Yuyan Shao

Durability Study of Pt ∕ C and Pt ∕ CNTs Catalysts under Simulated PEM Fuel Cell Conditions

The durability of carbon black supported Pt (Pt/C) and multiwalled carbon nanotubes supported Pt (Pt/CNTs) catalysts for potential application in polymer electrolyte membrane fuel cells are investigated using an accelerated durability test. The electrochemical surface area of Pt/C degrades by 49.8% during the 192-h test time, compared with 26.1% for Pt/CNTs, which is due to Pt particle growth and Pt loss from the support in the form of Pt ions and Pt particles. Transmission electron microscopy and X-ray diffraction analysis show that Pt particles in Pt/CNTs present higher sintering resistance. X-ray photoelectron spectroscopy characterization indicates that CNTs in Pt/CNTs are more resistant to electrochemical oxidation than carbon black in Pt/C. It can be concluded that Pt/CNTs are more stable under electrochemical operation, which can be attributed to specific interaction between Pt and the support and the higher resistance of the support to electrochemical oxidation.

In Situ Deposition of Highly Dispersed Pt Nanoparticles on Carbon Black Electrode for Oxygen Reduction

Deposition of Pt nanoparticles on electrochemically functionalized carbon black electrode for potential application in polymer membrane electrolyte fuel cells was realized with in situ ion-exchange method. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis show that carboxylic acid groups are introduced on the carbon black through electrochemical functionalization. The ion-exchange mechanism is confirmed. Scanning electron microscope and transmission electron microscope images show that Pt nanoparticles are highly dispersed on the surface of carbon black, with an average size of 4.1 nm, which is consistent with the particle size calculated through X-ray diffraction method. The electrochemical surface area is greatly increased and the Pt utilization is greatly enhanced on the ion-exchanged electrode (electrode made by in situ ion exchange method), which is 96.6%, 2.42 times that of the conventional one (39.9%). The increase in electrochemical surface area and Pt utilization is attributed to the specific structure of the ion-exchanged electrode.

Platinum Deposition on Multiwalled Carbon Nanotubes by Ion-Exchange Method as Electrocatalysts for Oxygen Reduction

Platinum supported on multiwalled carbon nanotubes (MWNTs) as electrocatalysts were prepared by the ion exchange method. The support was functionalized to create surface functional groups for the ion exchange reaction. The ion exchange was repeated for increased Pt loading. For comparison, the same loading of Pt catalyst supported on carbon nanotubes was prepared by the borohydride method. The electrocatalysts were characterized by energy dispersive analysis of X-ray, transmission electron microscopy, and X-ray photoelectron spectra. It was found that Pt/MWNTs with a high dispersion were obtained by the ion exchange method. The electrocatalytic properties of the Pt/MWNTs for oxygen reduction reaction (ORR) were investigated by cyclic voltammetry and linear sweep voltammetry. Compared with the electrocatalysts prepared by the borohydride method, Pt/MWNTs prepared with the ion exchange method showed a higher performance toward ORR and a higher Pt utilization efficiency. Furthermore, in spite of a low Pt loading (15.4 wt %), they showed a higher catalytic activity than 20 wt % E-TEK Pt/C catalyst. Thus, the ion exchange technique can provide a method for the reduction of Pt usage in Pt-based catalyst.