439 Indonesian Journal of Science & Technology 8. 439-468 Indonesian Journal of Science & Technology Journal homepage: http://ejournal. edu/index. php/ijost/ Biomass-Based Supercapacitors Electrodes for Electrical Energy Storage Systems Activated Using Chemical Activation Method: A Literature Review and Bibliometric Analysis Ida Hamidah1,*. Ramdhani Ramdhani1. Apri Wiyono1. Budi Mulyanti1. Roer Eka Pawinanto1. Lilik Hasanah1. Markus Diantoro2. Brian Yuliarto3. Jumril Yunas4. Andrivo Rusydi5 Universitas Pendidikan Indonesia. Jl. Dr. Setiabudhi 229. Bandung, 40154. Indonesia Universitas Negeri Malang. Jl. Semarang 5. Malang, 65145. Indonesia Institut Teknologi Bandung. Jl. Tamansari 10. Bandung 40132. Indonesia Universiti Kebangsaan Malaysia. Bangi, 43600. Selangor. Malaysia National University of Singapore. Queenstown. Singapore Correspondence: E-mail: idahamidah@upi. ABSTRACT Currently, carbon derived from biomass waste or residues is being intensively utilized as electrodes due to its excellent electrical properties, including high conductivity, appropriate porosity, and a specific surface area suitable for supercapacitor applications. Despite its advantages, the performance of supercapacitors made from biomass-derived carbon is insufficient for engineering applications because of the challenges in obtaining the mesoporous structure of activated carbon (AC). Therefore, this study highlights the potential of biomass-based carbon as the electrodes of a highly efficient supercapacitor, which can facilitate highly efficient current transport in energy storage systems. It comprehensively discusses various biomass material sources and activation methods to produce carbon, with a focus on the physical and electrical properties. Initially, the study discusses carbon activation methods and mechanisms to understand why activating agents and electrolyte solutions have a high specific surface area and specific capacitance. It then concentrates on the chemical activation method and its importance in making AC useful as an efficient electrode. Finally, in this study, various biomass sources were discussed to highlight the performance of supercapacitors electrodes originating from agricultural and wood residues relating to the specific capacitance and capacitance Based on the obtained results, it is concluded that biomassbased carbon materials could be the most advantageous platform material for energy conversion and storage. A 2023 Tim Pengembang Jurnal UPI ARTICLE INFO Article History: Submitted/Received 01 Apr 2023 First Revised 12 May 2023 Accepted 18 Jul 2023 First available online 21 Jul 2023 Publication Date 01 Dec 2023 ____________________ Keyword: Activated carbon. Biomass. Chemical activation. Energy storage. Specific capacitance. Supercapacitors. Hamidah et al. Biomass-Based Supercapacitors Electrodes for Electrical Energy Storage SystemsA | 440 INTRODUCTION In the past, there was a growing concern that fossil fuel reserves would eventually run out at some point (Kong et al. , 2020. Maheshvari, 2022. Haritha, 2. This has prompted efforts toward reducing the rate at which these fuels are widely consumed. One approach towards achieving this has been to explore alternative energy sources, such as hydrogen combustion gas in car engines (Hamidah et al. , 2. and electric-powered vehicles (Cano et al. , 2. To facilitate this transition towards renewable energy sources, machines, and other electrical devices have been designed to align with technological advancements and innovative Electricity can be generated by converting different types of energy, such as photon energy (Liu et al. , 2. , mechanical rotation and vibration energy (Said et al. , 2016. Yunas et al. , 2. , heat energy transfer from waste (Seralathan et al. , 2020. Tian et al. , 2. electrochemical power generator in fuel cells (Zhang et al. , 2021. Qiu et al. , 2. , and energy capture from environmental electromagnetic pollution (Surducan et al. Shi et al. , 2. One significant breakthrough in the shift towards renewable energy sources is the fast development of electric vehicles, and this coincides with the development of various energy storage technologies such as sodiumion, zinc-air, lithium-ion, and aluminum-air batteries (Chuhadiya et al. , 2021. Sellali et al. Meanwhile, supercapacitors are expected to have a comparative advantage over batteries, making them a promising alternative