Improvement of Mesoporosity on Supercapacitive Performance of Activated Carbons Derived From Coffee Grounds

Abstract

Activated carbons with different porosities derived from coffee, which prepared by the potassium hydroxide (KOH) activation method, are used as electrode for supercapacitors. The prepared materials indicated a well-designed porous structure that provides countless adsorption sites, leading to high supercapacitor performance. Mesopores allow rapid diffusion of electrolyte ions, while micropores usually provide abundant adsorption sites for ions. Therefore, appropriate control over pore-size distributions is a key factor for good electrochemical performance. The porosity and surface structure of activated coffee grounds (ACGs) are highly dependent on both the activation temperature and KOH/carbonized materials weight ratio. The ACGs were characterized using N 2 adsorption at 77 K. The specific surface area increased from 1.75 to 3065 m 2 /g. Cyclic voltammetry and galvanostatic charge-discharge tests were employed in the evaluation of the electrochemical behavior of each sample. The ACG materials have a high specific capacitance of 127.8 F/g and cycle stability after 2500 cycles.

Valorization of waste coffee grounds into microporous carbon materials for CO2 adsorption

“…These elemental contents are comparable to those reported in previous studies on coffee-ground-based ACs. 17,30 With the increasing K 2 C 2 O 4 reagent ratio, the total N content gradually decreases from 3.0 (CCG) to 0.8 at% (CAC5), whereas the total O content increases from 10.1 to 12.5 at%. These results are consistent with those obtained from the previously described bulk EA, demonstrating that the surface chemistry and elemental composition are in accordance with the bulk form.…”

“…However, CAC5 exhibits a considerable decrease in S BET and the micropore volume likely because of the microporous framework collapse at the highest activating reagent ratio. This microstructural collapse results from the extensive erosion of the carbon structures 25,30 due to excessive activation.…”

The second life of coffee can be even more energizing: Circularity of materials for bio-based electrochemical energy storage devices

“…49 The ratio between KOH and carbon was confirmed to have a strong impact on the activation procedure also by Lee et al who very recently obtained hierarchical porous carbon with a 3065 m 2 g −1 surface area and a good specific capacity of 127.8 F g −1 in sodium sulfate electrolyte with a good stability over 2500 cycles, by employing a KOH/carbon ratio of 8:1 in the activation step. 50 It is interesting to note as a recent work by Gadipelli et al highlighted the high performances of highly porous CDC for electrochemical energy storage applications compared to other nanoporous materials, as pinecones-derived nanoporous carbons, graphene oxide, and metal-organic frameworks. Besides electrical charge storage, CO2, H2, and water storage multifunctional properties were also examined.…”

Beneficial effect of steam on synthesis of hierarchically porous zeolite‐templated carbons

“…In aforementioned applications, the hierarchically meso‐/microporous carbons clearly show the synergistic combination, and outperform solely microporous or mesoporous carbons. [ 6,7 ]…”

“…In aforementioned applications, the hierarchically meso-/microporous carbons clearly show the synergistic combination, and outperform solely microporous or mesoporous carbons. [6,7] There are several routes to synthesize hierarchically porous carbon, such as a post-treatment of mesoporous carbon with CO 2 , [1] the carbonization of mesostructured phenol-formaldehyde resins [2] and chlorination of mesoporous silicon carbide. [8] As another approach, the synthesis using nanocrystalline beta zeolites (NBZ) as a hard template was reported.…”