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DOE OSTI2017

Catalysis on Singly Dispersed Rh Atoms Anchored on an Inert Support

A metal catalyst supported on an inert substrate could consist of both metal nanoparticles and singly dispersed metal atoms. Whether these singly dispersed metal atoms are active and how different their catalytic mechanism could be in contrast to a supported metal catalyst are fundamentally important for understanding catalysis on a supported metal or oxide. In this study, by taking reduction of NO with CO on singly dispersed Rh atoms anchored on an inert support SiO 2 as a probe system (Rh 1 /SiO 2 ), we demonstrated how singly dispersed metal atoms on an inert support could perform a complex multi-step catalytic cycle through a mechanism distinctly different from that for a supported metal nanoparticle with continuously packed metal sites. These singly dispersed Rh 1 atoms anchored on SiO 2 are active in reducing nitric oxide with carbon monoxide through two reaction pathways that are different from those of Rh nanoparticles. In situ IR studies show that a CO molecule and a NO molecule coadsorb on a singly dispersed Rh atom, Rh 1 anchored on SiO 2 , and couple to form an N atom to adsorb on the surface and a CO 2 molecule to desorb. The adsorbed N atom further couples with another CO molecule in the gas phase to form an intermediate -NCO on Rh 1 ; this intermediate can directly couple with an NO molecule adsorbed on the same Rh1 to form N 2 and CO 2 . In another pathway, the adsorbed N atom can couple with a coadsorbed NO on the same Rh 1 to form N 2 O; N 2 O further reacts with adsorbed CO on the same Rh 1 to form N 2 and CO 2 through a high activation barrier that can be overcome at a high temperature. Our studies show that the singly dispersed metal atoms on an inert support have great potential to perform selective transformation of chemicals. Lastly, the confirmed catalysis with a singly dispersed Rh 1 on SiO 2 through a mechanism different from a metal nanoparticle supported on the same substrate suggests the significance of taking the single-atom catalysis (SAC) into fundamental studies of catalysis of a supported metal catalyst, since metal nanoparticles and singly dispersed metal atoms likely coexist on the inert support of many supported catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

Efficient photocatalytic hydrogen generation by silica supported and platinum promoted titanium dioxide

Graphical abstract: Titanium dioxide was supported on mesoporous silica and promoted with Pt and Ru. The supported photocatalysts show high surface area and better photocatalytic activity in visible light as compared to the benchmark Degussa P25. These photocatalysts were characterized using XRD, BET-SA, and UV-DRS techniques. The surface area of supported photocatalyst was 140.6 m{sup 2}/g which is higher than Degussa P-25. Supported photocatalyst was evaluated for hydrogen evolution via water splitting reaction using ethanol as a sacrificial donor. Hydrogen yield observed is 4791.43 μmol/h/g of TiO{sub 2} and that for P-25 is 161 μmol/h/g of TiO{sub 2} under visible light irradiation. The value is 30 times higher than benchmark material Degussa P-25. This photocatalyst is also found stable up to 24 h without replenishing with sacrificial donor ethanol. - Highlights: • Semiconductor titanium dioxide has been supported on silica gel and promoted with Pt by simple wet impregnation route. • This synthesized photocatalyst is showing high surface area of 140.6 m{sup 2}/g with crystallite size in the range of 15.44 Å. • This photocatalyst is showing enhanced hydrogen yield of about 4791.43 μmol/h/g of TiO{sub 2}. • This photocatalyst is also found stable up to 24 h without replenishing with sacrificial donor ethanol. • The effect of various operating parameters on supported photocatalyst also has been studied. - Abstract: Titanium dioxide was supported on mesoporous silica and promoted with Pt and Ru. The supported photocatalysts show high surface area and better photocatalytic activity in visible light as compared to the benchmark Degussa P25. These photocatalysts were characterized using XRD, BET-SA, and UV-DRS techniques. The surface area of supported photocatalyst was 140.6 m{sup 2}/g which is higher than Degussa P-25. Supported photocatalyst was evaluated for hydrogen evolution via water splitting reaction using ethanol as a sacrificial donor. Hydrogen yield observed is 4791.43 μmol/h/g of TiO{sub 2} and that for P-25 is 161 μmol/h/g of TiO{sub 2} under visible light irradiation. The value is 30 times higher than benchmark material Degussa P-25. This photocatalyst is also found stable up to 24 h without replenishing with sacrificial donor ethanol. However silica gel/TiO{sub 2}/Ru does not show any exciting result for hydrogen generation. The effect of various operating parameters like photocatalyst loading, Illumination time and intensity of light on supported photocatalyst also has been studied.

