Direct Observation of Photoinduced Higher Oxidation States at a Semiconductor/Electrocatalyst Junction
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61989592%3A15310%2F20%3A73603306" target="_blank" >RIV/61989592:15310/20:73603306 - isvavai.cz</a>
Result on the web
<a href="https://pubs.acs.org/doi/full/10.1021/acscatal.0c02789" target="_blank" >https://pubs.acs.org/doi/full/10.1021/acscatal.0c02789</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1021/acscatal.0c02789" target="_blank" >10.1021/acscatal.0c02789</a>
Alternative languages
Result language
angličtina
Original language name
Direct Observation of Photoinduced Higher Oxidation States at a Semiconductor/Electrocatalyst Junction
Original language description
Photoelectrochemical (PEC) water splitting devices using semiconductors and electrocatalysts rely on heterogeneous interfaces that drive charge separation, thus determining potential gradients that dictate the reaction efficiency. The PEC potential of the electrocatalyst depends on the chemical oxidation state of forming elements, which may strongly vary under the photoinduced charge flow. However, element-sensitive, real-time measurements of the oxidation state of the electrocatalyst are not generally possible using conventional X-ray absorption techniques. Here, we show that fixed-energy X-ray absorption voltammetry and chronoamperometry, which measure the X-ray absorption coefficient variations along with photocurrent, can follow in real time the redox kinetics of electrocatalysts. To demonstrate the validity, we investigate hematite (alpha-Fe2O3) photoanodes covered with a nickel hydroxide electrocatalyst and show that it is fully oxidized by photogenerated holes to nickel oxyhydroxide with Ni reaching a higher oxidation state (Ni-IV) than that observed under electrocatalytic oxygen evolution in dark conditions. Highly oxidized Ni results from charge accumulation in the overlayer and can be observed only in the case of thick layers (with low PEC performance). On the other hand, the average oxidation state of Ni reaches lower values, under operative conditions, for very thin layers, resulting in high PEC activity. We complete our study by presenting PEC activity and impedance spectroscopy analysis using different thicknesses of the electrocatalyst, thus giving a detailed picture of the multiple and complex charge transfer processes occurring at a semiconductor/electrocatalyst junction.
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10403 - Physical chemistry
Result continuities
Project
<a href="/en/project/EF15_003%2F0000416" target="_blank" >EF15_003/0000416: Advanced Hybrid Nanostructures for Renewable Energy Applications</a><br>
Continuities
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)
Others
Publication year
2020
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
ACS Catalysis
ISSN
2155-5435
e-ISSN
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Volume of the periodical
10
Issue of the periodical within the volume
18
Country of publishing house
US - UNITED STATES
Number of pages
12
Pages from-to
10476-10487
UT code for WoS article
000574920200017
EID of the result in the Scopus database
2-s2.0-85095420787