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Performance of a polymer electrolyte membrane fuel cell with a Pd cathode catalyst was systemically investigated in this study. The Pd catalyst was directly formed on a gas diffusion layer by using electrodeposition (Pd/GDL). The electrodeposition formed aggregates of Pd nanoparticles on a gas diffusion layer with the preferred orientation of Pd(111) and Pd(200). In addition, the Pd aggregates mainly formed on the top surface of the gas diffusion layer. The membrane electrode assembly was fabricated with Pd/GDL as the cathode. The performance of the membrane electrode assembly was investigated by varying hot pressing parameters and back pressures, and the operating condition for the polymer electrolyte membrane fuel cell was optimized. Notably, introducing back pressure increased operating current density at 0.6 V by up to 45%. Durability of the membrane electrode assembly was also examined. Negligible deterioration of surface morphology of the Pd catalyst was observed even after accelerated stress testing, except for a slight increase in particle size. The results indicate that deterioration of the Pd cathode catalyst was not a major factor affecting overall single-cell performance degradation. [ABSTRACT FROM AUTHOR]

In this study, the facile and direct formation of platinum catalyst on a carbon paper (gas diffusion layer) via the sonochemical deposition method is demonstrated. An ultrasound irradiation with a carbon paper substrate in a platinum precursor solution formed interconnected platinum grains on the carbon paper surface. The surface morphology and deposition amount of platinum were strong functions of both ultrasound parameters (power and time) and solution composition. The platinum-deposited carbon paper was then directly used as a gas diffusion electrode in PEMFC without adding the ionomer. This exhibited high stability in the accelerated stress test in a single cell operation. The interconnected grains of platinum on carbon paper had high resistance to dissolution in an oxidizing environment and the absence of carbon support also enhanced resistance to carbon oxidation. Although the overall performance did not exceed that of the commercial Pt/C, this approach may be an option to form a stable platinum catalyst for PEMFCs. [ABSTRACT FROM AUTHOR]

Novel synthesis of a Pt catalyst encapsulated in a N-containing carbon layer for use in a polymer electrolyte membrane fuel cell is described in this study. A Pt-aniline complex, formed by mixing Pt precursor and aniline monomer, was used as the source of Pt, C, and N. Heat treatment of the Pt-aniline complex with carbon black yielded 5 nm Pt nanoparticles encapsulated by a N-containing carbon layer originating from aniline carbonization. The synthesized Pt catalyst exhibited higher mass specific activity to oxygen reduction reaction than that shown by conventional Pt/C catalyst because pyridinic N with graphitic carbon in the carbon layer provided active sites for oxygen reduction reaction in addition to those provided by Pt. In single cell testing, initial performance of the synthesized catalyst was limited because the thick catalyst layer increased resistance related to mass transfer. However, it was observed that the carbon layer successfully prevented Pt nanoparticles from growing via agglomeration and Ostwald ripening under fuel cell operation, thereby improving durability. Furthermore, a mass specific performance of the synthesized catalyst higher than that of a conventional Pt/C catalyst was achieved by modifying the synthesized catalyst's layer thickness. [ABSTRACT FROM AUTHOR]