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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Fuel-Cell-Powered Vehicle with Hybrid Power Management

Figure 1 depicts a hybrid electric utility vehicle that is powered by hydrogenburning proton-exchange-membrane (PEM) fuel cells operating in conjunction with a metal hydride hydrogen-storage unit. Unlike conventional hybrid electric vehicles, this vehicle utilizes ultracapacitors, rather than batteries, for storing electric energy. This vehicle is a product of continuing efforts to develop the technological discipline known as hybrid power management (HPM), which is oriented toward integration of diverse electric energy-generating, energy-storing, and energy- consuming devices in optimal configurations. Instances of HPM were reported in five prior NASA Tech Briefs articles, though not explicitly labeled as HPM in the first three articles: "Ultracapacitors Store Energy in a Hybrid Electric Vehicle" (LEW-16876), Vol. 24, No. 4 (April 2000), page 63; "Photovoltaic Power Station With Ultracapacitors for Storage" (LEW- 17177), Vol. 27, No. 8 (August 2003), page 38; "Flasher Powered by Photovoltaic Cells and Ultracapacitors" (LEW-17246), Vol. 27, No. 10 (October 2003), page 37; "Hybrid Power Management" (LEW-17520), Vol. 29, No. 12 (December 2005), page 35; and "Ultracapacitor-Powered Cordless Drill" (LEW-18116-1), Vol. 31, No. 8 (August 2007), page 34. To recapitulate from the cited prior articles: The use of ultracapacitors as energy- storage devices lies at the heart of HPM. An ultracapacitor is an electrochemical energy-storage device, but unlike in a conventional rechargeable electrochemical cell or battery, chemical reactions do not take place during operation. Instead, energy is stored electrostatically at an electrode/electrolyte interface. The capacitance per unit volume of an ultracapacitor is much greater than that of a conventional capacitor because its electrodes have much greater surface area per unit volume and the separation between the electrodes is much smaller.

Eichenberg, Dennis J.↗
DOE OSTI2021

Copper iodide nanoparticles as a hole transport layer to CdTe photovoltaics: 5.5 % efficient back-illuminated bifacial CdTe solar cells

We report the role of copper iodide (CuI) nanoparticles (NPs) as a hole transport layer (HTL) in cadmium sulfide/cadmium telluride (CdS/CdTe) photovoltaics. These CuI NPs were prepared using solution processing at room temperature and used to fabricate monofacial and bifacial CdTe solar cells with different back contacts. Using CuI/Au as the back contact, the device efficiency reached to 14.8% with outstanding fill factor (FF) of 79.2%. Replacing the gold (Au) electrode with sputtered transparent indium tin oxide (ITO), a CuI/ITO back contact yielded photoconversion efficiencies (PCEs) of 11.6% and 5.5% under front and back illumination respectively. Bifacial devices (CdTe/ITO) without the CuI NP HTL have an efficiency of 7.0% and 1.0% for front and back illumination, respectively. For CuI/ITO, a current collection of 12.0 mAcm -2 was observed upon back illumination which significantly improved over an ITO-only back contact (5.0 mAcm -2 ). The PCE obtained from back illumination was enhanced when using CuI NPs as the HTL due to the reduced back barrier height, and improved back interface as determined by temperature dependent current vs. voltage characteristics and impedance spectroscopy analysis. The improvement in device performance of the bifacial configuration is a significant step forward toward realizing thin film photovoltaic modules which harvest energy incident on the rear of the module.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Redesigning Photoelectrodes So They Can Work in the Light and Dark

Unassisted photoelectrochemical (PEC) reactions, such as H2 generation and CO2 reduction, are limited by the durability of the immersed photoelectrode. Small band gap semiconductors, like Si, are efficient at utilizing a large portion of the solar spectrum but are not stable in aqueous environments without protection. While great strides have been made to improve stability under constant illumination, dark stability remains relatively unexamined and presents great challenges for durable PEC systems. Cathodic protection is an established electrochemical method for preventing metal electrode degradation in harsh conditions. Similar protection strategies cannot be applied to traditional two-terminal (2T) semiconductor photoelectrodes because of their inability to pass reverse bias current in the dark. New, three-terminal (3T) photovoltaic (PV) architectures introduce additional degrees of freedom in traditional 2T PEC operations by adding an extra electrical contact for an alternative low resistance path to protect the photoelectrode and drive electrochemical reactions, even in the dark. Here, we investigate bare 3T Si PV devices operating as photocathodes in aqueous methyl viologen electrolyte. The 3T architecture provides additional capabilities to PEC systems such as cathodic protection, the ability to drive reactions with or without illumination, and in situ switching between different operational modes. We show that 3T-based Si photocathodes maintain PEC activity after several hours of light/dark cycling. This work helps advance PEC use in real-world conditions where variable illumination must be considered.

