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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

REIMAGINING HEAT EXCHANGERS FOR NEXT GENERATION ENVIRONMENTAL SYSTEMS

Air-to-refrigerant heat exchangers (HXs) are essential components in space conditioning, refrigeration, and power systems, and recent efforts have focused on making these devices more compact, reducing refrigerant charge and lowering manufacturing costs. Historically, HX innovation has been limited by available computational resources, design tools, and manufacturing constraints. The best available technologies utilize tube-fin and micro- or macro-channel tubes with fins, which are not necessarily the optimal designs achievable with current technology. In this paper, we highlight the latest advancements in air-to-refrigerant HXs, specifically emphasizing innovations achieved through shape and topology optimization. A multi-scale design optimization approach is introduced, alongside similar methods in literature, which enable highly sophisticated shape-optimized tube designs with more than 50% reduction in size and 25% reduction in refrigerant charge, essential for A3 refrigerant charge limit compliance. The frameworks integrate traditional heat and mass transfer science with state-of-the-art machine learning, genetic algorithms, and adjoint algorithms to create novel designs. While many of these innovative designs may not be manufacturable using conventional methods, they allow us explore the boundaries of what is possible. These novel air-to-refrigerant HXs are key enablers for ultra-low-refrigerant charge heat pump and refrigeration systems.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2026

Geothermal Heat Pump System Showcase: Short-Term Validation of Borehole Heat Exchanger Performance from Field Data to Numerical Modeling: Preprint

Since 2011, a geothermal heat pump (GHP) system has been operating to provide space heating and cooling for the Solar Radiation and Research Laboratory building at the National Laboratory of the Rockies (NLR) in Golden, Colorado. The system consists of 23 vertical boreholes, each extending to a depth of 300 ft (91 m), connected to 11 water-to-air heat pump units and four circulation pumps. Between fiscal years 2023 and 2025, additional power meters and temperature sensors were retrofitted to support detailed system performance assessment and model development. This study presents preliminary monitoring results and the development of an initial numerical model of the borehole heat exchanger field. The model incorporated site-specific geometry, ground thermal properties derived from thermal response tests, and ambient temperatures, and simulated system behavior over a representative operating day in September. Model predictions of outlet temperatures were compared against corresponding field measurements. Results showed that modeling initialized with a simplified linear subsurface temperature gradient presents systematic discrepancies in outlet temperature, whereas incorporating depth-resolved borehole temperature measurements for initialization yields substantially improved agreement with observations. The findings highlight the sensitivity of short-term predictive modeling to the representation of initial subsurface thermal conditions and underscore the value of high-resolution field measurements for model calibration and validation. These preliminary results inform ongoing efforts to extend the modeling framework to longer time horizons and to refine monitoring and modeling strategies that support the design guidance and operational optimization of GHP systems in research and commercial buildings.

15 GEOTHERMAL ENERGY↗
DOE OSTI2025

REFRACTORY COMPACT HEAT EXCHANGERS WITH EMBEDDED SENSORS ENABLED BY HYBRID ADVANCED SINTERING AND ADDITIVE APPROACH

Structural health monitoring (SHM) of compact heat exchangers (CHXs) operating in extreme environments is essential for ensuring system reliability, safety, and longevity. This study presents the development of high-temperature sensors fabricated via aerosol jet printing (AJP) using platinum ink, selected for its exceptional thermal stability, oxidation resistance, and electrical conductivity. AJP enables precise deposition of fine-feature sensor patterns onto complex geometries, making it well-suited for integration within CHX architectures. To enhance sensor durability, an alumina-based ceramic protective layer was printed over the platinum sensing elements. The sensors demonstrated stable, repeatable performance up to 900?°C during extended thermal cycling. A custom test setup was developed to evaluate sensor accuracy and robustness under steady-state and transient conditions. Substrate screening identified HG-1 ceramic-coated stainless steel as the most effective platform, offering strong adhesion and low resistance. Furthermore, electric field-assisted sintering (EFAS) was employed to embed the sensors into stainless steel 316L matrices without degrading their functionality. Post-embedding electrical tests confirmed sensor integrity, and initial characterization suggests strong potential for in-situ monitoring. This work provides a scalable strategy for integrating high-performance temperature sensors directly into refractory components, advancing embedded SHM technologies for harsh operating environments.

