Electrochemical Surface Oxidation of Copper Studied by in Situ Grazing Incidence X-ray Diffraction

Grazing incidence X-ray diffractometry (GIXRD) can deliver integral information on the structure and chemistry of surface near regions, which can be beneficial for functional materials related to interfacial reactions. Here, we present an in situ laboratory GIXRD setup for electrochemical experiments. The method is capable of directly correlating changes of the crystalline surface structure to the electrochemical conditions. It combines cyclovoltametric (CV) and chronoamperometric (CA) curves of crystalline samples, which can be recorded over the entire pH range, with simultaneous GIXRD measurements. The stepwise oxidation of polycrystalline copper in alkaline medium acts as an example to prove the functionality of the setup. In situ GIXRD measurements during CA experiments reveal a stepwise oxidation mechanism of metallic Cu to Cu²⁺ involving crystalline cuprite (Cu₂O) intermediates. The results highlight the importance of conducting in situ experiments under controlled environments in order to track transient states even for a comparable simple oxidation reaction.