Financial support was provided by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under contract number DE-AC36-08GO28308 to NREL.

1. Synthesis of Pt-Ni Nanowires
<ol>
	<li>To begin the displacement process, suspend the nickel nanowire template in water and heat it to 90 &#176;C.
	<ol>
		<li>Add 40 mg of commercially available, nickel nanowires to 20 mL of deionized water in a 50 mL centrifuge tube. Sonicate it for 5 min. 
		&#8203;NOTE: The nanowires are approximately 150-250 nm in diameter and 100-200 &#181;m in length.</li>
		<li>Transfer the suspended nanowires to a 250 mL glass round bottom flask and add 60 mL of deionized water. Heat the flask to 90 &#176;C in a mineral oil bath. Stir the reaction mixture at 500 rpm with a polytetrafluoroethylene paddle connected to a glass shaft and electric stirrer.</li>
	</ol>
	</li>
	<li>Form the Pt-Ni nanowires by spontaneous galvanic displacement.
	<ol>
		<li>Add 8.1 mg of potassium tetrachloroplatinate to 15 mL of deionized water. Add the solution to a 20 mL syringe with approximately 8 cm of 0.318 cm polyurethane-based tubing attached to the tip. Place the syringe in an automated syringe pump and set the rate to 1 mL/min.</li>
		<li>Start the syringe pump and allow the pump to add the solution to the round bottom flask over 15 min. Heat the flask at 90 &#176;C for 2 h.</li>
		<li>Centrifuge the solution at 2,500 x g for 15 min, and pour the supernatant into a waste stream. Resuspend the solidswith bath sonication (approximately 10 s) using fresh solution (water or 2-propanol, as specified). Centrifuge the solution again and remove the supernatant. Repeat the washing process three times with deionized water and then once with 2-propanol.</li>
		<li>Dry the Pt-Ni nanowires at 40 &#176;C in a vacuum oven overnight (approximately 16 h).</li>
	</ol>
	</li>
</ol>
2. Check Composition with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).
Note: Catalyst composition should be 7.3 &#177; 0.3 wt. % Pt.
<ol>
	<li>Digest 1 mg of sample in 10 mL of aqua regia at room temperature overnight.</li>
	<li>Dilute to concentrations of 200, 20, and 2 ppb, with a matrix matching of the dilutions to 1.5% hydrochloric and 0.5% nitric acid.
	<ol>
		<li>Add 20 &#181;L of digestate into 9.98 mL of stock solution (1.5% hydrochloric and 0.5% nitric acid) for 200 ppb; 2 &#181;L of digestate into 10.00 mL of stock solution (1.5% hydrochloric and 0.5% nitric acid) for 20 ppb; and 0.2 &#181;L of digestate into 10.00 mL of stock solution (1.5% hydrochloric and 0.5% nitric acid) for 2 ppb. Filter the dilutions using a 0.4 &#181;m polytetrafluoroethylene-based filter.</li>
	</ol>
	</li>
</ol>
3. Post-synthesis Process of the Pt-Ni Nanowires by Annealing and Acid Leaching.
<ol>
	<li>Hydrogen anneal the synthesized Pt-Ni nanowires.</li>
	<li>Add the entire nanowire sample to a tubular furnace. Apply vacuum to the tube overnight. 
	&#8203;NOTE: Since gas flow (hydrogen, oxygen) was used at elevated temperature in the tubular furnace, safety considerations were required. The tube-gas connections were built to ensure that the apparatus could handle vacuum and 500 Torr of back pressure during operation. The tube outlet was vented to exhaust, and the entire furnace was placed in an enclosure vented to an exhaust line.
	<ol>
		<li>Feed a low flow rate of hydrogen into the tube with 500 Torr of back pressure.</li>
		<li>Heat the sample to 250 &#176;C for 2 h, using a 10 &#176;C/min ramp rate.</li>
		<li>Allow for the sample to cool to room temperature naturally.</li>
	</ol>
	</li>
	<li>Acid leach the hydrogen annealed Pt-Ni nanowires.
	<ol>
		<li>Add 25 mg of the nanowires to 20 mL of deionized water and bath sonicate it. Transfer the suspended nanowires to a 100 mL round bottom flask.</li>
		<li>Add room temperature diluted nitric acid to the flask (25 mL of 0.2 M nitric acid to 25 mL of water/nanowire suspension), to bring the flask contents to 50 mL of 0.1 M nitric acid, and shake the flask to ensure a uniform concentration. Add the nitric acid all at once.</li>
		<li>Connect the flask to a Schlenk line. Turn on the vacuum for 10 min and then close off the vacuum. Slowly add nitrogen gas into the line and allow the flask to proceed at room temperature for 2 h. Remove the flask from the Schlenk line and wash the products as described in step 1.2.3.</li>
		<li>Check the composition with ICP-MS, which should be 15.2 &#177; 0.3 wt. % Pt.</li>
	</ol>
	</li>
	<li>Oxygen anneal the acid leached Pt-Ni nanowires.
	<ol>
		<li>Add the nanowires to a commercially available tubular furnace. Apply vacuum to the tube overnight.</li>
		<li>Feed a low flow rate of oxygen into the tube with 500 Torr of back pressure.</li>
		<li>Heat the sample to 175 &#176;C for 2 h, using a 10 &#176;C/min ramp rate.</li>
