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DOE OSTI2021

A Lamination Model for Pressure-Assisted Sintering of Multilayered Porous Structures

This work describes a lamination model for pressure-assisted sintering of thin, multilayered, and porous structures based on the linear viscous constitutive theory of sintering and the classical laminated plate theory of continuum mechanics. A constant out-of-plane normal stress is assumed in the constitutive relation. The lamination relations between the force/moment resultants and the strain/curvature rates are presented. Numerical simulations were performed for a symmetric tri-layer laminate consisting of a 10% gadolinia doped ceria (Ce 0.9 Gd 0.1 O 1.95-δ ) composite structure, where porous layers were adhered to the top and bottom of a denser layer under uniaxially-applied pressures and the sinter forging conditions. The numerical results show that, compared with free sintering, the applied pressure can significantly reduce the sintering time required to achieve given layer thicknesses and porosities. Unlike free sintering, which results in a monotonic decrease of the laminate in-plane dimension, pressure-assisted sintering may produce an in-plane dimension increase or decrease, depending on the applied pressure and sintering time. Finally, the individual layers in the laminate exhibit different stress characteristics under pressure-assisted sintering.

42 ENGINEERING↗

DOE OSTI2026

Data Associated with "Identifying Suitable Front Contacts for High-Efficiency Cd(Se,Te) Solar Cells on Space-Qualified Cover Glass"

This is data associated with the publication " Identifying Suitable Front Contacts for High-Efficiency Cd(Se,Te) Solar Cells on Space-Qualified Cover Glass " by Aesha P. Patel, Ryan Muzzio, Matthew R. Young, Robert Morrissey, Suresh Chaulagain, B. Edward Sartor, Prabodika N. Kaluarachchi, Christian Velez, Joshua A. Brown, Joel N. Duenow, Stephen Glynn, Michael J. Heben, Zhaoning Song, Nikolas J. Podraza, Adam B. Phillips, Randy J. Ellingson, Matthew O. Reese. All data associated with each figure in the manuscript and supplementary should be available in this dataset. A readme file is also included to provide some guidance. Abstract: Deployment of photovoltaics in space requires devices that combine high-efficiency, low areal mass, and resilience to harsh environments. Historically, high-efficiency multijunction III–V materials have dominated space power systems; however, their high cost and limited manufacturing throughput motivate the exploration of scalable alternatives. While CdTe-based thin-film photovoltaics offer an attractive option, their performance on non-conventional substrates can suffer from front-contact instability under higher-temperature processing. Here, the role of front-contact chemistry in limiting cell performance is investigated using CdTe-based devices fabricated on 150 μm thick Ceria-doped space-qualified 0214 Corning glass. A matrix of four transparent conducting oxides (TCOs: CTO, AZO, ITO, IZO) combined with two n-type emitters (MZO, IGO) reveals chemical stability at the front interface—rather than absorber composition alone—governs recombination losses, voltage deficits, and device reproducibility. Chemically stable front-contact combinations suppress elemental diffusion and interfacial degradation, resulting in significantly improved carrier lifetimes and junction quality. These insights are validated through record-certified Cd(Se,Te) cell efficiencies of 18.4% under AM1.5G and 16.2% under AM0 illumination on ultra-thin glass. Beyond CdTe, this work provides a general framework for the rational selection of TCO/emitter interfaces in superstrate thin-film photovoltaics, including emerging technologies like metal halide perovskites, while enabling high-efficiency, lightweight photovoltaics for space applications.

14 SOLAR ENERGY↗

DOE OSTI2020

Mixed metal oxide extrudate catalyst

Methods of making a Ce0.6Zr0.4O2 supported NiMg catalyst extrudate are provided. In some aspects, the methods include preparing a ceria-zirconia solution comprising Ce(NO3)3.6H2O, ZrO(NO3)2xH2O, and water; forming a precipitate; drying and calcining the precipitate to produce a Ce0.6Zr0.4O2; adding a nickel-magnesium solution to the Ce0.6Zr0.4O2 to produce the NiMg/Ce0.6Zr0.4O2; and drying and calcining a wet extrudate of the NiMg/Ce0.6Zr0.4O2 to produce the Ce0.6Zr0.4O2 supported NiMg catalyst extrudate. Ce0.6Zr0.4O2 supported NiMg catalyst extrudates made by the methods are also provided.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Three-dimensional architectured anode, a direct carbon fuel cell including the three-dimensional architectured anode, and related methods

A method of fabricating a three-dimensional (3D) architectured anode. The method comprises immersing a fabric textile in a precursor solution, the precursor solution comprising a nickel salt and gadolinium doped ceria (GDC). The nickel salt and GDC are absorbed to the fabric textile. The fabric textile comprising the absorbed nickel salt and GDC is removed from the precursor solution and calcined to form a 3D architectured anode comprising nickel oxide and GDC. Additional methods and a direct carbon fuel cell including the 3D architectured anode are also disclosed.

