*Properties and the supercapacitor performances of some of the biomass derived carbon based materials.*

material with heating. Resulting highly porous activated carbon is applied to a supercapacitor and it showed comparable performances in aqueous and organic electrolytes. In another study, Liang et al. [55] reported nitrogen and sulfur codoped hierarchical porous carbon (NSPC) with a high gravimetric capacitance around 350 F g−1. They used the NaHCO3/KHCO3 activated foxtail grass seeds as precursor biomass. Also, Cao et al. [52] studied the effect of nitrogen containing groups of NH4Cl, (NH4)2CO3 and urea on the electrochemical performances of biomass derived hierarchical porous materials. They reported that, NH4Cl is proved to be the porogen with the minimum collapse of pollen grain and urea can be identified as the most effective N dopant with the 300 F g−1 capacitance value. Du et al. [56] presented a silica activation process for the carbon produced from the carrot biomass. In this study nitrogen enriched porous carbon is produced by a simple activation method. Nitrogen enrichment is preferred to achieve a higher porous structure. Low-cost Na2SiO3 served as initiator and provided catalytic effect on the nitrogen doping process. In general the resulting material showed around 270 F g−1. These results showed that the choice of the biomass precursor is very important that, while carrots are used as the carbon source, the vitamins in carrot biomass can serve as a nitrogen reserve. Ariharan et al. [57] reported a facile synthesis of selfphosphorous doped porous carbon material from Honeyvine milkweed (Pod fluff as a precursor) by a simple carbonization route without using any activation process under argon gas atmosphere. They achieved nearly 250 F g−1 capacitance value and showed an excellent supercapacitance recovery after 10000 cycles with 95% recovery. They also examined the H2 storage capacity of the synthesized porous material and achieved successful performances. The reported study offers an effective route for the stable, conductive and highly porous carbon based material synthesis and their effective utilization in both energy applications.

Waste paper cups were used as a source for the synthesis of a carbon support that is loaded with Fluorescein molecules [58]. The resulting composite is successfully applied to a supercapacitor electrode and showed 214 F g-1 specific capacitance. Here the main point is that waste lignocellulosic materials are also a very promising tools for electrochemical response enhancement.

Mostly, the regions and their agricultural potentials are determinative for biomass source selection. In China rice based carbon production is very promising and their wastes are also bear huge biomass potentials. Xie et al. [59] used puffed-rice as a precursor material for carbon sheet structures. They applied gradual heat treatment to the source material and achieved the best performance from R-800 sample. They reached nearly 120 F g−1 capacitance performance. It is moderate but energy and power densities are recorded as attainable performances. They also utilized the material in microwave absorption beyond a supercapacitor material. So it has been shown that true selection of the biomass precursor can construct a bridge from the biomass derived materials to sustainable development. Orange peels are also used as a biomass source for activated carbon production [60]. The produced activated carbon is indicated as a very highly porous structure and its nanocomposite was produced by the combination with poly aniline. They both utilized for the supercapacitor material. Hybrid structure exhibited nearly 4 folds of higher capacitance value than the natural form. Another citrus based study is reported by Gehrke et al. [61]. The activated carbons synthesized from *Citrus bergamia* peels by activation with phosphoric acid (AC - H3PO4) and manganese nitrate (AC – Mn3O4). Among these materials AC – Mn3O4 exhibited the best electrochemical performance due to the active transition metal content with a specific capacitance value of 290 F g−1. Leaf extracts are widely used for the green synthesis of metallic nanoparticles. In this process the reactive organic groups in the extracts are utilized as reducing and

*Biomass Based Materials in Electrochemical Supercapacitor Applications DOI: http://dx.doi.org/10.5772/intechopen.98353*

stabilizing for metals. *Aloe vera* parts are also used for this purpose. Similar to this approach NiO is modified with the biomolecules in the *Aloe vera* extract to enhance the surface properties. Apart from the above mentioned carbonaceous material synthesis based studies here the composite structure is obtained by the modification of the NiO mas a metal oxide with the biomolecules. Resulted material improved the anodic and cathodic peak potentials of the NiO and provided longer stability and charge–discharge capacity [62]. He et al. [63] reported an interesting study on the effect of the mixture usage as raw biomass material. The raw biomass composed of, rice husk, reed rod, Platanus fruit, fibers, flax fiber, and walnut Shell. The mixture of these materials is rinsed and grinded than calcinated under nitrogen atmosphere finally Hierarchical porous hollow carbon nanospheres (HCNSs) were fabricated. This one step process is also performed by the addition of polytetrafluoroethylene (PTFE) to raw biomass. Both the hollow carbons served well as a supercapacitor additive since they possess core-shell pores. Also silica content improved the mesoporosity of the structure very much.

