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Kreller, Cortney R.

Publications and source records attributed to Kreller, Cortney R..

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Quantification of gas concentrations in NO/NO 2 /C 3 H 8 /NH 3 mixtures using machine learning

We employ machine learning to decode the composition of unknown gas mixtures from the output of an array of four electrochemical sensors. The sensors use metal oxide electrodes paired with a ceramic electrolyte, yttria-stabilized zirconia (YSZ), to produce voltage responses to the presence of gases in complex mixtures. The voltages from the sensor array serve as inputs to a machine learning pipeline which first carries out multi-class classification of mixtures into types based on which gases are present at non-zero concentrations, and subsequently predicts gas concentrations given the mixture type. Thus, our model is able to take a single reading from the sensor array in response to gas mixtures involving NO, NO 2 , C 3 H 8 , and NH 3 , and output a highly accurate prediction of which gases are present in the mixture, along with the concentrations of each constituent gas. Of note, our computational framework can be easily expanded to include additional gases and additional mixture types, allowing it to be used in numerous automotive, industrial and environmental monitoring settings.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

High Performing and Durable Pyrophosphate Based Composite Membranes for Intermediate Temperature Fuel Cells [Slides]

Objective: Develop a novel proton conducting electrolyte operating at >200°C with conductivity σ ≥ 100 mScm –1 and RH < 1%. Fabrication of membranes of less than 40μm thickness while retaining high conductivity will result in ASR <0.04 Ωcm 2 . Evaluate membrane durability in terms of crossover, shorting resistance, and open circuit voltage, as well as against temperature cycling. Relevance: Operating FCs in the intermediate temperature range has the potential to greatly reduce cost and simplify water and thermal management. This effort requires novel materials and approaches to meet DOE membrane performance and durability targets. MPP/Polymer composite membranes show promise in early development for application in IT-FCs for transportation applications. Approach: We have demonstrated that both cation dopants and phosphate precursor influence MPP conductivity and identified the most promising MPP compositions for membrane fabrication. The ceramic MPP materials are fabricated as a composite membrane in a 90:10 wt% ratio with Nafion. We have modified our membrane fabrication procedure to improve the density of our membranes. Accomplishments: We demonstrated through-plane membrane conductivity of 95mScm -1 at T > 200°C and RH<0.04bar with a thickness 50μm. We demonstrated FC performance up to 94hrs at 220°C and <1% RH with a 50μm thick membrane exhibiting an OCV of 0.98V and ASR of 0.08 Wcm 2 . Future work: Further decrease in ASR is expected by decreasing the membrane thickness to <40μm. ITPP with higher P:M ratio will be used to increase the conductivity of the starting material. Long term durability will be assessed against DOE technical targets

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Molybdenum Carbide Electrocatalysts for Electrochemical Synthesis of Ammonia from Nitrogen: Activity and Stability

Ammonia production has increased from few thousand tons in 1908 to above 200 million tons per year today, revolutionizing the fertilizer industry thanks to the Haber-Bosch (HB) process. However, the HB process is highly energy intensive consuming about 1.4% of fossil energy generated worldwide and releasing 1.87 tons of CO 2 per ton of ammonia produced. This further reduces ammonia’s scope as a carrier fuel for the hydrogen economy. Hence, finding alternative energy efficient ways to synthesize ammonia is important from more than one perspective. Ammonia synthesis from its constituent nitrogen and hydrogen gases is mainly hampered by the nitrogen reduction reaction (NRR) due to the strong N≡N bond (945 kJ mol −1 ). Electrochemical synthesis (ES) routes in this regard offer a milder approach. However, ES of ammonia under different temperatures, utilizing different electrolytes and catalysts has not yet reliably produced ammonia at viable rates and efficiencies. We report an origami-like Mo 2 C cathode catalyst for NRR that achieved a maximum synthesis rate of 2.16 × 10 −11 mol cm −2 s −1 and a faradaic efficiency of 1.8% at 30 °C using Nafion-212 as electrolyte. Origami-like morphology containing numerous kinks appears to improve electrocatalytic activity and show a promising route for fabricating NRR catalysts with higher catalytic activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