Zhongqing Jiang

Plasma Induced Grafting Carboxymethyl Cellulose on Multiwalled Carbon Nanotubes for the Removal of UO22+ from Aqueous Solution

Carboxymethyl cellulose (CMC) is grafted on multiwalled carbon nanotubes (MWCNT) by using plasma techniques. The CMC grafted MWCNT (MWCNT-g-CMC) is characterized by using Fourier transform infrared spectra (FT-IR), Raman spectra, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA)-differential thermal analysis (DTA), scanning electron microscopy (SEM), and N(2)-BET methods in detail. The application of MWCNT-g-CMC in the removal of UO(2)(2+) from aqueous solution is investigated. MWCNT-g-CMC has much higher sorption ability in the removal of UO(2)(2+) than raw MWCNT. The MWCNT-g-CMC is a suitable material in the preconcentration and solidification of heavy metal ions from large volume of aqueous solutions.

Composite membranes based on sulfonated poly(ether ether ketone) and SDBS-adsorbed graphene oxide for direct methanol fuel cells

Sodium dodecylbenzene sulfonate (SDBS) adsorbed graphene oxide (GO) has been used as a filler to modify sulfonated poly(ether ether ketone) (SPEEK). The incorporation of SDBS-GO greatly increases the ion-exchange capacity (IEC), water uptake, and proton conductivity, while it reduces the methanol permeability through the SPEEK membranes. With well controlled contents of SDBS-GO, the composite membranes exhibit higher IEC, water uptake, and proton conductivity and lower methanol permeability than Nafion® 112, making them attractive as proton exchange membranes (PEMs). These superior characteristics make the composite membranes with optimized SDBS-GO contents exhibit superior performance in direct methanol fuel cells (DMFCs) compared to the plain SPEEK or Nafion® 112 membranes.

Amine-functionalized holey graphene as a highly active metal-free catalyst for the oxygen reduction reaction

Amine functionalized holey graphene (AFHG), synthesized by the hydrothermal reaction of GO and ammonia and the subsequent KOH etching, has been used as a metal-free catalyst for the oxygen reduction reaction (ORR). It shows that AFHG is highly active for the ORR and exhibits higher electrocatalytic activity than graphene, nitrogen-doped graphene (NG) and amine functionalized graphene (AFG), which could be demonstrated from its higher current density and more positive half-wave and onset potentials for the ORR. Although AFHG also exhibits a slightly higher overpotential towards ORR, it is indeed more kinetically facile than the commercial JM Pt/C 40 wt%. Its higher electrochemical performance could be attributed to the presence of the electron donating group (e.g. amine) and a large number of holes in its sheet plate and the porous structure in its randomly stacked solid, which provide AFHG with higher electrical conductivity, more active edge N atoms and easier accessibility to oxygen, respectively. The stability measurements show that AFHG is more stable than graphene, NG, AFG and the JM Pt/C 40 wt% and exhibits higher immunity towards methanol crossover and CO poisoning than the JM Pt/C 40 wt%. Over 10 h of the ORR, AFHG loses only <7% of its original activity in the absence of methanol or CO, and the introduction of methanol or CO has no effect on its oxygen reduction activity, which makes it highly desirable as a metal-free catalyst for the ORR.

Randomly stacked holey graphene anodes for lithium ion batteries with enhanced electrochemical performance

Holey graphene (HG) synthesized by a hydrothermal method followed by etching with KOH and ball milling is randomly stacked to form a porous structure. These randomly stacked holey graphene anodes exhibit high rate capability with excellent cycling stability as an anode material for lithium-ion cells. This fascinating electrochemical performance can be ascribed to their specific porous structure, providing numerous active sites for Li+ insertion, reduced effective diffusion distance for the Li+ ions, high electrical conductivity, low charge-transfer resistance across the electrolyte–electrode interface, and improved structural stability against the local volume change during Li+ insertion–extraction.

Cobalt oxide-coated N- and B-doped graphene hollow spheres as bifunctional electrocatalysts for oxygen reduction and oxygen evolution reactions

A simple and scalable method has been developed for the synthesis of Co3O4-coated N- and B-doped graphene hollow spheres (Co3O4/NBGHSs). These Co3O4/NBGHSs are highly active for both oxygen reduction and evolution reactions and can exhibit higher electrocatalytic activities and better durability than commercial Pt/C and RuO2/C, respectively, demonstrating them to be efficient bi-functional electrocatalysts. In-depth analysis shows that the coupling between Co3O4 and NBGHSs, strong interaction with adsorbed O2, high electric conductivity, and the specific hollow structure play important roles in imparting the higher electrocatalytic activities to the Co3O4/NBGHSs. When tested as cathode catalysts for Zn–air batteries, the Co3O4/NBGHSs exhibit better performance and higher stability than the Pt/C catalyst and other catalysts reported previously. This strongly suggests that the Co3O4/NBGHSs could be used as efficient electrocatalysts for metal–air batteries with great potential to replace precious metal/carbon based materials.

