Yajie Zhang

Highly dispersed nanodiamonds supported on few-layer graphene as robust metal-free catalysts for ethylbenzene dehydrogenation reaction

Highly dispersed nanodiamond (ND) aggregates with sizes ranging from 5–50 nm supported on few-layer graphene are successfully prepared for ethylbenzene dehydrogenation to styrene. The as-prepared ND/graphene catalyst presents higher catalytic performance than commercial ND powders, showing its potential application as a metal-free catalyst in the chemical industry.

Carboxyl groups trigger the activity of carbon nanotube catalysts for the oxygen reduction reaction and agar conversion

Ozone treatment is a common way to functionalize commercial multi-walled carbon nanotubes (CNTs) with various oxygen functionalities like carboxyl, phenol and lactone groups, in order to enhance their textural properties and chemical activity. In order to detail the effect of each functional group, we correlated the activity with the surface density of each group, and found that the carboxyl groups play a pivotal role in two important catalytic reactions, namely the electrochemical oxygen reduction reaction (ORR) and agar conversion to 5-hydroxymethylfurfural (HMF). During the processes, the hydrophilic surface provides a strong affinity for reaction substrates while the improved porosity allows the efficient diffusion of reactants and products. Furthermore, the activity of functionalized CNTs for agar conversion remained almost unchanged during nine cycles of reaction. This work highlights a strategy for improving the activity of CNTs for electrochemical ORR and agar conversion reactions, as well a promising application of carboxyl-rich CNTs as a solid acid catalyst to produce high-purity HMF—an important chemical intermediate.

Direct Insight into Ethane Oxidative Dehydrogenation over Boron Nitrides

The ultimate objective of chemical conversion is to achieve 100 % selectivity from catalysis, and this is also a prodigious challenge for the conversion of light paraffins into olefins, because it involves controlled activation of highly stable aliphatic C−H bonds. Herein, we show that metal‐free boron nitride (BN) nanosheets not only enable the oxidative dehydrogenation of ethane to ethylene exclusively at near 10 % conversion, but they also deliver a remarkable 60 % selectivity at an ethane conversion of 78 % and remain stable over 400 h at 575 °C. Our operando infrared spectroscopy and 18O isotope tracer study explicitly demonstrates that B−O(H) active sites are formed at the edges of BN through the aid of ethane, and the dehydrogenation circle is completed over these B−O sites by the assistance of O2.

Acidic zeolite L as a highly efficient catalyst for dehydration of fructose to 5-hydroxymethylfurfural in ionic liquid

Zeolite L was synthesized by the hydrothermal method and post-treated by NH4 exchange to adjust its acidity. The samples were systematic characterized by various techniques including XRD, X-ray fluorescence spectroscopy, N2 adsorption-desorption, scanning electron microscopy, pyridine IR spectroscopy, and NH3 temperature-programmed desorption. The results demonstrated that the NH4 -exchange post-treatment increased the surface area, micropore volume, and acidity of zeolite L. The catalytic performance of the samples was tested in the dehydration of fructose to 5-hydroxymethylfurfural (HMF) in ionic liquid (1-butyl-3-methylimidazolium bromide, [bmim]Br). 99.1 % yield of HMF was obtained when the KL-80 °C-1 h sample (KL zeolite treated with 1 m NH4 NO3 solution at 80 °C for 1 h) was used. The high efficiency could be attributed to the appropriate acid properties of the catalyst. The zeolite catalyst could be reused four times without significant decrease in activity.

Nanodiamond core reinforced graphene shell immobilized Pt nanoparticles as a highly active catalyst for low temperature dehydrogenation of n-butane

Pt nanoparticles (NPs) immobilized on a core–shell hybrid carbon support allow the efficient direct dehydrogenation of n‐butane at low temperatures. The hybrid carbon support is composed of a nanodiamond core and a reinforced ultrathin graphene shell (ND@G), which improves the stability of the anchored Pt NPs against sintering under the reaction conditions. The as‐prepared Pt/ND@G catalyst demonstrates excellent catalytic performance (≈25 % conversion with >95 % selectivity toward olefins) at 450 °C for over 10 h as a result of strong metal–support interactions. The catalyst can also be fully regenerated by postoxidative thermal treatment.

Cobalt-Doped K-OMS-2 Nanofibers: A Novel and Efficient Water-Tolerant Catalyst for the Oxidation of Carbon Monoxide

Cobalt‐doped manganese octahedral molecular sieves with an ordered cryptomelane structure (OMS‐2) were synthesized by a one‐step hydrothermal method. The cobalt precursor was directly added into the solution before crystallization to allow its incorporation into the mixed‐valent framework of K‐OMS‐2. The structure, redox properties, and surface hydrophobicity of Co‐doped K‐OMS‐2 were examined by X‐ray diffraction, FTIR spectroscopy, Raman spectroscopy, SEM, TEM, N2 sorption, temperature‐programmed reduction by H2, X‐ray photoelectron spectroscopy, and water contact‐angle system. The incorporation of Co induced a morphological change in K‐OMS‐2 from nanorods to nanofibers and an increase in the specific surface area from 70.6 to 188.3 m2 g−1. Co‐doped K‐OMS‐2 was shown to be able to completely convert CO at 100 °C in the presence of approximately 3 % water vapor. The promotion effect of Co on the catalytic activity is believed to originate from the enhanced redox capacity and surface area of K‐OMS‐2, whereas the improved surface hydrophobicity may induce superior water‐tolerant performance.

Phosphorus oxide clusters stabilized by carbon nanotubes for selective isomerization and dehydrogenation of β-isopentene

Phosphorus oxide clusters (POCs) as metal-free active centers were used for the oxidative conversion of β-isopentene, exhibiting multiple catalytic functions in isomerization, dehydrogenation and combustion, similar to metal-centered analogues (MCAs). The POCs exhibit a more efficient hydrocarbon yield than the MCAs through the reduction of the combustion products by 20-fold.