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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Boosting Thermoelectric Performance in Nanocrystalline Ternary Skutterudite Thin Films through Metallic CoTe 2 Integration

Metal–semiconductor nanocomposites have emerged as a viable strategy for concurrently tailoring both thermal and electronic transport properties of established thermoelectric materials, ultimately achieving synergistic performance. In this investigation, a series of nanocomposite thin films were synthesized, embedding metallic cobalt telluride (CoTe 2 ) nanophase within the nanocrystalline ternary skutterudite (Co(Ge 1.22 Sb 0.22 )Te 1.58 or CGST) matrix. Our approach harnessed composition fluctuation-induced phase separation and in situ growth during thermal annealing to seamlessly integrate the metallic phase. The distinctive band structures of both materials have developed an ohmic-type contact characteristic at the interface, which raised carrier density considerably yet negligibly affected the mobility counterpart, leading to a substantial improvement in electrical conductivity. The intricate balance in transport properties is further influenced by the metallic CoTe 2 phase’s role in diminishing lattice thermal conductivity. The presence of the metallic phase instigates enhanced phonon scattering at the interface boundaries. Consequently, a 2-fold enhancement in the thermoelectric figure of merit (zT ~ 1.30) is attained with CGST-7 wt. % CoTe 2 nanocomposite film at 655 K compared to that of pristine CGST.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Optimizing Materials to Boost the Valorization of CO 2 : Tuning Cobalt–Cobalt Interactions on In 2 O 3 -Based Photothermal Catalysts

The valorization of CO 2 is an important challenge within the current panorama, since this molecule is probably the main contributor to climate change. In this study, the synthesis of materials based on a nanostructured batonnet-type indium oxide is carried out. In them, different amounts of Co are introduced, varying between 2 and 8% mol. It is verified that the most active sample in the transformation of carbon dioxide to carbon monoxide contains 6 mol %. of Co. This sample’s activity under dual excitation exceeds the thermal counterpart by more than 30%. After carrying out a complete physical and chemical characterization with the help of X-ray absorption spectroscopy and other techniques, it is shown that catalysts with amounts of cobalt equal to or below 4 mol % contain isolated single-atom species, while those with higher amounts of metal display a Co–Co interaction which triggers the evolution of the samples under reaction conditions. The optimum control of this Co–Co interaction and the nature of the final cobalt-containing species determine dual photothermal catalytic properties. In conclusion, this work establishes a structure–activity relationship to interpret the catalytic behavior of highly dispersed subnanometric cobalt species, and thus an avenue to optimize the photothermal valorization of carbon dioxide.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Self-Aligned Fluorinated-Organic Ligand for Boosting the Performance of Perovskite Solar Cells

Surface passivation is evident to be one of the most efficient approaches to achieve high efficiency with superior stability of perovskite solar cells (PeSCs). However, most previous approaches to surface passivation involve adding an additional coating process either before or after perovskite film fabrication, thereby introducing an extra processing step and significantly increasing production costs. Here, a simple yet novel one-step interfacial passivation approach was implemented by utilizing the self-aligning properties of fluorinated organic ligands (F4TmI) within a perovskite precursor solution. The inherent propensity of the ligand to spontaneously anchor onto the surface of perovskite guides the crystallization process of perovskites, thus largely enhancing the device performance and humidity stability. The optimized F4TmI-based devices achieved an efficiency of 21.1%, surpassing that of the control (19.8%). Furthermore, the device stability significantly improved after the incorporation of F4TmI, maintaining 78.9 and 95.1% of its initial efficiency after aging at 60 °C and 60% relative humidity, respectively, for 330 h.

14 SOLAR ENERGY↗
DOE OSTI2025

Boosting the Oxygen Evolution Reaction by Tuning the Interfacial Iron Adsorption on Layered Double Hydroxide

Understanding the interaction between ions in the electrolyte and electrode materials plays an important role in optimizing the water electrolysis performance for hydrogen production. Herein, the synergistic effect of iron (Fe) in the electrolyte and interlayer anions within the layered structure on the oxygen evolution reaction (OER) has been investigated by combining material synthesis with controlled structure, multiple characterization techniques, and first-principles calculations. Nickel aluminum layered double hydroxides (NiAl-LDHs) with different interlayer anions (CO 3 2– , Cl – , and Br – ) show similar oxygen evolution activity in the absence of Fe species in the electrolyte. The addition of Fe into the electrolyte results in improved performance for all of the NiAl-LDHs, following the rank LDH-Br > LDH-Cl > LDH-CO 3 , under all of the conditions with varied concentration of Fe. X-ray absorption spectroscopy and identical location electron microscopy analyses show that the LDH structure remains unchanged after the OER activity test, while in situ stationary probe rotating disk electrode inductively coupled plasma mass spectrometry (SPRDE-ICP-MS) measurements show partial dissolution of the intercalating halide ions during cycling, with less dissolution for Br-intercalated materials. Insights from theoretical calculations demonstrate the thermodynamic preference of Br – to remain intercalated in the presence of Fe, while the stronger adsorption of Fe(OH) 3 species on the LDH-Br sample promotes the OER activity. In conclusion, these results provide mechanistic insights into the rational design of active layered materials with an enhanced OER performance for efficient water electrolysis.

