Table A3.

XPS chemical state analysis of nitrogen (N1s), sulfur (S2p), silicon (Si2p), and oxygen (O1s).

Sample	Line	Peak Position [eV]	Percentage Contribution	Atomic Concentration	Assignment
S1	N1s	399.73	53.53	0.36	C-NH-C
	N1s	401.74	46.47	0.31	pyrrolic N-H
	S2p3/2	168.26	100	0.50	sulfate or sulfoamide S-O4
	Si2p3/2	101.93	55.95	0.33	SiOx
	Si2p3/2	103.79	44.05	0.26	SiO2
	O1s	531.11	7.08	2.00	O-C=O
	O1s	532.52	86.32	24.41	C=O
	O1s	533.96	6.06	1.71	C-O-C
S2	N1s	399.57	36.35	0.13	C-N
	N1s	401.84	63.65	0.24	graphitic nitrogen
	S2p3/2	168.23	89.34	0.24	sulfate or sulfoamide S-O4
	S2p3/2	170.52	10.36	0.03	bisulfate group (HSO4−)
	Si2p3/2	101.92	100	0.32	SiOx
	O1s	531.44	12.12	3.43	O-C=O
	O1s	532.62	65.92	18.67	C-OH
	O1s	533.91	21.96	6.22	C-O-C
S3	N1s	400.25	40.75	0.55	pyrrolic nitrogen
	N1s	401.56	59.25	0.81	graphitic nitrogen
	S2p3/2	168.76	81.82	2.93	sulfate
	S2p3/2	169.54	18.18	0.65	C-S-C
	Si2p3/2	102.62	100	0.12	silicate
	O1s	531.44	10.75	2.86	O-C=O
	O1s	532.46	67.20	17.90	C=O
	O1s	533.76	22.04	5.87	C-O-C
S4	N1s	400.31	90.09	0.63	pyrrolic nitrogen
	N1s	402.45	9.91	0.07	N-O
	S2p3/2	163.77	7.69	0.01	reduced sulfide -S-
	S2p3/2	166.43	37.79	0.03	-SOn-
	S2p3/2	168.86	54.52	0.04	SOx
	Si2p3/2	99.41	43.55	0.19	bulk Si
	Si2p3/2	101.76	30.29	0.13	SiOx
	Si2p3/2	103.89	26.07	0.11	SiO2
	O1s	531.44	17.21	0.90	O-C=O
	O1s	532.64	52.69	2.76	C-OH
	O1s	533.68	14.35	0.75	O-H or C-O-C
	O1s	534.46	15.76	0.82	C(=O)(O–)2