Yulin Min

B, N-codoped graphene nanoribbons supported Pd nanoparticles for ethanol electrooxidation enhancement

In this study, B, N-codoped graphene nanoribbons (BN-GNRs) were prepared on a large scale via a one-pot hydrothermal method with GNRs and an ammonium fluoroborate (NH4BF4) mixture and served as the support for Pd loading targeted for efficient ethanol electrooxidation. The synthesized Pd/BN-GNRs catalysts were characterized by TEM, XRD, XPS and electrochemical methods. The results showed that the Pd nanoparticles were uniformly loaded on BN-GNRs and the Pd/BN-GNRs exhibited much enhanced electrocatalytic activity and stability compared with Pd/GNRs and Pd/C.

Investigation of structure and photocatalytic activity on TiO2 hybridized with graphene: compared to CNT case

The structures of TiO2 hybridized with graphene by three different methods, i.e., thermal reaction, hydrolyzing synthesis and sol–gel method, were studied and their corresponding photocatalytic activities was compared by degrading RhB under UV and visible light irradiation. It was found that the 2-D graphene endowed an excellent morphology and structure for TiO2 hybridization using arbitrary synthesis routes, providing well-dispersed TiO2 particles on the graphene sheets with intimate contact. Their photocatalytic RhB degradation was strongly dependent on original TiO2 properties. However, the TiO2 hybridized with CNT via aforementioned three methods determined that their photocatalytic activity was strongly influenced by interfacial structures.

Magnetic BiFeO3 grafted with MWCNT hybrids as advanced photocatalysts for removing organic contamination with a high concentration

This work focuses on a novel visible light responsive photocatalysis system for removing organic contamination in a high concentration, employing MWCNTs as a scaffold and an efficient electron relay mediator and visible light and magnetically responsive BiFeO3. The MWCNT grafted BiFeO3 composites are fabricated by annealing an acid-functional MWCNT and Bi–Fe complex mixture at 800 °C, which induces the in situ formation of BiFeO3 particles that are grafted with the MWCNT matrix. The optimal BiFeO3/MWCNT photocatalyst exhibits enhanced photocatalytic activity under visible light, ascribed to efficient charge separation and transport which greatly extends the electron life time using MWCNTs as an electron acceptor. Simultaneously, the high surface area of the BiFeO3/MWCNT photocatalyst can act as an adsorbent to reduce organic contamination of a high concentration under an external magnetic field. The two processes composed of physical adsorption and photocatalytic degradation result in the fast removal of organic contamination during a short reaction time compared to N-doped TiO2. This work not only provides a new strategy for the fabrication of high performance multimetallic oxide grafted MWCNT photocatalysts, but also facilitates their practical application in environmental issues.

Cobalt super-microparticles anchored on nitrogen-doped graphene for aniline oxidation based on sulfate radicals

Cobalt super-microparticles anchored on nitrogen-doped graphene (Co-NG) were prepared using an inexpensive method and were tested for heterogeneous oxidation of aniline with peroxymonosulfate (PMS) in aqueous solutions. The crystal structure, morphology, and textural properties of Co-NG hybrids were investigated by various characterization techniques, such as X-ray diffraction, Raman spectroscopy, dark-field scanning transmission electron microscopy and X-ray photoelectron spectroscopy. Electron paramagnetic resonance and classical quenching tests were conducted to investigate the mechanism of PMS activation and aniline oxidation. The catalyst Co-NG exhibits an unexpectedly high catalytic activity in the degradation of aniline in water by advanced oxidation technology based on sulfate radicals (SO4-), and 100% decomposition can be achieved in 10min. This paper offers new insights on heterogeneous catalysis.

A ternary composite with manganese dioxide nanorods and graphene nanoribbons embedded in a polyaniline matrix for high-performance supercapacitors

A new ternary composite of manganese dioxide (MnO2), polyaniline (PANI) and graphene nanoribbons (GNRs) has been fabricated through a two-step polymerization process. With manganese dioxide nanorods and graphene nanoribbons embedded in the PANI matrix, the MnO2/GNRs/PANI ternary composites with 3-dimensional porous structures exhibited higher specific capacitance and better charge–discharge cycling performance than that of MnO2 and MnO2/GNRs binary composites in supercapacitors. The specific capacitance of the MnO2/PANI/GNRs ternary composite can be achieved at 472 F g−1. After 5000 cycles, the specific capacitance with 79.7% of the initial capacitance can be preserved. The enhanced specific capacitance and cycle life implies the structural stability of MnO2/GNRs/PANI ternary composites and the synergistic effect between MnO2, GNRs and PANI.

Facile fabrication of a multifunctional aramid nanofiber-based composite paper

Nowadays, aramid nanofibers (ANFs), split from macroscopic Kevlar yarns in dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH), can be used as versatile building blocks for macroscopic materials. Herein, novel Ag nanoparticles (NPs)/ANFs composite papers were facilely fabricated with a simple solution-blending and vacuum-filtration assembly. By adeptly exploiting the in situ reduction of dimethyl sulfoxide (DMSO), the Ag NPs with mean size of ∼10.2 nm can be well dispersed onto the surfaces of ANFs with electrostatic attraction between Ag+ ions and amide anions. The as-prepared Ag/ANFs composite papers exhibited flexibility and good mechanical and conductive properties. Moreover, the Ag/ANFs composite papers can act as high-performance catalysts and excellent surface enhanced Raman spectroscopy (SERS) substrates. When the feed weight ratios of ANFs and AgNO3 achieved 1 : 10, the Ag/ANFs-1 : 10 composite papers showed outstanding catalytic performance for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4 with a high first-order rate constant of 0.33 min−1. In addition, the Ag/ANFs-1 : 5 composite paper exhibited highly active and sensitive SERS enhancement for Rhodamine 6G (R6G) molecules at a detection limit of 10−12 M.

