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Understanding the impact of sintering temperature on the physical and chemical properties of Ni-BaCe0.54Zr0.36Y0.1O3-δ (Ni-BCZY) composite anode is worthy of being investigated as this anode is the potential for protonic ceramic fuel cell (PCFC) application. Initially, NiO–BCZY composite powder with 50 wt% of NiO and 50 wt% of BCZY is prepared by the sol–gel method using citric acid as the chelating agent. Thermogravimetric analysis indicates that the optimum calcination temperature of the synthesised powder is 1100 °C. XRD result shows that the calcined powder exists as a single cubic phase without any secondary phase with the lattice parameter (a) of 4.332 Å. FESEM analysis confirms that the powder is homogeneous and uniform, with an average particle size of 51 ± 16 nm. The specific surface area of the calcined powder measured by the Brunauer–Emmett–Teller (BET) technique is 6.25 m2/g. The thickness, porosity, electrical conductivity and electrochemical performance of the screen-printed anode are measured as a function of sintering temperature (1200–1400 °C). The thickness of the sintered anodes after the reduction process decreases from 28.95 μm to 26.18 μm and their porosity also decreases from 33.98% to 26.93% when the sintering temperature increases from 1200 °C to 1400 °C. The electrical conductivities of the anodes sintered at 1200 °C, 1300 °C and 1400 °C are 443 S/cm, 633 S/cm and 1124 S/cm at 800 °C, respectively. Electrochemical studies showed that the anode sintered at 1400 °C shows the lowest area specific resistance (ASR) of 1.165 Ω cm2 under a humidified (3% H2O) gas mixture of H2 (10%) and N2 (90%) at 800 °C. Further improvement of the anode’s performance can be achieved by considering the properties of the screen-printing ink used for its preparation.

The potential of Ni–Cu–Mn spinels as methane reforming catalysts for hydrocarbon-fueled solid oxide fuel cell (SOFC) applications is highly dependent on its catalytic properties, particularly reducibility. The reducibility of a spinel-structured catalyst is often correlated with its structural properties and fabrication processes. In this work, the structural properties and reducibility of a Ni–Cu–Mn spinel catalyst was evaluated on the basis of mixing time during the glycine–nitrate process. Phase analysis results showed that Ni0.4Cu0.6Mn2.0O4 and (Cu, Mn)3O4 in normal or inversed spinel structures were observed in GNP-produced Ni–Cu–Mn spinel catalyst powders. Distortion in inverse spinel structures enhanced the reducibility of the spinel catalyst. Morphological analysis results showed that complete nitrate binding occurred at a minimum mixing time of 24 h and resulted in homogenous particle size distribution and uniform elemental distribution. Furthermore, the Ni–Cu–Mn spinel catalyst produced after 24 h of mixing was fully reduced at 450 °C. The reducing pattern of the Ni–Cu–Mn spinel catalyst produced after 24 h of mixing time showed strong metal–support interaction and the fast adsorption of reactants. These effects were due to either the distribution of divalent cations in octahedral sites or large amounts of bulk pores. In conclusion, a minimum mixing time of 24 h is sufficient to produce the desired structural properties and reducibility of Ni–Cu–Mn spinel catalysts for SOFC applications.

In this study, Ce0.85-xLa0.15CaxO2-δ was synthesized using sol-gel combustion method and appliedfor partial oxidation of methane (POM). The physicochemical properties of catalyst were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and thermogravimetric analysis (TGA). Material shows a pure cubical structure and is highly stable up to 850 °C. The performance testing indicated the conversion of CH4 is 65% and selectivity of H2 and CO are 28% and 8%, respectively. The performance indicated the catalyst has a potential to be used for partial oxidation of methane on a larger scale. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

This study aimed to investigate the colloidal stability of (Cu,Mn,Co)3O4 spinel in various suspension media and suitable applied voltage for electrophoretic deposition (EPD). The performance of the coated SUS430 was evaluated in terms of oxidation behaviour, Cr migration and electrical conductivity. The (Cu,Mn,Co)3O4 suspension prepared using a mixture of 50/50 isopropanol and acetylacetone presented the highest zeta potential (41.4 mV), which indicated a stable and well-dispersed suspension. An applied voltage of 80 V is recommended to produce a coating surface with uniform particle arrangement. The electrophoretically deposited (Cu,Mn,Co)3O4 spinel coating could reduce the oxidation kinetics by three orders of magnitude and exhibited stable electrical conductivity during 200 h of oxidation. Cr element was not detected on the surface of the coated SUS430 and LSCF cathode after 200 h of oxidation. Therefore, the electrophoretically deposited (Cu,Mn,Co)3O4 spinel coating could successfully inhibit Cr migration from the stainless steel interconnects to the cathode.