		<li>Allow for the sample to cool to room temperature naturally.</li>
	</ol>
	</li>
</ol>
4. Electrochemically Characterize the Nanowires in Rotating Disk Electrode (RDE) Half-Cells8
<ol>
	<li>Coat the glassy carbon working electrodes.
	<ol>
		<li>Add catalyst, which contains 73 &#181;g of Pt, to 7.6 mL of deionized water in a 20 mL scintillation vial, and then add 2.4 mL of 2-propanol. The vial contents are subsequently referred to as the ink. Ice the ink for 5 min and then add 10 &#181;L of a commercially available ionomer. 
		NOTE: For the as-synthesized and hydrogen annealed catalyst, 1 mg (7.3 wt. % Pt) should be used. For the acid leached and oxygen annealed catalyst, 480 &#181;g (15.2 wt. % Pt) should be used.</li>
		<li>Sonicate the ink in ice, 30 s by horn followed by 20 min by bath and 30 s by horn. Add 7.5 mL of the ink to 0.5 mg of graphitized carbon nanofibers.</li>
		<li>Sonicate the ink in ice, 30 s by horn followed by 20 min by bath and 30 s by horn. Pipette 10 &#181;L of ink onto a glassy carbon working electrode (5 mm outer diameter), with the inverted electrode rotating at 100 rpm. After pipetting the ink, increase the rotation to 700 rpm.</li>
		<li>Sonicate the ink again (30 s horn, 20 min bath, 30 s horn) while the electrode dries and pipette an additional ink (10 &#181;L) onto the electrode. Continue the coating process to increase the loading to 1.9 &#181;g cmelec-2, five 10 &#181;L drops of ink.</li>
	</ol>
	</li>
	<li>Assemble the RDE test station.
	<ol>
		<li>Soak the glassware overnight in concentrated sulfuric acid. Then, soak the glassware overnight in a commercially available substitute for chromic acid. Boil eight times in deionized water. Assemble the glassware, by connecting the working, counter, and reference electrodes to the main testing cell. 
		NOTE: The RDE half-cells use a three-electrode configuration. The working and counter electrodes were glassy carbon and Pt mesh, respectively. The reference electrode was a reversible hydrogen electrode (RHE), a Pt wire contained in a glass bubbler with 0.1 M perchloric acid electrolyte.</li>
		<li>Fill the RDE half-cell with 0.1 M perchloric acid. Connect the working electrode to a commercially available modulated speed controller, and submerge the working electrode tip.</li>
		<li>Take electrochemical measurements with a commercially available potentiostat. Purge the electrolyte with nitrogen for 7 min.</li>
	</ol>
	</li>
	<li>Take electrochemical surface areas.
	<ol>
		<li>Input parameters into an automated cyclic voltammetry file supplied by the potentiostat manufacturer. Set the cycle number to 50, the scan rate to 100 mV s-1, the lower potential to 0.025 V, and the upper potential to 1.4 V. Run the cyclic voltammetry file and discard the electrolyte. Refill with 0.1 M perchloric acid and purge with carbon monoxide.</li>
		<li>Input parameters into an automated potential hold file supplied by the potentiostat manufacturer. Set the potential 0.1 V and the time to 20 min, and start rotating the working electrode at 2,500 rpm. Run the potential hold file: for the first 10 min of the program, purge carbon monoxide; for the second 10 min of the program, purge nitrogen. During the last 30 s of the hold, turn off the rotation and set the bubbler to blanket the electrolyte.</li>
		<li>Input parameters into an automated cyclic voltammetry file supplied by the potentiostat manufacturer. Set the cycle number to 3, the scan rate to 20 mV s-1, the start potential to 0.1 V, the lower potential to 0.025 V, and the upper potential to 1.2 V. Run the cyclic voltammetry file.</li>
	</ol>
	</li>
	<li>Take oxygen reduction polarization curves.
	<ol>
		<li>Purge the electrolyte with oxygen for at least 7 min with the working electrode rotating at 2,500 rpm.</li>
		<li>Set the oxygen purge to blanket the electrolyte and slow the working electrode rotation to 1,600 rpm.</li>
		<li>Input parameters into an automated linear sweep voltammetry file supplied by the potentiostat manufacturer. Set the cycle number to 10, the scan rate to 20 mV s-1, the start potential to -0.1 V, and the end potential to 1.05 V. Run the linear sweep voltammetry file. Discard the electrolyte.</li>
		<li>Refill with 0.1 M perchloric acid and purge with oxygen for at least 7 min. Rerun the linear sweep voltammetry file used in step 4.4.3.</li>
	</ol>
	</li>
	<li>Run durability tests.
	<ol>
		<li>Purge the electrolyte with nitrogen while rotating the working electrode at 2,500 rpm. Set the nitrogen purge to blanket the electrolyte and stop the working electrode rotation.</li>
		<li>Input parameters into an automated cyclic voltammetry file supplied by the potentiostat manufacturer. Set the cycle number to 30,000, the scan rate to 500 mV s-1, the lower potential to 0.6 V, and the upper potential to 1.0 V. Run the cyclic voltammetry file.</li>
