24749
We find that simple elementary steps in which a proton is transferred to an adsorbate ( such as the protonation of * CO to * COH ) have small barriers on the order of 0 . 1 eV .
 CO, COH
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 CO, COH