cathodic protection↗
DOE OSTI2022

Bulk Oxygen Stabilization via Electrode–Electrolyte Interphase Tailored Surface Activities of Li–Rich Cathodes

The O3-type Li-rich layered oxides (LLOs) are approaching industrial applications as high-energy cathode materials for Li-ion batteries (LIBs), however, they suffer from rapid performance decay associated with oxygen activities. The interplay between surface and bulk transformations in LLOs, especially the electrochemical behaviors of oxygen anions, remains elusive. Here, by regulating the surface of an O3-type LLO (Li 1.13 Mn 0.517 Ni 0.256 Co 0.097 O 2 ) using an all-fluorinated electrolyte, an enhanced capacity retention from 57.4% to 85.3% and a suppressed voltage decay from 1.34 mV cycle –1 to 0.58 mV cycle –1 within 300 cycles are realized. The performance enhancement is attributed to the thin, uniform, robust, and compact F-rich cathode-electrolyte interphase (CEI), which suppresses various types of oxygen-related surface degradation and, more importantly, stabilizes the bulk oxygen reactions. Finally, through the combined experimental and theoretical studies, this work directly reveals the intriguing association between the surface and bulk oxygen activities and demonstrates that optimizing the interphase is an effective approach for improving the stability of high-energy battery cathodes involving oxygen redox reactions.

25 ENERGY STORAGE↗
DOE OSTI2021

Elucidating Mass Transport Regimes in Gas Diffusion Electrodes for CO 2 Electroreduction

Gas diffusion electrodes (GDEs) have shown promising performance for the electrochemical reduction of CO 2 (CO 2 R). In this study, a resolved, pore scale model of electrochemical reduction of CO 2 within a liquid-filled catalyst layer is developed. Three CO 2 mass transport regimes are identified in which the CO 2 penetration depth is controlled by CO 2 consumption in the electrolyte, CO 2 conversion along the solid-electrolyte double-phase boundaries (DPBs), and CO 2 conversion concentrated around the gas–solid–electrolyte triple-phase boundaries (TPBs). While it is possible for CO 2 R to be localized around the TPBs, in systems with submicron pore radii operating at <1 A cm –2 CO 2 R will be distributed across the DPBs within the catalyst layer. This validates the assumption of pore-scale uniformity implicit in popular, volume-averaged GDE models. Overall, the CO 2 conversion efficiency depends strongly on the governing mass transport regime, and operational-phase diagrams are constructed to guide the catalyst layer design.

10 SYNTHETIC FUELS↗
DOE OSTI2023

Modulating the Mixing Gibbs Free Energy to Enhance Solid–Liquid Phase Separation for High–Performance Organic Solar Cells

Organic solar cells (OSC) feature a hierarchical structure with the electron donor/acceptor layer sandwiched by anode and cathode, which raises the importance of controlling the molecular crystal orientation, domain size, and vertical distribution to facilitate the charge collection at electrodes. However, the similar conjugated backbone of donor/acceptor material and fast film–formation kinetics have led to spinodal–decomposition–orientated phase separation that result in the film presenting an intimately mixed morphology and random molecular orientation. To solve the issue, the mixing Gibbs free energy–triggered solid–liquid phase separation during the film formation process is enhanced by solidifying one component and solvating the other based on a liquid additive. Following the liquid evaporation process, a favorable vertical distribution is obtained. Meanwhile, the prolonged solvation process enlarges the domain size and assists the molecules to diffuse and orient properly, enabling better exciton/charge dynamics during the power conversion processes. As a result, the fabricated devices exhibit a fill factor over 80% and an efficiency of 18.72%, which is one of the top efficiencies for binary OSCs. In conclusion, insights and a methodology is provided here to manipulate the organic donor/acceptor phase separation in terms of mixing Gibbs free energy.

