This work was supported by the Ministry of Science and Technology, R.O.C., under the funding number of NSC 102-2221-E-002-146-, MOST 103-2221-E-002-233-, and MOST 104-2628-E-002-016-MY3.

1. Construction of a SLFB Beaker Cell with a Sodium Acetate Additive
NOTE: This section describes the procedure to construct a SLFB beaker cell with an additive for long-term cycling experiment. The protocol includes the electrolyte preparation with and without additive, electrode pretreatment, cell assembly, and efficiency calculations.
<ol>
	<li>Preparation of lead methanesulfonate (1 L, 1 M as an example)
	<ol>
		<li>In the fume hood, add 274.6 g of methanesulfonic acid (MSA, 70%) to a beaker stirring with a stir bar. Dissolve the MSA with 300 mL of deionized (DI) water.</li>
		<li>Prepare 223.2 g of lead (II) oxide (98%) and add in increments to the aforementioned beaker until the prepared lead oxide is completely dissolved.</li>
		<li>Filter through the B&#252;chner funnel with 70 mm cellulose filter paper to separate any undissolved lead oxide.</li>
		<li>Repeat this procedure for 3 times. Add DI water to reach 1 L in total volume.</li>
	</ol>
	</li>
	<li>Preparation of electrolyte without additive (300 mL)
	<ol>
		<li>Add 20.595 g of MSA (70%) to a beaker. Add 150 mL of prepared 1 M lead methanesulfonate to the same beaker.</li>
		<li>Add DI water to reach 300 mL in total volume and stir the electrolyte until uniformly mixed, which results in a solution of 0.5 M lead methanesulfonate mixed with 0.5 M MSA.</li>
	</ol>
	</li>
	<li>Preparation of electrolyte with sodium acetate (300 mL) 
	<ol>
		<li>Add 20.595 g of MSA (70%) to a beaker. Add 150 mL of prepared 1 M lead methanesulfonate to the same beaker.</li>
		<li>Add 1.23 g of NaOAc (98%) to the beaker as an additive agent.</li>
		<li>Add DI water to reach 300 mL in total volume and stir the electrolyte until uniformly mixed, which results in a solution of 0.5 M lead methanesulfonate, 0.5 M methanesulfonic acid, and 50 mM sodium acetate.</li>
	</ol>
	</li>
	<li>Pretreatment of the positive and negative electrodes
	<ol>
		<li>Repeatedly polish the positive (commercial carbon composite) and negative (nickel) electrodes with a sandpaper (aluminum oxide, P100) until no visible impurities are left and then rinse electrodes with DI water.</li>
		<li>Add 20.83 g of hydrogen chloride (35%) in 200 mL DI water and stir the solution until all of the hydrogen chloride is dissolved.</li>
		<li>Immerse the entire positive electrode in the prepared 1 M hydrogen chloride solution overnight to remove impurities at the electrode surface.</li>
		<li>Rinse the positive electrode thoroughly with DI water and dry the electrode with delicate task wipers. Tape one side of each electrode using polytetrafluoroethylene (PTFE) tape while exposing the other side of the electrodes.</li>
		<li>Prepare another solution with 3.03 g of potassium nitrate (99%) and 300 mL DI water, which results in a solution of 0.1 M potassium nitrate.</li>
		<li>Immerse the positive and negative electrodes in 0.1 M potassium nitrate with the exposed surface facing each electrode.</li>
		<li>Apply a potential of 1.80 V vs. Ag/AgCl to the positive electrode for 5 min. Subsequently, apply a potential of -1.0 V vs. Ag/AgCl to the positive electrode for 2 min.</li>
	</ol>
	</li>
	<li>Assemble the SLFB beaker cell
	<ol>
		<li>Attach the pretreated positive and negative electrodes to a home-made electrode positioning board for a fixed electrode distance. Place the positioning board together with electrodes in a beaker as schematically illustrated in Figure 1 and add electrolyte to the beaker until the designated level of immersion.</li>
		<li>Place a magnetic stirrer into the beaker, position the beaker on a hot plate and control the rotating rate of the stirrer. Connect the battery tester to the electrodes and cover the beaker cell with plastic wrap to prevent evaporation.</li>
	</ol>
	</li>
	<li>Calculate the battery efficiency
	<ol>
		<li>After galvanostatic charge and discharge, calculate the efficiency of the battery as the following: 
		Coulombic efficiency: <img alt="Equation 1" src="/files/ftp_upload/58484/58484eq1.jpg" /> 
		Voltage efficiency: <img alt="Equation 2" src="/files/ftp_upload/58484/58484eq2.jpg" /> 
		Energy efficiency: <img alt="Equation 3" src="/files/ftp_upload/58484/58484eq3.jpg" /> 
		Here, Q denotes coulombs of charged/discharged equivalent electrons, V the apply/output voltage, and E the total energy stored/consumed.</li>
	</ol>
	</li>
</ol>
2. Throwing Index Measurement
NOTE: This section describes the procedure to measure throwing index (TI) of the electrodeposit at positive electrodes in SLFB cells. Reversing the role of positive and negative electrodes delivers the other set of TI results. Here, TI is investigated by using a home-made Haring-Blum cell as schematically depicted in Figure 2.
<ol>
	<li>Measurement
	<ol>
		<li>Weigh and record two positive electrodes respectively before the experiments.</li>
		<li>Place the negative electrode at the center of a Haring-Blum cell and one positive electrode at a distance ratio of 1 from the negative electrode. Place the second positive electrode at another distance ratio from the negative electrode (take 6 as an example in Figure 2).</li>
		<li>Immerse the two positive electrodes and one negative electrode with the same immersed surface area (2 cm2 here) in the Haring-Blum cell with the electrolyte of interest.</li>
		<li>Apply a controlled current density (20 mA&#183;cm-2 here) at the electrodes by using a battery tester. Carry out the galvanostatic charge for a certain duration (30 min here).</li>
		<li>After plating, rinse the two positive electrodes with DI water and dry them at room temperature overnight.</li>
		<li>Weigh and record two positive electrodes again respectively and calculate the metal distribution ratio (MDR) according to the equation listed below.</li>
		<li>Repeat the aforementioned experiments by placing the second positive electrode at various linear distance ratios (LR) to acquire the TI diagram (varied from 6 to 1 here).</li>
	</ol>
	</li>
	<li>Calculation
	<ol>
		<li>As an example, consider the anode as the electrode of interest, and determine each data on the TI diagram by the measured MDR versus LR, which are calculated as the following: 
		<img alt="Equation 7" src="/files/ftp_upload/58484/58484eq7.jpg" /> 
		<img alt="Equation 8" src="/files/ftp_upload/58484/58484eq8.jpg" /></li>
	</ol>
	</li>
</ol>
3. SEM Sample Preparation
<ol>
	<li>Rinse the graphite electrode with DI water and dry at room temperature after electroplating.</li>
	<li>Slice graphite electrodes into the desired sample size by diamond saw with care. Cold mount the electrode sample and then mechanically polish it with 14, 8, and 3 &#956;m silicon carbide sand papers, subsequently.</li>
	<li>Further polish the samples with 1 &#956;m diamond suspension and 0.05 &#956;m Al2O3. Deposit the cold-mounted sample with platinum and attach it with copper tapes to ensure conductivity for SEM observation.</li>
</ol>

