Kening Sun

Facile Synthesis of Anatase TiO2 Quantum‐Dot/Graphene‐Nanosheet Composites with Enhanced Electrochemical Performance for Lithium‐Ion Batteries

A facile method to synthesize well-dispersed TiO2 quantum dots on graphene nanosheets (TiO2 -QDs/GNs) in a water-in-oil (W/O) emulsion system is reported. The TiO2 /graphene composites display high performance as an anode material for lithium-ion batteries (LIBs), such as having high reversible lithium storage capacity, high Coulombic efficiency, excellent cycling stability, and high rate capability. The excellent electrochemical performance and special structure of the composites thus offer a way to prepare novel graphene-based electrode materials for high-energy-density and high-power LIBs.

Graphene-Co3O4 nanocomposite as electrocatalyst with high performance for oxygen evolution reaction

Graphene-Co3O4 composite with a unique sandwich-architecture was successfully synthesized and applied as an efficient electrocatalyst for oxygen evolution reaction. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses confirmed that Co3O4 nanocrystals were homogeneously distributed on both sides of graphene nanosheets. The obtained composite shows enhanced catalytic activities in both alkaline and neutral electrolytes. The onset potential towards the oxygen evolution reaction is 0.406 V (vs. Ag/AgCl) in 1 M KOH solution, and 0.858 V (vs. Ag/AgCl) in neutral phosphate buffer solution (PBS), respectively. The current density of 10 mA/cm2 has been achieved at the overpotential of 313 mV in 1 M KOH and 498 mV in PBS. The graphene-Co3O4 composite also exhibited an excellent stability in both alkaline and neutral electrolytes. In particular, no obvious current density decay was observed after 10 hours testing in alkaline solution and the morphology of the material was well maintained, which could be ascribed to the synergistic effect of combining Co3O4 and graphene.

Synthesis of MoS2 and MoO2 for their applications in H2 generation and lithium ion batteries: a review

Abstract Scientists increasingly witness the applications of MoS2 and MoO2 in the field of energy conversion and energy storage. On the one hand, MoS2 and MoO2 have been widely utilized as promising catalysts for electrocatalytic or photocatalytic hydrogen evolution in aqueous solution. On the other hand, MoS2 and MoO2 have also been verified as efficient electrode material for lithium ion batteries. In this review, the synthesis, structure and properties of MoS2 and MoO2 are briefly summarized according to their applications for H2 generation and lithium ion batteries. Firstly, we overview the recent advancements in the morphology control of MoS2 and MoO2 and their applications as electrocatalysts for hydrogen evolution reactions. Secondly, we focus on the photo-induced water splitting for H2 generation, in which MoS2 acts as an important co-catalyst when combined with other semiconductor catalysts. The newly reported research results of the significant functions of MoS2 nanocomposites in photo-induced water splitting are presented. Thirdly, we introduce the advantages of MoS2 and MoO2 for their enhanced cyclic performance and high capacity as electrode materials of lithium ion batteries. Recent key achievements in MoS2- and MoO2-based lithium ion batteries are highlighted. Finally, we discuss the future scope and the important challenges emerging from these fascinating materials.

pH-Controllable On-Demand Oil/Water Separation on the Switchable Superhydrophobic/Superhydrophilic and Underwater Low-Adhesive Superoleophobic Copper Mesh Film

Recently, materials with controlled oil/water separation ability became a new research focus. Herein, we report a novel copper mesh film, which is superhydrophobic and superhydrophilic for nonalkaline water and alkaline water, respectively. Meanwhile, the film shows superoleophobicity in alkaline water. Using the film as a separating membrane, the oil/water separating process can be triggered on-demand by changing the water pH, which shows a good controllability. Moreover, it is found that the nanostructure and the appropriate pore size of the substrate are important for realization of a good separation effect. This paper offers a new insight into the application of surfaces with switchable wettability, and the film reported here has such a special ability that allows it to be used in other applications, such as sewage purification, filtration, and microfluidic device.

3D nitrogen-doped graphene foam with encapsulated germanium/nitrogen-doped graphene yolk-shell nanoarchitecture for high-performance flexible Li-ion battery

Flexible electrochemical energy storage devices have attracted extensive attention as promising power sources for the ever-growing field of flexible and wearable electronic products. However, the rational design of a novel electrode structure with a good flexibility, high capacity, fast charge–discharge rate and long cycling lifetimes remains a long-standing challenge for developing next-generation flexible energy-storage materials. Herein, we develop a facile and general approach to three-dimensional (3D) interconnected porous nitrogen-doped graphene foam with encapsulated Ge quantum dot/nitrogen-doped graphene yolk-shell nano architecture for high specific reversible capacity (1,220 mAh g−1), long cycling capability (over 96% reversible capacity retention from the second to 1,000 cycles) and ultra-high rate performance (over 800 mAh g−1 at 40 C). This work paves a way to develop the 3D interconnected graphene-based high-capacity electrode material systems, particularly those that suffer from huge volume expansion, for the future development of high-performance flexible energy storage systems.

pH-induced reversible wetting transition between the underwater superoleophilicity and superoleophobicity.

