Originally this was planned as a 5 task, 3 year project, starting in May 2019. Task 1 Detecting oxidants and metal corrosion in molten chloride salt at 800°C. Task 2 Effectiveness of Zr getter using head gas sensors of inlet and outlet gases. Task 3 Cathodic protection of metal in molten salt at reducing potential. Task 4 Find reduction potential of metals in molten chloride salts & quantum modeling. Task 5 Develop corrosion test sections integrated into molten salt flow loop. After Q4, the project was scaled back and the reorganized SOPO was reduced to 3 tasks to be completed at the end of Q7 on 01/05/2021. The 3 SOPO tasks are: Task 1 Sense oxidants and the metal corrosion in molten Na-K-Mg-Cl salt at 800°C. Task 3 Cathodically protect H230 alloy in molten Na-K-Mg-Cl salt at 800C by making H230 alloy the cathode of a power supply with a chromium-rich-metal as the anode. Task 4 Find the reduction potential of Cr metal in molten Na-K-Mg-Cl salt at 800°C. The total timeline was reduced from 12 to 7 quarters with the end date being, January 5, 2021. This amounted to task 1,3 and 4 being done in Q5,6 and 7 of an extended year 1, ending on January 5, 2021. Task 1, 3 and 4 were completed. For task1) the increase of oxidants in molten salt is detected by two things: i) a positive shift of the electrode potential for a Haynes 230 alloy (H230) metal coupon versus a silver/silver-chloride reference electrode (SSE) and ii) an increase in the corrosion rate of a H230 electrode at 800C. For task 3) applying a cathodic potential (negative overpotential) to a H230 electrode versus SSE arrested the corrosion of the cathodically protected H230 compared to an unprotected “spectator H230 electrode” in the same molten chloride salt. Lastly, for task 4) the reduction potential of chrome and chrome rich, and nickel metal electrodes were measured. The most valuable outcome of this work is that a power supply can arrest metal corrosion for metal in molten chloride salt when the power supply applies a cathodic potential to bare metal, like H230, in molten chloride salts, like ternary Mg-K-Na-chloride salt. H230 is a high strength metal for containing molten chloride salt and ternary Mg-K-Na-chloride salt is used as heat transfer fluids in concentrating solar power plants. When to use cathodic protection for protecting metal in molten chloride salts? Two scenarios are envisioned: 1) for protecting high-valued components, like solar collectors and heat exchangers and 2) for protecting the bare surface in holidays (point defects) of corrosion inhibitors that are to intended to cover the entire surface of metal.

The useful lifetime of bipolar ion exchange membranes is often limited by nucleophilic attack by hydroxide ions on the ionic groups and polymer backbone in the anion exchange layers (AELs). This is especially problematic in water treatment applications for making acid and base from salt solutions. This research investigated the effect of bulk electrolyte composition, current density, membrane thickness, ion exchange capacity, and bulk solution pH value on hydroxide ion concentrations inside the AELs of a bipolar membrane. Onedimensional Nernst-Plank equations were solved for the species Na+, Cl-, OH- and H+ within 20-100 μm thick anion and cation exchange layers with fixed charged densities ranging from 0.5-2.0 eq/L. In 1 M NaCl solutions at neutral pH values, hydroxide concentrations in the AEL reached as high as 2.2 M at a current density of 100 mA/cm2. In 1 M NaOH solutions, hydroxide ion concentrations reached as high as 3.77 M. Hydroxide concentrations in the AEL were significantly affected by the ratio of Cl- to hydroxide ions in the bulk electrolyte. Where hydroxide concentrations in the bulk electrolyte were an order of magnitude lower than chloride concentrations, membrane hydroxide concentrations were nearly proportional to the current density. Increases in ion exchange capacity and AEL thickness resulted in increased membrane hydroxide ion concentrations. Membrane concentrations of hydroxide ions can be minimized by operation at low current densities, with high background electrolyte concentrations using thin membranes with low ion exchange capacities and producing base concentrations less than 0.1 M.