36 MATERIALS SCIENCE↗

NASA NTRS2019

Supporting Crew Autonomy in Deep Space Exploration: Preliminary Onboard Capability Requirements and Proposed Research Questions. Technical Report of the Autonomous Crew Operations Technical Interchange Meeting

Communication delays are a critical challenge posed by long duration deep space exploration. Space missions historically have relied on an ever-present Mission Control Center (MCC) to direct operations in near real-time. As unanticipated anomalies that defeat fault detection and resolution systems do arise, the lack of real-time communication will significantly weaken what the MCC support represents: a reliable safety net for the flight crew through its deep and diverse areas of expertise and investigative resources. As a consequence, future space vehicles and habitats need to be equipped with capabilities to support the flight crew to operate with little or no ground support. Considerations must be given to vehicle and mission designs that will fortify the traditionally ground-centered safety net and forge new support systems, when communication delays exist. In August 2018, NASA’s Human Research Program, through its Human Factors and Behavioral Performance Element, convened a Technical Interchange Meeting (TIM) on Autonomous Crew Operations at NASA Ames Research Center. The goal of the meeting was to gather input from NASA centers, industry, academia, and branches of the Department of Defense (DoD) to address how intelligent technologies can be applied to augment onboard capabilities to support crew anomaly response. The TIM featured 24 presentations by 29 speakers and hosted a total of 59 attendees, including 43 from 5 NASA centers (Ames, Johnson, Langley, Marshall, and Jet Propulsion Lab) and 4 from the DoD (3 from Army Research Lab and 1 from Naval Postgraduate School), with remaining attendees from academia (e.g., UC Davis, CMU) and industry (e.g., IBM, Siemens). Discussions were centered around three themes: standards and guidelines, lessons learned in analog environments, and technologies. To help provide a framework for discussion, a concept matrix describing anomaly response processes was created prior to the TIM (Figure 1, page 6). The matrix captures the steps involved (monitoring and detection, diagnosis, solution development and evaluation, solution implementation and verification, resolution documentation) as well as the resources and capabilities required to support these steps (data, knowledge, analysis, synthesis, resource management). A wallpaper size printout of the matrix was utilized at the TIM to solicit attendee inputs along the three themes; the activity garnered 108 submissions of ideas. Overall, what emerged from TIM discussions was a picture of mismatch between crew anomaly response needs and support that can be provided by existing intelligent technologies. The needs are broad, spanning multiple steps and processes/resources, with many of which lacking support from existing technologies, such as knowledge management throughout the steps of problem solving (especially in resolution documentation) and manpower management. The solutions provided by existing intelligent technologies are specific to the steps/processes that they are designed to support and constrained to solving only problems similar to those that have occurred before. What is lacking from technologies is typically made up by humans, specifically their complex critical thinking, creative problem solving, and domain expertise. In the end, the TIM highlighted the pressing need to support responses to onboard anomalies during autonomous crew operations, particularly those that have eluded the system tests, inspection, and other assurance processes. Such anomalies can potentially threaten crew and vehicle safety, as well as significantly impact overall operations with additional workload. These fairly rare events are difficult to anticipate and prepare for, given the state-of-the-art in intelligent technologies. This is true even for anomalies that stem from “unknown knowns”—cases in which there is sufficient external information to characterize the problem but the overall pattern fails to be recognized by the problem solver, or in which the internal knowledge needed to solve a problem is held tacitly and potentially accessible by the problem solver but not articulated. It follows that the ability to tackle anomalies lies not only with the availability of relevant information and knowledge but also their accessibility in times of need. To that end, we propose research questions along the following three broad themes: • How intelligent technologies can help make relevant knowledge and information available? • How intelligent technologies can help make relevant knowledge and information accessible? • How intelligent technologies can help support the crew operating as a team in anomaly response processes?

