The rapid and effective transfer of chemical reactants to solid surfaces through a mesoporous structure is essential for enhancing the catalytic performance of nanomaterials. Such materials are essential for realizing durable, nonpreciousmetal-based bifunctional electrocatalysts for rechargeable Zn−air batteries. Herein, highly reactant-accessible and mesoporous ZnMn 2 O 4 nanospheres have been prepared via solvothermal synthesis. The nanospheres demonstrate excellent catalytic activity toward the oxygen reduction reaction and the oxygen evolution reaction in an aqueous alkaline solution. Moreover, compared with commercial 20 wt % platinum on carbon black, IrO 2 , and RuO 2 , the mesoporous ZnMn 2 O 4 catalyst exhibits lower charge− discharge voltage gaps, good cycling stability, and improved round-trip efficiency. The enhanced electrochemical performance of the developed catalyst is attributed to the high specific surface area, numerous reaction sites by defective O 2 − (O ads ) species, and sufficient structural stability of the ZnMn 2 O 4 material. The achievements presented in this work are of great importance for the development of outstanding non-noble spinel electrocatalysts for Zn−air batteries.

Summary Hierarchical micro/nanostructures are believed to be magnificent electrocatalyst materials capable of competing with noble metals and the most expensive catalyst materials for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Mn2V2O7‐based hierarchical spiked ball structures (MVO SBs) were synthesized using a simple hydrothermal technique as a bifunctional oxygen catalyst for rechargeable Zn‐air batteries. The linear sweep voltammetry by a rotating disc electrode was used to investigate the ORR and OER properties and their mechanisms, and the charge transfer mechanism was also studied by electrochemical impedance spectroscopy analysis. When compared with platinum with carbon black (Pt/C), the MVO SB catalyst material exhibited comparable ORR and OER properties. Furthermore, the MVO SB material revealed a 4e− transfer pathway in an electrolyte solution. Furthermore, the prepared MVO SB material demonstrated a lower charge‐discharge voltage gap when compared with Pt/C material, which is lower than 180 mV at 45 mA cm−2. The cycling test result of MVO SB catalyst sample revealed excellent cycling stability over 50 charging and discharging cycles (~800 min) than the Pt/C sample (30 cycles [~520 min]). The good catalytic activity and excellent structural stability of the MVO SB material are especially due to the more active sites enhanced by the unique spiked ball‐like morphology and high specific surface area (11.70 m2 g−1) properties. The achieved results suggest that the synthesized catalyst material could be employed as an oxygen catalyst material for rechargeable Zn‐air batteries.

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Metal oxides have been considered and investigated as alternative anodes for use in lithium ion batteries. The research focus is on two different mechanism groups: intercalation–deintercalation reaction and conversion (redox) reaction. The intercalation–deintercalation mechanism is that transition metal oxides and other compounds with a multidimensional layer structure can reversibly intercalate lithium ions into the lattice without destroying their crystal structure. While conversion mechanism usually produces metallic nanoparticles embedded in an insulating Li2O matrix and the shows generally much higher theoretical capacity than that of already-commercialized graphite. Among the metal oxides, tungsten oxides (WO2, WO3, and WO3-x H2O) as one of the important metal oxides with respect to physicochemical properties, have been extensively investigated for such applications as gas sensors, photocatalysis, electrochromic devices, electronic devices, dye-sensitized solar cells, supercapacitors, and lithium ion batteries. Interestingly, the tungsten oxides have better electronic conductivity (10–10-6 S cm-1) than some of the other oxides; in addition, they also rely on designing a nanostructured particle with a small radius and right crystalline phase for fast lithium-ion insertion and superior electrochemical performance. From this point of view, a wide variety of approaches have been pursued over the years for the synthesis of tungsten oxides, such as nanoparticles, nanowires, nanorods, and nanoflowers using various approaches which include a hydrothermal reaction, combustion process, sol–gel process, solution-phase reaction, template directed method, mechanochemical activation, and hot-wire chemical vapor deposition (HWCVD) method. However, most of the previous approaches led to the formation of monoclinic W18O49, hexagonal WO3, and WO3-xH2O nanostructures. There have been very few studies on nanostructured monoclinic WO3 (m-WO3). In this study, we will present a facile hydrothermal process that obtains cauliflower-like carbon-coated WO3 oxide with a high rate-capability and good cycling performance for lithium-ion batteries. The motivation in this study is to explore the possibility of using m-WO3 as an anode material for lithium-ion batteries and to elucidate its reaction mechanism with lithium during the charge–discharge process.