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Solid oxide fuel cell (SOFC) technology has been proven to be a highly efficient electrochemical device that directly converts chemical energy into electrical energy with a potential to increase system efficiencies and to significantly reduce emissions in oil and gas operations. Enabling an effective integration and smarter utilization of SOFC systems at different scales and point-of-use can lead to an overall system efficiency improvement. In this research paper, two case studies, including the steam and power system in a gas plant, are considered for comparative analysis purposes. The first case study, base case, is a traditional steam and power system in a natural gas processing plant and the proposed case is the combined steam and power system with SOFC unit. Techno-economic and environmental analyses are performed for both cases. To carry out a comparative analysis, the power output of both cases is fixed at 20 MW. The results of this study show that a reduction of almost 35% in the emissions is possible and the cost of electricity becomes about 25% less for the proposed case.

New mixed ion-electron conductors are desired to lower the operating temperature of solid oxide fuel cells. The O Frenkel energy and migration of O ions in PrBa(Co/Fe)2O5.5 are studied for this purpose by density functional theory. The electronic structure and charge redistribution during defect formation are analyzed. We demonstrate that Co → Fe substitution strongly affects the formation of defects and consequently the O migration. The low O Frenkel energy points to a high concentration of O vacancies. The migration of the O ions shows a distinct anisotropy.

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.

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 the increasing 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.

Full ceramic anodes have been developed over the last decade as an alternative to the state-of-the-art Ni/YSZ cermet. The objective is to overcome the technical limitations of the cermet, especially in high fuel utilization operational mode, when hydrocarbon fuels are used, or in systems where rapid heat up is required. Numerous oxide compositions were proposed and investigated. (La,Sr)Cr0.5Mn0.5O3(LSCM) perovskite has been reported as a very promising anode material because of its high tolerance to carbon and sulfur, and its redox and thermal cycling stability. However, similarly to other oxide anode materials, its overall performance still needed further improvement to match that of Ni/YSZ. The relatively low performance of LSCM compared to Ni/YSZ, used to be attributed to its relatively low electronic conductivity. Recently, we have reported that the pre-coating LSCM with Ni nitrate results in a considerable decrease in the anodic polarization resistance and activation energy. Ni dissolves in the perovskite phase at high temperature under oxidizing atmosphere, and then exsolves in the form of nanoparticles under reducing atmospheres. This type of anode composition with split functionalities (ionic conduction, electronic conduction, and catalytic activity) gives a unique opportunity to investigate the specific influence of each of the above functions on the anodic mechanisms and performance. In this work, electrochemical impedance spectroscopy was used to characterize anode compositions containing LSCM and different levels (15, 40, and 60 wt%) of gadolinia doped ceria (CGO), with and without additional submicron Ni, as well as Ni nanoparticles exsoluted from pre-coated larger LSCM particles. Impedance measurements were performed in a three electrode – half cell configuration from 700 to 900°C under two flow rates of 3% wet H2(50 and 150 ml/min). At 900°C and under 150 mL/min of 3% wet H2, lower values of the polarization resistance (Rp) were measured for the samples containing CGO compared to pure LSCM ones. The Rp showed a slight decrease when the content of CGO was increased (15 to 40 and 60 wt%). This was characterized by a decrease of the high frequency part of the impedance diagrams, likely due to the higher ionic conductivity brought by the addition of CGO. The addition of 5 wt% of submicron Ni to LSCM-CGO led to a remarkable decrease in Rp. This effect was even more spectacular for the samples containing 5 wt% of exsoluted Ni nanoparticles, characterized by a decrease of the whole impedance diagram, and especially the high and the middle frequency parts, which suggests an enhancement of the electrochemical processes related to anode charge transfer. Further analysis of the impedance diagrams, measured for the above anodes at different temperatures and gas flow rates, is in progress in order to define the effect of different anode functionalities on the anodic processes involved, and thus its overall performance.