Solid oxide fuel cell (SOFC) is a promising technology to generate clean electricity to the environment with large scale application. However, the high operating temperature has several negative impacts such as faster material degradation and high operating cost. Therefore, it is desirable to reduce the operating temperature to intermediate temperature range (600–800 °C). La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) is an attracting and promising material to be used as cathode for intermediate temperature solid oxide fuel cell (IT-SOFC) due to its exceptional properties such as high electrical conductivity and high catalytic activity toward the oxygen reduction reaction (ORR). Infiltration of NiO within LSCF structure is foreseen to enhance the physical and electrochemical properties for IT-SOFC). Thus, this study utilizes modified sol–gel for the preparation of LSCF and NiO from metal nitrates and calcine temperature range from 600 °C to 900 °C. A sample consists of 1:1 ratio of LSCF and NiO was used for characterization with XRD and TGA/DTA. XRD result proved high purity of LSCF-NiO and increase in crystal size with increase in calcining temperature. TGA/DTA result shows that removal of organic compound occurs at 200–400 °C with peak at 250 °C and the perovskite completely formed at 650 °C. SEM result obtain similar pattern with XRD analysis where increment in calcining temperature increase the crystal size for the samples. Therefore, sample calcined at 700 °C and above have excellent properties for IT-SOFC application.

Gadolinium doped cerium (Ce0.9Gd0.1O1.95 or GDC10) was successfully synthesized using the solid-state method. Commercially available CeO2 and Gd2 O3 powders were used as starting materials. They were mixed in a ball mill where alumina balls were added as grinding medium with the ratio to powders as of 1:2. The obtained powders were dried and then calcined at temperatures of 600, 700 and 800 °C, respectively. The objective of this research was to investigate the effects of calcination temperature on the properties of GDC10. The powders were characterized using XRF, TGA, XRD, and PSA instruments. XRF analysis shows the presence of Ce, Gd and O elements in stoichiometric composition without any impurities. XRD analysis showed single phase structure of CeO2 where the crystallite size and lattice parameter increases and decreases, respectively, as the calcination temperature increases. The smallest particle size of 647.3 nm was obtained at the calcination temperature of 600 °C. The density of all GDC10 samples sintered at 1350 °C was found to be higher than 95%. In addition, the calcination temperature also influenced the ionic conductivity where the highest obtained value was 0.0153 S.cm-1 at 800 °C for the sample calcinaed at 600 °C. The results suggest that the calcination temperature affected the properties of GDC10 for solid oxide fuel cell application.

Sifat penguraian terma dan pembentukan fasa bahan lantanum strontium kobalt oksida, La0.6Sr0.4CoO3-δ (LSC) yang disediakan melalui kaedah sol-gel berbantu agen kimia berbeza, iaitu agen serakan, agen pempolimeran dan agen permukaan aktif atau surfaktan telah dicirikan secara sistematik masing-masing melalui analisis termogravimetrik (TG) dan pembelauan sinar-X (XRD). Penguraian terma bahan organik dan bahan bukan organik yang tidak diperlukan dalam serbuk pelopor bahan LSC telah lengkap pada suhu kurang daripada 1000 °C bagi serbuk pelopor yang disediakan dengan menggunakan agen serakan dan agen pempolimeran, dan suhu melebihi 1000 °C bagi serbuk pelopor yang disediakan dengan menggunakan surfaktan. Sifat penguraian terma ini dipengaruhi oleh suhu pengeringan serbuk pelopor tersebut dan berat molekul agen kimia. Pembentukan fasa tunggal perovskit LSC telah disahkan dalam serbuk pelopor yang disediakan dengan menggunakan agen serakan, iaitu karbon teraktif dan agen pempolimeran, iaitu etilena glikol selepas serbuk pelopor tersebut dikalsin pada suhu 900 °C. Sebaliknya, fasa tunggal perovskit LSC tidak terbentuk secara lengkap dalam serbuk pelopor yang disediakan dengan menggunakan surfaktan (polietilena glikol, Triton-X-100, Brij-97 dan Tween-80) walaupun selepas serbuk pelopor tersebut telah dikalsin pada suhu yang lebih tinggi iaitu 1100 °C. Kepekatan surfaktan, nisbah molar surfaktan kepada logam kation dan nilai pH larutan bahan pelopor yang tidak sesuai telah menyumbang kepada keputusan tersebut.