#### **4. Conclusion**

The utilization of the carbon based materials in the improvement of the electrochemical performances of energy production and storage devices has reached an important stage. In this manner, the source depletion for the synthesis of these materials leads the researchers to find new and cost-effective solutions. Today's studies show that biomass provides a real ocean to overcome this problem with many advantages. Especially supercapacitors need reliable modifications in which biomass derived carbon based materials play a crucial role. After extensive investigations biomass is found to be capable of the synthesis of highly porous carbon materials with low/no-cost and eternal precursor supplementary. At this point it has to be underlined that these methods not only provide a way to produce high-value added materials but also contribute to the recycling of the wastes with the win-win principle. The reported studies prove the developed biomass derived materials enhance electrochemical adhesion of the ions which leads to increased specific capacitance of the electrode, consecutively cycling ability and stability of the supercapacitor is enhanced. The crucial points in the biomass derived production are indicated as the choice of the biomass, synthesis process, pretreatment, and the type of the supercapacitor. Among them precursor material and pretreatment play a key role because the pore size and distribution vary very much depending on the precursor content and the pretreatment process. Heteroatom doping to the biomass derived materials add extremely high conductivity to the ordinary materials so the composite materials are preferred in many supercapacitor applications. However, because of the biomass derived synthesis is a green synthesis method the researchers avoid to exaggerated hazardous chemical pretreatments, instead they should choose the right precursor biomass material that has this feature in itself that is reported in this study as well. Overall, biomass is a very valuable source for the synthesis of the next generation of low-cost and green electrode materials for supercapacitors, fuel cells, batteries, and all electrochemical transducers.

#### **Conflict of interest**

The authors declare no conflict of interest.

*Supercapacitors for the Next Generation*

#### **Author details**

Sema Aslan1 and Derya Bal Altuntaş2 \*

1 Department of Chemistry, Faculty of Science, Mugla Sitki Kocman University, Mugla, Turkey

2 Department of Bioengineering, Faculty of Architecture and Engineering, Recep Tayyip Erdogan University, Rize, Turkey

\*Address all correspondence to: derya.balaltuntas@erdogan.edu.tr

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Biomass Based Materials in Electrochemical Supercapacitor Applications DOI: http://dx.doi.org/10.5772/intechopen.98353*

#### **References**

[1] Yang F, Meerman JC, Faaij APC. Carbon capture and biomass in industry: A techno-economic analysis and comparison of negative emission options. Renewable and Sustainable Energy Reviews. 2021;144:111028. https://doi.org/10.1016/j.rser.2021. 111028

[2] Antar M, Lyu D, Nazari M, Shah A, Zhou X, Smith DL. Biomass for a sustainable bioeconomy: An overview of world biomass production and utilization. Renewable and Sustainable Energy Reviews. 2021;139:110691. https://doi.org/10.1016/j. rser.2020.110691.

[3] Chen WH, Lin BJ, Lin YY, Chu YS, Ubando AT, Show PL, Ong HC, Chang J-S, Ho S-H, Culaba AB, Pétrissans A, Pétrissans M. Progress in biomass torrefaction: Principles, applications and challenges. Progress in Energy and Combustion Science. 2021;82:100887. https://doi.org/10.1016/j.pecs.2020. 100887

[4] Bastida F, Eldridge DJ, García C, Png GK, Bardgett RD, Delgado-Baquerizo M. Soil microbial diversity– biomass relationships are driven by soil carbon content across global biomes. The ISME Journal. 2021;1-11. doi: 10.1038/s41396-021-00906-0.

[5] Di Blasi C. Modeling chemical and physical processes of wood and biomass pyrolysis. Progress in energy and combustion science. 2008;34(1):47-90. https://doi.org/10.1016/j.pecs.2006. 12.001

[6] Vassilev SV, Vassileva CG, Vassilev VS. (). Advantages and disadvantages of composition and properties of biomass in comparison with coal: An overview. Fuel. 2015;158:330-350. https://doi. org/10.1016/j.fuel.2015.05.050

[7] Hoa LQ, Vestergaard MDC, Tamiya E. Carbon-based nanomaterials in biomass-based fuel-fed fuel cells. Sensors. 2017;17(11):2587. doi: 10.3390/ s17112587.