		<li>After durability, take electrochemical surface areas and oxygen reduction polarization curves using the protocols supplied in steps 4.3 and 4.4.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Bregoli, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+Platinum+Crystallite+Size+on+Electrochemical+Reduction+of+Oxygen+in+Phosphoric-Acid.">Influence of Platinum Crystallite Size on Electrochemical Reduction of Oxygen in Phosphoric-Acid.</a> Electrochim. Acta. 23 (6), 489-492 (1978).</li><li>Debe, M. K., Parsonage, E. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanostructured+electrode+membranes.">Nanostructured electrode membranes.</a> US patent. , (1994).</li><li>Papandrew, A. 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=Oxygen+Reduction+Activity+of+Vapor-Grown+Platinum+Nanotubes.">Oxygen Reduction Activity of Vapor-Grown Platinum Nanotubes.</a> ECS Trans. 50 (2), 1397-1403 (2013).</li><li>Alia, S. M., Yan, Y. S., Pivovar, B. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Galvanic+displacement+as+a+route+to+highly+active+and+durable+extended+surface+electrocatalysts.">Galvanic displacement as a route to highly active and durable extended surface electrocatalysts.</a> Cat. Sci. Tech. 4 (10), 3589-3600 (2014).</li><li>Alia, S. M., 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=Platinum-Coated+Nickel+Nanowires+as+Oxygen-Reducing+Electrocatalysts.">Platinum-Coated Nickel Nanowires as Oxygen-Reducing Electrocatalysts.</a> ACS Cat. 4 (4), 1114-1119 (2014).</li><li>Alia, S. M., 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=Exceptional+Oxygen+Reduction+Reaction+Activity+and+Durability+of+Platinum-Nickel+Nanowires+through+Synthesis+and+Post-Treatment+Optimization.">Exceptional Oxygen Reduction Reaction Activity and Durability of Platinum-Nickel Nanowires through Synthesis and Post-Treatment Optimization.</a> ACS Omega. 2 (4), 1408-1418 (2017).</li><li>Norskov, J., 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=Origin+of+the+Overpotential+for+Oxygen+Reduction+at+a+Fuel-Cell+Cathode.">Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode.</a> J. Phys. Chem. B. 108 (46), 17886-17892 (2004).</li><li>Sha, Y., Yu, T. H., Merinov, B. V., Shirvanian, P., Goddard, W. 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Chem. 118 (18), 2963-2967 (2006).</li><li>Cui, C., Gan, L., Heggen, M., Rudi, S., Strasser, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compositional+segregation+in+shaped+Pt+alloy+nanoparticles+and+their+structural+behaviour+during+electrocatalysis.">Compositional segregation in shaped Pt alloy nanoparticles and their structural behaviour during electrocatalysis.</a> Nat Mater. 12 (8), 765-771 (2013).</li><li>Chen, 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=Highly+Crystalline+Multimetallic+Nanoframes+with+Three-Dimensional+Electrocatalytic+Surfaces.">Highly Crystalline Multimetallic Nanoframes with Three-Dimensional Electrocatalytic Surfaces.</a> Science. 343 (6177), 1339-1343 (2014).</li><li>Alia, S., 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=Porous+Platinum+Nanotubes+for+Oxygen+Reduction+and+Methanol+Oxidation+Reactions.">Porous Platinum Nanotubes for Oxygen Reduction and Methanol Oxidation Reactions.</a> Adv. Funct. Mater. 20 (21), 3742-3746 (2010).</li><li>Alia, S. M., 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=Platinum+Coated+Copper+Nanowires+and+Platinum+Nanotubes+as+Oxygen+Reduction+Electrocatalysts.">Platinum Coated Copper Nanowires and Platinum Nanotubes as Oxygen Reduction Electrocatalysts.</a> ACS Cat. 3 (3), 358-362 (2013).</li><li>Alia, S. M., 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=Platinum-Coated+Cobalt+Nanowires+as+Oxygen+Reduction+Reaction+Electrocatalysts.">Platinum-Coated Cobalt Nanowires as Oxygen Reduction Reaction Electrocatalysts.</a> ACS Cat. 4 (8), 2680-2686 (2014).</li><li>Alia, S. M., Duong, K., Liu, T., Jensen, K., Yan, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Palladium+and+Gold+Nanotubes+as+Oxygen+Reduction+Reaction+and+Alcohol+Oxidation+Reaction+Catalysts+in+Base.">Palladium and Gold Nanotubes as Oxygen Reduction Reaction and Alcohol Oxidation Reaction Catalysts in Base.</a> ChemSusChem. , (2014).</li><li>Alia, S. M., Pylypenko, S., Neyerlin, K. C., Kocha, S. S., Pivovar, B. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platinum+Nickel+Nanowires+as+Methanol+Oxidation+Electrocatalysts.">Platinum Nickel Nanowires as Methanol Oxidation Electrocatalysts.</a> J. Electrochem. Soc. 162 (12), 1299-1304 (2015).</li><li>Alia, S. 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The authors have nothing to disclose.

