Pei Tang

Methane activation: the past and future

The conversion of methane to more valuable chemicals is one of the most intensively studied topics in catalysis. The direct conversion of methane is attractive because the process is simple, but unfortunately its products are chemicals that are more reactive than methane. The current status of this research field is discussed with an emphasis on C–H bond activation and future challenges.

Direct catalytic oxidation of benzene to phenol over metal-free graphene-based catalyst

We report an efficient, highly selective, and low temperature graphene-catalyzed reaction process for one-step oxidation of benzene to phenol with hydrogen peroxide as the oxidant. The chemically converted graphene (CCG) from small graphite was used as the catalyst. The conversion of benzene reaches 18%, with phenol being the sole product. The catalyst was reusable and very stable. By XPS, C K-edge X-ray absorption spectra, benzene-TPD, and kinetic measurements, it was concluded that the moderate H2O2 activation rate, good benzene adsorption ability, and balanced kinetic control over the oxidation reaction are responsible for the outstanding catalytic performance of the metal-free catalyst.

Monodispersed bimetallic PdAg nanoparticles with twinned structures: Formation and enhancement for the methanol oxidation

Monodispersed bimetallic PdAg nanoparticles can be fabricated through the emulsion-assisted ethylene glycol (EG) ternary system. Different compositions of bimetallic PdAg nanoparticles, Pd80Ag20, Pd65Ag35 and Pd46Ag54 can be obtained via adjusting the reaction parameters. For the formation process of the bimetallic PdAg nanoparticles, there have two-stage growth processes: firstly, nucleation and growth of the primary nanoclusters; secondly, formation of the secondary nanoparticles with the size-selection and relax process via the coalescence or aggregation of the primary nanoclusters. The as-prepared PdAg can be supported on the carbon black without any post-treatment, which exhibited high electro-oxidation activity towards methanol oxidation under alkaline media. More importantly, carbon-supported Pd80Ag20 nanoparticles reveal distinctly superior activities for the methanol oxidation, even if compared with commercial Pt/C electro-catalyst. It is concluded that the enhanced activity is dependant on the unique twinning structure with heterogeneous phase due to the dominating coalescence growth in EG ternary system.

Graphene Oxide Catalyzed C−H Bond Activation: The Importance of Oxygen Functional Groups for Biaryl Construction

A heterogeneous, inexpensive, and environmentally friendly graphene oxide catalytic system for the C-H bond arylation of benzene enables the formation of biaryl compounds in the presence of aryl iodides. The oxygen functional groups in these graphene oxide sheets and the addition of KOtBu are essential for the observed catalytic activity. Reactions with various model compounds and DFT calculations confirmed that these negatively charged oxygen atoms promote the overall transformation by stabilizing and activating K(+) ions, which in turns facilitates the activation of the C-I bond. However, the graphene π system also greatly facilitates the overall reaction as the aromatic coupling partners are easily adsorbed.

The microwave adsorption behavior and microwave-assisted heteroatoms doping of graphene-based nano-carbon materials

Microwave-assisted heating method is used to treat graphite oxide (GO), pyrolytic graphene oxide (PGO) and hydrogen-reduced pyrolytic graphene oxide (HPGO). Pure or doped graphene are prepared in the time of minutes and a thermal deoxygenization reduction mechanism is proposed to understand their microwave adsorption behaviors. These carbon materials are excellent catalysts in the reduction of nitrobenzene. The defects are believed to play an important role in the catalytic performance.

Construction of Stable Chainlike Au Nanostructures via Silica Coating and Exploration for Potential Photothermal Therapy

A facile one-pot approach is successfully developed to construct the stable Au nanochains with silica shell via self-assembly and classical Stöber process. The resulting Au chain@SiO2 nanoparticles holds great promise for serving as a safe, reusable, and high-performance photothermal agent against cancer.

Growth mechanism of N-doped graphene materials and their catalytic behavior in the selective oxidation of ethylbenzene

Abstract N-doped graphene materials were prepared from both inorganic and organic nitrogen sources and pyrolytic graphene oxide as the carbon substrate. Transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were used to investigate the detailed growth mechanism of the N species in these N-doped graphene materials. The different chemical nature and binding energy of the different N species resulted in their different trends with annealing temperature. These N-doped graphene are excellent catalysts in the oxidation of ethylbenzene. A high yield of acetonphenone did not depend on the total nitrogen amount but only on the type of nitrogen species. Too much defects and N-dopants were detrimental to this reaction. A proper activation of the oxidant is needed to get good catalytic activity.