[8] Tan Z, Yang J, Liang Y, Zheng M, Hu H, Dong H, Liu Y, Xiao Y. The changing structure by component: Biomass-based porous carbon for high-performance supercapacitors. Journal of Colloid and Interface Science. 2021;585:778-786. https://doi. org/10.1016/j.jcis.2020.10.058

[9] Arunachellan IC, Sypu VS, Kera NH, Pillay K, Maity A. Flower-like structures of carbonaceous nanomaterials obtained from biomass for the treatment of copper ion-containing water and their re-use in organic transformations. Journal of Environmental Chemical Engineering. 2021;9(4):105242. https:// doi.org/10.1016/j.jece.2021.105242

[10] Gogotsi Y. Nanomaterials handbook. 2nd ed. CRC press; 2017. 712 p. ISBN 9781498703062

[11] Ozin GA, Arsenault A, Cademartiri L. Nanochemistry: a chemical approach to nanomaterials. 2nd ed. Royal Society of Chemistry; 2015. 978-1-84755-895-4

[12] dos Reis GS, de Oliveira H, Larsson SH, Thyrel M, Claudio Lima E. A Short Review on the Electrochemical Performance of Hierarchical and Nitrogen-Doped Activated Biocarbon-Based Electrodes for Supercapacitors. Nanomaterials. 2021;11:424. DOI: 10.3390/nano11020424

[13] Zhang LL, Zhao XS. Carbon-based materials as supercapacitor electrodes. Chemical Society Reviews, 2009;38(9):2520-2531. https://doi. org/10.1039/B813846J

[14] Wang J, Kaskel S. KOH activation of carbon-based materials for energy

storage. Journal of Materials Chemistry. 2012;22(45):23710-23725. https://doi. org/10.1039/C2JM34066F

[15] Wang T, Zang X, Wang X, Gu X, Shao Q, Cao N. Recent advances in fluorine-doped/fluorinated carbonbased materials for supercapacitors. Energy Storage Materials. 2020;30:367- 384. https://doi.org/10.1016/j. ensm.2020.04.044

[16] Huang Y, Liang J, Chen Y. An overview of the applications of graphene-based materials in supercapacitors. Small. 2012;8(12):1805- 1834. http://dx.doi.org/10.1002/ smll.201102635

[17] Zhang LL, Zhou R, Zhao XS. Graphene-based materials as supercapacitor electrodes. Journal of Materials Chemistry, 2010;20(29):5983- 5992. https://doi.org/10.1039/C000417K

[18] He Y, Wang L, Jia D, Zhao Z, Qiu J. NiWO4/Ni/Carbon composite fibres for supercapacitors with excellent cycling performance. Electrochimica Acta. 2016;222:446-454. DOI: 10.1016/j. electacta.2016.10.197

[19] Bal Altuntaş D, Aslan S, Akyol Y, Nevruzoğlu V. Synthesis of new carbon material produced from human hair and its evaluation as electrochemical supercapacitor. Energy Sources Part A-Recovery Utilization And Environmental Effects. 2020;42:2346- 2356. https://doi.org/10.1080/15567036. 2020.1782536

[20] Bal Altuntaş D, Nevruzoğlu V, Dokumacı M, Cam Ş. Synthesis and characterization of activated carbon produced from waste human hair mass using chemical activation. Carbon Letters. 2020;30:307-313. http://dx.doi. org/10.1007/s42823-019-00099-9

[21] Bal Altuntas D, Akgul G, Yanık J, Anık Ü. A biochar-modified carbon paste electrode. Turkish Journal of

Chemistry. 2017;41:455-465. doi:10.3906/kim-1610-8

[22] Bal Altuntaş D, Nevruzoğlu V. Evaluation of waste human hair as graphene oxide and examination of some characteristics properties. El-Cezerî Journal of Science and Engineering. 2020;7:104-110. 2020 https://doi.org/10.31202/ecjse.594819

[23] Long, W., Fang, B., Ignaszak, A., Wu, Z., Wang, Y. J., & Wilkinson, D. (2017). Biomass-derived nanostructured carbons and their composites as anode materials for lithium ion batteries. Chemical society reviews, 46(23), 7176-7190. https://doi. org/10.1039/C6CS00639F

