Lisong Chen

One-step synthesis of sulfur doped graphene foam for oxygen reduction reactions

Sulfur doped graphene foam has been successfully synthesized by a simple solve-thermal method, which exhibited a much enhanced oxygen reduction reaction (ORR) catalytic activity as well as an especially high electrochemical stability, and would be a promising non-metal cathode catalyst for the ORR.

SnO2 nanocrystal-decorated mesoporous ZSM-5 as a precious metal-free electrode catalyst for methanol oxidation

A novel precious metal-free electrode catalyst SnO2/m-ZSM-5 nanocomposite has been successfully synthesized. This SnO2/m-ZSM-5 nanocomposite shows high and stable electrochemical catalytic activity for methanol oxidation, which is comparable to Pt/C. The high electrochemical performance has been attributed to the synergetic catalytic effects between the mesoporous ZSM-5 matrix and the loaded SnO2 nanocrystals.

One-step replication and enhanced catalytic activity for cathodic oxygen reduction of the mesostructured Co3O4/carbon composites

Mesostructured Co3O4/C composites of high surface area have been synthesized via a one-step replica route by co-nanocasting cobalt and carbon precursors into mesoporous silica, in which the Co3O4 nanoparticles are homogeneously dispersed in the mesoporous structure of carbon substrates. The mesostructured composites showed relatively high catalytic activities for oxygen reduction reaction (ORR), and that with a Co loading content of 4.3 at% exhibited the best electrochemical performance for ORR. The relatively high catalytic activity is attributed to the effects of the redox couples (Co(3+)/Co(2+)) together with the contribution from the conductive mesoporous carbon substrate.

Hollow mesoporous carbon cubes with high activity towards the electrocatalytic reduction of oxygen.

Hollow-structured mesoporous carbon cubes (HMCCs) have been successfully synthesized from carbon dioxide by a facile approach based on thermal reduction of magnesium. The approach is economical and applicable to large-scale synthesis. Notably, pyrrole-type nitrogen species are doped into the HMCCs during the synthesis in situ, that is, without introducing a nitrogen-containing precursor. A formation mechanism of the HMCCs is proposed, and formation of the structure is attributed to MgO templates generated in situ. Furthermore, the HMCCs are demonstrated to be a promising alternative to commercial Pt/C fuel-cell catalysts for the electrochemical oxygen reduction reaction.

One-step hydrothermal synthesis of nitrogen-doped carbon nanotubes as an efficient electrocatalyst for oxygen reduction reactions.

A high amount of heteroatom doping in carbon, although favorable for enhanced density of catalytically active sites, may lead to substantially decreased electroconductivity, which is necessary for the electrochemical oxygen reduction reaction. Herein, a relatively low amount of nitrogen was successfully doped into carbon nanotubes (CNTs) by a hydrothermal approach in one step, and the synthesized nitrogen-doped CNT (CNT-N) materials retained most of the original, excellent characteristics, such as the graphitic structure, tubular morphology, and high surface area, of CNTs. The resultant CNT-N materials, although containing a relatively low amount of nitrogen doping, exhibited high electrocatalytic ORR activity, comparable to that of 20 wt% Pt/C; long durability; and, more importantly, largely inhibited methanol crossover effect.

Microwave-Assisted Synthesis of Co-Coordinated Hollow Mesoporous Carbon Cubes for Oxygen Reduction Reactions

Transition-metal-/metal-oxide-loaded mesoporous carbon materials with hollow structures are thought to have great potential as catalysts, especially in the areas of sustainable chemistry and energy conversion. However, it is hard to load transition metals/metal oxides onto carbon materials while keeping the carbon materials unchanged through traditional after-treatment processes, thus making it difficult to determine the true roles of the transition metal/metal oxide and carbon in the reactions. Here, Co-coordinated hollow mesoporous carbon cubes (CoMHMCCs) were prepared by a microwave-assisted approach in the presence of ethylene glycol and hollow mesoporous carbon cubes (HMCCs). The synthesized CoMHMCCs inherited most advantages of the HMCCs, such as large surface area and pore volume, uniform pore size distribution, and hollow mesoporous structure, and the Co species was found to coordinate with the N atoms in the N-doped hollow mesoporous carbon cubes. The synthesized CoMHMCCs exhibited a much enhanced oxygen electroreduction reaction activity (∼50 mV deviation from Pt/C), a high selectivity (number of electrons transferred = 3.7-3.9), and excellent electrochemical stability (as low as 12 mV negative shift of half-wave potential after 5000 potential cycles) as a result of a synergetic catalytic effect.

