Table 2.

Elemental surface compositions of FSG and PFSG.

Sample	C	N	O	Fe	Sn	–N=	–NH–	Doping Level N+/N
	(at.%)					(%)
FSG	63.9	2.6	29.8	3.0	0.9	-	-	-
PFSG	74.6	11.7	12.2	0.8	0.7	21	62	17