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Seaweeds are large-scale multicellular marine algae categorized based on color as Chlorophyceae, Rhodophyceae, and Phaeophyceae. No information has been provided on the conditions affecting the production of mesoporous activated carbon from one member of the described aquatic plants, namely Sargassum sp. Therefore, this study aimed to determine the impact of the main factors and their interactions on Sargassum sp.-derived activated carbon manufactured (SAC) by hydrothermal carbonization and CO2 activation methods. A mathematical approach was employed using a multilevel factorial design with the main factors being the activator type (ZnCl2, CaCl2, & KOH), hydrothermal temperature (200, 225, & 250oC), and activator ratios (2 & 4). Meanwhile, the response variables were yield and BET surface area (SBET) of SAC. Morphological, functional, crystallographic, and porosity characterization was carried out on the samples. The SAC-Ca-200-2 sample had the highest yield, with the value being 26.5 percent of weight. The activators having the highest specific surface area (SBET) were SAC-Zn-250-4, SAC-Ca-225-2, and SAC-K-250-2, with 1552, 1368, and 1799 m2/g, respectively. The pore size distribution in SAC products ranged from 2.16 to 10 nm in diameter. The analysis conducted indicated the activator type and interaction with its ratio substantially impacted the SAC yield value; besides, only the activator type affects the formation of high surface area pores.

This research investigates the design, fabrication, and testing of single-cell and module supercapacitors. The supercapacitor consists of carbon nanocomposites, which contain activated carbon (AC), multiwall carbon nanotubes (MWCNT), and graphene (GR). The coin and pouch cell type supercapacitors were manufactured with AC: MWCNT: GR composite electrodes in a ratio of 70:20:10 weight percent. Meanwhile, the electrochemical characterization showed that the highest capacitance values for single coin and pouch cells were 32.13 F g-1 and 5.3 F g-1, respectively, in 6 M KOH electrolyte at a scan rate of 2 mV s-1. Furthermore, the power and energy densities for the coin-cell supercapacitor were 69 W kg-1 and 6.6 Wh kg-1, respectively, while for the pouch cell, it was 7.4 W kg-1 and 1.0 Wh kg-1, respectively. The coin-cell supercapacitor durability test was carried out for 1000 cycles, yielding the retention capacitance and coulombic efficiency values of 94-97% and 100%, respectively. These results showed that the performance of the supercapacitor is close to commercial products.

Supercapacitor is considered as a promising technology in the energy storage system (ESS) because of high power, large currents, and excellent cycle stability. In this study, activated carbon was used as the constituent material for electrodes because of its porous structure, a large surface area, high conductivity, low cost, and renewable. Activated carbon was synthesized from salacca peel by hydrothermal carbonization and chemical activation with KOH. In this research, the effect of operating pressure and temperature in the hydrothermal carbonization process was studied. The operating pressure was varied so that the water phase changed from vapor phase to liquid phase (subcritical water). The temperature was varied at 225 °C and 250 °C with a fixed carbonization time of 5 h. Chemical activation using KOH as an activating agent was done after obtaining the hydrochar from hydrothermal carbonization process. Produced activated carbons were characterized by nitrogen adsorption–desorption, scanning electron microscope, Fourier transform infrared, X-ray diffraction, and Raman spectroscopy. Electrochemical properties of these carbons were characterized by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The research results showed that the largest surface area of produced activated carbons was 2907.31 m2/g (obtained by carbonization in subcritical water at 250 °C) while the largest capacitance of supercapacitor is 15.57F/g (obtained activated carbon produced by carbonization in saturated mixture at 250 °C).

Dry reforming of methane was studied over high-ratio zirconia in ceria-zirconia-mixed oxide-supported Ni catalysts. The catalyst was synthesized using co-precipitation and impregnation methods. The effects of the catalyst support and Ni composition on the physicochemical characteristics and performance of the catalysts were investigated. Characterization of the physicochemical properties was conducted using X-ray diffraction (XRD), N