The construction of optimized biological fuel cells requires a cathode which combines the longevity of a microbial catalyst with the current density of an enzymatic catalyst. Laccase-secreting fungi were grown directly on the cathode of a biological fuel cell to facilitate the exchange of inactive enzymes with active enzymes, with the goal of extending the lifetime of laccase cathodes. Directly incorporating the laccase-producing fungus at the cathode extends the operational lifetime of laccase cathodes while eliminating the need for frequent replenishment of the electrolyte. The hybrid microbial–enzymatic cathode addresses the issue of enzyme inactivation by using the natural ability of fungi to exchange inactive laccases at the cathode with active laccases. Finally, enzyme adsorption was increased through the use of a functionally graded coating containing an optimized ratio of titanium dioxide nanoparticles and single-walled carbon nanotubes. The hybrid microbial–enzymatic fuel cell combines the higher current density of enzymatic fuel cells with the longevity of microbial fuel cells, and demonstrates the feasibility of a self-regenerating fuel cell in which inactive laccases are continuously exchanged with active laccases.

Eutectic molten chloride salts by MgCl2, ZnCl2, KCl, and NaCl are considered as promising high temperature heat transfer and thermal storage fluid in concentrated solar power (CSP) systems. However, chloride salts MgCl2 and ZnCl2 are water affinity, so they can absorb water from surroundings easily. This will increase the corrosion of metals when the molten salts stay with metals at high temperatures. Our study also found that the presence of trace water in the solid salt caused vapor pressure of the molten salts increase. The current work presents studies about the kinetic processes of water absorption and removal from single and different mixture of NaCl, KCl, MgCl2 and ZnCl2 salts. The process of water uptake from ambient air and removal through heating are measured quantitatively. Water removal from molten salts through sparging with argon gas was employed as a further treatment method.

The eutectic mixture of MgCl2–KCl molten salt is a high temperature heat transfer and thermal storage fluid able to be used at temperatures up to 800 °C in concentrating solar thermal power systems. The molten salt thermophysical properties are reported including vapor pressure, heat capacity, density, viscosity, thermal conductivity, and the corrosion behavior of nickel-based alloys in the molten salt corrosion at high temperatures. Correlations of the measured properties as functions of molten salt temperatures are presented for industrial applications. The test results of tensile strength of two nickel-based alloys exposed in the molten salt at a temperature of 800 °C from 1-week length to 16-week length are reported. It was found that the corrosion and strength loss is rather low when the salt is first processed to remove water and oxygen.

The reduction of total Pt-loading in a cathode catalyst without sacrificing performance is one of the key objectives for the large-scale commercialization of proton exchange membrane fuel cell (PEMFC) technology. A core-shell type nanostructured catalyst with a Pt-loading 20 times lower than a commercial catalyst is demonstrated herein to be more active for the electrocatalysis of the oxygen reduction reaction (ORR) in acid electrolyte. The weight ratio of metal nanoparticles on carbon support is the key to achieving the highest ORR activity in a series of silver-based catalysts, all with 10 mol percent of Pt and 10 mol percent of Pd over 80 mol percent of silver (Ag) and supported on untreated Vulcan carbon to form an electrocatalyst (Ag@Pt10Pd10/C) with either 5, 10, 20 or 30 wt% of total metals on carbon; which correspond to a Pt concentration around 1, 2, 3 and 5 wt%, respectively. All metal nanostructures on carbon show a similar morphology, size and structure. Thin films of these four Ag@Pt10Pd10/C catalysts on rotating disk electrodes (TF-RDEs) all shown a 4-electrons pathway for the ORR and give higher exchange current densities (j(o) > 3.8 mA/cm(2)) than a commercial Etek Pt-20/C catalyst (j(o) = 2.4 mA/cm(2)). The Ag@Pt10Pd10/C catalyst with 5 wt% of total metals (1 wt% of Pt) on carbon gives the best electrocatalysis; reducing molecular oxygen to water two times faster and generating 25% higher current per milligram of platinum (mass activity) than the commercial catalyst (Pt-20/C). Therefore, the Ag@Pt10Pd10/C catalyst with 5 wt% of total metals is a new catalyst for ORR for a PEMFC with a lower Pt loading and cost. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Eutectic molten salt MgCl2-KClis was considered as a high temperature heat transfer and thermal storage fluid, being able to work at temperatures up to 800 °C for concentrating solar thermal power. Thermophysical properties including vapor pressure, heat capacity, density, viscosity, and thermal conductivity, and the behavior of the corrosion of high temperature nickel-based alloys in the eutectic salt are investigated and reported in this work. Corrosion studies were carried out and measured at a temperature up to 800 °C over a time span of one week to one month. Low corrosion rate was observed for two types of high temperature nickel-based alloys under the environment that the salt is strictly processed to have a very low level of water and oxygen.

