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Due to the state transition of variable-valence ions during the solid-state reaction, the reaction mechavnism is complex. As one of the function materials in supercapacitors and catalysts, there is much research on the property and function mechanism of MnCo 2 O 4. But it's necessary to study the chemical reaction and a productive method for realizing wide application. In this paper, solid-state reaction method with high efficiency was applied to produce MnCo 2 O 4 and investigated the reaction process of oxides, the formation mechanism of MnCo 2 O 4 , respectively. Thermodynamic and roasting experiments of single metal oxides demonstrated the actual stability of MnO 2 and Co 3 O 4 in the air. Furthermore, Roasting experiments on different metal oxide systems revealed Mn 2 O 3 and Mn 3 O 4 were the effective reactants of MnCo 2 O 4 , which reacted with Co 3 O 4 respectively to produce MnCo 2 O 4. Moreover, the optimum condition of the preparation of MnCo 2 O 4 was determined to be 1150 ℃ with a 90-minute in a 3:2 molar ratio of MnO 2 and Co 3 O 4. MnCo 2 O 4 were composed of Mn2+, Mn3+, Co2+, and Co3+, the property of Mn-O and Co-O bonds at 1.50 Å and 1.54 Å all including tetrahedral and octahedral sites with a bond length of 1.9–1.92 Å and 1.93–1.94 Å, respectively. Mn and Co atoms are located at octahedral sites with two coordinated distances: Me Oh -Me Oh , Me Oh -Me Td. The migration behavior of elements in MnO 2 -Co 3 O 4 diffusion couple was found to manganese move to Co-based and generate a porous MnCo 2 O 4 at the interface. The formation mechanism of spinel-type MnCo 2 O 4 was explained: While Co 3 O 4 was activated, Mn4+ was decomposed to Mn2+ and Mn3+ in the oxidation roasting process. Further, Mn2+ and Mn3+ replaced part of tetrahedral Co2+ and octahedral Co3+ in [Co(2+)][Co(3+)] 2 O 4 to form a spinel-type [Mn(2+)Co(2+)][Mn(3+)Co(3+)] 2 O 4. [Display omitted] • Mn 2 O 3 and Mn 3 O 4 can directly react with Co 3 O 4 to produce MnCo 2 O 4 by roasting. • Mixing-valence Mn and Co atoms are located at octahedral sites with two coordinated distances: Me Oh -Me Oh , Me Oh -Me Td (Me= Mn, Co) • The process of atomic substitution is a pivotal step in the formation of MnCo 2 O 4 [ABSTRACT FROM AUTHOR]

Highlights: [•] The visible-light-induced In2O3/rectorite was prepared by a facile sol–gel method. [•] The specific surface area of the In2O3/rectorite was larger than that of pure In2O3. [•] The photocatalyst shows excellent photocatalytic activity under visible-light irradiation. [ABSTRACT FROM AUTHOR]

• Oxygen vacancy-enriched Co 3 O 4 nanowire arrays decorated on nickel foam is used for a dendrite-free Li metal anode. • The O vacancy -enriched metal oxides meet the ionic/electronic diffusion kinetics at the initial stage of lithium deposition. • The lithium utilization rate of red-Co 3 O 4 /NF at the current density of 1 mA cm−2 is 98.5%. [Display omitted] Lithium metal as a promising anode material has been widely applied in many advanced high-energy density batteries. However, uncontrollable Li dendrite formation and infinite volume expansion in lithium anode result in short lifespan and severe safety hazards. In this contribution, we report that utilization of oxygen vacancy-enriched Co 3 O 4 nanowire arrays as lithiophilic material is an effective strategy to obtain ultra-long stable lithium metal anode. The oxygen vacancy can serve as electronic charge carrier to facilitate electron transfer. Moreover, it can induce the generation of local electric field to accelerate lithium ions migration and enable uniform Li+ distribution, which are beneficial for homogeneous lithium nucleation. Combining the excellent ionic/electronic diffusion and the volume buffer offered by the nanowire arrays, the obtained electrode shows high coulombic efficiency of 98.5% at 1 mA cm−2 for 230 cycles. [ABSTRACT FROM AUTHOR]