A composite cathode exhibits low activation polarisation by spreading its electrochemically active area within its volume. Composite cathodes enable the development of high-performance electrodes for solid oxide fuel cells (SOFCs) at intermediate temperatures (600 °C – 800 °C) because of their significant role in determining the kinetics of oxygen reduction reaction (ORR). Few anions O2− are transferred through the electrolyte component when the ORR is low, thereby lowering the reaction with cation H+ from an anode side to transfer electrons along the outer circuit to the cathode side to participate in ORR. The resistance to the ORR at the cathode is minimised, thereby contributing to performance degradation and efficiency loss in existing SOFCs, especially at intermediate temperatures. The suitability and compatibility of the cathode and electrolyte are crucial in the development of cathodes and electrochemical reactions. The intercomponent compatibility is important to ensure the robustness and durability of SOFCs, especially at an operating temperature around 800 °C, at which the components experience extreme thermal and mechanical stresses. Composite cathodes are used to improve cathode performance. These composite cathodes help enhance the properties of mixed electronic–ionic conductors and the intercomponent compatibility. Herein, we reviewed historical data of composite-cathode development for SOFCs, including its basic principle and criteria. The overall performance of as-synthesised composite cathodes in terms of microstructure, electrochemical reaction and intercomponent compatibility is briefly discussed.

A conventional reactor in microbial electrochemical technology (MET) consists of anode and cathode compartments divided by a separator, which is usually a proton exchange membrane (PEM), such as Nafion 117. In this study, a novel porous clay earthenware (NCE) was fabricated as the separator to replace the highly cost PEM. The fabrication of NCEs is with raw clay powder and starch powder that acts as a pore-forming agent at different starch powder contents (10 vol%, 20 vol%, and 30 vol%), ball-milled before hydraulically pressed to form green ceramic pellets and sintered up to 1200 °C. The highest power density of 2250 ± 21 mW/m2 (6.0 A/m2), the internal resistance of 75 ± 24 Ω and coulombic efficiency (CE) of 44 ± 21% were produced for MFC–NCE from 30 vol% starch powder content under batch mode operation. The MFC–PEM combination produced the lowest power density, CE and the highest internal resistance up to 1350 ± 17 mW/m2 (3.0 A/m2), 23 ± 15% and 326 ± 13 Ω, respectively.

In the last few decades, photocatalysis has been found to be a practical, environmentally friendly approach for degrading various pollutants into non-toxic products (e.g., H2O and CO2) and generating fuels from water using solar light. Mainly, traditional photocatalysts (such as metal oxides, sulfides, and nitrides) have shown a promising role in various photocatalysis reactions. However, it faces many bottlenecks, such as a wider band gap, low light absorption nature, photo-corrosion issues, and quick recombination rates. Due to these, a big question arises of whether these traditional photocatalysts can meet increasing energy demand and degrade emerging pollutants in the future. Currently, researchers view heteroanionic materials as a feasible alternative to conventional photocatalysts for future energy generation and water purification techniques due to their superior light absorption capacity, narrower band gap, and improved photo-corrosion resistance. Therefore, this article summarizes the recent developments in heteroanionic materials, their classifications based on anionic presence, their synthesis techniques, and their role in photocatalysis. In the end, we present a few recommendations for improving the photocatalytic performance of future heteroanionic materials.