[24] Wang, J., Nie, P., Ding, B., Dong, S., Hao, X., Dou, H., & Zhang, X. (2017). Biomass derived carbon for energy storage devices. Journal of materials chemistry a, 5(6), 2411-2428. https:// doi.org/10.1039/C6TA08742F

[25] Wang Z, Shen D, Wu C, Gu S. State-of-the-art on the production and application of carbon nanomaterials from biomass. Green Chemistry. 2018;20(22):5031-5057. https://doi. org/10.1039/C8GC01748D

[26] Ellabban O, Abu-Rub H, Blaabjerg F. Renewable energy resources: Current status, future prospects and their enabling technology. Renewable and Sustainable Energy Reviews. 2014;39:748-764. https://doi. org/10.1016/j.rser.2014.07.113

[27] Ibrahim H, Ilinca A, Perron J. Energy storage systems— Characteristics and comparisons. Renewable and sustainable energy reviews. 2008;12(5):1221-1250. https:// doi.org/10.1016/j.rser.2007.01.023

[28] Zhang S, Pan, N. Supercapacitors performance evaluation. Advanced Energy Materials. 2015;5(6):1401401. DOI: 10.1002/aenm.201401401

*Biomass Based Materials in Electrochemical Supercapacitor Applications DOI: http://dx.doi.org/10.5772/intechopen.98353*

[29] Frackowiak E, Metenier K, Bertagna V, Beguin F. Supercapacitor electrodes from multiwalled carbon nanotubes. Applied Physics Letters. 2000;77(15):2421-2423. https://doi. org/10.1063/1.1290146

[30] Kim J, Lee J, You J, Park MS, Al Hossain MS, Yamauchi Y, Kim JH. Conductive polymers for nextgeneration energy storage systems: recent progress and new functions. Materials Horizons. 2016;3(6):517-535. https://doi.org/10.1039/C6MH00165C

[31] Aslan S, Bal Altuntaş D, Koçak Ç, Kara Subaşat H. Electrochemical evaluation of Titanium (IV) Oxide/ Polyacrylonitrile electrospun discharged battery coals as supercapacitor electrodes. Electroanalysis. 2021;33:120- 128. DOI: 10.1002/elan.202060239

[32] Xu B, Yue S, Sui Z, Zhang X, Hou S, Cao G, Yang Y. What is the choice for supercapacitors: graphene or graphene oxide?. Energy & Environmental Science. 2011;4(8):2826-2830. DOI: 10.1039/c1ee01198g

[33] Singh PK, Das AK, Hatui G, Nayak GC. Shape controlled green synthesis of CuO nanoparticles through ultrasonic assisted electrochemical discharge process and its application for supercapacitor. Materials Chemistry and Physics. 2017;198:16-34. ISSN 0254- 0584, https://doi.org/10.1016/j. matchemphys.2017.04.070.

[34] Bose S, Kuila T, Mishra AK, Rajasekar R, Kim NH, Lee JH. (). Carbon-based nanostructured materials and their composites as supercapacitor electrodes. Journal of Materials Chemistry. 2012;22(3):767-784. https:// doi.org/10.1039/C1JM14468E

[35] Rivera-Cárcamo C, Serp P. Single atom catalysts on carbon-based materials. ChemCatChem. 2018;10(22):5058-5091. https://doi. org/10.1002/cctc.201801174

[36] Senthil RA, Yang V, Pan J, Sun Y. A green and economical approach to derive biomass porous carbon from freely available feather finger grass flower for advanced symmetric supercapacitors. Journal of Energy Storage. 2021;35:102287. https://doi. org/10.1016/j.est.2021.102287

[37] Zheng LH, Chen MH, Liang SX, Lü QF. Oxygen-rich hierarchical porous carbon derived from biomass wastekapok flower for supercapacitor electrode. Diamond and Related Materials. 2021;113:108267. https://doi. org/10.1016/j.diamond.2021.108267

[38] Jain A, Ghosh M, Krajewski M, Kurungot S, Michalska M. Biomassderived activated carbon material from native European deciduous trees as an inexpensive and sustainable energy material for supercapacitor application. Journal of Energy Storage. 2021;34:102178. https://doi. org/10.1016/j.est.2020.102178

[39] Nguyen NT, Le PA, Phung VBT. Biomass-derived carbon hooks on Ni foam with free binder for high performance supercapacitor electrode. Chemical Engineering Science. 2021;229:116053. https://doi. org/10.1016/j.ces.2020.116053

