oxygen evolution reaction and oxygen reduction reaction (OER and ORR) play important roles in rechargeable zinc-air battery (ZAB), whereas OER and hydrogen evolution reaction (HER) are the core reactions in EWS. [4,5] These electrochemical reactions exhibit sluggish kinetics because they require multistep protoncoupled electron transfers, which increase the overpotentials of the systems, thus causing the losses of considerable energy and long-term electrocatalytic activity. [6][7][8][9] Multifunctional electrocatalysts that efficiently catalyzes diverse electrochemical reactions (OER, HER, and ORR) have recently attracted considerable attention. Multifunctional electrocatalysts can reduce the manufacturing cost of the specific electrocatalysts for various electrochemical systems. The state-of-the-art catalysts such as Pt-based electrocatalysts (ORR and HER), IrO 2 and RuO 2 (OER) could not meet the characteristics of ideal multifunctional electrocatalysts because of high cost, non-abundancy, and non-multifunctional electrocatalytic activity. [10] Moreover, there are limited reports on the strategies for synthesizing multi functional electrocatalysts with intense activity, stability, and selectivity; [11][12][13] and this has necessitated the development of inexpensive, abundant, efficient, and stable multifunctional electrocatalysts to substitute the noble metal-based electrocatalysts.Transition metal oxides (TMOs) have been recently identified as the most promising alternatives to noble metal-based electrocatalysts because of their natural abundance, environmental sustainability, and superior thermal and chemical stabilities under different operating conditions. [14][15][16][17][18] A few promising TMOs exhibit spinel structures, especially cobalt oxide, because Co in its d 7 state with unpaired electrons enhances the activation and polarization of media and the presence of different valences encourage electron transfer during ORR, OER, and HER. Similarly, manganese oxides are inexpensive and abundant materials that promote natural OER in plants, as well as the desired four-electron pathway toward ORR; however, the poor electronic conductivity of manganese oxides limits their electrocatalytic activity. To overcome these limitations, manganese oxide can be combined with cobalt as a co-metal in the spinel structure. Further, increasing the surface area and amounts of Mn 3+ and Mn 2+ can considerably enhance the The integration of energy conversion and storage systems such as electrochemical water splitting (EWS) and rechargeable zinc-air battery (ZAB) is on the vision to provide a sustainable future with green energy resources. Herein, a unique strategy for decorating 3D tetragonal CoMn 2 O 4 on carbon cloth (CMO-U@CC) via a facile one-pot in situ hydrothermal process, is reported. The highly exposed morphology of 3D tetragons enhances the electrocatalytic activity of CMO-U@CC. This is the first demonstration of such a bifunctional activity of CMO-U@CC in an EWS system; it achieves a nominal cell voltage of 1.610 ...

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The unique physical and chemical properties of spinels have made them highly suitable electrocatalysts in oxygen evolution reaction and oxygen reduction reaction (OER & ORR). Zinc–air batteries (ZABs), which are safer and more cost-effective power sources than commercial lithium-ion batteries, hinge on ORR and OER. The slow kinetics of the air electrode reduce its high theoretical energy density and specific capacity, which limits its practical applications. Thus, tuning the performance of the electrocatalyst and cathode architecture is vital for improving the performance of ZABs, which calls for exploring spinel, a material that delivers improved performance. However, the structure–activity relationship of spinel is still unclear because there is a lack of extensive information about it. This study was performed to address the promising potential of spinel as the bifunctional electrocatalyst in ZABs based on an in-depth understanding of spinel structure and active sites at the atomic level.