20869
Such excellent performances may be attributed to the synergistic effect , which includes high catalytic sites for ORR provided by high S - N heteroatom loading , excellent reactant transport caused by hierarchical pore structures and high electron transfer rate provided by 3D continuous networks .
 Chemical: S; Chemical: N
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: S; Chemical: N