Copper electrocatalysts are unique in catalysing the formation of carbon-carbon bonds, an essential first step for producing C2+ products during electrochemical CO2 reduction (CO2RR). Intermittent oxidation of Cu nanocatalysts further enhances the selectivity towards C2+ products, especially ethanol, but the mechanistic understanding is limited. We developed a method for producing Cu epitaxial thin films, which provide a versatile alternative for bulk single crystals, especially under strongly restructuring conditions such as the pulsed CO2RR. Here, we will use HE-SXRD to study the structural dynamics of both the surface as well as the bulk of such films under CO2RR conditions. From these experiments, we expect to track the transition from changes in the surface structure to the formation of bulk Cu2O. The results of these experiments enable us to optimize the design/operating conditions of Cu CO2RR electrocatalysts based on a mechanistic understanding rather than empirical evidence.