Cottonseed meal derived porous carbon prepared via the protease pretreatment and reduced activator dosage carbonization for supercapacitor

Abstract

The high catalytic activity and specificity of enzymes can be used to pretreat biomass. Herein, the resourceful, reproducible, cheap, and crude protein-rich cottonseed meal (CM) is selected as a precursor and the protease in the K2CO3–KHCO3 buffer solution is used as the enzyme degradation substance to pretreat CM. The crude protein content is significantly reduced by the protease degradation, and, meanwhile, it results in a looser and porous structure of CM. What is more, it significantly reduces the amount of activator. In the subsequent carbonization process, the K2CO3–KHCO3 in the buffer solution is also used as an activating agent (the mass ratio of CM to activator is 2:1), and after carbonization, the O, S, and N doped porous carbon is obtained. The optimized PCM-800-4 exhibits high heteroatom contents and a hierarchical porous structure. The specific capacitance of the prepared porous carbon reaches up to 233 F g−1 in 6M KOH even when 10 mg of active material is loaded. In addition, a K2CO3–KHCO3/EG based gel electrolyte is prepared and the fabricated flexible capacitor exhibits an energy density of 15.6 Wh kg−1 and a wide temperature range (−25 to 100 °C). This study presents a simple enzymatic degradation and reduced activator dosage strategy to prepare a cottonseed meal derived carbon material and looks forward to preparing porous carbon using other biomass.

Fractionation and Lability of Phosphorus Species in Cottonseed Meal-Derived Biochars as Influenced by Pyrolysis Temperature

“…In the field, however, raw CSM is readily mineralized and the soil-amending effect disappears in one to two growing seasons. Cottonseed meal is also a potential feedstock for valuable biofuels and bioproducts [ 9 ]. Converting CSM to biochar and bio-oil via the thermochemical technique “pyrolysis” has been explored [ 10 , 11 , 12 ].…”

“…In soils, the release of P from PL-derived biochar was greatly impacted by the soil pH [ 20 ]. As manures generally demonstrate a much higher mineral ash content relative to plant residues [ 9 ], the inherent mineral components—especially those multivalent cations such as Ca 2+ , Mg 2+ , Fe 3+ , and Al 3+ —may react with the feed P to form low-solubility phosphate minerals during the pyrolytic process and, subsequently, alter the extractability and phytoavailability of P in biochar products. Considering that CSM has a unique mineral ash composition profile in addition to the relatively high P content, the P speciation and lability (in terms of extractability and phytoavailability) of CSM-derived biochar may be distinctive and respond differently to the effects of the pyrolysis temperature.…”