<ol>
	<li>Soloveichik, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+batteries:+current+status+&amp;+trends.">Flow batteries: current status &amp; trends.</a> Chemical Reviews. 115 (20), 11533-11558 (2015).</li><li>Ravikumar, M. K., Rathod, S., Jaiswal, N., Patil, S., Shukla, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+renaissance+in+redox+flow+batteries.">The renaissance in redox flow batteries.</a> Journal of Solid State Electrochemistry. 21 (9), 2467-2488 (2017).</li><li>Hazza, A., Pletcher, D., Wills, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery:+A+lead+acid+battery+based+on+an+electrolyte+with+soluble+lead+(II)+Part+I.+Preliminary+studies.">A novel flow battery: A lead acid battery based on an electrolyte with soluble lead (II) Part I. Preliminary studies.</a> Physical Chemistry Chemical Physics. 6 (8), 1773-1778 (2004).</li><li>Pletcher, D., Wills, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery:+A+lead+acid+battery+based+on+an+electrolyte+with+soluble+lead+(II)+Part+II.+Flow+cell+studies.">A novel flow battery: A lead acid battery based on an electrolyte with soluble lead (II) Part II. Flow cell studies.</a> Physical Chemistry Chemical Physics. 6 (8), 1779-1785 (2004).</li><li>Pletcher, D., Wills, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery-a+lead+acid+battery+based+on+an+electrolyte+with+soluble+lead+(II).+III.+The+influence+of+conditions+on+battery+performance.">A novel flow battery-a lead acid battery based on an electrolyte with soluble lead (II). III. The influence of conditions on battery performance.</a> Journal of Power Sources. 149, 96-102 (2005).</li><li>Hazza, A., Pletcher, D., Wills, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery-a+lead+acid+battery+based+on+an+electrolyte+with+soluble+lead+(II).+IV.+The+influence+of+additives.">A novel flow battery-a lead acid battery based on an electrolyte with soluble lead (II). IV. The influence of additives.</a> Journal of Power Sources. 149, 103-111 (2005).</li><li>Pletcher, D., Zhou, H., Kear, G., Low, C. T. J., Walsh, F. C., Wills, R. G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery-A+lead-acid+battery+based+on+an+electrolyte+with+soluble+lead+(II).+V.+Studies+of+the+lead+negative+electrode.">A novel flow battery-A lead-acid battery based on an electrolyte with soluble lead (II). V. Studies of the lead negative electrode.</a> Journal of Power Sources. 180 (1), 621-629 (2008).</li><li>Pletcher, D., Zhou, H., Kear, G., Low, C. T. J., Walsh, F. C., Wills, R. G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery-A+lead-acid+battery+based+on+an+electrolyte+with+soluble+lead+(II).+Part+VI.+Studies+of+the+lead+dioxide+positive+electrode.">A novel flow battery-A lead-acid battery based on an electrolyte with soluble lead (II). Part VI. Studies of the lead dioxide positive electrode.</a> Journal of Power Sources. 180 (1), 630-634 (2008).</li><li>Li, X., Pletcher, D., Walsh, F. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery:+a+lead+acid+battery+based+on+an+electrolyte+with+soluble+lead+(II).+Part+VII.+Further+studies+of+the+lead+dioxide+positive+electrode.">A novel flow battery: a lead acid battery based on an electrolyte with soluble lead (II). Part VII. Further studies of the lead dioxide positive electrode.</a> Electrochimica Acta. 54 (20), 4688-4695 (2009).</li><li>Krishna, M., Fraser, E. J., Wills, R. G. A., Walsh, F. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developments+in+soluble+lead+flow+batteries+and+remaining+challenges:+An+illustrated+review.">Developments in soluble lead flow batteries and remaining challenges: An illustrated review.</a> Journal of Energy Storage. 15, 69-90 (2018).</li><li>Lin, Y. -. T., Tan, H. -. L., Lee, C. -. Y., Chen, H. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stabilizing+the+electrodeposit-electrolyte+interphase+in+soluble+lead+flow+batteries+with+ethanoate+additive.">Stabilizing the electrodeposit-electrolyte interphase in soluble lead flow batteries with ethanoate additive.</a> Electrochimica Acta. 263, 60-67 (2018).</li><li>Oury, A., Kirchev, A., Bultel, Y., Chainet, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PbO2/Pb2++cycling+in+methanesulfonic+acid+and+mechanisms+associated+for+soluble+lead-acid+flow+battery+applications.">PbO2/Pb2+ cycling in methanesulfonic acid and mechanisms associated for soluble lead-acid flow battery applications.</a> Electrochimica Acta. 71, 140-149 (2012).</li><li>Oury, A., Kirchev, A., Bultel, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+response+of+lead+dioxide/Lead+(II)+galvanostatic+cycling+in+methanesulfonic+acid:+a+morphologico-kinetics+interpretation.">Potential response of lead dioxide/Lead (II) galvanostatic cycling in methanesulfonic acid: a morphologico-kinetics interpretation.</a> Journal of The Electrochemical Society. 160 (1), A148-A154 (2013).</li></ol>