In this work (La0.75Sr0.25)0.97Cr0.5Mn0.5O3 (LSCM) perovskite powders were pre-coated with 5 wt% nickel and mixed with different amounts of CGO for testing as anode materials under 3% wet H2. By using scanning transmission electron microscopy (STEM) with X-ray energy dispersive spectroscopy (EDS), we demonstrated that Ni forms a solid solution in the perovkite phase under oxidizing atmosphere and exsolves in form of nanoparticles under reducing atmospheres. The presence of the catalyst nanoparticles led to a decrease in the anodic activation energy by half and thus the polarization resistance was dropped by 60% at 800¢ªC. The effect of CGO amount will be also discussed.

The impregnation method has been considered as one of the most successful techniques for the fabrication of highly efficient electrodes for solid oxide fuel and electrolysis cells (SOCs) at the lab scale. However, because the impregnation is usually performed manually, its irreproducibility remains a major problem that can be solved by using controllable techniques, such as inkjet printing. In this paper, lanthanum strontium manganite (LSM)/yttria stabilized zirconia (YSZ) air electrodes were prepared by infiltrating YSZ porous bodies with LSM precursor solution using inkjet printing, followed by annealing at 800°C for 2 hours. XRD analysis confirmed the formation of the LSM phase, which was in the form of nanoparticles with size in the 50-70 nm range on the YSZ walls, as revealed by FEG-SEM observations. The effect of printing parameters on the distribution of the impregnated phase was investigated and discussed.

In this work, a highly scalable technique is proposed as an alternative to the lab-scale impregnation method. LSCM–CGO powders were pre-coated with 5 wt% of Ni from nitrates. After appropriate mixing and adequate heat treatment, coated powders were then dispersed into organic based vehicles to form a screen-printable ink which was deposited and fired to form SOFC anode layers. Electrochemical tests show a considerable enhancement of the pre-coated anode performances under 50 ml/min wet H2 flow with polarization resistance decreased from about 0.60 Ω cm2 to 0.38 Ω cm2 at 900 °C and from 6.70 Ω cm2 to 1.37 Ω cm2 at 700 °C. This is most likely due to the pre-coating process resulting in nano-scaled Ni particles with two typical sizes; from 50 to 200 nm and from 10 to 40 nm. Converging indications suggest that the latter type of particle comes from solid state solution of Ni in LSCM phase under oxidizing conditions and exsolution as nanoparticles under reducing atmospheres.

This paper focuses on the electrochemical potentialities of the 2D misfit compound Ca3Co4O9−δ, so far mainly investigated for its thermoelectric properties. Its expansion coefficient (TEC = (9–10) × 10−6 °C−1) and its chemical stability are compatible with standard CGO IT-electrolyte and the first optimisation steps of the deposited cathode have been performed with the aim to minimise the ASR and increase the cell durability. Particular attention has been paid on the effect of thickness and microstructure for pure and composite cathodes. The electrode reaction was performed on symmetrical cells. The preliminary results presented here show that the composite (70 wt.% Ca3Co4O9−δ–30 wt.% CGO) gives the lowest ASR values compare to single-phased electrodes. Strikingly, the ASR values increase for thinner deposited layers. The effect of various current collectors (gold grid vs. platinum paste) has been also checked.

NbTi 0.5 Ni 0.5 O 4 (NTNO) has been prepared using solid state synthesis and investigated as a potential anode material. The oxide form of NTNO has single phase rutile-type structure with tetragonal (P42/mnm) space group. The reduced form is a composite of nano-scaled particles of metallic Ni and Nb 1.33 Ti 0.67 O 4 phase. Reduced NTNO showed high electronic conductivity up to 280 S.cm − 1 at 900 °C in reducing atmosphere, but suffers from low CTE equal to 3.78 10 − 6 K − 1 . Studies of NTNO as anode material were carried out in a three electrode – electrochemical half cell configuration under pure humidified H 2 at 900 °C using a 2 mm thick zirconia electrolyte and without any additional current collector material. The results show a reasonable series resistance (R s ) equal to 2.7 Ωcm 2 (about 50% higher than for metallic gold layers) indicating a good current collection performance for a 10 μm layer of material. The polarization resistance (R p ) was equal to 33 Ωcm 2 and is attributed to a poor density of three phase boundaries (TPB) and shortage of oxide ion conduction in the anode layer. The results show the potential of NTNO as an anode material, especially after optimization of the microstructure towards the increase of TPB length.