36 - MATERIALS SCIENCE↗
DOE OSTI2023

ECAR-7547 Rev 0 MARVEL Intermediate Heat Exchanger Liner ASME Analysis

This ECAR analyzes the Secondary Coolant System liner, otherwise known as the Intermediate Heat Exchanger (IHX) Liner, as an ASME Section VIII, Division 1 pressure vessel. This analysis is only necessary in the event of a failure of the primary coolant boundary, in which case the IHX liner acts as a secondary confinement boundary to prevent primary coolant leakage. The liner main body or vessel is analyzed, as well as the liner flange ring.

21 - SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLAN↗
DOE OSTI2021

Porphyrin Aerogel Catalysts for Oxygen Reduction Reaction in Anion-Exchange Membrane Fuel Cells

Platinum group metal (PGM)-free catalysts for oxygen reduction reaction have shown high oxygen reduction reaction activity in alkaline media. In order to further increase the power density of anion-exchange membrane fuel cells (AEMFCs), PGM-free catalysts need to have a high site density to reach high current densities. In this work, synthesis, characterization, and utilization of heat-treated iron porphyrin aerogels are reported as cathode catalysts in AEMFCs. The heat treatment effect is thoroughly studied and characterized using several techniques, and the best performing aerogel is studied in AEMFC, showing excellent performance, reaching a peak power density of 580 mW cm –2 and a limiting current density of as high as 2.0 A cm –2 , which can be considered the state-of-the-art for PGM-free based AEMFCs.

25 ENERGY STORAGE↗
DOE OSTI2020

Low‐PGM and PGM‐Free Catalysts for Proton Exchange Membrane Fuel Cells: Stability Challenges and Material Solutions

Abstract Fuel cells as an attractive clean energy technology have recently regained popularity in academia, government, and industry. In a mainstream proton exchange membrane (PEM) fuel cell, platinum‐group‐metal (PGM)‐based catalysts account for ≈50% of the projected total cost for large‐scale production. To lower the cost, two materials‐based strategies have been pursued: 1) to decrease PGM catalyst usage (so‐called low‐PGM catalysts), and 2) to develop alternative PGM‐free catalysts. Grand stability challenges exist when PGM catalyst loading is decreased in a membrane electrode assembly (MEA)—the power generation unit of a PEM fuel cell—or when PGM‐free catalysts are integrated into an MEA. More importantly, there is a significant knowledge gap between materials innovation and device integration. For example, high‐performance electrocatalysts usually demonstrate undesired quick degradation in MEAs. This issue significantly limits the development of PEM fuel cells. Herein, recent progress in understanding the degradation of low‐PGM and PGM‐free catalysts in fuel cell MEAs and materials‐based solutions to address these issues are reviewed. The key factors that degrade the MEA performance are highlighted. Innovative, emerging material concepts and development of low‐PGM and PGM‐free catalysts are discussed.

Du, Lei↗
DOE OSTI2026

Adsorption-Engineered Hydrocarbon Ionomers for Durable Proton-Exchange Membrane Fuel Cells

Reducing reliance on perfluoroalkyl substances (PFAS) in proton-exchange membrane fuel cells requires hydrocarbon ionomers that combine high performance with long-term durability, a persistent challenge in catalyst-layer design. Here, we identify oxidation-driven ionomer-catalyst interfacial degradation as a dominant failure pathway in hydrocarbon ionomer-bonded cathodes and introduce an adsorption-engineering strategy to overcome this limitation. The comparison of a commercial sulfonated poly(phenylene) (Pemion) with structurally engineered sulfonated poly(fluorene)s demonstrated that electrode durability is governed by the interplay between ionomer adsorption strength and resistance to oxidative degradation on carbon-supported Pt catalysts. A poly(fluorene) ionomer with mobile alkyl sulfonic acid groups forms resilient interfaces, delivering 1.28 A cm−2 at 0.65 V under fully humidified H2/air conditions (80°C and 150 kPaabs), comparable to Pemion. After 90,000 accelerated potential cycles, the poly(fluorene)-bonded cathode exhibits significantly improved durability, with only 29% performance loss compared to 58% for Pemion; further molecular refinement reduces the loss to 17%, approaching that of Nafion-bonded cathodes (14%). These findings establish adsorption-engineered ionomer design that decouples interfacial anchoring from oxidative degradation as a general strategy for achieving durable, high-performance PFAS-free PEM fuel cell electrodes.

