ZIF-67 derived Co@NC/g-C3N4 as a photocatalyst for enhanced water splitting H2 evolution.

Graphitic carbon nitride (g-C3N4), as the one of the most promising photocatalysts, usually relies on noble metal co-catalysts in the photocatalytic water splitting H2 evolution process, which greatly increases the use cost. Here, a zeolite imidazole framework (ZIF-67) derived Co@NC/g-C3N4 composite was constructed through facile thermal condensation of ZIF-67 and melamine. The obtained Co@NC/g-C3N4 composites can drive water splitting H2 evolution without any noble metal co-catalyst under simulated sunlight. The optimal sample exhibits the highest H2 evolution rate of 161 µmol g-1·h-1, which is 6 times of pure g-C3N4. The N doped carbon in carbonized ZIF-67 can not only quickly capture separated electrons from g-C3N4, but also serve as the co-catalyst. The well dispersed cobalt intermediate on carbonized ZIF-67 also play a role in promoting electron conversion. The formation of junction between carbonized ZIF-67 and g-C3N4 could promote quick charge carrier separation and transfer. This work provides a new idea for photocatalytic H2 evolution without noble metal co-catalysis.

Remarkable adsorption performance of MOF-199 derived porous carbons for benzene vapor.

Volatile organic compounds (VOCs) are perceived as serious pollutants due to their great threat to both environment and human health. Recovery and removal of VOCs is of great significance. Herein, novel MOF-199 derived porous carbon materials (MC-T-n) were prepared by using MOF-199 as precursor, glucose as additional carbon source and KOH as activator, and then characterized. Adsorption performance of MC-T-n materials for benzene vapor was investigated. Isotherms of MC-T-n samples towards benzene and water vapor were measured. The adsorption selectivities of benzene/water were estimated by DIH (difference of the isosteric heats) equation. Results indicated that BET surface area and pore volume of MC-T-n materials reached separately 2320 m2/g and 1.05 m3/g. Benzene adsorption capacity of MC-T-n materials reached as high as 12.8 mmol/g at 25 °C, outperforming MOF-199 and some conventional adsorbents. Moreover, MC-T-n materials presented type-V isotherms of water vapor, suggesting their excellent water resistance. The isosteric heats of benzene adsorption on MC-500-6 were much greater than that of water adsorption, leading to a preferential adsorption for C6H6 over H2O. The adsorption selectivity of C6H6/H2O on MC-500-6 reached up to 16.3 superior to some previously reported MOFs. Therefore, MC-500-6 was a promising candidate for VOC adsorption and seperation. This study provides a strong foundation for MOF derived porous carbons as adsorbents for VOC removal.

Core-shell Pd-P@Pt-Ni nanoparticles with enhanced activity and durability as anode electrocatalyst for methanol oxidation reaction.

Pd-P@Pt-Ni core-shell nanoparticles, which consisted of a Pd-P alloy as a core and Pt-Ni thin layer as a shell, were explored as electrocatalysts for methanol oxidation reaction. The crystallographic information and the electronic properties were fully investigated by X-ray diffraction and X-ray photoelectron spectroscopy. In the methanol electrooxidation reaction, the particles showed high catalytic activity and strong resistance to the poisoning carbonaceous species in comparison with those of commercial Pt/C and the as-prepared Pt/C catalysts. The excellent durability was demonstrated by electrochemically active surface area loss and chronoamperometric measurements. These results would be due to the enhanced catalytic properties of Pt by the double synergistic effects from the core part and the nickel species in the shell part.

Amorphous FeNiNbPC nanoprous structure for efficient and stable electrochemical oxygen evolution.

The oxygen evolution reaction (OER) is a crucial process for water splitting. Reducing overpotential is a great challenge because of four electrons transfer and slow kinetics compared to the hydrogen evolution reaction (HER). Highly efficient and stable OER catalyst with low-cost is important for industrial hydrogen production by water splitting. Here we report a simple approach to synthesize free-standing amorphous FexNi77-xNb3P13C7 with the nanoporous structure through electrochemical dealloying. The np-Fe50Ni27Nb3P13C7 exhibits remarkable OER catalytic activity with a low overpotential of 248 mV to achieve the current density of 10 mA cm-2 in 6 M KOH solution. Also, the np-Fe50Ni27Nb3P13C7 exhibits good long-term stability. The improved OER property is due to bimetallic synergy, decreased resistance of charge transfer, nanoporous structure, amorphous nature, and the generation of NiOOH during the OER process. The free-standing amorphous catalysts with nanoporous structure via electrodealloying method provide a promising approach to boost the performance of non-noble metal OER catalysts for the applications.

Self-supported Ni3Se2@NiFe layered double hydroxide bifunctional electrocatalyst for overall water splitting.

Low-cost, highly active and earth-abundant bifunctional electrocatalyst is very important for the large-scale hydrogen production by water splitting. In the present work, we report a novel two-step method to fabricate three-dimensional (3D) porous catalyst for water splitting. The Ni3Se2 nanowires are in-situ formed on Ni foam (NF) by simple hydrothermal method, subsequently NiFe layered double hydroxid (NiFe-LDH) nanosheets vertically grow on the nanowires to form core-shell structure. The as-formed Ni3Se2@NiFe-LDH/NF catalyst shows 3D porous structure, which can provide large specific surface area and effective substance transfers. The tight bonding between Ni3Se2 nanowires and NiFe-LDH nanosheets ensures good electron transfer. The Ni3Se2@NiFe-LDH/NF catalyst exhibits outstanding electrocatalytic property for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline medium. The overpotentianls for HER and OER at the current density of 10 mA cm-2 in 1 M KOH are 68 mV and 222 mV, respectively. For overall water splitting, a small cell voltage of 1.55 V can achieve a current density of 10 mA cm-2 in 1 M KOH. This work provides a guidance for the rational design and development of heterostructure electrocatalysts for overall water splitting.

