Chemical and Structural In-Situ Characterization of Model Electrocatalysts by Combined Infrared Spectroscopy and Surface X‑ray Diffraction

New diagnostic approaches are needed to drive progress in the field of electrocatalysis and address the challenges of developing electrocatalytic materials with superior activity, selectivity, and stability. To this end, we developed a versatile experimental setup that combines two complementary in-situ techniques for the simultaneous chemical and structural analysis of planar electrodes under electrochemical conditions: high-energy surface X-ray diffraction (HE-SXRD) and infrared reflection absorption spectroscopy (IRRAS). We tested the potential of the experimental setup by performing a model study in which we investigated the oxidation of preadsorbed CO on a Pt(111) surface as well as the oxidation of the Pt(111) electrode itself. In a single experiment, we were able to identify the adsorbates, their potential dependent adsorption geometries, the effect of the adsorbates on the surface morphology, and the structural evolution of Pt(111) during surface electro-oxidation. In a broader perspective, the combined setup has a high application potential in the field of energy conversion and storage

Anticaking Activity of Ferrocyanide on Sodium Chloride Explained by Charge Mismatch

Sodium chloride crystals have a strong tendency to cake, which can be prevented by treating them with the anticaking agent ferrocyanide. Using surface X-ray diffraction, we show how the ferrocyanide ion sorbs onto the {100} face of the sodium chloride crystal where it replaces a sodium ion and five surrounding chloride ions. The coverage is about 50%. On the basis of the determined atomic structure, we propose the following anticaking mechanism. Because of the charge of the ferrocyanide ions sorbed on the surface, the crystal can only continue growing by leaving an energetically unfavorable sodium vacancy, or by desorbing the ferrocyanide ion. Therefore, the ferrocyanide effectively blocks further growth of sodium chloride crystals, thereby preventing them from agglomerating and caking