These protocols have been used to produce extended surface electrocatalysts with both high surface areas and specific activities in the oxygen reduction reaction8. By depositing Pt onto nanostructured templates, the nanowires avoided low coordinated sites and minimize particle size effects, producing specific activities more than 12 times greater than carbon-supported Pt nanoparticles. Using galvanic displacement as the synthesis approach also produced an approximate coating on the Ni template<sup...

Proton exchange membrane fuel cells are partially limited by the amount and cost of platinum required in the catalyst layer, which can account for half of fuel cell costs1. In fuel cells, nanomaterials are typically developed as oxygen reduction catalysts, since the reaction is kinetically slower than hydrogen oxidation. Carbon-supported Pt nanoparticles are often used as oxygen reduction electrocatalysts due to their high surface area; however, they have specific selective activity and are prone to durability losses.
Extended thin films offer potential benefits to nanoparticles by addressing these limitations. Extended Pt surfaces typically produce specific activities an order of magnitude greater than nanoparticles, by limiting less active facets and particle size effects, and have been shown to be durable under potential cycling2,3,4. While high mass activities have been achieved in extended surface electrocatalysts, improvements have been made primarily through increases in specific activity, and the catalyst type has been limited to Pt with a low surface area (10 m2 gPt-1)3,4,5.
Spontaneous galvanic displacement combines the aspects of corrosion and electrodeposition6. The process is generally governed by the standard redox potentials of the two metals, and the deposition typically occurs when the metal cation is more reactive than the template. The displacement tends to produce nanostructures that match the template morphology. By applying this technique to extended nanostructures, Pt-based catalysts can be formed that take advantage of the high specific oxygen reduction activity of extended thin films. Through partial displacement, small amounts of Pt have been deposited, and have produced materials with high surface areas (&#62; 90 m2 gPt-1)7,8.
These protocols involve hydrogen annealing to mix Pt and Ni zones and improve oxygen reduction activity. A number of studies have theoretically established the mechanism and experimentally confirmed an alloying effect in Pt oxygen reduction. Modeling and correlating Pt-OH and Pt-O binding to oxygen reduction activity suggest that Pt improvements can be made through lattice compression9,10. Alloying Pt with smaller transition metals has confirmed this benefit, and Pt-Ni has been investigated in a number of forms, including polycrystalline, faceted electrodes, nanoparticles, and nanostructures11,12,13,14.
Galvanic displacement has been used in Pt-oxygen reduction catalyst development with a variety of other templates, including silver, copper, and cobalt nanostructures15,16,17. The synthesis technique has also been used in the deposition of other metals and has produced electrocatalysts for fuel cells, electrolyzers, and the electrochemical oxidation of alcohols18,19,20,21. Similar protocols can also be adapted for the synthesis of nanomaterials with a wider range of electrochemical applications.

