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[Display omitted] • Nanosized Ag@Co 3 O 4 nanoflower were synthesized by chemical deposition. • Small crystallite size and silver deposition enhanced electrochemical performance. • Highly stability upto 500 h with lower overpotential. The studies of core–shell nanoparticles have gained significant interests due to the high stability and probable template to form a core–shell complex by coating on them with organic or inorganic substances. The silica nanoparticle covered with cobalt is especially important because it has a chemically stable core. Co 3 O 4 -NF was synthesized by the calcination of Co(OH) 2 @SiO 2 under atmospheric air for oxygen reduction and evolution reactions. After calcination, Ag deposition was performed to produce Ag@Co 3 O 4 -NF and their surface area reduces from 125.68 to 108.12 m2/g. The crystallanity and morphological features were observed by the X-ray diffraction (XRD) and scanning electron microscopy (SEM). Furthermore, Ag@Co 3 O 4 -NF catalysts exhibited superior electrochemical performance as a cathode material for Zinc-air batteries. The cyclic test for charging and discharging was performed for 500 h revealing Ag@Co 3 O 4 -NF a potential catalyst, having splendid stability for the OER and ORR. [ABSTRACT FROM AUTHOR]

The wide structural versatility of the Metal-Organic Framework (MOF) is considered to be potential catalysts. In this work, [Mn (BDC). nDMF] n was synthesized by the reaction of 1,4-benzene dicarboxylic acid (1,4-BDC) with Manganese (II) nitrate using a solvothermal method. The [Mn (BDC). nDMF] n crystals were calcined for 2 h to produce Mn-MOF derived catalysts (C@MnO catalysts). The formation of MnO crystals was investigated by the X-ray diffraction (XRD) and the Raman Spectroscopy analyzed the graphitization. The resulting catalysts, C@MnO are highly porous with a high specific surface area of 291.62 m2/g at 700 °C. After calcination, Ni deposition was performed, to produce Ni@C@MnO on which Ni-atoms are deposited on the surface of MnO. The surface area reduces to 214.09 m2/g at 700 °C and the structure is distorted due to deposition. Numerous characterization techniques, including XRD, SEM, EDS, TGA, and Raman, strongly support the effective incorporation of Mn and Ni into the material frameworks. When applied as a cathode for Zinc-air battery, the Ni@C@MnO electrode delivered a high current density of 0.206 Acm−2 for the OER. The cyclic test for charging-discharging was performed for 152 cycles revealing a potential catalyst, having splendid stability for the OER and ORR. Unlabelled Image • Fabrication of carbon-coated manganese (C@MnO) catalysts by solvothermal method • Nickel deposition on C@MnO catalysts • Improved catalytic performance for the oxygen reduction and evolution reactions [ABSTRACT FROM AUTHOR]

• Fabrication of efficient bimetallic catalysts for OER. • Nickel decoration was performed on bimetallic CNT/CoNi. • Ni/CNT/CoNi exhibited excellent electrochemical performance and cycling stability. The fabrication of efficient catalysts for the oxygen evolution reactions (OER) that are required to accelerate the sluggish kinetics of metal-air batteries has attracted significant attention for application in energy conversion devices. Metal-organic frameworks (MOFs) have been recognized as potential candidates for the formation of promising catalysts. In this study, we report the formation of Ni/CNT/CoNi using bimetallic-ZIF (CoNi-ZIF) as a precursor. Bimetallic CoNi encapsulated in carbon nanotubes (CNTs) was obtained by calcinating CoNi-ZIF-67 to yield CNT/CoNi. The resulting CNT/CoNi was highly porous with a significant specific surface area of 242 m2/g. After calcination, Ni deposition on the CNT was performed and the surface area was reduced to 168.7 m2/g. Ni/CNT/CoNi was applied as a cathode material in zinc-air batteries, exhibiting excellent electrochemical performance and cycling stability. [ABSTRACT FROM AUTHOR]