Tunable high-performance microwave absorption for manganese dioxides by one-step Co doping modification

Enhanced catalytic activity of OMS-2 for carcinogenic benzene elimination by tuning Sr2+ contents in the tunnels

Cryptomelane-type manganese oxides (OMS-2) have been intensively investigated for application in the catalytic oxidation of carcinogenic benzene, and doping metal ions in the OMS-2 tunnels are widely used for modifying its catalytic activity. In this study, we reported a novel strategy of enhancing catalytic activity of OMS-2 for carcinogenic benzene elimination by tuning Sr²⁺ concentration in the tunnels. The catalytic activity result revealed that an obvious decrease (△T₅₀ = 27 °C and △T₉₀ = 37 °C) in T₅₀ and T₉₀ (corresponding to benzene conversions at 50 % and 90 %, respectively; initial benzene concentration was 2000 mg m^-3; contact time was 1.5 s) had been observed by increasing the Sr²⁺ concentration in the OMS-2 tunnels. The origin of Sr²⁺ doping effect on catalytic activity was theoretically and experimentally investigated by CO temperature-programmed reduction, ¹⁸O₂ isotope labeling, and density functional theory calculations. The result confirmed that increasing Sr²⁺ concentration in the tunnels not only promoted the lattice oxygen activity, but also facilitated the generation of more oxygen vacancy defects, thus considerably improving the catalytic activity of OMS-2.

Doping strategy to boost electromagnetic property and gigahertz tunable electromagnetic attenuation of hetero-structured manganese dioxide

A facile and simple chemical route has been used to synthesize novel three-dimensional (3D) architectures of nickel-doped ε-MnO₂ without the addition of any surfactant or organic template.

Carbon spheres@MnO2 core-shell nanocomposites with enhanced dielectric properties for electromagnetic shielding

Carbon spheres (CS)@MnO₂ core-shell nanocomposites, with MnO₂ nanoflakes uniformly coating at the surface of CS cores, were successfully synthesized by a facile water-bathing method. MnO₂ amounts is estimated to be 24.7 wt% in CS@MnO₂ nanocomposites. A high dielectric loss value and an electromagnetic shielding effectiveness of 16‒23 dB were observed for the CS@MnO₂ in the frequency range of 8‒18 GHz, which is mainly attributed to the enhanced absorption loss. The incorporation of the CS with MnO₂ improves the electrical conductivity. Meanwhile, the electromagnetic impendence matching has been significantly ameliorated. Moreover, the increasing interfaces between the CS and MnO₂ facilitate the microwave attenuation as well. Thus, the electromagnetic shielding performances were greatly enhanced. Our findings provide an effective methodology for the synthesis of the CS@MnO₂ core-shell nanocomposite for potential electromagnetic applications.

High temperature ferroelectric behaviour in α-MnO2 nanorods realised through enriched oxygen vacancy induced non-stoichiometry

Here, we observe high temperature ferroelectric behaviour in non-stoichiometric α-MnO₂ nanorods due to combined effects of charge and orbital ordering.