Asia Rafique

Significance enhancement in the conductivity of core shell nanocomposite electrolytes

Today, there is great demand of electrolytes with high ionic conductivities at low operating temperatures for solid-oxide fuel cells. Therefore, a co-doped technique was used to synthesize a highly ionically conductive two phase nanocomposite electrolyte Sr/Sm–ceria–carbonate by a co-precipitation method. A significant increase in conductivity was measured in this co-doped Sr/Sm–ceria–carbonate electrolyte at 550 °C as compared to the more commonly studied samarium doped ceria. The fuel cell power density was 900 mW cm−2 at low temperature (400–580 °C). The composite electrolyte was found to have homogenous morphology with a core–shell structure using SEM and TEM. The two phase core–shell structure was confirmed using XRD analysis. The crystallite size was found to be 30–60 nm and is in good agreement with the SEM analysis. The thermal analysis was determined with DSC. The enhancement in conductivity is due to two effects; co-doping of Sr in samarium doped ceria and its composite with carbonate which is responsible for the core–shell structure. This co-doped approach with the second phase gives promise in addressing the challenge to lower the operating temperature of solid oxide fuel cells (SOFC).

Alkaline earth metal and samarium co-doped ceria as efficient electrolytes

Co-doped ceramic electrolytes M0.1Sm0.1Ce0.8O2−δ (M = Ba, Ca, Mg, and Sr) were synthesized via co-precipitation. The focus of this study was to highlight the effects of alkaline earth metals in doped ceria on the microstructure, densification, conductivity, and performance. The ionic conductivity comparisons of prepared electrolytes in the air atmosphere were studied. It has been observed that Ca0.1Sm0.1Ce0.8O2−δ shows the highest conductivity of 0.124 Scm−1 at 650 °C and a lower activation energy of 0.48 eV. The cell shows a maximum power density of 630 mW cm−2 at 650 °C using hydrogen fuel. The enhancement in conductivity and performance was due to increasing the oxygen vacancies in the ceria lattice with the increasing dopant concentration. The bandgap was calculated from UV-Vis data, which shows a red shift when compared with pure ceria. The average crystallite size is in the range of 37–49 nm. DFT was used to analyze the co-doping structure, and the calculated lattice parameter was compared with the experimental lattice parameter.Co-doped ceramic electrolytes M0.1Sm0.1Ce0.8O2−δ (M = Ba, Ca, Mg, and Sr) were synthesized via co-precipitation. The focus of this study was to highlight the effects of alkaline earth metals in doped ceria on the microstructure, densification, conductivity, and performance. The ionic conductivity comparisons of prepared electrolytes in the air atmosphere were studied. It has been observed that Ca0.1Sm0.1Ce0.8O2−δ shows the highest conductivity of 0.124 Scm−1 at 650 °C and a lower activation energy of 0.48 eV. The cell shows a maximum power density of 630 mW cm−2 at 650 °C using hydrogen fuel. The enhancement in conductivity and performance was due to increasing the oxygen vacancies in the ceria lattice with the increasing dopant concentration. The bandgap was calculated from UV-Vis data, which shows a red shift when compared with pure ceria. The average crystallite size is in the range of 37–49 nm. DFT was used to analyze the co-doping structure, and the calculated lattice parameter was compared with the ...

Effect of Alkali Carbonates (Single, Binary, and Ternary) on Doped Ceria: A Composite Electrolyte for Low-Temperature Solid Oxide Fuel Cells

Samarium-doped ceria (SDC) carbonate has become an attractive electrolyte for fuel cells because of its remarkable ion conductivity and high performance. Different doped ceria-carbonate (single-carbonate SDC, binary-carbonate SDC, and ternary-carbonate SDC) electrolytes were synthesized by the coprecipitation/oxalate method, to optimize the electrochemical performance. The structure; morphology; and thermal, optical, and surface properties have been studied using a variety of techniques. The X-ray diffraction results confirmed the successful incorporation of samarium into ceria as a crystalline structure and inclusion of carbonate, which is amorphous in nature. To analyze the conduction mechanism, direct current conductivity was measured in a H2/O2 atmosphere. Doped ceria-binary carbonate ((Li/Na)CO3-SDC) showed the best conductivity of 0.31 S cm-1 and power density of 617 mW cm-2, at 600 °C. The enhancement in the ionic conductivity and performance of the composites is due to the contribution of hybrid ions (O2-, H+). The crystallite size of the composites was in the range 21-41 nm. For the calculation of band gaps, optical absorption spectra of the synthesized powders were analyzed, and they showed a red shift with the band gap energy in the range 2.6-3.01 eV, when compared to that of pure ceria (3.20 eV).

Low-temperature solid oxide fuel cells with bioalcohol fuels

Abstract Energy and environmental issues become key factors for sustainable development of society and national economy. Sustainable energy targeting opportunities for economic friendly growth of a country are commonly recognized. The growing interest is focused on the renewable energy resources because of the global energy demands increasing day by day. To meet the demands, an extensive research is aimed to develop sustainable energy devices such as solar cells, rechargeable batteries, and fuel cells. In recent years, solid oxide fuel cell (SOFC) among fuel-cell types has got more attention especially due to its fuel flexibility (e.g., different hydrocarbons, alcohols, and gasoline/diesel), high efficiency, and low emission. Thus, LTSOFC fed by direct bioethanol is receiving considerable attention as a clean, highly efficient for the production of both electricity and high-grade waste heat. These multifuel advantages provide the opportunities to develop an advanced SOFC system especially bioalcohol SOFC systems. This is a very dynamic area for SOFC applications with a promising future. It may create great energy savings and pollution reductions, if the bioalcohol fuel-based-technologies in these applications come into practical use. This chapter is focused on the development of LTSOFC operated by direct bioalcohol (bioethanol and biomethanol) for sustainable development. The content of this chapter is divided into three parts: (i) development of materials, (ii) characterization and analysis, (iii) demonstration of the nanocomposite materials in a bioalcohol FC, and (iv) case studies. Such bioalcohol FC research and development can enhance the use of sustainable/renewable energy for the society, and results achieved for applications have great potential to revolutionize the energy technology in an environmentally friendly and sustainable way.