Cobalt-free SrFe0·8Ti0·2O3-δ cathode powders were synthesized through the combustion method. Results of thermogravimetric and Fourier transform infrared analyses suggested that a perovskite oxide started to form at temperatures above 1100 °C. X-ray diffraction and Rietveld refinement analyses confirmed that the single-phase cubic structure (Pm-3m) of the SrFe0·8Ti0·2O3-δ cathode was produced after calcination at 1300 °C. The average sizes of the particles were 1.0827 and 1.4438 μm as revealed by field emission scanning electron microscopy and dynamic light scattering analysis, respectively. In addition, energy dispersive X-ray analysis coupled with mapping revealed the homogeneous distribution of elements in the cathode. The thermal expansion coefficient of the SrFe0·8Ti0·2O3-δ cathode is 16.20 × 10−6 K−1. For the electrochemical behavior, the area specific resistance of cathode (0.60–13.57 Ω cm2) was obtained at 600–800 °C, and the activation energy was 121.77 kJ mol−1. This work confirmed the potential of a SrFe0·8Ti0·2O3-δ cathode in the intermediate temperature solid oxide fuel cell.

Solid oxide fuel cell (SOFC) technology is attractive for its high-energy efficiency and expanded fuel flexibility. It is also more environmentally benign than conventional power generation systems. Recently, increasing attention has been paid to intermediate-to-low-temperature solid oxide fuel cells, which operating at 400–800 °C. Reducing its operating temperature can render SOFC more competitive with other types of fuel cells and portable energy storage system (EES) over a range of applications (eg: transportation, portable, stationary) and more conducive for commercialization. The high-performance composite anode requirements for low operating temperature (400–600 °C) demand microstructural and chemical stability, high electronic conductivity, and good electrochemical performance. The current high-temperature anode, Ni-YSZ (nickel-yttria stabilized zirconia) is generally reported with high interfacial resistance at reduced temperatures. This review highlights several potential composite anode materials (Ni-based and Ni-free) that have been developed for low-temperature SOFCs within the past 10 years. This literature survey shows that most of these anodes still exhibit relatively high polarization resistance. Focus is also given on reducing polarization resistance to maintain the cell power density. In literature, common approaches that have been adopted to enhance the performance of anodes are (i) selecting high-performance electrolyte, (ii) exploiting nanopowder properties, and (iii) adding noble metals as electrocatalysts.

Conductive polymer composite (CPC) materials are extensively used for the bipolar plate in Polymer Electrolyte Membrane Fuel Cells (PEMFCs). The produced CPC materials through the extrusion process strongly relate to electrical conductivity and mechanical properties. In this study, milled carbon fibre (MCF) reinforced polypropylene (PP) incorporating carbon nanotube (CNT), or graphene nanoplatelets (xGNP) are pre-mixed using the extrusion process to orientate the fibres before undergoing the compression moulding at 13.8 MPa and 200 °C for 15 min. The CNT composites exhibited the higher through-plane conductivity of 14.8 S/cm as compared to xGnP composites with 4.9 S/cm at 70 wt% of MCF. The flexural strength improved after being compressed to 99.6 MPa and 172.5 MPa for 70 wt% of CNT and xGNP, respectively. This reveals that the oriented fibres can boost the CPC performance.

Titanium, Ti-doped SrFe1-xTixO3-δ (x = 0.1–0.5) perovskite-structured ceramics were synthesized via solution combustion. The structural, morphological, and electrochemical behaviors of the as-synthesized materials were investigated to determine the applicability of SrFe1-xTixO3-δ as a cobalt-free cathode material for intermediate-temperature solid oxide fuel cells. X-ray diffraction analysis confirmed the formation of a single-phase cubic perovskite structure. The unit volume of this perovskite structure increased as the amount of Ti dopant increased. Morphological analysis revealed that the porosity of the SrFe1-xTixO3-δ perovskite cathode film was inversely proportional to the amount of Ti dopant. The cathode SrFe0·9Ti0·1O3-δ film exhibited a high porosity of 24.74 ± 0.52%, a low but acceptable hardness value of 0.70 ± 0.01 GPa and an area specific resistance of 0.57 Ω cm2. These results suggested that cobalt-free SrFe1-xTixO3-δ cathode was still not good enough to be compared with the existing cobalt-containing cathode such as lanthanum strontium cobalt ferrite. But, the results obtained from this work can be considered as a major turning point as the literature works on SrFe1-xTixO3-δ cathode showed excellence electrochemical performance. The contradict result between the present and past studies proved that the use of SrFe1-xTixO3-δ cathode is worthy of being studied into details to confirm its capability.

