Kai Han

Free-standing nitrogen-doped graphene paper as electrodes for high-performance lithium/dissolved polysulfide batteries.

Free-standing N-doped graphene papers (NGP), generated by pyrolysis of polydiallyldimethylammonium chloride, were successfully used as binder-free electrodes for the state-of-the-art Li/polysulfide-catholyte batteries. They exhibited high specific capacities of approximately 1000 mA h g(-1) (based on S) after 100 cycles and coulombic efficiencies great than 98%, significantly better than undoped graphene paper (GP). These NGP were characterized with XRD, X-ray photoelectron spectroscopy, thermogravimetric analysis, AFM, electron microscopy, and Raman and impedance spectroscopy before and after cycling. Spectroscopic evidence suggested stronger binding of sulfide to NGP relative to GP, and modelling results from DFT calculation, substantiated with experimental data, indicated that pyrrolic and pyridinic N atoms interacted more strongly with Li polysulfides than quaternary N atoms. Thus, more favorable partition of polysulfides between the electrode and the electrolyte and the corresponding effect on the morphology of the passivation layer were the causes of the beneficial effect of N doping.

Upper-critical solution temperature (UCST) polymer functionalized graphene oxide as thermally responsive ion permeable membrane for energy storage devices

A thermally responsive membrane separator, suitable for use in non-aqueous electrolytes, was constructed by grafting a UCST polymer, poly(sulfobetaine), onto graphene oxide sheets. When heated from 20 to 80 °C, it decreased the specific storage capacity of the electrode for Li by >50% reversibly, compared to 30% increase without polymer modification.

G-C3N4-coated activated carbon-supported Pd catalysts for 4-CBA hydrogenation: effect of nitrogen species

We report here a g-C3N4-coated activated carbon as the support for Pd catalysts and investigate the effect of nitrogen species in g-C3N4 on the dispersity and stability of Pd.

Supported TiO2–Pd bifunctional catalysts for the one-pot synthesis of methyl isobutyl ketone from acetone: modulation of the acid and base property of loaded TiO2 by support

In this work, we prepared a series of supported TiO2–Pd bifunctional catalysts for one-pot synthesis of methyl isobutyl ketone (MIBK) from acetone. The effects of supports including SiO2 with different pore structure, Al2O3 calcined at varied temperature, and F-modification on the catalytic performance were investigated. The results showed that microporous SiO2 was not beneficial to the dispersion of TiO2 inspite its high specific surface area. The calcination of Al2O3 had little effect on the acid and base property of TiO2 loaded thereon. F-modification of support was proved to be an effective way to modulate the acid and base property of TiO2 loaded thereon. As for the catalytic performance, TiO2 loaded on the F-modified mesoporous SiO2 showed the performance 60.9% MIBK yield, with acetone conversion of 77.2% and MIBK selectivity of 78.9%, higher than those ever reported. The excellent performance could be attributed to the enhanced electronic transfer between TiO2 and SiO2 after F modification which greatly affected the acid and base property of loaded TiO2. Taking the advantages of facile synthesis and high performance, the as-reported TiO2/SiO2(B-F)&Pd/Cor catalyst could be a promising alternative for one-pot synthesis of MIBK from acetone.