autonomous crew operations↗

DOE OSTI2015

Surface Chemistry and Properties of Oxides as Catalyst Supports

Heterogeneous catalysis relies on metal-oxides as supports for the catalysts. Catalyst supports are an indispensable component of most heterogeneous catalysts, but the role of the support is often minimized in light of the one played by the catalytically active species it supports. The active species of supported catalysts are located on the surface of the support where their contact with liquid or gas phase reactants will be greatest. Considering that support plays a major role in distribution and stability of active species, the absorption and retention of reactive species, and in some cases in catalytic reaction, the properties and chemistry that can occur at the surface of an oxide support are important for understanding their impact on the activity of a supported catalyst. This chapter examines this rich surface chemistry and properties of oxides used as catalyst supports, and explores the influence of their interaction with the active species.

Catalyst support↗

DOE OSTI2018

Development and Elucidation of Superior Turnover Rates and Selectivity of Supported Molecular Catalysts

Abstract Supported molecular catalysts consist of nanomaterials immobilized on a solid support. Important factors that control catalyst properties (reactivity, product selectivity, and stability) include the structure and compositions of both nanomaterials and supports. This review focuses on recent studies of supported molecular catalysts with controlled activity and selectivity in our group. We will first introduce the development of previously unexplored supported molecular catalysts. We will demonstrate the controllable selectivity of catalysts based on acidified mesoporous silica, metal‐organic frameworks (MOFs), hydrogen‐activated tungsten oxides, and noble metal doped Mn x O y /Na 2 WO 4 catalyst supported on mesoporous silica. We will then discuss advanced characterization techniques under reaction conditions, which offer mechanistic explanations of activity and selectivity of supported molecular catalysts. The applications of chemical transient kinetics (CTK) analysis, ambient pressure X‐ray photoelectron spectroscopy (APXPS), and sum‐frequency generation vibrational spectroscopy (SFG‐VS) are discussed. Next, we will describe new insights into catalysis at the nanoparticle‐support interfaces, which are catalytic environments unique to supported molecular catalysts. Examples include reactions at oxide‐metal interfaces and alcohol oxidation reactions at solid–gas and solid–liquid interfaces. Lastly, we will discuss heterogenized homogeneous catalysts and heterogenized enzyme catalysts as future directions of supported molecular catalysts.

Ye, Rong↗

DOE OSTI2013

Comparative Investigation of Benzene Steam Reforming over Spinel Supported Rh and Ir Catalysts

In a combined experimental and first-principles density functional theory (DFT) study, benzene steam reforming (BSR) over MgAl 2 O 4 supported Rh and Ir catalysts was investigated. Experimentally, it has been found that both highly dispersed Rh and Ir clusters (1-2 nm) on the MgAl 2 O 4 spinel support are stable during the BSR in the temperature range of 700-850°C. Compared to the Ir/MgAl 2 O 4 catalyst, the Rh/MgAl 2 O 4 catalyst is more active with higher benzene turnover frequency and conversion. At typical steam conditions with the steam-to-carbon ratio > 12, the benzene conversion is only a weak function of the H 2 O concentration in the feed. This suggests that the initial benzene decomposition step rather than the benzene adsorption is most likely the rate-determined step in BSR over supported Rh and Ir catalysts. In order to understand the differences between the two catalysts, we followed with a comparative DFT study of initial benzene decomposition pathways over two representative model systems for each supported metal (Rh and Ir) catalysts. A periodic terrace (111) surface and an amorphous 50-atom metal cluster with a diameter of 1.0 nm were used to represent the two supported model catalysts under low and high dispersion conditions. Our DFT results show that the decreasing catalyst particle size enhances the benzene decomposition on supported Rh catalysts by lowering both C-C and C-H bond scission. The activation barriers of the C-C and the C-H bond scission decrease from 1.60 and 1.61 eV on the Rh(111) surface to 1.34 and 1.26 eV on the Rh50 cluster. For supported Ir catalysts, the decreasing particle size only affects the C-C scission. The activation barrier of the C-C scission of benzene decreases from 1.60 eV on the Ir(111) surface to 1.35 eV on the Ir50 cluster while the barriers of the C-H scission are practically the same. The experimentally measured higher BSR activity on the supported highly dispersed Rh catalyst can be rationalized by the thermodynamic limitation for the very first C-C bond scission of benzene on the small Ir50 catalyst. The C-C bond scission of benzene on the small Ir50 catalyst is highly endothermic although the barrier is competitive with the barriers of both the C-C and the C-H bond-breakings on the small Rh50 catalyst. The calculations also imply that, for the supported Rh catalysts the C-C and C-H bond scissions are competitive, independently of the Rh cluster sizes. After the initial dissociation step via either the C-C or the C-H bond scission, the C-H bond breaking seems to be more favorable rather than the C-C bond breaking on the larger Rh terrace surface. This work was financially supported by the United States Department of Energy’s Office of Biomass Program’s. Computing time was granted by a user project at the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Review of hydro-instability experiments with alternate capsule supports in indirect-drive implosions on the National Ignition Facility

