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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Formation of Oxides in the Interior of Friction Stir Welds

In friction stir welding (FSWing) the actual solid state joining takes place between the faying surfaces which form the weld seam. Thus the seam trace is often investigated for clues when the strength of the weld is reduced. Aluminum and its alloys are known to form a native, protective oxide on the surface. If these native surface oxides are not sufficiently broken up during the FSW process, they are reported to remain in the FSW interior and weaken the bond strength. This type of weld defect has been referred to as a lazy "S", lazy "Z", joint line defect, kissing bond, or residual oxide defect. Usually these defects are mitigated by modification of the process parameters, such as increased tool rotation rate, which causes a finer breakup of the native oxide particles. This study proposes that there may be an alternative mechanism for formation of oxides found within the weld nugget. As the oxidation rate increases at elevated temperatures above 400ºC, it may be possible for enhanced oxidation to occur on the interior surfaces during the FSW process from entrained air entering the seam gap. Normally, FSWs of aluminum alloys are made without a purge gas and it is unknown how process parameters and initial fit up could affect a potential air path into the interior during the processing. In addition, variations in FSW parameters, such as the tool rotation, are known to have a strong influence on the FSW temperature which may affect the oxidation rate if internal surfaces are exposed to entrained air. A series of FSWs were made in 3 different thickness panels of AA2219 (0.95, 1.27 and 1.56 cm) at 2 different weld pitches. As the thickness of the panels increased, there was an increased tendency for a gap to form in advance of the weld tool. If sufficient air is able to enter the workpiece gap prior to consolidation, the weld temperature can increase the oxidation rate on the interior surfaces. These oxidation rates would also be accelerated in areas of localized liquation. Metallographs from the weld panels showed indications of liquation at the grain boundaries. In FSWs of thicker panels, these regions of liquation were found to be heavily oxidized. The quality of the FSWs was evaluated from tensile testing at room temperature. As the panel thickness increased, a slight decrease in tensile strength was observed which was attributed to the presence of oxides. No oxide formation was observed in the thinner workpieces, although there were indications of localized liquation at the grain boundaries. Results from this study will assist in a better understand of the mechanisms of oxide formation in FSW interiors and provide methodology for minimizing their occurrence.

Schneider, Judy↗
DOE OSTI2025

Tunable Crosslinked Ether Polymer Network Electrolytes for High‐Performance All‐Solid‐State Sodium Batteries

All-solid-state batteries (ASSBs) are critical for achieving high energy density and enhanced safety. Solid polymer electrolytes (SPEs) offer key advantages over other electrolytes, including improved safety, flexibility, and interfacial contact. Among the SPEs, ether-based polymers are widely studied due to their ease of processing and high ionic conductivity (σi) in the amorphous state. In this work, the introduction of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) into an SPE matrix composed of poly(ethylene glycol) diacrylate (PEGDA), poly(ethylene glycol) (PEG2k), and sodium bis(fluorosulfonyl)imide (NaFSI) salt is investigated to facilitate the formation of amorphous, high σ i SPEs through end-group engineering and polymer ratio optimization. PEGMEMA enhances structural integrity via crosslinking with PEGDA through its methacrylate group, while its methyl end group aids ion conduction. A 2:1:7 ratio of PEGDA:PEGMEMA:PEG2k exhibits a σi of 1.16 x 10 -4 S cm -1 and oxidative stability up to 4.4 V at 60 °C. A solid-state cell incorporating this SPE, a Na 2/3 Ni 1/3 Mn 2/3 O 2 (NM12) cathode, and a sodium-metal anode demonstrates excellent cycling stability, retaining over 80 % of its initial capacity for 150 cycles at 60 °C. The findings highlight the potential of end-group engineering in improving the electrochemical performance of SPEs.

