Environment-Dependent Radiation Damage in Atmospheric Pressure X-ray Spectroscopy

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Weatherup, RS 
Wu, CH 
Escudero, C 
Pérez Dieste, V 
Salmeron, MB 

Atmospheric pressure x-ray spectroscopy techniques based on soft x-ray excitation can provide interface-sensitive chemical information about a solid surface immersed in a gas or liquid environment. However, x-ray illumination of such dense phases can lead to the generation of considerable quantities of radical species by radiolysis. Soft x-ray absorption measurements of Cu films in both air and aqueous alkali halide solutions reveal that this can cause significant evolution of the Cu oxidation state. In air and NaOH (0.1M) solutions, the Cu is oxidized towards CuO, whilst the addition of small amounts of CH3OH to the solution leads to reduction towards Cu2O. For Ni films in NaHCO3 solutions, the oxidation state of the surface is found to remain stable under x-ray illumination, and can be electrochemically cycled between a reduced and oxidized state. We provide a consistent explanation for this behavior based on the products of x-ray induced radiolysis in these different environments, and highlight a number of general approaches that can mitigate radiolysis effects when performing operando x-ray measurements.

0306 Physical Chemistry (incl. Structural), 0299 Other Physical Sciences
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Journal of Physical Chemistry B
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American Chemical Society
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (656870)
R.S.W. acknowledges a Research Fellowship from St. John’s College, Cambridge and a EU Marie Skłodowska-Curie Individual Fellowship (Global) under grant ARTIST (no. 656870) from the European Union’s Horizon 2020 research and innovation programme. This work was supported by the Office of Basic Energy Sciences (BES), Division of Materials Sciences and Engineering, of the U.S. Department of Energy (DOE) under Contract DE-AC02-05CH11231, through the Chemical and Mechanical Properties of Surfaces, Interfaces and Nanostructures program and through work performed at the Advanced Light Source and Molecular Foundry user facilities of the DOE Office of Basic Energy Sciences.