Double layer · Spectroscopic investigation of the electrochemical interface for sustainable electrocatalysis

The structure of the double layer at the electrode-electrolyte interface dictates the electrocatalytic performance. A better understanding of the double layer is thus necessary for the optimization of key reactions such as the electrocatalytic hydrogen production and the CO2 electroconversion to value-added products, both of which are central to transitioning to carbon-free fuel alternatives. However, there is currently a significant lack of appropriate characterization methods to resolve this interfacial region. Meanwhile, recent results demonstrate that the models so far employed to predict the physical behavior at the double layer are incomplete. Therefore, for the field of electrocatalysis to reach its performance targets, it is critical we develop new techniques to fill this gap in our understanding of the catalyst-electrolyte interface. In this work, we propose to leverage the unique properties of X-ray photoelectron spectroscopy (XPS) and total electron yield X-ray absorption spectroscopy (TEY-XAS) in a dip-an-pull geometry to resolve the concentration and configuration of the ions and water molecules present in the double layer. Using single crystal electrodes that are well-defined surfaces, we propose to use these spectroscopic insights to verify the nature of non-specific ion-water-electrode interactions suggested by previous electrochemical and computational investigations. Once optimized, we propose to expand the application of this spectroscopic approach to electrocatalytically relevant conditions for the hydrogen evolution reaction on Pt(111) and for the CO2 reduction reaction on Au(111). The as-described methodology will not only provide unprecedented insights into the elusive contribution of the double layer during electrocatalysis, but it will also enable the standardization of a powerful characterization tool that will greatly benefit the field of surface chemistry and catalysis.