One of dye sensitized solar cell’s (DSSC) component is conductive glass, a transparent glass substrate covered with semiconductor oxide, usually fluorine-doped tin oxide (FTO). An economic and scalable method used to deposit the FTO film is spray pyrolysis. A research conducted by Fukano et al. (2004) showed that introducing intermittence in spray pyrolysis using batch atomizer improves the glass’ characteristics. This research aims to observe the effect of intermittence on spray pyrolysis method using nebulizer. A compressor nebulizer and hotplate were used, where the glass’ surface temperature reached 300 o C. Transmittance, conductance, morphology and composition of the glasses produced were analyzed. Deposition time and intermittence were varied. Variation of time were 5; 7.5; 10; 16; and 39 minutes. Deposition time of 7.5 minutes showed the highest figure of merit (FOM) of 7.83×10 -3 Ω -1 . Intermittence was performed by turning the nebulizer off during deposition, with varying period and amount of intermittence. Periods of intermittence were varied for 10, 20, and 30 seconds, and amounts of intermittence were varied 1, 2, and 3 times. Variation of 3 intermittences at 20 seconds each resulted in the highest FOM of 19.29×10 -3 Ω -1 . DSSC’s efficiency built using produced conductive glass are 1.9 × 10 -4 % and 5.5 × 10 -4 %.

Microbial fuel cell is one alternative technology that can be used to simultaneously solve problems related with wastewater production and energy demand. This study investigates the influence of electrode distance on power density in microbial fuel cell using tapioca wastewater. Graphite sheet without metal catalyst was used for both electrodes, separated by Nafion membranes. Four variations of electrode distance were used. MFC with highest electrode distance give the highest equilibrium OCV (676 mV), while the MFC with shortest electrode distance give the highest power density (7.74 mW/m2). EIS measurement suggested that the charge transfer resistance is dominant in all MFC configuration. Wastewater COD removal were in the range of 35-46 %, which were in accordance with the power density for all MFC.

The production of sustainable diesel without hydrogen addition remains a challenge for low-cost fuel production. In this work, the pyrolysis of unsaturated fatty acid (UFA) basic soaps was studied for the production sustainable diesel (bio-hydrocarbons). UFAs were obtained from palm fatty acids distillate (PFAD), which was purified by the fractional crystallization method. Metal hydroxides were used to make basic soap composed of a Ca, Mg, and Zn mixture with particular composition. The pyrolysis reactions were carried out in a batch reactor at atmospheric pressure and various temperatures from 375 to 475 °C. The liquid products were obtained with the best yield (58.35%) at 425 °C and yield of diesel fraction 53.4%. The fatty acids were not detected in the pyrolysis liquid product. The gas product consisted of carbon dioxide and methane. The liquid products were a mixture of hydrocarbon with carbon chains in the range of C7 and C20 containing n-alkane, alkene, and iso-alkane.

Disposal of palm oil mill effluent (POME), which is highly polluting from the palm oil industry, needs to be handled properly to minimize the harmful impact on the surrounding environment. Photocatalytic technology is one of the advanced technologies that can be developed due to its low operating costs, as well as being sustainable, renewable, and environmentally friendly. This paper reports on the photocatalytic degradation of palm oil mill effluent (POME) using a BiVO4 photocatalyst under UV-visible light irradiation. BiVO4 photocatalysts were synthesized via sol-gel method and their physical and chemical properties were characterized using several characterization tools including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), surface area analysis using the BET method, Raman spectroscopy, electron paramagnetic resonance (EPR), and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). The effect of calcination temperature on the properties and photocatalytic performance for POME degradation using BiVO4 photocatalyst was also studied. XRD characterization data show a phase transformation of BiVO4 from tetragonal to monoclinic phase at a temperature of 450 °C (BV-450). The defect site comprising of vanadium vacancy (Vv) was generated through calcination under air and maxima at the BV-450 sample and proposed as the origin of the highest reaction rate constant (k) of photocatalytic POME removal among various calcination temperature treatments with a k value of 1.04 × 10−3 min−1. These findings provide design guidelines to develop efficient BiVO4-based photocatalyst through defect engineering for potential scalable photocatalytic organic pollutant degradation.

The supercapacitor has gotten a lot of attention as a high-performance energy storage device because of its high power density, good energy density, long life cycle, and extensive application in various electronic applications. To effectively assess its performance, the electrode material composition was optimized with a blend of activated carbon (AC), multiwall carbon nanotube (MWCNT), and graphene (GR). The synergistic effect of AC, CNT, and GR supports the usage of AC/MWCNT/GR as a viable supercapacitor electrode. Furthermore, the surrounding MWCNT enhances AC and GR electronic conductivity, while AC efficiently suppresses GR re-stacking sheets and aggregates MWCNT particles. For supercapacitor electrodes, the optimal composite mixtures of AC, MWCNT, and GR were 71.7%, 20%, and 8.3% wt, respectively. Meanwhile, an outstanding capacitance value of 33.5 F g-1 in 6 M KOH electrolyte was obtained at 2 mV s-1.

