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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Protonic Ceramic Electrochemical Cells for Synthesizing Sustainable Chemicals and Fuels

Abstract Protonic ceramic electrochemical cells (PCECs) have been intensively studied as the technology that can be employed for power generation, energy storage, and sustainable chemical synthesis. Recently, there have been substantial advances in electrolyte and electrode materials for improving the performance of protonic ceramic fuel cells and protonic ceramic electrolyzers. However, the electrocatalytic materials development for synthesizing chemicals in PCECs has gained less attention, and there is a lack of systematic and fundamental understanding of the PCEC reactor design, reaction mechanisms, and electrode materials. This review comprehensively summarizes and critically evaluates the most up‐to‐date progress in employing PCECs to synthesize a wide range of chemicals, including ammonia, carbon monoxide, methane, light olefins, and aromatics. Factors that impact the conversion, selectivity, product yield, and energy efficiencies are discussed to provide new insights into designing electrochemical cells, developing electrode materials, and achieving economically viable chemical synthesis. The primary challenges associated with producing chemicals in PCECs are highlighted. Approaches to tackle these challenges are then offered, with a particular focus on deliberately designing electrode materials, aiming to achieve practically valuable product yield and energy efficiency. Finally, perspectives on the future development of PCECs for synthesizing sustainable chemicals are provided.

03 NATURAL GAS↗
NASA NTRS1979

Novel duplex vapor-electrochemical method for silicon solar cells

Optimization studies were carried out for the SiF4-Na reaction with solid Na feed. The goals of the study were the consistent production of high purity reaction products and the gathering of relevant information needed to scale-up the reactor. Parameters studied include: (1) effect of surface to volume ratio of Na slices on the extent of reaction; (2) effect of Na surface oxidation on the extent of reaction; (3) effect of external heating on the extent of SiF4-Na reaction; (4) effect of Na slice addition rate on extent of the reaction; and (5) SiF4-Na reaction - high pressure experiments. An investigation was also made of the possible role played by NaF as a fluxing agent during the separation of silicon by melting of the reaction product (Si + NaF) mixture. Since silicon can be produced by the thermite reaction between Na2SiF6 and Na, studies were initiated to gather information on parameters which control the efficiency of the thermite reaction.

Nanis, L.↗
DOE OSTI2020

LiNi x Fe y Al z O 2 , a new cobalt-free layered cathode material for advanced Li-ion batteries

Recently, rapid fluctuations in cobalt prices have created a worsening supply chain constraint that has become a serious cause of concern amidst global battery manufacturers. To address this challenge, we report herein a new class of cobalt-free, nickel-rich layered cathode material termed the NFA class with general formula LiNi x Fe y Al z O 2 (x + y + z = 1). Using co-precipitation reaction in a continuous stirred tank reactor, we synthesized NFA(OH) 2 precursors with the constituent Ni, Fe and Al elements successfully incorporated. The obtained LiNFAO 2 cathode was characterized using X-Ray diffraction, Mössbauer spectroscopy and scanning electron microscopy. Electrochemical behavior was assessed using cyclic voltammetry, galvanostatic charge/discharge, electrochemical impedance spectroscopy and galvanostatic intermittent titration technique at various states of lithiation/delithiation. Electrochemical performance evaluations revealed that our cobalt-free material delivers high capacity of 190 mAh/g at 0.1C. Rate and cycling performance evaluations also indicated good rate capability and cycling stability with 88% capacity retention after 100 cycles at C/3. Using NFA cathodes, we also fabricated a 0.5Ah (C/3) cobalt-free Li-ion battery which demonstrated reasonable cycling stability with ~72% capacity retained after 200 cycles. Overall, our work demonstrates the immense potential of the cobalt-free NFA class cathodes as viable candidates towards development of next generation cost effective lithium ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