Gasification of coconut shell (CS) and palm kernel shell (PKS) is conducted in a batch type downdraft fixed-bed reactor to evaluate the effect of particle size (1–3 mm, 4–7 mm, and 8–11 mm) and temperature (700, 800, and 900 °C) on gas composition and gasification performance. The response surface methodology integrated variance-optimal design is used to identify the optimum condition for gasification. Gas composition, which is measured using the biomass particle size of 1–11 mm at 700–900 °C, are 8.20–14.6 vol% (H2), 13.0–17.4 vol% (CO), 14.7–16.7 vol% (CO2), and 2.82–4.23 vol% (CH4) for CS and 7.01–13.3 vol% (H2), 13.3–17.8 vol% (CO), 14.9–17.1 vol% (CO2), and 2.39–3.90 vol% (CH4) for PKS. At similar conditions, the syngas higher heating value, dry gas yield, carbon conversion efficiency, and cold gas efficiency are 4.01–5.39 MJ/Nm3, 1.50–1.95 Nm3/kg, 52.2–75.9%, and 30.9–56.4% for CS, respectively, and 3.82–5.09 MJ/Nm3, 1.48–1.92 Nm3/kg, 59.0–81.5%, and 33.0–57.1% for PKS, respectively. Results reveal that temperature has a greater role than particle size in influencing the gasification reaction rate.

Pengoksidaan antarahubung berasaskan bahan keluli tahan karat SUS430 dalam sel fuel oksida pepejal (SFOP) bersuhu sederhana menyumbang kepada pembentukan lapisan oksida yang mengandungi spesies kromium (Cr) meruap (volatile Cr species) di sekeliling komponen tersebut. Bagi tempoh operasi yang panjang, pemeruapan spesies Cr ini menyebabkan keracunan kromium pada komponen katod yang bersentuhan dengan permukaan antarahubung SUS430. Sehingga kini, katod La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) merupakan calon terbaik bagi katod SFOP bersuhu sederhana. Justeru, kajian ini bertujuan untuk mengenal pasti kesan jangka panjang pengoksidaan keluli SUS430 terhadap pembentukan spesies Cr meruap dan menentukan pengaruh pemeruapan Cr ke atas prestasi komponen katod LSCF. Hasil kajian menunjukkan bahawa pengoksidaan keluli SUS430 selama 200 jam membawa kepada pertambahan berat secara parabolik yang berkait dengan mekanisme pertumbuhan sisik oksida. Sisik ini terdapat dua lapisan iaitu spinel di bahagian atas diikuti lapisan kromia dan dilihat tidak memberi kesan signifikan pada kekonduksian SUS430. Walau bagaimanapun, pengendapan Cr pada permukaan katod LSCF menyebabkan pertumbuhan hablur SrCrO4 dan Cr2O3. Pembentukan tersebut bukan sahaja mengurangkan aktiviti pemangkinan seperti penurunan oksigen dan meningkatkan rintangan elektrik, malah meningkatkan tenaga pengaktifan akibat peningkatan kepekatan kekosongan oksigen. Justeru, penghadangan pemeruapan Cr terbukti amat penting untuk mengekalkan kestabilan jangka panjang SFOP bersuhu sederhana.

