13237
Highly effective Ir ( x ) Sn ( 1 - x ) O2 electrocatalysts for oxygen evolution reaction in the solid polymer electrolyte water electrolyser .
 Chemical: Ir; Chemical: Sn; Chemical: O2; Chemical: oxygen
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: Ir, Sn, O2, oxygen 
Answer:
 Chemical: Ir; Chemical: Sn; Chemical: O2; Chemical: oxygen