Table 1.

Percentage of elements in the material.

Samples	Carbon [%]	Oxygen [%]	Sulphur [%]
as-obtained	15.3 ± 0.2	73.7 ± 0.3	7.6 ± 0.2
purified	41.7 ± 0.2	45.7 ± 0.2	2.4 ± 0.2
aged_as-obtained	14.7 ± 0.1	69.7 ± 0.3	8.9 ± 0.2
aged_purified	40.6 ± 0.2	44.2 ± 0.2	3.2 ± 0.1