Surface Chemistry of Carbon Black Electrocatalyst Supports as a Result of a Commercial Synthethic Route

摘要

A common electrocatalyst support, Vulcan XC72, was taken through a commercial catalyst synthetic route by Tanaka Kikinzoku Kogyo without depositing platinum and subsequently heat treated to produce samples of various surface-modified blacks. These support materials, which are used in polymer electrolyte membrane fuel cell electrode layers, were characterized by both surface and bulk characterization techniques to understand the impact of process steps on formation and removal of oxygen-containing functional groups and their effect on surface acidity of the supports. We present a rigorous cleaning procedure of the processed samples to eliminate free ions and synthesis precursors present on the support surfaces that prohibit accurate data collection. It is shown that strongly acidic functional groups are introduced during the catalyzation process by sacrificing only about 10% of the C-C bonding. Subsequent heat-treatment slowly destroys these functional groups, and while heat-treatment to 1000°C brings the elemental surface composition back to that of the base carbon, the oxygen containing moieties are different.