14 SOLAR ENERGY↗
DOE OSTI2022

Red-Ox Robust SOFC Stacks for Affordable, Reliable Distributed Generation Power Systems

While SOFC systems are expected to operate reliably and with limited degradation in steady state or transient performance, SOFC stacks may ultimately fail due to the loss of structural integrity of one or several of the cells as a result of the weakening of the materials and interfaces due to physico-chemical changes that occur during continuous operation as a result of plastic and creep deformations, modification of the temperature profile, and/or degradation of the electrochemical performance of the cells. Degradation mechanisms originating from the cell components include coarsening of the microstructure over time; decomposition of materials; chemical reaction of electrode materials with electrolyte at the interface; delamination from each other; and for the anode, coking and sulfur poisoning. Of all the reliability issues that may occur for SOFCs, the main limitation for Ni-based cermet anodes (e.g., NiO-YSZ) is the poor stability during reduction-oxidation (red-ox) cycling. This project was aimed at the development of ceramic anode SOFCs based on SFCM (SrFe0.2Co0.4Mo0.4O3), which is a conductive perovskite that is red-ox stable. Additionally, the project involved the development of a red-ox robust stack. Scale up of SFCM-based cells to a large format (10 cm by 10 cm) cell size was achieved as well as a maximum power density of 0.9 W/cm 2 at 600 °C (>0.6 W/cm 2 at 0.6 V). Up to a 10-cell stack was successfully assembled and demonstrated, and cells showed similar performance in reformed, pipeline natural gas as in hydrogen. Finally, a 3-cell stack was red-ox cycled without degradation for 40 cycles at ~600 °C.

03 NATURAL GAS↗
DOE OSTI2025

Development of a scalable, robust electrocatalytic technology for conversion of CO 2 to formic acid via microstructured materials

This project was funded by the Bioenergy Engineering for Product Synthesis (BEEPS) program under the Funding Opportunity Announcement (FOA) DE-FOA-0001916 Topic Area 5 “Rewiring Carbon Utilization”. This FOA sought projects that would electrocatalytically reduce CO 2 to a carbon intermediate and then upconvert to a multi-carbon product or fuel via non-photosynthetic biological system engineering. The project sought to combine the expertise of OCO Chem, whose chief scientist had previously developed an efficient electrocatalytic reactor for conversion of CO 2 to formate with potential to scale, Montana State University investigators who had recently patented a method for laterally grading membranes with the potential of improving reactant distribution and more uniform efficiency across membrane-based reactors, and University of South Florida which had recently discovered a novel C-C bond forming reaction not known to naturally occur in biological systems and which uses C1 substrates and circumvents the central microbial metabolism.

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

Understanding and Advancing Bifacial Thin Film Solar Cells under Dual Illumination

There is a great deal of interest in increasing the energy yield from thin film solar cells by implementing bifacial operation. However, deleterious band bending and high interface recombination at the back transparent electrode can cause problems. Herein, it is investigated how bifacial thin film devices perform when illuminated through the front, back, and simultaneously through both interfaces using numerical modeling. It is shown that the downward band bending near the back interface is reduced during illumination when the carrier concentration is low. This effect is not found when the doping is relatively high, but the minority carrier distribution is still modified. Under either condition, the power generated under bifacial illumination exceeds the sum of the power generated when the illumination is solely from the back or the front. It is also shown that the back-illuminated device performance is independent of the angle at which the light enters the back of the device, which provides accommodation for scattered light. Finally, the power enhancement is calculated for bifacial devices relative to front-illuminated devices, and is shown that any significant loss in frontside power generation is difficult to overcome with back illumination under real-world albedo conditions.

CdTe↗
DOE OSTI2020

A hybrid cyt c maturation system enhances the bioelectrical performance of engineered Escherichia coli by improving the rate-limiting step