<table border="0" cellpadding="0" cellspacing="0" style="width:681px;" width="680">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="40">
			<td height="40" style="height:40px;width:215px;">Nickel nanowires</td>
			<td style="width:300px;">Plasmachem GmbH</td>
			<td style="width:167px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">250 mL round bottom flask</td>
			<td>Ace Glass</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Hot plate</td>
			<td>VWR International</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Mineral oil</td>
			<td>VWR International</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Potassium tetrachloroplatinate</td>
			<td>Sigma Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Syringe pump</td>
			<td>New Era Pump Systems</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Rotator</td>
			<td>Arrow Engineering</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Teflon paddle</td>
			<td>Ace Glass</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Glass shaft</td>
			<td>Ace Glass</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Split hinge tubular furnace</td>
			<td>Lindberg</td>
			<td></td>
			<td>Customized in-house</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Schlenk line</td>
			<td>Ace Glass</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Condensers</td>
			<td>VWR International</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Nitric acid</td>
			<td>Fisher Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">2-propanol</td>
			<td>Fisher Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Nafion ionomer (5 wt. %)</td>
			<td>Sigma Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Glassy carbon working electrode</td>
			<td>Pine Instrument Company</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">RDE glassware</td>
			<td>Precision Glassblowing</td>
			<td></td>
			<td>Customized in-house</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Platinum wire</td>
			<td>Alfa Aesar</td>
			<td></td>
			<td>Customized in-house</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Platinum mesh</td>
			<td>Alfa Aesar</td>
			<td></td>
			<td>Customized in-house</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">MSR Rotator</td>
			<td>Pine Instrument Company</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Potentiostat</td>
			<td>Metrohm Autolab</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

synthesis of platinum-nickel nanowires and optimization for oxygen reduction performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

Spontaneous galvanic displacement of Ni nanowires with Pt, using the specified amount, produced Pt-Ni nanowires that were 7.3 wt. % Pt (Figure 1 and Figure 2A). Some modification to the amount of Pt precursor may be required to reach the optimum Pt loading. Pt displacement is sensitive to the thickness of the surface Ni oxide layer, which can vary based on template age (air exposure) and upstream variability<sup ...