25 ENERGY STORAGE↗
DOE OSTI2022

Enhanced Catalytic Performance of a Ce/V Oxo Cluster through Confinement in Mesoporous SBA-15

To increase catalytic efficiency, mesoporous supports have been widely applied to immobilize well-defined metal oxide clusters due to their ability to stabilize highly dispersed clusters. Here, for this study, a redox-active heterometallic Ce 12 V 6 -oxo cluster (CeV) was first presynthesized and then incorporated into mesoporous silica, SBA-15, via a straightforward impregnation method. Scanning transmission electron microscopy (STEM) and Fourier transform infrared spectroscopy (FTIR), in concert with scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), verified the successful introduction of the CeV cluster inside the pore of SBA-15. The 51 V magic angle spinning solid-state nuclear magnetic resonance ( 51 V MAS NMR) spectroscopy and differential pair distribution function (dPDF) analysis confirmed the structural integrity of the CeV cluster inside the SBA-15. The composite was then benchmarked for liquid-phase oxidation of 2-chloroethyl ethyl sulfide (CEES) under mild conditions and gas-phase oxidative dehydrogenation (ODH) of propane under high temperatures (up to 550 °C). The catalytic reactivity results demonstrated 8- and 14-fold increase in turnover frequency (TOF) values of the composite (CeV@10SBA-2) than the bulk CeV cluster under the same conditions for CEES oxidation and ODH, respectively. These results highlight the improved reactivity of the catalytically active CeV cluster as attributed to the higher dispersion of the discrete cluster upon immobilization within the SBA-15 support.

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

Does H 2 Temperature–Programmed Reduction Always Probe Solid–State Redox Chemistry? The Case of Pt/CeO 2

Redox reactions on the surface of transition metal oxides are of broad interest in thermo, photo, and electrocatalysis. H 2 temperature-programmed reduction (H 2 -TPR) is commonly used to probe oxide reducibility by measuring the rate of H 2 consumption during temperature ramps, assuming that this rate is controlled by oxide reduction. However, oxide reduction involves several elementary steps, such as H 2 dissociation and H-spillover, before surface reduction and H 2 O formation occur. In this study, we evaluated the kinetics of H 2 consumption over CeO 2 and Pt/CeO 2 with varying Pt loadings and structures to identify the elementary steps probed by H 2 -TPR. Literature often attributes changes in H 2 -TPR characteristics with Pt addition to increased CeO 2 reducibility. However, our analysis revealed that the H 2 consumption rate is measurement of the rate of H-spillover at Pt-CeO 2 interfaces and is determined by the concentration of Pt species on Pt nanoclusters that dissociate H 2 . Furthermore, lower temperature H 2 consumption observed with Pt addition does not indicate higher CeO 2 reducibility. Measurements on samples with mixtures of Pt single-atoms and nanoclusters demonstrated that H 2 -TPR can effectively quantify dilute Pt nanocluster concentrations, suggesting caution in directly linking H 2 -TPR characteristics to oxide reducibility while highlighting alternative material insights that can be gleaned.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1990

Solid-state thin-film memistor for electronic neural networks

This paper reports on a tungsten-oxide-based, nonvolatile, electrically reprogrammable, variable resistance device as an analog synaptic memory connection for electronic neural networks. A voltage controlled, reversible injection of H(+) ions in electrochromic thin films of WO3 is utilized to modulate its resistance. A hygroscopic thin film of Cr2O3 is the source of H(+) ions. The resistance of the device can be tailored and stabilized over a wide dynamic range (about 4 orders of magnitude), and the programming speed is modulated by the control voltage. The suitability of such a device in terms of its response speed, reversibility, stability, and cyclability for its use in electronic neural networks is discussed.

Thakoor, S.↗
DOE OSTI2026

All‐Solid‐State Batteries With Mechanically Stable Interfaces Consisting of a Zero‐Strain Cation‐Disordered Rocksalt Cathode

Interface stabilization is critical to the development of working all‐solid‐state batteries. Rigid cathode/solid electrolyte interfaces often disintegrate due to anisotropic volume change of cathode‐active materials, resulting in irreversible capacity loss. Herein, we demonstrate that Li 1.211 Mo 0.467 Cr 0.3 O 2 (LMCO), a pioneering cation‐disordered rocksalt oxide (DRX) cathode that has intrinsically small volume change upon lithium intercalation, can be integrated with a thiophosphate‐based solid electrolyte for all‐solid‐state batteries. Interface stability of the all‐solid LMCO cell was investigated by electrochemical impedance spectroscopy, X‐ray micro‐computed tomography, and electron microscopy. Since LMCO was initially synthesized as a layered phase exhibiting a large volume change, interface disintegration can be observable in the early cycles. As layered LMCO phase‐transformed into DRX LMCO in subsequent cycles, reintegration of the interfaces occurs within a pressurized cell as a result of its zero‐stain behavior. Consequently, the DRX LMCO cathode maintains interface integrity, and thus electrical wiring, over an extended number of cycles, leading to improved capacity retention with small internal cell resistance.

