Electrochemical dynamics investigated by small angle scattering

Abstract

Electrodeposition has been proven a viable tool for the making of nanostructures (template electrodeposition), which are most promising in achieving novel properties through nanoscale effects. In this work, Small angle X-ray and neutron scattering is applied to study the structural properties of electrodeposited materials due to its suitability for operando electrochemistry experiments. Firstly, Grazing Incidence Small Angle Xray Scattering (GISAXS) is used to investigate the arrangement of electrodeposited Au particles on a bare TiN electrode. This system represents a simplification of the configuration needed for template electrodeposition of nanomaterials and it is used to explore the arrangement of the deposits without the constraints of a physical template, showing their non-random arrangement. The understanding gained from this first study is then applied to the non-aqueous electrodeposition of bismuth telluride from dichloromethane, which is observed through in situ Grazing Incidence Neutron Scattering (GISANS). Neutrons are chosen in order to decouple the observations from processes happening within the electrolyte solution, but require a suitable electrochemical cell with unusually large electrodes. No evidence for the individual deposition of Bi and Te is found for deposition times longer than 1 s. Another route undergone in this work is the investigation of Electrochemically Assisted Surfactant Assembly (EASA) using operando GISAXS. EASA represents a reliable technique for the making of vertically aligned mesoporous silica films, which in turn are applicable to template electrodeposition. Its limitations in applicability arise from the unwanted formation of surface aggregates and the narrow range of available pore sizes. The operando experiments give the first time-resolved insight into the EASA process, showing film and aggregate formation under real conditions. A novel route for reduced aggregates using an electrolyte-free sol is presented. Lastly, nanostructured HPd pH sensors are made and used to monitor the hydroxide concentration in the vicinity of a TiN electrode under electric potential, showing that hydrogen, water and oxygen reduction dominate the formation of the gradient, and that its relaxation time widely exceeds typical deposition times.

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Identifiers

ORCID for Gilles Ernest Heinrich Karl Moehl: orcid.org/0000-0003-4910-3601

ORCID for Andrew Hector: orcid.org/0000-0002-9964-2163

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