Synthesis and Structural Study of a Novel La0.67Ca0.33Cr0.9Cu0.1O3-δ Anode for Syngas-Fuelled Solid Oxide Fuel Cell

Solid oxide fuel cell (SOFC) is an alternative energy generation device that converts chemical energy into electrical energy from the use of hydrogen or hydrogen-rich fuel. A light hydrocarbon, e.g. methane (CH4), is a hydrogen-rich fuel that can be used as an alternative fuel to hydrogen in SOFC application. Carbon-containing fuel is accessible from natural gas, biogas, biomass gasification, etc. Biomass gasification produces methane, hydrogen (H2), etc. as syngas products which could be integrated with SOFC. As anode is an outer layer of SOFC which exposes to fuel, the development of anode for carbon-containing fuel application is essential. Conventional Ni-containing anode is found to create carbon deposition which degrades the cell. The replacement of copper (Cu) to Ni has been studied to enhance the direct electrochemical oxidation of dry hydrocarbons which is free from carbon deposition. With the interest of Cu doping, a La-based anode has been doped with 10 % Cu at B-site of perovskite structure as La0.67Ca0.33Cr0.9Cu0.1O3-δ and studied the X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) for future application in syngas-fuelled SOFC

Electrochemical Performance of SrWO4 Electrolyte for SOFC

Scheelite structured SrWO4 material was synthesized by the solid-state sintering method and studied with respect to phase stability and ionic conductivity under condition of technological relevance for SOFC applications. The resulting compound was crystallized in the single phase of tetragonal scheelite structure with the space group of I41/a. Room temperature X-ray diffraction and subsequent Rietveld analysis confirms its symmetry, space group and structural parameters. Analysis by SEM illustrated a highly dense structure. SrWO4 sample shows lower conductivity compared to the traditional BCZY perovskite structured materials. SrWO4 sample exhibited an ionic conductivity of 1.93 × 10−6 S cm-¹ at 1000℃ in dry Ar condition. Since this scheelite type compound demonstrated significant conductivity and a dense microstructure, it could serve in SOFC as a mixed ion-conducting electrolyte

A new high-performance proton-conducting electrolyte for next-generation solid oxide fuel cells

N. Radenahmad and A. Afif are thankful to Universiti Brunei Darussalam for sponsoring the UBD graduate scholarship to perform Ph.D. work at Brunei Darussalam. The authors are also grateful to the late Professor Sten Eriksson for supporting a summer scholarship for NR to accomplish a part of this work at Chalmers University of Technology, Sweden. This work was also partially funded by research grant UBD/OVAORI/CRGWG(006)/161201.Conventional solid oxide fuel cells (SOFCs) are operable at high temperatures (700 – 1,000 °C) with the most commonly used electrolyte, yttria‐stabilized zirconia (YSZ). SOFC R&D activities have thus been carried out to reduce the SOFC operating temperature. At intermediate temperatures (400 – 700 °C), barium cerate (BaCeO3) and barium zirconate (BaZrO3) are good candidates for use as proton‐conducting electrolytes due to their promising electrochemical characteristics. Here, we combined two widely studied proton‐conducting materials with two dopants and discovered an attractive composition for the investigation of electrochemical behaviors. Ba0.9Sr0.1Ce0.5Zr0.35Y0.1Sm0.05O3‐δδ(BSCZYSm), a perovskite‐type polycrystalline material, has shown very promising properties to be used as proton‐conducting electrolytes at intermediate temperature range. BSCZYSm shows a high proton conductivity of 4.167×10−3 S cm−1 in a wet argon atmosphere and peak power density of 581.7 mW cm−2 in Ni‐BSCZYSm | BSCZYSm | BSCF cell arrangement at 700 °C, which is one of the highest in comparison to proton‐conducting electrolyte‐based fuel cells reported till now.PostprintPeer reviewe

Enhancement of proton conductivity through Yb and Zn doping in BaCe0.5Zr0.35Y0.15O3-δ electrolyte for IT-SOFCs

The new compositions of BaCe0.5Zr0.3Y0.15-xYbxZn0.05O3-δ perovskite electrolytes (x = 0.1 and 0.15) were prepared by solid state synthesis and final sintering at 1500 °C. The obtained ceramics were investigated using X-ray diffraction, scanning electron microscopy, thermo-gravimetric analysis and impedance spectroscopy. The refinement of XRD data confirmed cubic crystal structure with Pm3m space group for both samples. SEM morphology showed larger and compacted grains which enables obtaining of high density and high protonic conductivity. The relative densities of the samples were about 99% of the theoretical density after sintering at 1500 °C. The protonic conductivities at 650 °C were 2.8×10-4 S/cm and 4.2×10-3 S/cm for x = 0.1 and 0.15, respectively. The obtained results showed that higher Yb-content increases the ionic conductivity and both of these perovskites are promising electrolyte for intermediate temperature solid oxide fuel cells to get high efficiency, long-term stability and relatively low cost energy system

Highly dense and chemically stable proton conducting electrolyte sintered at 1200 °C

