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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