Supplementary data

How the activation process modifies the hydrogen storage behavior of the biomass-derived activated carbons

Najoua Bader1, Renju Zacharia2[1], Ouederni Abdelmottaleb1 and Daniel Cossement3

1Research Laboratory for Process Engineering and Industrials Systems, National School of Engineers of Gabes, University of Gabes, St. Omar Ibn Khattab, 6029 Gabes, Tunisia

2Gas Processing Center, College of Engineering, Qatar University, P.O Box 2713, Doha, Qatar

3Institut de Recherché sur l’Hydrogène Université du Québec à Trois-Rivières, P.O. Box 500, Trois-Rivières, Québec G9A 5H7, Canada

S1. Porosity parameters of OP-K2CO3 sample using CO2 adsorption isotherm at 273 K

Figure S1. CO2 adsorption desorption isotherms of OP-K2CO3 sample

Table S1. Textural characteristics of OP-K2CO3 deduced from CO2 adsorption isotherms at 273 K.

Carbon / Smic
(m2. g-1) / VDR-CO2
(cm3. g-1) / L0
(nm)
OP-K2CO3 / 989 / 0.30 / 0.53

From the DR equation, the micropore volume (VDR-CO2), the characteristic adsorption energy; E0, and the mean micropore width; L0 were obtained. L0 was calculated by applying the equation[1]:

L0=2(13.03-1.53×10-5×E03.5)/E0

S2. Temperature programmed desorption (TPD-MS) analysis of OP-H3PO4 and OP-CO2 samples

Experimental: TPD followed by a mass spectrometer were performed by heating the samples up to 950°C in helium flow of 50 mL.min-1, at a heating rate of 10 °C.min-1. An omnistar quadrupole mass spectrometer from Balzers was used for evolving the amount of CO and CO2.

Results and discussion:

The TPD results include the quantification of the CO and CO2 evolved as temperature increases in a helium atmosphere. This supplies information on the chemistry of the carbon material. The CO2 evolves at low temperatures (200 to 500°C) as a result of the decomposition of surface groups of an acid nature, whereas the CO comes from weakly acidic, neutral and basic groups, which are more thermally stable and therefore evolve at higher temperatures (400 to 800°C) [2]. The CO and CO2 desorption profiles of OP-H3PO4 and OP-CO2 samples are depicted in Fig. S2. Table S3 provides quantitative results obtained by integration of the TPD profiles. One can note that H3PO4-activated carbon has evolved 3 times CO and twice CO2 as much as the CO2-activated carbon. This clearly confirms that OP-H3PO4 has more oxide functional groups on its surface compared to the physically activated sample.

Figure S2. CO and CO2 desorption profiles of OP-H3PO4 and OP-CO2

Table S2. CO and CO2 evolved quantity

Carbons / CO (mmol/g) / CO2(mmol/g) / O(mmol/g)
OP-H3PO4 / 3.43 / 0.719 / 4.86
OP-CO2 / 1.06 / 0.385 / 1.83

S3. The effect of pressure on the correlations between the cryogenic hydrogen adsorption and the porous texture parameters of activated carbons

Table S3. Linear correlation coefficient (R2) between the cryogenic hydrogen adsorption and the porous texture parameters of the activated carbons.

R2
Texture parameters / 1 bar / 25 bar
VTpore / 0.02 / 0.97
VDR-N2 / 0.10 / 0.75
VDR-CO2 / 0.67 / 0.68
SBET / 0.17 / 0.82

References

[1] R.P Bansal, J.P Donnet, and F. Stoeckli, Active Carbon. New York: Marcel Dekker, 1988.

[2] S. Haydar et al., “Regularities in the temperature-programmed desorption spectra of CO2 and CO from activated carbons,” Carbon, vol. 38, no. 9, pp. 1297–1308, 2000.

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