An-Ya Lo

Structural evolution and electrocatalytic application of nitrogen-doped carbon shells synthesized by pyrolysis of near-monodisperse polyaniline nanospheres

Near-monodisperse polyaniline (PANI) colloids with controlled particle size (55–90 nm) were prepared by disperse polymerization of aniline in the presence of a steric stabilizer: polyvinylpyrrolidone (PVP). The silica-coated PANI colloidal nanospheres were further subjected to pyrolysis treatment at different temperatures (400–950 °C) to fabricate the nitrogen-doped carbon shells (NCSs). The NCSs so obtained were found to have controllable morphologies and pore sizes (13.4–23.2 nm). A possible structural evolution of the PANI colloids during pyrolysis process is proposed based on results obtained from a variety of characterization techniques. Upon loading Pt metal, the supported Pt/NCS catalysts were found to exhibit superior catalytic performance during electrooxidation of methanol, surpassing that of the conventional Pt/Vulcan XC-72 catalyst. The effects of nitrogen doping and carbon shell structure on Pt dispersion, tolerance of CO poisoning, and electrochemical properties are also examined and discussed.

Controlled synthesis of highly dispersed platinum nanoparticles in ordered mesoporous carbons

A novel route has been developed to fabricate ordered carbon mesoporous materials with well-dispersed, highly stable Pt nanoparticles of ca. 2-3 nm on the pore walls using platinum acetylacetonate as the co-feeding carbon and Pt precursor.

Adsorption of lysozyme on spherical mesoporous carbons (SMCs) replicated from colloidal silica arrays by chemical vapor deposition.

Spherical mesoporous carbons (SMC) were successfully synthesized by chemical vapor deposition (CVD) method using ferrocene as the carbon precursor and colloidal silica arrays as templates. The structure and textural properties of SMCs were characterized by a variety of techniques. Accordingly, a possible formation mechanism was proposed. These SMC materials were found to exhibit extraordinary high adsorption capacities (ca. 100mumol/g) for lysozyme (Lz) in solution with a pH value of 11 close to its isoelectric point. The correlations between the textural parameters of SMCs with Lz adsorption capacity were also investigated along with discussion on its adsorption kinetics and stability.

Effect of Temperature Gradient Direction in the Catalyst Nanoparticle on CNTs Growth Mode.

To improve the understanding on CNT growth modes, the various processes, including thermal CVD, MP-CVD and ECR-CVD, have been used to deposit CNTs on nanoporous SBA-15 and Si wafer substrates with C2H2 and H2 as reaction gases. The experiments to vary process parameter of ΔT, defined as the vector quantities of temperature at catalyst top minus it at catalyst bottom, were carried out to demonstrate its effect on the CNT growth mode. The TEM and TGA analyses were used to characterize their growth modes and carbon yields of the processes. The results show that ΔT can be used to monitor the temperature gradient direction across the catalyst nanoparticle during the growth stage of CNTs. The results also indicate that the tip-growth CNTs, base-growth CNTs and onion-like carbon are generally fabricated under conditions of ΔT > 0, <0 and ~0, respectively. Our proposed growth mechanisms can be successfully adopted to explain why the base- and tip-growth CNTs are common in thermal CVD and plasma-enhanced CVD processes, respectively. Furthermore, our experiments have also successfully demonstrated the possibility to vary ΔT to obtain the desired growth mode of CNTs by thermal or plasma-enhanced CVD systems for different applications.

Acidity and sorption properties of nano-sized mesoporous aluminosilicate materials

A comprehensive study on the acidic and sorptive properties of nano-sized, H-form mesoporous aluminosilicate materials with varied Si/Al ratio (15–200), prepared by microwave synthesis under base conditions, has been made. Their acidic properties were characterized by solid-state multinucleus ( 1 H, 27 Al, and 31 P) MAS-NMR and pyridine-IR spectroscopy, whereas their sorption and surface properties were probed by hyperpolarized (HP) 129 Xe NMR. Complementary results were obtained revealing the co-existence of Bronsted and Lewis acid sites in these nano-sized aluminosilicates. In particular, one type of strong Bronsted acid site, whose acidic strength is comparable to conventional zeolites, was identified. However, results obtained from HP- 129 Xe NMR of adsorbed Xe reveal that the local environments on the pore surfaces of these nano-sized materials are rather similar regardless of the sample Al contents.