for energy storage systems that play a significant key in preparing a continuous power supply for portable mobile electronic equipment (VukajloviN et al. However, batteries/supercapacitors were employed in electric vehicles because of their high energy density (Zhang et al. , 2020. Rahman et al. , while a voltage stabilizer is added to the automobile to stabilize power consumption (Hamidah et al. , 2. To meet the requirements of the automobile industry, energy storage applications must be highly efficient, cost-effective, compact, and produce low harmful exhaust gas (Zou et al. Furthermore, with the increasing need for high-performance energy storage devices in compact and highly mobile applications, such as the use of implanted biomedical devices (Veneri et al. , 2018. Seman et al. , 2. and aerospace applications (Pan et al. , 2014. Xu et al. , 2. the demand for compact and highperformance energy storage devices grows The energy storage system itself is critical generation problems and improving stability in electrical devices. Electric vehicles require kinetic energy storage when accelerating and recharging using electricity. To meet the supply and demand, electrochemical capacitors and batteries are among the most efficient energy storage systems (Sellai et al. Veneri et al. , 2. However, both have limitations. Batteries have a higher energy density than supercapacitors, whereas electrochemical capacitors can be charged and discharged in a matter of seconds but have a lower energy density than Lithium-ion batteries (Seman et al. Pan et al. , 2. Supercapacitors are emerging as one of the most promising candidates for batteries due to their improved performance and reduced costs. However, improvements in energy storage systems are necessary to address the increasing demand in the need for future energy systems, including hybrid electric vehicles, electronic gadgets, and industrial equipment (Xu et al. Improving the electrode properties of supercapacitors is one of the most critical elements in enhancing its performance. Figure 1 shows detailed information regarding the charge transport mechanism of common supercapacitors electrodes. DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 441 | Indonesian Journal of Science & Technology. Volume 8 Issue 3. December 2023 Hal 439-468 employing Equation 1, enlarging the electrode's surface area permitted a significant boosting of the capacity of the capacitor and shortened the distance between electrodes. This can be achieved by using a material with a huge number of free electrons gathered on its surface (Karaphun et al. , 2. As a result, with careful electrode material selection and the use of simple and low-cost synthesis procedures, larger-scale commercial applications for supercapacitors can be developed (Ghosh et , 2. ya ya = yuAyc yuA0 ycc where Ar and A0 are, respectively, the permittivity of electrolyte and vacuum. d and A are the distance between two electrodes and the specific surface area, respectively. Many reports have been published concerning the utilization of carbon-based materials (Anshar et al. , 2016. NAodiaye, 2023. Ragadhita & Nandiyanto, 2023. Nandiyanto et al. , 2017. Nandiyanto, 2018. Sukmafitri et , 2020. Fiandini et al. , 2020. Anggraeni et , 2021. Nandiyanto et al. , 2022a. Nandiyanto et al. , 2022. It has been applied as electrodes, especially for improving energy storage systems. These materials were selected because of their distinct properties, which include tunable porosities (Zhao et al. , 2. , large surface areas (Duan et al. , 2. , varying morphologies (Chuhadiya et al. , 2. , layer-by-layer design (Nabais et al. , 2. , and the superior quality of their crystalline products (BoopathiRaja & Parthibavarman, 2. shown in Table 1, carbon-based material can consist of nanoparticles, carbon nanotubes. Figure 1. The schematic of the supercapacitors structure highlighting the role of carbonbased electrodes. DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 Hamidah et al. Biomass-Based Supercapacitors Electrodes for Electrical Energy Storage SystemsA | 442 Table 1. Carbon-based electrode materials and their potential applications. Materials Carbon Graphene Graphite Borondoped Diamond Physical 1 Dimensional porous flexible free-standing electrodes coat Twodimensional high optical and excellent Threedimensional Porosity range 22-28%, electrodes coat Chemical