Hualin Lin

Boron, nitrogen, and phosphorous ternary doped graphene aerogel with hierarchically porous structures as highly efficient electrocatalysts for oxygen reduction reaction

Heteroatom doped porous carbons have shown great potential as metal-free catalysts for electrochemical catalyzed oxygen reduction reaction (ORR). Most previous works have been focused on preparation of single and dual heteroatom doped porous carbons for ORR. In this work, we developed a new two-step method for preparation of boron, nitrogen, and phosphorus (B, N, P) ternary doped hierarchically porous graphene aerogels by using boron phosphate as both B and P precursor and ammonia as N dopant. As-produced ternary-doped graphene aerogels exhibited promising ORR performance (mainly 4e− mechanism, Jk: −4.6 mA cm−2) in alkaline medium in comparison with commercially available precious metal based Pt/C catalyst. As-prepared B/N/P ternary doped hierarchically porous graphene aerogels can serve as the next generation of metal-free catalysts and alternatives to precious metal catalysts for oxygen reduction reaction and fuel cells.

Iron Nanoclusters as Template/Activator for the Synthesis of Nitrogen Doped Porous Carbon and Its CO2 Adsorption Application

We propose a facile synthesis approach for nitrogen doped porous carbon and demonstrate a novel pore-forming method that iron nanoclusters act as a template or activator at different carbonization temperatures based on Fe3+-poly(4-vinyipyridine) (P4VP) coordination. P4VP will completely decompose even in an inert atmosphere, but under the coordination and catalysis of Fe3+, it can be converted to carbon at a very low temperature (400 °C). The aggregation of iron nanoclusters in the carbonization process showed different pore-forming methods at different temperatures. The as-prepared materials possess high specific surface area (up to 1211 m2 g-1), large pore volume (up to 0.96 cm3 g-1), narrow microporosity, and high N content (up to 9.9 wt %). Due to these unique features, the materials show high CO2 uptake capacity and excellent selectivity for CO2/N2 separation. The CO2 uptake capacity of NDPC-2-600 is up to 6.8 and 4.3 mmol g-1 at 0 and 25 °C; the CO2/N2 (0.15/0.85) selectivity at 0 and 25 °C also reaches 18.4 and 15.2, respectively.

Graphene-constructed flower-like porous Co(OH)2 with tunable hierarchical morphologies for supercapacitors

Graphene-constructed flower-like porous Co(OH)2 (GFC) composites were prepared using a one-pot hydrothermal process. The flower-like porous Co(OH)2 with a hierarchical structure was perfectly constructed using graphene sheets. This strategy facilitated the large-scale synthesis of GFC composites. The morphologies of Co(OH)2 ranged from flower petals to large flower-like microspheres. The morphologies were easily controlled by changing the weight ratio of graphene oxide to cobalt salt. The flowers were approximately 5–10 μm in diameter and composed of numerous thin nanoplates. The GFC, as an electrode material for supercapacitors, showed a high specific capacitance of 480 F g−1 at 1 A g−1 and outstanding cycling performance with 93.5% capacitance retained over 1000 cycles. The outstanding electrochemical performance of GFC could be attributed to the large specific surface area of the GFC and synergistic interaction between uniformly dispersed Co(OH)2 and graphene.

Self-assembled graphene coupled hollow-structured γ-Fe2O3 spheres with crystal of transition for enhanced supercapacitors

Self-assembled graphene coupled hollow-structured γ-Fe2O3 spheres (SHFS) were synthesized using a simple hydrothermal method combined with an easy annealing route. In the SHFS crystals, α-Fe2O3 completely transformed into γ-Fe2O3 upon annealing at 500 °C under N2 atmosphere. SHFS-500 was also found to have a high specific surface area of 198 m2 g−1 and to have the characteristics of a good supercapacitor electrode material, an ultrahigh specific capacitance of 332.7 F g−1 at a current density of 2 A g−1, good rate capability, and excellent cycling stability. This enhanced electrochemical performance may be due to the optimal architecture of the hollow-structured γ-Fe2O3 as a result of the extraordinary electrical conductivity of graphene sheets combined with the easy annealing at 500 °C.

Effect of heat treatment on structures and mechanical properties of electroless Ni–P–GO composite coatings

In this work, graphene oxide (GO) was incorporated into a nickel phosphorus (Ni–P) alloy matrix by electroless plating. A series of experiments were carried out to examine the mechanical properties. The surface-heat treatment of Ni–P–GO composite coatings was performed at 200 °C, 400 °C, and 600 °C under vacuum atmosphere, respectively. X-ray diffraction (XRD) results indicated that composite coatings from a mixture of amorphous and crystalline phases transformed into a crystal structure after heat treatment. The microstructures of Ni–P–GO composite coatings were revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The micro-hardness and wear resistance of composite coatings were evaluated using both a micro-hardness tester and wear test apparatus. Additionally, the worn surface of Ni–P–GO composite coatings was analyzed by SEM. The results demonstrated that the heat treatment composite coatings have higher hardness and wear resistance than the composite coatings without heating. Composite coatings perform the best after heat treatment at 400 °C.