[40] Long S, Feng Y, He F, Zhao J, Bai T, Lin H, Cai W, Mao C, Chen Y, Gan L, Liu J, Ye M, Zeng X, Long M. Biomassderived, multifunctional and wavelayered carbon aerogels toward wearable pressure sensors, supercapacitors and triboelectric nanogenerators. Nano Energy. 2021;85:105973. https://doi. org/10.1016/j.nanoen.2021.105973

[41] Wu Y, Cao J-P, Zhuang Q-Q, Zhao X-Y, Zhou Z, Wei Y-L, Zhao M, Bai H-C. Biomass-derived three-dimensional hierarchical porous carbon network for symmetric supercapacitors with ultrahigh energy density in ionic liquid electrolyte, Electrochimica Acta.

2021;371:137825. https://doi. org/10.1016/j.electacta.2021.137825.

[42] Fang C, Hu P, Dong S, Cheng Y, Zhang D, Zhang X. Construction of carbon nanorods supported hydrothermal carbon and carbon fiber from waste biomass straw for high strength supercapacitor. Journal of Colloid and Interface Science. 2021;582:552-560. https://doi. org/10.1016/j.jcis.2020.07.139

[43] Ba H, Wang W, Pronkin S, Romero T, Baaziz W, Nguyen-Dinh L, Chu W, Ersen O, Huu CP. Biosourced foam-like activated carbon materials as high-performance supercapacitors. Adv Sustain Syst. 2018;2:1700123. https:// doi.org/10.1002/adsu.201700123

[44] Wang B, Ji L, Yu Y, Wang N, Wang J, Zhao J. A simple and universal method for preparing N, S co-doped biomass derived carbon with superior performance in supercapacitors. Electrochim Acta. 2019;309:34-43. https://doi.org/10.1016/j. electacta.2019.04.087

[45] Liu Y, Yu W, Hou L, He G, Zhu Z. Co3O4@Highly ordered macroporous carbon derived from a mollusc shell for supercapacitors. RSC Adv 2015;5:75105- 75110. DOI: 10.1039/C5RA15024H

[46] Xiong W, Gao Y, Wu X, Hu X, Lan D, Chen Y, Pu X, Zeng Y, Su J, Zhu Z. Composite of macroporous carbon with honeycomb-like structure from mollusc shell and NiCo(2)O(4) nanowires for high-performance supercapacitor. ACS Appl Mater Interfaces. 2014;6:19416-19423. https:// doi.org/10.1021/am5055228

[47] Lai F, Miao YE, Zuo L, Lu H, Huang Y, Liu T. Biomass-derived nitrogen-doped carbon nanofiber network: a facile template for decoration of ultrathin nickelcobalt layered double hydroxide nanosheets as highperformance asymmetric supercapacitor electrode. Small. 2016;12:3235-3244. https://doi.org/10.1002/smll.201600412

[48] Ghosh S, Santhosh R, Jeniffer S, Raghavan V, Jacob G, Nanaji K, Kollu P, Jeong SK, Grace AN. Natural biomass derived hard carbon and activated carbons as electrochemical supercapacitor electrodes. Sci Rep. 2019;9:1-15. https://doi.org/10.1038/ s41598-019-52006-x.

[49] Shang T, Xu Y, Li P, Han J, Wu Z, Tao Y, Yang QH. A bioderived sheet-like porous carbon with thin-layer pore walls for ultrahigh-power supercapacitors. Nanomater Energy. 2020;70:104531. https://doi.org/10.1016/j. nanoen.2020.104531.

[50] He J, Zhang D, Wang Y, Zhang J, Yang B, Shi H, Wang K, Wang Y. Biomass-derived porous carbons with tailored graphitization degree and pore size distribution for supercapacitors with ultra-high rate capability. Appl Surf Sci. 2020;515:146020. https://doi. org/10.1016/j.apsusc.2020.146020.

