Delamination of layer materials into two-dimensional single-atom sheets has induced exceptional physical properties, including large surface area, ultrahigh intrinsic carrier mobility, pronounced changes in the energy band structure, and other properties. Here, atomically thin mesoporous nanomesh of graphitic carbon nitride (g-C3N4) is fabricated by solvothermal exfoliation of mesoporous g-C3N4 bulk made from thermal polymerization of freeze-drying assembled Dicyandiamide nanostructure precursor. With the unique structural advantages for aligned energy levels, electron transfer, light harvesting, and the richly available reaction sites, the as-prepared monolayer of mesoporous g-C3N4 nanomesh exhibits a superior photocatalytic hydrogen evolution rate of 8510 μmol h(-1) g(-1) under λ > 420 nm and an apparent quantum efficiency of 5.1% at 420 nm, the highest of all the metal-free g-C3N4 nanosheets photocatalysts.

Zero-dimensional MoS2 quantum dots (QDs) possess distinct physical and chemical properties, which have garnered them considerable attention and facilitates their use in a broad range of applications. In this study, we prepared monolayer MoS2 QDs using temporally shaped femtosecond laser ablation of bulk MoS2 targets in water. The morphology, crystal structures, chemical, and optical properties of the MoS2 QDs were characterized by transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, UV–vis absorption spectra, and photoluminescence spectra. The analysis results show that highly pure, uniform, and monolayer MoS2 QDs can be successfully prepared. Moreover, by temporally shaping a conventional single pulse into a two-subpulse train, the production rate of MoS2 nanomaterials (including nanosheets, nanoparticles, and QDs) and the ratio of small size MoS2 QDs can be substantially improved. The underlying mechanism is a combination of multilevel photoexfoliation of monolayer MoS2 and water photoionization–enhanced light absorption. The as-prepared MoS2 QDs exhibit excellent electrocatalytic activity for hydrogen evolution reactions because of the abundant active edge sites, high specific surface area, and excellent electrical conductivity. Thus, this study provides a simple and green alternative strategy for the preparation of monolayer QDs of transition metal dichalcogenides or other layered materials.

Large-scale integrated graphene oxide power generator arrays on paper have been fabricated by direct screen printing and provide a high enough electrical output to power electronic devices.

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The use of abundant solar energy for regeneration and desalination of water is a promising strategy to address the challenge of a global shortage of clean water. Progress has been made to develop photothermal materials to improve the solar steam generation performance. However, the mass production rate of water is still low. Herein, by a rational combination of photo-electro-thermal effect on an all-graphene hybrid architecture, solar energy can not only be absorbed fully and transferred into heat, but also converted into electric power to further heat up the graphene skeleton frame for a much enhanced generation of water vapor. As a result, the unique graphene evaporator reaches a record high water production rate of 2.01-2.61 kg m h under solar illumination of 1 kW m even without system optimization. Several square meters of the graphene evaporators will provide a daily water supply that is enough for tens of people. The combination of photo-electro-thermal effect on graphene materials offers a new strategy to build a fast and scalable solar steam generation system, which makes an important step towards a solution for the scarcity of clean water.

To solve the aforementioned problems, emerging graphene agglomerates with crumpled morphologies obtained by the stacking of graphene sheets seem to be promising for increasing the packing density and energy density in energystorage devices. [ 23,24 ] Unfortunately, they usually exhibit a rather low packing density, and consequently a relatively low volumetric capacity. Additionally, the closely stacked graphene agglomerate electrodes generally decrease the ion-accessible surface area and electrolyte ion diffusion, which inevitably compromises its lithium storage capacity. Thus, both a high density and porous structure should be taken into consideration when seeking a strategy for the synthesis of novel carbon-based LIB anodes.Recently, holey graphene, as a new class of graphene derivatives, has attracted extensive attention because of its high intrinsic electrical conductivity, open ion channels, and edge activity useful for applications in electrochemistry-related fi elds. [ 8,25 ] In our previous study, we have demonstrated a lightweight porous graphene foam as advanced electrode material for electrochemical processes (e.g., hydrogen evolution reaction, oxygen reduction reaction, ethanol oxidation reaction, and as electrochemical capacitor). [26][27][28][29][30] Herein, we report a N-doped holey-graphene monolith (NHGM) with a dense microstructure and high density of 1.1 g cm −3 . The holey structure in the individual graphene sheets could not only provide effi cient diffusion channels for Li ions and a highly conductive pathway for electrons, but also provided more edges on the sheet to enhance Li intercalation. [ 31,32 ] NHGM was obtained by conjugating N-containing holey-graphene sheets into a 3D hydrogel, followed by evaporation of the trapped water under vacuum at room temperature and an annealing treatment under Ar atmosphere. This highly compact but porous architecture with heteroatom doping is favorable for ion diffusion, Li ion storage, and maximizing the LIB properties; the NHGM had a volumetric capacity of 1052 mAh cm −3 , which is nearly three times that of commercial graphite anodes (370 mAh cm −3 ), [ 33 ] and exhibited competitive characteristics over the existing Si-based and carbon/sulfur hybrid electrode materials (see Table S1 in the Supporting Information). This makes our graphene-based electrode material an important step toward practical applications.To prepare the N-doped, high-density, holey-graphene monolith (NHGM), we fi rst produced the N-containing holeygraphene hydrogel (NHGH) by a one-pot hydrothermal process with simultaneous etching of nanopores in the graphene sheets and co-assembly of graphene and pyrrole to form a 3D hydrogel. During the hydrothermal process, a controlled amount of H 2 O 2

Photocatalytic water splitting for hydrogen evolution by utilizing solar energy has a great significance for high-density solar energy storage and environmental sustainability. Here, a defect-rich amorphous carbon nitride (DACN) photocatalyst has been synthesized by simply direct calcination of the rationally size-reduced urea crystals. The introduction of nitrogen vacancies combined with disordered structure cause a broad visible-light-reponsive range, countless lateral edge/exposed surface bonding sites, and quenched radiative recombination, suggesting that this DACN enhances photocatalytic activity for hydrogen production. A record high hydrogen evolution rate of 37,680 μmol h g under visible-light irradiation and an extraordinary apparent quantum efficiency of 34.4% at 400 nm were achieved, higher than most of the existing graphitic carbon nitride-based photocatalysts.

Electrochemical oxygen reduction to hydrogen peroxide is now being studied as a promising renewable and localized alternative for the traditional complex anthraquinone process. Catalysts for this two-electron reduction pathway with high selectivity are required to achieve industrialization. Here, we disclose an inexpensive metal-free catalyst that is synthesized from commercial carbon black (CB) with a one-step plasma method for the affordable electrochemical generation of hydrogen peroxide in 100% Faradaic efficiency. This catalyst shows a high onset potential (0.1 mA cm −2 at 0.80 V vs reversible hydrogen electrode (RHE)) and the highest mass activity (300 A g −1 at 0.60 V vs reversible hydrogen electrode) among state-of-the-art catalysts. The performance could be maintained after the removal of oxygen-containing groups. Microscopic and spectroscopic characterizations as well as density functional theory (DFT) calculations indicate that the performance comes from the defective structure after plasma treatment.