Porous B-doped graphene inspired by Fried-Ice for supercapacitors and metal-free catalysts

An easy and efficient approach inspired by the ‘Fried-Ice’ concept has been developed for the preparation of boron-doped graphene (B-G) with porous morphologies. The morphology, boron content, and specific surface area (SSA) of these porous graphenes could be well tuned by controlling the reaction temperature. Because of the steam etching effect, the as-prepared porous B-Gs have a high SSA of up to 622 m2 g−1. The porous B-doped graphene electrodes show promising performance in supercapacitors with a gravimetric capacitance of up to 281 F g−1. As metal-free electrocatalysts for the oxygen reduction reaction in alkaline medium, these electrodes facilitate the four-electron transfer process with high performances in limited current density and high onset potential (−0.12 V vs. SCE) that is close to that of the commercial Pt/C (40 wt%) and excellent tolerance to methanol and carbon monoxide.

Synthesis of monodispersed Pt nanoparticles on plasma processed carbon nanotubes for methanol electro-oxidation reaction

Plasma-treated multi-walled carbon nanotubes (MWCNTs) have been used as a substrate for the deposition of Pt nanoparticles. These Pt nanoparticles deposited on MWCNTs showed a higher catalytic activity in a methanol electro-oxidation reaction even with a lower amount of precious metal catalyst used. The higher catalytic activity is attributed to less damage of the carbon nanotubes during plasma treatment. It also shows that direct contact between metal nanoparticles and carbon nanotubes can improve the performance of composites.

Hydrothermal Synthesis of Boron and Nitrogen Codoped Hollow Graphene Microspheres with Enhanced Electrocatalytic Activity for Oxygen Reduction Reaction

Boron and nitrogen codoped hollow graphene microspheres (NBGHSs), synthesized from a simple template sacrificing method, have been employed as an electrocatalyst for the oxygen reduction reaction (ORR). Because of their specific hollow structure that consists of boron and nitrogen codoped graphene, the NBGHSs can exhibit even high electrocatalytic activity toward ORR than the commercial JM Pt/C 40 wt %. This, along with their higher stability, makes the NBGHSs particularly attractive as the electrocatalyst for the ORR with great potential to replace the commonly used noble-metal-based catalysts.

High performance of a free-standing sulfonic acid functionalized holey graphene oxide paper as a proton conducting polymer electrolyte for air-breathing direct methanol fuel cells

The membranes constructed from sodium dodecylbenzenesulfonate adsorbed holey graphene oxides (SDBS-HGO)s have been used as proton exchange membranes for air-breathing direct methanol fuel cell applications. Due to the specific holey structure of graphene oxide which provides additional transport pathways for protons across the graphene oxide nanosheet and the presence of strong proton exchange groups which provide them with high proton conductivity, the SDBS-HGO membranes exhibit comparable proton conductivity and lower methanol permeability in comparison to the commercial Nafion® 112. The electrochemical results show that the air-breathing direct methanol fuel cell with the SDBS-HGO membranes as the PEMs exhibit much higher performance and better stability than that with Nafion® 112, which clearly demonstrates the possibility of using such SDBS-HGO based papers for air-breathing direct methanol fuel cell applications.

Reduction of the oxygen reduction reaction overpotential of nitrogen-doped graphene by designing it to a microspherical hollow shape

Nitrogen-doped hollow graphene microspheres (NHGSs), synthesized through a procedure involving the calcination of graphene–oxide-wrapped amine-functionalized mesoporous silica nanoparticles (AFMSNs) and the subsequent removal of the AFMSNs via HF etching, have been employed as an electrocatalyst for the oxygen reduction reaction (ORR). It has been shown that these NHGSs are highly active toward ORR and exhibit higher electrocatalytic activity than graphene, nitrogen-doped graphene (NG), hollow graphene microspheres (HGSs), and JM Pt/C 40 wt%, and a comparable overpotential to JM Pt/C 40 wt%. Their high electrocatalytic activity could be attributed to the N-doped graphitic structure, which produces more active sites for the ORR, allowing the easier adsorption of oxygen and the subsequent reduction; and the specific microspherical hollow structure, which promotes the exposure of more surface area accessible to electrolytes, thereby allowing an easier diffusion of electrolytes into and out of the electrode catalyst layers. Their low overpotential for the ORR can be attributed to the specific microspherical hollow structure, which reduces the overpotential contribution from the mass transport limitation. The stability measurements show that NHGSs also exhibit a much higher stability than graphene, NG, HGSs, and JM Pt/C 40 wt%, and are immune to the methanol crossover and CO poisoning effects, which all together makes NHGSs highly attractive as an electrocatalyst for the ORR.