Charge separation and transport in La0.6Sr0.4Co0.2Fe0.8O3-δ and ion-doping ceria heterostructure material for new generation fuel cell

Functionalities in heterostructure oxide material interfaces are an emerging subject resulting in extraordinary material properties such as great enhancement in the ionic conductivity in a heterostructure between a semiconductor SrTiO3 and an ionic conductor YSZ (yttrium stabilized zirconia), which can be expected to have a profound effect in oxygen ion conductors and solid oxide fuel cells [1–4]. Hereby we report a semiconductor-ionic heterostructure La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and Sm-Ca co-doped ceria (SCDC) material possessing unique properties for new generation fuel cells using semiconductor-ionic heterostructure composite materials. The LSCF-SCDC system contains both ionic and electronic conductivities, above 0.1 S/cm, but used as the electrolyte for the fuel cell it has displayed promising performance in terms of OCV (above 1.0 V) and enhanced power density (ca. 1000 mW/cm2 at 550 °C). Such high electronic conduction in the electrolyte membrane does not cause any short-circuiting problem in the device, instead delivering enhanced power output. Thus, the study of the charge separation/transport and electron blocking mechanism is crucial and can play a vital role in understanding the resulting physical properties and physics of the materials and device. With atomic level resolution ARM 200CF microscope equipped with the electron energy-loss spectroscopy (EELS) analysis, we can characterize more accurately the buried interface between the LSCF and SCDC further reveal the properties and distribution of charge carriers in the heterostructures. This phenomenon constrains the carrier mobility and determines the charge separation and devices’ fundamental working mechanism; continued exploration of this frontier can fulfill a next generation fuel cell based on the new concept of semiconductor-ionic fuel cells (SIFCs)

Perovskite SrFe1-xTixO3-δ (x < = 0.1) cathode for low temperature solid oxide fuel cell

© 2018 Elsevier Ltd and Techna Group S.r.l. Stable and compatible cathode materials are a key factor for realizing the low-temperature (LT, ≤600 °C) operation and practical implementations of solid oxide fuel cells (SOFCs). In this study, perovskite oxides SrFe 1-x Ti x O 3-δ (x < = 0.1), with various ratios of Ti doping, are prepared by a sol-gel method for cathode material for LT-SOFCs. The structure, morphology and thermo-gravimetric characteristics of the resultant SFT powders are investigated. It is found that the Ti is successfully doped into SrFeO 3-δ to form a single phase cubic perovskite structure and crystal structure of SFT shows better stability than SrFeO 3-δ . The dc electrical conductivity and electrochemical properties of SFT are measured and analysed by four-probe and electrochemical impedance spectra (EIS) measurements, respectively. The obtained SFT exhibits a very low polarization resistance (R p ),.01 Ωcm 2 at 600◦C. The SFT powders using as cathode in fuel cell devices, exhibit maximum power density of 551 mW cm −2 with open circuit voltage (OCV) of 1.15 V at 600◦C. The good performance of the SFT cathode indicates a high rate of oxygen diffusion through the material at cathode. By enabling operation at low temperatures, SFT cathodes may result in a practical implementation of SOFCs

Standardized procedures important for improving single-component ceramic fuel cell technology

Standardized procedures important for improving single-component ceramic fuel cell technolog

Promising electrochemical study of titanate based anodes in direct carbon fuel cell using walnut and almond shells biochar fuel

The direct carbon fuel cell (DCFC) is an efficient device that converts the carbon fuel directly into electricity with 100% theoretical efficiency contrary to practical efficiency around 60%. In this paper four perovskite anode materials La0.4Sr0.6M0.09Ti0.91O3-δ (M = Ni, Fe, Co, Zn) have been prepared using sol-gel technique to measure the performance of the device using solid fuel. These materials have shown reasonable stability and conductivity at 700 °C. Further structural analysis of as-prepared anode material using XRD technique reveals a single cubic perovskite structure with average crystallite size roughly 47 nm. Walnut and almond shells biochar have also been examined as a fuel in DCFC at the temperature range 400–700 °C. In addition, Elemental analysis of walnut and almond shells has shown high carbon content and low nitrogen and sulfur contents in the obtained biochar. Subsequently, the superior stability of as-prepared anode materials is evident by thermogravimetric analysis in pure N2 gas atmosphere. Conversely, the LSFT anode has shown the highest electronic conductivity of 7.53Scm−1 at 700 °C. The obtained power density for LSFTO3-δ composite anode mixed in sub-bituminous coal, walnut and almond shells biochar is of 68, 55, 48 mWcm−2 respectively. A significant improvement in performance of DCFC (78 mWcm−2) was achieved.<br

