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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 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Gallium Oxide Heterojunction Diodes for 400 °C High‐Temperature Applications

β ‐Ga 2 O 3 ‐based semiconductor devices are expected to have significantly improved high‐power and high‐temperature performance due to its ultrawide bandgap of close to 5 eV. However, the high‐temperature operation of these ultrawide‐bandgap devices is usually limited by the relatively low 1–2 eV built‐in potential at the Schottky barrier with most high‐work‐function metals. Herein, heterojunction p ‐NiO/n‐ β ‐Ga 2 O 3 diodes fabrication and optimization for high‐temperature device applications are reported, demonstrating a current rectification ratio ( I ON / I OFF ) of more than 10 6 at 410 °C. The NiO heterojunction diode can achieve higher turn‐on ( V ON ) voltage and lower reverse leakage current compared to the Ni‐based Schottky diode fabricated on the same single‐crystal β ‐Ga 2 O 3 substrate, despite charge transport dominated by interfacial recombination. Electrical characterization and device modeling show that these advantages are due to a higher built‐in potential and additional band offset. These results suggest that heterojunction p–n diodes based on β ‐Ga 2 O 3 can significantly improve high‐temperature electronic device and sensor performance.

Sohel, Shahadat H.↗
DOE OSTI2017

Sugar Blowing-Induced Porous Cobalt Phosphide/Nitrogen-Doped Carbon Nanostructures with Enhanced Electrochemical Oxidation Performance toward Water and Other Small Molecules

Finely controlled synthesis of high active and robust nonprecious metal catalysts with excellent catalytic efficiency in oxygen evolution reaction (OER) is extremely vital for making the water splitting process more energy-efficient and economical. Among these noble metal-free catalysts, transition-metal-based nanomaterials are considered as one of the most promising OER catalysts due to their relatively low-cost intrinsic activities, high abundance and diversity in terms of structure and morphology. In this work, we reported a facile sugar-blowing technique and low-temperature phosphorization to generate 3D self-supported metal involved carbon nanostructures, which termed as Co2P@Co/nitrogen-doped carbon (Co2P@Co/N-C). By capitalizing on the 3D porous nanostructures with high surface area, generously dispersed active sites, the intimate interaction between active sites and 3D N-doped carbon, the resultant Co2P@Co/N-C exhibited satisfying OER performance superior to CoO@Co/N-C, delivering 10 mA cm-2 at overpotential of 0.32 V. It is noting that in contrast to the substantial current density loss of RuO2, Co2P@Co/N-C showed much enhanced catalytic activity during the stability test and the 1.8-fold increase in current density was observed after stability test. Furthermore, the obtained Co2P@Co/N-C can also be served as an excellent nonprecious metal catalyst for methanol and glucose electrooxidation in alkaline media, further extending their potential applications.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

NiAu Single Atom Alloys for the Non-oxidative Dehydrogenation of Ethanol to Acetaldehyde and Hydrogen

Gold is examined here as an alternative to copper for the selective dehydrogenation of ethanol to acetaldehyde and hydrogen. Despite its high selectivity, gold is only active at temperatures higher than 250 °C for this reaction. We demonstrate that addition of a small amount of Ni on either supported or unsupported Au surfaces induces resistance to sintering, along with a beneficial effect on the catalytic activity. NiAu alloys prepared here with Ni as the minority component to the limit of atomic dispersion in the gold surfaces, catalyze the reaction beginning below 150 °C. A significant decrease of the apparent activation energy from 96 ± 3 kJ/mol for the monometallic Au to 59 ± 5 kJ/mol for the alloy was found. The Ni dispersion and concentration as a function of gas environment was followed by in situ DRIFTS and by XPS. The stability of the catalyst morphology was investigated through post-reaction microscopy imaging and long-term stability tests under reaction conditions. As shown via dynamic reaction experiments, acetaldehyde and H 2 were selectively produced up to 280 °C. A small drop of selectivity at higher temperatures is attributed to the formation of Ni clusters, as proven by CO-DRIFTS on the used sample. Comparison with samples of higher Ni loading, where Ni clusters are formed, clearly shows that they catalyze the undesired full decomposition of ethanol to CO, CH 4 , and H 2 .

36 MATERIALS SCIENCE↗