Phase and composition controllable synthesis of cobalt manganese spinel nanoparticles towards efficient oxygen electrocatalysis

Abstract

Spinel-type oxides are technologically important in many fields, including electronics, magnetism, catalysis and electrochemical energy storage and conversion. Typically, these materials are prepared by conventional ceramic routes that are energy consuming and offer limited control over shape and size. Moreover, for mixed-metal oxide spinels (for example, CoxMn3−xO4), the crystallographic phase sensitively correlates with the metal ratio, posing great challenges to synthesize active product with simultaneously tuned phase and composition. Here we report a general synthesis of ultrasmall cobalt manganese spinels with tailored structural symmetry and composition through facile solution-based oxidation–precipitation and insertion–crystallization process at modest condition. As an example application, the nanocrystalline spinels catalyse the oxygen reduction/evolution reactions, showing phase and composition co-dependent performance. Furthermore, the mild synthetic strategy allows the formation of homogeneous and strongly coupled spinel/carbon nanocomposites, which exhibit comparable activity but superior durability to Pt/C and serve as efficient catalysts to build rechargeable Zn–air and Li–air batteries.

Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems

“…89 As shown in Fig. 3, this synthesis process involves a room-temperature oxidation precipitation of Mn/Co salts with NH 3 H 2 O in an air atmosphere, followed by crystallisation into spinels at 180 1C.…”

Mn3O4@CoMn2O4–CoxOyNanoparticles: Partial Cation Exchange Synthesis and Electrocatalytic Properties toward the Oxygen Reduction and Evolution Reactions

“…(7)(8)(9)(10)(11)(12)(13)(14) Among transition metal oxides, Mn-based oxides and particularly spinels have shown outstanding performance for ORR and, to a minor extent, for OER. (7,(15)(16)(17)(18)(19)(20)(21) Besides, Co-based oxides are excellent electrocatalysts for OER, (22)(23)(24)(25) However, the multiple valence and related structural variability of transition metal oxides, which is at the origin of their exceptional electrocatalytic performance, is also behind the difficulty to produce these compounds in a reproducible and controlled manner.…”

Nanoscale Electrocatalysis of Hydrazine Electro-Oxidation at Blistered Graphite Electrodes

“…platinum and ruthenium) for a wide range of applications. [1][2][3][4] Great efforts have been made in developing non-noble metals catalysts through means of surface modification, doping, and alloying, 5,6 with varying degrees of success. 7 Beyond metals, carbon-based materials, which have mainly been used as supports for electrocatalysts, 8,9 are receiving increasing attention as electrocatalysts in their own right.…”