Haidong Bian

Fe1−xS/C nanocomposites from sugarcane waste-derived microporous carbon for high-performance lithium ion batteries

We report a novel strategy to collect microporous carbon from disposable sugarcane waste for lithium ion battery (LIB) applications. First boiled in water and ethanol and then calcined, the sugarcane waste successfully transforms into microporous carbon, delivering a specific capacity of 311 mA h g −1 at 0.33C as a LIB anode material. For improved LIB performance, pyrrhotite-5T Fe 1−x S nanoparticles were uniformly dispersed and robustly attached to the scaffold of the microporous carbon using a novel sulfurization method. A remarkably ultrahigh capacity of 1185 mA h g −1 (well beyond the theoretical value by 576 mA h g −1 ) was achieved after 200 charging/discharging cycles at a current density of 100 mA g −1 , suggesting desirable synergetic effects between Fe 1−x S and microporous carbon which lead to a shortened lithium ion transportation path, enhanced conductivity and effective prevention of polysulfide dissolution. Our approach opens a convenient route for mass-producing sustainable, superior LIB electrodes from natural wastes that can substitute commercial graphite.

Graphene-Nanowall-Decorated Carbon Felt with Excellent Electrochemical Activity Toward VO2+/VO2+ Couple for All Vanadium Redox Flow Battery

3D graphene‐nanowall‐decorated carbon felts (CF) are synthesized via an in situ microwave plasma enhanced chemical vapor deposition method and used as positive electrode for vanadium redox flow battery (VRFB). The carbon fibers in CF are successfully wrapped by vertically grown graphene nanowalls, which not only increase the electrode specific area, but also expose a high density of sharp graphene edges with good catalytic activities to the vanadium ions. As a result, the VRFB with this novel electrode shows three times higher reaction rate toward VO2 +/VO2+ redox couple and 11% increased energy efficiency over VRFB with an unmodified CF electrode. Moreover, this designed architecture shows excellent stability in the battery operation. After 100 charging–discharging cycles, the electrode not only shows no observable morphology change, it can also be reused in another battery and practical with the same performance. It is believed that this novel structure including the synthesis procedure will provide a new developing direction for the VRFB electrode.

Facile fabrication of N/S-doped carbon nanotubes with Fe3O4 nanocrystals enchased for lasting synergy as efficient oxygen reduction catalysts

Transition metal-doped carbon materials are regarded as a promising replacement of commercial Pt/C catalysts for the oxygen reduction reaction (ORR) in polymer-electrolyte-membrane fuel cells and metal–air batteries. The current fabrication methods are generally very complex and involve the introduction of foreign species onto the surface or into the voids of carbon nanostructures; this leads to loose attachment and severe aggregation over long term usage, weakening the synergetic effects between the host and guest species. Herein, we report a facile and scalable method to fabricate Fe, N, and S co-doped carbon nanotubes (Fe-NSCNT). Specifically, iron species were precipitated in situ and further converted to Fe3O4 nanoparticles enchased in the wall structures of N/S-doped CNTs (NSCNTs), resulting in a greatly reinforced synergistic effect. The Fe-NSCNT catalysts thus obtained showed excellent ORR performance, with a four-electron selectivity, high methanol tolerance, enhanced stability (no significant loss after 6 h, cf. 19% loss for 20% Pt/C), and high diffusion-limited current density (6.01 mA cm−2, higher than 5.79 mA cm−2 of the commercial Pt/C), comparable to that of the state-of-the-art Pt/C catalyst in alkaline media. Furthermore, when used as Zn–air battery cathode materials, the Fe-NSCNT catalyst enabled the same voltage (1.17 V at 20 mA cm−2) and specific capacity comparable (∼720 mA h gZn−1 at 10 mA cm−2) to that of the commercial Pt/C (∼735 mA h gZn−1 at 10 mA cm−2), indicating its great potential in replacing Pt/C for the practical applications in noble metal-free Zn–air batteries.

Mesoporous C-coated SnOx nanosheets on copper foil as flexible and binder-free anodes for superior sodium-ion batteries

Carbon-coated binder-free flexible porous SnOx nanosheets (SnO/SnO2 heterogeneous structure) were fabricated and tested as anode materials for Na-ion batteries (NIBs). The novel free-standing and binder-free porous C@SnOx nanosheets were first self-assembled on a Cu substrate via a facile, low-cost anodization method followed by the carbonization treatment. Instrumental analyses show that the porous C@SnOx nanosheets exhibit a remarkably large surface area of 221 m2 g−1, delivering a reversible discharge capacity of 510 mA h g−1 after 100 cycles at 100 mA g−1, demonstrating great potential for Na+ storage applications. The superior electrochemical performance is ascribed to the unique hierarchical porous architecture which greatly facilitates electrolyte penetration and ion transportation with the carbon coating further increasing the electrode conductivity and alleviating strains generated by volume change upon Na+ ion insertion/extraction.