The performance of low-to-intermediate temperature (400–800 °C) solid oxide fuel cells (SOFCs) depends on the properties of electrolyte used. SOFC performance can be enhanced by replacing electrolyte materials from conventional oxide ion (O2-) conductors with proton (H+) conductors because H+ conductors have higher ionic conductivity and theoretical electrical efficiency than O2- conductors within the target temperature range. Electrolytes based on cerate and/or zirconate have been proposed as potential H+ conductors. Cerate-based electrolytes have the highest H+ conductivity, but they are chemically and thermally unstable during redox cycles, whereas zirconate-based electrolytes exhibit the opposite properties. Thus, tailoring the properties of cerate and/or zirconate electrolytes by doping with rare-earth metals has become a main concern for many researchers to further improve the ionic conductivity and stability of electrolytes. This article provides an overview on the properties of four types of cerate and/or zirconate electrolytes including cerate-based, zirconate-based, single-doped cerate–zirconate and hybrid-doped cerate–zirconate. The properties of the proton electrolytes such as ionic conductivity, chemical stability and sinterability are also systematically discussed. This review further provides a summary of the performance of SOFCs operated with cerate and/or zirconate proton conductors and the actual potential of these materials as alternative electrolytes for proton-conducting SOFC application.

Ceramics powders based on cerate-zirconate such as yttrium-doped barium cerate-zirconate, BaCe0.54Zr0.36Y0.1O3 (BCZY) have been used as electrolyte materials for proton-conducting fuel cell (PCFC) application. High purity of the ceramics powders are traditionally prepared by solid state reaction (SSR) method at a high processing temperature (> 1400 °C). Alternatively, sol-gel (SG) technique and high pressure – high temperature (HP-HT) batch wise reactor system using supercritical fluids (SCFs) method are introduced to synthesis the powders at a lower temperature. To achieve the goals in producing the ceramics powders with better properties than SSR method, few critical parameters for both SG and SG assisted SCFs methods are determined. This study reports the effects of different chemical agents (chelating agent and surfactant) in SG method and the effects of pressure and temperature of HP-HT batch wise reactor system using ethanol as solvent on the phase purity and microstructure of the BCZY powders. Chelating agent (triethylenetetramine, TETA) and surfactant (Brij-97) aided to produce a single perovskite phase of BCZY at calcination temperatures of 1100 °C and 950 °C, respectively. On the other hand, a single perovskite phase of BCZY was obtained via SCFs assisted with sol-gel (SG-SCFs) method. The optimum characteristics of BCZY powder was found in the one prepared at P = 2 MPa and T = 150 °C and 200 °C. Particles of the powders produced by SG and SG-SCFs methods are spherical in-shape. As proven, SG method is able to produce better phase purity and homogenize BCZY powder at lower processing temperature that meets criteria to be used as an electrolyte material.

This study mainly aimed to elucidate the effects of strontium co-doping on the structural, optical, and electrical properties of erbium-doped ceria (Ce0.8Er0.2O2-δ). Ce1-x-yErxSryO2-δ co-doped electrolytes were synthesized through sol–gel-assisted citric acid–nitrate combustion technique and sintered at 1500 °C for 6 h. X-ray diffraction results confirmed that the sintered electrolytes possessed a cubic fluorite crystal structure. However, a perovskite secondary phase (SrCeO3) was observed in Ce0.8Er0.125Sr0.075O2-δ co-doped composition due to the low solubility limit of strontium (~5 mol%) in ceria. UV–Vis spectroscopy showed that the co-doping of strontium from 0 mol% to 7.5 mol% increased the direct band gap from 3.41 eV to 3.43 eV. The relative densities and the grain size were in the range of 96.02–97.68% and 1.5–3.28 µm, respectively, with increasing the strontium content from 0 mol% to 7.5 mol%. Electrochemical impedance spectroscopy showed that the total resistance of Ce0.8Er0.2O2-δ increased as the strontium content increased. Singly doped Ce0.8Er0.2O2-δ electrolyte exhibited the highest ionic conductivity of 18.22 mS/cm at 700 °C and the lowest activation energy of 0.55 eV within 600–800 °C among all other studied electrolytes.

Bipolar plates significantly contribute to the development of the polymer electrolyte membrane (PEM) fuel cells technology due to their ability to produce high electrical conductivity based on the type of materials used. Mismatching of inappropriate materials and manufacture may lead to the inferior performance of PEM fuel cells. Hence, material development was determined crucial to balance the overall performance of PEM fuels including the mechanical properties and electrical conductivity of the materials. Studies on conductive polymer composites (CPCs) offered filler with orientation in terms of filler with aspect ratio and shape as an alternative method to enhance the overall performance of the bipolar plate. Filler orientations permit an excellent conductivity network formation while controlling the filler alignment based on required applications. This paper reviewed various studies of filler orientations including materials used and methods of manufacture of CPC materials for the effective development of bipolar plate. The technique to orientate the filler was highlight in terms of materials processing and its effects on the materials performance.