and Electrical Giant power factor, anodes for Ion transport requires the opening of 2D For rapid charge storage and low sheet resistance, the entire surface is Thick electrodes with substantial surface and volume storage capacities, low Semiconducting In addition to the aforementioned carbonbased electrode materials, biocarbon-based electrodes derived from biomass have attracted the most interest because of their potential as a source of green and sustainable energy (Saini et al. , 2. Biomass refers to organic compounds derived from plants, algae, and organic Accordingly, this compound has been identified as the electrode of a promising supercapacitor due to its abundance, recyclability, and eco-friendliness. The use of this biomass can also help reduce the volume of organic waste globally (Priya et al. , 2. In this regard, this review is structured to first discuss the carbon activation mechanism using chemical or physical activation The key elements of this topic include characterizing the carbon content of Applications Ref. Sensors, energy storage Pietrzak and Wardak . Kulakovskaya et . Zouli . Tefera et al. Sensors, nanomedicine, energy Salleh et al. , . and Wang . Bashir et al. Rahim et al. Bioelectrochemical systems, sensors Aval et al. Dai et . Kim et al. Flow injection systems. Retinal Liu et al. Dettlaff et al. Bogdanowicz et al. Wood et al. various biomass and their usefulness as electrodes for supercapacitors applications, as well as understanding chemical activation processes used to enhance the attributes of biomass-based electrodes. The second section of this review concentrates on various types of biomass sources that can be converted into value-added carbon products to serve as a critical component of supercapacitors electrodes. METHODS Presentation of the Study Area This paper is a literature survey. Data were obtained from internet sources, specifically, articles published in international journals. Data were collected and compiled to form Data were also compared to the current situation. To support analysis, we DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 443 | Indonesian Journal of Science & Technology. Volume 8 Issue 3. December 2023 Hal 439-468 also used VOS viewer. Detailed information for the use of VOSviewer is explained in previous studies (Azizah et al. , 2021. Husaeni & Nandiyanto, 2. RESULTS AND DISCUSSION The Structure and Charge Transfer Mechanism of Supercapacitors The structure of supercapacitors, as shown in Figure 1, consists of electrodes, electrolytes, electrolyte separators, and current collectors. The active component of supercapacitors is electrodes, as the charge within them is dependent on the type of electrode-active materials used. Therefore, electrodes should have high electrical conductivity, a large surface area, a mesoporous structure, and a standard electrode potential to perform redox activity. The power density of carbon is significantly influenced by its electrical conductivity, which is fully reliant on its morphology (Sharma & Kumar, 2. and because electrodes have a large surface area, electrolyte ions can easily diffuse through their pores, thereby improving their performance (Sun et al. , 2. Moreover, materials with a high porosity structure can store a large number of voids on the atomic, nanometer, or molecular scales and have tunable dimensions, enhancing their ability to interact with their environment (Hassan et , 2. It is also noteworthy that redox activity could be advantageous for supercapacitors with a high specific capacity (Lakraychi et al. , 2. , hence, selecting electrode-active materials is a prerequisite for optimal performance. During an electrochemical analysis, two primary forms of electrode characteristics exist, they are the Faradaic and non-Faradaic At electrodes, charge transfer occurs during the redox reaction in the Faradaic process, whereas in the nonFaradaic process, the charge is collected through induction (Fleischmann et al. , 2. The ionic and electronic charges should remain at or in electrodes, similar to the adsorption and desorption processes. NonFaradaic processes are exhibited by intercalation. Electric Double-Layer Capacitor (EDLC), and electrodes with redox-active surface functionalities (Bartzis & Sarris. In charge transfer electrodes, both Faradaic and non-Faradaic processes occur However, for supercapacitors to overwhelm the bottleneck