Ionic Conductive Organohydrogel With Ultrastretchability, Self-Healable and Freezing-Tolerant Properties for Wearable Strain Sensor.

Currently, stretchable hydrogel has attracted great attention in the field of wearable flexible sensors. However, fabricating flexible hydrogel sensor simultaneously with superstretchability, high mechanical strength, remarkable self-healing ability, excellent anti-freezing and sensing features via a facile method remains a huge challenge. Herein, a fully physically linked poly(hydroxyethyl acrylamide)-gelatin-glycerol-lithium chloride (PHEAA-GE-Gl-LiCl) double network organohydrogel is prepared via a simple one-pot heating-cooling-photopolymerization method. The prepared PHEAA-GE-Gl-LiCl organohydrogel exhibits favorable stretchability (970%) and remarkable self-healing property. Meanwhile, due to the presence of glycerol and LiCl, the PHEAA-GE-Gl-LiCl organohydrogel possesses outstanding anti-freezing capability, it can maintain excellent stretchability (608%) and conductivity (0.102 S/m) even at -40°C. In addition, the PHEAA-GE-Gl-LiCl organohydrogel-based strain sensor is capable of repeatedly and stably detecting and monitoring both large-scale human motions and subtle physiological signals in a wide temperature range (from -40°C to 25°C). More importantly, the PHEAA-GE-Gl-LiCl organohydrogel-based sensor displays excellent strain sensitivity (GF = 13.16 at 500% strain), fast response time (300 ms), and outstanding repeatability. Based on these super characteristics, it is envisioned that PHEAA-GE-Gl-LiCl organohydrogel holds promising potentials as wearable strain sensor.

Nanoporous Nickel-Molybdenum Oxide with an Oxygen Vacancy for Electrocatalytic Nitrogen Fixation under Ambient Conditions.

The electrochemical nitrogen reduction reaction (NRR) is regarded as a sustainable method for N2 fixation. N2 adsorption and N≡N cleavage are the main challenges for the NRR. Herein, we propose a potential approach to enhance N2 activation via introducing oxygen vacancies (OVs) into nanoporous NiO/MoO3. Nanoporous NiO/MoO3 with OVs (np-OVs-NiO/MoO3) is prepared by a two-step process of dealloying and solid-state reaction. np-OVs-NiO/MoO3 exhibits a high NH3 yield of 35.4 µg h-1 mgcat-1 and a Faradaic efficiency (FE) of 10.3% in 0.1 M PBS solution. The introduction of OVs enhances the conductivity, N2 adsorption, and catalytic performance of np-NiO/MoO3. The dual-metal sites with OVs have a unique electronic structure in favor of the "π back-donation" behavior, which decreases the energy barrier of protonation steps and improves the whole NRR process. This approach provides new insight into the design of composite transition metal oxides with OVs for the NRR catalyst under ambient conditions.

In situ synthesis of a novel Mn3O4/g-C3N4 p-n heterostructure photocatalyst for water splitting.

Designing high-efficiency photocatalyst for photocatalytic water splitting is a considerable challenge. Herein, a new Mn3O4/g-C3N4 p-n heterostructure photocatalyst is prepared by an in-situ growth method. The introduction of Mn3O4 can enhance light absorption ability of g-C3N4. The Mn3O4/g-C3N4 photocatalyst exhibits outstanding photocatalytic activity for hydrogen evolution reaction (HER) efficiency of ~2700 µmol g-1h-1 at λ > 420 nm. For the separate reactions of H2 evolution and O2 evolution under simulated sunlight, the efficiencies of Mn3O4/g-C3N4 heterostructure photocatalyst are 3300 µmol g-1h-1 and 654 µmol g-1h-1, respectively. The p-n junction is also capable of catalyzing the overall water splitting reaction to generate H2 and O2 products in a stoichiometric molar ratio of 2:1. The formation of electric field in p-n Mn3O4/g-C3N4 junction promotes electron transfer and improves photocatalytic performance.

Facile synthesis of Ag nanoparticles-loaded chitosan antibacterial nanocomposite and its application in polypropylene.

The development of environmental-friendly antibacterial agents with high efficiency and low cost has become the focus of attention. In this work, the Ag nanoparticles doped into chitosan (Ag NPs-CS) were synthesized by a green and facile method, and the samples were characterized by UV-Vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The antibacterial tests implied that Ag NPs-CS obtained from glucose (G-Ag NPs-CS) exhibited the excellent antimicrobial activities against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) microbes. Besides, the utilization of antibacterial agents in polymeric materials plays an significant role in healthy living. The aim is to impart the antibacterial properties and maintain/improve the mechanical properties. Therefore, the G-Ag NPs-CS with 5 wt% Ag was chosen as the optimal additive to endow polypropylene with antimicrobial activity via a simple melt blending method. The results demonstrated that the suppression of bacteria proliferation was enhanced with increasing the amount of antibacterial agent, and the microorganisms were almost killed when the content reached to 8 wt%. Meanwhile, the considerable improvement in elastic modulus and impact strength along with a slight decrease of elongation at break provided the evidence that Ag NPs-CS/PP nanocomposites were the promising candidate for practical applications.