Nuclear waste reduction: Exploring new pathways one step at a time

In my home country of Venezuela, nuclear energy is not a topic that attracts much attention. The government briefly oversaw some nuclear energy programs during the 1950s, but currently there are no active nuclear power facilities in the country. In fact, the Venezuelan government signed and ratified the treaty of the prohibition of nuclear weapons in 2021, which states that Venezuela has never owned, possessed or controlled nuclear weapons or programs of any kind. When I moved to the United States, however, nuclear energy became an extremely relevant topic. In the 1940s, the U.S. government established and oversaw the Manhattan Project to build atomic bombs for use in World War II. After the war, the government encouraged scientists to use this information on nuclear reactions to develop nuclear energy for peaceful civilian purposes instead.1 During these early days of nuclear research, there were no formal regulatory standards for nuclear waste management. Policies usually were self-regulated and often created based on existing policies of disposal for non-nuclear waste.2 As a result, there were instances of nuclear waste leaching into the environment and affecting local communities. So, much research has been conducted since then to characterize and store nuclear waste safely and securely.3 I first became interested in nuclear energy during my undergraduate studies when I worked on a project involving ligand synthesis to help extract actinides from nuclear waste. I then studied electrochemistry in molten salt systems for nuclear energy applications during my Ph.D. As I approached graduation, I started looking into national laboratories that have programs involving nuclear energy and waste management. At Idaho National Laboratory (INL), the focus is more on applied processes and how nuclear energy can be innovated to realize next-generation reactor design and technologies. This focus led me to apply for a Seaborg distinguished postdoctoral position at INL, for which I was chosen based on my proposal of a way to improve nuclear waste recycling. To understand my proposal, we must familiarize ourselves with the makeup of nuclear waste. After uranium dioxide is used as nuclear fuel in a reactor, the fuel matrix is then characterized by various fission products, including rare earth elements, alkali and alkaline earths, and actinides. Some of these fission products can potentially be recovered through pyroprocessing, 4 which involves the electrochemical dissolution of the used nuclear fuel in a molten chloride salt mixture at high temperatures. Though some of the fission products can be easily recovered—for example, uranium is reduced onto an inert cathode by applied potentials—numerous other fission products such as rare earth elements are difficult to recover due to their multivalent oxidation states and side reactions.5 To improve the recovery efficiency of rare earth elements specifically, I proposed investigating the fundamental interactions between rare earth elements in the molten chloride salt and their metallic form (Figure 1). The kinetic pathways and the chemical reactions of these elements, which will be elucidated through spectro-electrochemistry at high temperatures, will give insights on how the recovery efficiency can be improved. Although my research focuses on fundamental science, it will benefit the applied process by generating new scientific knowledge and closing the gap for efficient recycling of the waste: one step at a time.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Pure-Water-Fed Forward-Bias Bipolar Membrane CO 2 Electrolyzer

Coupling renewable electricity to reduce carbon dioxide (CO 2 ) electrochemically into carbon feedstocks offers a promising pathway to produce chemical fuels sustainably. While there has been success in developing materials and theory for CO 2 reduction, the widespread deployment of CO 2 electrolyzers has been hindered by challenges in the reactor design and operational stability due to CO 2 crossover and (bi)carbonate salt precipitation. Herein, we design asymmetrical bipolar membranes assembled into a zero-gap CO 2 electrolyzer fed with pure water, solving both challenges. By investigating and optimizing the anion-exchangelayer thickness, cathode differential pressure, and cell temperature, the forward-bias bipolar membrane CO 2 electrolyzer achieves a CO faradic efficiency over 80% with a partial current density over 200 mA cm –2 at less than 3.0 V with negligible CO 2 crossover. In addition, this electrolyzer achieves 0.61 and 2.1 mV h –1 decay rates at 150 and 300 mA cm –2 for 200 and 100 h, respectively. Postmortem analysis indicates that the deterioration of catalyst/polymer– electrolyte interfaces resulted from catalyst structural change, and ionomer degradation at reductive potential shows the decay mechanism. Furthermore, all these results point to the future research direction and show a promising pathway to deploy CO 2 electrolyzers at scale for industrial applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Finding ways to reduce nuclear waste: searching for the unknown one step at a time

