Authors acknowledge financial support from U.S. Department of Energy (US DOE) under the federal grant DE-FE-0023385. Technical discussion with Drs. Rin Burke and Shailesh Vora (National Energy Technology Laboratory) is gratefully acknowledged. Drs. Amit Pandey (LG Fuel Cells, Canton OH), Jeff Stevenson and Matt Chou (Pacific Northwest National Laboratory, Richland WA) are acknowledged for their help with long term test validation of the performance of the getters. Authors acknowledge the University of Connecticut for providing laboratory support. Dr. Lichun Zhang and Ms. Chiying Liang is acknowledged for technical discussion and help with the experiments.

1. Synthesis of chromium getter
<ol>
	<li>Synthesize precursor powder using alkaline earth and transition metal oxide salts via conventional coprecipitation synthesis route as depicted in Figure 116.
	<ol>
		<li>Prepare a stock solution using 50.33 g of strontium nitrate Sr(NO3)2 and 43.97 g of nickel nitrate hexahydrate Ni(NO3)2.6H2O in order to prepare 2.4 M solutions in 100 mL of de-ionized water.&#160;</li>
		<li>Use 9 mL of 2.4 M Sr(NO3)2 and add with 7 mL of 2.4 M solution of Ni(NO3)2.6H2O, followed by stirring the mixed solution and heating up to 80 &#176;C.</li>
		<li>Add 30 mL of 5 M NH4OH to increase the pH to 8.5 for precipitation, then, dry the solution in a dry oven and ensure that all the water evaporates until a blue waxy compound is observed. Rinse&#160;the powder in DI water to ensure that residual ammonium nitrate is removed by filtration. Finally, dry the powder at 120 &#176;C for 2 h.&#160; 
		Note: This will produce&#160;precursor powder for strontium nickel oxide (SNO) getter.&#160;</li>
	</ol>
	</li>
	<li>Dissolve the powder in water to prepare a slurry.&#160;</li>
	<li>Immerse the cordierite substrate in the slurry for dip-coating, followed by drying in air at ~120 &#176;C for at least 2 h with a ramp rate of 5 &#176;C.</li>
	<li>Calcine the substrate in air at the temperature of 650 &#176;C for 12 h with a ramp rate of 5 &#176;C to produce SNO getter.&#160;</li>
</ol>
2. Screening of chromium getter using Cr transpiration test
<ol>
	<li>Set up experiment following the illustration of Figure 2a&#160;for the validation of Cr getters.
	<ol>
		<li>Place 2 gram of sintered chromium oxide pellet (1,200 &#176;C, 2 h) as a chromium source in a quartz tube.&#160; 
		Note: the quartz tube is specifically designed with a diffuser inside (shown in Figure 2) to prevent any back diffusion of chromium vapor during operation. The dimensions of the fabricated getter cartridge match the inside diameter of the quartz tube. Getter cartridge is placed between the chromium source and the outlet elbow (shown in Figure 2).&#160;</li>
		<li>Flow the compressed air at a flow rate of 300 sccm through a mass flow controller (MFC). Bubble the air at room temperature water to ensure that the humidity is 3% H2O. This humidified air passes through the chromia pellets, evaporate chromium vapor and flow through the getter.&#160; 
		Note: The chiller and condenser are placed at the outlet of the transpiration setup to enable condensation of chromium-containing vapor which deposits at the outlet elbow (at the low temperature zone).</li>
		<li>Place additional wash bottles before venting the gas at the outlet to ensure that the evaporated chromium is captured.&#160;</li>
		<li>Having completed the setup, purge the tube with air for at least 1 h to ensure that there is no leaks or contaminants.&#160;</li>
		<li>Start the furnace to heat up to the desired temperature (for example, 850 &#176;C in this case) and hold it there for 500 h.&#160;</li>
		<li>Monitor the color change of outlet elbow and record for any discoloration due to deposited chromium compounds.&#160;</li>
		<li>Lower the furnace temperature back to room temperature (RT) after the completion of the test. Turn off the air flow until the furnace temperature reaches RT.&#160;</li>
		<li>Remove the getter sample for post-test analyses and characterization.&#160;</li>
	</ol>
	</li>
	<li>Quantitative analysis of chromium species by inductively coupled plasma mass spectroscopy (ICP-MS)&#160; 
	Note: ICP-MS sample preparation of post Cr transpiration test17.
	<ol>
		<li>Wash the deposited chromium from glass elbow, condenser, wash bottles and quartz tubes using 20% nitric acid to extract the chromium after conducting transpiration test for 500 h.&#160;</li>
		<li>Extract the deposited chromium by dissolving it in 20% nitric acid (HNO3) for 12 h.&#160;</li>
		<li>Further remove any undissolved chromium species from the glass wall by dissolution in alkaline potassium permanganate solution upon heating at 80 &#176;C. 
		Note: Convert any partial unreacted Cr3+ species to Cr6+ species in this step.&#160;</li>
		<li>Analyze the DI water and nitric acid blank sample by ICP-MS.</li>
		<li>Divide each sample into three parts for ICP-MS analysis and report the average value.</li>
	</ol>
	</li>
</ol>
3. Electrochemical validation of chromium getter using SOFC cells with and without getter&#160;
<ol>
	<li>Cell fabrication and in-operando electrochemical testing of Cr getters18,19
	<ol>
		<li>Fabricate SOFCs by screen printing LSM paste on the surface of YSZ electrolyte (Figure 3a).&#160;</li>
		<li>Sinter the applied LSM ink at 1,200 &#176;C for 2 h, heated with a ramp rate of 3 &#176;C/min.&#160;</li>
		<li>Use Pt electrode as the anode. Attach a Pt on the YSZ disc (anode side) as a reference electrode, and attach Pt gauze and Pt wires to YSZ electrolyte disc using Pt ink and then cure the SOFC at 850 &#176;C for 2 h at a ramp rate of 3 &#176;C/min.&#160;</li>
		<li>Conduct three distinct experiments using three identical SOFCs (namely Cell a, b, and c) to validate the efficacy of getters and demonstrate chromium poisoning without a getter.&#160; 
		Note: make sure to use the identical test conditions to simulate nominal SOFC operating conditions of 850 &#176;C and maintain the anode air (dry) for all the tests at 150 sccm.&#160;</li>