DRX↗
DOE OSTI2022

Application of GO anchored mediator in a polymer electrolyte membrane for high-rate solid-state supercapacitors

Here, we synthesized a novel polymer electrolyte membrane by combining poly (vinylidene fluoride) (PVDF) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) with graphene oxide (GO) nanosheets and a lithium salt of tungstosilicic acid (Li 4 SiW 12 O 40 , hereafter, referred to SiWLi). The impact of the addition of GO/SiWLi on the microstructure and morphology of the membrane were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). We found that adding the GO/SiWLi to the PVDF/LiTFSI polymer electrolyte membrane significantly reduced the pore size. Furthermore, the addition of the GO/SiWLi resulted in not only an increase of the ionic conductivity from 0.87 $\times$ 10 –2 to 3.12 $\times$ 10 –2 Scm –1 but also an increase in the lithium-ion transference number from 0.52 to 0.87. The polymer electrolyte membranes with and without GO/SiWLi were utilized to fabricate solid-state supercapacitors. The supercapacitors fabricated with the membrane containing GO/SiWLi displayed 37.2% lower equivalent series resistance and 88.2% greater specific capacitance than those fabricated using the membrane without GO/SiWLi at 200mVs –1 .

42 ENGINEERING↗
DOE OSTI2024

Mechanisms and site requirements for NO and NH 3 oxidation on Cu/SSZ-13

Two series of Cu/SSZ-13 catalysts were synthesized via aqueous solution and solid-state ion exchange using SSZ-13 supports of varying Si/Al ratios. The isolated and multinuclear Cu content of these catalysts were determined by H 2 temperature programmed reduction (H 2 -TPR). Multinuclear Cu in these catalysts, including in situ Cu- dimers formed from ZCu II OH coupling and permanent CuO clusters, are active species for dry NO oxidation. NH 3 oxidation on these catalysts follows an internal SCR (i-SCR) mechanism, i.e., a portion of NH 3 is first oxidized to NO, then NO is selectively reduced by the remaining NH 3 to N 2 . NH 3 oxidation displays distinct kinetic behavior below ~300 °C and above ~400 °C. At low temperature the results indicate that NH 3 -solvated mobile Cu-ions are the active centers. CuO clusters, when present, also contribute to the low temperature activity by catalyzing NH 3 oxidation to NO. At high temperature, in situ Cu-dimers and CuO clusters catalyze NH 3 oxidation to NO, and isolated Cu-ions catalyze SCR to realize the cascade turnovers. For both NO and NH 3 oxidation, Cu-dimers balanced by framework charges of close proximity appear to be more active than Cu-dimers balanced by distant framework charges. However, the former Cu-dimers are less stable than the latter and tend to split into monomers in the presence of vicinal Brønsted acid sites. Via density functional theory (DFT) calculations, the i-SCR mechanism for low temperature NH 3 oxidation, i.e., the energetic favorability for the involvement of the NO intermediate, is justified. Furthermore, the DFT results also agree with experimental data that the formation of Cu-dimers from ZCu II OH dimerization is essential for NH 3 oxidation at high temperature.

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

Developing cathode infiltration processes for all-solid-state bilayer LLZO cells

To realize the bilayer architecture of lithium lanthanum zirconate (LLZO) for application in solid-state batteries (SSBs), the scaffold structure must be optimized, and effective cathode infiltration strategies must be established. In this study, we fabricate a modified bilayer LLZO using a sacrificial layer to enhance surface porosity, and systematically investigate various cathode infiltration techniques to fill the scaffold with oxide cathode active materials (CAM). Structural characterizations showed that the sacrificial layer significantly increased open surface porosity, enabling the surface of the scaffold to be filled with CAM. To further increase infiltration depth, applying vacuum or vibration was compared, with the full-depth infiltration achieved using a sonicator-based vibration. Full cells prepared using the modified bilayer LLZO and vibration-assisted technique demonstrated successful operation. This work demonstrates a practical and scalable approach for engineering bilayer LLZO structures and integrating oxide cathodes into porous scaffolds, offering a promising pathway toward high-performance solid-state batteries.

