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Sodium-ion batteries have been extensively pursued as economic alternatives to Lithium-ion batteries. Investigating the polyanion chemistry, alluaudite structured Na 2 Fe II 2 (SO 4 ) 3 has been recently discovered as a 3.8 V positive electrode material (Barpanda et al, Nature Commun., 5:4358, 2014). Registering the highest ever Fe III /Fe II redox potential (vs. Na/Na + ) and formidable energy density, it has opened up a new polyanion family for sodium batteries. Exploring the alluaudite family, here we report isotypical Na 2+2x Mn II 2-x (SO 4 ) 3 (x = 0.22) as a novel high-voltage cathode material for the first time. Following low-temperature (ca. 350°C) solid-state synthesis, the structure of this new alluaudite compound has been solved adopting a monoclinic framework (s.g. C2/c) showing antiferromagnetic ordering at 3.4 K.Synergising experimental and ab-initio DFT investigation, Na 2+2x Mn II 2-x (SO 4 ) 3 has been found to be a potential high-voltage (ca. 4.4 V) cathode material for sodium batteries.

The combined local structure techniques, extended x-ray absorption fine structure and neutron pair distribution function analysis, have been used for temperatures 4< or =T< or =330 K to rule out a large Jahn-Teller (JT) distortion of the Co-O bond in La1-xSrxCoO3 for a significant fraction of Co sites (x< or =0.35), indicating few, if any, JT-active, singly occupied e_{g} Co sites exist.

Metal-organic frameworks (MOFs) are widely known for their record storage capacities of small gas molecules (H , CO , and CH ). Assembly of such porous materials onto well-known chemiresistive gas sensing elements such as SnO could be an attractive prospect to achieve novel sensing properties as this affects the surface chemistry of SnO . Cobalt-imidazole based ZIF-67 MOF was grown onto preformed SnO nanoparticles to realize core-shell like architecture and explored for greenhouse gas CO sensing. CO sensing over SnO is a challenge because its interaction with SnO surface is minimal. The ZIF-67 coating over SnO improved the response of SnO up to 12-fold (for 50 % CO ). The SnO @ZIF-67 also showed a response of 16.5±2.1 % for 5000 ppm CO (threshold limit value (TLV)) at 205 °C, one of the best values reported for a SnO -based sensor. The observed novel CO sensing characteristics are assigned to electronic structure changes at the interface of ZIF-67 and SnO .

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