Preparation and evaluation of modified cyanobacteria-derived activated carbon for H₂ adsorption

Abstract

A series of porous carbon sorbents obtained by carbonization and activation by KOH/ZnCl 2 of the abundant waste material cyanobacteria was utilized for the adsorption of H 2 . During experiments to determine the optimal activation parameters, the activation time had little effect, whereas the KOH/C and ZnCl 2 /C mass ratios and activation temperature had a significant impact on adsorption performance. Samples activated by KOH exhibited better adsorption characteristics (such as higher values of S BET , V total , V micro , etc.) than those activated by ZnCl 2 . In particular, ACK-2-8, which had an S BET of 1951 m 2 g À1 , displayed H 2 uptake capacities of nearly 17.3 mg g À1 at À196 C and 1 bar. In addition, for evaluation of the H 2 adsorption performance, N-doped and P-doped porous carbons were synthesized using HNO 3 , NH 3 $H 2 O and H 3 PO 4 , respectively, to modify the abovementioned cyanobacteria-derived activated carbon ACK-2-8, and exhibited H 2 adsorption amounts that were 16.8%, 31.8%, and 45.7% higher, respectively, than those of undoped ACK-2-8. Furthermore, it was remarkable that P-doping in conjunction with a moderately high S BET enhanced the uptake of H 2 by ACK-2-8-2, which had a smaller S BET than ACK-2-8-3 but the best uptake capacity of up to 25.2 mg g À1 , and thereby showed that the relationship between the H 2 adsorption capacity and S BET of these materials was scarcely linear and was therefore noticeably different from previously reported results for the uptake of H 2 by other carbon sorbents. Hence, it is probable that the considerable H 2 adsorption properties of the material with a moderate S BET have great potential applications for hydrogen capture or storage.

Biomass‐derived Carbon Quantum Dots – A Review. Part 1: Preparation and Characterization

“…Activation with alkali enhances carbon yield and pores on the surface 301. KOH activation is reported to give a uniform distribution of a large number of worm‐like micropores sheet 302.…”

Marine and Freshwater Feedstocks as a Precursor for Nitrogen-Containing Carbons: A Review

“…KOH is not the only chemical activator applicable to microorganism-derived carbon manufacturing. Gao et al [ 73 ] prepared activated carbon using cyanobacteria by means of two chemical activators—KOH and ZnCl 2 . The resulting carbons activated by KOH exhibited larger amounts of micropores and mesopores, and a larger specific surface area than those activated by ZnCl 2 .…”

“…In general, micropore volume is essential for enhancing the uptake of hydrogen [ 238 , 239 ]. Guo et al [ 73 ] researched the effect of nitrogen and phosphorus heteroatoms in cyanobacteria-derived activated carbon for H 2 adsorption. In comparison with the surface groups, the S BET should have a much greater effect on the uptake of H 2 .…”