08 HYDROGEN↗
DOE OSTI2023

The Dynamics of Oxygen Ion Exchange in Epitaxial Strontium Cobaltite Bilayers

Abstract The exchange of ions across interfaces is key to the field of iontronics, where the properties of the device can be altered by the local ion concentration. This study investigates a complex oxide system where structural and electronic phase transitions can be driven by changes in the concentration of oxygen ions. In situ coherent X‐ray studies are conducted on epitaxial bilayers of insulating SrCoO 2.5 and metallic SrCoO 3 − δ . The diffusion of oxygen ions across the bilayer is studied with X‐ray photon correlation spectroscopy to capture the dynamical behavior of the interface in reducing and oxidizing environments. The behavior is strongly asymmetric, with much slower dynamics appearing in reducing versus oxidizing environments. According to the correlation functions determined from different points in reciprocal space, this study finds that the dynamics near the center of the SrCoO 2.5 crystal are generally similar to those near the heterointerfaces. The results suggest that the interface is stable and reversible, making SrCoO x a model system for the study of iontronic behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Understanding Operando Water Management in Hydroxide‐Exchange‐Membrane Fuel Cells

The water balance in hydroxide-exchange-membrane fuel cells (HEMFCs) is a key challenge for improved performance and durability, intimately linked with the various interfaces and coupled phenomena. For every 4 electrons produced, 4 water molecules are generated in the anode and 2 consumed in the cathode, while electroosmosis transports water across the HEM from the cathode to the anode. Consequently, a concentration gradient drives water back, from anode to cathode. Ineffective water management could lead to cathode dry-out, limiting reaction rate and causing ionomer degradation, or to anode flooding. To address these concerns, it is critical to measure the water transport operando . Herein, a home-built water-flux station is used to measure total water flux during cell operation with different inlet relative humidities and back pressures. Increasing the HEM thickness fourfold decreases the water flux at high current density, and utilizing microporous layers on both the anode and cathode decreases the water flux from the anode to the cathode. However, the most significant variable in changing the water flux was found by increasing the anode back pressure. Furthermore, humidity cycling significantly changed electrochemical performance without affecting the overall water fluxes. These findings can be translated to other devices utilizing an HEM.

AEMFC↗
DOE OSTI2021

Superstructured Biomaterials Formed by Exchange Dynamics and Host–Guest Interactions in Supramolecular Polymers

Dynamic and reversible assembly of molecules is ubiquitous in the hierarchical superstructures of living systems and plays a key role in cellular functions. Recent work from the laboratory reported on the reversible formation of such superstructures in systems of peptide amphiphiles conjugated to oligonucleotides and electrostatically complimentary peptide sequences. Here, a supramolecular system is reported upon where exchange dynamics and host–guest interactions between β-cyclodextrin and adamantane on peptide amphiphiles lead to superstructure formation. Superstructure formation with bundled nanoribbons generates a mechanically robust hydrogel with a highly porous architecture that can be 3D printed. Functionalization of the porous superstructured material with a biological signal results in a matrix with significant in vitro bioactivity toward neurons that could be used as a supramolecular model to design novel biomaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Highly Durable Fluorinated High Oxygen Permeability Ionomers for Proton Exchange Membrane Fuel Cells