		<li>Assembly the Cell-a in the tube reactor in the absence of chromium source using paste for sealing. Heat the furnace with a ramp rate of 5 &#176;C/min up to a designed temperature (for example: 850 &#176;C in this study). Then, flow the 3% H2O/air (for example 300-500 sccm) to the LSM cathode.</li>
		<li>Measure the electrochemical performance of the SOFC using a multi-channel potentiostat9.&#160;</li>
		<li>Record the cell current every minute with a bias of 0.5 V applied between the cathode and the reference electrode.&#160;</li>
		<li>Conduct electrochemical impedance spectroscopy (EIS) analyses between cathode and reference electrode using three electrode mode in the frequency range of 0.5 Hz to 200 KHz with 10 mV sinus amplitude at an interval of 1 h. After a 100-hour test, cool down the furnace to room temperature and take the Cell-a for characterization.</li>
		<li>Place 2 gram chromium oxide (Cr2O3) pellets (source of chromium vapor) in a porous container at the constant heating zone of the alumina tube. Assembly the Cell-b in the tube reactor using paste for sealing.&#160; Heat the furnace with a ramp rate of 5 &#176;C/min up to 850 &#176;C. Then, flow the humidified air (for example 300-500 sccm) through the chromia pellets and ensure a constant generation of the chromium vapor species9.&#160;</li>
		<li>Repeat Steps 3.1.6 &#8211; 3.1.8. After a 100-hour test, cool down the furnace to room temperature and take the Cell-b for characterization.</li>
		<li>Place 2 gram chromium oxide (Cr2O3) pellets (source of chromium vapor) in a porous container at the constant heating zone of the alumina tube. Place a chromium getter above the chromium source. Assembly the Cell-c on the top of the tube reactor using paste for sealing. Heat the furnace with a ramp rate of 5 &#176;C/min up to a designed temperature (for example: 850&#176;C in this study). Then, flow the 3% H2O/air (for example 300-500 sccm) to the LSM cathode.</li>
		<li>Repeat Steps 3.1.6 &#8211; 3.1.8. After a 100-hour test, cool down the furnace to room temperature and take the Cell-c for characterization.</li>
	</ol>
	</li>
	<li>Posttest getter morphological and chemical characterization 
	Note: Posttest characterization is conducted using scanning electron microscopy coupled with energy dispersive spectroscopy and scanning transmission electron microscopy (STEM) coupled with EDS analyses. Focused electron and ion-beam technologies (FIB) have utilized for the preparation of nanoscale samples.&#160;
	<ol>
		<li>Analyze the microstructures of the cell component by fracturing after the electrochemical test.&#160; Use SEM instrument for morphological analysis. Ensure that both the morphologies and chemical compositions of LSM cathode surface and LSM/YSZ interface are analyzed13,14
		<ol>
			<li>Prior to conducting SEM analysis, prepare samples by sputter coating of gold (Au) films to make sure the sample surface is conductive (avoiding of charge on the sample surface). The coating chamber was under a vacuum (&#60; 50 mm Torr). The applied current was at 40 mA and the coating time was 1 min.&#160;&#160;</li>
			<li>Conduct quantitative elemental distribution using energy dispersive X-ray spectroscopy (EDS) technique. The distance between the specimen and the lower pole piece in SEM system was set at 10 mm. A voltage of 20 KV was applied for the SEM and EDS analysis.&#160;</li>
		</ol>
		</li>
		<li>Conduct the chemical, structural and morphological analyses of the chromium getter using the SEM-EDS technique to obtain the chromium capture profile across the getter channels.&#160;
		<ol>
			<li>Prepare the posttest getter sample by dissecting the getter sample into half using a knife.&#160;</li>
			<li>Repeat Step 3.1.1.1 to coat conductive gold films on the getter surface.</li>
			<li>Repeat Step 3.2.1.2. Ensure that detailed EDS analyses were conducted from the inlet of the getter towards the outlet along the central channel as shown in Figure 2b. Use weight (wt.) % of total chromium measured against the channel length to plot the chromium profile.</li>
		</ol>
		</li>
		<li>Conduct in-depth chemical, structural and morphological analyses of the chromium getter using the FIB-STEM-EDS technique17,20.
		<ol>
			<li>Repeat Step 3.1.1.1 to coat conductive gold films on the getter surface.</li>
			<li>Load the sample in the FIB-STEM instrument, select the region of interest (ROI) for sample extraction, deposit four layers of Pt to mark and protect the sample (a typical area of 30 &#181;m length &#215; 15 &#181;m width).</li>
			<li>Mill the channels around the above ROI using the FIB beam until a &#8220;bridge-like&#8221; strip is left. Then, make wedges at both sides of the strip to make sure the depth is enough for your analysis (a typical depth is 10-20 &#181;m).</li>
			<li>Mount to the micromanipulator needle and cut the FIB sample by milling using an ion beam with 15 nA current. Then lift the FIB sample from the bulk getter sample to the FIB-STEM grid holder, which is perpendicular to the electron beam. After the specimen touch the grid at right position, Pt is deposited using an ion beam current of 0.5 nA to connect the specimen to the grid.&#160; &#160;&#160;</li>
			<li>Make the specimen thinner using a FIB current of about 20 pA at 2 kV to obtain a 50-60 nm sample thickness. Final clean-up of the specimen is also performed using argon-milling at an extra low current (0.5 pA at 1 kV).&#160;</li>