Junction and energy band on novel semiconductor-based fuel cells

Fuel cells are highly efficient and green power sources. The typical membrane electrode assembly is necessary for common electrochemical devices. Recent research and development in solid oxide fuel cells have opened up many new opportunities based on the semiconductor or its heterostructure materials. Semiconductor-based fuel cells (SBFCs) realize the fuel cell functionality in a much more straightforward way. This work aims to discuss new strategies and scientific principles of SBFCs by reviewing various novel junction-types/interfaces, i.e., bulk and planar p-n junction, Schottky junction and n-i type interface contact. New designing methodologies of SBFCs from energy band/alignment and built-in electric field (BIEF) which block the internal electronic transport while assisting interfacial superionic transport, and subsequently enhance device performance, are comprehensively reviewed. This work highlights the recent advances of SBFCs and provides new methodology and understanding with significant importance for both fundamental and applied R&D on new-generation fuel cell materials and technologies

Semiconductor electrochemistry for clean energy conversion and storage

Semiconductors and the associated methodologies applied to electrochemistry have recently grown as an emerging field in energy materials and technologies. For example, semiconductor membranes and heterostructure fuel cells are new technological trend, which differ from the traditional fuel cell electrochemistry principle employing three basic functional components: anode, electrolyte, and cathode. The electrolyte is key to the device performance by providing an ionic charge flow pathway between the anode and cathode while preventing electron passage. In contrast, semiconductors and derived heterostructures with electron (hole) conducting materials have demonstrated to be much better ionic conductors than the conventional ionic electrolytes. The energy band structure and alignment, band bending and built-in electric field are all important elements in this context to realize the necessary fuel cell functionalities. This review further extends to semiconductor- based electrochemical energy conversion and storage, describing their fundamentals and working principles, with the intention of advancing the understanding of the roles of semiconductors and energy bands in electrochemical devices for energy conversion and storage, as well as applications to meet emerging demands widely involved in energy applications, such as photocatalysis/water splitting devices, batteries and solar cells. This review provides new ideas and new solutions to problems beyond the conventional electrochemistry and presents new interdisciplinary approaches to develop clean energy conversion and storage technologies

Semiconductor-ionic membrane of LaSrCoFe-oxide-doped ceria solid oxide fuel cells

A novel semiconductor-ionic La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF)-Sm/Ca co-doped CeO 2 (SCDC) nanocomposite has been developed as a membrane, which is sandwiched between two layers of Ni 0.8 Co 0.15 Al 0.05 Li-oxide (NCAL) to construct semiconductor-ion membrane fuel cell (SIMFC). Such a device presented an open circuit voltage (OCV) above 1.0 V and maximum power density of 814 mW cm −2 at 550 °C, which is much higher than 0.84 V and 300 mW cm −2 for the fuel cell using the SCDC membrane. Moreover, the SIMFC has a relatively promising long-term stability, the voltage can maintain at 0.966 V for 60 hours without degradation during the fuel cells operation and the open-circuit voltage (OCV) can return to 1.06 V after long-term fuel cell operation. The introduction of LSCF electronic conductor into the membrane did not cause any short circuit but brought significant enhancement of fuel cell performances. The Schottky junction is proposed to prevent the internal electrons passing thus avoiding the device short circuiting problem

Design principle and assessing the correlations in Sb-doped Ba_0.5Sr_0.5FeO_3–δ perovskite oxide for enhanced oxygen reduction catalytic performance

Lack of fundamental understanding of the oxygen reduction reaction (ORR) hampers the development of effective metal oxide catalysts and advance low-temperature solid oxide fuel cells (LT-SOFCs). In this study, we report Ba0.5Sr0.5Fe1–xSbxO3–δ (BSFSb, x = 0, 0.05, and 0.1) cathodes designed from both theoretical and experimental aspects to study a good relationship between a material property and enhanced ORR activity. The BSFSb cathode exhibits a very low area-specific resistance (ASR) of 0.20 Ω cm2 and excellent power output of 738 mW cm−2 using the Sm0.2Ce0.8O2 (SDC) electrolyte at 550 °C. The Sb ions doping significantly enhances electrical conductivity and reduces its ORR activation energy. First-principles calculations screen the potential of designed perovskite by showing very low vacancy formation energy and shift in O-p and Fe3-d band centers near to fermi level by replacing Fe with Sb ions. Correspondingly, wide range coverage of distributed orbitals at the fermi level in BSFSb cathode promotes charge transfer with lower energy barrier. These results demonstrate that this design can impact the development of highly functional ORR electrocatalysts for LT-SOFCs and other electrocatalyst applications