We have nothing to disclose.

This paper describes an economical method to extend the cycle life of SLFBs: by employing NaOAc agent as an electrolyte additive. A batch of fresh graphite electrodes and nickel plates are preprocessed as aforementioned in Step 1 before long-term cycling experiments. Because inconsistency among commercial carbon electrodes may cause performance deviation of the SLFBs, the physical/chemical pretreatment in Step 1.4 is critical to remove surface residues. The second part of Step 1.4 is employing electrochemical methods to remove impurities that may induce redox reactions between the potentials of 0 to 1.8 V vs. Ag/AgCl. As demonstrated in Figure 3, the cycle life of SLFBs is extended by approximately 50% when the NaOAc additive is supplied in 50 mM to the MSA based electrolyte, under a current density of 15 mA cm-2 and a charge/discharge duration of 40 min.
Since the focus of this study is on the electrolyte additive effects, we employed beaker cells rather than flow cells to minimize uncertainties derived from flow conditions. The beaker cell is magnetically stirred at a rotation rate of ~200 rpm to maintain a certain level of concentration uniformity of the electrolyte without severe agitation. The temperature of beaker cells is not controlled in the experiments, which leaves it close to the atmospheric temperature (25 &#177; 5 &#176;C). While temperature variation, if significant enough, may affect the deposition quality and battery performance, the two compared experiments are conducted in parallel to avoid the temperature perturbation interference. In addition, the long-term charge/discharge cycling of SLFBs can continue for several weeks during which the electrolyte in beaker cells will evaporate unignorably. It is thus also important to conceal the beaker cell to prevent excess evaporation. We find the aforementioned beaker cell experiment useful to simplify the analysis of electrolyte/electrode modification effects in single-flow RFBs.
Since the SLFB is a single-flow energy storage device operates through electroplating/stripping of PbO2 and Pb at the positive and the negative electrode, respectively, during charge/discharge, the quality of electrodeposits is pivotal to the battery efficiency. TI measurement has been historically utilized to investigate the quality of electrodeposit and thus is employed here to assess the additive effect. A pivotal consideration for accurate TI measurement in Step 2 is to choose the appropriate plating duration. Since the weight of electrodeposit is proportional to the amount of charges supplied and the current density is chosen to be representable of the battery operation condition, the plating duration should be chosen to accumulate appropriate amount of electrodeposit for later measurements.
Another prominent phenomenon observed in NaOAc-assisted SLFBs is the significant decrease of PbO2 shedding, which can be visually observed in the beaker cell. This reduced shedding in electrolyte with NaOAc additive is in accordance with the more congregated surface of the PbO2 electrodeposit observed in SEM images shown in Figure 5a. The extended cycle life of SLFBs is thus achieved by the plating of more integrated PbO2 deposits when NaOAc is added adequately to the electrolyte.
In this report, we present findings on a significant extension of SLFB lifespan by the NaOAc additive. Our work marks substantial improvement of SLFB technology and sheds lights on the failure mechanisms of SLFBs. In light of how high-quality electrodeposition can be assisted by NaOAc additive, our work opens up an exciting avenue to the advancement of batteries involving redox reactions associated with electrodeposition during cyclization.