			<li>Conduct STEM-EDS mapping of the above getter specimen. The scanning transmission electron microscope was operated at 200 kV. A High Angle Annular Dark Field (HAADF) image of the selected area on the getter specimen was obtained and elemental maps of relevant elements (such as Cr and Sr) were taken.&#160;&#160;</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Singh, P., Minh, N. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solid+oxide+fuel+cells:+Technology+status.">Solid oxide fuel cells: Technology status.</a> International Journal of Applied Ceramic Technology. 1, 5-15 (2005).</li><li>Stambouli, A. B., Traversa, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solid+oxide+fuel+cells+(SOFCs):+a+review+of+an+environmentally+clean+and+efficient+source+of+energy.">Solid oxide fuel cells (SOFCs): a review of an environmentally clean and efficient source of energy.</a> Renewable &#38; Sustainable Energy Reviews. 6, 433-455 (2002).</li><li>Mahato, N., Banerjee, A., Gupta, A., Omar, S., Balani, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Progress+in+material+selection+for+solid+oxide+fuel+cell+technology:+A+review.">Progress in material selection for solid oxide fuel cell technology: A review.</a> Progress in Materials Science. 72, 141-337 (2015).</li><li>Brandon, N. P., Skinner, S., Steele, B. C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+materials+for+fuel+cells.">Recent advances in materials for fuel cells.</a> Annual Review of Materials Research. 33, 183-213 (2003).</li><li>Piccardo, P., Amendola, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SOFC+&#8217;+s+Interconnects+Materials+Development.">SOFC &#8217; s Interconnects Materials Development.</a> Aisofc. , 189-194 (2009).</li><li>Yang, Z., Xia, G. -. G., Maupin, G. D., Stevenson, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conductive+protection+layers+on+oxidation+resistant+alloys+for+SOFC+interconnect+applications.">Conductive protection layers on oxidation resistant alloys for SOFC interconnect applications.</a> Surface and Coatings Technology. 201, 4476-4483 (2006).</li><li>Aphale, A. N., Hu, B., Reisert, M., Pandey, A., Singh, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxidation+Behavior+and+Chromium+Evaporation+From+Fe+and+Ni+Base+Alloys+Under+SOFC+Systems+Operation+Conditions.">Oxidation Behavior and Chromium Evaporation From Fe and Ni Base Alloys Under SOFC Systems Operation Conditions.</a> JOM. , (2018).</li><li>Matsuzaki, Y., Yasuda, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemical+properties+of+a+SOFC+cathode+in+contact+with+a+chromium-containing+alloy+separator.">Electrochemical properties of a SOFC cathode in contact with a chromium-containing alloy separator.</a> Solid State Ionics. 132, 271-278 (2000).</li><li>Hu, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+and+thermodynamic+evaluation+of+La1&#8722;xSrx+MnO3&#177;&#948;+and+La1&#8722;xSrxCo1&#8722;yFeyO3&#8722;&#948;+cathodes+in+Cr-containing+humidified+air.">Experimental and thermodynamic evaluation of La1&#8722;xSrx MnO3&#177;&#948; and La1&#8722;xSrxCo1&#8722;yFeyO3&#8722;&#948; cathodes in Cr-containing humidified air.</a> International Journal of Hydrogen Energy . 42, 10208-10216 (2017).</li><li>Aphale, A. N., Liang, C., Hu, B., Singh, P., Brandon, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Solid Oxide Fuel Cells Lifetime and Reliability: Critical Challenges in Fuel Cells. , 102-114 (2017).</li><li>Chen, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+chromium+contaminant+tolerant+BaO+infiltrated+La+0.6+Sr+0.4Co+0.2+Fe+0.8+O+3&#8722;&#948;+cathodes+for+solid+oxide+fuel+cells.">Highly chromium contaminant tolerant BaO infiltrated La 0.6 Sr 0.4Co 0.2 Fe 0.8 O 3&#8722;&#948; cathodes for solid oxide fuel cells.</a> Physical Chemistry Chemical Physics. 17, 4870-4874 (2015).</li><li>Zhen, Y. D., Tok, A. I. Y., Jiang, S. P., Boey, F. Y. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=La(Ni,Fe)O3+as+a+cathode+material+with+high+tolerance+to+chromium+poisoning+for+solid+oxide+fuel+cells.">La(Ni,Fe)O3 as a cathode material with high tolerance to chromium poisoning for solid oxide fuel cells.</a> Journal of Power Sources. 170, 61-66 (2007).</li><li>Aphale, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+stability+of+SrxNiyOz+chromium+getter+for+solid+oxide+fuel+cells.">Synthesis and stability of SrxNiyOz chromium getter for solid oxide fuel cells.</a> Journal of the Electrochemical Society. 165, (2018).</li><li>Aphale, A., Hu, B., Singh, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-Cost+Getters+for+Gaseous+Chromium+Removal+in+High-Temperature+Electrochemical+Systems.">Low-Cost Getters for Gaseous Chromium Removal in High-Temperature Electrochemical Systems.</a> Jom. , 2-8 (2018).</li><li>Heo, S. H., Hu, B., Aphale, A., Uddin, M. A., Singh, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-temperature+chromium+poisoning+of+SOFC+cathode.">Low-temperature chromium poisoning of SOFC cathode.</a> ECS Transactions. 78, (2017).</li><li>Liang, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitigation+of+Chromium+Assisted+Degradation+of+LSM+Cathode+in+SOFC.">Mitigation of Chromium Assisted Degradation of LSM Cathode in SOFC.</a> ECS Transactions. 75, 57-64 (2017).</li><li>Ge, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxide+Scale+Morphology+and+Chromium+Evaporation+Characteristics+of+Alloys+for+Balance+of+Plant+Applications+in+Solid+Oxide+Fuel+Cells.">Oxide Scale Morphology and Chromium Evaporation Characteristics of Alloys for Balance of Plant Applications in Solid Oxide Fuel Cells.</a> Metallurgical and Materials Transactions A. 44, 193-206 (2013).</li><li>Hu, B., Mahapatra, M. K., Keane, M., Zhang, H., Singh, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+CO2+on+the+stability+of+strontium+doped+lanthanum+manganite+cathode.">Effect of CO2 on the stability of strontium doped lanthanum manganite cathode.</a> Journal of Power Sources. 268, 404-413 (2014).</li><li>Hu, B., Keane, M., Mahapatra, M. K., Singh, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stability+of+strontium-doped+lanthanum+manganite+cathode+in+humidified+air.">Stability of strontium-doped lanthanum manganite cathode in humidified air.</a> Journal of Power Sources. 248, 196-204 (2014).</li><li>Li, C., Habler, G., Baldwin, L. C., Abart, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+improved+FIB+sample+preparation+technique+for+site-specific+plan-view+specimens:+A+new+cutting+geometry.">An improved FIB sample preparation technique for site-specific plan-view specimens: A new cutting geometry.</a> Ultramicroscopy. 184, 310-317 (2018).</li></ol>

