Shiyou Yan

Electro-oxidation of Ethanol at Gas Diffusion Electrodes A DEMS Study

The ethanol electro-oxidation at gas diffusion electrodes made of different catalysts, pt/c, ptru(1:1)/c, and ptsn(7:3)/c, were studied by on-line differential electrochemical mass spectrometry in a wide temperature range (30-90 degrees c) as a function of the anode potential, the fuel concentration, and catalyst loading. the co2 current efficiency (cce) of the ethanol oxidation reaction (eor) exhibits a maximum at about 0.6 v and decreases rapidly with further increasing potentials. the cce for the eor goes down with the increase in concentration of ethanol. cce for ethanol oxidation reaction shows a strong increase with increasing catalyst loading. the cce increases with increasing temperature, exceeding 75% at 90 degrees c, 0.1 m ethanol, and 5 mg/cm(2) pt catalyst loading. ptsn/c shows high cce, like pt/c. but ptru/c exhibits very small cce. of the intermediates, acetaldehyde is quite active for further oxidation. but acetic acid is fairly resistant against further oxidation. our results indicate that the c-c bond scission observed for the eor with cce in excess of 50% has to proceed in parallel with ethanol oxidation to either acetaldehyde or acetic acid, and not sequentially from acetic acid further on, as acetic acid cannot be oxidized any further.

Synthesis and Characterization of Carbon Nanoribbons as Electrocatalyst Supports for Direct Methanol Fuel Cells

Abstract Carbon nanoribbons (CNRs) were synthesized using resorcinol—formaldehyde as precursors and characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption—desorption. CNRs are highly graphitized and the width of the ribbon is 8–20 nm. The BET surface area of CNRs is 283 m2/g, and the nitrogen isotherm for the CNRs with an average pore size of 8.2 nm is classified as type-IV. A platinum-based binary electrocatalyst, PtRu/CNRs, using CNRs as the support, with metal loading of 45%, was prepared using a modified polyol process. The performance of the single cell using PtRu/CNRs as the anode electrocatalyst is significantly improved when compared with that using Vulcan XC-72R as the support, indicating that CNRs are promising electrocatalyst supports for direct methanol fuel cells.

Studies on Electrocatalysts, MEAs and Compact Stacks of Direct Alcohol Fuel Cells

A number of carbon supported bi/multi-metallic Pt-based electrocatalysts with a metal particle-size and shape controllable in nanoscale and a narrow size distribution were prepared by the improved polyol method. Among the electrocatalysts prepared in-house, PtSn/C showed a high direct ethanol fuel cell performance and PtPd/C exhibited a favorable methanol-tolerant property and oxygen-reduction activity. Several MEA fabrication methods such as direct-spray, decal and screen-printing were developed, through which the pore structure and hydrophilic/hydrophobic properties in the MEAs could be controlled desirably. With multi-layer structured electrodes, the maximum power density of 300 mW/cm2 and 240 mW/cm2 for the single cells were achieved at 90 °C under 0.2 MPa pressures of oxygen and air, respectively. Several demonstrations of active and passive compact DMFC systems ranging from sub-watts to 200 watt were fabricated. Some of them were demonstrated in PDA, toy cars, mobile phones and laptop computers.Copyright