Bilayer↗
DOE OSTI2021

Ionic Dopant-Induced Ordering Enhances the Thermoelectric Properties of a Polythiophene-Based Block Copolymer

Conjugated polymer-based block copolymers (CP-BCPs) are an unexplored class of materials for organic thermoelectrics. In this study, the authors report on the electronic conductivity (σ) and Seebeck coefficient (α) of a newly synthesized CP-BCP, poly(3-hexylthiophene)-block-poly (oligo-oxyethylene methacrylate) (P3HT-b-POEM), upon solution co-processing with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and subsequently vapor-doping with a molecular dopant, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). It is found that the addition of the hydrophilic block POEM greatly enhances the processability of P3HT, enabling homogeneous solution-mixing with LiTFSI. Notably, interactions between P3HT-b-POEM with ionic species significantly improve molecular order and unexpectedly cause electrical oxidizing doping of P3HT block both in solution and solid-states, a phenomenon that has not been previously observed in Li-salt containing P3HT. Vapor doping of P3HT-b-POEM-LiTFSI thin films with F4TCNQ further enhances σ and yields a thermoelectric power factor PF = α 2 σ of 13.0 μW m -1 K -2 , which is more than 20 times higher than salt-free P3HT-b-POEM sample. Through modeling thermoelectric behaviors of P3HT-b-POEM with the Kang-Snyder transport model, the improvement in PF is attributed to higher electronic charge mobility originating from the enhanced molecular ordering of P3HT. The results demonstrate that solution co-processing CP-BCPs with a salt is a powerful method to control structure and performance of organic thermoelectric materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Persistent compositions of non-stoichiometric compounds with low bulk diffusivity: A theory and application to Nb3Sn superconductors

Non-stoichiometric compounds may develop a composition gradient when they are formed by reactive diffusional processes. This paper reports an interesting phenomenon that in compounds with low bulk diffusivities, which rely mainly on grain boundary diffusion for their growth, the final bulk compositions may be far from equilibrium, with a very low bulk diffusivity leading to fixed (persistent) compositions – one such example is Nb 3 Sn, a superconductor. We investigated the microchemistry at the reactive interface using atom probe tomography to clarify the diffusion reaction mechanism for this low-bulk-diffusivity case and thus propose a theory for what determines the compound composition, using Nb 3 Sn as an example for concreteness. Using certain approximations, we derive an explicit analytical equation that illustrates what factors determine its composition profile. We compare our model with the known facts of Nb 3 Sn and see good agreement. In particular, this model predicts that internal oxidation may lead to higher Sn contents than conventional, non-oxidized Nb 3 Sn. Our measurements show that this is indeed true, and that the internally-oxidized Nb 3 Sn also has higher upper critical fields, achieving up to 28.2 T at 4.2 K. We discuss the general applicability of this model to non-stoichiometric compounds with low bulk diffusivity, and propose it as a tool to help in the design and processing of such materials for compositional control.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A mechanistic study of the dopant-induced breakdown in halide perovskites using solid state energy storage devices

Doping halide perovskites (HPs) with extrinsic species, such as alkali metal ions, plays a critical, albeit often elusive role in optimising optoelectronic devices. Here, we use solid state lithium ion battery inspired devices with a polyethylene oxide-based polymer electrolyte to dope HPs controllably with lithium ions. We perform a suite of operando material analysis techniques while dynamically varying Li doping concentrations. We determine and quantify three doping regimes; a safe regime, with doping concentrations of <10 20 cm –3 (2% Li : Pb mol%) in which the HP may be modified without detrimental effect to its structure; a minor decomposition regime, in which the HP is partially transformed but remains the dominant species; and a major decomposition regime in which the perovskite is superseded by new phases. We provide a mechanistic description of the processes mediating between each stage and find evidence for metallic Pb (0) , LiBr and LiPbBr 2 as final decomposition products. Combining results from synchrotron X-ray diffraction measurements with in situ photoluminescence and optical reflection microscopy studies, we distinguish the influences of free charge carriers and intercalated lithium independently. We find that the charge density is equally as important as the geometric considerations of the dopant species and thereby provide a quantitative framework upon which the future design of doped-perovskite energy devices should be based.