Authors do not have anything to disclose.

The experimental results clearly demonstrate the effectiveness of chromium getters during long-term chromium transpiration tests and electrochemical tests. Presence of getters successfully mitigates the contamination of the electrode which otherwise would lead to rapid increase in polarization resistance and electrochemical performance degradation.
The formation of gas phase chromium species from chromia is favored and enhanced with an increase of water vapor concentration (humidity level)<sup...

Solid oxide fuel cell (SOFC) power system, a high temperature direct electrochemical energy conversion device, offers an environmentally friendly pathway to generate electricity from a wide variety of fossil and renewable fuels. SOFC technology finds its applications in centralized as well as distributed power generation areas1. This technology relies on electrochemical conversion of chemical energy stored in the fuels into electricity. Numerous advantages are offered by SOFCs in terms of high energy efficiency, high quality heat, ease of modularity, and no or negligible carbon footprints2. Several individual SOFC cells are connected in series or parallel fashion (namely SOFC stacks) to obtain desired output voltage. SOFC stacks consist of components such as dense electrolyte, porous electrodes, interconnection (IC) and seals3,4. Anode and cathode of adjacent cells are connected using IC, which not only serves as a separator to prevent any mixing of oxidant with fuel but also provides electrical connection between the adjacent anode and cathode5.
Improvements over decades of research and development in materials engineering have led to reduction in operating temperature for SOFCs, enabling replacements of ceramics materials with inexpensive stainless-steel alloys for the fabrication of electrochemically active cell and stack components and balance-of-plant (BOP) sub-systems. Commercially available ferritic and austenitic stainless steels are utilized for the fabrication of system components due to their low cost, matched coefficient of thermal expansion (CTE) and resistance to oxidation and corrosion at high operating temperatures6. Formation of Cr2O3 type passivating oxide scale on the alloy surface acts as a barrier layer against inward diffusion of oxygen from air or outward diffusion of cations from bulk alloy7.
In the presence of humidified air, Cr2O3 undergoes significant chemical transformation leading to hydrated chromium vapor species formation at SOFC operating temperatures. The gaseous chromium vapor is subsequently carried through the air stream into the cathode leading to surface and interface reactions with the cathode materials. Such cathode experiences both ohmic and non-ohmic increases in the polarization and electrical performance degradation. Details of the cathode degradation mechanisms have been illustrated elsewhere8,9,10.
The state-of-the-art methods to reduce or eliminate the above cathode degradation processes commonly consist of modifications of the alloy chemistry, application of surface coating and the use of chromium tolerant cathodes11,12. Although these techniques have demonstrated reduction of the cathode degradation due to Cr vapor interactions (namely Cr poisoning) for short-term, long-term efficacy for performance stability remains a concern, mainly due to cracking and spallation within the coating and interdiffusion of cations.
We have demonstrated a novel method to mitigate the problem of chromium poisoning by capturing the incoming chromium vapor before it reacts with the cathode materials13. The getters have been synthesized from low-cost alkaline earth and transition metal oxides using conventional ceramic processing techniques. The cost advantage of this approach is use of non-noble and non-strategic materials as well as conventional processing methods to fabricate getters for the mitigation of cathode degradation arising from airborne contaminants. The placement of the getter can be tailored to capture chromium vapor arising from BOP components or it can also be tailored to be placed within the electrochemically active stack components14,15. Here, we present methods to validate the chromium getters using transpiration and electrochemical tests. Experimental setup and characterization results will also be demonstrated to show the getter effectiveness and the mechanisms of Cr capture on the getter under typical SOFC operating conditions.

