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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.


Related in: MedlinePlus

Enlargement of the voltage window evaluated by CD at 0.2 A g−1 for (a) AS-600 and (b) AS-800. CD voltage profiles at (c) 0.5 A g−1, (d) 1 A g−1, (e) 10 A g−1 and (f) 80 A g−1 for the N-doped microporous carbon materials. Electrolyte: H2SO4.
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f5: Enlargement of the voltage window evaluated by CD at 0.2 A g−1 for (a) AS-600 and (b) AS-800. CD voltage profiles at (c) 0.5 A g−1, (d) 1 A g−1, (e) 10 A g−1 and (f) 80 A g−1 for the N-doped microporous carbon materials. Electrolyte: H2SO4.

Mentions: Constant current charge/discharge cycling (CD) experiments were performed in 1M H2SO4 electrolyte at current densities in the 0.1–80 A g−1 range. Taking into account the fact that heteroatom-doped carbon materials normally exhibit high resistance towards corrosion4041, an enlargement of the voltage window up to 1.1 V was first explored. Figure 5b and Supplementary S5 online show the voltage profiles obtained in the CD test at 0.2 A g−1 as the cell voltage was increased from 0.8 V to 1.1 V for the N-doped microporous carbons. Irrespective of the cell voltage used, the voltage profiles are symmetrical for all the materials, with coulombic efficiencies >97%, indicating that no secondary reactions, such as electrolyte decomposition or irreversible carbon corrosion, are taking place. This is corroborated by the results in Supplementary Fig. S4 online. Further confirmation of the stability of the supercapacitors at 1.1 V was obtained by long-term CD at 5 A g−1. Thus, as shown in Supplementary Fig. S6 online, capacitance loss after 10000 cycles is lower than 10% for all the N-doped microporous carbons. On the other hand, the voltage profiles for a cell voltage of 0.8 V are curved for AS-600 (Fig. 5a), AS-650 (Supplementary Fig. S5a online) and AS-700 (Supplementary Fig. S5b online), but linear for AS-800 (Fig. 5b). These results reveal that the contribution of pseudocapacitance to electrode performance decays with the rise in activation temperature, which is in accordance with the diminution of the nitrogen (and decreasing presence of N-5 and N-6) and oxygen contents. This deviation from linearity increases with cell voltage (including AS-800), hinting at an increase in the contribution of pseudocapacitance to the energy storage process, with a consequent enhancement of the specific capacitance of ca. 20%. The voltage profiles of the carbon materials are compared at diverse current densities in Fig. 5c–f. The small IR drop registered in AS-700 and AS-800 regardless of the discharge rate reflects a small equivalent series resistance (ESR) in the supercapacitor, which agrees well with the EIS measurements, and makes it possible to attain discharge rates of 80 A g−1. AS-600 and AS-650, on the other hand, cannot withstand discharge rates higher than 20 A g−1. Table 2 summarizes the values of specific capacitance obtained for the microporous materials at a cell voltage of 1.1 V and at current density of 0.2 A g−1. All the materials exhibit similar values of specific capacitance, in the ~ 250–260 F g−1 range, independently of the value of surface area, which reflects the increasing contribution of pseudocapacitance with the decrease in activation temperature. Thus, for the AS-600 sample, the material with the highest N and O contents (see Table 1), the surface area-normalized capacitance is ca. 19 μF cm−2, which is a considerably higher value than that obtained for the AS-800 sample (12 μF cm−2), the material that has the lowest N and O contents (see Table 1). These values of specific capacitance are comparable, or superior, to some types of carbon reported in the literature such as carbon derived from seaweeds, different graphene materials, carbon spheres, carbon nanocages, carbon nanofibers, activated carbons, or hydrochar-based porous carbons. A comparative table of these materials is provided in the Supporting Information (Supplementary Table S2 online).


From Soybean residue to advanced supercapacitors.

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

Enlargement of the voltage window evaluated by CD at 0.2 A g−1 for (a) AS-600 and (b) AS-800. CD voltage profiles at (c) 0.5 A g−1, (d) 1 A g−1, (e) 10 A g−1 and (f) 80 A g−1 for the N-doped microporous carbon materials. Electrolyte: H2SO4.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: Enlargement of the voltage window evaluated by CD at 0.2 A g−1 for (a) AS-600 and (b) AS-800. CD voltage profiles at (c) 0.5 A g−1, (d) 1 A g−1, (e) 10 A g−1 and (f) 80 A g−1 for the N-doped microporous carbon materials. Electrolyte: H2SO4.
Mentions: Constant current charge/discharge cycling (CD) experiments were performed in 1M H2SO4 electrolyte at current densities in the 0.1–80 A g−1 range. Taking into account the fact that heteroatom-doped carbon materials normally exhibit high resistance towards corrosion4041, an enlargement of the voltage window up to 1.1 V was first explored. Figure 5b and Supplementary S5 online show the voltage profiles obtained in the CD test at 0.2 A g−1 as the cell voltage was increased from 0.8 V to 1.1 V for the N-doped microporous carbons. Irrespective of the cell voltage used, the voltage profiles are symmetrical for all the materials, with coulombic efficiencies >97%, indicating that no secondary reactions, such as electrolyte decomposition or irreversible carbon corrosion, are taking place. This is corroborated by the results in Supplementary Fig. S4 online. Further confirmation of the stability of the supercapacitors at 1.1 V was obtained by long-term CD at 5 A g−1. Thus, as shown in Supplementary Fig. S6 online, capacitance loss after 10000 cycles is lower than 10% for all the N-doped microporous carbons. On the other hand, the voltage profiles for a cell voltage of 0.8 V are curved for AS-600 (Fig. 5a), AS-650 (Supplementary Fig. S5a online) and AS-700 (Supplementary Fig. S5b online), but linear for AS-800 (Fig. 5b). These results reveal that the contribution of pseudocapacitance to electrode performance decays with the rise in activation temperature, which is in accordance with the diminution of the nitrogen (and decreasing presence of N-5 and N-6) and oxygen contents. This deviation from linearity increases with cell voltage (including AS-800), hinting at an increase in the contribution of pseudocapacitance to the energy storage process, with a consequent enhancement of the specific capacitance of ca. 20%. The voltage profiles of the carbon materials are compared at diverse current densities in Fig. 5c–f. The small IR drop registered in AS-700 and AS-800 regardless of the discharge rate reflects a small equivalent series resistance (ESR) in the supercapacitor, which agrees well with the EIS measurements, and makes it possible to attain discharge rates of 80 A g−1. AS-600 and AS-650, on the other hand, cannot withstand discharge rates higher than 20 A g−1. Table 2 summarizes the values of specific capacitance obtained for the microporous materials at a cell voltage of 1.1 V and at current density of 0.2 A g−1. All the materials exhibit similar values of specific capacitance, in the ~ 250–260 F g−1 range, independently of the value of surface area, which reflects the increasing contribution of pseudocapacitance with the decrease in activation temperature. Thus, for the AS-600 sample, the material with the highest N and O contents (see Table 1), the surface area-normalized capacitance is ca. 19 μF cm−2, which is a considerably higher value than that obtained for the AS-800 sample (12 μF cm−2), the material that has the lowest N and O contents (see Table 1). These values of specific capacitance are comparable, or superior, to some types of carbon reported in the literature such as carbon derived from seaweeds, different graphene materials, carbon spheres, carbon nanocages, carbon nanofibers, activated carbons, or hydrochar-based porous carbons. A comparative table of these materials is provided in the Supporting Information (Supplementary Table S2 online).

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.


Related in: MedlinePlus