Inkjet Printing Functionalization of SOFC LSCF Cathodes.

An important segment of the future renewable energy economy is the implementation of novel energy generation systems. Such electrochemical systems are solid oxide fuel cells, which have the advantage of direct conversion of the chemical energy stored in the fuel to electrical energy with high efficiency. Improving the performance and lowering the cost of solid oxide fuel cells (SOFCs) are strongly dependent on finding commercially viable methods for nano-functionalization of their electrodes via infiltration. Inkjet printing technology was proven to be a feasible method providing scalability and high-resolution ink delivery. LaxSr1-xCoyFe1-yO3-δ cathodes were modified using inkjet printing for infiltration with two different materials: Gd-doped ceria (CGO) commonly used as ion-conductor and La0.6Sr0.4CoO3-δ (LCO) commonly used as a mixed ionic electronic conductor. As-modified surface structures promoted the extension of the three-phase boundary (TPB) and enhanced the mechanisms of the oxygen reduction reaction. Electrochemical impedance measurements revealed significantly lowered polarization resistances (between 2.7 and 3.7 times) and maximum power output enhancement of 24% for CGO infiltrated electrodes and 40% for LCO infiltrated electrodes

Inkjet Printing Infiltration of the Doped Ceria Interlayer in Commercial Anode-Supported SOFCs.

Single-step inkjet printing infiltration with doped ceria Ce0.9Ye0.1O1.95 (YDC) and cobalt oxide (CoxOy) precursor inks was performed in order to modify the properties of the doped ceria interlayer in commercial (50 × 50 × 0.5 mm3 size) anode-supported SOFCs. The penetration of the inks throughout the La0.8Sr0.2Co0.5Fe0.5O3-δ porous cathode to the Gd0.1Ce0.9O2 (GDC) interlayer was achieved by optimisation of the inks' rheology jetting parameters. The low-temperature calcination (750 °C) resulted in densification of the Gd-doped ceria porous interlayer as well as decoration of the cathode scaffold with nanoparticles (~20-50 nm in size). The I-V testing in pure hydrogen showed a maximum power density gain of ~20% at 700 °C and ~97% at 800 °C for the infiltrated cells. The latter effect was largely assigned to the improvement in the interfacial Ohmic resistance due to the densification of the interlayer. The EIS study of the polarisation losses of the reference and infiltrated cells revealed a reduction in the activation polarisations losses at 700 °C due to the nano-decoration of the La0.8Sr0.2Co0.5Fe0.5O3-δ scaffold surface. Such was not the case at 800 °C, where the drop in Ohmic losses was dominant. This work demonstrated that single-step inkjet printing infiltration, a non-disruptive, low-cost technique, can produce significant and scalable performance enhancements in commercial anode-supported SOFCs

Experimental characterization and elementary reaction modeling of solid oxide electrolyte direct carbon fuel cell

A detailed mechanistic model for solid oxide electrolyte direct carbon fuel cell (SO-DCFC) is developed while considering the thermo-chemical and electrochemical elementary reactions in both the carbon bed and the SOFC, as well as the meso-scale transport processes within the carbon bed and the SOFC electrode porous structures. The model is validated using data from a fixed bed carbon gasification experiment and the SO-DCFC performance testing experiments carried out using different carrier gases and at various temperatures. The analyzes of the experimental and modeling results indicate the strong influence of the carrier gas on the cell performance. The coupling between carbon gasification and electrochemical oxidation on the SO-DCFC performance that results in an unusual transition zone in the cell polarization curve was predicted by the model, and analyzed in detail at the elementary reaction level. We conclude that the carbon bed physical properties such as the bed height, char conversion ratio and fuel utilization, as well as the temperature significantly limit the performance of the SO-DCFC.National Natural Science Foundation (China) (20776078)National Natural Science Foundation (China) (51106085)Low Carbon Energy University Alliance (LCEUA) (Seed Funding

Inkjet printing and inkjet infiltration of functional coatings for SOFCs fabrication