Activated carbon (AC) has been utilized for various applications including as an electrode for supercapacitor, i.e., electric double-layer capacitor (EDLC) as well as hybrid capacitor such as lithium ion capacitor. In this research, salacca peel was used as a raw material for AC. It was chosen among other biomass wastes because it is abundant and is still considered as a waste. The hydrothermal carbonization was conducted at 5 MPa, temperature of 200–250 °C, and 5 h in subcritical water, which is a green dehydrating agent. The effect of parameters (temperature and addition of citric acid as a catalyst) on the hydrochar and AC product was investigated. The hydrochar from hydrothermal carbonization was activated by chemical activation using potassium hydroxide (KOH) as an activated agent to enhance the surface area and porosity. The morphology of both hydrochar and AC was measured by scanning electron microscopy (SEM), its chemical transformation was measured by Fourier transform infrared spectroscopy (FTIR) while the surface area and pore size distribution were measured by nitrogen adsorption at 77.35 K. The electrochemical performance of activated carbon from salacca peel as well as commercial activated carbon using a coin cell in a Li half-cell system was evaluated by CV, GCD, and EIS. The results show that the presence of citric acid contributes to higher specific capacitance in the rate performance test of LIC at different current density as well as in long rate stability test.

Produksi hidrogen melalui elektrolisis menggunakan energi matahari sangat potensial di Indonesia, namun terkendala oleh ketidakstabilan penyinaran matahari. Penggunaan sumber listrik konvensional sebagai komplementer dapat mengatasi ketidakstabilan tersebut. Dalam penelitian ini, elektrolisis air dilakukan dalam sel dengan ruang ganda dengan elektrolit larutan KOH 3 M. Variasi dilakukan terhadap jenis dan bentuk elektroda serta laju alir elektrolit. Sumber energi listrik divariasikan dengan sumber listrik konvensional dari PLN, modul fotovoltaik, serta hibrid dari kedua sistem tersebut. Kinerja elektrolisis dianalisis dengan mengukur volum hidrogen yang terbentuk, rapat energi yang dibutuhkan, serta efisiensi arus listrik. Hasil penelitian menunjukkan penggunaan sistem hibrid dapat menstabilkan produksi hidrogen untuk elektrolisis pada tegangan 15 V selama 7 jam operasi. Dibandingkan dengan penggunaan listrik PLN sepenuhnya, sistem hibrid memberikan peluang penghematan energi hingga 81,64%.

This research studied the effect of electrode deposition method on the performance of dye-sensitized solar cells (DSSCs). Four deposition methods (bar coating, doctor blade coating, screen printing, and spray coating) were compared. For commercial production purposes, applicability of the methods to a scaled-up DSSC was studied. In order to minimize the production cost, commercial activated carbon was utilized as counter electrode. The experimental results showed that the doctor blade technique provided the best DSSC performance among the investigated methods. Based on the study of cell I-V characteristics, the photoelectric conversion efficiency of the DSSC with an electrode active area of 70 cm2 was significantly lower than with 5 cm2 despite using the same deposition method. The electrochemical characteristics of the cells were further studied using electrochemical impedance analysis.

Activated carbon is a highly porous material that has been used as electrodes for batteries, symmetric, and asymmetric supercapacitors. In this study we utilize salacca peel as a precursor to synthesis activated carbon (AC) using hydrothermal carbonization (HTC) and microwave assisted chemical activation method. The HTC was done at 225°C, 50 bar for 5 h using citric acid as a catalyst. The obtained hydrochar (HC) was furthermore impregnated using KOH as activating agent at various HC to KOH mass ratio (1:2, 1:3, and 1:4). The activation was done under microwave radiation of 700 Watt for 8 min. The obtained AC samples were characterized using scanning electron microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and methylene blue adsorption. The best AC with ratio 1:4 was furthermore tested as nickel ion's capacitor electrode. The electrochemical characteristics (cyclic voltammetry) were measured by using half-cell test pouch with nickel oxide as a reference electrode and 6 M KOH as electrolyte. The results obtained showed that AC from salacca peel gave better performance compared to commercial AC.

