The performance of an electrocatalyst (its activity, selectivity, and stability) is strongly dependent on the electrode structure and composition, particularly in the near surface region. A successful approach in trying to understand the impact of structure is the use of well-defined model electrodes such as single crystals, to isolate how various changes in structure and composition impact upon the catalyst behavior. Surface x-ray diffraction gives the average surface structure of an isolated facet, whereas real catalysts often contain multiple facets and edge sites. This contribution will discuss two recent advances in the determination of electrocatalyst structure:

a) The application of high energy surface x-ray scattering to quickly map out large volumes of 3D reciprocal space and then extract crystal truncation rods. These truncation rods can then be used to determine atomic coordinates of surface atoms, in operando. I will present examples during methanol oxidation on both Pt(111) and Au(111) surfaces.

b) I will then discuss how we can complement single crystal studies by using coherent Bragg diffraction imaging (and some of the challenges) to look at single nanoparticle electrocatalysts and ceate strain maps to identify important facets and sites.