Renewable energy sources including solar and wind have been developed for decades, but their intermittent nature poses great challenges. For a future power grid with renewable energy sources incorporated, grid stabilization and load leveling are critical and can be achieved by integrating energy storage. Redox flow batteries (RFBs) are one of the promising options for grid-scale energy storage. Traditional RFBs contain ion-selective membranes separating anolyte and catholyte; for example, the all-vanadium RFB has shown to operate with high efficiency and a long cycle life1,2. However, their market share as energy storage is very limited in part due to the expensive comprising materials and ineffective ion-selective membranes. On the other hand, a single-flow soluble lead flow battery (SLFB) is presented by Plectcher et al.1,2,3,4,5. The SLFB is membrane-less because it has only one active species, Pb(II) ions. Pb(II) ions are electroplated at the positive electrode as PbO2 and the negative electrode as Pb simultaneously during charging, and convert back to Pb(II) during discharging. A SLFB thus needs one circulation pump and one electrolyte storage tank only, which in turn can potentially lead to reduced capital and operational cost compared to conventional RFBs. The published cycle life of SLFBs, however, is so far limited to less than 200 cycles under normal flow conditions6,7,8,9,10.
Factors leading to a short SLFB cycle life is preliminarily associated with deposition/dissolution of PbO2 at the positive electrode. During charge/discharge processes, the electrolyte acidity is found to increase over deep or repeated cycles11, and protons are suggested to induce the generation of a passivation layer of non-stoichiometric PbOx12,13. The shedding of PbO2 is another phenomenon related to SLFB degradation. Shed PbO2 particles are irreversible and can no longer be utilized. The coulombic efficiency (CE) of SLFBs consequentially declines because of imbalanced electrochemical reactions as well as accumulated electrodeposits at both electrodes. To extend cycle life of SLFBs, stabilizing the pH fluctuation and electrodeposit structure are critical. A recent paper demonstrates an enhanced performance and extended cycle life of SLFBs with addition of sodium acetate (NaOAc) in methanesulfonic electrolyte11.
Here, a detailed protocol for employing NaOAc as an additive to the methanesulfonic electrolyte in SLFBs is described. The SLFB performance is shown to be enhanced and the lifespan can be extended by over 50% in comparison to SLFBs without NaOAc additives. In addition, procedures for throwing index (TI) measurement are illustrated for the purpose of quantitative comparison of additive effects on electrodeposition. Finally, a scanning electron microscopy (SEM) sample preparation method for electrodeposit on SLFB electrodes is described and the additive impact on electrodeposit is manifested in acquired images.

<table>
	<tbody>
		<tr>
			<td>70 mm cellulose filter paper</td>
			<td>Advance</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Autolab</td>
			<td>Metrohm</td>
			<td>PGSTA302N</td>
			<td></td>
		</tr>
		<tr>
			<td>BT-Lab</td>
			<td>BioLogic</td>
			<td>BCS-810</td>
			<td></td>
		</tr>
		<tr>
			<td>commercial carbon composite electrode</td>
			<td>Homy Tech,Taiwan</td>
			<td></td>
			<td>Density 1.75 g cm-3, and electrical conductivity 330 S cm-1</td>
		</tr>
		<tr>
			<td>Diamond saw</td>
			<td>Buehler</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric Acid</td>
			<td>SHOWA</td>
			<td>0812-0150-000-69SW</td>
			<td>35%</td>
		</tr>
		<tr>
			<td>Lead (II) Oxide</td>
			<td>SHOWA</td>
			<td>1209-0250-000-23SW</td>
			<td>98%</td>
		</tr>
		<tr>
			<td>Lutropur MSA</td>
			<td>BASF</td>
			<td>50707525</td>
			<td>70%</td>
		</tr>
		<tr>
			<td>nickel plate</td>
			<td>Lien Hung Alloy Trading Co., LTD., Taiwan,&#160;</td>
			<td></td>
			<td>99%</td>
		</tr>
		<tr>
			<td>Potassium Nitrate</td>
			<td>Scharlab</td>
			<td>28703-95</td>
			<td>99%</td>
		</tr>
		<tr>
			<td>Scanning electron microscopy</td>
			<td>JEOL</td>
			<td>JSM-7800F</td>
			<td>at accelerating voltage of 15 kV</td>
		</tr>
		<tr>
			<td>Sodium Acetate</td>
			<td>SHOWA</td>
			<td>1922-5250-000-23SW</td>
			<td>98%</td>
		</tr>
		<tr>
			<td>water purification system</td>
			<td>Barnstead MicroPure</td>
			<td></td>
			<td>&#160;18.2 M&#937;&#160;&#8226; cm</td>
		</tr>
	</tbody>
</table>