The growth of Serratia marcescens depends on its metabolism, which is influenced by environmental factors, such as pH and temperature. The metabolic activity of Serratia marcescens may influence the corrosion of carbon steel by forming a biofilm on the metal surface. This research is focused on determining the effect of pH on carbon steel corrosion caused by Serratia marcescens. The medium used as immersion solution was a mixture of synthetic seawater and Luria-Bertani medium with a volume ratio of 4:1. The carbon steel coupons with a size of 1 cm x 1 cm were immersed in the solution with initial pH of 5, 7, and 9. The analyses of biofilm were conducted by total plate count (TPC), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Biofilm was detected evenly on the metal surface and decreased with an increase in incubation pH. The biofilm consists of some functional groups, such as alcohol, alkane, amine, nitro, sulphate, carboxylic acid, and polysulfide. The analyses of the corrosion were conducted by gravimetric and X-ray diffraction (XRD). The pHs of 5 and 9 were found to give an increase in the corrosion rate. The average corrosion rate at pH variations of 5, 7, and 9 were 2.5309 g/m 2 .day; 2.2844 g/m 2 .day; and 2.9756 g/m 2 .day, respectively. Nevertheless, the corrosion products were not detected by XRD analysis. Keywords: biocorrosion; carbon steel; pH; seawate r; Serratia marcescens Abstrak PENGARUH pH AWAL LARUTAN PADA PEMBENTUKAN BIOFILM DAN KOROSI BAJA KARBON OLEH Serratia marcescens . Laju pertumbuhan Serratia marcescens bergantung pada aktivitas metabolise mikroba, yang akan sangat dipengaruhi oleh faktor lingkungan, seperti pH dan temperatur. Aktivitas metabolisme Serratia marcescens dapat memengaruhi korosi pada baja karbon dengan membentuk lapisan biofilm pada permukaan logam. Penelitian ini bertujuan untuk menentukan efek pH pada korosi baja karbon yang disebabkan oleh Serratia marcescens. Media yang digunakan sebagai larutan perendam adalah campuran air laut sintetis dan media Luria-Bertani dengan perbandingan volume sebesar 4:1. Kupon baja karbon dengan ukuran 1 cm x 1 cm direndam dalam larutan dengan pH awal 5, 7, dan 9. Analisis lapisan biofilm dilakukan dengan total plate count (TPC), scanning electron microscopy (SEM) dan Fourier transform infrared spectroscopy (FTIR). Lapisan biofilm tumbuh secara merata pada permukaan logam dan berkurang seiring dengan peningkatan pH inkubasi. Lapisan biofilm mengandung berbagai gugus fungsional, seperti alkohol, alkana, amin, nitro, sulfat, asam karboksilat, dan polisulfida. Analisa korosi dilakukan dengan gravimetri dan X-ray diffraction (XRD). Penggunaan pH 5 dan 9 memberikan peningkatan terhadap laju korosi. Laju korosi rata-rata pada pH 5, 7, dan 9 ditentukan sebesar 2,5309 g/m 2 .day; 2,2844 g/m 2 .day; and 2,9756 g/m 2 .day. Namun, produk korosi tidak terdeksi oleh analisis XRD. Kata kunci: biokorosi ; baja karbon ; pH; air laut; Serratia marcescens

Electric vehicles are set to become a most attractive alternative transportation mode due to their high efficiency and low emission. Electric vehicles require an efficient energy storage system, e.g. a supercapacitor. Coconut shells have high lignocellulosic content and are not being fully utilized in Indonesia. The lignocellulose could be converted into activated carbon for use as the electrode on a hybrid supercapacitor. This research focused on studying the effect of the addition of carbon nanotube (CNT) composite to porous graphene-like nanosheets (PGNS) as the electrode on a hybrid supercapacitor. The PGNS and CNT composite were synthesized via simultaneous activation and carbonization. Nickel oxide was used as the counter electrode. The CNT composite had a large surface area of 1374.8 m 2 g -1 , pore volume of 1.1 cm 3 g, and pore size of 3.2 nm. On the other hand, the PGNS had a surface area of 666.1 m 2 g -1 , pore volume of 0.47 cm 3 g, and pore size of 2.8 nm. The electrode pair between the NiO and the activated carbon achieved 5.69 F/g and 94.1% cycle durability after 10 charging and discharging cycles. The composite had an energy density of 0.38 W h kg -1 . The aim of this research was to provide an alternative formula for producing high-performance supercapacitor materials.