Ding, Dong↗

DOE OSTI2022

Unconventional Highly Active and Stable Oxygen Reduction Catalysts Informed by Computational Design Strategies

As conventional strategies of engineering new MIEC materials for SOFCs over the past few decades would have eliminated a material like BFCZ75 from contention, this work suggests there is a need to re-think existing design criteria and develop and understand new rational materials design strategies that challenge conventional wisdom and chemical intuition. The ultimate goal of cathode design of SOFCs is to achieve a balance among electrical conductivity, ionic conductivity, oxygen exchange activity and long-term stability. Instead of searching for a replacement for unstable MIEC like LSCF, which works well in a ceria based composite electrode, some stable composites contain a highly conductive material mixing with a less conductive but highly ORR active and stable MIEC such as BFCZ75 or even triple-phase composites could be an alternative way to advance the current SOFC technology. (This work is published in May 2022 issue of Advanced Energy Materials. https://doi.org/10.1002/aenm.202201203 -->)<br>

Liu, Jian↗

DOE OSTI2023

Chemical looping conversion of CH4/CO2 to syngas on 5wt.%Ni@Ce0.6Zr0.4O2 catalyst: Impact of dynamic accumulation of surface carbon and oxygen vacancies

Syngas, a combination of carbon monoxide (CO) and hydrogen (H2), is a precursor to many chemicals and fuels, contributing to the billion-dollar global hydrocarbon industry. Chemical looping reforming (CLR) of the greenhouse gases methane (CH4) and carbon dioxide (CO2) allows for energy-efficient production of syngas. 5wt.% nickel (Ni) on ceria-zirconia (5wt%Ni@Ce0.6Zr0.4O2) mixed metal oxide catalyst was investigated here to explore pathways for enhanced syngas production on sustainable earth-abundant transition metal supported catalysts. The role of reduction-oxidation (redox) state of the catalyst, and carbon formation on the catalyst surface during chemical looping is explored to drive superior reaction kinetics, conversions, selectivity, and syngas ratios (H2/CO). The bulk and surface structure of the catalyst, along with carbon deposition features were characterized by electron microscopy, X-Ray diffraction, and ex situ Raman spectroscopy. The dynamic evolution of catalysts under CLR reaction conditions and the intrinsic reaction mechanisms were probed with in situ Raman spectroscopy, in situ Fourier transform spectroscopy, dynamic oxygen storage capacity (DOSC), and the Temporal Analysis of Products (TAP) reactor studies. Intrinsic kinetics of syngas production via CLR was correlated to the redox state of catalyst and the participation of nickel-catalyzed multiwalled carbon nanotube (CNT) growth, allowing enhanced CLR reaction performance.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2025

Nickel-incorporated Oxide Composites for Fiber-Optic Based Gas Sensing

Numerous high-value applications within the energy sector involve environmental conditions that are incompatible with traditional sensor technology due to degradation of electrical interconnects, packaging, or the sensors themselves. These can include chemically harsh conditions, high temperature operation, or the presence of electromagnetic interference due to high voltage. The fiber optic platform, constructed of robust, electrically insulating glass or single crystal oxides, offers a versatile and often low cost per node solution to this problem, especially with the integration of distributed sensing techniques such as optical time-domain and frequency-domain reflectometry (OTDR, OFDR). A major challenge of gas and chemical sensing on the optical fiber platform is the fabrication of robust and stable sensing materials that interact quickly and reversibly to the presence of the target analytes. In this work, we discuss the utilization of nickel-incorporated oxides on evanescent-field optical fiber sensors for gas sensing under harsh conditions relevant to multiple energy infrastructure applications. This paper will discuss a Ni/GDC (Ni / Gd-doped ceria) based sensing layer targeting conditions relevant for high-temperature (up to at least 800oC) hydrogen sensing applications (e.g., for operation within a solid oxide fuel cell or electrolyzer). The impact of hydrogen at elevated temperatures on the optical properties of Ni/GDC will be shown and the material mechanisms for the optical response will be discussed.