extending the lifespan of soluble lead flow batteries with a sodium acetate additive

In this report, we present a method for the construction of a soluble lead flow battery (SLFB) with an extended cycle life. By supplying an adequate amount of sodium acetate (NaOAc) to the electrolyte, a cycle life extension of over 50% is demonstrated for SLFBs via long-term galvanostatic charge/discharge experiments. A higher quality of the PbO2 electrodeposit at the positive electrode is quantitatively validated for NaOAc-added electrolyte by throwing index (TI) measurements. Images acquired by scanning electron microscopy (SEM) also exhibit more integrated PbO2 surface morphology when the SLFB is operated with the NaOAc-added electrolyte. This work indicates that electrolyte modification can be a plausible route to economically enable SLFBs for large-scale energy storage.

To extend cycle life of SLFBs, NaOAc is supplied as an electrolyte additive. Cycling performance of SLFBs with and without NaOAc additive are examined in parallel, and results are shown in Figure 3. For easier quantitative comparison of cycle life, we define the &#34;death&#34; of a SLFB as when its CE is lower than 80% under continuous galvanostatic charge/discharge. Figure 3a and 3b show that approximately 50% cycle life extension of the SLFB is achieved when 50 mM NaOAc is added to the electrolyte of 0.5 M lead methanesulfonate and 0.5 M MSA, under 40-minute charge/discharge with a current density of 15 mA cm-2. The cycle number we hence accounted for is a representation of the battery life under full depth of discharge. The positive effect of NaOAc additive on SLFB performance is even more pronounced when the depth of charge/discharge is increased, and no additional redox reaction is observed in the SLFB operational potential range11.
Since SLFB is operated through electroplating/dissolution, TI experiments are conducted for the positive and negative electrodes of SLFBs, with and without NaOAc, to gain insight into the additive effect. TI measurements conducted for the positive electrodes employing an electrolyte with NaOAc demonstrate a shallower&#160;slope of the metal distribution ratio (MDR) to linear distance ratio (LR) than the one without additive in Figure 4a. The steeper slope of MDR to LR in TI measurement suggests that the electrodeposition is more affected by non-uniform current distribution, and a high-quality electrodeposit is harder to be plated. On the contrary, TI results for negative electrodes in Figure 4b show similar slopes of MDR to LR for both electrolytes. This result indicates that a better quality of PbO2 deposition is achieved with NaOAc-added electrolyte at the positive electrode, while the Pb plating at the negative electrode is nearly unaffected by NaOAc additive.
In addition, SEM images are acquired for the PbO2 electrodeposits as plated at the positive electrodes of SLFBs after 50-cycle galvanostatic charge/discharge experiments, under 60-minute charge/discharge with a current density of 15 mA cm-2. A smoother surface with less defects of the PbO2 electrodeposit is observed in Figure 5a in an electrolyte with the NaOAc additive, compared to the more fractured PbO2 surface plated without NaOAc as shown in Figure 5b. This morphological observation of PbO2 electrodeposit is in accordance with the TI measurement results, which indicates higher quality of electrodeposition with NaOAc additive.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58484/58484fig1.jpg" /> 
Figure 1. A schematic diagram of the beaker cell employed for SLFB galvanostatic charge/discharge experiment. A home-made electrode positioning board is used to fix the electrode distance (18 mm), and the electrolyte mixing is achieved by controlling the rotation rate of the magnetic stirrer. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58484/58484fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58484/58484fig2.jpg" /> 
Figure 2. A schematic diagram of the Haring-Blum cell employed for TI measurements. In this diagram, the far to near anode distance ratio is set at 6 to 1. The complete set of TI results is acquired by varying the far to near electrode distance ratios with fresh electrodes in each individual measurement. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58484/58484fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58484/58484fig3.jpg" /> 
Figure 3. Galvanostatic charge/discharge cycle efficiencies of SLFBs with electrolyte (a) with; and (b) without 50 mM NaOAc additive; under 40-minute charge/discharge cycling and a current density of 15 mA&#183;cm-2. The cutoff potential is set at 1.05 V and the electrolyte volume is of 260 mL. This figure has been plotted based on data in Ref11 with permission. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58484/58484fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58484/58484fig4.jpg" /> 
Figure 4. A comparison of the metal distribution ratio to linear distance ratio measured by throwing index experiments (a) PbO2 deposition at the positive electrodes; (b) Pb deposition at the negative electrodes. This figure has been modified from Ref11 with permission. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58484/58484fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58484/58484fig5.jpg" /> 
Figure 5. SEM images of electroplated PbO2 at the positive electrode by electrolyte (a) with 50 mM NaOAc additive; (b) without additive. The magnification is of 20,000X. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58484/58484fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive at JoVE.com

Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive

A protocol for the construction of a soluble lead flow battery with an extended lifespan, in which sodium acetate is supplied in the methanesulfonic electrolyte as an additive, is presented.

In this report, we present a method for the construction of a soluble lead flow battery (SLFB) with an extended cycle life. By supplying an adequate ...

extending-lifespan-soluble-lead-flow-batteries-with-sodium-acetate

Nanyang Technological University

Research

JoVE Journal

Chemistry

9.1K Views.  National Taiwan University. A protocol for the construction of a soluble lead flow battery with an extended lifespan, in which sodium acetate is supplied in the methanesulfonic electrolyte as an additive, is presented.

Video: Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive

Exploring the Radical Nature of a Carbon Surface by Electron Paramagnetic Resonance and a Calibrated Gas Flow

While the first Electron Paramagnetic Resonance (EPR) studies regarding the effects of oxidation on the structure and stability of carbon radicals date back to the early 1980s the focus of these early papers primarily characterized the changes to the structures under extremely harsh conditions (pH or temperature)1-3. It is also known that paramagnetic molecular oxygen undergoes a Heisenberg spin exchange interaction with stable radicals that extremely broadens the EPR signal4-6. Recently, we reported interesting results where this interaction of molecular oxygen with a certain part of the existing stable radical structure can be reversibly affected simply by flowing a diamagnetic gas through the carbon samples at STP7. As flows of He, CO2, and N2 had a similar effect these interactions occur at the surface area of the macropore system.
This manuscript highlights the experimental techniques, work-up, and analysis towards affecting the existing stable radical nature in the carbon structures. It is hoped that it will help towards further development and understanding of these interactions in the community at large.

Stable radicals that are present in carbon substrates interact with paramagnetic oxygen through a Heisenberg spin exchange. This interaction can be significantly reduced under STP conditions by flowing a diamagnetic gas over the carbon system. This manuscript describes a simple method to characterize the nature of those radicals.

While the first Electron Paramagnetic Resonance (EPR) studies regarding the effects of oxidation on the structure and stability of carbon radicals date ...

Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible to ensure consistent product quality over time using this technique. We here show how to interface a commercially available flow unit with a Raman spectrometer. The Raman flow cell is placed after the back-pressure regulator, meaning that it can be operated at atmospheric pressure. In addition, the fact that the product stream passes through a length of tubing before entering the flow cell means that the material is at RT. It is important that the spectra are acquired under isothermal conditions since Raman signal intensity is temperature dependent. Having assembled the apparatus, we then show how to monitor a chemical reaction, the piperidine-catalyzed synthesis of 3-acetylcoumarin from salicylaldehyde and ethyl acetoacetate being used as an example. The reaction can be performed over a range of flow rates and temperatures, the in-situ monitoring tool being used to optimize conditions simply and easily.

Real-time monitoring allows for fast optimization of reactions performed using continuous-flow processing. Here the preparation of 3-acetylcoumarin is used as an example. The apparatus for performing in-situ Raman monitoring is described, as are the steps required to optimize the reaction.

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible ...

Water in Oil Emulsions: A New System for Assembling Water-soluble Chlorophyll-binding Proteins with Hydrophobic Pigments

Chlorophylls (Chls) and bacteriochlorophylls (BChls) are the primary cofactors that carry out photosynthetic light harvesting and electron transport. Their functionality critically depends on their specific organization within large and elaborate multisubunit transmembrane protein complexes. In order to understand at the molecular level how these complexes facilitate solar energy conversion, it is essential to understand protein-pigment, and pigment-pigment interactions, and their effect on excited dynamics. One way of gaining such understanding is by constructing and studying complexes of Chls with simple water-soluble recombinant proteins. However, incorporating the lipophilic Chls and BChls into water-soluble proteins is difficult. Moreover, there is no general method, which could be used for assembly of water-soluble proteins with hydrophobic pigments. Here, we demonstrate a simple and high throughput system based on water-in-oil emulsions, which enables assembly of water-soluble proteins with hydrophobic Chls. The new method was validated by assembling recombinant versions of the water-soluble chlorophyll binding protein of Brassicaceae plants (WSCP) with Chl a. We demonstrate the successful assembly of Chl a using crude lysates of WSCP expressing E. coli cell, which may be used for developing a genetic screen system for novel water-soluble Chl-binding proteins, and for studies of Chl-protein interactions and assembly processes.

