Chengling Zhu

N-doped porous carbon with magnetic particles formed in situ for enhanced Cr(VI) removal

A newly designed N-doped porous carbon with magnetic nanoparticles formed in situ (RHC-mag-CN) was fabricated through simple impregnation then polymerization and calcination. The doped nitrogen in RHC-mag-CN was in the form of graphite-type layers with the composition of CN. The resultant nanocomposite maintained a high surface area of 1136 m(2) g(-1) with 18.5 wt% magnetic nanoparticles (Fe3O4 and Fe) inside, which showed a saturation magnetization (Ms) of 22 emu/g. When used as an adsorbent, the RHC-mag-CN demonstrated a very quick adsorption property for the removal of Cr(VI), during which 92% of Cr(VI) could be removed within 10 min for dilute solutions at 2 g L(-1) adsorbent dose. The high adsorption capacity (16 mg g(-1)) is related to the synergetic effects of physical adsorption from the surface area and chemical adsorption from complexation reactions between Cr(VI) and Fe3O4. Importantly, the basic CNs in RHC-mag-CN increase its negative charge density and simultaneously increase the adsorption of metallic cations, such as Cr(3+) formed in the acid solution from the reduction of Cr(VI). The formation of magnetic nanoparticles inside not only supplies complexing sites for the adsorption of Cr(VI), but also shows perfect magnetic separation performance from aqueous solution.

Tailoring the Morphology of g‐C3N4 by Self‐Assembly towards High Photocatalytic Performance

We report a novel method for the preparation of graphitic carbon nitride (g‐C3N4) with various morphologies through self‐assembly and calcination, which starts from the raw materials melamine, urea, and cyanuric acid. The hollow to wormlike morphologies of g‐C3N4 could be readily tailored by adjusting the molar ratio of melamine to urea; with increase in the molar ratio from 3:1 to 1:3, a morphology transformation was observed. The morphologies were tailored by self‐assembly of the aggregates by hydrogen bonding and ionic interactions. Correspondingly, an increased BET surface area from 49.6 to 97.4 m2 g−1 was observed. If used as a photocatalyst in degrading rhodamine B (RhB) under visible‐light irradiation, these g‐C3N4 samples demonstrated 7 to 13 times higher performance than conventional bulk g‐C3N4. The high performance was attributed to the unique morphology that provided not only high specific surface area but low recombination losses of photogenerated charges.

Bioinspired Carbon/SnO2 Composite Anodes Prepared from a Photonic Hierarchical Structure for Lithium Batteries

A carbon/SnO2 composite (C-SnO2) with hierarchical photonic structure was fabricated from the templates of butterfly wings. We have investigated for the first time its application as the anode material for lithium-ion batteries. It was demonstrated to have high reversible capacities, good cycling stability, and excellent high-rate discharge performance, as shown by a capacitance of ∼572 mAh g(-1) after 100 cycles, 4.18 times that of commercial SnO2 powder (137 mAh g(-1)); a far better recovery capability of 94.3% was observed after a step-increase and sudden-recovery current. An obvious synergistic effect was found between the porous, hierarchically photonic microstructure and the presence of carbon; the synergy guarantees an effective flow of electrolyte and a short diffusion length of lithium ions, provides considerable buffering room, and prevents aggregation of SnO2 particles in the discharge/charge processes. This nature-inspired strategy points out a new direction for the fabrication of alternative anode materials.

Confined SnO2 quantum-dot clusters in graphene sheets as high-performance anodes for lithium-ion batteries

Construction of metal oxide nanoparticles as anodes is of special interest for next-generation lithium-ion batteries. The main challenge lies in their rapid capacity fading caused by the structural degradation and instability of solid-electrolyte interphase (SEI) layer during charge/discharge process. Herein, we address these problems by constructing a novel-structured SnO2-based anode. The novel structure consists of mesoporous clusters of SnO2 quantum dots (SnO2 QDs), which are wrapped with reduced graphene oxide (RGO) sheets. The mesopores inside the clusters provide enough room for the expansion and contraction of SnO2 QDs during charge/discharge process while the integral structure of the clusters can be maintained. The wrapping RGO sheets act as electrolyte barrier and conductive reinforcement. When used as an anode, the resultant composite (MQDC-SnO2/RGO) shows an extremely high reversible capacity of 924 mAh g−1 after 200 cycles at 100 mA g−1, superior capacity retention (96%), and outstanding rate performance (505 mAh g−1 after 1000 cycles at 1000 mA g−1). Importantly, the materials can be easily scaled up under mild conditions. Our findings pave a new way for the development of metal oxide towards enhanced lithium storage performance.

