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From Soybean residue to advanced supercapacitors.

Ferrero GA, Fuertes AB, Sevilla M - Sci Rep (2015)

Bottom Line: Supercapacitor technology is an extremely timely area of research with fierce international competition to develop cost-effective, environmentally friendlier EC electrode materials that have real world application.Interestingly, when Li2SO4 is used, the voltage window is extended up to 1.7 V (in contrast to 1.1 V in H2SO4).Thus, the amount of energy stored is increased by 50% compared to H2SO4 electrolyte, enabling this environmentally sound Li2SO4-based supercapacitor to deliver ~12 Wh kg(-1) at a high power density of ~2 kW kg(-1).

View Article: PubMed Central - PubMed

Affiliation: Instituto Nacional del Carbón (CSIC), P.O. Box 73, Oviedo 33080, Spain.

ABSTRACT
Supercapacitor technology is an extremely timely area of research with fierce international competition to develop cost-effective, environmentally friendlier EC electrode materials that have real world application. Herein, nitrogen-doped carbons with large specific surface area, optimized micropore structure and surface chemistry have been prepared by means of an environmentally sound hydrothermal carbonization process using defatted soybean (i.e., Soybean meal), a widely available and cost-effective protein-rich biomass, as precursor followed by a chemical activation step. When tested as supercapacitor electrodes in aqueous electrolytes (i.e. H2SO4 and Li2SO4), they demonstrate excellent capacitive performance and robustness, with high values of specific capacitance in both gravimetric (250-260 and 176 F g(-1) in H2SO4 and Li2SO4 respectively) and volumetric (150-210 and 102 F cm(-3) in H2SO4 and Li2SO4 respectively) units, and remarkable rate capability (>60% capacitance retention at 20 A g(-1) in both media). Interestingly, when Li2SO4 is used, the voltage window is extended up to 1.7 V (in contrast to 1.1 V in H2SO4). Thus, the amount of energy stored is increased by 50% compared to H2SO4 electrolyte, enabling this environmentally sound Li2SO4-based supercapacitor to deliver ~12 Wh kg(-1) at a high power density of ~2 kW kg(-1).

No MeSH data available.


Schematic of the synthesis of N-doped microporous carbon from a protein-rich biomass residue derived from soybean (photos of soybean and protein-rich biomass residue were taken by G. A. Ferrero, photos of hydrochar and SEM and TEM pictures were taken by A. B. Fuertes, photos of HTC reactor and soybean oil were taken by M. Sevilla and the picture of N-moieties was done by M. Sevilla).
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f1: Schematic of the synthesis of N-doped microporous carbon from a protein-rich biomass residue derived from soybean (photos of soybean and protein-rich biomass residue were taken by G. A. Ferrero, photos of hydrochar and SEM and TEM pictures were taken by A. B. Fuertes, photos of HTC reactor and soybean oil were taken by M. Sevilla and the picture of N-moieties was done by M. Sevilla).

Mentions: Soybean is widely used for oil production, mainly but not entirely, for human consumption. Even though soybean origins are in Southeast Asia, nowadays it is produced worldwide, ensuring easy access. In the last decade, the oil production from soybean has steadily grown, from ~30 million tons in 2004 to more than 45 million tons in 2014293031. This production process leaves behind high amounts of a solid residue, i.e. defatted soybean, better known as soybean meal (see Fig. 1). This soybean meal has been traditionally used for animal feed due to its high protein content. However, this high protein content makes this abundant and cost-effective residue highly suitable for a more advanced application, such as its use as precursor for the fabrication of high added-value materials, i.e. N-doped porous carbon materials. Herein we demonstrate that this can be achieved based on a “green” process such as hydrothermal carbonization, as depicted in Fig. 1. In this regard, some of us have previously shown that the hydrothermal co-carbonization of glucose with a N-rich biomass of low carbohydrate content (i.e. microalgae Spirulina Platensis) has beneficial effects on both the hydrochar yield and N content32. The same strategy has been followed in this work, resulting in a two-fold increase in the hydrochar yield and a three-fold increase in the nitrogen efficiency (defined as the percentage of N contained in the defatted soybean/glucose mixture retained in the hydrochar), as is shown in Supplementary Fig. S1a online. Furthermore, as can be deduced from Fig. S1b, the degree of carbonization (the higher the degree of carbonization, the lower the H/C and O/C ratios) of the dSB/glucose-derived hydrochar is higher than that of the dSB-derived hydrochar, although both have the same N/C ratio. This result suggests that a higher product yield would be obtained in the activation step as a consequence of a lower burn-off, as has been previously shown when comparing hydrochar with biomass25. Indeed, a 10% increase in product yield was recorded. This result is important from a technological and environmental standpoint as it shows that a smaller amount of corrosive KOH can be used to generate the same amount of activated carbon.


