Using Light to Probe Surface Electrochemical Processes
(2021)- Abstract
- This thesis shows how various light-based in situ techniques can be used to follow different surface electrochemical processes such as electrochemical deposition into Nanoporous Anodic Aluminium Oxide (NP-AAO) templates and the surface structure of electrodes. Techniques based on both x-rays and visible light were used to follow surface structures and compositions, in situ. The samples were also
investigated with ex situ techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and various other techniques. Templated electrodeposition processes, which can be used for growing various nanostructures with applications in for example gas sensors, catalysts, electrocatalysts and colouring of metal... (More) - This thesis shows how various light-based in situ techniques can be used to follow different surface electrochemical processes such as electrochemical deposition into Nanoporous Anodic Aluminium Oxide (NP-AAO) templates and the surface structure of electrodes. Techniques based on both x-rays and visible light were used to follow surface structures and compositions, in situ. The samples were also
investigated with ex situ techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and various other techniques. Templated electrodeposition processes, which can be used for growing various nanostructures with applications in for example gas sensors, catalysts, electrocatalysts and colouring of metal products were studied. Cyclic voltammetry (CV) for investigating electrooxidation and corrosion of model systems as well as real industrial materials was combined with Surface X-ray Diffraction and 2-Dimensional Surface Optical Reflectance.
Electrochemical deposition of Sn, Pd and Au into NP-AAO was investigated with both in situ and ex situ methods to gain information about the deposition process, the influence of the NP-AAO template on the growth of the nanostructures and the chemical and crystallographic nature of the grown nanostructures. For the Sn, it was possible to determine that the grown nanostructures were metallic with a beta-Sn crystal structure and a compression of the nanostructures due to the confinement of the pores were measured. Both the Pd and the Au nanostructures were constructed
of crystalline grains with grain sizes in the range of the pore diameter. A compressive and tensile strain could be measured across and along the
nanostructures, respectively.
The combination of 2-Dimensional Surface Optical Reflectance (2D-SOR), an optical microscope, with a modified electrochemical cell, was investigated through cyclic voltammetry measurements on Au, Pd and Super Duplex Stainless Steel and anodization of aluminium. The measured reflectance could be correlated with characteristic features in the CV curve corresponding to oxidation and reduction of the surface. By combining 2D-SOR with High Energy Surface X-ray Diffraction (HESXRD) during CV measurements the reflectance could be correlated with the
atomic changes of the Au(111) surface. It was also shown that 2D-SOR could detect monolayer changes of the surface, due to its sensitivity to the increased electron density of the Herringbone reconstruction, a rearrangement of the atoms in the topmost layer of the Au(111) single crystal surface. By applying this method to polycrystalline samples, it was possible to follow how differently oriented grains react differently during the same experimental conditions, showing the possibility for 2D-SOR to image inhomogeneous surfaces.
The Au(111) single crystal was further studied using CV and potential stepping going into the oxygen evolution reaction (OER). The combined HESXRD and 2D- SOR measurements detected a roughening of the surface as it was oxidized and during the OER. These measurements also suggest that the oxide on the Au(111) single crystal is amorphous, due to the lack of oxidation peaks in the measured diffraction pattern. With X-ray photoelectron spectroscopy measurements, it could be shown that sulphate species absorb on the surface before any oxide is detected,
the oxide is then formed and detected as the sulphate desorbs.