Hematin-induced fluorescence quenching of boron-doped graphene quantum dots (BGQDs) allows for determination of hematin concentration in human erythrocytes with no need for separating hematin from hemoglobin before performing the assay. The BGQDs are made by oxidizing a graphite anode by holding the voltage between a graphite rod and a Pt cathode at 3 V for 2 h in an aqueous borax solution at pH 7; then, the borate solution was filtered with BGQDs, and the borate was dialyzed from the filtrate, leaving a solution of BGQDs in water. The fluorescence intensity of BGQDs is measurable in real time, and its quenching is very sensitive to the concentration of hematin in the system but not to other coexisting biological substances. The analytical signal is defined as ΔF = 1 - F/F0, where F0 and F are the fluorescence intensities of the BGQDs before and after interaction with hematin, respectively. There is a good linear relationship between ΔF and hematin concentration, ranging from 0.01 to 0.92 μM, with the limit of detection (LOD) being ∼0.005 ± 0.001 μM at a signal-to-noise ratio of 3. This new method is sensitive, label-free, simple, and inexpensive, and many tedious procedures related to sample separation and preparation can be omitted, implying that this method has potential for applications in clinical examinations and disease diagnoses. For example, the determination of the hematin levels in two kind of red blood cell samples, healthy human and sickle cell erythrocytes, gives average concentrations of hematin of ∼(23.1 ± 4.9) μM (average of five samples) for healthy red cell cytosols and ∼(52.5 ± 9.5) μM (average of two samples) for sickle red cell cytosols.

Much work has been devoted to synthesizing the non-noble metal catalyst such as nitrogen-doped carbon supported transition metal catalysts (denoted as metal-N-C catalyst) for the oxygen reduction reaction (ORR). However, the catalytic mechanisms and precise chemical nature of the active sites in this kind of catalyst are still controversial, which hinders the development and commercialization of this novel ORR catalyst. The objective of this work is to study the nature of active sites for ORR in the Fe-N-C catalysts. We synthesized a new family of nitrogen-doped carbon with iron catalysts (denoted as Fe-N-C catalysts) by pyrolyzing the mixtures with various ratios of a nitrogen-atom rich heterocycle compound, 1-ethyl-3-methylimidazolium dicyanamide (EMIM-dca), and iron chloride (FeCl3). The ORR activity (J(K) at 0.8 V vs RHE, in 0.1 M KOH solution) of a typical catalyst, Fe-15-N-C1000, in this family is 6.65 mA/mg, which is much higher than the values of the Fe-C (0.48 mA/mg) and N-C catalysts (0.25 mA/mg). The relationship between the ORR activity and the structures (the possible active sites in particular) of the catalysts was studied under different conditions. The active site in the catalyst is found to be the Fe-N species (most likely in the form of Fe3N). Metallic iron (Fe) particles, Fe3C species, and N-C species are not catalytically active sites, nor do these moieties interact with the Fe-N active sites during the catalysis of the ORB. High pyrolysis temperatures and increasing the Fe content during the synthesis favor the formation of the Fe-N active sites in the final catalyst. Our study opens up new synthetic control of parameters affecting the final structure and catalyst performance and allows modifying the unexplored avenues toward new multiply heteroatom doped nonprecious ORR catalysts.

A heat transfer fluid (HTF) is a major component in the system for concentrating solar power systems (CSP) to make electricity. The HTF carries thermal energy from the solar concentrator to a steam generator. Currently hydrocarbon oils or alkali-nitrate-based eutectic molten-salt mixtures are used as the HTF in CSP systems, but these materials have limited operating temperature range, which limits efficiency. Hydrocarbons are limited to 250 degrees C and alkali-nitrate salts are stable only below 600 degrees C. Using abundant inexpensive materials to make an HTF which is stable to 1,300 degrees C and compatible with a metal housing, like a Hastelloy nickel alloy, is desired. Design rules are given which tell how the desired goals can be met, which leads to mixing abundant ionic chloride salts, like NaCl and KCl, which boil at temperatures higher than 1,400 degrees C, with low-melting (similar to 200 degrees C) covalent metal halides, such as AlCl3 or ZnCl2, to give low-melting (m.p.< 250 degrees C) eutectic mixtures, which are stable at high temperatures. To have negligible corrosion of the metals which house the eutectic, the component eutectic should have more negative reduction potentials than metals in the salt housing. Accordingly, the ternary K-Na-Zn chloride molten-salt mixtures in the alloy metal housing should be stable. However, corrosion of the metal housing is seen, especially at higher temperatures. The corrosion rates of housing alloys in molten salt in the presence of or excluding air have been experimentally determined at different temperatures. Indications are that the corrosion of the metal is not due to the salt itself but dissolved impurities like water and oxygen.