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Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

synthesis-platinum-nickel-nanowires-optimization-for-oxygen-reduction

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Chemistry

7.7K Views.  National Renewable Energy Laboratory.   The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Video: Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded synthesis strategy is used in which spherical seeds of CdSe are prepared first using a hot-injection technique. By controlling the crystal structure of the seed to be either wurtzite or zinc-blende, the subsequent hot-injection growth of CdS off of the seed results in either a rod-shaped or tetrapod-shaped nanocrystal, respectively. The phase and morphology of the synthesized nanocrystals are confirmed using X-ray diffraction and transmission electron microscopy, demonstrating that the nanocrystals are phase-pure and have a consistent morphology. The extinction coefficient and quantum yield of the synthesized nanocrystals are calculated using UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The rods and tetrapods exhibit extinction coefficients and quantum yields that are higher than that of the bare seeds. This synthesis demonstrates the precise arrangement of materials that can be achieved at the nanoscale by using a seeded synthetic approach.

A protocol for the seeded synthesis of rod-shaped and tetrapod-shaped multicomponent nanostructures consisting of CdS and CdSe is presented.

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded ...

Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties of the materials were investigated. We used a one pot sol-gel approach to intercalate gold nano particles in the walls of mesoporous silica. To start with the synthesis, P123 was used as template to form micelles. Then TESPTS was used as a surface modification agent to intercalate gold nano particles. Following this process, TEOS was added in as a silica source which underwent a polymerization process in acid environment. After hydrothermal processing and calcination, the final product was acquired. Several techniques were utilized to characterize the porosity, morphology and structure of the gold intercalated mesoporous silica. The results showed a stable structure of mesoporous silica after gold intercalation. Through the oxidation of benzyl alcohol as a benchmark reaction, the GMS materials showed high selectivity and recyclability.

Here, we present a protocol with a sol-gel process to synthesize gold intercalated in the walls of mesoporous materials (GMS), which is confirmed to possess a mesoporous matrix with gold intercalated in the walls imparting great stability and recyclability.

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties ...

Optimization of Synthetic Proteins: Identification of Interpositional Dependencies Indicating Structurally and/or Functionally Linked Residues

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional units (e.g., domains). Traditional consensus-building models fail to account for interpositional dependencies &#8211; functionally required covariation of residues that tend to appear simultaneously throughout evolution and across the phylogentic tree. These relationships can reveal important clues about the processes of protein folding, thermostability, and the formation of functional sites, which in turn can be used to inform the engineering of synthetic proteins. Unfortunately, these relationships essentially form sub-motifs which cannot be predicted by simple &#8220;majority rule&#8221; or even HMM-based consensus models, and the result can be a biologically invalid &#8220;consensus&#8221; which is not only never seen in nature but is less viable than any extant protein. We have developed a visual analytics tool, StickWRLD, which creates an interactive 3D representation of a protein alignment and clearly displays covarying residues. The user has the ability to pan and zoom, as well as dynamically change the statistical threshold underlying the identification of covariants. StickWRLD has previously been successfully used to identify functionally-required covarying residues in proteins such as Adenylate Kinase and in DNA sequences such as endonuclease target sites.

Synthetic protein sequences based on consensus motifs typically ignore co-evolving residues, that imply interpositional dependencies (IPDs). IPDs can be essential to activity, and designs that disregard them may result in suboptimal results. This protocol uses StickWRLD to identify IPDs and help inform rational protein design, resulting in more efficient results.

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional ...