A variety of technologies to diminish greenhouse gases CO2 emission have been extensively explored in recent years. One promising technology called electrochemical reduction of CO2 have been developed to convert CO2 into value-added chemicals, such as methanol, ethanol, ethylene, and formic acid. One of important parameter that need to be considered is the size of CO2 bubbles. In general, decreasing bubbles size can increase retention time of carbon dioxide in an electrolyte. In this research, effect of the microbubble size on the effectiveness of electrochemical reduction of carbon dioxide to formic acid was studied. Bubbles with average diameter 0.321 and 0.952 mm were generated through perforated glass apparatus. The FTIR analysis showed peak at 1634 cm−1 which attributed to C=O bonding of formic acid. Smaller bubble size showed relatively more stable and higher electric current during electrolysis, indicating better retention time of carbon dioxide in the electrolyte.

Solid Oxide Fuel Cell (SOFC) is one type of fuel cell that has several advantages over other types of fuel cells. To achieve low cost SOFC, the materials used are nickel oxide (NiO) for the anode, Calcia Stabilized Zirconia (SCZ) for the electrolyte and Calcia Cobalt Oxide Zinc Oxide (CCZO) as cathode. Fe2O3 is a doping agent to form a denser electrolyte. The cell with and without Fe doping was tested using hydrogen and ambient air. Additionally, the effect of the amount of fuel flow rate is also investigated using Aspen Plus Modelling. Based on physical characterization, it is determined that 3%-mole Fe doping on the electrolyte increases the electrolyte density from 83% to 90%. Using electrochemical impedance spectroscopy, it can be concluded that SOFC with Fe doped electrolyte has a lower resistance than SOFC without Fe doping. On the other hand, using a correction factor, an equation of power correlated to fuel flow for the SOFC is generated to show increasing fuel flow enhanced SOFC performance.

Indonesia committed to reduce greenhouse gas emission by 29% in 2030. Carbon dioxide (CO2) emissions from flue gas in coal power plant must be captured to reduce greenhouse gas emissions. Technology to decrease greenhouse gases on a large scale and in a relatively short period is Carbon Capture and Storage (CCS). Chemical absorption method is a more advantageous CCS technology than other methods owing to high efficiency, low cost, and mature technology. Solvents in chemical absorption include amine-based solvent such as monoethanolamine (MEA) was frequently utilized to absorb CO2 from low-pressure flue gas streams, especially fossil fuel-based power plant, owing to rapid reaction rate with CO2 and low cost of raw amines compared to other amines. In this study, Aspen Hysys was used to simulate the CO2 capture process and 30 wt% of MEA was selected as a solvent which is mainly handy for CO2 capture from flue gas. The results show that lean amine temperature, flue gas temperature, and regenerator feed temperature has effects on the CO2 capture and energy consumption. The rich-split stream configuration was developed to examine energy reduction in various split fractions. The minimum in energy consumption and reboiler duty occurs when 30% of the solvent is split to the top of the column.

Carbon Nanotube (CNT) has outstanding properties such as electrical conductivity, specific surface area, charge transport capability, mesoporosity, and very high electrolyte accessibility. Based on these properties, CNTs are very suitable to be used as high-performance supercapacitor electrodes which can be seen from the capacitance. One of the factors that can lead to increase capacitance is the high interface interaction between CNT and the electrolyte. The interface interaction of CNT and electrolyte can be improved by increasing the CNT wettability using hydrophilization. CNT is synthesized by pyrolysis with Palm Oil Mill Effluent (POME) as the main raw material. In this study, hydrophilization was carried out using chemical activation HNO3 with various concentrations and activation times (1M for 1, 3, 6 hours, and 13M for 1 hour). The results of CNT structure were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), and X-Ray Diffraction (XRD), as well as electrochemically characterized using cyclic voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) dan galvanostatic charge-discharge (GCD), as supported data to evaluate which concentration and activation time with the highest efficiency to improve CNT performance as a supercapacitor. Based on CV characterization, the capacitance of CNT before hydrophilization, and after hydrophilization using HNO3 (1M for 1 hour, 3 hours, 6 hours, and 13M for 1 hour) were 10 F/g, 13.30 F/g, 14.28 F/g, 26.95 F/g and 24.5 F/g respectively. When CNT hydrophilized at 13M for 1 hour, capacitance decreased. Due to surface damage of CNT, therefore the performance of the supercapacitor decreased. This was supported by the results of the GCD characterization, where some charges could not completely release.