Amorphous Fe2+-rich FeOx loaded in mesoporous silica as a highly efficient heterogeneous Fenton catalyst

A simple physical-vapor-infiltration (PVI) method using ferrocene as the iron source, has been developed to load FeOx into the pore channels of mesoporous silica SBA-15. The obtained FeOx/SBA-15 composite has a high loading amount of FeOx (e.g. 26.64 wt% Fe content obtained at PVI duration 17 h and calcination temperature 450 °C) but unblocked pore channels thanks to the unique preparation strategy. The FeOx species are amorphous, rich of Fe(2+) and have been highly dispersed as a nanocoating onto the pore channel surface. The FeOx/SBA-15 composite was used as a heterogeneous Fenton catalyst to degrade Acid orange 7 (AO7). It showed a high catalytic activity and degradation efficiency, which was attributed to the high proportion of Fe(2+) in the amorphous FeOx and their favorable adsorption capability for the dye. The influences of the PVI duration, the calcination temperature and the Fenton reaction conditions (FeOx/SBA-15 dosages, H2O2 dosages and initial pH value) on the catalytic activity were investigated in detail.

Synergetic Catalytic Effects in Tri-Component Mesostructured Ru–Cu–Ce Oxide Nanocomposite in CO Oxidation

This work focuses on probing the synergetic catalytic effects in mesostructured tri‐component Ru–Cu–Ce oxides in CO oxidation reaction. The crystallized nanocomposites with RuO2 and CuO nanoparticles dispersed homogeneously in the pore network of mesoporous CeO2 were synthesized by the nanocasting replication method. The greatly enhanced catalytic activity was achieved by CuO incorporating in mesoporous CeO2, and further by RuO2 incorporating in the mesostructure of CuO/CeO2. Two types of synergetic catalytic mechanisms have been preliminarily proposed to be copresent in the system: CeO2 activation by CuO through generating oxygen vacancies at CeO2/CuO interface and the CeO2 surface nearby, which consequently activate the oxygen species (O*) and enhance the CO oxidation activity of the bi‐metal CuCe oxide, and the simultaneous adsorption of CO molecules and their activation in parallel on the active surface of RuO2, which results in further elevated catalytic activity.

Manganese Oxide Nanorod-Decorated Mesoporous ZSM-5 Composite as a Precious-Metal-Free Electrode Catalyst for Oxygen Reduction.

A precious-metal-free cathode catalyst, MnO2 nanorod-decorated mesoporous ZSM-5 zeolite nanocomposite (MnO2 / m-ZSM-5), has been successfully synthesized by a hydrothermal and electrostatic interaction approach for efficient electrochemical catalysis of the oxygen reduction reaction (ORR). The active MnOOH species, that is, Mn(4+) /Mn(3+) redox couple and Brønsted acid sites on the mesoporous ZSM-5 matrix facilitate an approximately 4 e(-) process for the catalysis of the ORR comparable to commercial 20 wt % Pt/C. Stable electrocatalytic activity with 90 % current retention after 5000 cycles, and more importantly, excellent methanol tolerance is observed. Synergetic catalytic effects between the MnO2 nanorods and the mesoporous ZSM-5 matrix are proposed to account for the high electrochemical catalytic performance.

Post-synthesis of hierarchically structured Ti-β zeolites and their epoxidation catalytic performance

Abstract Hierarchically structured Ti-β zeolites were prepared using a two-step post-synthesis approach. The physicochemical properties of the resultant Ti- m β-S x materials were determined using various techniques, including X-ray diffraction, scanning electron microscopy, inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, and ultraviolet-visible and ultraviolet-Raman spectroscopies. The porous structures of the synthesized hierarchical Ti-β zeolites were well preserved. Their catalytic performance was compared with that of pure microporous Ti-β materials using alkene epoxidation as a model reaction. It was found that although comparable catalytic activities were obtained for both types of catalyst in the epoxidation of small molecules, e.g., cyclohexene, the synthesized hierarchical Ti-β gave an enhanced catalytic performance in the epoxidation of bulky 1-dodecene.