An Introductory Study on Activated Carbon Monolith Electrodes Fabrication from Teak Leaf Waste

Journal of Technomaterial Physics Vol. 1, No. 1, 2019 | 31 – 38 JoTP Journal of Technomaterial Physics An Introductory Study on Activated Carbon Monolith Electrodes Fabrication from Teak Leaf Waste Erman Taer1, Miftah ‘Ainul Mardiah2, Sugianto3, Rita Juliani4, Awitdrus5 and Rakhmawati Farma6 1,2.3,4,5,6 Department of Physics, Faculty of Mathematics and Natural Science, Universitas Riau, Pekanbaru 28293, Riau, Indonesia Abstract. A preliminary study has been conducted on supercapacitor carbon-electrode monolith prepared from teak leaf waste. The objective of this study is to know the electrochemical cell capacitance from carbon materials. The production of carbon electrode began with pre-carbonization process at 250°C for 2.5 hours, then proceeded to chemical activation using KOH activator with concentration of 0.3 M. Hydraulic Press was used with pressure at 8 ton to form the monolith. Then, the density was measured the carbonization. After that the sample was activated using CO2 gas at 850°C burning temperature. Next after the carbonization, the density was measured by collecting mass, diameter and thickness data of the electrode. The specific capacitance was measured using Physics CV UR Rad-ER 5481 which is controlled by a cyclic voltammetry software with the potential window width of 0 – 0.5 V and at a scan rate of 1 mV/s. The best density results obtained were 0.853 g/cm3 before carbonization for sample code C24 and 0.605 g/cm3 after carbonization for sample C30. The specific capacitance was found at 113.20 G/g for C32 and C38 electrodes Keyword:Teak leaf waste, activated carbon, supercapacitor Received 10 December 2018 | Revised [10 January 2019] | Accepted [28 February 2019] 1 Introduction Electrical energy has become world’s primary needs and brought big impacts to all lives aspects. The energy needs in Indonesia is still dependent on fossil fuel like crude oil, coal and natural gas as sources for electrical energy. This has impacted on air pollution and will affect the people’s lives and health [1]. Besides that, crude oil is non-renewable energy as it takes longer time to produce than the exploitation. Energy storage devices become one of the solutions as alternative energy, for example devices like batteries, fuel cells and capacitor. Batteries and fuel cells are capable to store high energy but with very little power, while capacitor has big power but is only capable to store small energy. Another device, as an advancement to capacitor, usually known as supercapacitor is made to allow a device with not only big power but also large energy storage [2-5]. *Corresponding author at: Bina Widya Km 12.5 Simpang Baru Pekanbaru, 28293, Riau, Indonesia. E-mail address: Copyright © 2019 Published by Talenta Publisher, ISSN: 2656-0747 e-ISSN: 2656-0755 Journal Homepage: https://talenta.usu.ac.id/index.php/JoTP 32 Supercapacitor consists of electrodes, separator, electrolytes and current collector. The Journal of Technomaterial Physics Vol. 1, No. 1, 2019 | 31 – 38 Electrodes in supercapacitors have big effect on the energy and power capability of the supercapacitors. A popular material for supercapacitor electrodes is activated carbon with nanometer pores. Activated carbon from biomass can be made of bagasse, coconut shells and fibers, rice husk, sawdust, hard wood, coal also waste leaf. Teak leaf are one of biomass waste that is interesting to be studied about as raw material for activated carbon because it is the biggest part of a Teak tree. It is considered as a deciduous tree that shed leaves at dry season, between November and January. After that, the leaves grow again in January or March. Fell off Teak leaves are suitable as biomass in supercapacitor fabrication as it reduces the amount of leaf waste produced. The carbon (C) content in Teak leaves is high, around 46.49 – 52.32% [6]. 2 Materials and Methods Electrodes fabrication started by collecting Teak leaf waste as the raw material. The sample was dried in an over at 110°C for 2 days. Then, pre-carbonization was done at 250°C for 2.5 hours in order to get brittle sample to ease the milling process in ball milling for 20 hours. In order to get fine and uniformity of pre-carbonized sample, the sieve with a size of 53 µm was used to get particles smaller than 53 µm. Chemical activation process was done by KOH activation of 0.3 M to increase the surface area. Then, the sample was neutralized and dried in an oven at 110°C for 3 days until dry. Dried sample was refined and weighed 0.7 g for 10 samples and they were molded into pellets. The molding process was done using hydraulic press at 8 tons pressure and given code C32 to C38. The carbonization process was done in a furnace at 600°C in N2 environment and followed by physical activation at 850°C in CO2 gas environment. After that, the sample was polished carefully with sandpapers (Hammer P1200) to reach certain thickness. The measurement done to sample was electrode dimension like mass, diameter, thickness and specific capacitance. The mass was measured using digital scales while the diameters and thickness were measured using Insize digital calipers. Those measurements were done after pellets molding and carbonization to observe the difference in density of the electrodes. The density was determined with the standard formula by dividing the mass and volume. Supercapacitor cell specific capacitance was done by Cyclic Voltammetry (CV) method using Physics CV UR Rad-Er 5841 controlled by cyclic voltammetry CVv6 software with the potential window width of 0 – 0.5 V at 1 m V/s scan rate. The results obtained were processed by sigma plot 8.0 program. Specific capacitance cell was done in sulfuric acid H2SO4 1 M electrolyte. Journal of Technomaterial Physics Vol. 1, No. 1, 2019 | 31 – 38 3 3.1 33 Result and Discussion Mass, thickness, diameter and density The mass of supercapacitor electrode cells before and after carbonization-activation process is shown in Figure 1. Based on the mass comparison diagram, sample mass before carbonization is different. The differences are caused by different condition during the molding process. Initial sample mass should be made the same as initial sample was weighed with the desired weight such as 0.7 g. The difference occur due to the non-uniformity in the mass before the molding process. However, the error due to mass factor is predicted to be relatively small at 5%. After the carbonization-activation, sample would shrink. The reduction in mass is caused by the released of non-carbon material like water, then the decomposition of organic compounds that make up the raw material like hemicellulose, cellulose and lignin [7]. The comparison of mass shrinkage after carbonization – activation is at 71.1% to 73.3%. The variations of sample shrinkage indicated differences in sample arrangement in the burning tube. Figure 1. Mass Diagram for Before and After Carbonization Figure 2. Average Diameter Diagram Before and A (...truncated)