Elsevier

Materials Letters

Volume 264, 1 April 2020, 127339
Materials Letters

Activated carbon derived from pitaya peel for supercapacitor applications with high capacitance performance

https://doi.org/10.1016/j.matlet.2020.127339Get rights and content

Highlights

  • Pitaya peel was used in preparing activated carbon for supercapacitors.

  • The activated carbon derived from pitaya peel has high specific surface area of 1872 m2 g−1.

  • Specific capacitance of 255F g−1 is obtained at 1 A g−1 and retains 198F g−1 at 10 A g−1.

  • 96.4% of initial capacitance is remained after 5000 cycles at 5 A g−1.

Abstract

In this paper, activated carbon with a high specific surface area up to 1872 m2 g−1 has been prepared from pitaya peel by chemical activation method using KOH solution as an activator. The novel activated carbon exhibits a significantly high specific capacitance of 255 F g−1 at a current density of 1 A g−1 in 6 M KOH, as well as excellent cycling stability with capacity retention of 96.4% after 5000 cycles at 5 A g−1. Our findings suggest that the biowaste like pitaya peel can be converted into available activated carbon, indicating a low-cost substitute for conventional electrode materials for supercapacitors.

Introduction

Supercapacitors are electrochemical energy storage devices which stimulated intensive research interest in the application of energy storage [1], [2], [3]. As the essential factor in supercapacitors, electrode materials are well established to be classified into three major types, including carbon materials, transition metal oxides and conductive polymers [4], [5], [6], [7]. Activated carbons prepared via the template method and chemical/physical activation exhibit typically high electrochemical capacitance performance attributed to their high specific surface area and suitable pore size distribution [8]. Recent reports have shown that activated carbons for supercapacitors has been synthesized successfully from numerous biowaste, which has obvious advantages of environmental friendliness, low cost and renewability. Given that, biowaste is considered as a positive alternative for conventional raw materials (such as petroleum coke, tar pitches and coal) for supercapacitors. So far, there have been numerous studies concerning activated carbon originated from multifarious biowaste such as corncob [9], bagasse [10], water bamboo [11] and cattail [12] with high electrochemical capacitance.

In this study, an activated carbon derived from pitaya peel is synthesized via KOH activation method, which exhibits a high specific capacitance of 255 F g−1 at a current density of 1 A g−1, as well as excellent cycling stability with capacity retention of 96.4% after 5000 cycles at 5 A g−1. These basic findings provide a new promising substitute from unusable biowaste to conventional raw materials for high-performance supercapacitor application.

Section snippets

Experimental section

Pitaya, a kind of fruit, is widely cultivated along tropical and subtropical areas. The pitaya peel used in the synthesized process was obtained from the fruit market, and afterward washed and cut into small pieces. After drying at 60 °C for three days, the pitaya peel was carbonized at 800 °C for 2 h under N2 to acquire pitaya peel derived carbon (PC), which was later on mixed with KOH in a weight ratio of 1:2, and activated in the same way under N2. Finally, activated carbon (AC) derived from

Results and discussion

Fig. 1 presents a schematic diagram illustrating the synthesis of AC from pitaya peel. The clean pitaya peel was dried at 80 °C to remove the excess water and carbonized at 800 °C to obtain the PC, which was later on mixed with KOH in a weight ratio of 1:2. The AC was ultimately obtained by activating the resulting mixture at 800 °C for 2 h.

The morphology of as-prepared samples was observed by SEM. The SEM image in Fig. 2a shows a big bulk structure with fold of the obtained PC. Nevertheless,

Conclusion

In summary, AC with high specific surface area of 1872 m2 g−1 have been successfully prepared from pitaya peel via chemical activation. Experimental results suggest that AC exhibits a high specific capacitance of 255 F g−1 at a current density of 1 A g−1, as well as excellent cycling stability with capacity retention of 96.4% after 5000 cycles at 5 A g−1. These outstanding results highlight the applicability of activated carbon materials derived from pitaya peel for high-performance

CRediT authorship contribution statement

Wenjing Lu: Writing - original draft. Xiaohua Cao: Data curation, Writing - original draft. Lina Hao: Data curation. Yiping Zhou: Formal analysis. Yawei Wang: Project administration, Supervision.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was financially supported by the National Natural Science Foundation of China (21680415).

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