Higher operating temperatures increase efficiency of the concentrating solar power plants but promote faster corrosion of the pipes and vessels made of Hastelloy or stainless steel materials for the molten-salt mixtures. Hastelloys C-276 and C-22 and stainless steel 304 coupons evaluated in the present study in a eutectic molten salt consisting of 13.4 mol% NaCl, 33.7 mol% KCl and 52.9 mol% ZnCl2 showed substantially lower corrosion rates in the absence versus presence of air from 200 to 800 degrees C as determined by electrochemical and gravimetric methods. In the presence of air, the corrosion rate for the Hastelloy C-276 in the molten salt was found to diminish with immersion time and converges around similar to 50 mu m per year after 4 weeks of immersion at 500 degrees C, which is close to the value similar to 40 mu m per year obtained using the electrochemical method at 500 degrees C. For anaerobic corrosion rate estimation, the corrosivity of an alloy sample was examined by immersing in molten salt inside a sealed quartz container without any contact with air, which is possible because the vapor pressure of the eutectic molten salt is only about 0.7 atm at 800 degrees C. The corrosion rate of the Hastelloy C-276 was only 10 mu m per year in the molten salt in the absence of air at 800 degrees C, which is extremely low compared to 500 mu m per year in conducting corrosion studies in the presence of air at 800 degrees C. The Hastelloy coupons after immersion testing in the absence of air have then been examined also by SEM, and the images did not show any significant changes in the surface. This behavior indicates that, from a corrosion standpoint, the eutectic molten salt in the absence of air is suitable as a heat transfer fluid in Hastelloy C-276 pipes and containers up to 800 degrees C. (C) 2015 Elsevier Ltd. All rights reserved.

