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Condensed π-conjugation C-PAN/MS-CN nanotubes were obtained through the facile polyacrylonitrile (PAN)-confined molten salt (MS) thermal condensation of melamine.

Photocatalytic H2 evolution from water splitting using catalysts has proven to be a promising strategy. In photocatalytic H2 evolution, a hydrogen evolution cocatalyst is necessary. The cocatalyst should be inexpensive and efficient. In this work, a hollow Co2(OH)3Cl/cobalt carbide/reduced graphene oxide (RGO) composite was fabricated as a cocatalyst via the one-step thermal treatment at low temperature (300 °C and 350 °C) of CoCl2/graphene oxide (GO). Cobalt carbide was formed based on the strong interaction between GO and Co2+. GO not only provides the carbon source for cobalt carbide, but also acts as a soft template of a hollow structure and promotes the distribution of active species. The obtained sample exhibits a much higher dye-sensitized photocatalytic H2 evolution activity than the catalysts prepared at high temperature (500 °C and 600 °C), which mainly consist of CoO/Co/cobalt carbide/RGO. This enhanced activity is ascribed to the formation of highly dispersed cobalt carbide and Co2(OH)3Cl, the effective electron transfer between them, and the ability of Co2(OH)3Cl to efficiently convey electrons from excited dye molecules. The highest apparent quantum yield of dye-sensitized photocatalytic H2 evolution obtained using our catalyst was 28.3% at 420 nm. The possible mechanism is also discussed.

Recently, advanced membranes based on a 2D material of graphene oxide (GO) for NF have drawn great attention due to their striking, dramatic separation performances which are much higher than traditional membranes. However, stability, which is a precondition for practical applications, has become the bottleneck of the GO membranes for water treatment. Fortunately, the stability of GO membranes in water has received significant attention, and many fruitful efforts have been recently devoted to solving this problem. It is therefore critical to update the broader scientific community on the important advances in this interdisciplinary field. Herein, we review the recent progress made in improving the stability of GO membranes in water. Fundamental issues, including the origin of the instability of GO membranes in water, and influences of the chemical properties of GO itself on the stability of the resultant membranes have been discussed. We also explore the diverse structural design and surface/interface engineering strategies for improving the stability of GO membranes in water, including the introduction of hydrogen bonding or intermolecular interactions via insertion of polyelectrolytes, cross-linking by molecules or ions, or blending of graphene-based materials, as well as improving the interactions between GO selective layers and substrates. The existing challenges and a forward-looking perspective are also outlined, suggesting directions to take in the design of GO and other 2D material-based membranes with outstanding stability and high separation performance for practical applications.

Superhydrophilic membranes have drawn much attention owing to their outstanding anti-fouling performance and ultrahigh permeation flux for wastewater treatment and oil–water separation. Since most widely used polymer membranes have high intrinsic hydrophobicity, a universal approach for superhydrophilic modification is highly required. Yet, how to simply transform highly hydrophobic membranes into superhydrophilic ones is still a challenge. Herein, we develop a one-step and general strategy to achieve the hydrophobic-to-superhydrophilic transformation of commercial membranes on the basis of catechol chemistry, i.e., co-deposition of tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES) in aqueous solution. Owing to the distinct adhesion properties of TA and the reaction between the oxidative product of TA and the hydrolysis product of APTES, hydrophilic and hierarchical layer-colloidal nanospheres can be in situ assembled on various highly hydrophobic membranes including polyvinylidene fluoride (PVDF), polypropylene (PP), polytetrafluoroethylene (PTFE), copper mesh, stainless steel wire, and nylon mesh. The resulting superhydrophilic membrane can realize high-efficiency separation of various oil-in-water emulsions.

Superhydrophilic membranes have attracted significant attention due to their desirable anti-oil-fouling performance for oil/water separation. Although many strategies have been developed to prepare superhydrophilic membranes, few of them are completely green and can be applied for various highly hydrophobic materials. Since most of the widely used membrane materials are usually hydrophobic, an environmentally friendly and mild strategy that can transform various hydrophobic membranes into superhydrophilic ones is highly desired. Herein, for the first time, based on edible ovalbumin (OVA) and tannic acid (TA, a natural and environmentally friendly plant polyphenol), we have developed a novel, mild and completely green strategy to realize the superhydrophilic transformation of various hydrophobic membranes including polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), copper mesh, and fabric. The water-soluble OVA can be adsorbed on hydrophobic materials via hydrophobic interaction, and the adsorbed OVA further acts as a pre-coating to facilitate the subsequent introduction of abundant TA molecules. On the other hand, TA can not only provide abundant hydrophilic groups, but can also induce the degeneration of the adsorbed OVA layer, realizing the formation and firm immobilization of hybrid coatings decorated with abundant nanonodes. The resulting membranes exhibit superhydrophilicity, underwater superoleophobicity (all underwater oil contact angles are above 155° and oil roll-off angles are below 5°) and favorable anti-oil-fouling performance and thus, high-efficiency oil/water separation can be realized. In addition, the membranes can maintain their superhydrophilicity and underwater superoleophobicity after continuous rinsing treatment with salt and surfactant solutions for 6 h or ultrasonic treatment for 5 min, demonstrating their favourable stability.