gas sensors↗

DOE OSTI2022

Low temperature dry reforming of methane using Ru-Ni-Mg/ceria-zirconia catalysts: Effect of Ru loading and reduction temperature

Dry reforming catalysts, especially those with activity at moderate temperatures, have been intensely investigated to enhance the conversion of biogas. Here, Ru is evaluated as a promoter for Ni-Mg based catalysts. Catalysts based on 1.4 wt%Ni-1.0 wt%Mg-Ce 0.6 Zr 0.4 O 2 with Ru (0.02–0.32 wt%) were prepared using incipient wetness. The reducibility of the catalysts and conversions increased with increasing Ru content. Increases in conversions with increasing Ru loading was attributed to the additional active sites and synergistic effect between Ru and Ni, which weakened Ni-Mg interactions. Samples showed dry reforming activity at low temperatures (450–510 °C). Reaction rates and activation energies of higher loading Ru samples (1.4 wt%Ni-1.0 wt%Mg/Ce 0.6 Zr 0.4 O 2 with 0.16 and 0.32 wt%Ru) decreased when the reduction temperature was raised from 300 to 400 °C. A 20 h TOS study showed stable catalytic activity with minimal coke deposition. Furthermore, the results suggest that Ru is an alternative to Pt in promoting low temperature dry reforming of methane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

High‐Performance and Durable Fuel Cells using Co/Sr‐Free Fluorite‐Based Mixed Conducting (Pr,Ce)O 2‐δ Cathode

Abstract A major challenge to overcome in demonstrating solid oxide fuel cells (SOFCs) to be suitable as efficient and environmentally friendly energy conversion devices capable of addressing pressing clean energy and environmental needs is to surmount chemical and thermo‐mechanical instabilities in their operational phase. To date, perovskite‐based mixed conducting cathodes, which include inherent Co and Sr elements for enhanced reactivity and conductivity, have been intensively studied. These Co/Sr‐based oxides, however, exhibit severe thermochemical expansion and suffer from Sr surface segregation, ultimately degrading the electrode performance. Here, high‐performance and durable SOFCs are demonstrated by employing a Co/Sr‐free fluorite‐based mixed conducting (Pr,Ce)O 2‐δ (PCO) cathode eminently compatible with fluorite‐based solid electrolytes. The nanocolumnar PCO electrode developed in this study provides not only a remarkable low level of electrode resistance (e.g., ≈0.05 Ω cm 2 at 600 °C) but also exceptional long‐term stability (e.g., a degradation rate 15 times slower compared to the state‐of‐the‐art La 0.6 Sr 0.4 CoO 3‐δ perovskite). The competitive peak power densities of an anode‐supported single cell with the PCO cathode are also successively achieved, recording a value of 0.92 W cm −2 at 600 °C. These findings herald the development of new Co/Sr‐free electrodes for SOFCs at intermediate temperatures.

30 DIRECT ENERGY CONVERSION↗

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↗

DOE OSTI2020

Methane combustion over Ni/Ce x Zr 1-x O 2 catalysts: impact of ceria/zirconia ratio

In this work, a series of Ce x Zr 1–x O 2 (x=1, 0.83, 0.17, 0) supports and 2 wt.% Ni/Ce x Zr 1–x O 2 catalysts were synthesized and evaluated for CH 4 oxidation. The Ce x Zr 1–x O 2 supports showed moderate activity (T 50 =519-638°C) with CO by-product formation. Additionally, nickel incorporation onto Ce x Zr 1–x O 2 lowered the T 50 to 438–477°C and eliminated the formation of CO. The results indicated that moderate Zr doping improved the support oxygen storage capacity (OSC) and reducibility of the catalyst at low temperatures (H 2 -TPR) leading to an enhanced CH 4 combustion turnover frequency: Ni/ZrO 2 <Ni/Ce 0.17 Zr 0.83 O 2 <Ni/CeO 2 <Ni/Ce 0.83 Zr 0.17 O 2 . The apparent activation energies of Ni/Ce x Zr 1–x O 2 catalysts (87-92 kJ/mol) were much lower than the ones of Ce x Zr 1–x O 2 supports and Ni/quartz sand (111-120 kJ/mol) indicating that CH 4 oxidation is facilitated when Ni is deposited on Ce x Zr 1–x O 2 . Moreover, stability tests with H 2 O and CO 2 showed that Zr doping can improve the catalyst stability, while H 2 O had a stronger reversible inhibition effect than CO 2 for CH 4 combustion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Enhancing NO Reduction by CO Over NiO/CeO 2 Catalyst by Optimizing the Metal Oxide–Support Interaction