Introduction When one mole of tetrahedral zinc dichloride (ZnCl2) and cubic potassium chloride or sodium chloride, a thermally stable complex forms. The corrosion of metal in molten salt, its physical stability and heat transfer properties are needed to determine if metal can house these salts used as heat transfer fluid (HTF) for concentrating solar power (CSP) to generate electricity. Preliminary results show that some ternary mixtures, like NaCl-KCl-ZnCl2 in molar fractions of 13.4%-33.7%-52.9% melt near 200oC and have very low vapor pressures (~ 7psig) at 800oC and has satisfactory thermal and transport properties for collecting solar energy up to 800oC [1]. High corrosion rates of metals in this molten salt are found for aerated salt, but metal corrosion rates are low when the salt is anhydrous and deoxygenated. Electrochemical testing with atmosphere control in cell A working and a counter electrode of C-276 Hastelloy and a silver/silver chloride reference electrode (0.2 V vs NHE) are housed in a quartz electrochemical cell isothermally heated in a furnace. The C-276 Hastelloy is polished with 600 grit SiC paper, rinsed with DI water and acetone. Linear polarization [2] was used to electrochemically characterize the rate of metal oxidation by scanning the working electrode from -30 mV vs. OCP to +30 mV vs. OCP at a scan rate of 0.2 mV/s. The atmosphere of salt in the cell is controlled by heating to 300°C to melt the salt; sparging salt for about 30min with Argon flowing at 150 sccm. The metal sample is inserted into salt and gas passed over salt during the polarization study. Gas is bubbled into the salt when heating to a new temperature, then over salt during polarization at the new temperature. For Fig. 1, the Hastelloy C276 metal area is 5.15cm2 in 150 grams of KCl-NaCl-ZnCl2 salt. Figure 1 Table 1 Gravimetric determination of metal weight loss in anaerobic molten salt Acell with two caps is used to gravimetrically determine corrosion rates. One cap has a long tube to bubble gas into the salt; the other has a short tube to keep gas over the salt. This decreases the salt lost while flowing Argon to maintain the anaerobic condition. For example, the initial weight of metal in one experiment was 10.5830 gm (58 cm2); the mass of salt 300 gm; the salt temperature 800oC, and immersion time 50 hours (2.08 days). The salt was heated at 250°C for 1 hour, then 30 minutes at 350°C without flowing Argon; heated at 500°C for 1h with Argon flowing at 175 sccm without metal in the salt toremove water and oxygen. Argon gas is admitted from a side tube at about 450 sccm to prevent air entering cell as the metal coupon is added and the cap switched from the long tube to short tube. The Argon was kept flowing through the cell cap at 175 sccm and the side tube at 450 sccm. The temperature was 800°C for 50 hours. The metal sample was removed from the cell at 300°C by pouring all contents into a quartz beaker. The metal was sonicated in DI water, then in dilute HCl, then in DI water, 15min each at RT. The sample was re-weighed. The corrosion rate, CR, was 53.34 mpy. This test was repeated with a metal coupon, 5.205 cm2 in area with all other conditions constant. The corrosion rate was 30.29 mpy at 800oC. Conclusion The anaerobic immersion experiments give low corrosion rates because water and oxygen are removed from the salt. The comparison between the small and large coupons indicates sample size does not limit corrosion. The CR from the gravimetric method is consistent with that from the electrochemical method. The C276 metal in the selected salt appears intrinsically stable at elevated temperatures in absence water and oxygen. Acknowledgement The authors gratefully acknowledge the US Dept of Energy for support of this work under Sunshot MURI Program grant number DE-EE0005942. DOE Technical Manager, Levi Irwin. References Halide and Oxy-halide Eutectic Systems for High Performance High Temperature Heat Transfer Fluids, DoE MURI DE-EE0005942, Principal Investigator, Peiwen Li (2014). M. STERN AND A. L. GEARY, “Electrochemical Polarization, I. A Theoretical Analysis of the Shape of Polarization Curves”, JOURNAL OF THE ELECTROCHEMICAL SOCIETY Vol. 104, pp. 56 -63 (1957). Figure 1

Polymer membranes are prepared as a composite of polybenzimidazole and non-functionalized multi-wall carbon nanotubes (PBI-CNT) and polybenzimidazole (PBI) only. Each is doped with H3PO4 (PA) and used as a proton exchange membrane (PEM) as the electrolyte in a fuel cell. The proton conductivities at 180 degrees C for the doped PBI membrane (PBIPA) and the doped PBI-CNT membrane (PBICNTPA) are 6.3 x 10(-2) and 7.4 x 10(-2) Scm(-1) respectively. A single fuel cell having these membranes as electrolyte has a Pt catalyzed hydrogen gas fed anode and a similar oxygen cathode without humidification of feed gases; the cell with the PBICN'TPA membrane has higher open circuit voltage (0.96 V) than that with a PBIPA membrane (0.8 V) at 180 degrees C. The mechanical stability of the membrane improves with CNTs addition. The tensile strength of the composite PBI-CNT membrane with 1 wt.% CNTs loading is 32% higher and the Young's Modulus is 147% higher than the values for a membrane of PBI alone. The improvement in conductivity and mechanical properties in the composite membrane due to the CNT addition indicates that a PBI-CNT membrane is a good alternative as a membrane electrolyte in a PEMFC. (C) 2015 Elsevier B.V. All rights reserved.