From Soybean residue to advanced supercapacitors.

Ferrero GA, Fuertes AB, Sevilla M - Sci Rep (2015)

Schematic of the synthesis of N-doped microporous carbon from a protein-rich biomass residue derived from soybean (photos of soybean and protein-rich biomass residue were taken by G. A. Ferrero, photos of hydrochar and SEM and TEM pictures were taken by A. B. Fuertes, photos of HTC reactor and soybean oil were taken by M. Sevilla and the picture of N-moieties was done by M. Sevilla).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4645100&req=5

f1: Schematic of the synthesis of N-doped microporous carbon from a protein-rich biomass residue derived from soybean (photos of soybean and protein-rich biomass residue were taken by G. A. Ferrero, photos of hydrochar and SEM and TEM pictures were taken by A. B. Fuertes, photos of HTC reactor and soybean oil were taken by M. Sevilla and the picture of N-moieties was done by M. Sevilla).
Mentions: Soybean is widely used for oil production, mainly but not entirely, for human consumption. Even though soybean origins are in Southeast Asia, nowadays it is produced worldwide, ensuring easy access. In the last decade, the oil production from soybean has steadily grown, from ~30 million tons in 2004 to more than 45 million tons in 2014293031. This production process leaves behind high amounts of a solid residue, i.e. defatted soybean, better known as soybean meal (see Fig. 1). This soybean meal has been traditionally used for animal feed due to its high protein content. However, this high protein content makes this abundant and cost-effective residue highly suitable for a more advanced application, such as its use as precursor for the fabrication of high added-value materials, i.e. N-doped porous carbon materials. Herein we demonstrate that this can be achieved based on a “green” process such as hydrothermal carbonization, as depicted in Fig. 1. In this regard, some of us have previously shown that the hydrothermal co-carbonization of glucose with a N-rich biomass of low carbohydrate content (i.e. microalgae Spirulina Platensis) has beneficial effects on both the hydrochar yield and N content32. The same strategy has been followed in this work, resulting in a two-fold increase in the hydrochar yield and a three-fold increase in the nitrogen efficiency (defined as the percentage of N contained in the defatted soybean/glucose mixture retained in the hydrochar), as is shown in Supplementary Fig. S1a online. Furthermore, as can be deduced from Fig. S1b, the degree of carbonization (the higher the degree of carbonization, the lower the H/C and O/C ratios) of the dSB/glucose-derived hydrochar is higher than that of the dSB-derived hydrochar, although both have the same N/C ratio. This result suggests that a higher product yield would be obtained in the activation step as a consequence of a lower burn-off, as has been previously shown when comparing hydrochar with biomass25. Indeed, a 10% increase in product yield was recorded. This result is important from a technological and environmental standpoint as it shows that a smaller amount of corrosive KOH can be used to generate the same amount of activated carbon.

Bottom Line: Supercapacitor technology is an extremely timely area of research with fierce international competition to develop cost-effective, environmentally friendlier EC electrode materials that have real world application.Interestingly, when Li2SO4 is used, the voltage window is extended up to 1.7 V (in contrast to 1.1 V in H2SO4).Thus, the amount of energy stored is increased by 50% compared to H2SO4 electrolyte, enabling this environmentally sound Li2SO4-based supercapacitor to deliver ~12 Wh kg(-1) at a high power density of ~2 kW kg(-1).

View Article: PubMed Central - PubMed

Affiliation: Instituto Nacional del Carbón (CSIC), P.O. Box 73, Oviedo 33080, Spain.

ABSTRACT
Supercapacitor technology is an extremely timely area of research with fierce international competition to develop cost-effective, environmentally friendlier EC electrode materials that have real world application. Herein, nitrogen-doped carbons with large specific surface area, optimized micropore structure and surface chemistry have been prepared by means of an environmentally sound hydrothermal carbonization process using defatted soybean (i.e., Soybean meal), a widely available and cost-effective protein-rich biomass, as precursor followed by a chemical activation step. When tested as supercapacitor electrodes in aqueous electrolytes (i.e. H2SO4 and Li2SO4), they demonstrate excellent capacitive performance and robustness, with high values of specific capacitance in both gravimetric (250-260 and 176 F g(-1) in H2SO4 and Li2SO4 respectively) and volumetric (150-210 and 102 F cm(-3) in H2SO4 and Li2SO4 respectively) units, and remarkable rate capability (>60% capacitance retention at 20 A g(-1) in both media). Interestingly, when Li2SO4 is used, the voltage window is extended up to 1.7 V (in contrast to 1.1 V in H2SO4). Thus, the amount of energy stored is increased by 50% compared to H2SO4 electrolyte, enabling this environmentally sound Li2SO4-based supercapacitor to deliver ~12 Wh kg(-1) at a high power density of ~2 kW kg(-1).

No MeSH data available.