Manganese Oxide Nanoparticles: An Insight into Structure, Synthesis and Applications

Abstract

Manganese oxide nanoparticles with different crystal phases, morphologies, and structural diversity along with their exceptional properties like high specific surface area, a high fraction of surface atoms, non‐toxic nature, and excellent redox properties are drawing attention for various applications in storage science, especially in the batteries, super‐capacitors, energy conversion, and the environmental catalysis field. Precise control of particle size, morphology, surface area, Mnx+ oxidation state, etc. is the utmost important aspect to explore their application to the full potential. Here, the emphasis is on the recent trends in manganese oxide research – structure, synthesis, and applications. The structure of numerous crystalline phases of manganese oxide nanoparticles are summerized and several facile chemical synthesis processes to achieve the desired crystalline/amorphous structure are discoursed. Temperature and different synthesis conditions dependent phase transformations of β‐MnO2, α‐Mn2O3, and Mn3O4 from α‐MnO2 are discussed as well. The pragmatic approach directs that the application field is mostly controlled by the morphologies.

Understanding the role of manganese oxides in retaining harmful metals: Insights into oxidation and adsorption mechanisms at microstructure level

“…The size of the tunnels, defined by the number of chains, accommodates large cations (e.g., Mg 2+ , Ca 2+ , Ba 2+ , Na + , K + ) and water molecules [ [112] , [113] , [114] , [115] ]. Commonly found tunnel-structured Mn oxide minerals in nature include pyrolusite (1 × 1 configuration), Ramsdellite (1 × 2), nsutite (mixture of 1 × 1 and 1 × 2), cryptomelan (2 × 2), romanechite (2 × 3), and todorokite (3 × 3), with the rare occurrence of woodruffite (3 × 4) [ [116] , [117] , [118] , [119] , [120] , [121] , [122] ]. Under specific conditions in soil or sediments, layered Mn oxides can undergo a transformation into tunnel-structured Mn oxides [ 18 , 37 , 102 , 103 , 123 ].…”

“…The adsorption of metal ions onto Mn oxides is significantly influenced by the intrinsic properties of the Mn oxides, including their oxidation state, surface charge, crystallinity, and surface area, as well as the physical and chemical characteristics of the metal elements. Moreover, a range of environmental factors, such as reactant concentration, temperature, reaction time, pH value, and coexisting ions, also influence the adsorption behavior and capacity of Mn oxides for metal ions [ 8 , 116 , 222 ].…”

“…The performance of Mn oxides is significantly influenced by their phase, size, and morphology [ 223 ]. Layered Mn oxides are categorized into triclinic and hexagonal structures based on structural symmetry [ 129 , 224 ], while common tunneled Mn oxides possess n × m structures [ [116] , [117] , [118] , [119] , [120] , [121] , [122] ]. Hexagonal birnessites, consist of curled layers of edge-sharing [Mn(IV)O 6 ] and [Mn(III)O 6 ] octahedra with varying amounts of octahedral vacancies, possessing superior oxidation capacity compared to the triclinic birnessites [ 225 ].…”

Review on Medical Applications of Manganese Oxide (Mn2+, Mn3+, and Mn4+) Magnetic Nanoparticles

“…The Mn oxides are used in drug delivery in different forms like MnO 2 [167], MnO [168], Mn 2 O 3 [169], Mn 3 O 4 [34], and Mn-based composites [170,170]. Mn NP is used in different structures like rods [171], spheres [166], wires [172], sheets [173], platelets [174], mesoporous [166], hollow [175], etc. The redox ability of MnO 2 makes it more favorable for the triggered drug release by the reversible redox reaction [176].…”