58 GEOSCIENCES↗
DOE OSTI2020

Rhombohedral Ordered Intermetallic Nanocatalyst Boosts the Oxygen Reduction Reaction

Low platinum-group-metal (PGM) ordered intermetallic catalysts have been considered one of the most promising candidates for catalyzing the oxygen reduction reaction (ORR) in fuel cells, but achieving the desired performances in terms of activity, durability, and cost is still a grand challenge for the fuel cell research field. While the cubic- and tetragonal-ordered (L1 2 and L1 0 phases) low-PGM nanocatalysts have been investigated extensively and have shown considerably improved durability and activity toward the ORR, so far, little is known about rhombohedral ordered L1 1 catalysts. Here, we report the synthesis of an L1 1 -ordered PtCu catalyst for the ORR. We demonstrate that by applying nitrogen (N) doping through a thermal treatment in an NH 3 gas, the activity and stability of the N-doped, rhombohedral ordered PtCu catalyst can be further enhanced, and the ORR mass and specific activities achieve nearly 5-fold and 4-fold enhancement in acidic media, respectively, relative to those of commercial Pt/C. In situ synchrotron X-ray absorption and pair-distribution-function measurements reveal that both the formation of the ordered intermetallic structure and N-doping synergistically improve the corrosion resistance of the PtCu catalyst by lowering the Cu diffusivity and introduce a compressive strain effect regulating the adsorption of oxygenated species on the Pt surface, thus accounting for the improved ORR kinetics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Transforming Boron Carbon Nitride: A Carbon-to-Oxygen Switch to Boost Propane Oxidative Dehydrogenation

Hexagonal boron nitride (h-BN) catalysts exhibit high alkene selectivity in the oxidative dehydrogenation of propane (ODHP). Nevertheless, the conversion-selectivity trade-off persisted primarily due to the low density of oxygen-containing boron active species, while simple and controllable modification strategies for h-BN still face challenges. Herein, we developed an in situ carbon-to-oxygen switch strategy within a tailored boron carbon nitride (BCN) framework, in which uniformly embedded B–C 3 were transformed into B–O 3 via oxidative treatment (denoted as BNO x ). The structural evolution from B–C 3 to B–O 3 was well characterized by spectroscopy and soft X-ray absorption techniques. The resulting BNO x catalysts, enriched with B–O 3 units, demonstrated performance in ODHP, achieving a propane conversion of 50.4% with 32.7% olefin yield at 500 °C. Density functional theory (DFT) calculations confirmed that B–O 3 species preferentially lower activation barriers, rendering the process thermodynamically more favorable. In conclusion, this work introduced an in situ reconstruction method for atomic-level heteroatom-engineered h-BN catalysts, opening an avenue for advanced catalyst design across energy conversion systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Quantum Shells Boost the Optical Gain of Lasing Media

Auger decay of multiple excitons represents one of the main obstacles to photonic applications of semiconductor quantum dots (QDs). These non-radiative processes are particularly detrimental to the performance of QD-based electroluminescent and lasing devices. Here, we demonstrate that by using semiconductor quantum shells with an “inverted” QD geometry, it is possible to inhibit Auger recombination, allowing extraordinary improvements to their multi-exciton characteristics. Additionally, we show that quantum shells result in ultralong biexciton lifetimes (>10 ns), and an associated biexciton quantum yield of up to 81%. Furthermore, the energy-dispersive architecture of quantum shells leads to exciton-exciton repulsion, which splits the single-exciton and bi-exciton optical transitions. In this regime, quantum shells produce the longest optical gain lifetime reported for colloidal QDs to date (> 6 ns) over a broad amplification bandwidth. Therefore, the employment of quantum shells in optically- or electrically-pumped gain media can lead to a substantial improvement in device performance.

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

Mesoporous 3D/2D NiCoP/g-C 3 N 4 Heterostructure with Dual Co–N and Ni–N Bonding States for Boosting Photocatalytic H 2 Production Activity and Stability

The mesoporous 3D/2D NiCoP/g-C 3 N 4 heterostructure is fabricated by embedding NiCoP nanoclusters on the surfaces of g-C 3 N 4 nanosheets, which exhibit more outstanding photocatalytic H 2 production activity than g-C 3 N 4 modified with Pt and other similar phosphides. The highest H 2 production rate over NiCoP/g-C 3 N 4 heterostructures reaches up to about 2.27 times than that of Pt/g-C 3 N 4 under visible light, and meanwhile, the NiCoP/g-C 3 N 4 heterostructure can maintain a continuously stable H 2 production rate during long cyclic running of 15 times in a total of 60 h. Here, the structure and properties investigations reveal that the splendid H 2 production activity and stability derive from the formed dual Co–N and Ni–N bonding states between 3D NiCoP nanoclusters and 2D g-C 3 N 4 nanosheets that can efficiently facilitate the transfer and separation of charge carriers and improve the interaction at heterointerfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Fe–N–C Boosts the Stability of Supported Platinum Nanoparticles for Fuel Cells

The poor durability of Pt-based nanoparticles dispersed on carbon black is the challenge for the application of long-life polymer electrolyte fuel cells. Recent work suggests that Fe- and N-codoped carbon (Fe-N-C) might be a better support than conventional high-surface-area carbon. In this work, we find that the electrochemical surface area retention of Pt/Fe-N-C is much better than that of commercial Pt/C during potential cycling in both acidic and basic media. In situ inductively coupled plasma mass spectrometry studies indicate that the Pt dissolution rate of Pt/Fe-N-C is 3 times smaller than that of Pt/C during cycling. Density functional theory calculations further illustrate that the Fe-N-C substrate can provide strong and stable support to the Pt nanoparticles and alleviate the oxide formation by adjusting the electronic structure. The strong metal-substrate interaction, together with a lower metal dissolution rate and highly stable support, may be the reason for the significantly enhanced stability of Pt/Fe-N-C. In conclusion, this finding highlights the importance of carbon support selection to achieve a more durable Pt-based electrocatalyst for fuel cells.

25 ENERGY STORAGE↗