In Situ Probing of the Interfacial Forces at Play on Catalytic Gold Surfaces

Electrocatalysis is one of the green energy technologies which employs the use of chemical reactions to convert an unwanted feedstock into a useful energy product. The most common electrocatalysts under an investigation like Pt, Au, Cu etc. are both expensive and unpredictable due to the dynamic nature of their surface morphologies during catalysis. The recent emphasis on the surface structure of catalyst due to the electrode-electrolyte (solid-liquid) interface highlights the complexity of the surface under study and the differences that arise due to electrolyte compositions. Probing catalytic surfaces in the solid-liquid interface can provide useful information about the surface structure and composition of different ionic species (adsorbed on the catalyst surface).<br/>In this work, we highlight the use of the in-situ Electrochemical-AFM technique to observe the local changes on gold catalyst surfaces during catalysis. In addition to local topographical information, our scanning probe also maps the local nano-mechanical properties of the catalyst under study. We measure the adhesion force between the probe and the Au catalyst under applied potentials in electrochemical conditions. These in-situ adhesion force measurements can then be exploited to learn the work of adhesion which provides useful information about the electrostatic, Vander Waals, and Electric Double Layer forces under play on the catalyst surface. To highlight the important differences in the catalytic system, we study the behavior of both polycrystalline gold film on Si substrates and single crystalline gold nano-triangles on ITO substrate in sulfate-based electrolytes. This work further highlights the nanoscopic and microscopic inhomogeneity of the solid-liquid interface structure.