In my home country, Venezuela, research has been stagnant. Due to the political turmoil and the crisis, many educated people have left the country in search for a better life. This has caused a deficit in any technological and scientific advances, making Venezuela one of the first South American countries to have its rate of publications decline by 29% in 2013. Currently, Venezuela lacks the infrastructure and the means to keep up with the research progress as compared to other countries in South America, such as Brazil. Since coming to the United States (US), and currently working for a national laboratory, the active research environment endorses a wide range of careers and engineering programs that allow researchers to thrive at any given field. Researchers have access to funds and tools to succeed in developing materials for the future. There are 17 national laboratories in the US, and all of these have a different research focus/objective. As examples, Los Alamos National Laboratory and Sandia National Laboratory focus is on national homeland security, weapon science, radiation effects, among others. Argonne National Laboratory focuses on nuclear energy, energy storage, high performance computing, etc. At Idaho National Laboratory (INL) the research focuses on innovating nuclear energy and clean energy resources, critical infrastructure materials, along with fuel cycle solutions to manage, dispose and find ways to recycle current and future radiological waste. Compared to other national laboratories, INL focuses slightly more on applied processes and how nuclear energy can be innovated to next reactor design and technologies. The research being conducted at INL made me apply for a Seaborg distinguished postdoctoral position. For the position itself, the researcher must submit a proposal related to actinide chemistry on a research field area. In this position, 50% of my time will be focused on my own proposal. The proposal that I am working on is focused on the innovation of nuclear energy and fuel cycle recycling, which is why I was mainly interested on working at this national laboratory. To give a bit more context of what my proposal is about, a little bit of background is necessary: After the nuclear fuel (UO2) is used in a reactor, the fuel matrix is then characterized by various fission products (FP). Among these FP (including rare earth elements, alkali/alkaline earths, and actinides), many can potentially be recovered through nuclear reprocessing technologies. In pyroprocessing, the used nuclear fuel undergoes electrochemical dissolution into a molten chloride salt mixture in an electrorefiner. Initially, uranium is reduced onto an inert cathode by applied potentials. However, numerous remaining FPs accumulate in the melt and pose challenges for recovery by an inert electrode, particularly the rare earth elements (e.g., Nd, Gd, Pr, Sm) due to their multivalent oxidation states and tendencies toward side reactions, leading to their dissolution in the electrolyte. These recovery challenges result in inefficiencies and necessitate the continual discarding of the molten chloride salt, thereby generating additional waste. Furthermore, the presence of rare earth elements and other fission products in the molten salt electrolyte alters its physical and chemical properties, affecting both uranium recovery efficiency and the longevity of the molten chloride salt. To improve the recovery efficiency of the FP, specifically rare earth elements, I am investigating the fundamental interactions between rare earth elements in the molten chloride salt and their metallic form. The kinetic pathways and the chemical reactions of these elements will give insights on how the recovery efficiency can be improved. The interactions and speciation of these elements are being studied by spectro-electrochemistry at high temperature environments in quartz and other ceramic materials (e.g., alumina crucibles). Some of the challenges I am facing specifically relates the reactivity of some of these elements with different glass and crucible materials. Although my research focuses on fundamental science, it will benefit the applied process by generating new scientific knowledge and closing the gap for an efficient recycling of the waste: one step at a time.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1979

Novel duplex vapor-electrochemical method for silicon solar cells

The dependence of the SiF4 Na reaction initiation time and of the efficiency of the reaction on Na particle size and reaction temperature were studied. Close to 100 percent utilization of Na was obtained, and formation of byproduct fluoro-silicate was decreased to below 10 percent. A SiF4 Na reactor was built to scale up the reaction by a factor of about four and is now being tested. A scaled up melting system was built and successfully used to separate Si from kilogram quantities of SiF4 NaF mixtures. Support studies of the volatilization of NaF performed in a smaller melting system indicated minimal loss of NaF as vapor at 1410 C. The wetting of graphite was also investigated to determine the constituents of the NaF phase which promote good wetting.

Nanis, L.↗
DOE OSTI2024

Upgrading carbon monoxide to bioplastics via integrated electrochemical reduction and biosynthesis

It is challenging to obtain high-value hydrocarbons that are longer than C 3 via electrochemical CO 2 /CO reduction. Integrating electrochemical CO 2 /CO electrolysers with a downstream bioreactor is one solution for obtaining high-value long-chain products, but the electrolytes in these two systems are mismatched, preventing smooth integration. Furthermore we demonstrate a porous solid electrolyte reactor that produces highly selective and electrolyte-free acetate and couple it with a biosynthesis system for generating C 4+ polyhydroxybutyrate bioplastic. A finely tuned electrolyte containing biocompatible salt medium with acetate can be directly injected into the downstream bioreactor without any separation or salt-mixing processes. In the optimized coupled platform, Ralstonia eutropha bacteria can grow with acetate generated from the CO electrocatalytic reduction reactor, and produce bioplastic as the final value-added product.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Formate as an Energy Source to Allow Sugar Fermentation with No Net CO2 Generation: Integration of Electrochemistry with Fermentation

This poster summarizes at a high-level the scope of various groups' work on Formate as an Energy Source to Allow Sugar Fermentation with No Net CO2 Generation: Integration of Electrochemistry with Fermentation. The goals of this research are to develop and demonstrate an integrated process that electrochemically generates formate from CO2 and use the formate as an energy source for the fermentation of sugars to fatty acid methyl esters (FAME) without net CO2 generation wherein formate provides reducing equivalents for sugar fermentation and a chemical looping reactor system takes advantage of intermittent low-cost electricity from wind and solar resources.