Hydrodynamic instability growth of capsule support membranes (or “tents”) has been recognized as one of the major contributors to the performance degradation in high-compression plastic capsule implosions at the National Ignition Facility (NIF). The capsules were supported by tents because the nominal 10-μm diameter fill tubes were not strong enough to support capsules by themselves in indirect-drive implosions on NIF. After it was recognized that the tents had a significant impact of implosion's stability, new alternative support methods were investigated. While some of these methods completely eliminated tent, other concepts still used tents, but concentrated on mitigating their impact. The tent-less methods included “fishing pole” reinforced fill tubes, cantilevered fill tubes, and thin-wire “tetra cage” supports. In the “fishing pole” concept, a 10-μm fill tube was inserted inside 30-μm fill tube for extra support with the connection point located 300 μm away from the capsule surface. The cantilevered fill tubes were supported by 12-μm thick SiC rods, offset by up to 300 μm from the capsule surfaces. In the “tetra-cage” concept, 2.5-μm thick wires (carbon nanotube yarns) were used to support a capsule. Other concepts used “polar tents” and a “foam-shell” to mitigate the effects of the tents. The “polar tents” had significantly reduced contact area between the tents and the capsule compared to the nominal tents. In the “foam-shell” concept, a 200-μm thick, 30 mg/cc SiO 2 foam layer was used to offset the tents away from the capsule surface in an attempt to mitigate their effects. These concepts were investigated in x-ray radiography experiments and compared with perturbations from standard tent support. The measured perturbations in the “fishing pole,” cantilevered fill tube, and “tetra-cage” concepts compared favorably with (were smaller than) nominal tent perturbations and were recommended for further testing for feasibility in layered DT implosions. The “polar tents” were tested in layered DT implosions with a relatively-stable “high-foot” drive showing an improvement in neutron yield in one experiment compared to companion implosions with nominal tents. Furthermore, this article reviews and summarizes recent experiments on these alternate capsule support concepts. In addition, the concept of magnetic levitation is also discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2025

Partial PdAu nanoparticle embedding into TiO 2 support accentuates catalytic contributions from the Au/TiO 2 interface