This manuscript describes a simple and high-throughput method for assembling water-soluble proteins with hydrophobic pigments that is based on water-in-oil emulsions. We demonstrate the effectiveness of the method in the assembly of native chlorophylls with four variants of recombinant water-soluble-chlorophyll binding proteins (WSCPs) of Brassica plants expressed in E. coli.

Chlorophylls (Chls) and bacteriochlorophylls (BChls) are the primary cofactors that carry out photosynthetic light harvesting and electron transport. ...

Visualization of Ambient Mass Spectrometry with the Use of Schlieren Photography

This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass spectrometer, it is necessary to characterize and understand the physical principles of the source. Most commercial ambient ionization sources utilize jets of nitrogen, helium, or atmospheric air to facilitate the ionization of the analyte. As a consequence, schlieren photography can be used to visualize the gas streams by exploiting the differences in refractive index between the streams and ambient air for visualization in real time. The basic setup requires a camera, mirror, flashlight, and razor blade. When properly configured, a real time image of the source is observed by watching its reflection. This allows for insight into the mechanism of action in the source, and pathways to its optimization can be elucidated. Light is shed on an otherwise invisible situation.

This paper presents a protocol for the visualization of gaseous streams of an ambient ionization source using schlieren photography and mass spectrometry.

This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass ...

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and &#946; liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.

A protocol for in situ aqueous synthesis of a bis(iminoguanidinium) ligand and its utilization in selective separation of sulfate is presented.

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, ...

Synthesis of a Water-soluble Metal&#8211;Organic Complex Array

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as Ru(II), Pt(II), and Rh(III). The compound, named as a water-soluble metal-organic complex array (WSMOCA), is obtained through 1) the conventional solution-chemistry-based preparation of the corresponding metal complex monomers having a 9-fluorenylmethyloxycarbonyl (Fmoc)-protected amino acid moiety and 2) their sequential coupling together with other water-soluble organic building units on the surface-functionalized polymeric resin by following the procedures originally developed for the solid-phase synthesis of polypeptides, with proper modifications. Traces of reactions determined by mass spectrometric analysis at the representative coupling steps in stage 2 confirm the selective construction of a predetermined sequence of metal centers along with the peptide backbone. The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.

A potential general method for the synthesis of water-soluble multimetallic peptidic arrays containing a predetermined sequence of metal centers is presented.

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as ...

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Direct cross-coupling between two alkenes via vinylic C-H bond activation represents an efficient strategy for the synthesis of butadienes with high atomic and step economy. However, this functionality-directed cross-coupling reaction has not been developed, as there are still limited directing groups in practical use. In particular, a stoichiometric amount of oxidant is usually required, producing a large amount of waste. Due to our interest in novel 1,3-butadiene synthesis, we describe the ruthenium-catalyzed olefination of electron-deficient alkenes using allyl acetate and without external oxidant. The reaction of 2-phenyl acrylamide and allyl acetate was chosen as a model reaction, and the desired diene product was obtained in 80% isolated yield with good stereoselectivity (Z,E/Z,Z = 88:12) under optimal conditions: [Ru(p-cymene) Cl2]2 (3 mol %) and AgSbF6 (20 mol %) in DCE at 110 &#186;C for 16 h. With the optimized catalytic conditions in hand, representative &#945;- and/or &#946;-substituted acrylamides were investigated, and all reacted smoothly, regardless of aliphatic or aromatic groups. Also, differently N-substituted acrylamides have proven to be good substrates. Moreover, we examined the reactivity of different allyl derivatives, suggesting that the chelation of acetate oxygen to the metal is crucial for the catalytic process. Deuterium-labeled experiments were also conducted to investigate the reaction mechanism. Only Z-selective H/D exchanges on acrylamide were observed, indicating a reversible cyclometalation event. In addition, a kinetic isotope effect (KIE) of 3.2 was observed in the intermolecular isotopic study, suggesting that the olefinic C-H metalation step is probably involved in the rate-determining step.

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

The ruthenium-catalyzed olefination of electron-deficient alkenes with allyl acetate is described here. By using aminocarbonyl as a directing group, this external oxidant-free protocol has high efficiency and good stereo- and regioselectivity, opening a novel synthetic route to (Z,E)-butadiene skeletons.

Direct cross-coupling between two alkenes via vinylic C-H bond activation represents an efficient strategy for the synthesis of butadienes with high ...

