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Journal : International Journal of Renewable Energy Development

Synthesis of rubber seed shell-derived porous activated carbons for promising supercapacitor application Rustamaji, Heri; Prakoso, Tirto; Devianto, Hary; Widiatmoko, Pramujo; Febriyanto, Pramahadi; Ginting, Simparmin br; Darmansyah, Darmansyah
International Journal of Renewable Energy Development Vol 14, No 2 (2025): March 2025
Publisher : Center of Biomass & Renewable Energy (CBIORE)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.61435/ijred.2025.60869

Abstract

This work investigates synthesizing activated carbon obtained from rubber seed shells utilizing several activating agents (KOH, CaCl2, and ZnCl2) for supercapacitor applications. Activated carbon was produced from a rubber seed shell using hydrothermal carbonization at 275 °C for 60 minutes and a 120-minute activation treatment at 800 °C. Various activating agents pronounced impacted the pore architecture, surface area, crystallinity, and level of graphitization, which collectively determined the electrochemical characteristics of the resulting materials. Incorporating activation agents enhances the specific surface area and influences the extent of graphitization of activated carbon. The specific surface area of activated carbon products ranges from 367 to 735.2 m² g⁻¹. Further investigation through electrochemical analysis, conducted with a carefully engineered two-electrode system, demonstrated a peak electrode capacitance value of 246 F g-1 at 50 mA g-1 for an ACZn-based supercapacitor. Supercapacitor cells’ energy and power densities reached significant levels, measuring 5.47 Wh kg-1 and 246 W kg-1, respectively. The RSS-derived activated carbon-based supercapacitor exhibited remarkable longevity in a 5000-cycle test, with consistent capacitance retention and coulombic efficiency of 100.11% and 100%, respectively. This work presents a sustainable pathway for producing activated carbon electrodes, contributing to the global circular economy and demonstrating considerable industrial potential.
Morphological and thermal stability analysis of Sn/C electrodes synthesized through impregnation and precipitation methods for CO2 electroreduction Eviani, Mitra; Prakoso, Tirto; Kusdiana, Dadan; Widiatmoko, Pramujo; Devianto, Hary
International Journal of Renewable Energy Development Vol 14, No 5 (2025): September 2025
Publisher : Center of Biomass & Renewable Energy (CBIORE)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.61435/ijred.2025.61280

Abstract

This study investigates tin (Sn) based electrodes supported by graphite for the electrochemical reduction of carbon dioxide (ECO2R) to formic acid, comparing precipitation and impregnation synthesis methods. Electrodes were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Thermogravimetric Analysis (TGA), Cyclic Voltammetry (CV), Chronoamperometry, and Electrochemical Impedance Spectroscopy (EIS). The precipitation method yielded higher Sn content (91.22%) and superior thermal stability (3% mass loss at 1000°C vs. 45% for impregnation). Morphological analysis through SEM revealed precipitation-synthesized electrodes exhibited more uniform Sn particle distribution across the graphite surface, while impregnation resulted in larger Sn agglomerates with less homogeneous coverage, significantly influencing electroactive surface area and catalytic performance. The electrochemical performance of electrodes was tested using H-cell. CV showed decreased cathodic current for Sn/C electrodes compared to pure graphite in CO2-saturated electrolyte, while chronoamperometry indicated slightly better sustained performance for precipitation-synthesized electrodes with stabilized current densities after 3 hours of operation. EIS analysis suggested the precipitation method yields a marginally lower ohmic resistance (28.8 Ω vs. 29.8 Ω), resulting in a more favorable electrode structure for overall catalytic activity. Both methods showed lower ohmic resistance than that of pure graphite (38.1 Ω), the precipitation-synthesized Sn/C electrode emerged as the preferred selection for ECO2R to formic acid, balancing high Sn content, thermal stability, superior durability, and better Faradaic efficiency. The observed performance differences were attributed to distinct metal-support interactions formed during synthesis, with precipitation creating stronger metal-carbon bonds that enhance stability but potentially limit certain active sites necessary for optimal CO2 reduction kinetics. This comprehensive characterization revealed that the precipitation-synthesized electrode offers the most promising foundation for further development, potentially through process optimization, hybrid synthesis approaches, or targeted doping strategies to enhance catalytic activity while maintaining the advantageous stability characteristics.
Evaluation of the effects of fatty ester isomerization and turpentine-derived additive introduction on biodiesel cold flow properties and oxidation stability Indarto, Antonius; Pradana, Yano Surya; Kembara Alam, Alif; Makertihartha, I Gusti Bagus Ngurah; Prakoso, Tirto; Soerawidjaja, Tatang Hernas
International Journal of Renewable Energy Development Vol 15, No 3 (2026): May 2026
Publisher : Center of Biomass & Renewable Energy (CBIORE)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.61435/ijred.2026.61192

Abstract

Biodiesel is a cleaner and renewable combustion fuel that globally serves as an effective alternative to fossil diesel. The current application of this biofuel is still restricted to specific concentration due to its poor cold flow properties (CFPs) and low oxidation stability (OS). Later, isomerization process was offered to improve cold flow properties as well as oxidation stability. In this study, palm-biodiesel isomerization was carried out atmospherically using SO4/SnO2 catalyst, prepared via wet nitration method, in the stirred batch reactor at temperature of 200oC, catalyst loading of 10 wt%, stirring speed of 900 rpm, and under N2 flow. The performance of catalyst and the effect of fatty ester isomerization on CFPs and OS were investigated. For comparative study, the effect of bio-additive (turpentine oil and α-terpineol) introduction, at concentrations of 1−10 vol%, on CFPs and OS was also evaluated. The isomerization results demonstrated a conversion ratio of 12.54±0.60%, an isomerization selectivity of 75.92±5.79%, and an overall turnover frequency of 1.75×10−1±8.5×10−3 h−1. This reaction had a small reduction in pour point (ΔPP = ‒1oC), a minor elevation in cloud point (ΔCP = 0.50±0.15oC), and a slight improving effect in OS (ΔOS = 1.36 h). Furthermore, the optimum insertion of bio-additive was α-terpineol at concentration of 5 vol%, demonstrating a more significant enhancement in CFP parameters (ΔPP = ‒1oC; ΔCP = ‒1.75±0.15oC). Nevertheless, it significantly reduced OS level (ΔOS = ‒11 h), although the absolute value (OS = 10.36 h) remains compliant with international standards.