Bioelectronic devices can use electron flux to enable communication between biotic components and abiotic electrodes. We have modified Escherichia coli to electrically interact with electrodes by expressing the cytochrome c from Shewanella oneidensis MR-1. However, we observe inefficient electrical performance, which we hypothesize is due to the limited compatibility of the E. coli cytochrome c maturation (Ccm) systems with MR-1 cytochrome c. Here we test whether the bioelectronic performance of E. coli can be improved by constructing hybrid Ccm systems containing protein domains from both E. coli and S. oneidensis MR-1. The hybrid CcmH increased cytochrome c expression by increasing the abundance of CymA 60%, while only slightly changing the abundance of the other cytochromes c. Electrochemical measurements showed that the overall current from the hybrid ccm strain increased 121% relative to the wildtype ccm strain, with an electron flux per cell of 12.3 ± 0.3 fA·cell -1 . Additionally, the hybrid ccm strain doubled its electrical response with the addition of exogenous flavin, and quantitative analysis of this demonstrates CymA is the rate-limiting step in this electron conduit. These results demonstrate that this hybrid Ccm system can enhance the bioelectrical performance of the cyt c expressing E. coli, allowing the construction of more efficient bioelectronic devices.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

(Photo)Electrocatalytic CO 2 Reduction at the Defective Anatase TiO 2 (101) Surface

Excessive carbon dioxide (CO 2 ) emissions by combustion of fossil fuels are linked to global warming and rapid climate change. One promising route to lowering the concentration of CO 2 in the atmosphere is to reduce it to useful small molecules via photoelectrocatalytic hydrogenation, which would enable solar energy storage with a zero-carbon emission cycle and perform a more efficient separation of the photogenerated electron and hole pair than pure photocatalysis. Indeed, photoelectrocatalytic CO 2 reduction has been an intense focus of research. Using the density functional theory (DFT), we studied the CO 2 reduction reaction on the defective anatase TiO 2 (101) surface, at both the solvent/catalyst and the electrolyte/catalyst interfaces. The analysis of the electronic structure of the surface shows a contrast between the solvent/catalyst and the electrolyte/catalyst interfaces, which results in the two corresponding catalytic cycles being distinct. Furthermore, our study explains at the electronic and mechanistic levels why methanol is the main product in the presence of the electrolyte and why the overpotential is not only controlled by the reaction process but also by the diffusion process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Leveraging Cell Expansion Sensing in State of Charge Estimation: Practical Considerations

Measurements such as current and terminal voltage that are typically used to determine the battery’s state of charge (SOC) are augmented with measured force associated with electrode expansion as the lithium intercalates in its structure. The combination of the sensed behavior is shown to improve SOC estimation even for the lithium ion iron phosphate (LFP) chemistry, where the voltage–SOC relation is flat (low slope) making SOC estimation using measured voltage difficult. For the LFP cells, the measured force has a non-monotonic F–SOC relationship. This presents a challenge for estimation as multiple force values can correspond to the same SOC. The traditional linear quadratic estimator can be driven to an incorrect SOC value. To address these difficulties, a novel switching estimation gain is used based on determining the operating region that corresponds to the actual SOC. Moreover, a drift in the measured force associated with a shift of the cell SOC–expansion behavior over time is addressed with a bias estimator for the force signal. The performance of Voltage-based (V) and Voltage and Force-based (V&F) SOC estimation algorithms are then compared and evaluated against a desired ±5% absolute error bound of the SOC using a dynamic stress test current protocol that tests the proposed estimation scheme across wide range of SOC and current rates.

25 ENERGY STORAGE↗
DOE OSTI2025

Capability in Theory, Modeling, and Validation for a Range of Innovative Fusion Concepts using High-Fidelity Moment-Kinetic Models