Curtain Flow Column: Optimization of Efficiency and Sensitivity

Active Flow Technology (AFT) is a form of column technology that increases the separation performance of a HPLC column through the use of a specially purpose built multiport end-fitting(s). Curtain Flow (CF) columns belong to the AFT suite of columns, specifically the CF column is designed so that the sample is injected into the radial central region of the bed and a curtain flow of mobile phase surrounding the injection of solute prevents the radial dispersion of the sample to the wall. The column functions as an 'infinite diameter' column. The purpose of the design is to overcome the radial heterogeneity of the column bed, and at the same time maximize the sample load into the radial central region of the column bed, which serves to increase detection sensitivity. The protocol described herein outlines the system and CF column set up and the tuning process for an optimized infinite diameter 'virtual' column.

Here, we present a protocol for the operation and optimization of Active Flow Technology (AFT) column in Curtain flow (CF) mode for enhanced separation performance.

Active Flow Technology (AFT) is a form of column technology that increases the separation performance of a HPLC column through the use of a specially ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Hydroquinone Based Synthesis of Gold Nanorods

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the synthetic methods for the preparation of gold nanorods are still not fully optimized. In this paper we describe a new, highly efficient, two-step protocol based on the use of hydroquinone as a mild reducing agent. Our approach allows the preparation of nanorods with a good control of size and aspect ratio (AR) simply by varying the amount of hexadecyl trimethylammonium bromide (CTAB) and silver ions (Ag+) present in the "growth solution". By using this method, it is possible to markedly reduce the amount of CTAB, an expensive and cytotoxic reagent, necessary to obtain the elongated shape. Gold nanorods with an aspect ratio of about 3 can be obtained in the presence of just 50 mM of CTAB (versus 100 mM used in the standard protocol based on the use of ascorbic acid), while shorter gold nanorods are obtained using a concentration as low as 10 mM.

This paper describes a protocol for the synthesis of gold nanorods, based on the use of hydroquinone as reducing agent, plus the different mechanisms for controlling their size and aspect ratio.

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the ...

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 ...

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a ...

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various precursor noble metal ions with reducing agents in a 1:1 (v/v) ratio results in the formation of metal gels within seconds to minutes compared to much longer synthesis times for other techniques such as sol-gel. Conducting the reduction step in a microcentrifuge tube or small volume conical tube facilitates a proposed nucleation, growth, densification, fusion, equilibration model for gel formation, with final gel geometry smaller than the initial reaction volume. This method takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step, and as a consequence of reagent concentrations. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. After rinsing and freeze drying, the resulting aerogel structure is examined with scanning electron microscopy, X-ray diffractometry, and nitrogen gas adsorption. The synthesis method and characterization techniques result in a close correspondence of aerogel ligament sizes. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

A rapid, direct solution-based reduction synthesis method to obtain Au, Pd, and Pt aerogels is presented.

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a simple protocol for the multifunctional surface modification of NDs by using mussel-inspired polydopamine (PDA) coating. In addition, the functional layer of PDA on NDs could serve as a reducing agent to synthesize and stabilize metal nanoparticles. Dopamine (DA) can self-polymerize and spontaneously form PDA layers on ND surfaces if the NDs and dopamine are simply mixed together. The thickness of a PDA layer is controlled by varying the concentration of DA. A typical result shows that a thickness of ~5 to ~15 nm of the PDA layer can be reached by adding 50 to 100 &#181;g/mL of DA to 100 nm ND suspensions. Furthermore, the PDA-NDs are used as a substrate to reduce metal ions, such as Ag[(NH3)2]+, to silver nanoparticles (AgNPs). The sizes of the AgNPs rely on the initial concentrations of Ag[(NH3)2]+. Along with an increase in the concentration of Ag[(NH3)2]+, the number of NPs increases, as well as the diameters of the NPs. In summary, this study not only presents a facile method for modifying the surfaces of NDs with PDA, but also demonstrates the enhanced functionality of NDs by anchoring various species of interest (such as AgNPs) for advanced applications.

A facile protocol is presented to functionalize the surfaces of nanodiamonds with polydopamine.

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a ...