A precursor route to synthesize mesoporous γ-MnO2 microcrystals and their applications in lithium battery and water treatment

Highlights: → Manganese carbonates with different morphologies such as microplates and microspheres were selectively synthesized just by changing the surfactants. → Mesoporous γ-MnO2 structures were fabricated from themolysis of MnCO3 precursors under inert gas. → The porous structures exhibited good performances in lithium storage. → The porous structures were also used as adsorbents in water treatment. - Abstract: MnCO3 microstructures, including 2.3 μm microplates with the thickness of 200 nm and 3.1 μm microspheres stacked with 50 nm-thick sheets, were hydrothermally prepared in the assistance of sodium dodecyl benzene sulphonate (SDBS) and dodecyl sulfonic acid sodium (SDS), respectively. With the as-synthesized MnCO3 as precursors followed by annealing at 400 deg. C for 4 h, mesoporous γ-MnO2 microplates and microspheres with the pore size of 4-50 nm, which basically preserved the initial shapes, were obtained. The Brunauer-Emmett-Teller surface areas of the as-prepared γ-MnO2 microplates and microspheres were 52.1 m2 g-1 and 50.2 m2 g-1, respectively. The electrochemical property tests over Li+ batteries showed that the initial discharge capacity of γ-MnO2 microplates and microspheres were 1997 mAh g-1 and 1533 mAh g-1. Noticeably, even after 100 cycles, the discharge capacity of γ-MnO2 microplates was still as high as 626 mAh g-1, indicating the decent cycle behavior. In addition, mesoporous γ-MnO2 was also applied as adsorbents in water treatment, and γ-MnO2 microplates and microspheres could remove about 55% and 80% of Congo red.