Despite the broad catalytic relevance of metal–support interfaces, controlling their chemical nature, the interfacial contact perimeter (exposed to reactants), and consequently, their contributions to overall catalytic reactivity, remains challenging, as the nanoparticle and support characteristics are interdependent when catalysts are prepared by impregnation. Here, we decoupled both characteristics by using a raspberry-colloid-templating strategy that yields partially embedded PdAu nanoparticles within well-defined SiO 2 or TiO 2 supports, thereby increasing the metal–support interfacial contact compared to nonembedded catalysts that we prepared by attaching the same nanoparticles onto support surfaces. Between nonembedded PdAu/SiO 2 and PdAu/TiO 2 , we identified a support effect resulting in a 1.4-fold higher activity of PdAu/TiO 2 than PdAu/SiO 2 for benzaldehyde hydrogenation. Notably, partial nanoparticle embedding in the TiO 2 raspberry-colloid-templated support increased the metal–support interfacial perimeter and consequently, the number of Au/TiO 2 interfacial sites by 5.4-fold, which further enhanced the activity of PdAu/TiO 2 by an additional 4.1-fold. Theoretical calculations and in situ surface-sensitive desorption analyses reveal facile benzaldehyde binding at the Au/TiO 2 interface and at Pd ensembles on the nanoparticle surface, explaining the connection between the number of Au/TiO 2 interfacial sites (via the metal–support interfacial perimeter) and catalytic activity. Our results demonstrate partial nanoparticle embedding as a synthetic strategy to produce thermocatalytically stable catalysts and increase the number of catalytically active Au/TiO 2 interfacial sites to augment catalytic contributions arising from metal–support interfaces.

Lim, Kang Rui Garrick (ORCID:0000000321599844)↗

NASA NTRS1974

Flutter of panels on discrete flexible supports

The supersonic flutter of wide panels on discrete flexible supports is investigated for three different panel-support configurations. The first study examines the effect of support stiffness on the flutter behavior of a specific five-support configuration with leading-and trailing-edge overhangs; this configuration was recently under consideration for a heat shield on an entry body. The second study investigates the effect of support stiffness on flutter of panels with various numbers of equally spaced supports. The third study examines the effect of center-support location on the flutter of panels with three supports. Results are presented in nondimensional form. The analysis is based on wide-plate structural theory and Ackeret aerodynamics. Finite differences are employed to obtain solutions for flutter pressure. A computer program based on this analysis and including a direct solution technique is presented. The program can be used to find the flutter pressure of wide panels of variable thickness supported by any number of flexible supports.

Stein, M.↗

NASA NTRS2009

Environmental Control and Life Support Integration Strategy for 6-Crew Operations

The International Space Station (ISS) crew compliment will be increasing in size from 3 to 6 crew members in the summer of 2009. In order to support this increase in crew on ISS, the United States on-orbit Segment (USOS) has been outfitted with a suite of regenerative Environmental Control and Life Support (ECLS) hardware including an Oxygen Generation System(OGS), Waste and Hygiene Compartment (WHC), and a Water Recovery System (WRS). The WRS includes the Urine Processor Assembly (UPA) and the Water Processor Assembly (WPA). A critical step in advancing to a 6Crew support capability on ISS is a full checkedout and verification of the Regenerative ECLS hardware. With a successful checkout, the ISS will achieve full redundancy in its onorbit life support system between the USOS and Russian Segment (RS). The additional redundancy created by the Regenerative ECLS hardware creates the opportunity for independent support capabilities between segments, and for the first time since the start of ISS, the necessity to revise Life Support strategy agreements. Independent operating strategies coupled with the loss of the Space Shuttle supply and return capabilities in 2010 offers additional challenges. These challenges create the need for a higher level of onorbit consumables reserve to ensure crewmember life support during a system failure. This paper will discuss the evolution of the ISS Life Support hardware strategy in support of 6Crew on ISS, as well as the continued work which will be necessary to ensure the support of crew and ISS Program objectives through the life of station.

FROM↗

NASA NTRS2010

Developing a Logistics Data Process for Support Equipment for NASA Ground Operations

