Alkali Metal-Modified P2 NaxMnO2: Crystal Structure and Application in Sodium-Ion Batteries

Novel application of sodium manganese oxide in removing acidic gases in ambient conditions

In this study, we have demonstrated the application of sodium manganese oxide for the chemisorption of toxic acidic gases at room temperature. The fabricated alkali ceramic has Na_0.4MnO₂, Na₂Mn₃O₇, and Na_xMnO₂ phases with a surface area of 2.6 m² g^-1. Na-Mn oxide was studied for oxidation of H₂S, SO₂, and NO₂ gases in the concentration range of 100-500 ppm. The material exhibited a high uptake capacity of 7.13, 0.75, and 0.53 mmol g^-1 for H₂S, SO₂, and NO₂ in wet conditions, respectively. The material was reusable when regenerated simply by soaking the spent oxide in a NaOH-H₂O₂ solution. While the H₂S chemisorption process was accompanied by sulfide, sulfur, and sulfate formation, the SO₂ chemisorption process yielded only sulfate ions. The NO₂ chemisorption process was accomplished by its conversion to nitrite and nitrate ions. Thus, the present work is one of the first reports on alkali ceramic utilization for room-temperature mineralization of acidic gases.

Fabrication of Na0.4MnO2 Microrods for Room-Temperature Oxidation of Sulfurous Gases

Phase pure Na_0.4MnO₂ microrods crystallized in the orthorhombic symmetry were fabricated for the wet oxidation of H₂S and SO₂ gases at room temperature. The material was found highly effective for the mineralization of low concentrations of acidic gases. The material was fully regenerable after soaking in a basic H₂O₂ solution.

Sodium Pre-Intercalation-Based Na3-δ-MnO2@CC for High-Performance Aqueous Asymmetric Supercapacitor: Joint Experimental and DFT Study

Electrochemical energy storage devices are ubiquitous for personal electronics, electric vehicles, smart grids, and future clean energy demand. SCs are EES devices with excellent power density and superior cycling ability. Herein, we focused on the fabrication and DFT calculations of Na₃-δ-MnO₂ nanocomposite, which has layered MnO₂ redox-active sites, supported on carbon cloth. MnO₂ has two-dimensional diffusion channels and is not labile to structural changes during intercalation; therefore, it is considered the best substrate for intercalation. Cation pre-intercalation has proven to be an effective way of increasing inter-layered spacing, optimizing the crystal structure, and improving the relevant electrochemical behavior of asymmetric aqueous supercapacitors. We successfully established Na⁺ pre-intercalated δ-MnO₂ nanosheets on carbon cloth via one-pot hydrothermal synthesis. As a cathode, our prepared material exhibited an extended potential window of 0-1.4 V with a remarkable specific capacitance of 546 F g^-1(300 F g^-1 at 50 A g^-1). Moreover, when this cathode was accompanied by an N-AC anode in an asymmetric aqueous supercapacitor, it illustrated exceptional performance (64 Wh kg^-1 at a power density of 1225 W kg^-1) and incomparable potential window of 2.4 V and 83% capacitance retention over 10,000 cycles with a great Columbic efficiency.

Structural Degradation of O3-NaMnO2 Positive Electrodes in Sodium-Ion Batteries

In this manuscript, we report an extensive study of the physico-chemical properties of different samples of O3-NaMnO2, synthesized by sol–gel and solid state methods. In order to successfully synthesize the materials by sol–gel methods a rigorous control of the synthesis condition has been optimized. The electrochemical performances of the materials as positive electrodes in aprotic sodium-ion batteries have been demonstrated. The effects of different synthesis methods on both structural and electrochemical features of O3-NaMnO2 have been studied to shed light on the interplay between structure and performance. Noticeably, we obtained a material capable of attaining a reversible capacity exceeding 180 mAhg−1 at 10 mAg−1 with a capacity retention >70% after 20 cycles. The capacity fading mechanism and the structural evolution of O3-NaMnO2 upon cycling have been extensively studied by performing post-mortem analysis using XRD and Raman spectroscopy. Apparently, the loss of reversible capacity upon cycling originates from irreversible structural degradations.