This paper is concerned with Palladium-(La0.75Sr 0.25S)0.97Cr0.5Mn0.5O3 (LSCM) composite current collectors for solid oxide fuel cells (SOFCs); the composites, which are in a 2D configuration (thickness of about 8-10 μm), 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 μm) with sintered Pd particle sizes approaching 10 μm 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 ∼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 (CEM) equation is used to fit the experimental data, and the two main parameters (the threshold point φc and the exponent t) are defined. © 2010 WILEY-VCH Verlag GmbH &. Co. KGaA.

The limitations of the current state of the art Ni-YSZ cermet anodes with respect to Redox stability, coking and sulphur tolerance are well acknowledged. A material which mitigates all or even some of these issues would be of great importence for the continued development of robust SOFC systems. One such promising material system is based around the perovskite (La,Sr)Cr0.5Mn0.5O3 (LSCM). In this paper, some aspects of the work, carried out to integrate LSCM anodes into the IP-SOFC, are described. The intricacies of the introduction of a new material into an existing stack design concept are considered and how this impacts the performance and requirements of adjacent materials. In the case of the LSCM integration, at least as much work has gone into the development of these layers as into the anode itself. In particular, the design of a current collector to optimise both the conductivity across the layers and the adhesion to the anode has proved to be a challenging task within the normal design constraints of the IP-SOFC. Initial perfomance of around 75 mW cm–2 in a stack repeat unit test is encouraging and initial analysis has suggested that further development of the current collecting microstructure will confer significant performance improvements.

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.

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.

Cu(In, Ga)Se 2 (CIGS) ink was formulated from CIGS powder, polyvinyl butyral PVB, terpineol and polyester/polyamine co-polymeric dispersant KD-1. Thin films with different thicknesses were deposited on PET substrate using screen-printing followed by heat treatment using a Nd:YAG laser. The structure and morphology of the heated thin films were studied. The characterization of the CIGS powder, ink, and film was done using TGA, SEM, FIB, EDS, and XRD. TGA analysis shows that the CIGS ink is drying at 200 °C, which is well below the decomposition temperature of the PET substrate. It was observed by SEM that 20 pulses of 532nm and 60 mJ/cm2 Nd:YAG laser annealing causes atomic diffusion on the near surface area. Furthermore, FIB cross section images were utilized to monitor the effect of laser annealing in the depth of the layer. Laser annealing effects were compared to as deposited layer using XRD in reference to CIGS powder. The measurement shows that crystallinity of deposited CIGS is retained while EDS quantification and atomic ratio result in gradual loss of selenium as laser energy increases. The laser parameters were tuned in an effort to utilize laser annealing of screen-printed CIGS layer as a layer annealing method for solar cell fabrication process.