To resolve the energy crisis and environment pollution, it is urgent to exploit highly efficient and inexpensive catalysts for the hydrogen evolution reaction (HER). Herein, we report a hollow Ni/RGO (reduced graphene oxide) composite (HNG) as an efficient HER catalyst, which was fabricated through a facile template-free method using graphene oxide (GO) sol as the raw material. The explosively released gases from GO under thermal treatment restrained the growth of Ni species towards the formed gas bubbles, resulting in the formation of hollow Ni nanoparticles (NPs). The hollow structure contributes to the diffusion of the reactant H2O to the active sites for HER. The electrocatalytic HER activity of HNG increases with the amount of hollow Ni NPs in the range from 3 to 12 wt% Ni loading. However, the dye-sensitized photocatalytic H2 evolution activity reaches the maximum at 9.0 wt%, due to the interaction between the dye and RGO. Under optimal conditions, the highest apparent quantum yield (AQY) for the hydrogen evolution at 470 nm reaches 47.7%. This study paves the way for the synthesis of various hollow metal–RGO materials.

Single ZnIn2S4 or Zn-In-S composites were synthesized by a simple low temperature (80 °C) method assisted by the presence of NaCl. The products were characterized by XRD, SEM, TEM, TG/DTA, ICP-AES, BET and UV-Vis absorption spectrometry. The decomposition of thioacetamide (TAA) at low temperature was investigated by UV-Vis absorption spectrometry. The decomposition rate of TAA and NaCl concentration influenced the composition, structure, morphology and grain size of the products. The obtained samples are marigold-like microspheres consisting of nanosheets. Loading 0.10 wt% Pt on the samples by in situ photoreduction, allowed the photocatalytic activity of the prepared samples to be evaluated by hydrogen evolution from aqueous solution containing triethanolamine as the electron donor under visible light (λ ≥ 420 nm) irradiation. The activity of the sample obtained in the presence of 0.50 mol L−1 NaCl is ca. 5 times higher than samples without NaCl. Thus, a photocatalyst with layered structure is beneficial for photoactivity. A possible mechanism is discussed.

Cubic nanocrystalline CdS was hydrothermally transformed into hexagonal CdS in the presence of Na3PO4 at 180 °C for 12 h. The as-prepared CdS samples were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), BET, electrophoretic analysis, photoluminescence (PL) spectra and UV-Vis absorption spectra techniques. Effects of phosphate concentration, hydrothermal time and Pt loading content were investigated. Their photoactivity was evaluated by hydrogen evolution from aqueous solution containing formic acid as a hole scavenger under visible light (λ ≥ 420 nm) irradiation. Phosphate markedly promotes the phase transformation of CdS from cubic to hexagonal. With 0.050 mol L−1 PO43−, the formed hexagonal phase content reaches a maximum (82%). The as-prepared CdS with a high percentage of hexagonal phase displays excellent activity for photocatalytic hydrogen evolution. Pt is highly dispersed on CdS so that the Pt content for the effective hydrogen evolution is very low. The CdS loaded with 0.025 wt% Pt shows the maximum activity for the hydrogen evolution. The apparent quantum yield at 420 nm amounts to 21.4%. This work highlights a facile and low-cost method for the preparation of a highly-efficient CdS photocatalyst. The possible mechanisms were discussed.

The 12-layer hexagonal perovskite Ba4YMn3O11.5 (Rm, referred to as 12R) was transformed to a 6-layer mixed valent Mn3+/4+ hexagonal perovskite Ba4YMn3O10.7 (P63/mmc, referred to as 6H) via a partial-reduction in a N2 flow. This phase transformation between the 12R and 6H phases is redox-reversible. In contrast with the 12R-type Ba4YMn3O11.5 structure containing c-BaO2.75 and h-BaO3 layers with a (cchh)3 stacking, the 6H-type Ba4YMn3O10.7 structure consists of the cubic (c) BaO2.87 and hexagonal (h) BaO2.33 layers with a (cch)2 stacking, showing a preference of oxygen vacancy distribution in the hexagonal layers over the cubic layers. The h-BaO2.33 layer in the 6H-type Ba4YMn3O10.7 transforms two-thirds of face-sharing octahedral Mn2O9 dimers into edge-sharing pyramidal Mn2O8 units, sharing corners with Y octahedra/pyramids. Impedance measurements suggested that the 6H-type material is insulating with a bulk electrical resistivity of ∼107 Ω cm at 303 K, significantly higher than that for the 12R-type Ba4YMn3O11.5 by ∼4 orders of magnitude.

Zn-In-S composites were synthesized by a NaCl-assisted hydrothermal method and characterized by an X-ray diffractometer (XRD), Scanning electron microscope (SEM), Energy dispersive spectrometer (EDS), BET, UV-Vis absorption spectrometer and inductively coupled plasma-atomic emission spectrometer (ICP). The products obtained by the hydrothermal method are a single ZnIn2S4 or a composite of ZnIn2S4, ZnmIn2Sm+3, ZnS and In2S3, depending on the NaCl concentration. The samples are consisted of microspheres and sheet-like grains with a marigold-like superstructure. The grain size of the products increases and the specific surface area decreases with an increase of the NaCl concentration. Their photoactivities were evaluated by hydrogen evolution from an aqueous triethanolamine solution under visible light (λ ≥ 420 nm) irradiation. 0.50 wt% Pt was deposited on the samples for the photocatalytic hydrogen evolution by in situ photoreduction. The sample obtained in the presence of 0.20 mol L−1 NaCl exhibits the highest activity for hydrogen evolution, ca. 4 times as high as that of the sample prepared without NaCl. A possible mechanism was discussed.