How the activation process modifies the hydrogen storage behavior of biomass-derived activated carbons
| Autor: | Renju Zacharia, Daniel Cossement, Ouederni Abdelmottaleb, Najoua Bader |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Materials science
Hydrogen chemistry.chemical_element 02 engineering and technology 010402 general chemistry 01 natural sciences Catalysis Hydrogen storage Adsorption Specific surface area Olive pomace medicine General Materials Science Biomass Activated carbons Activation process Mechanical Engineering Microporous material 021001 nanoscience & nanotechnology 0104 chemical sciences chemistry Chemical engineering Mechanics of Materials 0210 nano-technology Carbon Activated carbon medicine.drug |
| Popis: | Microporous activated carbons (ACs) derived from biomass residues, by virtue of their low-cost, good thermo-mechanical stability and easy adsorbent regeneration, are widely considered as hydrogen storage materials for near-term applications. The hydrogen uptake performance of activated carbons is known to depend on the pore-textural and surface characteristics, such as size and distribution of micropores and specific surface area. Here, we present a detailed investigation on how the activation processes using KOH, CO2, K2CO3, and H3PO4 modify the microstructure of olive stones-derived ACs and how they affect the ACs’ hydrogen storage behavior. The KOH-activation results in the formation of exfoliated graphene sheets, which are not common in lignocellulose-derived ACs. In addition, the KOH-activation forms supermicropores (1–2 nm) that enhance the hydrogen uptake capacity at high pressures (200 bar). The absolute hydrogen adsorption of KOH-activated sample at 200 bar and 77 K is 6.11 wt%, which is among the highest reported for activated carbon samples. The best hydrogen uptake density per surface area of the carbon we obtained is 2.1 × 10−3 wt% m−2 g which is very close to the theoretical maximum hydrogen uptake density on a single graphene sheet. CO2 and H3PO4 activations are more effective on the creation of ultramicropores (d ≤ 0.7 nm) in the carbon matrix. This order of pore size is useful when hydrogen adsorption is performed at sub-atmospheric pressures. Our study suggests that activated carbons with a homogenous pore size distribution centered at narrow range are not as efficient H2 adsorbents as the ACs with a bimodal PSD. |
| Databáze: | OpenAIRE |
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