16452
If the samples are exposed to air prior to electrochemistry , both ORR and carbon oxidation signals are absent , and instead only small capacitive currents or currents attributed to redox chemistry of adventitious organic adsorbates are observed , indicating that air exposure results in passivation of the small Pt clusters .
 Chemical: carbon; Chemical: Pt
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: carbon; Chemical: Pt