The effect of current collecting layer (CCL) and cathode functional layer (CFL) thicknesses on the catalytic activity of the La0.6Sr0.4Co0.2Fe0.8O3-δ-Ce0.8Sm0.2O1.9 (LSCF-SDC) composite cathode was investigated by electrochemical impedance spectroscopy at 600 °C for 100 h. Results revealed that the charge transfer process associated with the incorporation of O2− ions and the surface oxygen reduction reaction rate are dependent on CFL and CCL thicknesses, respectively. Area-specific resistance is dependent on CCL thickness in high-frequency arcs and on CFL thickness in low-frequency arcs. No significant change was observed in area-specific resistance value as the thickness of LSCF CCL decreased (25–5 μm) while the LSCF-SDC CFL thickness (5-25 μm) was gradually increased. However, the LSCF-SDC composite cathode (without CCL) showed poor catalytic activity toward the oxygen reduction reaction and had a high area-specific resistance value (3.31 Ω cm2). When LSCF CCL (5 μm) was used, the area-specific resistance value decreased by 16 times relative to the ASR of a sample without CCL. The field emission scanning electron microscopy results indicated that these cathodes exhibited a clear change in microstructure on the surface of the LSCF CCL after 100 h of thermal treatment in oxygen. The particle agglomeration and Sr surface segregation affected the surface catalytic activity toward oxygen reduction reaction at the LSCF CCL. As a result, the ASR value increased gradually in 100 h thermal treatment.

Three different series of doped ceria-based composite electrolyte consisting of M-doped ceria (M = Ce0.85Er0.15O2-δ (ErDC), Ce0.85La0.15O2-δ (LaDC) and Ce0.95Sr0.05O2-δ (SrDC)) and ternary carbonate (mixture of Li2CO3, Na2CO3 and K2CO3) were developed as functional solid electrolytes for low-temperature solid oxide fuel cells. X-ray diffraction, transmission electron microscopy and UV–visible spectroscopy were used to analyze the chemical stability, morphology, and bandgap, respectively, of the prepared composite powders. All composite electrolytes exhibited cubic fluorite structure as a primary phase and small peaks corresponding to (Li/Na/K)2CO3 as an amorphous phase. The bulk densities of the sintered composite electrolyte pellets were in the range of 3.34 g/cm3–3.45 g/cm3. The total conductivity of the composite electrolyte materials was evaluated by electrochemical impedance spectroscopy in air and hydrogen (90 vol% N2 + 10 vol% H2) in the temperature range of 350 oC–650 °C. The SrDC-ternary carbonate composite electrolyte showed the highest conductivity of 0.092 Scm−1 and lowest activation energy at 650 °C in hydrogen. The formation of hydrated phase from chemical interaction between the carbonates and hydrogen gas and the presence of Sr2+ and cerium ions is useful in enhancing the proton conduction in the SrDC-ternary carbonate system.

An excellent oxide ion conductivity with high oxygen transportation of lanthanum silicate apatite at the solid oxide fuel cell (SOFC) can be achieved through the solid-state reaction method. The doped La10Si6−x−0.2AlxZn0.2O27−δ (x = 0.2 and 0.4) materials sintered at 1600°C accomplished crystallinity and crystal structure of apatite-type. The structural and electrochemical characterizations of La10Si6−x−0.2AlxZn0.2O27−δ (x = 0.2 and 0.4) were executed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS) measurements. The total oxide ion conductivities of La10Si6−x−0.2AlxZn0.2O27−δ (x = 0.2 and 0.4) were measured from low to intermediate operating temperature range (450 to 800°C) using electrochemical impedance spectroscopy. Room temperature XRD patterns of La10Si6−x−0.2AlxZn0.2O27−δ (x = 0.2 and 0.4) exhibited La10Si6O27 apatite phase with space group P63/m as the main phase with the minor appearance of La2SiO5 as an impurity phase. The highest total oxide ion conductivity of 3.24 × 10−3 Scm−1 and corresponding activation energy of 0.30 eV at 800°C were obtained for La10Si5.6Al0.2Zn0.2O26.7 which contains a low concentration of Al3+ dopant.