The possibility to follow and understand these different surface reactions gives knowledge which in the future could be used for example for the continued development of fuel cells, the development of devices, sensors, catalysts and to develop more corrosion-resistant materials. (Less) - Abstract (Swedish)
- Kemiska reaktioner drivna av en ström eller som producerar en ström heter elektrokemiska reaktioner och finns överallt omkring oss, ta bara till exempel ett batteri, här produceras en ström som kan driva till exempel din mobiltelefon. Förståelsen för dessa kemiska reaktioner och hur de påverkar den yta där reaktionerna sker är därför viktig. Det är också viktigt att förstå hur olika strukturer reagerar på den kemiska reaktionen då ett material kan ha många olika strukturer på sin yta samtidigt. Ett område som har fått stor betydelse är just elektrokatalys, där reaktionen vattendelning är av intresse och guld är ett av de material som kan användas som katalysator för att driva reaktionen. Denna reaktion kan användas för att producera väte... (More)
- Kemiska reaktioner drivna av en ström eller som producerar en ström heter elektrokemiska reaktioner och finns överallt omkring oss, ta bara till exempel ett batteri, här produceras en ström som kan driva till exempel din mobiltelefon. Förståelsen för dessa kemiska reaktioner och hur de påverkar den yta där reaktionerna sker är därför viktig. Det är också viktigt att förstå hur olika strukturer reagerar på den kemiska reaktionen då ett material kan ha många olika strukturer på sin yta samtidigt. Ett område som har fått stor betydelse är just elektrokatalys, där reaktionen vattendelning är av intresse och guld är ett av de material som kan användas som katalysator för att driva reaktionen. Denna reaktion kan användas för att producera väte till bränsleceller, en nödvändig utveckling för att skifta världens energikällor till förnybara. Ett annat viktigt område är produktionen av nanotrådar och nano partiklar då de har många användningsområden, i allt ifrån sensorer och katalysatorer till något så simpelt som att färga aluminiumprodukter. Undersökningar med hjälp av röntgenstrålning och synligt ljus kan ge en ökad
förståelsen för olika elektrokemiska processer, var till exempel oxidering av en yta eller hur nanotrådar växer inuti en ordnad struktur kan studeras under reaktionens gång.
I denna avhandling har potentialen av att använda 2D-SOR, ett optiskt reflektants mikroskop, för att undersöka yt-elektrokemiska reaktioner påvisats. Denna teknik kan detektera förändringar i en ytas reflektans då elektrokemiska reaktioner sker. Även möjligheten att visualisera olika strukturer i materialen med denna teknik är av stor nytta. Guld har även studerats i djupare utsträckning i denna avhandling för att få en bättre förståelse av dess yt-förändringarna då det oxiderar och då syreproduktion sker på dess yta. Nanotråds växt inuti porös aluminiumoxid har
också studerats i denna avhandling, vilket gav både kunskap om hur nanotrådarna växte och hur den porösa aluminiumoxiden i vilken de växte påverkade nanotrådarna.
Denna avhandling är del av Röntgen-Ångström projektet HEXCHEM (In situ High Energy X-ray Diffraction from Electrochemical interfaces). Detta projekt är ett samarbete mellan tyska och svenska forskningsgrupper som fokuserar på att använda synkrotron (röntgen) experiment för att studera elektrokemiska ytprocesser. Denna avhandling bidrar till detta projekt genom sina studier av nanotrådsväxt i porös aluminiumoxid, sin användning av optisk reflektans för att följa yt-förändringar kombinerat med röntgendiffraktion för att få kompletterande atomisk kunskap om reaktionen, samt studier av guld under elektrokatalytiska reaktioner. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/4848fc95-3bab-4b70-917f-39fc97e57a89
- author
- Linpe, Weronica LU
- supervisor
-
- Edvin Lundgren LU
- Johan Gustafson LU
- Gary Harlow LU
- opponent
-
- Prof. Dr. Kunze-Liebhäuser, Julia, University of Innsbruck
- organization
- publishing date
- 2021
- type
- Thesis
- publication status
- published
- subject
- keywords
- Electrochemistry, X-ray methods, In situ, synchrotron radiation, Ex situ, Single crystal, polycrystalline, aluminium oxide, Au, Pd, Pt, Sn, Super duplex stainless steel., Fysicumarkivet A:2021:Linpé
- pages
- 238 pages
- publisher
- Lund University
- defense location
- Rydbergsalen, Fysikum, Sölvegatan 14, Lund Join via zoom: https://lu-se.zoom.us/j/68239306056?pwd=VG9IV0J1b1h0KzAyMVcvR3pmSTlxZz09 passcode 2020
- defense date
- 2021-06-04 09:00:00
- ISBN
- 978-91-7895-749-1
- 978-91-7895-750-7
- language
- English
- LU publication?