[51] Selvaraj AR, Muthusamy A, Kim HJ, Senthil K, Prabakar K. Ultrahigh surface area biomass derived 3D hierarchical porous carbon nanosheet electrodes for high energy density supercapacitors. Carbon. 2021;174:463-474. https://doi. org/10.1016/j.carbon.2020.12.052

[52] Cao X, Li Z, Chen H, Zhang C, Zhang Y, Gu C, Xu X, Li Q. Synthesis of biomass porous carbon materials from bean sprouts for hydrogen evolution reaction electrocatalysis and supercapacitor electrode. International Journal of Hydrogen Energy. https://doi. org/10.1016/j.ijhydene.2021.03.038

[53] Yakaboylu GA, Jiang C, Yumak T, Zondlo JW, Wang J, Sabolsky EM. Engineered hierarchical porous carbons for supercapacitor applications through chemical pretreatment and activation of biomass precursors. Renewable

*Biomass Based Materials in Electrochemical Supercapacitor Applications DOI: http://dx.doi.org/10.5772/intechopen.98353*

Energy.2021;163:276-287. https://doi. org/10.1016/j.renene.2020.08.092

[54] Chaparro-Garnica J, Salinas-Torres D, Mostazo-López MJ, Morallón E, Cazorla-Amorós D. Biomass waste conversion into low-cost carbonbased materials for supercapacitors: A sustainable approach for the energy scenario. Journal of Electroanalytical Chemistry. 2021;880:114899. http:// dx.doi.org/10.1016/j.jelechem.2020. 114899

[55] Liang X, Liu R, Wu X. Biomass waste derived functionalized hierarchical porous carbon with high gravimetric and volumetric capacitances for supercapacitors. Microporous and Mesoporous Materials. 2021;310:110659. https://doi.org/10.1016/j. micromeso.2020.110659

[56] Du J, Zhang Y, Lv H, Chen A. Silicate-assisted activation of biomass towards N-doped porous carbon sheets for supercapacitors. Journal of Alloys and Compounds. 2021;853:157091. https://doi.org/10.1016/j.jallcom.2020. 157091

[57] Ariharan A, Ramesh K, Vinayagamoorthi R, Rani MS, Viswanathan B, Ramaprabhu S, Nandhakumar V. Biomass derived phosphorous containing porous carbon material for hydrogen storage and high-performance supercapacitor applications. Journal of Energy Storage. 2021;35:102185. https://doi. org/10.1016/j.est.2020.102185

[58] Ramanathan S, Sasikumar M, Paul SPM, Obadiah A, Angamuthu A, Santhoshkumar P, Raj D, Vasanthkumar S. Low cost electrochemical composite material of paper cup waste carbon (P-carbon) and Fluorescein for supercapacitor application. Materials Today: Proceedings. https://doi.org/10.1016/j. matpr.2020.12.561

[59] Xie X, Zhang B, Wang Q, Zhao X, Wu D, Wu H, Sun X, Hou C, Yang X, Yu R, Zhang S, Murugadoss V, Du W. Efficient microwave absorber and supercapacitors derived from puffedrice-based biomass carbon: Effects of activating temperature. Journal of Colloid and Interface Science. 2021;594:290-303. https://doi. org/10.1016/j.jcis.2021.03.025

[60] Ajay KM, Dinesh MN, Byatarayappa G, Radhika MG, Kathyayini N, Vijeth H. Electrochemical investigations on low cost KOH activated carbon derived from orange-peel and polyaniline for hybrid supercapacitors. Inorganic Chemistry Communications. 2021;127:108523. https://doi. org/10.1016/j.inoche.2021.108523

[61] Gehrke V, Maron GK, da Silva Rodrigues L, Alano JH, de Pereira CMP, Orlandi MO, Carreño NLV. Facile preparation of a novel biomass-derived H3PO4 and Mn (NO₃)₂ activated carbon from citrus bergamia peels for highperformance supercapacitors. Materials Today Communications. 2021;26:101779. https://doi.org/10.1016/j.mtcomm. 2020.101779

[62] Avinash B, Ravikumar CR, Kumar MA, Santosh MS, Pratapkumar C, Nagaswarupa HP, Ananda Murthy HC, Deshmukh VV, Bhatt Aarti S, Jahagirdar AA, Alam MW. NiO biocomposite materials: Photocatalytic, electrochemical and supercapacitor applications. Applied Surface Science Advances. 2021;3:100049. https://doi. org/10.1016/j.apsadv.2020.100049

[63] He D, Gao Y, Wang Z, Yao Y, Wu L, Zhang J, Huang Z-H, Wang MX. One-step green fabrication of hierarchically porous hollow carbon nanospheres (HCNSs) from raw biomass: Formation mechanisms and supercapacitor applications. Journal of Colloid and Interface Science. 2021;581:238-250. https://doi. org/10.1016/j.jcis.2020.07.118

Section 3
