Hydrogen absorption into titanium under cathodic polarization: An in-situ neutron reflectometry and EIS study

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DOIResolve DOI: http://doi.org/10.1149/2.020309jes
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Journal titleJournal of the Electrochemical Society
SubjectAbsorption kinetics; Diffusion process; Electronic defects; Hydrogen absorption; Hydrogen penetration; Neutron reflectometry; Redox transformations; Scattering length density; Cathodic polarization; Deuterium; Electrochemical impedance spectroscopy; Film growth; Grain boundaries; Heavy water; Neutron reflection; Oxide films; Titanium; Titanium dioxide; Hydrogen
AbstractHydrogen (deuterium) absorption into sputter-coated titanium (Ti) film electrodes during cathodic polarization in heavy water (D2O) was monitored using in-situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS). The scattering length density (SLD) of Ti metal increased with increasing cathodic polarization, due to the penetration of deuterium through the surface oxide and into the underlying metal. The rate of D absorption estimated from the NR data showed a pattern with four distinctive regions separated by potential boundaries between -0.35 and -0.4 VSCE and around ∼-0.6 VSCE. EIS results support division of the behavior into these potential ranges. Hydrogen absorption by Tiwas observed at potentials <∼-0.35 VSCE, where the capacitance and resistance of the TiO2 layer dramatically changed. At this point, the D content of the film quickly achieved a level of ∼900 ppm by weight (atom ratio D:Ti ∼ 0.04). Decreased absorption kinetics were observed over the potential region from ∼-0.40 VSCE to -0.6 VSCE, indicating that D absorption was controlled either by a diffusion process through the TiO 2 layer or by the formation of blocking hydrides at the Ti/TiO 2 interface, at the base of the defective locations in the oxide through which the hydrogen was entering. Significant increases in the current density and SLD of the Ti film at potentials more negative than -0.6 V SCE were assigned to widespread hydrogen absorption and TiH x growth within the metal. These observations are consistent with hydrogen ingress through the oxide film, probably via weak points containing electronic defects and disorder, such as grain boundaries and triple points, at potentials as mild as ∼-0.4 VSCE, and with hydrogen penetration through continuous, intact oxide via the previously published redox transformation mechanism, at potentials more negative than -0.6 VSCE. © 2013 The Electrochemical Society. All rights reserved.
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AffiliationNational Research Council Canada (NRC-CNRC); NRC Canadian Neutron Beam Centre (CNBC-CCFN)
Peer reviewedYes
NPARC number21269746
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Record identifier9d815a00-de1b-4b09-a2a7-51fa03a5dcc0
Record created2013-12-13
Record modified2016-05-09
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