Perovskite-based composite cathodes, La0.6Sr0.4Co0.2Fe0.8O3-&delta, (LSCF)&ndash, Ce0.8Sm0.2O1.9-carbonate (SDCC), were investigated as cathode materials for low-temperature solid-oxide fuel cells. The LSCF was mixed with the SDC&ndash, carbonate (SDCC) composite electrolyte at different weight percentages (i.e., 30, 40, and 50 wt %) to prepare the LSCF&ndash, SDCC composite cathode. The effect of SDCC composite electrolyte content on the diffraction pattern, microstructure, specific surface area, and electrochemical performances of the LSCF&ndash, SDCC composite cathode were evaluated. The XRD pattern revealed that the SDCC phase diffraction peaks vary according to its increasing addition to the system. The introduction of SDCCs within the composite cathode did not change the LSCF phase structure and its specific surface area. However, the electrical performance of the realized cell drastically changed with the increase of the SDCC content in the LSCF microstructure. This drastic change can be ascribed to the poor in-plane electronic conduction at the surface of the LSCF cathode layer due to the presence of the insulating phase of SDC and molten carbonate. Among the cathodes investigated, LSCF&ndash, 30SDCC showed the best cell performance, exhibiting a power density value of 60.3&ndash, 75.4 mW/cm2 at 600 &deg, C to 650 &deg, C.

Solid oxide fuel cells (SOFCs) are energy conversion technologies known for their excellent efficiency and high energy density. However, the application of SOFCs is restrained by their high operating temperatures (800–1000 °C), which result in overall energy system degradation. Reducing the operating temperatures of SOFCs leads to a reduction in power density because of insufficient protonic–ionic conduction. Ionic conduction at the cathode component is related to polarization and area-specific resistance that varies following the selected material. To date, several types of cathode materials have been investigated, namely, pure electronic conductor, mixed protonic–electronic conductor, mixed ionic–electronic conductor (MIEC) and triple protonic–electronic–ionic conductor (THOEC). Amongst these conductors, MIEC and THOEC currently lead in research development and application in conventional and proton-conducting intermediate–low-temperature SOFCs, yet further studies need to be carried out to ensure the continuous improvement of these materials as SOFC cathode. In this review, an explanation on the different types of cathodes will be discussed, with emphasis on MIEC- and THOEC-based cathodes. This review also includes recent progress and challenges encountered for both materials in the SOFC environment.

This paper reviews recent progress in electrophoretic deposition (EPD), particularly in solid oxide fuel cells (SOFCs). EPD is a simple, cost-effective, and geometrical flexible colloidal process. With its excellent control of thickness and other morphological characteristics, it is favored for the fabrication of SOFCs because each component layer of an SOFC has different requirements. However, the effectiveness of EPD is closely related to the suspension stability and EPD processing parameters. Maintaining a stable suspension and optimizing the EPD processing parameters are essential to achieve a dense and uniform deposition layer. Key parameters in maintaining the suspension stability are generally categorized into colloidal related parameters, including particle size and solid loading, and suspension media related parameters, including dielectric constant and conductivity. The effects of these parameters are often reflected by the zeta potential of the suspension, which can be manipulated by using charging agents to maintain a stable state. The deposition time and applied voltage are key parameters in optimizing the EPD process through their effects on the deposition rate. The effects of these parameters on particle surface charges and on the EPD mechanism are discussed.

This Extrusion permit in controlling electrical conductivity before composite materials undergo the manufacturing process. However, studies on electrical conductivity in high conductive polymer composite materials are still in preliminary stage. Thus, the studies on electrical conductivity model are crucial as it able in predicting the electrical conductivity hence minimizing the experimental conducted. In this study, conductivity model was conducted to validate the series of experiment. The electrical conductivity increases as shear rate decrease and the highest electrical conductivity of 3 S/cm is obtained which indicated that the shear rate is crucial in increasing the electrical conductivity of the composites compared to extrusion temperature hence it is consider in the modelling.