Inkjet printing fabrication and modification of electrodes and electrolytes of SOFCs were studied. Electromagnetic print-heads were utilized to reproducibly dispense droplets of inks at rates of several kHz on demand. Printing parameters including pressure, nozzle opening time and drop spreading were studied in order to optimize the inks jetting and delivery. Scanning electron microscopy revealed highly conformal ~ 6-10 μm thick dense electrolyte layers routinely produced on cermet and metal porous supports. Open circuit voltages ranging from 0.95 to 1.01 V, and a maximum power density of ~180 mW.cm−2 were measured at 750 °C on Ni-8YSZ/YSZ/LSM single cell 50×50 mm in size. The effect of anode and cathode microstructures on the electrochemical performance was investigated. Two - step fabrication of the electrodes using inkjet printing infiltration was implemented. In the first step the porous electrode scaffold was created printing suspension composite inks. During the second step inkjet printing infiltration was utilized for controllable loading of active elements and a formation of nano-grid decorations on the scaffolds radically reducing the activation polarization losses of both electrodes. Symmetrical cells of both types were characterized by impedance spectroscopy in order to reveal the relation between the microstructure and the electrochemical performance

Evaluation of inkjet-printed spinel coatings on standard and surface nitrided ferritic stainless steels for interconnect application in solid oxide fuel cell devices

Inkjet printing technology was employed for the application of protective layer coatings in SOFC metallic interconnects. Aqueous-based spinel coatings were inkjet-printed on standard and surface nitrided K41 ferritic stainless-steel substrates. Inkjet-printed substrates were exposed to high-temperature oxidation and Area Specific Resistance (ASR) tests for 1000 h at 700 degrees C in air with 3% volume humidity, simulating SOFC cathode environment. Performance of inkjet printed coatings and effect of nitriding stainless-steel substrates were evaluated based on chromium migration/retention and Area Specific Resistance. Sol-gel infiltration was introduced to develop a scaffold layer over the porous microstructure. With the ASR reduced to a level ~60 m omega cm2 and chromium concentration in the getter (cathode) material below 1 atomic%, close to the detection threshold, the protective layers produced via inkjet printing present a promising solution for SOFC interconnector applications

Inkjet printing and inkjet infiltration of functional coatings for SOFCs fabrication

Inkjet printing fabrication and modification of electrodes and electrolytes of SOFCs were studied. Electromagnetic print-heads were utilized to reproducibly dispense droplets of inks at rates of several kHz on demand. Printing parameters including pressure, nozzle opening time and drop spreading were studied in order to optimize the inks jetting and delivery. Scanning electron microscopy revealed highly conformal similar to 6-10 mu m thick dense electrolyte layers routinely produced on cermet and metal porous supports. Open circuit voltages ranging from 0.95 to 1.01 V, and a maximum power density of similar to 180 mW.cm(-2) were measured at 750 degrees C on Ni-8YSZ/YSZ/LSM single cell 50x50 mm in size. The effect of anode and cathode microstructures on the electrochemical performance was investigated. Two - step fabrication of the electrodes using inkjet printing infiltration was implemented. In the first step the porous electrode scaffold was created printing suspension composite inks. During the second step inkjet printing infiltration was utilized for controllable loading of active elements and a formation of nano-grid decorations on the scaffolds radically reducing the activation polarization losses of both electrodes. Symmetrical cells of both types were characterized by impedance spectroscopy in order to reveal the relation between the microstructure and the electrochemical performance

A comparative study on the conductive properties of coated and printed silver layers on a paper substrate

The industrial sector of flexible printed electronics has shown a dynamic growth in the last decades. Therefore, demand for new inks, coatings and printing methods leading to improved performances of the electronic components at room temperature is also increasing. Here, we present a study on the conductive properties of silver layers obtained by different coating and printing methods. The results obtained proved that drop-on-demand inkjet printing of water-based inks containing micron-sized silver flakes with narrow-size distribution is a feasible method for in situ fabrication of conductive silver coatings that does not require additional heat treatment. A rigorous optimization Taguchi experiment was carried out considering the major process parameters. This experiment showed that the printing pressure was the dominant factor defining the quality of the printed coatings and tracks

Infiltration of commercially available, anode supported SOFC’s via inkjet printing

Commercially available anode supported solid oxide fuel cells (NiO-8YSZ/8YSZ/LSCF- 20 mm in diameter) were anode infiltrated with gadolinium doped ceria (CGO) using a scalable drop-on-demand inkjet printing process. Cells were infiltrated with two different precursor solutions—water based or propionic acid based. The saturation limit of the 0.5 lm thick anode supports sintered at 1400 C was found to be approximately 1wt%. No significant enhancement in power output was recorded at practical voltage levels. Microstructural characterisation was carried out after electrochemical performance testing using high resolution scanning electron microscopy. This work demonstrates that despite the feasibility of achieving CGO nanoparticle infiltration into thick, commercial SOFC anodes with a simple, low-cost and industrially scalable procedure other loss mechanisms were dominant. Infiltration of model symmetric anode cells with the propionic acid based ink demonstrated that significant reductions in polarisation resistance were possible