Noble metal catalysts are widely used in three-way catalysts (TWCs) due to their high efficiency, but their scarcity and high cost drive the need for effective, low-cost alternatives. Here, in this work, a series of NiO/CeO 2 catalysts were engineered by modulating the OH content and crystallite size of the CeO 2 support. This approach yielded Ni species ranging from isolated single atoms to small clusters and larger aggregates, with varied NiO/CeO 2 interaction strengths. Evaluation of their performance in NO reduction by CO, CO oxidation, and the water–gas shift reaction revealed that the NiO/CeO 2 -300 catalyst, featuring small CeO 2 crystallites and highly dispersed NiO clusters, delivered superior activity for NO reduction and CO oxidation. It was demonstrated that small NiO clusters, due to their efficient CO adsorption and activation, were more active than Ni single atoms. Furthermore, the presence of water was found to influence the catalyst stability, with NiO clusters less stable than single atoms likely due to the hydroxylation effect leading to the formation of Ni(OH) 2 . Oxygen storage capacity measurements revealed that performance was governed by a combination of CeO 2 crystallite size and the abundance of NiO/CeO 2 interfaces. These findings demonstrated that the catalytic performance of Ni/CeO 2 systems could be maximized by optimizing the Ni nanostructure and its interaction with CeO 2 support, positioning them as a promising, multifunctional nonprecious alternative for three-way catalysis application.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Effect of redox promoters (CeO x and CuO x ) and surface sulfates on the selective catalytic reduction (SCR) of NO with NH 3 by supported V 2 O 5 -WO 3 /TiO 2 catalysts

A series of TiO 2 -supported MO x catalysts (M=V, W, Ce, Cu and S) were investigated for their SCR activity. In situ Raman spectroscopy indicated that the supported MO x phases were completely dispersed as surface sites on the TiO 2 support. In situ IR revealed that surface VO x , WO x and SO x sites anchored at both CeO x /CuO x and TiO 2 sites. The number of surface Lewis acid sites decreased with the addition of basic (CeO x /CuO x ) and acidic (VO x /WO x ) sites in all catalysts, and acidic SO x in the unpromoted and Ce-promoted catalysts. The surface VO x , WO x and SO x sites introduced surface Brønsted acid sites. The redox promoters increased the NO conversion, but SO x impregnation inhibited their effect due to acid (SO x )-base (CeO x /CuO x ) interactions. Finally, the SCR reaction was shown to efficiently proceed via either surface NH 3 * or NH 4 +* species, resolving the long-standing dispute on the involvement of these species in the SCR reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Controlling the Reconstruction of Ni/CeO 2 Catalyst during Reduction for Enhanced CO Methanation

Reductive pretreatment is an important step for activating supported metal catalysts but has received little attention. In this study, reconstruction of the supported nickel catalyst was found to be sensitive to pretreatment conditions. In contrast to the traditional activation procedure in hydrogen, activating the catalyst in syngas created supported Ni nanoparticles with a polycrystalline structure containing an abundance of grain boundaries. The unique post-activation catalyst structure offered enhanced CO adsorption and an improved CO methanation rate. The current strategy to tune the catalyst structure via manipulating the activation conditions can potentially guide the rational design of other supported metal catalysts.

42 ENGINEERING↗

DOE OSTI2022

Dependency of CO 2 methanation on the strong metal-support interaction for supported Ni/CeO 2 catalysts

The strong metal-support interaction (SMSI) for supported Ni/CeO 2 catalysts with different CeO 2 nanomorphologies was systematically explored. The degree of encapsulation of Ni particles originating from the SMSI effect was found to follow the trend of Ni/CeO 2 -(1 1 1) > Ni/CeO 2 -(1 0 0) > Ni/CeO 2 -(110 + 100), which parallels the CO 2 hydrogenation activity. Quasi in situ XPS reveals the presence of Ce 3+ sites in accordance with the formation of an amorphous surface CeOx layer encapsulating the Ni nanoparticles. In situ DRIFTS indicates the reaction pathway and rate-determining step are dependent on the degree of the SMSI effect, leading to distinct selectivities towards CH 4 , especially at a high weight hourly space velocity (WHSV). Finally, these findings present a fundamental strategy about tailoring catalytic performance through support facet dependent susceptibility of SMSI phenomena.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Adsorption and activation of CO 2 on Pt/CeOx/TiO 2 (110): Role of the Pt-CeO x interface

