Catalytic characteristics of MnO₂nanostructures for the O₂reduction process

Abstract

Nanorods with an α type MnO(2) structure and a diameter ranging from 25 to 40 nm, along with tipped needles with a β MnO(2) structure and a diameter of 100 nm were obtained. The 25 nm diameter α MnO(2) nanorods showed the best catalytic activity for dissociation of HO(2)(-) formed during oxygen reduction in a KOH solution. The MnO(2) nanostructures preferably followed a two-electron oxygen reduction mechanism in a LiOH solution. The size of the catalyst also affected the specific capacities of the non-aqueous Li/O(2) batteries fabricated using the MnO(2) based air electrode. The highest specific capacity of 1917 mA h g(-1) was obtained for an α MnO(2) nanorod catalyst having a diameter of 25 nm. The cation present in the MnO(2) nanostructures appears to determine the catalytic activity of MnO(2).

Rutile (β-)MnO2 Surfaces and Vacancy Formation for High Electrochemical and Catalytic Performance

“…The shape may be described as being like a short pencil that has been sharpened at both ends. The tendency toward an elongated rod-like structure may be important to the nanorod and nanotube-type 75−78 morphologies of rutile MnO 2 that have shown promising electrochemical performance as battery cathodes, oxygen reduction catalysts, 79,80 and supercapacitors. 81 By considering higher Miller indexes than treated in previous computational studies, we bring to light the importance of new surfaces of importance to the properties of this system.…”

RuO 2 nanoparticles decorated MnOOH/C as effective bifunctional electrocatalysts for lithium-air battery cathodes with long-cycling stability

“…MnOOH is known to be produced by reaction between aqueous solution of KMnO 4 and MnSO 4 at elevated temperature [24]. Since MnO 2 is the most thermodynamically stable manganese species in aqueous solution, MnO 4 À ions from KMnO 4 oxidize water and liberate oxygen (Equation (1)), which reacts with Mn 2þ of MnSO 4 (Equation (2)), resulting in the precipitation of MnO 2 as follows [25,26]:…”

Synthesis of Ag/NiO composite nanosheets and empty microspheres and their highly effective electrocatalytic properties

“…6H 2 O = 6HCHO ? 4NH 3 ) [37], and nickel ions hydrolyzed to form Ni(OH) 2 . Additionally, the addition of PVP could prevent Ag nanoparticles from agglomerating, leading to the formation of Ag nanoparicles with a mean size of 10 nm or so.…”

“…The significant transition metal oxides with nanostructures generally possess numerously highlighted physicochemical properties and have been applied widely in catalysts [1][2][3][4], electrochemistry [5,6], gas sensors [7,8], biomedical materials [9,10] and other fields. Of the oxides, nickel oxide (NiO), an important p-typed semiconductor with stable band gap, has received much attention and been extensively studied and used frequently as electrode for lithium ion batteries and funnel cells [11,12], catalysts [13][14][15], electrochemical supercapacitors [16,17], dyesensitized photocathodes [18], magnetic materials [19,20], etc.…”