For proton exchange membrane fuel cells to be cost-competitive in light- and heavy-duty vehicle applications, their Pt content in the catalyst layers needs to be lowered. However, lowering the Pt content results in voltage losses due to high local oxygen transport resistances at the ionomer–Pt interface. It is therefore crucial to use ionomers that have higher oxygen permeability than Nafion. In this paper, novel high oxygen permeability ionomers (HOPIs) are presented, with up to five times higher oxygen permeability than Nafion, synthesized by copolymerization of perfluoro-2,2-dimethyl-1,3-dioxole (PDD) with perfluoro(4-methyl-3,6-dioxaoct-7-ene) sulfonyl fluoride (PFSVE). PDD is the source of higher permeability due to its open ring structure, while PFSVE provides ionic conductivity. Optimization of PDD content and equivalent weight enables increased fuel cell performance, mainly at high current densities, where HOPIs can achieve power densities >1.25 W cm -2 and exceed the 0.8 A cm -2 U.S. Department of Energy durability target by losing only 4.5 mV, which is over six times less than 30 mV. Finally, the interactions between HOPI and SO 3 - groups with a PtCo/C catalyst are also elucidated here at a fundamental level.

25 ENERGY STORAGE↗
DOE OSTI2023

Observation of Weak Counterion Size Dependence of Thermoelectric Transport in Ion Exchange Doped Conducting Polymers Across a Wide Range of Conductivities

Conducting polymers are of interest for a broad range of applications from bioelectronics to thermoelectrics. The factors that govern their complex charge transport physics include the structural disorder present in these highly doped polymer films and the Coulombic interactions between the electronic charge carriers and the dopant counterions. Previous studies have shown that at low doping levels carriers are strongly trapped in the vicinity of the counterions, while at high doping levels charge transport is not limited by Coulombic trapping, which manifests itself in the conductivity being independent of the size of the dopant counterion. Here a recently developed ion exchange doping method is used to investigate the ion size dependence of a semicrystalline polythiophene–based model system across a wide range of conductivities. It is found that the regime in which the charge and thermoelectric transport is not or only weakly dependent on ion size, extends to surprisingly low conductivities. This surprising observation is explained by a heterogeneous doping that involves doping of the amorphous domains to high doping levels first before doping of the ordered, crystalline domains occurs. The study provides new insights into how the thermoelectric physics of conducting polymers evolves as a function of doping level.

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

Tri‐Metallic Catalyst for Oxygen Evolution Reaction Enables Continuous Operation of Anion Exchange Membrane Electrolyzer at 1A cm −2 for Hundreds of Hours

Abstract Although numerous efforts are made to synthesize active electrocatalysts for green hydrogen production; catalyst stability, and facile synthesis to scale up the production are still challenging. Herein, the production of novel non‐PGM catalysts for the oxygen reduction reaction (OER) in an alkaline aqueous medium is reported, which is based on the synthesis of a trimetallic metal–organic framework (MOF) precursors. Fine‐tuning of the composition of the metal centers (Ni, Co, and Fe) shows a great effect on OER activity after the MOF undergoes dynamic chemical and structural transformations under OER conditions. In situ characterization reveals the origin of OER activity enhancement as metals’ oxidation state increases, inducing compressive mechanical strain on metal centers, enhancing the electronic conductivity through the formation of oxygen vacancies, and stronger metal–oxygen covalency. Catalysts are used in membrane electrode assembly (MEA) setup within an industrial full‐cell anion exchange membrane electrolyzer (AEMEC), showing a stable performance for 550 h without noticeable decay at 750 and 1000 mA cm −2 industrial level current densities.

