| AVS 58th Annual International Symposium and Exhibition | |
| Late Breaking Session | Friday Sessions |
| Session SS2-FrM |
| Session: | Surface Science Late Breaking Session |
| Presenter: | Ali Sems Ahsen, Gebze Institute of Technology, Turkey |
| Authors: | A.S. Ahsen, Gebze Institute of Technology, Turkey O.K. Ozdemir, Yildiz Tech Univ., Turkey O. Ozturk, Gebze Institute of Technology, Turkey |
| Correspondent: | Click to Email |
In this ongoing study it has been tailored surface structures and morphologies to increase chemical and structural stability for higher efficiency and improved utilization compared to presently available Pt-based catalysts used for fuel cell application. Pt-Co bi metallic alloys is selected to explore the electronic and structural properties of tailored surface and interfaces of electrocatalysts, and it is intended to explain surface chemical dynamics and interaction in fuel cell where chemical reaction pathways are influenced by the nature of the underlying support, the surfaces can be designed and modified appropriately to either promote or inhibit particular reaction.
A series of Pt and Pt-Co bi-metalic nanocatalysts alloys films were deposited on glassy-carbon disks and on a commercial hydrophobic carbon paper substrate by dc magnetron sputtering. The electronic structure and chemcial states o f surface were investigated by Photoelectron Spectroscopy (XPS and UPS). Cyclic Voltammetry (CV) and Rotating Disc Electrode (RDE) methods were used to investigate Active Surface Area (ASA) and Oxygen Reduction Reaction (ORR) kinetics . Low loading values, 6 -22 µg Pt/cm2, were observed the kinetic properties of the nanocatalysts. The highest active surface area was observed with an optimum loading of 10 µg Pt/cm2 value. Besides that the Pt-Co alloy catalysts showed significant improvement on catalytic activity against pure platinum catalysts. The effects of deposition temperature on alloy formation and reaction kinetics were also observed. A photoelectron spectroscopy study was also used for understanding electronic interaction between Pt and Co by the function of preparation temperature.
CV measurements indicate that carbon supported Pt-Co catalyst on gas diffusion electrode had electrochemical stability in the acidic environment. Also, it was observed that with increasing Co ratio metal oxidation and reduction current peaks rises. The enhancement on the ORR activity for the PtCo/C catalysts to form of the Pt-shell layer as revealed from the CV analysis, where the PtCo/C electrodes show a delayed formation of Pt-OH and faster reduction of the Pt-oxygenated containing species compared to Pt/C. It means that the oxophilicity of the PtCo/C catalysts are low compared to Pt/C. The hydrogen desorption peaks on the CV curve showed that the highest ESA value was obtained from Pt-Co(3:1) ratio. The capacitance region of PtCo catalysts increases with rising Co ratio. This is a strong evidence for that additional Co layers change the catalyst morphology. As a result, gas can reach to the reaction area easily and this reduces the ohmic resistance.