Conventional solid oxide fuel cells (SOFCs) based on yttria-stabilized zirconia (YSZ) require high operating temperatures in the 800-1000 °C range. Such high operating temperatures hinder the commercialization of SOFCs due to degradation and high cost issues. On the other hand high temperature proton conductors (HTPCs), due to their lower activation energy for proton conduction, can achieve high conductivity at relatively lower temperatures compared to their oxygen ion conducting counterparts. BaZrO3 related HTPC electrolyte materials possess good chemical stability and high bulk conductivity. However, due to its high refractory nature, fabrication of fully dense electrolyte films is very challenging. The poor sinterability of BaZrO3based materials leads to a large number of resistive grain boundaries, thus lowering the total proton conductivity. Previous reports have shown that NiO can function as an effective additive for enhancing the densification of BaZrO3 based materials [1, 2]. These studies did not focus on controlling the stoichiometry so as to accommodate Ni at a specific site in the perovskite structure. Contrary to the previous NiO sintering aid studies, the present work focuses on substitution of Zr with Ni in the perovskite B-site in a targeted fashion. Y-doped BaZrO3 (BZY) is chemically stable at fuel cell operating conditions and shows the best protonic conductivity when Y-content is 20 mol% [3]. In this work, the sinterability of 20 mol% Y-doped BaZrO3 (BZY20) was significantly improved by partial substitution of Zr with Ni in the perovskite B-site. The effect of Ni-doping on the shrinkage behavior of BZY has been identified through dilatometric measurements. The SEM analysis showed a pore-free dense microstructure for 4 mol% Ni-doped BZY (BaZr0.76Y0.2Ni0.04O3-δ, BZYNi04) and therefore electrochemical characterization studies were carried out on this material. The total conductivity of BZYNi04 in wet air was observed to be 0.0037 Scm-1 at 600 °C. The open circuit voltage (OCV) values recorded for BZYNi04 pellet fuel cell were 0.96, 0.99, 1.01, 1.03 and 1.034 V at 700, 650, 600, 550 and 500 °C respectively indicating that there is not much electronic conductivity. Ni-doped BZY electrolyte films were fabricated on an optimized NiO-BZY anode using co-pressing and co-firing process. Subsequently, a full fuel cell was fabricated with PrBaCo2O5+δ (PBCO) and BZY composite cathode. The ease of film electrolyte fabrication of low thickness assisted by the good sinterability of BZYNi04 coupled with employing an anode functional layer aided in attaining a superior power density output. Peak power density values of 428 and 340 mWcm-2 were obtained at 700 and 650 °C respectively when humidified hydrogen (≈ 3% H2O) and static air were used as the fuel and oxidant respectively. To the best of our knowledge, the power performance obtained in this work is the best reported yet for BaZrO3based proton conducting SOFCs. References P. Babilo, S. M. Haile, J. Am. Ceram. Soc. 88 (2005) 2362. J. Tong, D. Clark, M. Hoban, R. O’Hayre, Solid State Ionics 181 (2010) 496. K. D. Kreuer, S. Adams, W. Munch, A. Fuchs, U. Klock, J. Maier, Solid State Ionics 145 (2001) 295.

Increasing the density of the triple phase boundary (TPB) sites has been the main focus of the microstructural optimization of the electrodes in solid oxide fuel and Electrolysis Cells (SOCs). TPB is the interface between the catalyst/electronic conductor, the ionic conductor, and the gas phase where the electrode reactions occur. Better electrode performance is achieved with increasing the TPB surface. Classically, electrodes are prepared by mixing powders of the solid phases and then depositing them to form porous films after appropriate heat treatments. Optimizing the composition and particle size distribution of starting powders, as well as the deposition and sintering processes have led to a substantial increase in the TPB density. However, this has reached an optimum maturity. In the recent years impregnation based processes were developed to achieve larger TPB and better performance. In this scenario, one solid phase, usually the electrolyte, is sintered to form a porous backbone structure to be impregnated with a liquid precursor of the second phase. After drying and heating, the second solid phase is usually formed as a very fine structure on the top of larger particles of the porous backbone. This ensures a significant increase in the TPB, and good percolation of both solid phases. Very interesting results have been reported with a large number of cathode and anode materials in SOCs. In this paper we will review the progress performed in our laboratories in impregnation based SOCs electrodes, including methods, materials, and results. In addition, the optimization of inkjet printing impregnation process will be presented and discussed in terms of controllability, reproducibility, and scalability.