22177
Koutecky - Levich analysis of the samples indicates a transition of the total number of electrons transferred ( n ) in the electrochemical oxygen reduction reaction from two to four electrons upon increasing the surface concentration of platinum atoms .
 Chemical: oxygen; Chemical: platinum
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: oxygen; Chemical: platinum