Nafisah Osman

Role of CA-EDTA on the Synthesizing Process of Cerate-Zirconate Ceramics Electrolyte

The role of a combination between citric acid (CA) and ethylenediaminetetra acetic acid (EDTA) as chelating agents in preparation of BaCe0.54Zr0.36Y0.1O2.95 powder by a modified sol-gel method is reported. The precursor solutions were prepared from metal nitrate salts (M

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) Perovskite Nanorods by Template Synthesis

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) is a ceramic perovskite-type oxide that has attracted growing attention due to its high catalytic activity, mixed ionic/electronic conductivity and giant magnetic resistance. Improvement in the properties of BSCF can be achieved by tailoring its architecture such as nanoparticles (powdered form), nanotubes or nanorods as these nanostructured materials posses high surface-to-volume ratios with high sensitivity to surface adsorption and reactions. However, most of the studies conducted by means of conventional solid-state reaction methods or with wet chemistry techniques regularly produced BSCF in loose powdered form, non-uniform and the particle size is hard to be controlled. Herein in this work, an investigation on a synthetic approach using highly ordered nanoporous anodic aluminium oxide (AAO) as a template, focusing on the fabrication of BSCF perovskite nanorods is demonstrated. Sol-gel method is used to prepare the BSCF precursor solution or sol followed by filling the AAO template with the sol at different immersion time of 1 hr, 12 hrs and 24 hrs. After the following drying and calcination steps, the morphological structure and composition of the synthesized BSCF nanorods inside the AAO templates are examined by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) analysis. The micrograph showed BSCF nanorods are successfully synthesized at immersion time of 24 hrs with the diameter of nanorods embedded in the AAO template is approximately 180 nm. The EDX analysis also confirmed the stoichiometry of Ba0.5Sr0.5Co0.8Fe0.2O3-δ. Possible formation mechanism of BSCF nanorods inside the AAO template is also discussed in this paper.

Penyediaan serbuk lantanum strontium kobalt oksida melalui kaedah sol-gel terubahsuai

A simple low temperature synthesis route has been presented for the preparation of single perovskite phase of La0.6Sr0.4CoO3-δ (LSCO) for cathode application in intermediate temperature proton conducting solid oxide fuel cell (SOFC). A wet chemical method namely a modified sol-gel method has been applied in this work. In this method, a combined citric acid and ethylenediaminetetraacetic acid (EDTA) has been used as a chelating agent. Ethylene glycol (EG) and activated carbon (AC) have been used as surfactants in this process. The synthesized powders were characterized by X-ray diffractometer (XRD), scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) spectrometer and particle size analyzer (PSA) for phase formation, morphology and particle size analysis, respectively. XRD result revealed that a single LSCO perovskite phase for both surfactants formed at calcination temperature of 900 °C. The produced single phase powders consist of homogeneous and almost identical shape of particles as shown in SEM images. However, the powder prepared using EG has a smaller average particle size diameter as compared with the powder prepared using AC which is 149 nm and 190 nm, respectively.

Microstructure control of SOFC cathode material: The role of dispersing agent

In the present works, La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode powders were synthesized by a sol-gel method with the aid of ethylene glycol which served as the dispersing agent. The phase formation and morphology of the powders were examined by X-Ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM), respectively. The electrochemical properties of the synthesized cathode were obtained using an electrochemical impedance spectroscopy (EIS). The characteristic peaks for LSCF phase appears in the X-ray diffractogram after calcined at 500 °C and complete formation of LSCF single phase was attained at 700 °C. FESEM micrographs showed the presence of spherical particles of the powders with approximate particle size between 10 to 60 nm along with agglomerate morphologies. Well dispersed particles and fewer aggregates were observed for samples prepared with addition of ethylene glycol as the synthesizing aid. The surface area obtained for powder sample prepared with the aid of dispersing ...

Contact Formation at Interface of LSCO|BCZY|LSCO Symmetrical Cell: Effect of LSCO to PVP Ratio

Symmetrical cells of La0.6Sr0.4CoO3-δ (LSCO) cathode and BaCe0.54Zr0.36Y0.1O2.95 (BCZY) electrolyte (LSCO|BCZY|LSCO) were fabricated by manually painting the respective LSCO cathode slurries onto pellet surfaces of BCZY. The slurries were prepared with different ratios of LSCO to polyvinyl pyrrolidone, PVP as electrode binder (LSCO:PVP). The fabricated cells were denoted as S#1 (5:1/2), S#2 (5:1), S#3 (5:3/2), S#4 (5:2) and S#5 (5:5/2). The contact formation at LSCO|BCZY interface at different ratios of LSCO:PVP was examined by a scanning electron microscope (SEM). SEM images revealed that the LSCO cathode was well adhered onto BCZY electrolyte in all samples without formation of air gap/hole at the interface, except for S#4 and S#5. The elemental composition percentage and formation of air gap/hole at the interface were confirmed by electron dispersive spectroscopy (EDS). The optimum ratio in obtaining a good adhesion between LSCO cathode and BCZY electrolyte is PVP:LSCO = 1/2 – 2 : 5. The polarization resistance (Rp) for the S#1 measured by an electrochemical impedance spectroscopy (EIS) is 0.29 Ωcm2 at 700 °C.