A computational modeling capability is created and available to the fusion community to understand and design lower-cost and innovative fusion concepts. The approach uses high- fidelity kinetic, moment-kinetic, and moment models and includes sophisticated plasma- boundary interactions. A majority of fusion-relevant simulations are performed with magnetohydrodynamic models and hybrid particle-in-cell codes, with limited-fidelity electron and kinetic physics. However, in fusion configurations like Z-pinches, field-reversed- configurations, plasma jet magneto-inertial fusion, spinning mirrors, and others, kinetic effects (both electron and ions) are critical to understand the physics and design scaling into the highly kinetic regime of a burning fusion plasma. Furthermore, as present fusion machines move towards a burning plasma regime, liquid-metal blankets are needed to handle first-wall heat- flux, reduce erosion, and eventually for energy conversion and fuel breeding. The work performed under this ARPA-E BETHE Capability Team advances the state-of-the-art in modeling and understanding plasma dynamics in fusion devices and its coupling with liquid-metal dynamics. These are critical areas of research for fusion energy to become realizable. To address these complex problems, we have leveraged and extended computational capabilities through the code, Gkeyll (developed jointly with Princeton Plasma Physics Laboratory and academic partners), for kinetic and moment modeling of fusion plasmas. The Concept Teams supported by this Capability Team include the Wisconsin High-field Axisymmetric Mirror (WHAM), Centrifugal Mirror Experiment (CFME), Plasma-Jet Magneto- Inertial Fusion (PJMIF), and solid and liquid wall plasma-material interaction studies relevant to a number of fusion concepts including Zap Energy’s Z-pinch. This software is open-source and available to the fusion community as a high-fidelity tool for the design of lower-cost fusion experiments. 3D gyrokinetic simulations of WHAM are now possible for long enough time scales to understand the evolution of interchange instabilities. 3D multi-fluid simulations of CMFE at higher Mach numbers are now possible for detailed design iterations with the goal of stability. The state-of-the-art in understanding shock formation and shock mitigation regimes in merging liners for PJMIF have been furthered by our kinetic simulations. Our novel models and frameworks studying plasma-material interaction by incorporating wall emission for various solid wall materials of relevance to pulsed and steady fusion concepts have advanced the state-of-the-art in our understanding of particle fluxes, heat fluxes, and other quantities at cathodes and anodes. The results from this work may explain discrepancies between experimental and theoretical predictions of achieved current densities in pulsed concepts such as Z-pinches. Another significant contribution of this Capability Team is the development and deployment of a novel experimental platform, LEX (Liquid Electrode eXperiment), at Virginia Tech to understand liquid metal free-surface response to electromagnetic pulses. The novel experiments along with model validation quantified the effect of different materials and sizes of liquid metal droplets on the radiative power balance of fusion plasmas for pulsed concepts. Furthermore, these experiments provided mitigation strategies for violent liquid metal response for high current pulses as would be expected in fusion regimes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2010

Electrochemical Hydrogen Peroxide Generator

Two-electron reduction of oxygen to produce hydrogen peroxide is a much researched topic. Most of the work has been done in the production of hydrogen peroxide in basic media, in order to address the needs of the pulp and paper industry. However, peroxides under alkaline conditions show poor stabilities and are not useful in disinfection applications. There is a need to design electrocatalysts that are stable and provide good current and energy efficiencies to produce hydrogen peroxide under acidic conditions. The innovation focuses on the in situ generation of hydrogen peroxide using an electrochemical cell having a gas diffusion electrode as the cathode (electrode connected to the negative pole of the power supply) and a platinized titanium anode. The cathode and anode compartments are separated by a readily available cation-exchange membrane (Nafion 117). The anode compartment is fed with deionized water. Generation of oxygen is the anode reaction. Protons from the anode compartment are transferred across the cation-exchange membrane to the cathode compartment by electrostatic attraction towards the negatively charged electrode. The cathode compartment is fed with oxygen. Here, hydrogen peroxide is generated by the reduction of oxygen. Water may also be generated in the cathode. A small amount of water is also transported across the membrane along with hydrated protons transported across the membrane. Generally, each proton is hydrated with 3-5 molecules. The process is unique because hydrogen peroxide is formed as a high-purity aqueous solution. Since there are no hazardous chemicals or liquids used in the process, the disinfection product can be applied directly to water, before entering a water filtration unit to disinfect the incoming water and to prevent the build up of heterotrophic bacteria, for example, in carbon based filters. The competitive advantages of this process are: 1. No consumable chemicals are needed in the process. The only raw materials needed are water and oxygen or air. 2. The product is pure and can therefore be used in disinfection applications directly or after proper dilution with water. 3. Oxygen generated in the anode compartment is used in the electrochemical reduction process; in addition, external oxygen is used to establish a high flow rate in the cathode compartment to remove the desired product efficiently. Exiting oxygen can be recycled after separation of liquid hydrogen peroxide product, if so desired. 4. The process can be designed for peroxide generation under microgravity conditions. 5. High concentrations of the order of 6-7 wt% can be generated by this method. This method at the time of this reporting is superior to what other researchers have reported. 6. The cell design allows for stacking of cells to increase the hydrogen peroxide production. 7. The catalyst mix containing a diquaternary ammonium compound enabled not only higher concentration of hydrogen peroxide but also higher current efficiency, improved energy efficiency, and catalyst stability. 8. The activity of the catalyst is maintained even after repeated periods of system shutdown. 9. The catalyst system can be extended for fuel-cell cathodes with suitable modifications.

