In the context of ion transfer batteries, highly oriented pyrolytic graphite (HOPG) was studied as a model in aqueous electrolytes to elucidate the mechanism of electrochemical intercalation into graphite. The local and time-dependent dimensional changes of the host material occurring during the electrochemical intercalation processes were investigated on the nanometer scale. Atomic force microscopy (AFM), combined with cyclic voltammetry, was used as an in situ analytical tool during the intercalation of perchlorate and hydrogen sulfate ions into and their expulsion from the HOPG electrodes. For the first time, a reproducible, quantitative estimate of the interlayer spacing in HOPG with intercalated perchlorate and hydrogen sulfate ions could be obtained by in situ AFM measurements. The experimental values are in agreement with theoretical expectations, only for relatively low stacks of graphene layers. After formation of stage IV, HOPG expansion upon intercalation typically amounts to 32% when tens of layers are involved but to only 14% when thousands of layers are involved. Blister formation and more dramatic changes in morphology were observed, depending on the kind of electrolyte used, at higher levels of anion intercalation.

The diffuse layer properties of modified gold electrodes under potentiostatic control have been determined by direct force measurements. These measurements have been performed with a colloidal probe consisting of a silica particle attached to the cantilever of an atomic force microscope. The gold electrodes were modified by self-assembled monolayers (SAMs) of different thickness. Additionally, the terminating functional groups of the monolayer have been varied. The interaction force profiles have been fit to the full solutions of the nonlinear Poisson-Boltzmann equation. An accurate quantitative description of the force profiles has been obtained by taking charge regulation between the surfaces into account. The diffuse layer potentials obtained from these fits were studied in dependence of the potential applied to the gold electrode. The capacitance of the SAM and the potential of zero charge (pzc) have been determined for various SAMs of different thickness and surface termination. The values obtained by our direct force measurements are in agreement with the ones reported by classical electrochemical techniques. The capacitance of the SAM depends primarily on the thickness of the monolayer and its crystalline structure. Pronounced differences in the pzc for the different functional groups have been found. These changes are related to the dipole moment of the functional group terminating the SAM. Our data are in agreement with ion adsorption, but this effect seems to be less pronounced than for bare gold electrodes.

Data on the electrical conductance, density, viscosity, and surface tension of nitrate—nitrate, nitrite—nitrite, and nitrite—nitrate mixtures have been systematically collected and evaluated. Results are given for some 71 binary mixtures over a range of compositions and temperatures. Values of the above properties for the single salts have been updated in accord with previously advanced recommendations.

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