Highly dispersed palladium nanoparticles on poly(N1,N3-dimethylbenzimidazolium)iodide-functionalized multiwalled carbon nanotubes for ethanol oxidation in alkaline solution

Multi-walled carbon nanotubes (MWCNTs) have been considered as good catalyst supporting materials, and their dispersion and functionalization are important, challenging problems for high-performance composite catalysts. Here, poly(N1,N3-dimethylbenzimidazolium)iodide (P(DMBI)-I−) was successfully synthesized by methylation of polybenzimidazole (PBI) for the dispersion and functionalization of MWCNTs. The results demonstrate that the novel P(DMBI)-I− exhibits a higher dispersion effect for MWCNTs than the original PBI in some typical organic solvents. MWCNTs were wrapped with a thin layer of P(DMBI)-I− and achieved functionalization with π–π conjugation and cation–π interaction. Benefiting from the positive charges and imidazole rings of P(DMBI)-I−, the palladium nanoparticles/P(DMBI)-I−-functionalized MWCNTs hybrid (Pd/P(DMBI)-I−-f-MWCNTs) catalyst loaded with highly dispersed palladium nanoparticles was fabricated by in situ reduction. TEM and SEM images demonstrated that when the feed weight ratio of Na2PdCl4 and P(DMBI)-I−-f-MWCNTs was 6 : 1, the Pd NPs of Pd/P(DMBI)-I−-f-MWCNTs with particle size of ∼2.9 nm were well distributed on P(DMBI)-I−-f-MWCNTs in good quantity. The amount of Pd loading on the catalyst of Pd/P(DMBI)-I−-f-MWCNTs was about 56.43 wt%. With respect to ethanol oxidation in alkaline solution, the Pd/P(DMBI)-I−-f-MWCNTs exhibited higher electrochemical performance and tolerance stability, compared to commercial Pd/C and Pd/PBI-f-MWCNTs.

Simple method to construct three-dimensional porous carbon for electrochemical energy storage

A 3D porous carbon matrix with a high nitrogen content has been synthesized by employing particles of a nitrogen-enriched superabsorbent polymer (SAP) from the waste diapers of newborn babies. The derived material exhibits an ultrathin layered structure with interconnected pores and a large specific surface area. As it inherits the unique skeleton of the functional polymer from waste diapers, the resulting material (NSAPC-W) has been assessed as an inserting host anode with excellent ultralong cycling performance, as well as steady rate capability for both Li+ and Na+ ions in half cells. Furthermore, the unique structure imparts intimate structural interconnectivity, wide open channels for ion diffusion, and a large accessible surface area, as well as high structural stability, and opens up a wide horizon for electrochemical applications.

Micropores of Pure Nanographite Spheres for Long-Cycle and High-Rate Lithium-Sulfur Batteries

An effective way to prevent shuttling of polysulfides is the key to obtaining long cycle life lithium–sulfur batteries. In this paper, an effective and novel structure of pure hollow nanographite with micropores (∼8 A) was successfully synthesized, and high-rate and long cycle life lithium–sulfur batteries were obtained. Ni2+ acts as a catalyst to promote the growth of super absorbent polymers into graphite carbon shells at lower temperatures. Then, after etching the internal Ni with acid, hollow nanographite spheres are obtained and there are some micropores inside graphite carbon shells. The number of micropores can be controlled by the amount of Ni in the precursor. The existence of micropores facilitates the infiltration of sulfur in the molten state and limits the shuttling of polysulfide during charging and discharging. Therefore, the structure is apt to package sulfur by better restricting the shuttle of polysulfides, which can promote the cycle performance of the S@HNG. The fast kinetics of the graphite carbon shells can increase the rate capability. Specifically, when using S@HNG as a cathode in lithium–sulfur batteries, the specific capacity can still remain at 658 mA h g−1 under a current density of 1C after 1000 cycles. In addition, the phenomenon of self-discharge of lithium–sulfur batteries is also greatly alleviated.

Recycling application of waste Li–MnO2 batteries as efficient catalysts based on electrochemical lithiation to improve catalytic activity

The ever-increasing consumption of tons of lithium batteries, for example, Li–MnO2 batteries, has generated great concern regarding their recycling. Currently, the developed or proposed cathode recycling processes often suffer from complex recycling procedures, potential secondary pollution, high operating costs, or thermal reprocessing. The discharge of Li–MnO2 batteries involves electrochemical lithiation, which is simultaneously accompanied by the transition from Mn(IV) to Mn(III). Studies on manganese-containing catalysts have experimentally and theoretically emphasized the role of Mn(III) as an important intermediate state for enabling catalytic reactions. We present herein a simple washing-recycling process for efficiently recycling the MnO2-based cathode materials as catalysts from depleted lithium batteries. The multiple important properties of the lithiated MnO2, including phase structure, oxidation state, surface oxygen species, and structural factors, were investigated in detail. Correspondingly, the effect of the degree of electrochemical lithiation on the catalytic activity of recycled MnO2 was observed to be continuously tuned. Compared with pristine MnO2, the recycled MnO2 exhibited remarkably enhanced catalytic activity for activating PMS to decompose contaminants. The catalytic activity was correlated with the composition of LixMnO2 generated in situ in Li–MnO2 batteries owing to the tuning of the Mn valence and structural factors. This study provides an attractive method for converting the depleted electrode materials of lithium batteries into catalysts to enhance their recycling efficiency.