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The interface of Cu͑001͒ electrode surfaces in 10 mM HCl solution was studied by in situ surface x-ray diffraction and density functional theory, focusing on the precise structure of the c͑2 ϫ 2͒ Cl adlayer formed at positive potentials. Crystal truncation rod measurements in this adsorbate phase at a potential of −0.20 V Ag/AgCl reveal distinct differences to corresponding data by Tolentino et al. ͓Surf. Sci. 601, 2962 ͑2007͔͒ for the c͑2 ϫ 2͒ Cl structure formed at the Cu͑001͒-vacuum interface. Although in both environments, the atoms in the second Cu layer exhibit a small vertical corrugation, the sign of this corrugation is reversed. Furthermore, also the Cu-Cl bond distance and the average Cu interlayer spacings at the surface differ. Ab initio calculations performed for this adsorbate system reproduce these effects-specifically the reversal of the subsurface second-layer buckling caused in the presence of coadsorbed water molecules and cations in the outer part of the electrochemical double layer. In addition, studies at more negative potentials reveal a continuous surface phase transition to a disordered Cl adlayer at −0.62 V Ag/AgCl , but indicate a substantial Cl coverage even at the onset of hydrogen evolution.

Model experiments, in which active material in the electrode is replaced with insulating ceramic particles, are used to show the importance of pure conductive additives network. Ceramic particles are chosen with particle diameter of 10 and 3 μm. Coatings with similar loading and varying levels of carbon black, graphite and polyvinylidene fluoride are fabricated, analyzed regarding electronic conductivity and investigated with a new "quasi" in-situ SEM compression method. The electronic conductivity strongly depends on porosity, inactive material amount and distribution. SEM/EDX images showed that coatings with 10 μm particles have higher porosity and denser network of conductive additives compared to 3 μm particles. Therefore, the conductive additives and binder amount should be adjusted based on the particle size distribution.

We present in situ X-ray surface diffraction studies of interface processes with data acquisition rates in the millisecond regime, using the electrochemical dissolution of Au(001) in Cl-containing solution as an example. This progress in time resolution permits monitoring of atomic-scale growth and etching processes at solid-liquid interfaces at technologically relevant rates. Au etching was found to proceed via a layer-by-layer mechanism in the entire active dissolution regime up to rates of ∼20 ML/s. Furthermore, we demonstrate that information on the lateral surface morphology and in-plane lattice strain during the electrochemical process can be obtained.