Nitrogen-doped graphene quantum dots (N-GQDs) are synthesized at low temperature as a new catalyst allowing electrochemical detection of 2,4,6-trinitrotoluene (TNT). N-GQDs are made by an oxidative ultrasonication of graphene oxide (GO) forming nanometer-sized species, which are then chemically reduced and nitrogen doped by reacting with hydrazine. The as-synthesized N-GQDs have an average diameter of ∼2.5 nm with an N/C atomic ratio of up to ∼6.4%. To detect TNT, TNT is first accumulated on N-GQDs modified glassy carbon (N-GQDs/GC) electrode by holding the electrode at a 0 V versus Ag/AgCl for 150 s in an aqueous TNT solution. Next, the N-GQDs/GC electrode with accumulated TNT is transferred to a fresh PBS solution (0.1 M, pH 7.0, without TNT), where the TNT reduction current at -0.36 V versus Ag/AgCl in a linear scan voltammogram (LSV) shows a linear response to TNT concentration in the aqueous solution from 1 to 400 ppb, with a correlation coefficient of 0.999, a detection limit of 0.2 ppb at a signal/noise (S/N) of 3, and a detection sensitivity of 363 ± 7 mA mM(-1) cm(-2). The detection limit of 0.2 ppb of TNT for this new method is much lower than 2 ppb set by the U.S. Environmental Protection Agency for drinking water. Therefore, N-GQDs allow an electrochemical method for assaying TNT in drinking water to determine if levels of TNT are safe or not.

Cost analyses developed for fuel cells are reviewed, focusing mainly on polymer electrolyte membrane fuel cell (PEMFC) technology, because the solid polymer membrane electrolyte is robust and operates under conditions needed for most pressing applications, especially for the automotive application. Presently, PEMFC cost is still too high for large scale commercialization. The cost of electrodes and membranes contributes substantially to the total PEMFC cost which is driving research to reduce the costs of these components so the PEMFC can be introduced into large scale power markets. A scenario analysis for PEMFC costs for an automotive application illustrates that reducing the MEA cost up to 27% makes achievable the $40/kW cost target by 2020, which corresponds to a reduction in the cost of the catalyst by $3.55/kW and the membrane by $0.8/kW. The ultimate cost target for the PEMFC of 30/kW is obtained when the MEA cost is reduced by 45%, which corresponds to a projected cost reduction for catalyst cost by $6.41/kW and membrane by $1.44/kW. If these costs are met, the PEMFC would reach a price which is cost competitive to Internal Combustion Engine Vehicles which would allow the use of PEMFCs for power generation in a significant number of sectors.

A new oxygen reduction catalyst is made of Pd and Pt nanostructures (Pd–Pt) supported on a herring-bone arrangement of carbon nanofibers (NFs) and is synthesized in one pot by the sequential reduction of Pd2+and Pt4+in aqueous chloride solution with ethylene glycol and then adding the carbon NF to precipitate the catalyst.

In the first part of this work, the feasibility of developing a catalyst with high activity for the oxygen electroreduction reaction (ORR) in acid media and with low Pt loading was demonstrated by over coating a silver (Ag) nanoparticle with a shell of platinum (Pt) and palladium (Pd) En The results show that best activity is not directly related to a higher PtPd loading on the surface of the Ag. The best catalyst in a series of this type of catalyst is found with Ag@Pt0.3Pd0.3/C which gives a specific activity for oxygen reduction, j(k) (in units of mA cm(-2) of real area), of 0.07 mA cm(-2) at 0.85 V vs. NHE, as compared to 0.04 mA cm(-2) when with a commercial Pt on carbon catalyst (Pt-20/C) is used in an identical electrode except for the catalyst. The mass activity, j(m) (in units of mA mu g(-1) of Pt), for Ag@Pt0.3Pd0.3/C is 0.04 mA mu g(-1) of Pt at 0.85 V vs. NHE, whereas that for the Pt-20/C gives 0.02 mA mu g(-1) of Pt, showing Ag@Pt0.3Pd0.3/C is a lower-cost catalyst, because using a Ag core and Pd with Pt in the shell gives the highest catalytic activity using less Pt. (C) 2014 Elsevier B.V. All rights reserved.

Corrosion rates have been estimated for commercial Hastelloys C-276, C-22 and N types in eutectic molten salts containing NaCl, KCl and ZnCl2 using steady-state potentiodynamic method (0.2mVs−1 within ∼±30mV from the open circuit voltage). Hastelloy C-276 exhibited the lowest corrosion rates of ∼10 and 40μm per year in 13.4NaCl–33.7KCl–52.9ZnCl2 (mol%) salt at 250 and 500°C, respectively. The potentiodynamic method was validated by conducting traditional immersion test for corrosion rate estimation on C-276 Hastelloy in 13.4NaCl–33.7KCl–52.9ZnCl2 (mol%) at 500°C (corrosion rate ∼50μm per year). Among the samples evaluated, Hastelloy N showed highest corrosion rate of >150μm per year at 500°C.