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Continuous flow technology has been identified as instrumental for its environmental and economic advantages leveraging superior mixing, heat transfer and cost savings through the &#34;scaling out&#34; strategy as opposed to the traditional &#34;scaling up&#34;. Herein, we report the reaction of diphenyldiazomethane with p-nitrobenzoic acid in both batch and flow modes. To effectively transfer the reaction from batch to flow mode, it is essential to first conduct the reaction in batch. As a consequence, the reaction of diphenyldiazomethane was first studied in batch as a function of temperature, reaction time, and concentration to obtain kinetic information and process parameters. The glass flow reactor set-up is described and combines two types of reaction modules with &#34;mixing&#34; and &#34;linear&#34; microstructures. Finally, the reaction of diphenyldiazomethane with p-nitrobenzoic acid was successfully conducted in the flow reactor, with up to 95% conversion of the diphenyldiazomethane in 11 min. This proof of concept reaction aims to provide insight for scientists to consider flow technology&#39;s competitiveness, sustainability, and versatility in their research.

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Flow chemistry carries environmental and economic advantages by leveraging superior mixing, heat transfer and cost benefits. Herein, we provide a blueprint to transfer chemical processes from batch to flow mode. The reaction of diphenyldiazomethane (DDM) with p-nitrobenzoic acid, conducted in batch and flow, was chosen for proof of concept.

Continuous flow technology has been identified as instrumental for its environmental and economic advantages leveraging superior mixing, heat transfer and ...

Synthesizing Sodium Tungstate and Sodium Molybdate Microcapsules via Bacterial Mineral Excretion

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the two metal oxides&#39; corresponding nanoparticles&#8212;the former being as small as 22 nm and the latter 15 nm. We fed two strains of bacteria, Shewanella algae and Pandoraea sp., with various concentrations of tungstate or molybdate ions. The concentrations of tungstate and molybdate were adjusted to make microcapsules of different length-to-diameter ratios. We found that the higher the concentration the smaller the nanoparticles were. The nanoparticles came in with three length-to-diameter ratios: 10:1, 3:1 and 1:1, which were achieved by feeding the bacteria respectively with a low concentration, a medium concentration, and a high concentration. The images of the hollow microcapsules were taken via the scanning electron microsphere (SEM). Their crystal structures were verified by X-ray diffraction (XRD)&#8212;the crystal structure of molybdate microcapsules is Na2MoO4 and that of tungstate microcapsules is Na2WO4 with Na2W2O7. These syntheses all were accomplished under a near ambient condition.

This work presents a protocol for manufacture sodium tungstate and sodium molybdate microcapsules via bacteria and their corresponding nanoparticles.

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the ...

Elemental-sensitive Detection of the Chemistry in Batteries through Soft X-ray Absorption Spectroscopy and Resonant Inelastic X-ray Scattering

Energy storage has become more and more a limiting factor of today's sustainable energy applications, including electric vehicles and green electric grid based on volatile solar and wind sources. The pressing demand of developing high-performance electrochemical energy storage solutions, i.e., batteries, relies on both fundamental understanding and practical developments from both the academy and industry. The formidable challenge of developing successful battery technology stems from the different requirements for different energy-storage applications. Energy density, power, stability, safety, and cost parameters all have to be balanced in batteries to meet the requirements of different applications. Therefore, multiple battery technologies based on different materials and mechanisms need to be developed and optimized. Incisive tools that could directly probe the chemical reactions in various battery materials are becoming critical to advance the field beyond its conventional trial-and-error approach. Here, we present detailed protocols for soft X-ray absorption spectroscopy (sXAS), soft X-ray emission spectroscopy (sXES), and resonant inelastic X-ray scattering (RIXS) experiments, which are inherently elemental-sensitive probes of the transition-metal 3d and anion 2p states in battery compounds. We provide the details on the experimental techniques and demonstrations revealing the key chemical states in battery materials through these soft X-ray spectroscopy techniques.

Here, we present a protocol for typical experiments of soft X-ray absorption spectroscopy (sXAS) and resonant inelastic X-ray scattering (RIXS) with applications in battery material studies.

Energy storage has become more and more a limiting factor of today's sustainable energy applications, including electric vehicles and green electric grid ...

Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive

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Exploring the Radical Nature of a Carbon Surface by Electron Paramagnetic Resonance and a Calibrated Gas Flow

Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example

Water in Oil Emulsions: A New System for Assembling Water-soluble Chlorophyll-binding Proteins with Hydrophobic Pigments

Visualization of Ambient Mass Spectrometry with the Use of Schlieren Photography

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

Synthesis of a Water-soluble Metal–Organic Complex Array

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Synthesizing Sodium Tungstate and Sodium Molybdate Microcapsules via Bacterial Mineral Excretion

Elemental-sensitive Detection of the Chemistry in Batteries through Soft X-ray Absorption Spectroscopy and Resonant Inelastic X-ray Scattering