The generalization of the Local Density Approximation (LDA) method for the systems with strong Coulomb correlations is presented which gives a correct description of the Mott insulators. The LDA+U method is based on the model hamiltonian approach and allows to take into account the non-sphericity of the Coulomb and exchange interactions. parameters. Orbital-dependent LDA+U potential gives correct orbital polarization and corresponding Jahn-Teller distortion. To calculate the spectra of the strongly correlated systems the impurity Anderson model should be solved with a many-electron trial wave function. All parameters of the many-electron hamiltonian are taken from LDA+U calculations. The method was applied to NiO and has shown good agreement with experimental photoemission spectra and with the oxygen Kα X-ray emission spectrum.

http://absimage.aps.org/image/MAR06/MWS_MAR06-2005-007233.pdf

First-principles calculations of electronic structure and spectra of strongly correlated systems: the LDA+U method

Bi and Sn co-doped perovskite BaFe0.8−XSn0.2BiXO3−δ materials have been designed and characterized as a series of new cathodes for proton-conducting solid oxide fuel cells (SOFCs), providing a new life for the traditional BaFeO3-based cathodes. Proton uptake of the cathode increases significantly with bismuth-doping, favoring the application of Bi and Sn co-doped perovskite BaFe0.8−XSn0.2BiXO3−δ materials in proton-conducting SOFCs. The density functional theory (DFT) calculation also suggests that the bismuth-doping leads to a dramatic increase of hydration energy and acceleration of proton migration for the BFS material. The XPS results show that the oxygen reduction reaction (ORR) activity of the cathode is enhanced after bismuth is added, which is consistent with the experimental results of the power density of the single cell. The maximum power density of the single cells with the structure of NiO-BaZr0.1Ce0.7Y0.2O3−δ|BaZr0.1Ce0.7Y0.2O3−δ| BaFe0.5Sn0.2Bi0.3O3−δ (BFSBi0.3) reached 1277 mW cm−2 at 700 °C, which is a record-high performance for proton-conducting SOFCs using cobalt-free cathodes, compared with previous reports. The outstanding fuel cell performance and good long term stability indicate that bismuth-doping is an effective way of promoting proton-conduction in traditional cathodes. This study opens a new door to the design of high performance cathodes for proton-conducting SOFCs.

A novel cobalt-free cathode with triple-conduction for proton-conducting solid oxide fuel cells with unprecedented performance

Sintering aids for proton-conducting oxides – A double-edged sword? A mini review

There is a growing interest in solid oxide fuel cells (SOFCs) technology among the researchers a promising power generation with high energy efficiency, inflated fuel flexibility, and low environmental impact compared to conventional power generation systems. SOFCs are devices in which the chemical energy is directly converted into electrical energy with negligible emission. SOFCs have low pollution characteristics, high efficiency (~ 60%), and possess expanded fuel selection with little environmental effects. A single cell component of SOFCs is consisting an anode, cathode and an electrolyte which are stacked layer by layer to produce higher amount of power. The dense ceramic electrolyte transporting O2− ions and fills the space between the electrodes material. Redox reaction occurred at the electrodes side in the presence of fuels. The operating temperatures of SOFCs of 600–1200 °C which produced heat as a byproduct and fast electro-catalytic activity while using nonprecious metals. Many ceramic materials have been investigated for SOFCs electrolyte. Yttria-stabilized zirconia (YSZ) material was extensively used as dense electrolyte in SOFCs technology. In this review, the article presents; overview of the SOFCs devices and their related materials and mostly reviewed newly available reported.

/pdf/review-of-solid-oxide-fuel-cell-materials-cathode-anode-and-54cyyyvuay.pdf

Hongning Kou

Papers

Electrochemical performance of protonic ceramic fuel cells with stable BaZrO3-based electrolyte: A mini-review

Evaluating the effect of Pr-doping on the performance of strontium-doped lanthanum ferrite cathodes for protonic SOFCs

Optimization of sintering temperature for SOFCs by a co-firing method