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ca 2 fe 2 o 5 (cfo) is a potentially viable material for alternate energy applications. incorporation of nitrogen in ca 2 fe 2 o 5 (CFO-N) lattice modifies the optical and electronic properties to its advantage. Here, the electronic band structures of cfo and cfo-n were probed using Ultraviolet photoelectron spectroscopy (UPS) and UV-Visible spectroscopy. The optical bandgap of CFO reduces from 2.21 eV to 2.07 eV on post N incorporation along with a clear shift in the valence band of CFO indicating the occupation of N 2p levels over O 2p in the valence band. Similar effect is also observed in the bandgap of CFO, which is tailored upto 1.43 eV by N + ion implantation. the theoretical bandgaps of cfo and cfo-n were also determined by using the Density functional theory (Dft) calculations. the photoactivity of these CFO and CFO-N was explored by organic effluent degradation under sunlight. The feasibility of utilizing cfo and cfo-n samples for energy storage applications were also investigated through specific capacitance measurements. The specific capacitance of CFO is found to increase to 224.67 Fg −1 upon n incorporation. cfo-n is thus found to exhibit superior optical, catalytic as well as supercapacitor properties over cfo expanding the scope of brownmillerites in energy and environmental applications.Multifunctional brownmillerite Ca 2 Fe 2 O 5 is a promising material for energy and environmental applications such as fuel cells, supercapacitors, batteries, H 2 production and CO 2 capture, attributed mostly to its multifaceted property like those in catalysis and mixed ionic electronic conduction (MIEC) 1-5 . Presence of a visible region bandgap along with its catalytic activity also enables it as a photoactive material and most importantly as material for textile waste water remediation. There is a huge need for industrial waste water purification of the effluents from the textile industries before releasing it to water bodies. A lower cost and energy requirement pushes us to explore more efficient materials which can absorb a larger percentage of incident natural sunlight and make their impact felt on the environment 6-10 . Well known wide band gap semiconductors, such as TiO 2 and ZnO (bandgap > 3 eV), cannot perfectly match the broad ranges of solar radiation emphasizing the need to investigate new materials/composites with narrow bandgap 11 . Quite recently perovskite metal oxides, such as PbTiO 3 (2.75 eV), AgNbO 3 (2.86 eV), SrNbO 3 (1.9 eV), BiFeO 3 (2.1 eV), LaFeO 3 (2.4 eV), LaNiO 3 (2.42 eV) have been found to possess reasonable catalytic efficiency [12][13][14][15][16][17][18][19] . This encourages us to work with novel materials like oxygen deficient perovskites for sunlight-driven photocatalysis.To meet the above objectives, it is desirable to modify such structures with transition metal-N x active sites to enhance the charge transport features and hence the catalytic activity towards remediation of industrial wastewater 20,21 . Recently, Nitrogen-doped layered perovskite K 2 La 2 Ti 3 O 10 was sh...

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The oxygen storage capacity, oxygen exchange kinetics, structure and thermodynamic stability were studied for hexagonal Y0.7Tb0.3MnO3+δ in oxygen and air to assess its applicability for oxygen separation from air by a temperature-swing adsorption process.

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Structural and oxygen content changes of hexagonal HoMnO manganite at the stability boundary in the perovskite phase have been studied by X-ray diffraction and thermogravimetry using in situ oxidation and reduction processes at elevated temperatures in oxygen and air. The oxygen storage properties during structural transformation between stoichiometric Hex0 and oxygen-loaded Hex1 phases, transition temperatures and kinetics of the oxygen incorporation and release are reported for materials prepared by the solid-state synthesis and high-impact mechanical milling. Long-term annealing experiments have shown that the Hex0 (δ = 0) → Hex1 (δ ≈ 0.28) phase transition is limited by the surface reaction and nucleation of the new phase for HoMnO 15MM. The temperatures of Hex0 ↔ Hex1 transitions have been established at 290 °C and 250 °C upon heating and cooling, respectively, at a rate of 0.1° min, also indicating that the temperature hysteresis of the transition could possibly be as small as 10 °C in the equilibrium. Ball-milling of HoMnO has only a small effect on improving the speed of the reduction/oxidation processes in oxygen, but importantly, allowed for considerable oxygen incorporation in air at a temperature range of 220-255 °C after prolonged heating. The Mn 2p XAS results of the Mn valence in oxygen loaded samples support the oxygen content determined by the TG method. The magnetic susceptibility data of the effective Mn valence gave inconclusive results due to dominating magnetism of the Ho ions. Comparison of HoMnO with previously studied DyMnO indicates that a tiny increase in the ionic size of lanthanide has a huge effect on the redox properties of hexagonal manganites and that practical properties could be significantly improved by synthesizing the larger average size (Y,Ln)MnO manganites.

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