of low energy density, a faradaic process must be implemented right away (Wei et al. , 2. this regard, synergistic interactions between redox-active electrolytes and binder-free functionalization are being explored to enhance the performance of supercapacitors (Mai et al. , 2013. Wang et al. , 2. Carbon Activation Mechanism and Method To make biomass material usable as electrodes in supercapacitors, carbon activation techniques are required to increase activated carbon (AC) surface area. AC synthesis consists of two fundamental steps, the include activation and carbonization (Ayinla et al. , 2019. Kleszyk et , 2. Carbonization is the process of reducing the volatile content of raw materials by pyrolyzing carbon raw materials/precursors, resulting in the production of AC with high fixed carbon content and primary porosity. Activation, on the other hand, is the process of increasing the specific surface area or pore volume of AC through the formation of new pore structures and the expansion of existing ones (Gao et al. , 2. From these two steps, activation is more important than carbonization in terms of AC properties, which is why increased emphasis has been placed on activation. Currently, three primary activation procedures are utilized to create AC . amely physical activatio. (Shrestha et al. , 2021. Ettish et al. , chemical activation (Duan et al. , 2021. Hu et al. , 2. , and physiochemical activation (Tobi et al. , 2019. Fan et al. , 2. DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 Hamidah et al. Biomass-Based Supercapacitors Electrodes for Electrical Energy Storage SystemsA | 444 Figure 2 illustrates the use of biomassderived environmental purposes. Initially, pyrolysis and hydrothermal carbonization were the Hydrothermal carbonization is a thermochemical process that converts biomass into carbon, while pyrolysis is carried out in a low-oxygen or inert atmosphere at a set temperature. Chemical and physical processes can then be used to convert biomass into value-added carbon products, with the resulting carbon materials being affected by chemical, surface properties, time, and availability (Thomas et , 2019. Anggraeni et al. , 2022a. Anggraeni et al. , 2022. Pyrolysis Pyrolysis is a process that occurs in an oxygen-free, inert environment at a specific temperature, and the biomass of its products is determined by the feedstock, an activation reagent catalyst, a temperature controller, and the AC impregnation ratio (Zhang et al. Pebrianti & Salamah, 2. The AC derived through pyrolysis of biomass usually results in more micropore structures, which has large pore volume and a substantial specific surface area (Fu et al. , 2. Carbon nanofibers, for instance, can be produced by solar pyrolysis of pinewood and exhibit a substantial specific surface area and a rich microstructure as binder-free electrodes, which is critical to their electrochemical performance relating to specific capacitance (Wang et al. , 2. Furthermore, a study found that CoMoO4 electrodes for lithiumion batteries and supercapacitors could be efficiently prepared through a polymerpyrolysis method. These electrodes have been found to have a high specific capacitance and capacity retention (Wang et , 2. Figure 2. The schematic overview of AC originating from biomass for energy and environment applications. DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 445 | Indonesian Journal of Science & Technology. Volume 8 Issue 3. December 2023 Hal 439-468 Hydrothermal carbonization Hydrothermal carbonization (HTC) is a thermochemical process (Nandiyanto, 2. It turns biomass into carbon with or without the presence of a catalyst. This process takes place in environments with temperatures within the range of 120 and 250 AC (Wang et , 2. The resulting materials from hydrothermal carbonization typically have a low specific surface area and contain functional groups that are good for To preserve some functional groups while increasing the surface area of these materials, higher-temperature steam activation was employed (Beri et al. , 2. Similarly, it was concluded in another study that an increase in temperature and time during the hydrothermal carbonization process potentially permits an increase in the amount of carbon that is contained within the material (Wilk et al. , 2. Physical activation The physical activation of carbon involves a high-temperature pyrolysis