Recent Advances in Boron-Containing Conjugated Porous Polymers

Porous polymers, integrating the advantages of porous materials and conventional polymers, have been well developed and exhibited tremendous attention in the fields of material, chemistry and biology. Of these, boron-containing conjugated porous polymers, featuring tunable geometric structures, unique Lewis acid boron centers and very rich physical properties, such as high specific surface, chargeable scaffold, strong photoluminescence and intramolecular charge transfer, have emerged as one of the most promising functional materials for optoelectronics, catalysis and sensing, etc. Furthermore, upon thermal treatment, some of them can be effectively converted to boron-doped porous carbon materials with good electrochemical performance in energy storage and conversion, extensively enlarging the applicable scope of such kinds of polymers. In this review, the synthetic approaches, structure analyses and various applications of the boron-containing conjugated porous polymers reported very recently are summarized.

Effect of ultrasonication on Ni–Mo coatings produced by DC electroformation

The effect of the ultrasound-assisted method on Ni–Mo alloy coatings by direct current (DC) electroformation in a sulphate–citrate bath was investigated with different ultrasound powers. This study focused on the microstructure, molybdenum content, grain size, roughness, micro-hardness and corrosion resistance of the Ni–Mo alloy coatings, which were influenced by the ultrasound parameters. X-ray diffraction results showed that ultrasound modification decreased the grain size of the nanocrystalline alloy coatings. The hardness of the as-plated coatings after ultrasonication was determined by Vickers diamond indentation tests and compared with that of the Ni–Mo coatings in the absence of ultrasound. As a result, the hardness (719 HV) of the former coatings improved significantly. Scanning electron microscopy and atomic force microscopy images showed a smoother coating and a decrease in the surface roughness of the electrodeposited film, as a result of the use of ultrasound. Furthermore, the corrosion resistance behaviour of the coatings was analysed by a Tafel polarisation curve and electrochemical impedance spectroscopic studies in a 3.5 wt% NaCl solution. The ultrasonicated coatings (Ni–Mo) significantly enhanced corrosion resistance (4.1 μA cm−2) compared with those without ultrasound assistance. However, at the maximum ultrasound power (270 W), the molybdenum content, grain size, roughness, microhardness and corrosion resistance of the Ni–Mo alloy coatings all slightly decreased.

N-Doped carbon decorated with molybdenum disulfide with excellent electrochemical performance for lithium-ion batteries

Two-dimensional MoS2 nanoplates within N-doped carbon from polyaniline (PANI) were fabricated by a simple hydrothermal method. During this process, PANI facilitated the absorption of inorganic precursors and provided confined spaces for the growth of MoS3 nanoparticles in the case of the unwanted aggregations. The unique nanostructure and composition of the nanoplates achieved high capacity. When CNFs@NC/MoS2 was used as an anode in lithium-ion batteries, it maintained an ultrahigh capacity of 900.9 mA h g−1 at a current density of 200 mA g−1 for 80 cycles. Even when the current density returned to 100 mA g−1 after cycling at different rates, a capacity of 998 mA h g−1 was still achieved.

Factors affecting the cold flow properties of biodiesel: Fatty acid esters

ABSTRACT Biodiesel is renewable, sustainable, and cost-effective; it possesses good lubricity and high cetane number. Nevertheless, its poor cold flow properties impede the popularization and application of biodiesel. In this study, the cold flow properties of peanut and rapeseed biodiesel and their blends with different fatty acid esters were investigated, including different chain lengths (saturated and unsaturated), different double bond numbers, and different alcohol chains. Results showed that shorter chain length, more double bonds, and branched alcohol chain could effectively improve the biodiesel cold filter plugging point (CFPP). This study also tried to explore the mechanism action of this phenomenon.

MICROSTRUCTURE AND PROPERTIES OF THE Ni–B AND Ni–B–Ce ULTRASONIC-ASSISTED ELECTROLESS COATINGS

We successfully obtained Ni–B and Ni–B–Ce coatings with and without sonication on low-carbon steel (Q235) through electroless plating with the deposition time of 60min. The surface morphology and elemental composition of the coatings were evaluated by scanning electron microscopy (SEM) and inductively coupled plasma (ICP). The 11μm thick sonicated Ni–B–Ce (Son-Ni–B–Ce) coating is uniform with the composition of Ni 87.1%, B 6.2% and Ce 6.6%. X-ray diffraction (XRD) measurements implied a typical broaden peak around 44∘, considered as amorphous structure which was confirmed by selected area electron diffraction pattern (SAED). Atomic force microscopy (AFM) showed a typical circular pit of Ni–B–Ce coating and Son-Ni–B–Ce coating. X-ray photoelectron spectroscopy (XPS) revealed the chemical status of coating components. The mechanical and corrosion resistance properties were determined by Vickers hardness tester, potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS) in 3.5wt. % NaCl solution. As a result, the Son-Ni–B–Ce coating revealed the optimum hardness (956HV), minimum roughness Ra (92.38nm) and excellent corrosion resistance (3.65μAcm−2) among all coatings.