation remains challenging, particularly in controlling interlayer configurations and maintaining the quality at high thickness. Herein, an in situ self-heating CVD strategy is developed, realizing simultaneous combined control over twist-tilt interlayer configurations in high-quality, thick graphene. A rapid thermal period stabilizes turbostratic twist stacking by suppressing metastable-to-stable transformation into AB-stacking around the lattice's z-axis, yielding a high layer-number-independent turbostratic ratio (∼92%). Localized self-heating suppresses undesirable gas-phase reactions and amorphous carbon formation, while the electrical "hot-spot" effect facilitates selective defect healing. These suppress tilt configurations around the lattice's x/y axes, resulting in high in-plane interlayer alignment. This strategy achieves low defect density (<1010 cm-2) at rapid growth rate (>100 layers hour-1), rarely accessible via conventional CVD. A self-heating CVD strategy demonstrates excellent scalability and universality, and life cycle assessment and technoeconomic analysis reveal its superior environmental sustainability and cost-effectiveness.

Covalent organic frameworks (COFs) are emerging as promising electrode materials due to their high surface area, tunable porosity, and design flexibility. However, their practical use in energy storage remains limited by their poor stability and electrochemical performance. Here, we report a nitrogen-rich COF, synthesized via an irreversible aromatic nucleophilic substitution between hexaazatriphenylenehexacarbonitrile and 3,3′-diaminobenzidine (HAT-DAB COF), forming stable – C═N– and −C–N– linkages. The framework integrates redox-active phenazine and arylamine units, offering a porous, crystalline, and nitrogen-rich architecture. Structural and morphological analyses confirm its robust and porous nature. As a bifunctional electrode, HAT-DAB COF shows excellent performance in lithium-ion batteries, with a specific capacity of 265 mAh/g, an energy density of ∼607 Wh/kg, and ∼98% Coulombic efficiency over hundreds of cycles. As a supercapacitor, it delivers 110.5 mF/cm2 at 1 mV/s, with ∼95% capacitance retention and 100% Coulombic efficiency over 8000 cycles. Capacitance arises from a synergy of electric double-layer and redox (Faradaic) processes, with the diffusive component retained even at high scan rates, indicating strong pseudocapacitor behavior. This work demonstrates the value of irreversible linkages and rational redox-active design in achieving durable, high-performance COFs for next-generation energy storage applications.

The non-uniform heating phenomenon in microwave-assisted synthesis of carbon materials has persistently posed a core challenge restricting the realization of industrial-scale applications for microwave technology. Here, an innovative microwave reduction strategy based on spatial configuration engineering is proposed, solving the problem of uneven product quality in the scale-up preparation of microwave-assisted reduced graphene oxide (m-rGO). The corona-discharge-free and fully exposed irradiation areas jointly determine the stability of batch reduction and quality of m-rGO. The quality of the m-rGO is significantly improved by preferential optimization of the process parameters, achieving an ID/IG ratio as low as 0.12 and an excellent electrical conductivity of 13486Sm-1, with a yield of ≈70g per batch. Due to its high conductivity, lightweight, graphene-based materials have emerged as promising candidates in absorption-dominated electromagnetic interference (EMI) shielding fields. A microwave-assisted reduced graphene oxide/polyurethane (m-rGO/PU) film is prepared with a thickness of 90µm, exhibiting outstanding EMI SE of up to 40dB in the X-band. This study provides a strategy for mitigating the quality variability associated with microwave heating technology in the scale-up preparation of various advanced carbon materials, facilitating the industrial application of microwave technology.