Mei-xian Wang

An aqueous media based approach for the preparation of a biosensor platform composed of graphene oxide and Pt-black.

The combination of Pt nanoparticles and graphene was more effective in enhancing biosensing than either nanomaterial alone according to previous reports. Based on the structural similarities between water soluble graphene oxide (GrO(x)) and graphene, we report the fabrication of an aqueous media based GrO(x)/Pt-black nanocomposite for biosensing enhancement. In this approach GrO(x) acted as a nanoscale molecular template for the electrodeposition of Pt-black, an amorphously nanopatterned isoform of platinum metal. Scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy (EDS) showed that Pt-black was growing along GrO(x). The effective surface area and electrocatalytic activity towards H(2)O(2) oxidation of GrO(x)/Pt-black microelectrodes were significantly higher than for Pt-black microelectrodes. When used to prepare a bio-nanocomposite based on protein functionalization with the enzyme glucose oxidase (GOx), the GrO(x)/Pt-black microbiosensors exhibited improved sensitivity over the Pt-black microbiosensors. This suggested that the GrO(x)/Pt-black nanocomposite facilitated an increase in electron transfer, and/or minimized mass transport limitations as compared to Pt-black used alone. Glucose microbiosensors based on GrO(x)/Pt-black exhibited high sensitivity (465.9 ± 48.0 nA/mM), a low detection limit of 1 μM, a linear response range of 1 μM-2mM, and response time of ≈ 4s. Additionally the sensor was stable and highly selective over potential interferents.

Investigation of the Carbon Corrosion Process for Polymer Electrolyte Fuel Cells Using a Rotating Disk Electrode Technique

The carbon corrosion process of low surface area Pt/XC72 and high surface area Pt/BP2000 was investigated using an accelerated durability testing method under simulated fuel cell conditions (a rotating disk electrode approach). A steam etching experiment was also carried out for further understanding of the carbon corrosion process for XC72 and BP2000. It was observed that different carbon corrosion processes resulted in different performance (electrochemical active surface area, mass activity, and double layer capacity) decays of catalysts. The corrosion process was studied using transmission electron microscopy. In Pt/XC72, major corrosion occurred at the center of the Pt/XC72 particle, with some minor corrosion on the surface of the carbon particle removing some amorphously structured carbon black filaments, whereas in Pt/BP2000, the corrosion started on the surface.

Structural Modification of Graphene Sheets to Create a Dense Network of Defect Sites

Pt/graphene composites were synthesized by loading platinum nanoparticles onto graphene and etched at 1000 °C in a hydrogen atmosphere. This results in the formation of a dense array of nanostructured defect sites in the graphene, including trenches, nanoribbons, islands, and holes. These defect sites result in an increase in the number of unsaturated carbon atoms and, consequently, enhance the interaction of the CO2 molecules with the etched graphene. This leads to a high capacity for storing CO2; 1 g of the etched samples can store up to 76.3 cm(3) of CO2 at 273 K under ambient pressure.

Enhancing the Catalytic Performance of Pt/C Catalysts Using Steam-Etched Carbon Blacks as a Catalyst Support

XC-72 carbon blacks were etched using steam for different times and used as a catalysts support for oxygen reduction reactions. Transmission electron microscopy (TEM) results show that the center parts of the XC-72 were more easily etched away. X-ray diffraction shows that the 002 and 10 peaks of the XC-72-based samples are initially sharp, but then broaden during the corrosion process. TEM shows that the steam etching can improve the Pt dispersion uniformity on the surface of the support and decrease the Pt particle size. Electrochemical characterization shows that the mass activity of a sample etched for 1h was better than that of the unetched samples and a commercial catalyst. The electrochemically active surface area of the samples was also significantly increased after etching. Steam etching is a simple and efficient method to increase the performance of the fuel cells catalysts.