BIOMASS FUELS,INORGANIC, ORGANIC, PHYSICAL, AND AN↗
DOE OSTI2023

Two‐Membrane Dual Non‐Aqueous/Aqueous Electrolyte Flow Cell Operation for Electrochemical Conversion of CO 2 to Methyl Formate

Recently, tandem cathodic reactions have been demonstrated in non-aqueous solvents to couple CO 2 reduction to a secondary reaction to create novel species that are not produced in aqueous CO 2 electrolysis. One reaction that can be performed with high selectivity and durability is the electrochemical conversion of CO 2 to formic acid and in-situ esterification with methanol to produce methyl formate. However, the translation to a high-performance flow electrolyzer is far from trivial, as the non-aqueous catholyte leads to reactor challenges including flooding the gas diffusion electrode. Here, in this study, a two-membrane flow electrolyzer with both anion and cation exchange membranes was used with flowing methanol catholyte and aqueous anolyte. This design prevented methanol from flooding the cathode, which was a pervasive limiting issue for electrolyzers with a single membrane. Methyl formate production at 42.9 % faradaic efficiency was achieved with pure methanol in a flow electrolyzer with stable performance beyond 80 min. However, low-water-content catholyte compositions also led to increased cell resistance and lower operating current densities. Thus, with the present ionomer materials there is a tradeoff between methyl formate selectivity and current density depending on water concentration, highlighting a need for new ionomers tailored for desirable non-aqueous solvents such as methanol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1995

Sensing strategies for toxic vapor detection

This work was motivated by the recommendations of the American Conference of Governmental Industrial Hygienists (ACGIH) that threshold limits for hydrazine, H2N-NH2 in air be lowered from 100 to 10 parts-per-billion (ppb) concentration levels. Hydrazine is one of the high-energy propellants used in large volumes in Space Shuttle, Titan, payloads, and other aerospace operations. Since analytical methods presently available for hydrazine detection and/or determination do not satisfy such low levels of detection, the ultimate goal of this research is the development and characterization of a portable and compact chemical sensor ideally capable to detect (in real time) 1 ppb of hydrazine, continuously and reversibly. The laboratory prototype developed as part of this project is comprised of: (1) a reactor part in which H2N-NH2 reacts, generating chemiluminescence emission, with tris(2,2'-bipyridine)ruthenium(III), which is immobilized on an ion-exchange polymeric materials of a perfluorinated hydrocarbon containing sulfonate groups as exchange centers (Nafion); (2) an electrochemical three-electrode cell posed at a potential at which the immobilized ruthenium complex could be reoxidized to the 3-oxidation state (as to provide reversible and continuous detection); and (3) a low power consumption photomultiplier tube to collect and quantitatively integrate the emitted photons with the help of auxiliary electronics and readout device.

Mottola, Horacio A.↗
DOE OSTI2022

Temporal evolution of Pu and Cs sediment contamination in a seasonally stratified pond

There remains a lack of knowledge regarding ecosystem transfer, transport processes, and mechanisms, which influence the long-term mobility of Pu-239 and Cs-137 in natural environments. Monitoring the distribution and migration of trace radioisotopes as ecosystem tracers has the potential to provide insight into the underlying mechanisms of geochemical cycles. This study investigated the distribution of anthropogenic radionuclides Pu-239 and Cs-137 along with total organic carbon, iron, and trace element in contaminated sediments of Pond B at the Savannah River Site (SRS). Pond B received reactor cooling water from 1961 to 1964, and trace amounts of Pu-239 and Cs-137 during operations. Our study collected sediment cores to determine concentrations of Pu-239, Cs-137, and major and minor elements in solid phase, pore water and an electrochemical method was used on wet cores to determine dissolved elemental concentrations. More than 50 years after deposition, Pu-239 and Cs-137 in sediments are primarily located in the upper 5 cm in area where deposition of particulate-bound contaminants was prevalent and located between 5 and 10 cm in areas of high sedimentation, showing a limited migration of Pu-239 and Cs-137. A Factor analysis demonstrated different sediment facies across the pond resulting in a range of geochemical processes controlling accumulation of Pu and Cs. Highest concentrations appear to be controlled by particulate input from the influent canal, dominated by clay, silt, and sand minerals bearing Fe. Elevated Pu-239 in the sediments were observed in areas with high organic matter and higher deposition rate relative to the Pond B system near the outlet indicating strong association of Pu with OM and particulates. Therefore, organic matter cycling likely plays a role in Pu redistribution between sediment and overlying pond water, and deposition in organic rich sediments accumulating near the outlet. Though Pu appears to have been distributed throughout the pond, Cs-137 concentrations remained the highest near the influent canal.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Biogeochemistry of Pond B (Savannah River Site, South Carolina, USA): Sediment Core, Total extraction data, Pond B Savannah River Site July 2019. Subsurface Biogeochemistry of Actinides SFA