The authors S. Hossain and A. M. Abdalla are grateful to the graduate studies office of Universiti Brunei Darussalam for graduate research scholarship (GRS) for funding this research. The authors are thankful to Professor John T. S. Irvine for managing a visiting scholarship for SH and AMA at Center for Advanced Materials at School of Chemistry in University of St Andrews, UK for the research works done.The BaCe0.7Zr0.1Y0.2−xZnxO3−δ (x = 0.05, 0.10, 0.15, 0.20) has been synthesized by the conventional solid state reaction method for application in protonic solid oxide fuel cell. The phase purity and lattice parameters of the materials have been studied by the room temperature X-ray diffraction (XRD). Scanning electron microscopy (SEM) has been done for check the morphology and grain growth of the samples. The chemical and mechanical stabilities have been done using thermogravimetric analysis (TGA) in pure CO2 environment and thermomechanical analysis (TMA) in Argon atmosphere. The XRD of the materials show the orthorhombic crystal symmetry with Pbnm space group. The SEM images of the pellets show that the samples sintered at 1200 °C are highly dense. The XRD after TGA in CO2 and thermal expansion measurements confirm the stability. The particles of the samples are in micrometer ranges and increasing Zn content decreases the size. The conductivity measurements have been done in 5% H2 with Ar in dry and wet atmospheres. All the materials show high proton conductivity in the intermediate temperature range (400–700 °C). The maximum proton conductivity was found to be 1.0 × 10−2 S cm−1 at 700 °C in wet atmosphere for x = 0.10. From our study, 10 wt % of Zn seems to be optimum at the B-site of the perovskite structure. All the properties studied here suggest it can be a promising candidate of electrolyte for IT-SOFCs.PostprintPeer reviewe

Improved mechanical strength, proton conductivity and power density in an ‘all-protonic’ ceramic fuel cell at intermediate temperature

The authors AA and NR would like to thank Universiti Brunei Darussalam for providing a UGS scholarship to perform this research. This work was supported by the UBD CRG project: UBD/OVACRI/CRGWG(006)/161201.Protonic ceramic fuel cells (PCFCs) have become the most efficient, clean and cost-effective electrochemical energy conversion devices in recent years. While significant progress has been made in developing proton conducting electrolyte materials, mechanical strength and durability still need to be improved for efficient applications. We report that adding 5 mol% Zn to the Y-doped barium cerate-zirconate perovskite electrolyte material can significantly improve the sintering properties, mechanical strength, durability and performance. Using same proton conducting material in anodes, electrolytes and cathodes to make a strong structural backbone shows clear advantages in mechanical strength over other arrangements with different materials. Rietveld analysis of the X-ray and neutron diffraction data of BaCe0.7Zr0.1Y0.15Zn0.05O3−δ (BCZYZn05) revealed a pure orthorhombic structure belonging to the Pbnm space group. Structural and electrochemical analyses indicate highly dense and high proton conductivity at intermediate temperature (400–700 °C). The anode-supported single cell, NiO-BCZYZn05|BCZYZn05|BSCF-BCZYZn05, demonstrates a peak power density of 872 mW cm−2 at 700 °C which is one of the highest power density in an all-protonic solid oxide fuel cell. This observation represents an important step towards commercially viable SOFC technology.Publisher PDFPeer reviewe

Enhancement of proton conductivity through Yb and Zn doping in BaCe0.5Zr0.35Y0.15O3-delta electrolyte for IT-SOFCs

The new compositions of BaCe0.5Zr0.3Y0.15-xYbxZn0.05O3-delta perovskite electrolytes (x = 0.1 and 0.15) were prepared by solid state synthesis and final sintering at 1500 degrees C. The obtained ceramics were investigated using X-ray diffraction, scanning electron microscopy, thermo-gravimetric analysis and impedance spectroscopy. The refinement of XRD data confirmed cubic crystal structure with Pm-3m space group for both samples. SEM morphology showed larger and compacted grains which enables obtaining of high density and high protonic conductivity. The relative densities of the samples were about 99% of the theoretical density after sintering at 1500 degrees C. The protonic conductivities at 650 degrees C were 2.8x10(-4) S/cm and 4.2x10(-3) S/cm for x = 0.1 and 0.15, respectively. The obtained results showed that higher Yb-content increases the ionic conductivity and both of these perovskites are promising electrolyte for intermediate temperature solid oxide fuel cells to get high efficiency, long-term stability and relatively low cost energy system

A new high-performance proton-conducting electrolyte for next-generation solid oxide fuel cells

Conventional solid oxide fuel cells (SOFCs) are operable at high temperatures (700 – 1,000 °C) with the most commonly used electrolyte, yttria‐stabilized zirconia (YSZ). SOFC R&D activities have thus been carried out to reduce the SOFC operating temperature. At intermediate temperatures (400 – 700 °C), barium cerate (BaCeO3) and barium zirconate (BaZrO3) are good candidates for use as proton‐conducting electrolytes due to their promising electrochemical characteristics. Here, we combined two widely studied proton‐conducting materials with two dopants and discovered an attractive composition for the investigation of electrochemical behaviors. Ba0.9Sr0.1Ce0.5Zr0.35Y0.1Sm0.05O3‐δδ(BSCZYSm), a perovskite‐type polycrystalline material, has shown very promising properties to be used as proton‐conducting electrolytes at intermediate temperature range. BSCZYSm shows a high proton conductivity of 4.167×10−3 S cm−1 in a wet argon atmosphere and peak power density of 581.7 mW cm−2 in Ni‐BSCZYSm | BSCZYSm | BSCF cell arrangement at 700 °C, which is one of the highest in comparison to proton‐conducting electrolyte‐based fuel cells reported till now