Abstract
Electrochemistry is a promising building block for the global transition to a sustainable energy market. Particularly the electroreduction of CO2 and the electrolysis of water might be strategic elements for chemical energy conversion. The reactions of interest are inner-sphere reactions, which occur on the surface of the electrode, and the biased interface between the electrode surface and the electrolyte is of central importance to the reactivity of an electrode. However, a potential-dependent observation of this buried interface is challenging, which slows the development of catalyst materials. Here we describe a sample architecture using a graphene blanket that allows surface sensitive studies of biased electrochemical interfaces. At the examples of near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and environmental scanning electron microscopy (ESEM), we show that the combination of a graphene blanket and a permeable membrane leads to the formation of a liquid thin film between them. This liquid thin film is stable against a water partial pressure below 1 mbar. These properties of the sample assembly extend the study of solid–liquid interfaces to highly surface sensitive techniques, such as electron spectroscopy/microscopy. In fact, photoelectrons with an effective attenuation length of only 10 Å can be detected, which is close to the absolute minimum possible in aqueous solutions. The in-situ cells and the sample preparation necessary to employ our method are comparatively simple. Transferring this approach to other surface sensitive measurement techniques should therefore be straightforward. We see our approach as a starting point for more studies on electrochemical interfaces and surface processes under applied potential. Such studies would be of high value for the rational design of electrocatalysts.
Highlights
The solid−liquid interface plays an important role in technical processes like electroplating, etching, or electrocatalysis as well as biological and environmental processes such as corrosion, ice formation, or transport phenomena across lipid membranes
CVD graphene from Graphenea is transferred as a single layer of graphene (SLG), a bilayer of graphene (BLG), or a single layer supported by PMMA (SLGp) in a wet chemical process
We demonstrated a way to investigate the solid−liquid interface by using a sample preparation method that can be done in any chemical lab
Summary
The solid−liquid interface plays an important role in technical processes like electroplating, etching, or electrocatalysis as well as biological and environmental processes such as corrosion, ice formation, or transport phenomena across lipid membranes. At the heart of our approach is a sample preparation that can be done in any chemical lab (Figure 1): we use solid polymer electrolytes for the transport of ions and water, as others have done before,[14−17] but we cover the polymer membrane or the topping layer of material with graphene (compare Figure 1).
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