Pond B at Savannah River Site (SRS, South Carolina) is a monomictic reservoir that received SRS R reactor cooling water from 1961–1964. Previous studies conducted between the 1980s–1990s on the water column and sediments of Pond B measured trace amounts of Pu (33 MBq 238Pu and 430 MBq 239,240Pu), 241Am, and 137Cs. Since then, the pond has been relatively isolated and the radionuclide concentrations have not been monitored over time. Herein, about 30 years after the last publication on Pond B, we are re-evaluating the geochemistry and radionuclide distribution within Pond B at four locations along a horizontal transect from the inlet to outlet.This study investigated the distribution of anthropogenic radionuclides Pu-239 and Cs-137 along with total organic carbon, iron, and trace element in contaminated sediments of Pond B at the Savannah River Site (SRS). Pond B received reactor cooling water from 1961 to 1964, and trace amounts of Pu-239 and Cs-137 during operations. Our study collected sediment cores to determine concentrations of Pu-239, Cs-137, and major and minor elements in solid phase, pore water and an electrochemical method was used on wet cores to determine dissolved elemental concentrations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Flow field design for zero-gap microbial electrolysis cells using synthetic and real wastewater

Increasing performance in microbial electrolysis cells (MECs) requires the development of optimized reactor configurations with minimal internal resistance and capable to operate with real wastewater. Here, the impact of two different flow fields (serpentine and circular) was examined in zero-gap MECs with synthetic and real wastewaters. The serpentine flow field enabled a uniform distribution of the electrolyte in the anode chamber, resulting in larger current densities at lower flow rates compared to the circular flow field. Electrochemical tests using synthetic media with high buffer capacity revealed more stable and higher performance with the serpentine flow field compared to the circular flow path, producing larger current density (23.7 ± 0.8 A/m 2 vs 21.9 ± 5.6 A/m 2 ), hydrogen production rate (75.8 ± 4.1 L/L-d vs 54.3 ± 2.4 L/L-d), cathodic coulombic efficiency (>91 % vs >50 %), and an overall lower internal resistance (12.5 ± 0.5 mΩm 2 vs 14.8 ± 3.7 mΩm 2 ). Continuous operation for over 30 days with real wastewater indicated higher tolerance of the MECs with serpentine flow field toward media with large concentration of suspended solids, producing a current density of 5.4 ± 1.1 A/m 2 and a hydrogen production rate of 22.2 ± 6.2 L/L-d. Furthermore, the results presented here underscore the importance of reactor design and architecture in optimizing MEC performance for hydrogen production from liquid wastes.

flow path↗
DOE OSTI2024

Overview of NETL’s Low Temperature CO2 Electrolysis Research

This keynote lecture will briefly overview diverse research areas of National Energy Technology Laboratory (NETL) to advance energy and environmental sustainability along with carbon management. Our electrochemistry efforts on carbon conversion directly support the US goal of achieving carbon-free power sector by 2035 and net zero emissions by 2050. Since CO2 electroreduction is highly structure-sensitive, NETL ongoing research has been focused on the rational design and engineering of electrocatalysts to facilitate the CO2 conversion to desirable products with good selectivity, activity, and durability. Different classes and types of electrocatalytic materials will be covered in this talk, from well-defined atomic-scale model catalysts to heterogenous, scalable powder systems at nano- and micro-scale for “real world” performance evaluation. Several spectroscopic, microscopic, and electrochemical characterization techniques along with computational findings will be additionally discussed to gain more insights into the structure-activity relation. The last part of this seminar will provide more detail on how NETL has transitioned from the most common aqueous H-type reactor for lab-scale validation to more realistic full electrolyzer cell in bench-scale prototype. The knowledge, electrocatalytic materials, and device validation achieved from NETL in-house research will be translated to industrial sector for large scale deployment and the anticipated outcome will help advance the development of low temperature CO2 electrolysis technologies.

Nguyen Phan, Thuy Duong↗