<table><tbody><tr><td>&lt;strong&gt;Sr(NO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;&lt;/strong&gt;</td><td>Sigma-Aldrich</td><td>243426</td><td>Getter precursor material</td></tr><tr><td>&lt;strong&gt;Ni(NO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;-6H&lt;sub&gt;2&lt;/sub&gt;O&lt;/strong&gt;</td><td>Alfa Aesar</td><td>A15540</td><td>Getter precursor material</td></tr><tr><td>&lt;strong&gt;NH&lt;sub&gt;4&lt;/sub&gt;OH&lt;/strong&gt;</td><td>Alfa Aesar</td><td>L13168</td><td>Getter precursor material</td></tr><tr><td>&lt;strong&gt;Pt ink&lt;/strong&gt;</td><td>ESL ElectroScience</td><td>5051</td><td>Current collector paste</td></tr><tr><td>&lt;strong&gt;Pt wire&lt;/strong&gt;</td><td>Alfa Aesar</td><td>10288</td><td>Current collector wire</td></tr><tr><td>&lt;strong&gt;Pt gause&lt;/strong&gt;</td><td>Alfa Aesar</td><td>40935</td><td>Current collector</td></tr><tr><td>&lt;strong&gt;Cr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; powder&lt;/strong&gt;</td><td>Alfa Aesar</td><td>12286</td><td>Chromium source</td></tr><tr><td>&lt;strong&gt;Nitric acid (HNO&lt;sub&gt;3&lt;/sub&gt;)&lt;/strong&gt;</td><td>Sigma-Aldrich</td><td>438073</td><td>Chromium extraction</td></tr><tr><td>&lt;strong&gt;Potassium permanganate (KMnO&lt;sub&gt;4&lt;/sub&gt;)&lt;/strong&gt;</td><td>Alfa Aesar</td><td>A12170</td><td>Chromium extraction</td></tr><tr><td>&lt;strong&gt;LSM paste&lt;/strong&gt;</td><td>Fuelcellmaterials</td><td>18007</td><td>Cathode</td></tr><tr><td>&lt;strong&gt;YSZ electrolyte&lt;/strong&gt;</td><td>Fuelcellmaterials</td><td>211102</td><td>Electrolyte</td></tr><tr><td>&lt;strong&gt;Alumina fiber board&lt;/strong&gt;</td><td>Zircar</td><td>GJ0014</td><td>Getter substrate</td></tr><tr><td>&lt;strong&gt;Ceramabond paste&lt;/strong&gt;</td><td>AREMCO</td><td>552-VFG</td><td>For cell sealing</td></tr><tr><td>&lt;strong&gt;ICP-MS (7700s)&lt;/strong&gt;</td><td>Agilent</td><td>NA</td><td>For Cr analysis</td></tr><tr><td>&lt;strong&gt;Potentiostat (VMP3)&lt;/strong&gt;</td><td>Biologic</td><td>NA</td><td>For EIS/I-t measurement</td></tr><tr><td>&lt;strong&gt;FIB (Helios Nanolab 460F1)&lt;/strong&gt;</td><td>FEI</td><td>NA</td><td>For Nano-sample preparation</td></tr><tr><td>&lt;strong&gt;TEM (Talos F200X S/TEM)&lt;/strong&gt;</td><td>FEI</td><td>NA</td><td>For composition analysis</td></tr></tbody></table>

development and validation of chromium getters for solid oxide fuel cell power systems