Preparation of Nano-Structured Cathode for Proton-Conducting Fuel Cell by Dispersing Agent-Assisted Sol-Gel Method

The development of high-performance cathodes is essential towards the operation of proton-conducting fuel cells (PCFCs) at intermediate temperatures. To that end, the performance of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathodes is very attractive. In the present works, LSCF cathode powders were synthesized by a sol-gel method with the aid of ethylene glycol which served as the dispersing agent. The pristine and modified samples were each denoted as LSCF64 and LSCF-EG5. The phase formation and morphology of the cathode powders were examined by X-Ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM), respectively. In order to evaluate the cathode performance, a symmetrical cell of electrolyte supported PCFCs were examined using an electrochemical impedance spectroscopy (EIS) at a 700 oC in atmosphere containing humidified air. The formation of LSCF single phase was attained at 700 °C for both prepared samples. The FESEM images confirms an improvement in the microstructure of the modified cathode. The impedance spectra obtained from the electrochemical impedance measurement were resolved by a fitting procedure using an equivalent circuit that consists of a combination of two parallel pairs of resistor-constant phase element (R-Q) in series. The area specific resistance (ASR) determined for LSCF64 and LSCF-EG5 is 1.55 and 0.23 Ωcm2 , respectively. The better performance exhibited by LSCF-EG5 is attributed to its higher cathode reaction site due the improved microstucture. This study reveals that the application of ethylene glycol as dispersing agent is effective in producing a high quality cathode material for better PCFCs performance.

Electrical and electrochemical characteristics of La0.6Sr0.4CoO3-δ cathode materials synthesized by a modified citrate-EDTA sol-gel method assisted with activated carbon for proton-conducting solid oxide fuel cell application

AbstractThe electrical conductivity and electrochemical performance of a La0.6Sr0.4CoO3-δ (LSC) cathode produced by a modified citrate-EDTA sol-gel method assisted with activated carbon are characterized for a proton-conducting solid oxide fuel cell (H+ −SOFC) application at intermediate temperature. Thermogravimetric analysis revealed that the decomposition of the unrequired intermediate compounds in the precalcined powder was completed at 800 °C. A single LSC perovskite phase was formed at a calcination temperature of 900 °C, as confirmed by X-ray diffraction analysis. The particle size, crystallite size, and BET-specific surface area of the powder are 219–221 nm, 18 nm, and 9.87 m2 g−1, respectively. The high index value of the extent of agglomeration (5.53) showed that the powder was barely agglomerated. Bulk LSC sintered at 1200 °C for 2 h showed the highest direct-current electrical conductivity (σd.c) compared to that of bulk LSC sintered at 1000 °C and 1100 °C. The value of σd.c was affected by the density and porosity of the sintered samples. The area specific resistance (ASR) of screen-printed LSC working on a proton conductor of BaCe0.54Zr0.36Y0.1O2.95 (BCZY) decreased from 5.0 Ω cm2–0.06 Ω cm2 as the temperature increased from 500 °C to 800 °C with an activation energy of 1.079 eV. Overall, in this work, the LSC material produced with the aid of activated carbon meet the requirements for the application as a cathode in an intermediate temperature H+-SOFC.

Characterization of Acid Treated Activated Carbon From Oil Palm Empty Fruit Bunches (EFB)

Activated carbon (AC) has a high potential to act as dispersing agent as the surface of the activated carbon can be modified by chemical and/or physical treatments. In this work, several acid treatment methods have been conducted by using nitric acid (HNO3), hydrogen peroxide (H2O2) and a mixture of nitric acid and sulfuric acid To functionalize the activated carbon from oil palm empty fruit bunches (AC-EFB), those treatments were followed by washing with distilled water until neutral pH and dried overnight in an oven at 80 °C. A dispersion test was conducted by dispersing a small amount of the treated AC-EFB in distilled water using a sonicator for 5 minutes. The modified AC-EFB has been characterized by using, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. Based on observation, the treated AC-EFB with a mixture of acids has a stable suspension compared to other methods which indicate the presence of a hydroxyl group attached to the surface of AC-EFB. FTIR results further confirmed the presence of the functional group of hydroxyl. The SEM micrograph shows the formation of unique microstructure on the AC-EFB structure after treated with method M3 whereas the number of pores developed was increased. The atomic percentage of oxygen of treated AC-EFB was higher than untreated AC-EFB, which indicates the hydroxyl group was attached to the surface of activated carbon as proven by EDX analysis. Thus, acid treated method using HNO3/H2SO4 mixture shows a promising approach on synthesizing the activated carbon with unique properties and characteristics.