In situ reduction of silver nanoparticles on hybrid polydopamine–copper phosphate nanoflowers with enhanced antimicrobial activity

The development of novel antimicrobial materials with high antimicrobial activity and low environmental impact is of importance for global health, but has proven to be challenging. Herein we report a facile mineralization process to create a flower-like, porous antimicrobial agent, which is stable, selective, effective and environmentally benign. This new antimicrobial material is made of organic polydopamine (PD) and inorganic (copper phosphate) components, where the incorporation of PD on the hybrid architecture endows the direct in situ reduction of silver ions into silver nanoparticles (Ag NPs) without the need of external toxic reductants. The combination of Ag NPs and high surface area of the nanoflower results in high selectivity in the antimicrobial activity towards Gram-negative Escherichia coli (E. coli), while leaving co-cultured mammalian cells healthy and intact. Moreover, we show that the hybrid antimicrobial material is stable, and can be easily recovered after use, avoiding the persistent hazard to the environment. We envision that this novel antimicrobial agent may find useful applications for clinical studies and industrial products.

Mesoporous SnO2 nanostructures of ultrahigh surface areas by novel anodization.

Here we report a novel type of hierarchical mesoporous SnO2 nanostructures fabricated by a facile anodization method in a novel electrolyte system (an ethylene glycol solution of H2C2O4/NH4F) followed by thermal annealing at a low temperature. The SnO2 nanostructures thus obtained feature highly porous nanosheets with mesoporous pores well below 10 nm, enabling a remarkably high surface area of 202.8 m2/g which represents one of the highest values reported to date on SnO2 nanostructures. The formation of this novel type of SnO2 nanostructures is ascribed to an interesting self-assembly mechanism of the anodic tin oxalate, which was found to be heavily impacted by the anodization voltage and water content in the electrolyte. The electrochemical measurements of the mesoporous SnO2 nanostructures indicate their promising applications as lithium-ion battery and supercapacitor electrode materials.

Water-enabled crystallization of mesoporous SnO2 as a binder-free electrode for enhanced sodium storage

Water-enabled crystallization of amorphous anodic SnO2 is reported. After low-temperature water soaking for a short period of time (e.g., 60 °C for 2 h), mesoporous rutile SnO2 with a remarkably increased surface area is achieved (nearly 2-fold that of the as-anodized SnO2 and 3.3 times that of SnO2 annealed at high temperature). Closer examination reveals that the water-crystallized SnO2 possesses a hierarchical nanostructure that features 1D nanochannels (e.g., ∼30 nm in diameter) and thin channel walls (e.g., 20 nm thick) that are comprised of tiny nanoparticles (e.g., ∼4 nm big). The water-crystallized SnO2 directly grown on the copper foil can be directly applied as a novel type of binder-free electrode for sodium-ion storage, delivering a high reversible capacity of 514 mA h g−1 after 100 cycles at a current rate of 0.1C.

Bulk monolithic electrodes enabled by surface mechanical attrition treatment-facilitated dealloying

A convenient method is developed for mass producing porous bulk metallic nanostructures with high purity, fine nanostructures of high specific surface areas, and improved mechanical performance, at low cost and high production rates. Alloys are first mechanically pretreated and grain-refined using the convenient surface mechanical attrition treatment (SMAT) and then dealloyed in an etchant solution. The reactive metal component can be effectively removed at an accelerated rate, while the more inert metal component forms a porous structure with finer porous features (e.g., ligament size) and largely suppressed “self-coarsening” effects (the undesired structural rearrangement upon long-time soaking in the etchant that results in larger structural features reducing the material overall surface area), leading to a bulk metallic framework of a well-defined nanoporous morphology and a remarkable thickness of the mm order. Monolithic supercapacitor electrodes of superior performance are enabled by coating NiIIIOOH onto the bulk porous Cu frameworks fabricated using this novel method.

Bestow metal foams with nanostructured surfaces via a convenient electrochemical method for improved device performance

Metal foams have been intensively studied as three-dimensional (3-D) bulk mass-support for various applications because of their high conductivities and attractive mechanical properties. However, the relatively low surface area of conventional metal foams largely limits their performance in applications such as charge storage. Here, we present a convenient electrochemical method for addressing this problem using Cu foams as an example. High surface area Cu foams are fabricated in a one-pot one-step manner by repetitive electrodeposition and dealloying treatments. The obtained Cu foams exhibit greatly improved performance for different applications like surface enhanced Raman spectroscopy (SERS) substrates and 3-D bulk supercapacitor electrodes.

Synthesis of Mesoporous ZIF-8 Nanoribbons and their Conversion into Carbon Nanoribbons for High-Performance Supercapacitors

ZIF-8 nanoribbons, with tunable morphology and pore structure, were synthesized by using the tri-block co-polymer Pluronic F127 as a soft template. The as-synthesized ZIF-8 nanoribbons were converted into carbon nanoribbons by thermal transformation with largely preserved morphology and porosity. The resulting carbon nanoribbons feature both micro- and meso-pores with high surface areas of over 1000 m2  g-1 . In addition, nitrogen-doping in the carbon nanoribbons was achieved, as confirmed by XPS and EELS measurements. The hybrid carbon nanoribbons provide pseudo-capacitance that promotes electrochemical performance, rendering a high specific capacitance of up to 297 F g-1 at a current density of 0.5 A g-1 in a three-electrode system. A long cycle life was also demonstrated by recording a 90.26 % preservation of capacitance after 10 000 cycles of charge-discharge at a current density of 4.0 A g-1 . Furthermore, a symmetrical supercapacitor is fabricated by employing the carbon nanoribbons, which shows good electrochemical performance with respect to energy, power and cycle life.