Y and Ni Co-doped BaZrO3 as a proton-conducting solid oxide fuel cell electrolyte exhibiting superior power performance

The fabrication of anode supported single cells based on BaZr0.8Y0.2O3-δ (BZY20) electrolyte is challenging due to its poor sinteractive nature. The acceleration of shrinkage behavior, improved sinterability and larger grain size were achieved by the partial substitution of Zr with Ni in the BZY perovskite. Phase pure Ni-doped BZY powders of nominal compositions BaZr0.8-xY0.2NixO3-δ were synthesized up to x = 0.04 using a wet chemical combustion synthesis route. BaZr0.76Y0.2Ni0.04O3-δ (BZYNi04) exhibited adequate total conductivity and the open circuit voltage (OCV) values measured on the BZYNi04 pellet suggested lack of significant electronic contribution. The improved sinterability of BZYNi04 assisted the ease in film fabrication and this coupled with the application of an anode functional layer and a suitable cathode, PrBaCo2O5+δ (PBCO), resulted in a superior fuel cell power performance. With humidified hydrogen and static air as the fuel and oxidant, respectively, a peak power density value of 428 and 240 mW cm-2 was obtained at 700 and 600°C, respectively

Preventing light-induced degradation in multicrystalline silicon

Multicrystalline silicon (mc-Si) is currently dominating the silicon solar cell market due to low ingot costs, but its efficiency is limited by transition metals, extended defects, and light-induced degradation (LID). LID is traditionally associated with a boron-oxygen complex, but the origin of the degradation in the top of the commercial mc-Si brick is revealed to be interstitial copper. We demonstrate that both a large negative corona charge and an aluminum oxide thin film with a built-in negative charge decrease the interstitial copper concentration in the bulk, preventing LID in mc-Si.Peer reviewe

Reversible solid oxide fuel cells (R-SOFCs) with chemically stable proton-conducting oxides

Proton-conducting oxides offer a promising way of lowering the working temperature of solid oxide cells to the intermediate temperate range (500 to 700°C) due to their better ionic conductivity. In addition, the application of proton-conducting oxides in both solid oxide fuel cells (SOFCs) and sold oxide electrolysis cells (SOECs) provides unique advantages compared with the use of conventional oxygen-ion conducting conductors, including the formation of water at the air electrode site. Since the discovery of proton conduction in some oxides about 30 years ago, the development of proton-conducting oxides in SOFCs and SOECs (the reverse mode of SOFCs) has gained increased attention. This paper briefly summarizes the development in the recent years of R-SOFCs with proton-conducting electrolytes, focusing on discussing the importance of adopting chemically stable materials in both fuel cell and electrolysis modes. The development of electrode materials for proton-conducting R-SOFCs is also discussed. © 2015 Elsevier B.V. All rights reserved

Steam electrolysis by solid oxide electrolysis cells (SOECs) with proton-conducting oxides

Energy crisis and environmental problems caused by the conventional combustion of fossil fuels boost the development of renewable and sustainable energies. H2 is regarded as a clean fuel for many applications and it also serves as an energy carrier for many renewable energy sources, such as solar and wind power. Among all the technologies for H2 production, steam electrolysis by solid oxide electrolysis cells (SOECs) has attracted much attention due to its high efficiency and low environmental impact, provided that the needed electrical power is generated from renewable sources. However, the deployment of SOECs based on conventional oxygen-ion conductors is limited by several issues, such as high operating temperature, hydrogen purification from water, and electrode stability. To avoid these problems, proton-conducting oxides are proposed as electrolyte materials for SOECs. This review paper provides a broad overview of the research progresses made for proton-conducting SOECs, summarizing the past work and finding the problems for the development of proton-conducting SOECs, as well as pointing out potential development directions. © The Royal Society of Chemistry 2014

Nanostructuring the electronic conducting La0.8Sr0.2MnO3−δ cathode for high-performance in proton-conducting solid oxide fuel cells below 600°C

Proton-conducting oxides offer a promising electrolyte solution for intermediate temperature solid oxide fuel cells (SOFCs) due to their high conductivity and low activation energy. However, the lower operation temperature leads to a reduced cathode activity and thus a poorer fuel cell performance. La0.8Sr0.2MnO3−δ (LSM) is the classical cathode material for high-temperature SOFCs, which lack features as a proper SOFC cathode material at intermediate temperatures. Despite this, we here successfully couple nanostructured LSM cathode with proton-conducting electrolytes to operate below 600°C with desirable SOFC performance. Inkjet printing allows depositing nanostructured particles of LSM on Y-doped BaZrO3 (BZY) backbones as cathodes for proton-conducting SOFCs, which provides one of the highest power output for the BZY-based fuel cells below 600°C. This somehow changes the common knowledge that LSM can be applied as a SOFC cathode materials only at high temperatures (above 700°C)

