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Manganese oxides have attracted great interest in electrochemical energy storage due to high theoretical specific capacitance and abundant valence states. The multiple valence states in the redox reactions are beneficial for enhancing the electrochemical properties. Herein, three manganese microspheres were prepared by a one‐pot hydrothermal method and subsequent calcination at different temperatures using carbon spheres as templates. The trivalent manganese of Mn2O3 exhibited multiple redox transitions of Mn3+/Mn2+ and Mn4+/Mn3+ during the intercalation/deintercalation of electrolyte ions. The possible redox reactions of Mn2O3 were proposed based on the cyclic voltammetry and differential pulse voltammogram results. Mn2O3 microsphere integrated the advantages of multiple redox couples and unique structure, demonstrating a high specific capacitance and long cycling stability. The symmetric Mn2O3//Mn2O3 device yielded a maximum energy density of 29.3 Wh kg−1 at 250 W kg−1. [ABSTRACT FROM AUTHOR]

The rational synthesis of hybrid catalysts with diverse electrocatalytically active components for robust oxygen reduction reaction (ORR) is highly desirable for the development of sustainable metal-air batteries. By using melamine as nitrogen and hydrogen precursors, herein, melamine pyrolysis-induced functionalized nitrogen doping was adopted for the construction of nitrogen doped manganese oxides (N-MnO x Rs), which consists of manganese oxyhydroxide (MnOOH) rooted in manganese sesquioxide (Mn 2 O 3) rod, as a robust ORR electrocatalyst. Systematic studies have found that a suitable mass ratio of melamine to β-MnO 2 rods is necessary for the formation of electrocatalytically MnOOH and Mn 2 O 3. The representative N-MnO x Rs exhibits the nano structure consisting of interconnected nonorods, nanowires, and nanoparticles, which not only increases the exposure of more active sites but also enhances microstructure stability. Moreover, the nitrogen doping creates high content of oxygen vacancies, which accelerates electron transmission/transfer of N-MnO x Rs. As a result, the optimal N-MnO x Rs exhibits impressive ORR catalytic performance in a homemade ZAB. The N-MnO x Rs driven ZAB (176.6 mW cm-2; 811 mAh g-1) delivers a high peak power density and large discharging capacitance comparable to Pt/C driven one (178.1 mW cm-2; 800 mAh g-1), displaying a promising application potential. This work provides a functionalized nitrogen doping strategy for rational construction of robust hybrid electrocatalysts for energy conversion. • Functional nitrogen doping strategy was adopted for construction of MnOOH rooted in Mn 2 O 3 rod hierarchical electrocatalyst. • The nano hierarchical feature not only increases exposure of active sites but also enhances microstructure stability. • The representative N-MnO x Rs exhibits robust ORR catalytic performance comparable to Pt/C catalyst in a homemade ZAB. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn 2 O 3 integrated catalytic ceramic membrane is fabricated by solid state sintering. • Catalytic ceramic membranes degrade multiple EOCs via peroxymonosulfate activation. • Singlet oxygen (1O 2) is the primary reactive species for the degradation. • Excellent catalytic stability and negilible leaching of Mn ions are found. • Hydroxylation and C-N bond cleavage are main degradation pathways of acetaminophen. In this study the performance of catalytic ceramic membranes in activating peroxymonosulfate (PMS) for the degradation of emerging organic contaminants (EOCs) was investigated. The catalytic ceramic membrane (MnCM) integrated with Mn 2 O 3 nanoparticles was fabricated by a solid-state sintering method. Physical and chemical properties of MnCM were characterized by SEM/EDX, XRD, BET, AFM and XPS. The MnCM/PMS system has shown excellent decontamination efficiencies (81–97% removal) for different EOCs. Acetaminophen (APAP) has been efficiently degraded by MnCM/PMS in different real water matrices and harsh water conditions. Based on results of quenching experiments and electron paramagnetic resonance (EPR) analyses, non-radical pathway with singlet oxygen (1O 2) was the dominant ROS for the degradation of EOCs. The membrane pores in active layer acted as micro-reactors for the interaction among active sites, PMS, and EOCs. The MnCM/PMS system showed outstanding catalytic stability with high mineralization (TOC removal of ∼ 65%) and negligible leaching of the manganese (1.3–1.5 µg/L) in permeate. Hydroxylation and C-N bond cleavage were found to be the main degradation pathways of APAP by MnCM/PMS system. The MnCM prepared in this study with excellent performance could be a way forward for applications at large-scale or full-scale water systems suffering from heavy loads or trace amount of refractory organic compounds. [ABSTRACT FROM AUTHOR]