Construction of SnO 2 −Graphene Composite with Half-Supported Cluster Structure as Anode toward Superior Lithium Storage Properties

Inspired by nature, herein we designed a novel construction of SnO2 anodes with an extremely high lithium storage performance. By utilizing small sheets of graphene oxide, the partitioned-pomegranate-like structure was constructed (SnO2@C@half-rGO), in which the porous clusters of SnO2 nanoparticles are partially supported by reduced graphene oxide sheets while the rest part is exposed (half-supported), like partitioned pomegranates. When served as anode for lithium-ion batteries, SnO2@C@half-rGO exhibited considerably high specific capacity (1034.5 mAh g−1 after 200 cycles at 100 mA g−1), superior rate performance and remarkable durability (370.3 mAh g−1 after 10000 cycles at 5 A g−1). When coupled with graphitized porous carbon cathode for lithium-ion hybrid capacitors, the fabricated devices delivered a high energy density of 257 Wh kg−1 at ∼200 W kg−1 and maintained 79 Wh kg−1 at a super-high power density of ∼20 kW kg−1 within a wide voltage window up to 4 V. This facile and scalable approach demonstrates a new architecture for graphene-based composite for practical use in energy storage with high performance.

Fabrication of AgBr/boron-doped reduced graphene oxide aerogels for photocatalytic removal of Cr(VI) in water

AgBr nanoparticles on boron-doped reduced graphene oxide aerogels (AgBr/B-RGO) are synthesized by a facile hydrothermal method, which shows a superior performance in the photoreduction of toxic hexavalent chromium (CrVI) in aqueous media under visible light irradiation. The composition and structure of the samples have been characterized by using XPS, Raman, XRD, TEM and SEM measurements. As compared with that of AgBr on none-doped reduced graphene oxide aerogels (AgBr/RGO), the improved photocatalytic properties, can be attributed to the introduction of boron atoms in reduced graphene oxide (RGO), bringing in the improvement of electron transfer efficiency, and the depression of the recombination of photo-excited electrons and holes. Further tests in the photoreduction of CrVI reveal that the obtained AgBr/B-RGO presents excellent cycling performance with an interesting increase in the photocatalytic efficiency upon cycling number. This observation can be explained by the fact that the gradual emergence of Ag0 formed from the photo-induced decomposition of AgBr, introduces a Surface Plasmon Resonance (SPR) effect to the system. The approach herein reported could be extended to the design and fabrication of other photocatalysts with high performance that combine the boron-doped graphene and SPR effect.

Coupled Chiral Structure in Graphene-Based Film for Ultrahigh Thermal Conductivity in Both In-Plane and Through-Plane Directions

The development of high-performance thermal management materials to dissipate excessive heat both in plane and through plane is of special interest to maintain efficient operation and prolong the life of electronic devices. Herein, we designed and constructed a graphene-based composite film, which contains chiral liquid crystals (cellulose nanocrystals, CNCs) inside graphene oxide (GO). The composite film was prepared by annealing and compacting of self-assembled GO-CNC, which contains chiral smectic liquid crystal structures. The helical arranged nanorods of carbonized CNC act as in-plane connections, which bridge neighboring graphene sheets. More interestingly, the chiral structures also act as through-plane connections, which bridge the upper and lower graphene layers. As a result, the graphene-based composite film shows extraordinary thermal conductivity, in both in-plane (1820.4 W m-1 K-1) and through-plane (4.596 W m-1 K-1) directions. As a thermal management material, the heat dissipation and transportation behaviors of the composite film were investigated using a self-heating system and the results showed that the real-time temperature of the heater covered with the film was 44.5 °C lower than a naked heater. The prepared film shows a much higher efficiency of heat transportation than the commonly used thermal conductive Cu foil. Additionally, this graphene-based composite film exhibits excellent mechanical strength of 31.6 MPa and an electrical conductivity of 667.4 S cm-1. The strategy reported here may open a new avenue to the development of high-performance thermal management films.