Tennakoon, Charles L. K.↗
DOE OSTI2022

Triggering Anionic Redox Activity in Li 3 NbS 4 Through Cationic Disordering or Substitution

Extensive utilization of Li-ion batteries for varieties of applications necessitates ceaseless improvements of electrode materials for achieving higher energy density. Towards this goal, Li-rich layered oxides exhibiting high capacity due to cumulated cationic and anionic redox activities are under study for nearly a decade. Still, several unanswered questions remain with respect to these Li-driven anionic redox reactions in terms of the activation process and long-term consequences upon cycling. Here, the Li-rich Li 3 NbS 4 phase is focused, and synthesized as two different polymorphs, namely ordered and disordered phases. From analyses of their chemical and electrochemical properties, a crystal-electronic structure relationship is unraveled that triggers the anionic redox activity in these compounds. Moreover, through complementary theoretical calculations, the capability of cationic disorder to trigger anionic redox activity via the hybridization of cationic and non-bonding anionic energy levels is shown. This finding is further supported by the appearance of anionic redox activity by introducing the disorder through cationic substitution. Altogether, the insights derived here can help in designing new anionic redox materials with optimum performances for practical applications.

25 ENERGY STORAGE↗
DOE OSTI2023

Effect of the Nature of Both Cation and Anion Substitution on the Structural Symmetry of Li‐Rich 3 d ‐Metal Chalcogenide Electrodes

Abstract Li‐rich layered chalcogenides have recently led to better understanding of the anionic redox process and its associated high capacity while providing ways to overcome its practical limitations of voltage fade and irreversibility. This study reports on the feasibility of triggering anionic activity in Li 2 TiS 3 , through anionic substitution (Se for S) or cationic substitution (Fe for Ti). Herein, the chalcogenide chemical space is further explored to prepare mono‐substituted Li 1.7 Ti 0.85 Mn 0.45 Ch 3 (Ch = S/Se) and doubly substituted cationic and anionic phases (Li 1.7 Ti 0.85 Fe 0.45 S 3‐z Se z ) which crystallize either in the O3‐ or O1‐type structures depending upon substituents. All series show a bell‐shape capacity variation as function of the transition metal (TM) substitution degree with values up to 240 mAh g −1 . For specific compositions, a structural O3 to O1 phase transition is observed upon Li removal, which is not reversible upon Li re‐insertion due to kinetic limitations and negatively affects long‐term cycling performance. Density functional theory (DFT) calculations confirm the O3/O1 relative stability along the different series and point subtle electronic differences in the TM‐doping, rationalizing the structural and electrochemical behaviors of these phases upon cycling. These findings provide further insights into the link between structural and electronic stability, which is of key importance for designing chalcogenide‐based anionic redox compounds.

Chemistry↗
DOE OSTI2022

Tuning Surface Acidity of Mixed Conducting Electrodes: Recovery of Si‐Induced Degradation of Oxygen Exchange Rate and Area Specific Resistance

Abstract Metal oxides are an important class of functional materials, and for many applications, ranging from solid oxide fuel/electrolysis cells, oxygen permeation membranes, and oxygen storage materials to gas sensors (semiconducting and electrolytic) and catalysts, the interaction between the surface and oxygen in the gas phase is central. Ubiquitous Si‐impurities are known to impede this interaction, commonly attributed to the formation of glassy blocking layers on the surface. Here, the surface oxygen exchange coefficient ( k chem ) is examined for Pr 0.1 Ce 0.9 O 2‐δ (PCO), a model mixed ionic electronic conductor, via electrical conductivity relaxation measurements, and the area‐specific resistance (ASR) by electrochemical impedance spectroscopy. It is demonstrated that even low silica levels, introduced by infiltration, depress k chem by a factor 4000, while the ASR increases 40‐fold and we attribute this to its acidity relative to that of PCO. The ability to fully regenerate the poisoned surface by the subsequent addition of basic Ca‐ or Li‐species is further shown. This ability to not only recover Si‐poisoned surfaces by tuning the relative surface acidity of an oxide surface, but subsequently outperform the pre‐poisoned response, promises to extend the operating life of materials and devices for which the catalytic oxygen/solid interface reaction is central.

30 DIRECT ENERGY CONVERSION↗