The United States NASA Space Shuttle has long been considered an extremely capable yet relatively expensive rocket. A great part of the roughly US $500 million per launch expense was the support footprint: refurbishment and maintenance of the space shuttle system, together with the long list of resources required to support it, including personnel, tools, facilities, transport and support equipment. NASA determined to make its next rocket system with a smaller logistics footprint, and thereby more cost-effective and quicker turnaround. The logical solution was to adopt a standard Logistics Support Analysis (LSA) process based on GEIA-STD-0007 http://www.logisticsengineers.org/may09pres/GEIASTD0007DEXShortIntro.pdf which is the successor of MIL-STD-1388-2B widely used by U.S., NATO, and other world military services and industries. This approach is unprecedented at NASA: it is the first time a major program of programs, Project Constellation, is factoring logistics and supportability into design at many levels. This paper will focus on one of those levels NASA ground support equipment for the next generation of NASA rockets and on building a Logistics Support Analysis Record (LSAR) for developing and documenting a support solution and inventory of resources for. This LSAR is actually a standards-based database, containing analyses of the time and tools, personnel, facilities and support equipment required to assemble and integrate the stages and umbilicals of a rocket. This paper will cover building this database from scratch: including creating and importing a hierarchical bill of materials (BOM) from legacy data; identifying line-replaceable units (LRUs) of a given piece of equipment; analyzing reliability and maintainability of said LRUs; and therefore making an assessment back to design whether the support solution for a piece of equipment is too much work, i.e., too resource-intensive. If one must replace or inspect an LRU too much, perhaps a modification of the design of the equipment can make such operational effort unnecessary. Finally, this paper addresses processes of tying resources to a timeline of tasks performed in ground operations: this enables various overarching analyses, e.g., a summarization of all resources used for a given piece of equipment. Quality Control of data will also be discussed: importing and exporting data from product teams, including spreadsheets-todatabase or data exchange between databases.

Chakrabarti, Suman↗

NASA NTRS2012

Fischer-Tropsch Cobalt Catalyst Improvements with the Presence of TiO2, La2O3, and ZrO2 on an Alumina Support

The objective of this study was to evaluate the effect of titanium oxide, lanthanum oxide, and zirconium oxide on alumina supported cobalt catalysts. The hypothesis was that the presence of lanthanum oxide, titanium oxide, and zirconium oxide would reduce the interaction between cobalt and the alumina support. This was of interest because an optimized weakened interaction could lead to the most advantageous cobalt dispersion, particle size, and reducibility. The presence of these oxides on the support were investigated using a wide range of characterization techniques such as SEM, nitrogen adsorption, x-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed reduction after reduction (TPR-AR), and hydrogen chemisorptions/pulse reoxidation. Results indicated that both La2O3 and TiO2 doped supports facilitated the reduction of cobalt oxide species in reference to pure alumina supported cobalt catalysts, however further investigation is needed to determine the effect of ZrO2 on the reduction profile. Results showed an increased corrected cluster size for all three doped supported catalysts in comparison to their reference catalysts. The increase in reduction and an increase in the cluster size led to the conclusion that the support-metal interaction weakened by the addition of TiO2 and La2O3. It is also likely that the interaction decreased upon presence of ZrO2 on the alumina, but further research is necessary. Preliminary results have indicated that the alumina-supported catalysts with titanium oxide and lanthanum oxide present are of interest because of the weakened cobalt support interaction. These catalysts showed an increased extent of reduction, therefore more metallic cobalt is present on the support. However, whether or not there is more cobalt available to participate in the Fischer-Tropsch synthesis reaction (cobalt surface atoms) depends also on the cluster size. On one hand, increasing cluster size alone tends to decrease the active site density; on the other hand, by increasing the size of the cobalt clusters, there is less likelihood of forming oxidized cobalt complexes (cobalt aluminate) during Fischer-Tropsch synthesis. Thus, from the standpoint of stability, improving the extent of reduction while increasing the particle size slightly may be beneficial for maintaining the sites, even if there is a slight decrease in overall initial active site density.

Klettlinger, Jennifer Lindsey Suder↗

DOE OSTI2021

Composites and additive manufacturing for high-field coil supports for stellarators