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

Abstract for CRADA between NETL and Praxair Surface Technologies, Inc. (AGMT-1288)

The National Energy Technology Laboratory (NETL) and Praxair Surface Technologies (Participant) will collaborate in the design and manufacturing of new high-performance thermal barrier coatings (TBCs) for hydrogen gas turbine applications. High-throughput first-principles density functional theory (DFT) calculations will be performed to accelerate novel TBCs discovery with expanded phase field, increased temperature and erosion capabilities, low thermal conductivity, and significant toughness imparted by ferroelastic toughening for the non-transformable tetragonal oxide phase. Down-selected materials will be manufactured using solid state powder processing techniques. Testing will include isothermal aging followed by Raman and x-ray diffraction (XRD) phase analysis, indentation fracture toughness measurements, erosion testing, and thermal conductivity measurements. The collaboration will facilitate the deployment of hydrogen gas turbine technologies that are a key to the decarburization of power generation in the United States.

08 HYDROGEN↗
NASA NTRS1999

Camera-on-a-Chip

Jet Propulsion Laboratory's research on a second generation, solid-state image sensor technology has resulted in the Complementary Metal- Oxide Semiconductor Active Pixel Sensor (CMOS), establishing an alternative to the Charged Coupled Device (CCD). Photobit Corporation, the leading supplier of CMOS image sensors, has commercialized two products of their own based on this technology: the PB-100 and PB-300. These devices are cameras on a chip, combining all camera functions. CMOS "active-pixel" digital image sensors offer several advantages over CCDs, a technology used in video and still-camera applications for 30 years. The CMOS sensors draw less energy, they use the same manufacturing platform as most microprocessors and memory chips, and they allow on-chip programming of frame size, exposure, and other parameters.

Source record↗
NASA NTRS2002

Novel Molecular Architectures Developed for Improved Solid Polymer Electrolytes for Lithium Polymer Batteries

Lithium-based polymer batteries for aerospace applications need the ability to operate in temperatures ranging from -70 to 70 C. Current state-of-the-art solid polymer electrolytes (based on amorphous polyethylene oxide, PEO) have acceptable ionic conductivities (10-4 to 10-3 S/cm) only above 60 C. Higher conductivity can be achieved in the current systems by adding solvent or plasticizers to the solid polymer to improve ion transport. However, this can compromise the dimensional and thermal stability of the electrolyte, as well as compatibility with electrode materials. One of NASA Glenn Research Center's objectives in the PERS program is to develop new electrolytes having unique molecular architectures and/or novel ion transport mechanisms, leading to good ionic conductivity at room temperature and below without solvents or plasticizers.

Meador, Mary Ann B.↗
DOE OSTI2026

Fabrication, oxidation, and combustion of nanoscale magnesium diboride and tetraboride

The difficult ignition and low combustion efficiency of boron particles decrease the performance of boron-loaded, fuel-rich propellants for solid fuel ramjets and ducted rockets. One approach to solving this problem involves the use of magnesium diboride (MgB 2 ), which ignites easier than boron. Magnesium tetraboride (MgB 4 ) offers greater energy density owing to its higher boron content. However, the effect of B/Mg ratio on the ignition and combustion is unknown. Additionally, while nanoscale MgB₂ particles and quasi-2D structures are promising energetic additives, the oxidation and combustion properties of nanoscale MgB₄ have not been explored. To address these knowledge gaps, the present work included synthesis and high-energy ball milling of MgB 2 and MgB 4 powders, thermogravimetric analysis (TGA) of their oxidation, and combustion experiments with thin layers of the obtained powders. Comparison of two synthesis routes (a solid-state reaction in a tube furnace and combustion synthesis) has shown that the former is the superior method for producing magnesium borides. TGA has revealed that oxidation of both MgB 2 and MgB 4 results in a high conversion into the oxides (88–91 %), far exceeding the low conversion of boron (62.5 %). MgB 4 begins to oxidize rapidly at a much lower temperature (∼900 °C) than MgB 2 (∼1200 °C). The burning rates of milled MgB 2 and MgB 4 are about eight and five times, respectively, faster than that of submicron boron. Magnesium borides exhibit a stable, sustained boron flame, needed for high combustion efficiency, whereas physical Mg/B mixtures undergo Mg-driven "flash" combustion.