Utilization of biomass using gasification technology combined with Molten Carbonate Fuel Cell (MCFC), is an option to solve fossil fuels and environmental pollution problem. Various types of biomass give different composition of the gas produced by gasification process and indirectly affect the performance and durability of MCFC. This research is focused on determination of gas composition produced by gasification process (CO, CO2, H2 and N2) that gives optimum performance and durability of MCFC either in dry or wet condition. Using mixture design method, the gas composition supplied to MCFC anode is varied in the range of 14%–25% for CO, 9%–17% for H2, 10%–20% for CO2, and 51%–58% for N2. The effect of feed gas composition on the performance and durability of MCFC is characterized by using potentiodynamic method and accelerated load cycle method respectively. SEM and XRD is used in this study to evaluate gas composition effect on MCFC anode morphology. Based on experiments that are carried out, the optimum result is obtained by using syn-gas from coconut shell gasification with composition of 25% CO, 12% H2, 10% CO2 and 53% N2 in wet condition. Electrical power of 0.13 W is generated within 228 days of durability or it is decreased by 135 mV/1000 h or 16% (v/v)/1000 h.

Mesoporous Ce0.75Zr0.25O2 solid solution powders were successfully synthesized by a co-precipitation method. A combination of 10 wt% copper oxide, manganese oxide, and nickel oxide was added to the Ce0.75Zr0.25O2 support by impregnation method and calcined in the air with a flow rate of 2 ml s−1 at 400 °C for 4 h. All catalysts were characterized using Hydrogen Temperature Programmed Reduction (H2-TPR), X-ray Diffraction (XRD), and Brunauer-Emmet-Teller (BET) isotherm methods to find the interaction between metals, the crystallinity of the catalyst, surface area and pore volume of the catalyst, respectively. The 3.3% CuO-3.3% MnO2-3.3% NiO/Ce0.75Zr0.25O2 catalyst showed higher catalytic activity for benzene oxidation with benzene conversion of 90% at 250 °C and weight hourly space velocity (72,000 mL g−1 h−1) when compared to one metal oxide only. This finding presents a high activity and low-cost catalysts for removing a very lean concentration of benzene containing in the industrial flue gas at low temperatures.

Graphene is a two-dimensional sp2 bonded carbon nanostructure packed in a honeycomb crystal lattice. Graphene has a high theoretical surface area and electrical conductivity that is suitable for the electrode of supercapacitors. There are many methods to produce graphene, such as mechanical exfoliation using scotch tape, reduction of graphene oxide, and chemical vapor deposition. An alternative and simple method to produce graphene is through pyrolysis process. The previous study shows that the production of graphene from biomass via two-stage pyrolysis process results in an increase of the surface area; however, its capacitance is still low to be applied as the electrode for supercapacitor. This study aims to modification of graphene surface using cetyltrimethylammonium bromide (CTAB) as the surfactant. The graphene was produced from palm kernel shell via two-stage pyrolysis method (the first stage was at 350°C followed by the second stage at 900°C) using FeCl3 as catalyst and ZnCl2 as activating agent, resulting in 16% yield. Graphene was analyzed using Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Raman scattering, X-ray Diffraction (XRD), and Fourier Transform Infrared (FTIR). These analyses show that the two-stage pyrolysis produces multi-layered graphene. The surface properties were analyzed by nitrogen adsorption-desorption measurements, which show some mesoporous graphene product with a surface area of 351.27 m2/g. The result exhibited more hydrophilic graphene than the unmodified one, but according to the Cyclic Voltammetry (CV) analysis, the specific capacitance of modified graphene (11.91 Fg-1) is lower than unmodified graphene (43.87 Fg-1).

Carbon dioxide released to the atmosphere due to fossil combustion needs to be reduced to decrease the global warming effect. Electrochemical reduction of CO2 is one of promising technology to convert CO2 to various valuable compounds, reducing the amount of released CO2 to the atmosphere. Metal alloys are interesting material for cathode. In this preliminary work, a CO2 electrochemical reduction was performed on a Pb-Sn alloy cathode using catholyte of KHCO3 and NaHCO3 at various concentrations. An anode from Pt-Ir and H2SO4 0.1 M as anolyte were used in the experiment. The CO2 was bubbled into 400 mL catholyte at rate of 75 mL min-1. It was found that Pb-Sn alloy in KHCO3 electrolyte provides higher productivity and faradaic efficiency than in NaHCO3. Increasing overpotential from 0.1 V to 1 V increases both formic acid productivity and efficiency. The optimum amount of formic acid produced was 9400 μmol in catholyte KHCO3 0.5 M with faradaic efficiency of 67.19% and conversion of 0.326%.