The utilization of composites layered on an additive manufactured substrate, for the production of coil supports for modular coils in small or middle size experimental stellarators is assessed. The focus of the study is a monolithic coil support comprising the coils of a half-period of a stellarator, somewhat similar to the ones in UST_2 and ARIES-CS stellarators. However, the concept may be applicable to quasi-monolithic coil supports (coil forms of NCSX type) or individual coil casings (W7-X type).Coil supports for stellarators require high precision, stiffness and strength for large contorted parts. Traditionally, monolithic coil supports are produced by steel casting/forging and final machining. This production method and material gives accurate, stiff and strong coil supports, but the method may be expensive for monolithic supports due to the geometrical complexity and required accuracy of the structure. In relation to those matters, this work investigates whether a monolithic coil support comprising an additive manufactured resin substrate, which is externally (outward from the coils) surrounded with a thick layer of fibre-reinforced resin, may achieve enough strength and stiffness under middle/high magnetic fields. Finite element calculations are produced to obtain the direction of the principal stresses and their values in compression and tension at different areas of the monolithic support, which is relevant for anisotropic materials. The feasibility of directional application of (carbon) fibres on the winding surface of the stellarator outward from the coils is experimentally tested on a scaled-down additively manufactured prototype of a monolithic support. The strength and stiffness of the composite structure appears sufficient for common magnetic fields in experimental stellarators, and the 3D-composite design and manufacturing was technically feasible.

Queral, Vicente↗

DOE OSTI2012

Fuel Cell Tech Team Meeting: Engineered Nano-scale Ceramic Supports for PEM Fuel Cells [Slides]

Catalyst support durability is currently a technical barrier for commercialization of polymer electrolyte membrane (PEM) fuel cells, especially for transportation applications. Degradation and corrosion of the conventional carbon supports leads to losses in active catalyst surface area and, consequently, reduced performance. As a result, the goal of this work is to develop support materials that interact strongly with Pt, yet sustain bulk-like catalytic activities with very highly dispersed particles. Ceramic materials that are prepared using conventional solid-state methods have large grain sizes and low surface areas that can only be minimally ameliorated through grinding and ball milling. Other synthesis routes to produce ceramic materials must be investigated and utilized in order to obtain desired surface areas. In this work, several different synthesis methods are being utilized to prepare electronically conductive ceramic boride, nitride, and oxide materials with high surface areas and have the potential for use as PEMFC catalyst supports. Polymer-assisted deposition (PAD) and aerosol-through plasma (A-T-P) torch are among several methods used to obtain ceramic materials with surface areas that are equal to, or exceed Vulcan XC-72R supports. Cubic Mo-based ceramic phases have been prepared with average XRD-determined crystallite sizes as low as 1.6 nm (from full profile, XRD fitting) and a BET surface area exceeding 200 m 2 /g. Additionally, black, sub-stoichiometric TiO 2-x , have been prepared with an average crystallite size in the 4 nm range and surface areas exceeding 250 m 2 /gr. Pt disposition using an incipient wetness approach produced materials with activity for hydrogen redox reactions and ORR. Cyclic voltammetry data will be shown for a variety of potential Pt/ceramic catalysts. Initial experiments indicate enhanced Pt metal-support interactions as well. Plane wave periodic density functional calculations (VASP) are being used to predict the thermodynamic and activation barriers for fundamental electrode processes occurring at platinum surfaces supported on thin films of the ceramic support materials. The results of this work will be used in order to optimize support properties.

08 HYDROGEN↗

NASA NTRSDate not supplied

Supportability Concepts for Crewed Deep Space Exploration

Supportability—defined as the set of system characteristics that influence the logistics and support required to enable safe and effective operations—will be a much larger driver of mass, risk, and crew time for future human space exploration due to the more challenging mission context. For Mars, systems must operate in a logistically isolated environment for much longer durations than previous missions, which results in a higher probability of system failure and therefore an increased need for maintenance or contingency options. Mars missions also lack access to quick aborts, which increases the consequences of an unrecoverable system failure. Together, this higher likelihood and consequence of failure results in an increase in supportability-related risk. Supportability analysis is an important part of systems development that helps designers better understand the impacts of system and mission decisions on risk, mass, and crew time. The real-world processes that drive maintenance requirements and other supportability-related characteristics are probabilistic, and therefore they require different conceptual approaches and models than are used for more deterministic aspects of space systems. This paper provides an overview of supportability analysis, addresses key concepts, and provides examples of how supportability analysis can be incorporated into system development. Specifically, system supportability involves stochastic processes, and therefore must be evaluated using probabilistic models. These models can be used to perform sensitivity analysis even if system characteristics are not yet fully defined. Failure rates cannot be measured directly, but tests provide valuable data that can help refine those estimates. Human spaceflight architectures are complex, and exhibit coupled behavior that should be examined with integrated systems analysis that includes an assessment of supportability.