process, typically between 400 and 1200CC (Wang et , 2. This type of activation is less complicated and more environmentally friendly than chemical activation. Also, activating agents commonly used in this activation method include CO2, steam, and air (Mai et al. , 2. Physical activation can be combined with pyrolysis to create a costeffective and advantageous activation method for biomass materials. The combination of these two methods causes or contributes to the development of high porosity and larger surface area (Lima et al. It is also important to note that AC can be increased by raising the temperature of activating agents (Mopoung & Dejang, 2. Chemical activation Chemical activation requires less activation time and temperature than physical activation. In a single phase, which is a combination of carbonization and activation, chemical activation makes it possible to produce porous carbon with large surface areas. This ultimately results in a lower energy requirement for the process (Mayoral et al. , 2. It has also been proven that chemical activation can boost carbon material capacitance (Xiong et al. , 2. Chemical activation has two activation steps, they are one-step and two-step activation, which are for the activation of acid-activating agents and, alkaline and neutral activating agents respectively. The activating agent is chemically impregnated into the precursor, and the mixture is then heated to the desired Regarding the two-step activation, the first step involves carbonizing the precursor at 300-600AC to produce charcoal, which is then mixed with activating agent and heated to a temperature ranging from 400 to 900AC (Oginni et al. , 2. It is important to note that the long heating time and manufacturing process of the two-step activation necessitates the requirement for a lot of energy. However, the most important benefit of this activation method is that it results in a high specific surface area (Heimbyckel et al. , 2. Physiochemical activation The activation process is carried out either physically, chemically, or through a combination of the two processes, called the physiochemical method (Ayinla et al. , 2019. Tobi et al. , 2. Although it costs more and takes longer to prepare, this method is very popular due to its ability to create highquality AC with increased surface area (Din. The process involves carbonization at high temperatures ranging from 600 to 850AC and activation with chemical activating agents . KOH and NaOH) (Erabee et al. In addition to producing high-quality AC, physiochemical activation can also be used to remove pollutants such as Zn(II) from the surface area of AC (Latiff et al, 2. This process also increases the volume of the mesopore and the surface area of carbon. Table 2 outlines the summaries of the carbon DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 Hamidah et al. Biomass-Based Supercapacitors Electrodes for Electrical Energy Storage SystemsA | 446 their research, as discussed in previous studies advantages and disadvantages. (Nandiyanto et al. , 2020. Hamidah et al. From the analysis of the advantages and 2020. Ramadhan et al. , 2022. Shidiq, 2023. disadvantages of all methods for carbon Nandiyanto et al. , 2024. Ragadhita & activation, the chemical activation method Nandiyanto, 2022. Nugraha & Nandiyanto, was found to be of particular interest for 2022. Fauziah & Nandiyanto, 2022. Pramanik further study and this is because it offers a & Rahmanita, 2023. Wirzal & Putra, 2022. simple, cost-efficient, controlled, and stable Husaeni et al. , 2023. Nordin, 2022. Following this point. Hu et al. Husaeni et al. , 2023. Mulyawati & reported that this method was successfully Ramadhan, 2021. Al Husaeni & Nandiyanto, utilized to produce AC with a large surface 2023. Hofifah & Nandiyanto, 2024. area from biomass-based sources like Nandiyanto et al. , 2023. Ruzmetov & coconut shells (Hu et al. , 1. The Ibragimov, 2023. Nordin, 2022. Bilad, 2022. correlation between AC from biomass using Sudarjat, 2023. Nursaniah & Nandiyanto, the chemical activation method for 2023. Al Husaeni, 2023. Firdaus et al. , 2023. supercapacitors applications has been Nandiyanto et al. , 2021. Wiendartun et al. thoroughly analyzed using Vosviewer. The 2022. Solehuddin et al. , 2023. Sukyadi et al. analysis results from 8,403 articles sourced 2. from the Scopus database . ata taken by Apr The strong correlation