Surfaces with controlled oil wettability in water have great potential for numerous underwater applications. In this work, we report a smart surface with pH-responsive oil wettability. The surface shows superoleophilicity in acidic water and superoleophobicity in basic water. Reversible transition between the two states can be achieved through alteration of the water pH. Such smart ability of the surface is due to the cooperation between the surface chemistry variation and hierarchical structures on the surface. Furthermore, we also extended this strategy to the copper mesh substrate and realized the selective oil/water separation on the as-prepared film. This paper reports a new surface with excellently controllable underwater oil wettability, and we believe such a surface has a lot of applications, for instance, microfluidic devices, bioadhesion, and antifouling materials.

One-Pot Synthesis of Copper Sulfide Nanowires/Reduced Graphene Oxide Nanocomposites with Excellent Lithium-Storage Properties as Anode Materials for Lithium-Ion Batteries

Copper sulfide nanowires/reduced graphene oxide (CuSNWs/rGO) nanocompsites are successfully synthesized via a facile one-pot and template-free solution method in a dimethyl sulfoxide (DMSO)-ethyl glycol (EG) mixed solvent. It is noteworthy that the precursor plays a crucial role in the formation of the nanocomposites structure. SEM, TEM, XRD, IR and Raman spectroscopy are used to investigate the morphological and structural evolution of CuSNWs/rGO nanocomposites. The as-fabricated CuSNWs/rGO nanocompsites show remarkably improved Li-storage performance, excellent cycling stability as well as high-rate capability compared with pristine CuS nanowires. It obtains a reversible capacity of 620 mAh g(-1) at 0.5C (1C = 560 mA g(-1)) after 100 cycles and 320 mAh g(-1) at a high current rate of 4C even after 430 cycles. The excellent lithium storage performance is ascribed to the synergistic effect between CuS nanowires and rGO nanosheets. The as-formed CuSNWs/rGO nanocomposites can effectively accommodate large volume changes, supply a 2D conducting network and trap the polysulfides generated during the conversion reaction of CuS.

A bulky and flexible electrocatalyst for efficient hydrogen evolution based on the growth of MoS2 nanoparticles on carbon nanofiber foam

An advanced hydrogen evolution reaction (HER) electrocatalyst is highly desired for the development of solar water-splitting devices. In this work, we describe the preparation of a flexible, three-dimensional (3D) and durable electrode, which is composed of MoS2 nanoparticles grown on bacteria-cellulose-derived carbon fiber foam (MoS2/CNF). The MoS2/CNF foam was used as a bulky and flexible HER electrocatalyst, exhibiting excellent catalytic activity for a hydrogen evolution reaction in an acidic electrolyte (16 mA cm−2 at an overpotential of 230 mV). Remarkably, this novel HER electrocatalyst shows a low onset overpotential of 120 mV, a small Tafel slope of 44 mV dec−1, a high exchange current density of 0.09 mA cm−2, and a Faradaic efficiency of nearly 100%. This work offers an attractive strategy of preparing bulky and flexible electrocatalyst for large-scale water splitting technology.

Three-dimensional graphene–Co3O4 cathodes for rechargeable Li–O2 batteries

A three-dimensional (3D) graphene–Co3O4 electrode was prepared by a two-step method in which graphene was initially deposited on a Ni foam with Co3O4 then grown on the resulting graphene structure. Cross-linked Co3O4 nanosheets with an open pore structure were fully and vertically distributed throughout the graphene skeleton. The free-standing and binder-free monolithic electrode was used directly as a cathode in a Li–O2 battery. This composite structure exhibited enhanced performance with a specific capacity of 2453 mA h g−1 at 0.1 mA cm−2 and 62 stable cycles with 583 mA h g−1 (1000 mA h gcarbon−1). The excellent electrochemical performance is associated with the unique architecture and superior catalytic activity of the 3D electrode.

Electrochemical preparation of porous MoO3 film with a high rate performance as anode for lithium ion batteries

A porous MoO3 film is prepared by electrodeposition on Ni foam substrates and exhibits a capacity of 650 mAh g−1 at a current density of 3 A g−1 as anodes for lithium ion batteries. Electrochemical measurements demonstrate that the outstanding rate performances are due to the improved Li+ diffusion kinetics.