Shape-controlled synthesis of one-dimensional α-MnO2 nanocrystals for organic detection and pollutant degradation

• One-dimensional α-MnO2 nanocrystals with different shapes were synthesized.
• α-MnO2 shows shape related activities for detection of H2O2 and l-ascorbic acid.
• α-MnO2 shows shape related activities in activation of peroxymonosulfate.
• Different activities are due to different surface areas and surface charge densities.

Shape control is an important technique for improving the quality and activity of nanomaterials. Two types of one-dimensional manganese dioxide (MnO2) nanocrystals with different shapes were synthesized by facile hydrothermal methods as the catalyst materials for both sensor fabrication and heterogeneous catalytic reactions. The nanomaterials present an α-crystalline phase (α-MnO2) in either nanotube or nanowire shapes. The α-MnO2 nanocrystals were found to have a favorable electrochemical property that can be used to fabricate sensors for rapid detection of hydrogen peroxide and l-ascorbic acid. The α-MnO2 also functioned well as a catalyst for the oxidation of phenol and chlorophenol by peroxymonosulfate and hydrogen peroxide in an aqueous solution at room temperature. Comparison between the two differently shaped α-MnO2 catalysts indicated that nanowires performed better than nanotubes in both electrocatalytic detection and catalytic phenol degradation. Compared to α-MnO2 nanotubes, nanowires have a much greater surface area and lower negative surface charge density, which are probably the main reasons for their higher catalytic activities.

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