Degradation of cathode in solid oxide fuel cells (SOFC) remains a major concern for the long-term performance stability and operational reliability. The presence of gas phase chromium species in air has demonstrated significant cathode performance degradation during long-term exposure due to unwanted compound formation at the cathode and electrolyte interface which retards the oxygen reduction reaction (ORR). We have demonstrated a novel method to mitigate the cathode degradation using chromium getters which capture the gas phase chromium species before it is ingested in the cathode chamber. Low-cost getter materials, synthesized from alkaline earth and transition metal oxides, are coated on the cordierite honeycomb substrate for application in the SOFC power systems. As-fabricated getters have been screened by chromium transpiration tests for 500 h in humidified air atmosphere in presence of chromium vapor. Selected getters have been further validated utilizing electrochemical tests. Typically, electrochemical performance of SOFCs (lanthanum strontium manganite (LSM) &#449; yttria stabilized zirconia (YSZ) &#449; Pt) was measured at 850 &#176;C in the presence and absence of Cr getter. For the 100 h cell tests containing getters, stable electrochemical performance was maintained, whereas the cell performance in the absence of Cr getters rapidly decreased in 10 h. Analyses of Nyquist plots indicated significant increase in the polarization resistance within the first 10 h of the cell operation. Characterization results from posttest SOFCs and getters have demonstrated the high efficiency of chromium capture for the mitigation of cell degradation.

A Cr transpiration experiment is a screening test for the selection of Cr getters. Cr transpiration setup was utilized to validate the performance of chromium getter under the SOFC operating conditions. Experiments were conducted in the presence of a chromium getter operated at 850 &#176;C in humidified (3% H2O) air for 500 h. Visual observations during Cr transpiration tests indicated significant discoloration of the outlet elbow during 500 h in the absence of getter. However,...

Watch this Scientific Journal Video about Development and Validation of Chromium Getters for Solid Oxide Fuel Cell Power Systems at JoVE.com

Development and Validation of Chromium Getters for Solid Oxide Fuel Cell Power Systems

Cathode poisoning from airborne contaminants in trace levels remains a major concern for long-term stability of high-temperature electrochemical systems. We provide a novel method to mitigate the cathode degradations using getters, which capture airborne contaminants at high temperature before entering electrochemically active stack area.

Degradation of cathode in solid oxide fuel cells (SOFC) remains a major concern for the long-term performance stability and operational reliability. The ...

development-validation-chromium-getters-for-solid-oxide-fuel-cell

Research

JoVE Journal

Chemistry

7.1K Views.  University of Connecticut. Cathode poisoning from airborne contaminants in trace levels remains a major concern for long-term stability of high-temperature electrochemical systems. We provide a novel method to mitigate the cathode degradations using getters, which capture airborne contaminants at high temperature before entering electrochemically active stack area.

Video: Development and Validation of Chromium Getters for Solid Oxide Fuel Cell Power Systems

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen 1-7. The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion2. Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation8-12. It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition8, 10, 13, 14 ("coking") and sulfur poisoning11, 15 and the manner in which surface modifications stave off this degradation16. The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM and STM, other properties such as local electronic states, ion diffusion coefficient and surface potential can also be investigated17-22. In this work, electrochemical measurements, Raman spectroscopy, and SPM were used in conjunction with a novel test electrode platform that consists of a Ni mesh electrode embedded in an yttria-stabilized zirconia (YSZ) electrolyte. Cell performance testing and impedance spectroscopy under fuel containing H2S was characterized, and Raman mapping was used to further elucidate the nature of sulfur poisoning. In situ Raman monitoring was used to investigate coking behavior. Finally, atomic force microscopy (AFM) and electrostatic force microscopy (EFM) were used to further visualize carbon deposition on the nanoscale. From this research, we desire to produce a more complete picture of the SOFC anode.

We present a unique platform for characterizing electrode surfaces in solid oxide fuel cells (SOFCs) that allows simultaneous performance of multiple characterization techniques (e.g. in situ Raman spectroscopy and scanning probe microscopy alongside electrochemical measurements). Complementary information from these analyses may help to advance toward a more profound understanding of electrode reaction and degradation mechanisms, providing insights into rational design of better materials for SOFCs.

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen ...

Engineering

On the Preparation and Testing of Fuel Cell Catalysts Using the Thin Film Rotating Disk Electrode Method

We present a step-by-step tutorial to prepare proton exchange membrane fuel cell (PEMFC) catalysts, consisting of Pt nanoparticles (NPs) supported on a high surface area carbon, and to test their performance in thin film rotating disk electrode (TF-RDE) measurements. The TF-RDE methodology is widely used for catalyst screening; nevertheless, the measured performance sometimes considerably differs among research groups. These uncertainties impede the advancement of new catalyst materials and, consequently, several authors discussed possible best practice methods and the importance of benchmarking.
The visual tutorial highlights possible pitfalls in the TF-RDE testing of Pt/C catalysts. A synthesis and testing protocol to assess standard Pt/C catalysts is introduced that can be used together with polycrystalline Pt disks as benchmark catalysts. In particular, this study highlights how the properties of the catalyst film on the glassy carbon (GC) electrode influence the measured performance in TF-RDE testing. To obtain thin, homogeneous catalyst films, not only the catalyst preparation, but also the ink deposition and drying procedures are essential. It is demonstrated that an adjustment of the ink&#39;s pH might be necessary, and how simple control measurements can be used to check film quality. Once reproducible TF-RDE measurements are obtained, determining the Pt loading on the catalyst support (expressed as Pt wt%) and the electrochemical surface area is necessary to normalize the determined reaction rates to either surface area or Pt mass. For the surface area determination, so-called CO stripping, or the determination of the hydrogen underpotential deposition (Hupd) charge, are standard. For the determination of the Pt loading, a straightforward and cheap procedure using digestion in aqua regia with subsequent conversion of Pt(IV) to Pt(II) and UV-vis measurements is introduced.

