Aqueous zinc-ion batteries (AZIBs) can benefit from a deep understanding of the electrochemical reaction mechanism of cathode materials, which can assist in resolving issues such as cathode dissolution and electrostatic interactions. We reported a straightforward two-step synthesis of polydopamine coated MnO 2 (MnO 2 @PDA) and revealed the energy storage mechanisms in AZIBs. The layered structure of MnO 2 creates a generous passage for the insertion of H + /Zn 2+ ions. Simultaneously, the plethora of functional groups within PDA exerts a robust desolvation effect, bolstering the transfer rate of H + /Zn 2+ . This effect significantly enhances the overall efficiency and performance of cathode. The AZIBs, incorporating MnO 2 @PDA cathode material, consequently exhibit a satisfactory cycling capacity (412 mAh g −1 at 0.1 A g −1 ) and a superb specific energy (561.6 Wh kg −1 at 136.34 W kg −1 ). This work provides a new path for design strategies and catalytic mechanisms of MnO 2 @PDA cathode.
The functionalized MnO 2 /PDA/Fe 3 O 4 fibers were synthesized to removal Pb(II) from wastewater. MnO 2 nanosheets were in-situ loaded on the high saturation magnetization Fe 3 O 4 fibers matrix through a polydopamine (PDA) intermediate platform. The high Fe 3 O 4 content enabled the composite fibers to achieve rapid magnetic separation. The perpendicularly orientated MnO 2 nanosheets coated on the fibers could avoid agglomeration and give full play to their outstanding adsorption performance. The maximum Pb(II) adsorption capacity at 300 K, 308 K and 318 K calculated by Langmuir model could reach 196.67, 200.45 and 205.07 mg/g, respectively; all of which were higher than those of most reported MnO 2 based adsorbents. Thermodynamics showed that the fibers had spontaneously physicochemical adsorption of Pb(II). The composite fibers adsorbents had excellent Pb(II) selective adsorption and reusability. In addition, under the laboratory simulation test conditions, the fibers exhibited an excellent Pb(II) treated capacity of ~2500 and 6500 kg wastewater per kg adsorbents. This could dramatically purify wastewater from 10 mg/L to below 0.01 mg/L and 0.1 mg/L. The prepared MnO 2 /PDA/Fe 3 O 4 fibers had excellent adsorption capacity and actual treated capability for Pb(II), which could bring about rapid magnetic separation and offer great application potential in Pb(II) adsorption removal.
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