Shuangming Li

Nitrogen-doped graphene nanosheets as metal-free catalysts for dehydrogenation reaction of ethanol

The catalytic performance of nitrogen-doped graphenes for the dehydrogenation of ethanol is investigated in this study. N-Doped graphene is synthesized by using urea and graphene oxide as nitrogen source and precursor, respectively. XRD, Raman spectra, XPS, SEM and HRTEM are utilized to characterize the structure of the synthesized N-doped graphenes. XPS reveals that the doped nitrogens on the surface exist in three forms of nitrogen atom: pyridinic, pyrrolic and graphitic. Moreover, it shows that the contents of the three states of doped N obtained from various nitrogen doped contents are different. Dehydrogenation results show that the N-doped graphene efficiently catalyzes the dehydrogenation of ethanol, and acetaldehyde is obtained as the only product without any byproduct in all the cases. In addition, the nitrogen-doped content and reaction temperature obviously have significant effects on the catalytic performance of NG. The dehydrogenation mechanism for ethanol under the catalysis of NG has also been proposed.

Synthesis and Magnetic Properties of Ferroferric Oxide in Supercritical Methanol

Ferroferric oxide was prepared using Fe(NO₃)₃ · 9H₂O as the iron source under supercritical methanol conditions. Methanol was not only a solvent but also a reducing agent in the supercritical state. The effects of reaction temperature and time, and precursor concentration on product composition were investigated. In addition, ferromagnetic ferroferric oxide was synthesized in supercritical methanol with polyvinyl pyrrolidone (PVP) and polyethylene glycol (PEG) as surfactants. The as-synthesized products were characterized by XRD, SEM, FTIR techniques. Results showed that the addition of PVP and PEG had notable influences on the products. The findings also showed that ferroferric oxide of a loose flocculent structure and with a variable size (from several tens to a few hundred nanometers) had been prepared in supercritical methanol at 300 °C and 17.8 MPa for 15 min. Magnetic properties of the ferroferric oxide were detected by vibrating sample magnetometer. Its saturation magnetization was 50 emu/g, which was lower than the bulk value of 92 emu/g and showed that it had ferromagnetism.

Boron-doped graphene as a metal-free catalyst for gas-phase oxidation of benzyl alcohol to benzaldehyde

Boron-doped graphene samples (BGs) with tunable boron content of 0–2.90 at% were synthesized and directly used in the gas-phase oxidation of benzyl alcohol to benzaldehyde, and showed excellent performance. XPS results indicated that the graphitic sp2 B species (BC3) is the mainly boron dopant species incorporated in the graphene lattice, which could significantly improve the content of ketone carbonyl groups (CO) on the graphene. For instance, the contents of CO jumped from 1.93 to 4.19 at% while BC3 doped into the graphene lattice was only 0.35 at%. The CO is the active site of catalytic reaction, so BG has significantly improved catalytic activity. Compared to the un-doped graphene (G), the conversion of benzyl alcohol over BGs increased 2.35 times and the selectivity of benzaldehyde increased from 77.3% to 99.2%. Aerobic–anaerobic exchange experiments revealed that the superior catalytic performance of BG was achieved only under aerobic conditions. The study of the boron-doped carbocatalyst may also provide guidance for the design of surface modified carbon-based catalysts for the selective oxidation dehydrogenation of alcohols by regulating doping elements and their types.