Surfactant modified platinum based fuel cell cathode studied by X-ray absorption spectroscopy

Abstract A carbon supported Pt catalyst with tetradecyltrimethylammonium bromide (TTAB) adsorbed to the nanoparticle surface was operated and tested as a cathode in a polymer electrolyte membrane fuel cell. The fuel cell with the TTAB@Pt/C catalyst showed a higher current relative to the amount of Pt used than the fuel cell with a commercial Pt/C catalyst. Besides, CO stripping evidenced that for the TTAB@Pt/C electrode large parts of the Pt surface were covered by TTAB. Hence, the fuel cell with the TTAB@Pt/C cathode showed a larger current related to the electrochemical active surface area as compared to the fuel cell with the commercial Pt/C cathode. This improvement in the ORR kinetics was further investigated by X-ray photoelectron and in-situ X-ray absorption spectroscopy, and was found to have been caused by two effects: (1) the presence of a metal-ligand charge transfer in the TTAB@Pt/C electrode and (2) the prevention of oxygen containing adsorbates which were being formed in large amounts on the Pt/C electrode. Furthermore, the latter effect also explains the higher stability observed for the TTAB@Pt/C compared to the Pt/C electrode.