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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 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

In-situ and in-operando analysis of voltage losses using sense wires for proton exchange membrane water electrolyzers

Proton exchange membrane water electrolyzer development requires understanding processes at the materials and interface levels to reach the required performance and lifetime targets for increasing market penetration. To achieve the required progress, it is critical to develop advanced in-situ diagnostics that allow observation of the changes that come with the reduction of catalyst loading combined with long-term intermittent operation. This work presents an internal voltage sensing method that enables observing internal voltage drops in an operating electrolyzer cell. It allows the total cell resistance to be separated into anode, CCM, and cathode resistance. The method is demonstrated by operating cells with different anode porous transport layers (PTLs). The changing properties of the PTLs result in significant variations of the resistances. Enhancing the PTL properties with a protective coating reduces the anode resistance significantly. In addition to these observations, the method enables a real-time monitoring of resistance related values that impact performance in water electrolyzers. Long-term experiments with the method allow us to gain insights into processes that occur during operation such as conditioning or degradation. The internal voltage sensing method presented in this study is a novel technique for diagnosing, analyzing, and optimizing water electrolyzers and other energy conversion devices.

42 ENGINEERING↗
DOE OSTI2016

Growth of boron doped hydrogenated nanocrystalline cubic silicon carbide (3C-SiC) films by Hot Wire-CVD

Highlights: • Boron doped nc-3C-SiC films prepared by HW-CVD using SiH{sub 4}/CH{sub 4}/B{sub 2}H{sub 6}. • 3C-Si-C films have preferred orientation in (1 1 1) direction. • Introduction of boron into SiC matrix retard the crystallanity in the film structure. • Film large number of SiC nanocrystallites embedded in the a-Si matrix. • Band gap values, E{sub Tauc} and E{sub 04} (E{sub 04} > E{sub Tauc}) decreases with increase in B{sub 2}H{sub 6} flow rate. - Abstract: Boron doped nanocrystalline cubic silicon carbide (3C-SiC) films have been prepared by HW-CVD using silane (SiH{sub 4})/methane (CH{sub 4})/diborane (B{sub 2}H{sub 6}) gas mixture. The influence of boron doping on structural, optical, morphological and electrical properties have been investigated. The formation of 3C-SiC films have been confirmed by low angle XRD, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) spectroscopy and high resolution-transmission electron microscopy (HR-TEM) analysis whereas effective boron doping in nc-3C-SiC have been confirmed by conductivity, charge carrier activation energy, and Hall measurements. Raman spectroscopy and HR-TEM analysis revealed that introduction of boron into the SiC matrix retards the crystallanity in the film structure. The field emission scanning electron microscopy (FE-SEM) and non contact atomic force microscopy (NC-AFM) results signify that 3C-SiC film contain well resolved, large number of silicon carbide (SiC) nanocrystallites embedded in the a-Si matrix having rms surface roughness ∼1.64 nm. Hydrogen content in doped films are found smaller than that of un-doped films. Optical band gap values, E{sub Tauc} and E{sub 04} decreases with increase in B{sub 2}H{sub 6} flow rate.

36 MATERIALS SCIENCE↗