In Situ Grown CoMn₂O₄ 3D‐Tetragons on Carbon Cloth: Flexible Electrodes for Efficient Rechargeable Zinc–Air Battery Powered Water Splitting Systems

Abstract

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 ...

Integrated Bifunctional Electrodes Based on Amorphous Co–Ni–S Nanoflake Arrays with Atomic Dispersity of Active Sites for Overall Water Splitting

“…In the reported reaction system, activated CC is used as a conductive substrate that simultaneously guarantees great electron transfer and physical integration of freestanding electrodes; 36 2-aminoterephthalic acid (NH 2 -TPA), a regular ligand to build metal-organic frameworks (MOFs), 37 is expected to act as spatial isolators when the dosage is far from complete for growing MOF crystals, in which they coordinate with Co/Ni ions and form hybrid metal sites in a high-dispersion manner. As for the intended addition of glucose, the hydrolysis of glucose that occurred during the hydrothermal process can generate acids 38 that interfere with the growth of Co/Ni-TPA MOFs, whereas glucose-derived polymers that have greater infinity to CC than metal ions would deposit on the external surface of CC fibers and in situ react with metal species, 39 forming NiCoO/carbon composite layers on CC fibers. The insufficient coordination between Co/Ni ions and NH 2 -TPA assisted by the strong interaction between Co/Ni ions and glucose-derived polymers, jointly induces the growth of amorphous NiCoO highly dispersed in the carbon matrix.…”

Material design and surface chemistry for advanced rechargeable zinc–air batteries

“…TEM analysis showed that the high content (mass loading) of Fe and N in the porous structure of N-OMC enhanced the ORR active areas. Zhang et al created the pores in the carbon matrix by the heat treatment of macrocyclic cucurbit [6]uril (CB [6]) and M-N-C precursors. 76 They conrmed the N-doped carbon pore structure with Fe-bond through the HAADF-STEM images.…”

“…4 Therefore, the environmentally friendly energy conversion and storage devices such as fuel cells, electrochemical water-splitting systems, and metal-air batteries have been widely studied due to their clean property. 5,6 With respect to the metal-air batteries, this system can be operated without pre-storing oxygen in the cells. It is noteworthy to mention that oxygen can be taken directly from the ambient air.…”

“…4,5 This issue increases the full-cell overpotential of the ZAB system, causing signicant energy loss. 6 In order to address these limitations in the ZABs, it is urgent to develop low-cost, efficient electrocatalysts with long-term cycle stability.…”

Ultrafast Carbothermal Shock Constructing Ni3Fe1–xCrx Intermetallic Integrated Electrodes for Efficient and Durable Overall Water Splitting

“…In addition, most of the practically available water electrolyzers work in strong acid or alkaline electrolytes . The optimal working conditions for HER electrocatalysts and OER electrocatalysts are quite different, which leads to the difficult assembly and increased cost of the electrolyzers. , Therefore, the development of the efficient electrocatalysts with HER/OER bifunctional activity from low-cost materials is highly desirable for simplifying the system and reducing the cost of the practical water electrolyzers. − To date, although some of the reported bifunctional electrocatalysts have been applied in overall water splitting, there are still challenges hindering their application and remaining to be solved.…”