In quest of a stable structure throughout redox reactions, an approach of B-site ordering (0D arrangement) of cations in double perovskites is adopted. Here, we report B-site cation ordering in double perovskite Sr 2 CoMoO 6-δ (DP-SCM) that tends to a favorable rock salt structure (0D arrangement). The synergy of Co/Mo having good redox ability further facilitates high oxygen mobility. A high content of oxygen vacancy examined using XPS and EPR facilitates a high oxygen anion diffusion rate (2.03 × 10 −11 cm 2 s −1 ). Moreover, fast kinetics (ΔE P ≈ 0.013 V@ 1 mV s −1 ) of charge storage prohibits any phase transformation reflecting the excellent cycle life (125% retention up to 5000 cycles). Such fast kinetics is majorly furnished from anion intercalation with little involvement from double layer mechanism (C dl ≈ 42.1 F g −1 ). DP-SCM achieves a resultant capacitance of 747 F g −1 @ 1 A g −1 with a rate capability of 56% up to 10 A g −1 . Motivated by outstanding performance of DP-SCM electrodes, a symmetric cell is assembled with a 1.4 V operating potential that delivers a high energy density of 64 Wh kg −1 @855 W kg −1 . This work on double perovskites suggests that the advance understanding of cation ordering and charge storage mechanism can provide a new direction to fabricate highly capacitive electrode materials.

New Dion−Jacobson (n = 3) layered perovskites, A′Cd 2 Nb 3 O 10 (A′ = Rb, Cs), have been synthesized by a solid-state method. Powder X-ray diffraction measurements confirm the noncentrosymmetric orthorhombic (space group Ima2) structures for both rubidium-and cesium-containing layered oxides. The distorted octahedral coordination of the d 0 metal cations (Nb 5+ ) coupled with the increased covalency in the lattice by the introduction of d 10 metal cations (Cd 2+ ) is responsible for the acentric structures. The resulting second-harmonicgeneration (SHG) efficiencies of the polycrystalline samples (size 45−63 μm) using 1064 nm radiation reveal comparable values for CsCd 2 Nb 3 O 10 and nearly 5 times higher output values for RbCd 2 Nb 3 O 10 with respect to potassium dihydrogen phosphate. These structures were further confirmed from transmission electron microscopy and Raman spectroscopy measurements. The optical characteristics show interesting variations to the expected photocatalytic activities. Ion-exchange reactions result in the synthesis of proton-and lithium-containing oxides, which are otherwise inaccessible by direct solid-state reactions. The mobilities of the interlayer ions have also been confirmed by ionic conductivity measurements.

The research work conducted mainly on the reduction reaction of NOx, the oxidation reaction of CO, and hydrocarbons, electro‐catalysis of oxygen in alkaline medium, and photocatalytic water splitting has proved excellent catalytic behavior of perovskite oxides.[16–23] Although only a few reports published usages of the perovskite oxides as catalysts for the organic transformation such as catalytic hydrogenation, Ullmann, Sonogashira reactions, and Suzuki couplings.[24–26] Yoon et al. have prepared K2CO3 based LaMn1‐xCuxO3 perovskite oxide as a potential catalyst and discussed their mechanistic aspects in various reactions occurring at room temperature.[27] Recently, Wu and Ajayan group has demonstrated the relationship between stoichiometry and activity of pure and B‐site substituted layered perovskite oxide in the decomposition reaction of isopropanol by considering Sr2Sn1‐xRuxO4 (0≤x≤1) as catalyst.[28] In this scenario, present work aims to summarize the contribution of perovskite oxides as catalyst in numerous organic syntheses and catalysis, photocatalysis, and electrocatalysis reactions.

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The microwave-assisted method is an appropriate route; to overcome the energy barrier for stabilizing perovskite structured based inorganic-organic-hybrid materials. The motivation for using the microwave-assisted method in material science as an effective heating technique results from improvement in the topochemical modification of layered perovskite oxides. The microwave-assisted method causes a fall in time duration from days to hours/minutes and produces good quality products with high crystallinity. Inorganic-organic-hybrids can be derived easily by the stepwise modification of layered perovskites. These modification techniques involve proton exchange, grafting, intercalation, and exfoliation steps. The microwave synthesized inorganic-organic-hybrid materials are in high demand due to their various interesting properties, potential catalytic, optical, composite, magnetic, and electronic, making them useful for technological applications.