- yes
- id
- 4848fc95-3bab-4b70-917f-39fc97e57a89
- date added to LUP
- 2021-04-27 09:51:28
- date last changed
- 2023-09-06 10:10:17
@phdthesis{4848fc95-3bab-4b70-917f-39fc97e57a89,
abstract = {{This thesis shows how various light-based in situ techniques can be used to follow different surface electrochemical processes such as electrochemical deposition into Nanoporous Anodic Aluminium Oxide (NP-AAO) templates and the surface structure of electrodes. Techniques based on both x-rays and visible light were used to follow surface structures and compositions, in situ. The samples were also<br/>investigated with ex situ techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and various other techniques. Templated electrodeposition processes, which can be used for growing various nanostructures with applications in for example gas sensors, catalysts, electrocatalysts and colouring of metal products were studied. Cyclic voltammetry (CV) for investigating electrooxidation and corrosion of model systems as well as real industrial materials was combined with Surface X-ray Diffraction and 2-Dimensional Surface Optical Reflectance.<br/><br/>Electrochemical deposition of Sn, Pd and Au into NP-AAO was investigated with both in situ and ex situ methods to gain information about the deposition process, the influence of the NP-AAO template on the growth of the nanostructures and the chemical and crystallographic nature of the grown nanostructures. For the Sn, it was possible to determine that the grown nanostructures were metallic with a beta-Sn crystal structure and a compression of the nanostructures due to the confinement of the pores were measured. Both the Pd and the Au nanostructures were constructed<br/>of crystalline grains with grain sizes in the range of the pore diameter. A compressive and tensile strain could be measured across and along the<br/>nanostructures, respectively. <br/><br/>The combination of 2-Dimensional Surface Optical Reflectance (2D-SOR), an optical microscope, with a modified electrochemical cell, was investigated through cyclic voltammetry measurements on Au, Pd and Super Duplex Stainless Steel and anodization of aluminium. The measured reflectance could be correlated with characteristic features in the CV curve corresponding to oxidation and reduction of the surface. By combining 2D-SOR with High Energy Surface X-ray Diffraction (HESXRD) during CV measurements the reflectance could be correlated with the<br/>atomic changes of the Au(111) surface. It was also shown that 2D-SOR could detect monolayer changes of the surface, due to its sensitivity to the increased electron density of the Herringbone reconstruction, a rearrangement of the atoms in the topmost layer of the Au(111) single crystal surface. By applying this method to polycrystalline samples, it was possible to follow how differently oriented grains react differently during the same experimental conditions, showing the possibility for 2D-SOR to image inhomogeneous surfaces.<br/><br/>The Au(111) single crystal was further studied using CV and potential stepping going into the oxygen evolution reaction (OER). The combined HESXRD and 2D- SOR measurements detected a roughening of the surface as it was oxidized and during the OER. These measurements also suggest that the oxide on the Au(111) single crystal is amorphous, due to the lack of oxidation peaks in the measured diffraction pattern. With X-ray photoelectron spectroscopy measurements, it could be shown that sulphate species absorb on the surface before any oxide is detected,<br/>the oxide is then formed and detected as the sulphate desorbs. <br/><br/>The possibility to follow and understand these different surface reactions gives knowledge which in the future could be used for example for the continued development of fuel cells, the development of devices, sensors, catalysts and to develop more corrosion-resistant materials.}},
author = {{Linpe, Weronica}},
isbn = {{978-91-7895-749-1}},
keywords = {{Electrochemistry; X-ray methods; In situ; synchrotron radiation; Ex situ; Single crystal; polycrystalline; aluminium oxide; Au; Pd; Pt; Sn; Super duplex stainless steel.; Fysicumarkivet A:2021:Linpé}},
language = {{eng}},
publisher = {{Lund University}},
school = {{Lund University}},
title = {{Using Light to Probe Surface Electrochemical Processes}},
url = {{https://lup.lub.lu.se/search/files/97180671/Weronica_Linp_WEBB.pdf}},
year = {{2021}},
}