The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds as promising high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion and charge compensation by transition-metal (TM) ions. The additional capacity is provided through charge compensation by oxygen redox chemistry and some oxygen loss. It has been reported previously that oxygen redox occurs in O 2p orbitals that interact with alkali ions in the TM and alkali-ion layers (that is, oxygen redox occurs in compounds containing Li-O(2p)-Li interactions). Na[MgMn]O exhibits an excess capacity and here we show that this is caused by oxygen redox, even though Mg resides in the TM layers rather than alkali-metal (AM) ions, which demonstrates that excess AM ions are not required to activate oxygen redox. We also show that, unlike the alkali-rich compounds, Na[MgMn]O does not lose oxygen. The extraction of alkali ions from the alkali and TM layers in the alkali-rich compounds results in severely underbonded oxygen, which promotes oxygen loss, whereas Mg remains in Na[MgMn]O, which stabilizes oxygen.

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Recent findings revealed that surface oxygen can participate in the oxygen evolution reaction (OER) for the most active catalysts, which eventually triggers a new mechanism for which the deprotonation of surface intermediates limits the OER activity. We propose in this work a "dual strategy" in which tuning the electronic properties of the oxide, such as LaSrCoO, can be dissociated from the use of surface functionalization with phosphate ion groups (P) that enhances the interfacial proton transfer. Results show that the P functionalized LaSrCoO gives rise to a significant enhancement of the OER activity when compared to LaSrCoO and LaCoO. We further demonstrate that the P surface functionalization selectivity enhances the activity when the OER kinetics is limited by the proton transfer. Finally, this work suggests that tuning the catalytic activity by such a "dual approach" may be a new and largely unexplored avenue for the design of novel high-performance catalysts.

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Detailed EXAFS (extended X-ray absorption fine structure spectroscopy) measurements have been collected for two nanocrystalline forms of zirconia, namely, dense films of yttria-stabilized cubic zirconia (YSZ) and tetragonal phase powders of pure ZrO 2 . Zr and Y K edge EXAFS spectra for the YSZ films with grain sizes of 6, 15, and 240 nm showed no major differences with the corresponding spectra of the bulk counterpart. This is clear proof that these nanocrystalline films exhibit similar levels of disorder to that of large crystals. In particular, there is no support for the view that the intergrain regions are highly disordered, and the present work is consistent with recent EXAFS studies of other nanocrystalline oxides (SnO 2 and ZnO) and metals (Cu). The pure nanocrystalline ZrO 2 powders were produced by calcining zirconium hydroxide, a widely used method of synthesising ZrO 2 . The Zr K edge EXAFS of the powders, with grain sizes of 10 and 20 nm, yielded spectra in which the signal was strongly attenuated in comparison to the EXAFS bulk of ZrO 2 . A significant feature is the dramatically reduced amplitude of the second peak in the Fourier transform, which is due to the Zr-Zr correlation. This feature is often interpreted as evidence of high levels of disorder in nanocrystalline materials. However, using the results from other techniques, notably, NMR measurements, it is argued that the samples contained amorphous material due to an incomplete conversion of the hydroxide precursor. Overall, the studies of the two types of nanocrystalline zirconia emphasize the need for careful characterization of the materials prior to the application of techniques such as EXAFS, which provide an average picture of the local structure.

Nanocrystalline MgO has been sol-gel manufactured to give a range of crystallite sizes from 1.8 to 35 nm as determined by powder X-ray diffraction. A multinuclear magnetic resonance approach using 13 C, 17 O, and 25 Mg provides information on the atomic scale structure. It is found that despite extensive hydrolysis that -CH 3 fragments persist until extensive calcination has been performed. In 17 O magic angle spinning NMR spectra three signals are detected that are assigned to MgO-like, a surface species, and a unit also like MgO but with carbon as the third nearest neighbor, demonstrating the high sensitivity of the 17 O chemical shift to local structure and its ability to detect medium-range order.

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