To develop materials with enhanced electrochemical properties, an original synthesis strategy based on the exfoliation and restacking of manganese and cobalt layered transition metal oxides has been explored. Successful exfoliation yielded "building nanoblocks", which were further reassembled in mixed nanocomposites, by modifications of electrostatic interactions in solution. Three methods were tested, differing by the acidification procedure and time of mixing. The restacking conditions play a key role on the microstructural homogeneity of the nanocomposites. Such a nanocomposite approach marrying a good electronic conductor (cobalt oxyhydroxide) with a pseudocapacitive material (manganese oxide) should thus be very beneficial for development of highly efficient pseudocapacitors.
To design novel layered materials, bottom-up strategy is very promising. It consists of (1) synthesizing various layered oxides, (2) exfoliating them, then (3) restacking them in a controlled way. The last step is based on electrostatic interactions between different layered oxides and is difficult to control. The aim of this study is to facilitate this step by predicting the isoelectric point (IEP) of exfoliated materials. The Multisite Complexation model (MUSIC) was used for this objective and was shown to be able to predict IEP from the mean oxidation state of the metal in the (hydr)oxides, as the main parameter. Moreover, the effect of exfoliation on IEP has also been calculated. Starting from platelets with a high basal surface area over total surface area, we show that the exfoliation process has no impact on calculated IEP value, as verified with experiments. Moreover, the restacked materials containing different monometallic (hydr)oxide layers also have an IEP consistent with values calculated with the model. This study proves that MUSIC model is a useful tool to predict IEP of various complex metal oxides and hydroxides.
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