Preparing and testing Pt/C fuel cell catalysts is subject to continuous discussion in the scientific community with respect to reproducibility and best practice. With the presented work, we intend to present a step-by-step tutorial to make and test Pt/C catalysts, which can serve as benchmark for novel catalyst systems.

We present a step-by-step tutorial to prepare proton exchange membrane fuel cell (PEMFC) catalysts, consisting of Pt nanoparticles (NPs) supported on a ...

Environment

Combustion Characterization and Model Fuel Development for Micro-tubular Flame-assisted Fuel Cells

Combustion based power generation has been accomplished for many years through a number of heat engine systems. Recently, a move towards small scale power generation and micro combustion as well as development in fuel cell research has created new means of power generation that combine solid oxide fuel cells with open flames and combustion exhaust. Instead of relying upon the heat of combustion, these solid oxide fuel cell systems rely on reforming of the fuel via combustion to generate syngas for electrochemical power generation. Procedures were developed to assess the combustion by-products under a wide range of conditions. While theoretical and computational procedures have been developed for assessing fuel-rich combustion exhaust in these applications, experimental techniques have also emerged. The experimental procedures often rely upon a gas chromatograph or mass spectrometer analysis of the flame and exhaust to assess the combustion process as a fuel reformer and means of heat generation. The experimental techniques developed in these areas have been applied anew for the development of the micro-tubular flame-assisted fuel cell. The protocol discussed in this work builds on past techniques to specify a procedure for characterizing fuel-rich combustion exhaust and developing a model fuel-rich combustion exhaust for use in flame-assisted fuel cell testing. The development of the procedure and its applications and limitations are discussed.

A protocol for creating a model fuel-rich combustion exhaust is developed through combustion characterization and is applied for micro-tubular flame-assisted fuel cell testing and research.

Combustion based power generation has been accomplished for many years through a number of heat engine systems. Recently, a move towards small scale power ...

A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid and deployment of renewable energy technologies. Among the many flow battery chemistries, non-aqueous flow batteries have the potential to achieve high energy density because of the broad voltage windows of non-aqueous electrolytes. However, significant technical hurdles exist currently limiting non-aqueous flow batteries to demonstrate their full potential, such as low redox concentrations, low operating currents, under-explored battery status monitoring, etc. In an attempt to address these limitations, we recently reported a non-aqueous flow battery based on a highly soluble, redox-active organic nitronyl nitroxide radical compound, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO). This redox material exhibits an ambipolar electrochemical property, and therefore can serve as both anolyte and catholyte redox materials to form a symmetric flow battery chemistry. Moreover, we demonstrated that Fourier transform infrared (FTIR) spectroscopy could measure the PTIO concentrations during the PTIO flow battery cycling and offer reasonably accurate detection of the battery state of charge (SOC), as cross-validated by electron spin resonance (ESR) measurements. Herein we present a video protocol for the electrochemical evaluation and SOC diagnosis of the PTIO symmetric flow battery. With a detailed description, we experimentally demonstrated the route to achieve such purposes. This protocol aims to spark more interests and insights on the safety and reliability in the field of non-aqueous redox flow batteries.

We present the protocols for electrochemically evaluating a symmetric non-aqueous organic redox flow battery and for diagnosing its state of charge using FTIR.

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid ...

Simple Methods for the Preparation of Non-noble Metal Bulk-electrodes for Electrocatalytic Applications

The rock material pentlandite with the composition Fe4.5Ni4.5S8 was synthesized via high temperature synthesis from the elements. The structure and composition of the material was characterized via powder X-ray diffraction (PXRD), M&#246;ssbauer spectroscopy (MB), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and energy dispersive X-ray spectroscopy (EDX). Two preparation methods of pentlandite bulk electrodes are presented. In the first approach a piece of synthetic pentlandite rock is directly contacted via a wire ferrule. The second approach utilizes pentlandite pellets, pressed from finely ground powder, which is immobilized in a Teflon casing. Both electrodes, whilst being prepared by an additive-free method, reveal high durability during electrocatalytic conversions in comparison to common drop-coating methods. We herein showcase the striking performance of such electrodes to accomplish the hydrogen evolution reaction (HER) and present a standardized method to evaluate the electrocatalytic performance by electrochemical and gas chromatographic methods. Furthermore, we report stability tests via potentiostatic methods at an overpotential of 0.6 V to explore the material limitations of the electrodes during electrolysis under industrial relevant conditions.

A facile preparation method of electrodes using the bulk material Fe4.5Ni4.5S8 is presented. This method provides an alternative technique to conventional electrode fabrication and describes prerequisites for unconventional electrode materials including a straightforward electrocatalytic testing method.