between biomass, 12 , 2. show a strong correlation supercapacitors. AC, and chemical activation between biomass, supercapacitors. AC, and strengthens the hypothesis that a more inchemical activation (Figure . This depth analysis of the relationship between bibliometric analysis gives additional these four variables is needed. information regarding current trend Table 2. The advantages and disadvantages of the activation method. Method Physical Activation Advantages Clean and green production without any secondary waste Chemical Activation An effective way for increasing the capacitance of carbon characterized by a low activation temperature, a short processing time, an increasing carbon yield, a broad surface area that is well dispersed and formed microporous structure, wellcontrolled porosity, and better control of the textural properties. Can create AC of superior quality with a greater surface Physiochemical Activation Disadvantages Low specific surface area, high activation temperature, low carbon yield, and long processing time The drastic corrosively and inevitable washing process Ref Wang et al. Mopoung and Dejang . Ettish et al. Taer et al. Yi et al. Gao et al. Xiong et al. Kanjana et al. Bhandari and Gogate . Kanjana et al. Yakaboylu et . Sundriyal et al. , . Higher cost, longer preparation time, higher higher emission of heavy metals. Mai et al. Din et al. Ao et al. Rawat et al. DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 447 | Indonesian Journal of Science & Technology. Volume 8 Issue 3. December 2023 Hal 439-468 Figure 3. The correlation between biomass, supercapacitors. AC, and chemical activation. Evaluation of The Electrochemical Performance Carbon-Based Supercapacitors Made from Different Sources of Biomass Carbon materials derived from biomass are the highest-performing electrode materials for a variety of applications. These materials are particularly well-suited for use as effective electrodes in supercapacitors due to their ease of activation with chemical and their ability to be produced in large quantities at low cost. There are five categories of biomass sources, including . agricultural biomass, . urban and industrial waste, . aquatic biomass, . livestock waste, and . wood and woody biomass. However, the focus of this study is on agricultural biomass as well as wood and woody biomass sources, which can be considered sustainable sources of raw materials for biochar manufacture and their use in supercapacitors. Agricultural biomass refers to biomass obtained from agricultural products such as fruits, vegetables, and parts of the plant itself such as leaves, flowers, and flower petals. Many research regarding agriculture has been well-documented (Permatasari et al. Ragadhita et al. , 2023. Bhosale, 2. It can be further classified into two categories namely agriculture residues/wastes and energy crops (Yadav et al. , 2. Agriculture residues consist of basic byproducts such as cornstalk and rice straw, as well as secondary by-products from biomass processing like coffee husk, rice husk, and sugarcane bagasse. Energy crops include poplars, willows, eucalyptus, sugarcane, sorghum, artichokes, rapeseed, and sunflowers, which are produced specifically for biofuel and bioproduct production. Meanwhile, wood and woody biomass are derived from plant residues such as twigs, powder, and dried leaves. Before plant wastes can be used as electrodes in supercapacitors, they first have to be chemically activated to create pore sizes ranging from micropores to mesopores. Several studies have been conducted on the two types of biomass and their suitability for use in supercapacitors. The properties of these materials are listed in Table 3. DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 Hamidah et al. Biomass-Based Supercapacitors Electrodes for Electrical Energy Storage SystemsA | 448 Table 3. The characteristics of supercapacitors derived from biomass sources of agricultural. Activating Agent KOH Electrolyte in SC Aqueous Electrical Properties SpC CR (%) (F/. KOH 1 M H2SO4 KOH 3 M KOH KOH, NaOH KOH 1 M KOH 2 M KOH Banana Stem Fibers Beer Leaves ZnCl2 H2SO4 KOH 1 M ya2 SO4 Carrot ZnCl2 6 M KOH Celtuse Leaves* Cinnamon Sticks Cinnamon Sticks Cinnamon Sticks Coffee Grounds Corncob* KOH 6 M KOH KOH** NaClO4 in EC/ DMC ycAycayaycoycC4 in EC/ DMC ycAycayaycoycC4 in EC/ DMC BMIMBF4/AN KOH H2SO4*** Corncob KOH 6 M KOH*** 91 