Baoyuan Wang

Composition dependence of band alignment and dielectric constant for Hf1−xTixO2 thin films on Si (100)

Composition-dependent band alignment and dielectric constant for Hf1−xTixO2 thin films on Si (100) have been investigated. It was found with increasing Ti content, the band gap and band offsets (ΔEv and ΔEc) of Hf1−xTixO2 films against Si all decrease and the optimal Ti content in the films should be no higher than 21%, at which ΔEc is 1.06 eV. The dielectric constant of the films not only can increase up to 31.3, but show a linear increase with increasing TiO2 content. Compared with HfO2 thin film with similar equivalent oxide thickness, low leakage currents were obtained.

Preparation and characterization of Sm and Ca co-doped ceria–La0.6Sr0.4Co0.2Fe0.8O3−δ semiconductor–ionic composites for electrolyte-layer-free fuel cells

A series of Sm and Ca co-doped ceria, i.e. Ca0.04Ce0.96-xSmxO2-delta (x = 0, 0.09, 0.16, and 0.24) (SCDC), were synthesized by a co-precipitation method. Detailed morphology, composition, crystal s ...

Study on Zinc Oxide-Based Electrolytes in Low-Temperature Solid Oxide Fuel Cells

Semiconducting-ionic conductors have been recently described as excellent electrolyte membranes for low-temperature operation solid oxide fuel cells (LT-SOFCs). In the present work, two new functional materials based on zinc oxide (ZnO)—a legacy material in semiconductors but exceptionally novel to solid state ionics—are developed as membranes in SOFCs for the first time. The proposed ZnO and ZnO-LCP (La/Pr doped CeO2) electrolytes are respectively sandwiched between two Ni0.8Co0.15Al0.05Li-oxide (NCAL) electrodes to construct fuel cell devices. The assembled ZnO fuel cell demonstrates encouraging power outputs of 158–482 mW cm−2 and high open circuit voltages (OCVs) of 1–1.06 V at 450–550 °C, while the ZnO-LCP cell delivers significantly enhanced performance with maximum power density of 864 mW cm−2 and OCV of 1.07 V at 550 °C. The conductive properties of the materials are investigated. As a consequence, the ZnO electrolyte and ZnO-LCP composite exhibit extraordinary ionic conductivities of 0.09 and 0.156 S cm−1 at 550 °C, respectively, and the proton conductive behavior of ZnO is verified. Furthermore, performance enhancement of the ZnO-LCP cell is studied by electrochemical impedance spectroscopy (EIS), which is found to be as a result of the significantly reduced grain boundary and electrode polarization resistances. These findings indicate that ZnO is a highly promising alternative semiconducting-ionic membrane to replace the electrolyte materials for advanced LT-SOFCs, which in turn provides a new strategic pathway for the future development of electrolytes.

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 ...

Progress in Electrolyte-Free Fuel Cells

Solid Oxide Fuel Cell (SOFC) represents a clean electrochemical energy conversion technology with characteristics of high conversion efficiency and low emissions. It is one of the most important new energy technologies in the future. However, the manufacture of SOFCs based on the structure of anode/electrolyte/cathode is complicated and time-consuming. Thus, the cost for the entire fabrication and technology is too high to be affordable and challenges still hinder commercialization. Recently, a novel type of Electrolyte -free fuel cell (EFFC) with single component was invented which could be the potential candidate for the next generation of advanced fuel cells. This paper briefly introduces the EFFC, working principle, performance and advantages with updated research progress. A number of key R&D issues about EFFCs have been addressed and future opportunities and challenges are discussed.

Semiconductor-Ionic Nanocomposite La0.1Sr0.9MnO3−δ-Ce0.8Sm0.2O2−δ Functional Layer for High Performance Low Temperature SOFC

A novel composite was synthesized by mixing La0.1Sr0.9MnO3−δ (LSM) with Ce0.8Sm0.2O2−δ (SDC) for the functional layer of low temperature solid oxide fuel cell (LT-SOFC). Though LSM, a highly electronic conducting semiconductor, was used in the functional layer, the fuel cell device could reach OCVs higher than 1.0 V without short-circuit problem. A typical diode or rectification effect was observed when an external electric force was supplied on the device under fuel cell atmosphere, which indicated the existence of a junction that prevented the device from short-circuit problem. The optimum ratio of LSM:SDC = 1:2 was found for the LT-SOFC to reach the highest power density of 742 mW·cm−2 under 550 °C The electrochemical impedance spectroscopy data highlighted that introducing LSM into SDC electrolyte layer not only decreased charge-transfer resistances from 0.66 Ω·cm2 for SDC to 0.47–0.49 Ω·cm2 for LSM-SDC composite, but also decreased the activation energy of ionic conduction from 0.55 to 0.20 eV.