The rock material pentlandite with the composition Fe4.5Ni4.5S8 was synthesized via high temperature synthesis from the elements. The structure and ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

A Guide to Concentration Alternating Frequency Response Analysis of Fuel Cells

An experimental setup capable of generating a periodic concentration input perturbation of oxygen was used to perform concentration-alternating frequency response analysis (cFRA) on proton-exchange membrane (PEM) fuel cells. During cFRA experiments, the modulated concentration feed was sent to the cathode of the cell at different frequencies. The electric response, which can be cell potential or current depending on the control applied on the cell, was registered in order to formulate a frequency response transfer function. Unlike traditional electrochemical impedance spectroscopy (EIS), the novel cFRA methodology makes it possible to separate the contribution of different mass transport phenomena from the kinetic charge transfer processes in the frequency response spectra of the cell. Moreover, cFRA is able to differentiate between varying humidification states of the cathode. In this protocol, the focus is on the detailed description of the procedure to perform cFRA experiments. The most critical steps of the measurements and future improvements to the technique are discussed.

We present a protocol for concentration alternating frequency response analysis of fuel cells, a promising new method of studying fuel cell dynamics.

An experimental setup capable of generating a periodic concentration input perturbation of oxygen was used to perform concentration-alternating frequency ...

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity in aqueous CO2 reduction. Different from traditional metal nanocrystals, the synthesis of metal single atoms involves a matrix material that can confine those single atoms and prevent them from aggregation. We report an electrospinning and thermal annealing method to prepare Ni single atoms dispersed and coordinated in a graphene shell, as active centers for CO2 reduction to CO. During the synthesis, N dopants play a critical role in generating graphene vacancies to trap Ni atoms. Aberration-corrected scanning transmission electron microscopy and three-dimensional atom probe tomography were employed to identify the single Ni atomic sites in graphene vacancies. Detailed setup of electrochemical CO2 reduction apparatus coupled with an on-line gas chromatography is also demonstrated. Compared to metallic Ni, Ni single atom catalyst exhibit dramatically improved CO2 reduction and suppressed H2 evolution side reaction.

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Here, we present a protocol for the synthesis and electrochemical testing of transition metal single atoms coordinated in graphene vacancies as active centers for selective carbon dioxide reduction to carbon monoxide in aqueous solutions.

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity ...

Metal Oxide Heterojunction for Photocatalytic Activities

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale applications. Sol-gel-based solution combustion synthesis (SG-SCS) is a simple method to produce ordered porous materials. In this regard, Pearson&#39;s hard and soft acids and bases theory assists in selecting host-dopant reactivity to form a proper heterojunction.
The formation of a heterojunction also changes the essential properties of the materials, improving photocatalysis via charge transfer or synergistic activities. A calcination temperature of 500 &#176;C is ideal for this process based on the results of the stability assessment via a differential thermogravimetry ratio analysis (DTG).
The nanoscale dimensions of the nanoparticles (NPs) and nanocomposites (NCs) generated were validated using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Furthermore, the scanning electron microscopy micrographs and BET analyses confirmed the porosity nature of the materials. HRTEM, X-ray photoelectron spectroscopy, and energy-dispersive X-ray investigations established the materials composition. The study found that NCs degraded the acid orange 8 (AO8) color more efficiently than bare ZnO.

The development of a heterojunction boosts the photocatalytic activities of solution combustion synthesis, which is a time-/energy-efficient process. Advanced analytical characterization techniques were used in this protocol to evaluate the materials&#39; characteristics, and nanocomposites demonstrated improved acid orange-8 dye degradation.

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale ...

Exploring Innovative 3D Electrodes for Hydrogen Peroxide Fuel Cells

Membraneless Hydrogen Peroxide Fuel Cells as a Promising Clean Energy Source

In an in-depth investigation of membraneless hydrogen peroxide-based fuel cells (H2O2 FCs), hydrogen peroxide (H2O2), a carbon-neutral compound, is demonstrated to undergo electrochemical decomposition to produce H2O, O2, and electrical energy. The unique redox properties of H2O2 position it as a viable candidate for sustainable energy applications. The proposed membraneless design addresses the limitations of conventional fuel cells, including fabrication complexities and design challenges. A novel three-dimensional electrode, synthesized via electroplating techniques, is introduced. Constructed from Au-electroplated carbon fiber cloth combined with Ni-foam, this electrode showcases enhanced electrochemical reaction kinetics, leading to an increased power density for H2O2 FCs. The performance of fuel cells is intricately linked to the pH levels of the electrolyte solution. Beyond FC applications, such electrodes hold potential in portable energy systems and as high surface area catalysts. This study emphasizes the significance of electrode engineering in optimizing the potential of H2O2 as an environmentally friendly energy source.

Author Spotlight: Design and Evaluation of Au-Electroplated Carbon Fiber Cloth Electrodes for Hydrogen Peroxide Fuel Cells 

This protocol introduces the design and evaluation of innovative three-dimensional electrodes for hydrogen peroxide fuel cells, utilizing Au-electroplated carbon fiber cloth and Ni-foam electrodes. The research findings highlight hydrogen peroxide's potential as a promising candidate for sustainable energy technologies.

In an in-depth investigation of membraneless hydrogen peroxide-based fuel cells (H2O2 FCs), hydrogen peroxide (H2O2), a carbon-neutral compound, is ...