after Cornstalk KCl and NaCl H2SO4*** Corn Stalk KOH 6 M KOH*** Cotton Stalk KOH 4 M KOH Elm Samara* Ficus Religiosa Leaves Garlic Skin* KOH 6 M KOH PVA-H2 PO4 KOH 6M KOH >2000 KOH 6M KOH 92 after Biomass Source Aloe vera* Arenga Pinnata Bamboo Fibers* Bamboo Shoots* Banana Peel Garlic Seedling Chemical Solution ZnCl2** H3 PO4** KOH Physical Properties Ref. SSA eaya /yeO) 8 1890 Karnan et al. Farma et al. Zequine et al. Chen et al. Tripathy et al. 09 Taer et al. Lee et al. Ahmed et al. Wang et al. Thangavel et Thangavel et Thangavel et 7 Yun et al. Wang et al. Pramanik et Wang et al. Cao et al. Tian et al. Chen et al. Senthilkumar and Selvan Zhang et al. Li et al. DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 449 | Indonesian Journal of Science & Technology. Volume 8 Issue 3. December 2023 Hal 439-468 Table 3 (Continu. The characteristics of supercapacitors derived from biomass sources of Activating Agent KOH Electrolyte in SC 3 M KOH Electrical Properties SpC CR (%) (F/. Lacquer Wood H3PO4 1 m H2 SO4 Litchi Shell KOH 6 M KOH Lotus Leaf KOH 6 M KOH Mangosteen NaOH KOH Miscanthus Grass KOH KOH Onion KOH 6M KOH Onion Leaves Orange Peel* Palm Kernel Shell Pattail Peanut Shell KOH 3 M KOH Biomass Source Jute Fibers* Chemical Solution Physical Properties SSA . eaya /yeO) Ref. Zequine et al. Hu et al. Zhao et al. Qu et al. Yang et al. Yakaboylu et Thangavel et 80 after 92 after Yu et al. KOH KOH 1 M KOH NaCl NaOH 6 M KOH Perilla Frutescenes Pine Pollencone KOH 6 M KOH 80 after Ranaweera et Misnon et al. Yu et al. Zhan et al. 1 M ycAyca2 SO4 Pine Tree Powder Pistachios Nutshell Rice Husk KOH IL EMIMBF4 KOH 6 M KOH KOH 6 M KOH 5 Ae Rice Straws KOH 6 M KOH 95 after Liu et al. Hor and Hashmi . Wang et al. Xu et al. Liu et al. Divya & Rajalakshmi . DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 Hamidah et al. Biomass-Based Supercapacitors Electrodes for Electrical Energy Storage SystemsA | 450 Table 3 (Continu. The characteristics of supercapacitors derived from biomass sources of Activating Agent KOH, NaOH. Na2CO3 Electrolyte in SC 1 M LiOH Electrical Properties SpC CR (%) (F/. 1 M H2 SO4 325,046 Znyayco2 6 M KOH Syzygium Oleana Leaves Tamarind Fruit Shell* Tea Leaves KOH 1 M H2SO4 Taer et al. KOH H2SO4 KOH 2M KOH Tea-Waste KOH 6 M KOH Green TeaWaste Tobacco Rods KOH H2SO4 Senthilkumar et al. Peng et al. KOH 6 M KOH Walnut Shell ya2 CO3 1 M KOH Wood Carbon Monolith 2 M KOH Biomass Source Sisal Leaves Solanum Lycoperium Leaves Soybean Pods Chemical Solution Physical Properties SSA . eaya /yeO) Ref. Li et al. Divya & Rajalakshmi . Liu et al. Khan et al. Sankar et al. Zhao et al. Xu et al. Liu et al. Note: SpC = specific capacitance. CR = capacitance retention. PD = pore diameter. SSA=specific surface area *Biomass that produces specific capacitance over 400 F/g. **Different activating agents applied to the same biomass *** Different electrolytes in SC applied to the same biomass Table 3 presents the physical and electrical characteristics of each type of biomass with various chemical solutions. Among the different activating agents. KOH is the most commonly used and has been found to produce better specific capacitance compared to other agents. Due to its environmental friendliness. KOH has also garnered a lot of interest as an activator, and the treatment with this substance results in porosity with a narrow pore size distribution (Li et al. , 2. Additionally, this activator has been shown to enhance specific surface area, specific capacitance, and specific energy (Zhan et al. , 2. Thangavel et al. demonstrated the effectiveness of DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 451 | Indonesian Journal of Science & Technology. Volume 8 Issue 3. December 2023 Hal 439-468 KOH in producing a high specific surface area when they AC from cinnamon sticks. The activation process using KOH calls for more intricate procedures, but the resulting structure is extremely porous (Wang & Kaskel, 2. The following are some suggested equations to describe the concrete process of carbon activation using KOH (Otowa et al. , 1. 