The adsorption and dissociation of CO 2 on TiO 2 (110), CeO x /TiO 2 (110) and Pt/CeO x /TiO 2 (110) surfaces has been examined using Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS). The substrates under study exhibited different degrees of complexity which were tested for the binding of the adsorbate and the cleavage of C-O bonds. The surfaces were prepared by depositing CeO x (0.1 ML) onto TiO 2 (110) to form a mixed oxide support, onto which Pt nanoparticles (0.2 ML) were deposited. This configuration yields a complex set of interfaces between metal and oxides and we have systematically titrated the active role of each component (Pt 4f, Ce 3d and Ti 2p regions) and the arising surface intermediates (C 1s and O 1s regions). CO 2 barely bonds to stoichiometric TiO 2 (110). It heals oxygen vacancies of this oxide surface (CO 2,gas → CO gas + O a ) and does not form stable carbonates. A stable carbonate was seen upon adsorption of CO 2 on CeO x /TiO 2 (110) and on this type of substrate the adsorbate also removed O vacancies leading to the oxidation of Ti 3+ and Ce 3+ sites. Pt nanoparticles dispersed on CeO x /TiO 2 (110) were highly effective for the binding and dissociation of CO 2 , with the formation of CO 3 , CO, C and CH x species on the Pt/CeO x /TiO 2 (110) system. The results of theoretical calculations based on density-functional theory (DFT) show that Pt/CeOx/TiO2(110) binds CO2 much stronger than surfaces of bulk platinum {(111), (100), (110)} or other late transition metals. On a Pt-CeO x interface, the molecule adsorbs with a bent configuration (~ 130° O-C-O bond angle) and with a substantial elongation (~ 0.1 Å) of the C-O bonds, facilitating its transformation into high value chemicals.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Hydroxyls on CeO 2 Support Promoting CuO/CeO 2 Catalyst for Efficient CO Oxidation and NO Reduction by CO

Transition metal catalysts, such as copper oxide, are more attractive alternatives to noble metal catalysts for emission control due to their higher abundance, lower cost, and excellent catalytic activity. Here, in this study, we report the preparation and application of a novel CuO/CeO 2 catalyst using a hydroxyl-rich Ce(OH) x support for CO oxidation and NO reduction by CO. Compared to the catalyst prepared from a regular CeO 2 support, the new CuO/CeO 2 catalyst prepared from the OH-rich Ce(OH) x (CuO/CeO 2 –OH) showed significantly higher catalytic activity under different testing conditions. The effect of OH species in the CeO 2 support on the catalytic performance and physicochemical properties of the CuO/CeO 2 catalyst was characterized in detail. It is demonstrated that the abundant OH species enhanced the CuO x dispersion on CeO 2 , increased the CuO x –CeO 2 interfaces and surface defects, promoted the oxygen activation and mobility, and boosted the NO adsorption and dissociation on CuO/CeO 2 –OH, thus contributing to its superior catalytic activity for both CO oxidation and NO reduction by CO. These results suggest that the OH-rich Ce(OH) x is a superior support for the preparation of highly efficient metal catalysts for different applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Stable and Catalytically Active Shape-Engineered Cerium Oxide Nanorods by Controlled Doping of Aluminum Cations

Shape-engineered nanocrystals (SENs) promise a better selectivity and a higher activity in catalytic reactions than the corresponding non-shape-engineered ones because of their larger specific surface areas and desirable crystal facets. However, often, it is challenging to apply SENs in practical catalytic applications at high reaction temperatures, where SENs deforms into more stable, less active nanoparticles. In this paper, we show that atomic layer deposition (ALD) of Al 2 O 3 at 200 °C can controllably dope Al cations into the shape-engineered CeO 2 nanorods (NRs) to not only increase their shape transition temperature from 400 °C to beyond 700 °C but also greatly increase their specific reversible oxygen storage capacity (srOSC). Furthermore, the substituted Al3+ ions impede the surface diffusion of Ce ions and therefore improve the thermal stability of CeO 2 NRs. These Al3+ dopants form -Al–O–Ce–O– clusters, which are new Ce species and can be reversibly reduced and oxidized at 500–700 °C. This low-temperature chemical doping method decouples the synthesis process of SENs from the doping process and maintains the shape of the SENs during the activation of dopants. This concept could be adopted to enable the applications of other SENs in challenging high-temperature environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