A new route of synthesizing perovskite nanotubes by templating approach

A perovskite oxide for example Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) has attracted growing attention due to its high catalytic activity and mixed ionic/electronic conductivity. Recent research of BSCF is more comprehensively based on a remarkable trajectory of innovation, in particular with regards to the synthesis of perovskite structures in one-dimensional (1-D) nanometric scales as they promote not only to increase an active electrode area for the oxygen reduction reaction, but also allow the tailoring of electrode’s architecture. Nevertheless, achieving the desired 1-D structure by a conventional method such as hydrothermal, solvothermal, or sonochemical are far from satisfactory. Herein, the aim of this work is to synthesize the BSCF perovskite nanotubes via soft templating approach, particularly using anodic aluminium oxide (AAO) as a template, focusing on the morphology, composition and structural properties were demonstrated. After the AAO template was anodized at 80 V, the fabricated template was clamped between apair of spectroscopic cells containing BSCF sol and deionized water (with a hole of both sides) for 24 hours. After that, the sample was removed from the cells followed by heat treatment process. The FESEM images showed that BSCF nanotubes were successfully achieved, with the diameter of the nanotubes’ approximately 80 nm. The EDX result also confirmed the nominal stoichiometry of Ba0.5Sr0.5Co0.8Fe0.2O3-δ. Meanwhile, the XRD pattern confirmed a single crystalline phase of BSCF nanotubes was successfully obtained and congruent to a cubic perovskite structure of BSCF. Possible formation mechanism,as well as the schematic illustration of BSCF nanotubes inside the template was also discussed in this paper.A perovskite oxide for example Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) has attracted growing attention due to its high catalytic activity and mixed ionic/electronic conductivity. Recent research of BSCF is more comprehensively based on a remarkable trajectory of innovation, in particular with regards to the synthesis of perovskite structures in one-dimensional (1-D) nanometric scales as they promote not only to increase an active electrode area for the oxygen reduction reaction, but also allow the tailoring of electrode’s architecture. Nevertheless, achieving the desired 1-D structure by a conventional method such as hydrothermal, solvothermal, or sonochemical are far from satisfactory. Herein, the aim of this work is to synthesize the BSCF perovskite nanotubes via soft templating approach, particularly using anodic aluminium oxide (AAO) as a template, focusing on the morphology, composition and structural properties were demonstrated. After the AAO template was anodized at 80 V, the fabricated template was clamp...

Reactivity Study of LaSrCoFeO3 - Ba(Ce,Zr)O3 Composite Cathode Material

This paper reports on the reactivity study of composite cathode materials that comprises different weight percent of La0.6Sr0.4Co0.2Fe0.8O3-α (LSCF) and BaCe0.54Zr0.36Y0.1O3-α (BCZY). BCZY and LSCF powders are both prepared by a sol-gel method using metal nitrate salts as precursor. In this work, three samples with different weight percent ratios of 30, 50 & 70% of LSCF to BCZY were used and denoted as sample A1, A2 and A3, respectively. The powder mixtures of all samples were calcined at temperature of 1000 °C for 10 hours in an air. The phase formation of the samples was identified by X-ray diffractometer (XRD). As a comparison, XRD measurements for the LSCF and BCZY powders were also conducted individually, and their single-phase XRD pattern was used to identify the formation of undesired secondary reaction of the powdered mixture. The analysis of room temperature XRD data revealed that A1, A2 and A3 samples exhibit a complete solid solution between the crystal structures of LSCF cathode and BCZY electrolyte. The peaks can be indexed to (110), (020), (202), (220), (132), (224), (332) that belong to the LCSF phase and (110), (200), (211), (220), (310), (222) peaks that fit to the BCZY phase. No additional reaction products or secondary phases were observed indicating that up to 1000 °C, the prepared mixture formed a decent LSCF-BCZY composite. The average values of the lattice parameters for all the samples confirmed their phases were stable with the increasing BCZY content. Thus, it found that the LSCF is compatible with BCZY to form LSCF-BCZY composite for potential cathode material.