2 KOH Ie K2O H2O . C H2O Ie H2 CO . ater-gas reactio. CO H2O Ie H2 CO2 . ater-gas shift K2O CO2 Ie K2CO3 . arbonate formatio. Once the activation temperature was higher than 700oC, a significant amount of metallic potassium was spotted. This element is considered to be formed as a result of the reduction of K2O by carbon or hydrogen at high temperatures: K2O H2 Ie 2K H2O . eduction by . K2O C Ie2K CO . eduction by carbo. Considering the fact that metallic potassium is easily moved and shifted . at activation temperatures, the element intercalated with the carbon matrix. As a consequence, the atomic layers of carbon were stretched, creating pores that can be used to boost the material's surface area and capacitance. Figure 4 shows the specific capacitance of all biomass previously listed in Table 3, which have a value over 400 Fg-1. In Figure 4, it can be seen that bamboo fibers exhibit the highest specific capacitance . eaching 512 F/cm-. compared to other biomass. The outstanding features of bamboo fibers include a large specific surface area . 0 m2/. with an excellent pore diameter . and capacitance retention . %). These good characteristics of bamboo fibers have attracted the interest of many, hence, it is crucial to evaluate further the effect of the KOH concentration on its physical properties . ee Figure . Figure 5 shows that AC from bamboo without KOH activation (Figure 5. possesses numerous pores uniformly distributed across its entire surface. However, when AC from bamboo is activated by 1M KOH, the atomic layer of carbon widens due to the intercalation of potassium . s explained in the process of carbon This intercalation increased with an increase in the concentration of KOH . ee Fig. 5b to Fig. , but it starts to decrease when the concentration reached 5M. Figure 4. The specific capacitance of biomass activated by KOH. DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 Hamidah et al. Biomass-Based Supercapacitors Electrodes for Electrical Energy Storage SystemsA | 452 Figure 5. SEM micrograph for bamboo sticks using KOH activating agent: . no activation, . 1M, . 2 M, . 3M, . 4 M, . DOI: https://doi. org/10. 17509/ijost. p- ISSN 2528-1410 e- ISSN 2527-8045 453 | Indonesian Journal of Science & Technology. Volume 8 Issue 3. December 2023 Hal 439-468 Upon further analysis of the role of KOH as an electrolyte, the element was found to produce higher capacitance retention compared to that of H2SO4 . ee the triple asterisk in Table . On the other hand. H2SO4 as an electrolyte produced a capacitance with a higher specific value than KOH. According to Liu et al. , the K ion is smaller in size than SO42-, enabling it to enter the microporous AC through its small pores, which SO42- cannot penetrate. The penetration of ions into the pore of microporous AC creates an Electric Double Layer (EDL) capacitance. However, when the pore diameter of the microporous AC is larger than 0. 6 nm. SO42- will be able to penetrate the pore and form EDL In addition, when the pore size is sufficiently large, a redox reaction occurs. The hydration of H in the redox reaction can result in the pseudocapacitance of By combining EDL with SO42and pseudocapacitance with H , micropore carbon attained a higher capacitance in H2SO4 than KOH. Even though biomass has more generated specific capacitance with KOH activation, the percentage of capacity retention needs Lastly, the carbon activation method used for this biomass source is the chemical activation method carried out using KOH. After undergoing the characterization process, these agricultural biomass sources produce an average of microporous to mesoporous size pores. CONCLUSION Carbon materials derived from biomass have shown great prospects as excellent electrodes for supercapacitors. This is because biomass comprises diverse chemical and structural properties that can be easily tailored as per the requirements. This study focuses on the chemical activation of carbon, which was obtained from biomass. The pore structure and the surface area created through this carbon activation method resulted in an increased current collection at electrode surfaces. Furthermore, specific capacitance is directly proportional to the highest surface area of AC. Among all biomass analyzed in this study, bamboo fibers show the highest specific capacitance with capacitance retention, a pore diameter, and a specific surface area. KOH-activated bamboo-based carbon has a higher specific surface area than unactivated carbon. The KOH activating agents produced a very porous structure due to their more complex The average pore diameter of carbon, which produced high specific capacitance, was within the range of microporous (<2 n. and mesoporous .