Sufeng Wei

Robust superhydrophobic surface on Al substrate with durability, corrosion resistance and ice-phobicity

Practical application of superhydrophobic surfaces is limited by the fragility of nanoscale asperities. Combining chemical etching and anodization, microscale pits and nanoscale pores, instead of the micro and nano protrusions on traditional superhydrophobic surfaces mimicking Lutos leaves, were fabricated on commercially pure aluminum surfaces. After modified by FDTS, the surfaces were superhydrophobic and self-cleaning. The ultrahigh hardness and electrochemical stability of Al2O3 coating endowed the surface excellent mechanical durability and good corrosion resistance. Because the method is scalable, it may find practical application on body panels of automobiles and aircrafts and so on.

Carbon-Encapsulated Co3O4 Nanoparticles as Anode Materials with Super Lithium Storage Performance

A high-performance anode material for lithium storage was successfully synthesized by glucose as carbon source and cobalt nitrate as Co3O4 precursor with the assistance of sodium chloride surface as a template to reduce the carbon sheet thickness. Ultrafine Co3O4 nanoparticles were homogeneously embedded in ultrathin porous graphitic carbon in this material. The carbon sheets, which have large specific surface area, high electronic conductivity, and outstanding mechanical flexibility, are very effective to keep the stability of Co3O4 nanoparticales which has a large capacity. As a consequence, a very high reversible capacity of up to 1413 mA h g−1 at a current density of 0.1 A g−1 after 100 cycles, a high rate capability (845, 560, 461 and 345 mA h g−1 at 5, 10, 15 and 20 C, respectively, 1 C = 1 A g−1), and a superior cycling performance at an ultrahigh rate (760 mA h g−1 at 5 C after 1000 cycles) are achieved by this lithium-ion-battery anode material.

A unique porous architecture built by ultrathin wrinkled NiCoO2/rGO/NiCoO2 sandwich nanosheets for pseudocapacitance and Li ion storage

Hierarchical porous architectures assembled by ultrathin mesoporous nanosheets are attractive for electrochemical energy storage. Herein, we present a facile and scalable strategy where two ultrathin mesoporous NiCoO2 sheets (∼2 nm) are anchored on both sides of a rGO sheet to form an ultrathin sandwich nanosheet (∼6 nm) using a chemical co-precipitation method. The sandwich nanosheets are randomly wrinkled, thus the framework built up by such sheets is porous and has a high specific surface area. The high quality rGO endows the composite with excellent conductivity. And the firm adhesion between the NiCoO2 sheet and flexible rGO also guarantees the integration of the electrode during electrochemical cycling. The electrochemical tests on the electrode made by such ultrathin sandwich nanosheets validate that the strategy is effective to obtain high performance electrodes for supercapacitors and lithium ion batteries. As an electrode of a lithium ion battery, it shows excellent cycling performance with a specific capacity close to 998 mA h g−1 at a current density of 0.1 A g−1; and as an electrode of a supercapacitor, capacitance retention of 87.6% is achieved over 2000 cycles at a constant current density of 20 A g−1.

A Strategy for Synthesis of Nanosheets Consisting of Alternating Spinel Li4Ti5O12 and Rutile TiO2 Lamellas for High-Rate Anodes of Lithium-Ion Batteries

Ultrathin dual phase nanosheets consisting of alternating spinel Li4Ti5O12 (LTO) and rutile TiO2 (RT) lamellas are synthesized through a facile and scalable hydrothermal method, and the formation mechanism is explored. The thickness of constituent lamellas can be controlled exactly by adjusting the mole ratio of Li:Ti in the original reactants. Alternating insertion of the RT lamellas significantly improves the electrochemical performance of LTO nanosheets, especially at high charge/discharge rates. As anodes in lithium-ion batteries (LIBs), the dual phase nanosheet electrode with the optimized phase ratio can deliver stable discharge capacities of 178.5, 154.9, 148.4, 142.3, 138.2, and 131.4 mA h g-1 at current densities of 1, 10, 20, 30, 40, and 50 C, respectively. Meanwhile, they inherit the excellent cyclic stability of pure spinel LTO and exhibit a capacity retention of 93.1% even after 500 cycles at 50 C. Our results indicate that the alternating nanoscaled lamella structure is a good alternative to facilitate the transfer of both the Li ions and electrons into the spinel LTO, giving rise to an excellent cyclability and fast rate performance. Therefore, the newly prepared carbon-free LTO-RT nanosheets with high safety provide a new opportunity to develop high-power anodes for LIBs.

A novel open architecture built by ultra-fine single-crystal Co2(CO3)(OH)2 nanowires and reduced graphene oxide for asymmetric supercapacitors

Recently, hydroxyl-carbonates have drawn increasing interest in energy storage because of their special layered structure and pseudocapacitive character. In this work, a novel open architecture based on reduced graphene oxide and ultra-fine single-crystal Co2(CO3)(OH)2 nanowires (designed as rGO/Co2(CO3)(OH)2) is synthesized via mutual electrostatic interactions benefiting from their intrinsic opposite charges. Taking advantage of the high conductivity of rGO, the ultra-fine diameter of the nanowires, and the open network of the architecture, the rGO/Co2(CO3)(OH)2 electrode exhibits high specific capacitance (998 F g−1 at 1 A g−1 and 727 F g−1 at 20 A g−1) with excellent rate capability and stability (98.3% capacitance retention after 4000 cycles). An asymmetric supercapacitor fabricated by using it as the positive electrode and activated carbon as the negative electrode has demonstrated high energy/power density (26.7 W h kg−1 at 751 W kg−1 and 13.1 W h kg−1 at 15 362 W kg−1) and outstanding cycle stability (10 000 times with only 5.4% loss).

The Synthesis and Electrochemical Behavior of High-Nitrogen Nickel-Free Austenitic Stainless Steel

A new smelting method to synthesize high-nitrogen nickel-free austenitic stainless steel was suggested. The synthesized steel completely consists of austenite and represents more brilliant anti-corrosion ability both in salt solution and sulfuric acid solution. The brilliant anti-corrosion ability is retained even after severe cold-rolling deformation, which ensures its workability in practice. The potentiodynamic polarization curves, electrochemical impedance spectroscopy, and passivating treatment were used to characterize its corrosion properties and uncover its corrosion mechanism in salt solution. X-ray photoelectron spectroscopy was used to clarify the mechanism of passivation. The results demonstrate that the steel has a more uniform and thicker passive film than traditional stainless steel due to the cooperation of nitrogen and chromium.

Dual Superlyophobic Copper Foam with Good Durability and Recyclability for High Flux, High Efficiency, and Continuous Oil–Water Separation

Traditional oil-water separation materials have to own ultrahigh or ultralow surface energy. Thus, they can only be wetted by one of the two, oil or water. Our experiment here demonstrates that the wettability in oil-water mixtures can be tuned by oil and water initially. Hierarchical voids are built on commercial copper foams with the help of hydrothermally synthesized titanium dioxide nanorods. The foams can be easily wetted by both oil and water. The water prewetted foams are superhydrophilic and superoleophobic under oil-water mixtures, meanwhile the oil prewetted foams are superoleophilic and superhydrophobic. In this paper, many kinds of water-oil mixtures were separated by two foams, prewetted by corresponding oil or water, respectively, combining a straight tee in a high flux, high efficiency, and continuous mode. This research indicates that oil-water mixtures can be separated more eco-friendly and at lower cost.