Jiuling Chen

Influence of surface functionalization via chemical oxidation on the properties of carbon nanotubes

The surface of carbon nanotubes (CNTs) was functionalized in different chemical oxidants, hydrogen peroxide, mixed concentrated HNO(3)/H(2)SO(4) and acidic KMnO(4) solution. The influences on the properties of CNTs were systematically investigated, such as the structure, the kinds and the contents of the formed surface oxygen-containing functional groups, the pH(PZC) values and the surface hydrophilicity using XRD, HREM, FTIR and chemical titration. The results show that the kinds and the contents of the surface oxygen-containing groups are dependent on the functionalization methods. The formation of the oxygen-containing groups can decrease pH(PZC) values and improve surface hydrophilicity of CNTs. The dispersion of the supported Pd-Pt particles on the functionalized CNTs and their catalytic activity in the profile reaction of naphthalene hydrogenation to tetralin are both promoted due to the presence of these oxygen-containing groups.

One-pot synthesis of carbon nanotube–graphene hybrids via syngas production

Multi-walled carbon nanotubes (MWCNTs) are limited by entanglement, and it is rather difficult to prevent graphene stacking in a polymer composite. These two challenges can be addressed by developing a MWCNT–graphene hybrid where MWCNTs and graphene are born as twins. We in this study employed a syngas production method using microwave irradiation for a one-pot synthesis of porous, crumpled and loose MWCNT–graphene hybrids, investigated the substrate compositions, measured their performance as electrodes for energy storage devices, and proposed the synthesis mechanisms. A number of hybrids, including MWCNT–graphene, MWCNT–cup-stacked CNT and MWCNT–graphitic nanofiber, were synthesized on Cr–Ni, Fe–Ni and Ni–CeO2 substrates, respectively. TEM analysis shows that the two challenges have been markedly addressed in the hybrids. They performed better in terms of capacitive properties than commercial MWCNTs.

Heterostructured electrode with concentration gradient shell for highly efficient oxygen reduction at low temperature

Heterostructures of oxides have been widely investigated in optical, catalytic and electrochemical applications, because the heterostructured interfaces exhibit pronouncedly different transport, charge, and reactivity characteristics compared to the bulk of the oxides. Here we fabricated a three-dimensional (3D) heterostructured electrode with a concentration gradient shell. The concentration gradient shell with the composition of Ba0.5-xSr0.5-yCo0.8Fe0.2O3-δ (BSCF-D) was prepared by simply treating porous Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) backbone with microwave-plasma. Electrochemical impedance spectroscopy reveals that the oxygen surface exchange rate of the BSCF-D is enhanced by ~250% that of the pristine BSCF due to the appearance of the shell. The heterostructured electrode shows an interfacial resistance as low as 0.148 Ω cm2 at 550°C and an unchanged electrochemical performance after heating treatment for 200 h. This method offers potential to prepare heterostructured oxides not only for electrochemical devices but also for many other applications that use ceramic materials.

Nano‐ and Microscale Engineering of the Molybdenum Disulfide‐Based Catalysts for Syngas to Ethanol Conversion

Nickel‐promoted MoS2, unsupported catalysts and laponite‐supported alcohol synthesis catalysts were synthesised by using microemulsion (ME) and hydrothermal (HT) methods. Highly ordered sulfide slabs, consisting of up to seven layers, were visible in the TEM images of HT‐based NiMoS2 catalysts. In contrast, disordered sulfide layers were identified in ME‐based NiMoS2 catalysts. High catalytic activity was observed in ME‐based supported (laponite‐supported NiMoS2) and unsupported catalysts. After the CO hydrogenation reaction, the catalysts were characterised by X‐ray photoelectron spectroscopy and inductively coupled plasma–mass spectrometry elemental analyses, which detected a significant sulfur loss in ME‐based NiMoS2 catalysts and minor sulfur loss in HT‐based NiMoS2 catalysts. In addition to the large surface area (120 m2 g−1), disordered sulfide structure, and exposed active sites, ME‐based NiMoS2 catalysts demonstrated higher alcohol selectivity (61 mol %) than HT‐based NiMoS2 catalysts (15 mol %). Correlations between the catalyst morphology, surface active components, and alcohol selectivity are discussed herein.

Flower-like perovskite LaCr0.9Ni0.1O3−δ–NiO nanostructures: a new candidate for CO2 reforming of methane

We have developed a facile low-cost approach to the fabrication of large-scale flower-like perovskite-type oxides: orthorhombic LaCr0.9Ni0.1O3−δ nanowires. The nanowires (∼76.2%) exhibited higher CO2 conversion than their conventional bulk counterpart (∼40.1%) due to exposure of more active sites. The unique morphological structure of the nanowires enhanced the dispersion of Pd nanoparticles on its edges and surfaces, resulting in excellent performance and stability in CO2 reforming of methane. The Pd decorated LaCr0.9Ni0.1O3−δ nanowires exhibit optimum CO2 and CH4 conversions of ∼98.6% and ∼75.4% at 800 °C. The high turnover frequency (TOF) of CH4 (6.04 s−1) on 1 wt% Pd decorated LaCr0.9Ni0.1O3−δ might be attributed to high dispersion of Pd species on the nanowires.

Difference in the cooperative interaction between carbon nanotubes and Ru particles loaded on their internal/external surface

This paper examines differences in the cooperative interaction between carbon nanotubes (CNTs) and Ru particles loaded on their internal/external surface. The techniques used were transmission electron microscopy, X-ray photoelectron spectroscopy, CO chemisorption, X-ray diffraction, N2 physisorption, hydrogen temperature-programmed reduction and two probe catalysis reactions, namely ammonia decomposition and preferential oxidation of CO in H2-rich atmosphere (PROX). The results show that the loading of highly dispersed Ru particles on CNTs does not change the structure of the CNTs. The cooperative interaction between Ru particles and associated CNT surfaces is dependent on the position of Ru particles and the surface functional groups of CNTs. Due to the electron-deficient structure of Ru particles confined inside CNT channels, they have an inferior ammonia decomposition activity to those deposited on the CNT external surface. For PROX, the catalytic performance of Ru particles confined inside CNT channels is superior compared to that over Ru particles deposited outside CNTs, which we attribute to the selective reactant enrichment of CO over H2 inside the CNTs.