Table 1.

Atomic concentration calculated for detected elements using XPS spectroscopy.

Element	Atomic Concentration [at.%]
	S1	S2	S3	S4
C	69.88	70.72	68.32	93.57
N	0.67	0.37	1.36	0.70
O	28.28	28.32	26.63	5.23
Al	0.08	-	-	-
Si	0.59	0.32	0.12	0.43
S	0.50	0.27	3.58	0.07
	Ratio of atomic concentrations C/O
C/O	2.47	2.5	2.57	17.89