Chemistry↗
DOE OSTI2024

Regulating the Third Metal to Design and Engineer Multilayered NiFeM (M: Co, Mn, and Cu) Nanofoam Anode Catalysts for Anion-Exchange Membrane Water Electrolyzers

In this study, alkaline anion-exchange membrane water electrolyzers (AEMWEs) for green hydrogen production have received intensive attention due to their feasibility of using earth-abundant platinum group metal (PGM)-free catalysts. Herein, the third metal is incorporated into NiFe-based catalysts to regulate their electronic structures and morphologies, aiming to achieve sufficient oxygen evolution reaction (OER) activity and performance in AEMWEs. The ternary NiFeM (M: Cu, Co, or Mn) catalysts are featured with multiple layered structures and nanofoam network morphologies, consisting of highly OER-active amorphous Ni-rich oxide shells and electrically conductive metallic alloy cores. The physical and electronic perturbations to the NiFe induced by a third element lead to a fine-tuning of the redox ability of the metal sites at the reaction centers, which breaks the scaling relationship between OH* and O* intermediates at the reaction centers. Thus, the unique structural configuration and electronic regulation simultaneously benefit catalytic activity and performance improvements. These NiFeM nanofoam catalysts demonstrated promising anode performance in actual AEMWEs, comparable to the IrO 2 reference, especially at high current densities. Notably, using various electrolytes (e.g., KOH solution or pure water) for AEMWEs exhibited a different performance trend among studied NiFeM catalysts, likely due to dynamic changes of catalysts under various OER environments.

25 ENERGY STORAGE↗
DOE OSTI2020

NaGaS 2 : An Elusive Layered Compound with Dynamic Water Absorption and Wide‐Ranging Ion‐Exchange Properties

Abstract Most ternary sulfides belonging to the MGaS 2 structure‐type have been known for many years and are well‐characterized. Surprisingly, there have been no reports of the NaGaS 2 composition, which contains Na, a monovalent cation slightly larger in size than Li, found in LiGaS 2 , a compound known for its non‐linear optical properties. Now it is demonstrated for the first time that the unique reversible water absorption in NaGaS 2 has resulted in its absence from previous reports owing to difficulties encountered when characterizing this compound by SC XRD. The layered structure of this compound coupled with uniquely easy migration of water molecules between the layers allows for ion exchange with 3d and 5f metal cations. Some cations, for example, Ni 2+ , facilitate exfoliation of the layers, providing a facile synthetic route to a new class of 2D chalcogenide materials and furthermore demonstrating that NaGaS 2 can readily uptake uranyl species from aqueous solutions.

Klepov, Vladislav V.↗
DOE OSTI2023

Direct Insertion Polymerization of Ionic Monomers: Rapid Production of Anion Exchange Membranes

Abstract The limited number of methods to directly polymerize ionic monomers currently hinders rapid diversification and production of ionic polymeric materials, namely anion exchange membranes (AEMs) which are essential components in emerging alkaline fuel cell and electrolyzer technologies. Herein, we report a direct coordination‐insertion polymerization of cationic monomers, providing the first direct synthesis of aliphatic polymers with high ion incorporations and allowing facile access to a broad range of materials. We demonstrate the utility of this method by rapidly generating a library of solution processable ionic polymers for use as AEMs. We investigate these materials to study the influence of cation identity on hydroxide conductivity and stability. We found that AEMs with piperidinium cations exhibited the highest performance, with high alkaline stability, hydroxide conductivity of 87 mS cm −1 at 80 °C, and a peak power density of 730 mW cm −2 when integrated into a fuel cell device.

Hsu, Jesse H.↗
DOE OSTI2023

Direct Insertion Polymerization of Ionic Monomers: Rapid Production of Anion Exchange Membranes

The limited number of methods to directly polymerize ionic monomers currently hinders rapid diversification and production of ionic polymeric materials, namely anion exchange membranes (AEMs) which are essential components in emerging alkaline fuel cell and electrolyzer technologies. Herein, we report a direct coordination-insertion polymerization of cationic monomers, providing the first direct synthesis of aliphatic polymers with high ion incorporations and allowing facile access to a broad range of materials. We demonstrate the utility of this method by rapidly generating a library of solution processable ionic polymers for use as AEMs. We investigate these materials to study the influence of cation identity on hydroxide conductivity and stability. Furthermore, we found that AEMs with piperidinium cations exhibited the highest performance, with high alkaline stability, hydroxide conductivity of 87 mS cm –1 at 80 °C, and a peak power density of 730 mW cm –2 when integrated into a fuel cell device.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