Abstract: Yttria-stabilized zirconia (YSZ)-based amperometric NO2 sensors comprised of an In2O3 sensing-electrode (SE), a Pt counter-electrode (CE) and a Mn2O3 reference-electrode (RE) in both tubular and rod geometries were fabricated and their sensing characteristics were examined. For comparative purposes, the performance of the In2O3-SE and Pt-CE were also examined against an internal Pt/air-RE. Experimental observations of tubular YSZ-based gas sensors revealed that a three-electrode system exhibited better electrical signal stability, when compared with a two-electrode system. Additionally, replacing the internal Pt/air-RE with an external Mn2O3-RE (exposed to the sample gas), was found to have a negligible effect on the gas sensing characteristics of the tubular sensor. This gas sensing equivalence indicates that Mn2O3-RE can successfully replace the Pt/air-RE in an amperometric gas sensor. Similarly, rod-type sensors utilizing an In2O3-SE and a Mn2O3-RE were observed to have almost identical NO2 sensing characteristics to that of the tubular sensor. Furthermore, both sensors (tubular or rod geometry) exhibited a linear response to increasing NO2 concentration in the range of 20–200ppm at 550°C. [Copyright &y& Elsevier]

MnO x-Y2O3 binary metal oxide catalysts are synthesized by a constant-pH co-precipitation method, their ability of NO x storage capacity and absorbing process were investigated. The pure MnO x and Y2O3 calcined at 500 °C for 4 h in static air are both of body-centre structure, while the binary metal oxides containing Mn and Y are mainly of amorphous phase. The adulteration of Y2O3 can remarkably improve the specific surface areas of the catalysts, which probably result of the enhancement on NO storage capacity and catalytic oxidation ability of NO at 100 °C. The XPS results indicate that both Mn and Y have 3+ chemical states in the binary oxides. FT-IR spectra could be beneficial to explain the NO storage process on the binary metal oxide: NO can be adsorbed on the MnO x and Y2O3 sites as nitrates and nitrites, respectively, and then the nitrites on Y2O3 site are shifted to Mn2O3 site and then is oxidized to nitrates. As a result, the NO storage capacity is enhanced due to the adulteration of Y2O3, finally the NO x are adsorbed on the Mn2O3 site as nitrate species. [ABSTRACT FROM AUTHOR]

Abstract: Self ordered arrays of titanium manganese mixed oxide nanotubes were prepared by anodization of Ti8Mn alloy (UNS R56080) under ultrasonication in diluted ethylene glycol containing fluoride. The dimensions of the nanotubes (diameter: 20–100nm and length: 0.5–2.0μm) could be tuned by changing the synthesis parameters. The as-anodized nanotubes showed a stoichiometry of (Ti,Mn)O2. Upon annealing at 500°C in oxygen atmosphere, the nanotubes contained a mixture of anatase+rutile phases of TiO2 and Mn2O3. The composition of the oxide nanotubes was influenced by the chemistry of the phases present in the alloy. More manganese content was observed in the oxide formed on the β-phase than in the oxide layer of α-phase. Anodization in the ultrasonic field increased the kinetics of nanotubular oxide formation and resulted in homogeneous ordering of the nanotubular arrays as compared to the anodization by conventional stirring in the fluoride containing ethylene glycol solution. Whereas, anodization in aqueous acidified fluoride solutions resulted in severe attack of the β-phase and did not show presence of nanotubular oxide structure. [Copyright &y& Elsevier]

The solid-solid interactions between manganese and magnesium oxides in absence and in presence of small amounts of Li2O have been investigated. The molar ratios between manganese and magnesiurn oxides in the form of Mn2O3MgO were varied between 0.05:1 to 0.5:1. The mixed solids were calcined in air at 400-1000°C. The techniques employed were DTA, XRD and H2O2 decomposition at 20-40°C. The results obtained revealed that solid-solid interactions took place between the reacting solids at 600-1000°C yielding magnesium manganates (Mg2MnO4, Mg6MnO8, MgMnO4 besides unreacted portions of MgO, Mn2O1 and Mn3O4). Li2O-doping (0.75-6 mol%) of the investigated system followed by calcination at 600 and 800°C decreased progressively the intensity of the diffraction lines of Mn2O3 (Bixbyite) with subsequent increase in the lattice parameter 'a' of MgO to an extent proportional to the amount of Li2O added. This finding might suggest that the doping process enhanced the dissolution of Mn2O3 in MgO forming solid solution. This treatment led also to the formation of Li2MnO3. Furthermore, the doping with 3 and 6 mol% Li2O conducted at 800°C resulted in the conversion of Mn2O3 into Mn3O4, a process that took place at 1000°C in absence of Li2O. The produced Li2MnO3 phase remained stable by heating at up to 1000°C. Furthermore, Li2O doping of the investigated system at 400-1000°C resulted in a progressive measurable increase in the particle size of MgO. The catalytic activity measurements showed that the increase in the molar ratio of Mn2O3 in the samples precalcined at 400-800°C was accompanied by a significant increase in the catalytic activity of the treated solids. The maximum increase in the catalytic activity expressed as reaction rate constant measured at 20°C (k20°C) attained 3.14, 2.67 and 3.25-fold for the solids precalcined at 400, 600 and 800°C, respectively. Li2O-doping of the samples having the formula 0.1 Mn2O3/MgO conducted at 400-600°C brought a progressive significant increase in its catalytic activity. The maximum increase in the value of k20°C due to Li2O attained 1.93 and 2.75-fold for the samples preheated at 400 and 600°C, respectively and opposite effect was found for the doped samples preheated at 800°C. [ABSTRACT FROM AUTHOR]