Yttrium and nickel co-doped BaZrO3 as a proton-conducting electrolyte for intermediate temperature solid oxide fuel cells

High temperature proton conducting oxides, due to their lower activation energy for proton conduction, can achieve high conductivity at relatively low temperatures (500-700°C). Though BaZr0.8Y0.2O3-δ (BZY) perovskite exhibits good chemical stability and high bulk conductivity, high grain boundary resistance decreases its total conductivity. This work focuses on substitution of Zr4+ with Ni2+ in the perovskite B-site in a targeted fashion in order to promote the sinterability of BZY. Powder X-ray diffraction analysis showed the formation of single phases for Ba0.8-xY0.2NixO3-δ compositions up to x = 0.04. Scanning electron microscopy (SEM) image analysis demonstrated that densification is promoted by increasing the Ni-content, reaching a fully dense microstructure for Ba0.76Y0.2Ni0.04O3-δ (BZYNi04). An anode supported single cell based on BZYNi04 electrolyte showed superior power performance, achieving 240 and 428 mW cm-2 at 600 and 700°C, respectively

Adhesion and Percolation Parameters in Two Dimensional Pd-LSCM Composites for SOFC Anode Current Collection

This paper is concerned with palladium-(La0.75Sr0.25)(0.97)Cr0.5Mn0.5O3 (LSCM) composite current collectors for solid oxide fuel cells (SOFCs); the composites, which are in a 2D configuration (thickness of about 8-10 mu m) are deposited upon an LSCM electrode layer on top of an yttria zirconia electrolyte substrate. The influence of the LSCM particle size on the adhesion between palladium and LSCM are reported and discussed. Compositions using four different LSCM particle sizes (0.21, 0.49, 0.64, and 0.81 mu m) with sintered Pd particle sizes approaching 10 mu m are investigated. The best bonding is obtained when smaller particles are used. The electrical dc conductivity of the composite is reported as a function of the palladium volume fraction for all used LSCM particle sizes. The measured experimental values present typical insulating-conductive percolation. However, the transition occurs at similar to 33% of the conductive phase, that is, a lower percentage than for 2D ideal systems and a higher percentage than for 3D ideal systems. This is consistent with lower-dimension percolation for a system of large-grained conductors and small-grained insulators. The general effective media (GEM) equation is used to fit the experimental data, and the two main parameters (the threshold point phi(c) and the exponent t) are defined.</p

Adhesion and Percolation Parameters in Two Dimensional Pd-LSCM Composites for SOFC Anode Current Collection

This paper is concerned with palladium-(La0.75Sr0.25)(0.97)Cr0.5Mn0.5O3 (LSCM) composite current collectors for solid oxide fuel cells (SOFCs); the composites, which are in a 2D configuration (thickness of about 8-10 mu m) are deposited upon an LSCM electrode layer on top of an yttria zirconia electrolyte substrate. The influence of the LSCM particle size on the adhesion between palladium and LSCM are reported and discussed. Compositions using four different LSCM particle sizes (0.21, 0.49, 0.64, and 0.81 mu m) with sintered Pd particle sizes approaching 10 mu m are investigated. The best bonding is obtained when smaller particles are used. The electrical dc conductivity of the composite is reported as a function of the palladium volume fraction for all used LSCM particle sizes. The measured experimental values present typical insulating-conductive percolation. However, the transition occurs at similar to 33% of the conductive phase, that is, a lower percentage than for 2D ideal systems and a higher percentage than for 3D ideal systems. This is consistent with lower-dimension percolation for a system of large-grained conductors and small-grained insulators. The general effective media (GEM) equation is used to fit the experimental data, and the two main parameters (the threshold point phi(c) and the exponent t) are defined.</p

Parametric study of self-forming ZnO nanowall network with honeycomb structure by pulsed laser deposition

The successful synthesis of catalyst free zinc oxide (ZnO) Nanowall networks with honeycomb like struc-ture by Pulsed Laser Deposition (PLD) is demonstrated in this paper. The synthesis was conducted directlyon Silicon (Si) (1 0 0) and Glass-ITO substrates without the intermediate of metal catalyst, template orchemical etching. Kinetic of growth and effects of gas pressure and substrate temperature were studiedby depositing ZnO films on P type Si (1 0 0) substrates with different deposition parameters. The opti-mized growth parameters were found as: 10 mTorr oxygen pressure, 600◦C substrate temperature, anddeposition duration equal or higher than 10 min. X-Ray Diffraction (XRD), Scanning Electron Microscopy(SEM) and Photoluminescence (PL) measurements were used to investigate structural, microstructuraland optical properties of ZnO Nanowall networks produced. They exhibit a non-uniform size high qualityhoneycomb structure with low deep level defects