Boron↗
DOE OSTI2023

Ionic Liquid-Mediated Scanning Probe Electro-Oxidative Lithography as a Novel Tool for Engineering Functional Oxide Micro- and Nano-Architectures

Functional oxides have extensively been investigated as a promising class of materials in a broad range of innovative applications. Harnessing the novel properties of functional oxides in micro- to nano-scale applications hinges on establishing advanced fabrication and manufacturing techniques able to synthesize these materials in an accurate and reliable manner. Oxidative scanning probe lithography (o-SPL), an atomic force microscopy (AFM) technique based on anodic oxidation at the water meniscus formed at the tip/substrate contact, not only combines the advantages of both “top-down” and “bottom-up” fabrication approaches, but also offers the possibility of fabricating oxide nanomaterials with high patterning accuracy. While the use of self-assembled monolayers (SAMs) broadened the application of o-SPL, significant challenges have emerged owing to the relatively limited number of SAM/solid surface combinations that can be employed for o-SPL, which constrains the ability to control the chemistry and structure of oxides formed by o-SPL. Here, in this work, a new o-SPL technique that utilizes room-temperature ionic liquids (RTILs) as the functionalizing material to mediate the electrochemistry at AFM tip/substrate contacts is reported. The results show that the new IL-mediated o-SPL (IL-o-SPL) approach allows sub-100 nm oxide features to be patterned on a model solid surface, namely steel, with an initiation voltage as low as -2 V. Moreover, this approach enables high tunability of both the chemical state and morphology of the patterned iron oxide structures. Owing to the high chemical compatibility of ILs, which derives from the possibility of synthesizing ILs able to adsorb on a wide variety of solid surfaces, IL-o-SPL can be extended to other material surfaces and provide the opportunity to accurately tailor the chemistry, morphology, and electronic properties within nanoscale domains, thus opening new pathways to the development of novel micro- and nano-architectures for advanced integrated devices.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Does H 2 Temperature‐Programmed Reduction Always Probe Solid‐State Redox Chemistry? The Case of Pt/CeO 2

Abstract Redox reactions on the surface of transition metal oxides are of broad interest in thermo, photo, and electrocatalysis. H 2 temperature‐programmed reduction (H 2 ‐TPR) is commonly used to probe oxide reducibility by measuring the rate of H 2 consumption during temperature ramps, assuming that this rate is controlled by oxide reduction. However, oxide reduction involves several elementary steps, such as H 2 dissociation and H‐spillover, before surface reduction and H 2 O formation occur. In this study, we evaluated the kinetics of H 2 consumption over CeO 2 and Pt/CeO 2 with varying Pt loadings and structures to identify the elementary steps probed by H 2 ‐TPR. Literature often attributes changes in H 2 ‐TPR characteristics with Pt addition to increased CeO 2 reducibility. However, our analysis revealed that the H 2 consumption rate is measurement of the rate of H‐spillover at Pt‐CeO 2 interfaces and is determined by the concentration of Pt species on Pt nanoclusters that dissociate H 2 . Therefore, lower temperature H 2 consumption observed with Pt addition does not indicate higher CeO 2 reducibility. Measurements on samples with mixtures of Pt single‐atoms and nanoclusters demonstrated that H 2 ‐TPR can effectively quantify dilute Pt nanocluster concentrations, suggesting caution in directly linking H 2 ‐TPR characteristics to oxide reducibility while highlighting alternative material insights that can be gleaned.

Lee, Jaeha↗