Supportability↗

NASA NTRSDate not supplied

Supportability Concepts for Crewed Deep Space Exploration

Supportability↗

DOE OSTI2025

Tuning Catalytic Reactivity via Wetting Control through Oxygen Vacancies: Ru Clusters on Anatase TiO 2 and CeO 2 Supports

The shape of supported metal particles regulates their catalytic reactivity and is determined by the degree of wetting between the metal particle and the support surface. Flattened particles that wet support surfaces were reported in various catalytic systems, particularly in the subnanometer size regime. Such consequential metal–support wetting phenomena are poorly understood, and methods to study them on powder catalysts under realistic conditions are lacking. Here, we investigate the size-dependent wetting behaviors of Ru particles on two reducible-oxide supports, anatase TiO 2 (TiO 2 -A) and CeO 2 , under reducing catalytic conditions. X-ray absorption spectroscopy (XAS), low-energy ion scattering (LEIS), and density functional theory (DFT) are combined to determine the shape of Ru particles. Ru particles remain three-dimensional without wetting the TiO 2 -A support within the coverage range studied (0.06–0.98 Ru nm –2 ). In contrast, at low coverages (<0.25 Ru nm –2 ), Ru wets the CeO 2 support to form flat, disordered structures. The higher wettability of CeO 2 than TiO 2 -A is attributed to oxygen vacancies in the near-surface region. The shape difference between small Ru particles or clusters on the two supports leads to drastically contrasting catalytic reactivities in polyolefin hydrogenolysis, despite similar diameters. As a result, this work highlights the implications of metal–support wetting, or cluster shape, on catalytic behaviors of small metal clusters, while establishing the foundation for future systematic studies of such a phenomenon in realistic systems, by delivering a multitechnique methodology and revealing governing fundamental principles.

42 ENGINEERING↗

DOE OSTI2020

Tutorial review on structure – dendrite growth relations in metal battery anode supports

This tutorial review explains the emerging understanding of the surface and bulk chemistry – electrochemical performance relations in anode supports (aka secondary current collectors, substrates, templates, hosts) for lithium, sodium and potassium metal batteries (LMBs, SMBs or NMBs, and KMBs or PMBs). In relation to each section, the possible future research directions that may yield both new insight and improved cycling behavior are explored. Representative case studies from Li, Na and K metal anode literature are discussed. The tutorial starts with an overview of the solid electrolyte interphase (SEI), covering both the “classic” understanding of the SEI structure and the “modern” insights obtained by site-specific cryogenic stage TEM analysis. Next, the multiple roles of supports in promoting cycling stability are detailed. Without an optimized support architecture, the metal–electrolyte interface becomes geometrically unstable at a lower current density and cycle number. Taking into consideration the available literature on LMBs, SMBs and KMBs, it is concluded that effective architectures are geometrically complex and electrochemically lithiophilic, sodiophilic or potassiophilic, so as to promote conformal electrochemical wetting of the metal during plating/stripping. One way that philicity is achieved is through support oxygen surface chemistry, which yields a reversibly reactive metal–support interface. Examples of this include the well-known oxygen–carbon moieties in reduced graphene oxide (rGO), as well as classic ion battery reversible conversion reaction oxides such as SnO 2 . Unreactive surfaces lead to dewetted island growth of the metal, which is a precursor to dendrites, and possibly to non-uniform dissolution. Surveying the literature on various Li, Na and K metal supports, it is concluded that the key bulk thermodynamic property that will predict electrochemical wetting behavior is the enthalpy of infinite solution (Δ sol H ∞ ) of the metal (solute) into the support (solvent). Large and negative Δ sol H ∞ promotes uniform metal wetting on the support surface, corresponding to relatively low plating overpotential. Positive Δ sol H ∞ promotes dewetted islands and a relatively high overpotential. This simple rule explains a broad range of studies on Li, Na and K metal – support interactions, including the previously reported correlation between mutual solubility and wetting.

25 ENERGY STORAGE↗