Atomic percentages of nitrogen content and the relative proportions of the four N species (pyridinic N, pyrrolic N, graphitic N and oxidized N) of NEA, NA and NE.

Material	N (at%)
NEA	16.41	0.5953	0.1761	0.1683	0.0603
NA	12.93	0.4476	0.2724	0.1797	0.1002
NE	10.01	0.3926	0.2681	0.1702	0.1690