Potentialabhängige Morphologie von Kupferkatalysatoren während der Elektroreduktion von CO 2 , ermittelt durch In‐situ‐Rasterkraftmikroskopie

Structure of the (Bi)carbonate Adlayer on Cu(100) Electrodes

(Bi)carbonate adsorption on Cu(100) in 0.1 M KHCO₃ has been studied by in situ scanning tunneling microscopy. Coexistence of different ordered adlayer phases with ( 2 ${\sqrt{2}}$ ×6 2 ${\sqrt{2}}$ )R45° and (4×4) unit cells was observed in the double layer potential regime. The adlayer is rather dynamic and undergoes a reversible order-disorder phase transition at 0 V vs. the reversible hydrogen electrode. Density functional calculations indicate that the adlayer consists of coadsorbed carbonate and water molecules and is strongly stabilized by liquid water in the adjacent electrolyte.

Insight into Structural Evolution, Active Site and Stability of Heterogeneous Electrocatalysts

The structure-activity correlation study of electrocatalysts is essential for improving conversion from electrical to chemical energy. Recently, increasing evidences obtained by operando characterization techniques reveal that the structural evolution of catalysts caused by the interplay with electric fields, electrolytes or reactants/intermediates brings about the formation of real active sites. Hence, it is time to summarize the structural evolution-related research advances and envisage their future developments. In this minireview, we first introduce the fundamental concepts associated with structural evolution ( e.g., catalyst, active site/center and stability/lifetime) and their relevance. Then, the multiple inducements of structural evolution and advanced operando characterizations are discussed. Lastly, a brief overview of structural evolution and its reversibility in heterogeneous electrocatalysis, especially for representative electrocatalytic oxygen evolution reaction (OER) and CO 2 reduction reaction (CO 2 RR), along with key challenges and opportunities, is highlighted.

Identifying Structure-Selectivity Correlations in the Electrochemical Reduction of CO2 : A Comparison of Well-Ordered Atomically Clean and Chemically Etched Copper Single-Crystal Surfaces

The identification of the active sites for the electrochemical reduction of CO2 (CO2 RR) to specific chemical products is elusive, owing in part to insufficient data gathered on clean and atomically well-ordered electrode surfaces. Here, ultrahigh vacuum based preparation methods and surface science characterization techniques are used with gas chromatography to demonstrate that subtle changes in the preparation of well-oriented Cu(100) and Cu(111) single-crystal surfaces drastically affect their CO2 RR selectivity. Copper single crystals with clean, flat, and atomically ordered surfaces are predicted to yield hydrocarbons; however, these were found experimentally to favor the production of H2 . Only when roughness and defects are introduced, for example by electrochemical etching or a plasma treatment, are significant amounts of hydrocarbons generated. These results show that structural and morphological effects are the key factors determining the catalytic selectivity of CO2 RR.