Juglans Sporopollenin for High-Performance\nSupercapacitor Electrode Design

Abstract

Recently, plant pollen\nhas been used\nas a source of activated carbon to produce carbon-containing supercapacitor\nelectrodes. However, in this study, pollen was used as a biotemplate\nwith a completely different approach. As a biotemplate, pollen offers\na wide range of varieties in terms of exterior, porosity, shape, and\nsize. An electrode formed by the use of metal oxide grown on the pollen\nexine layer (sporopollenin microcapsules) as the active substance\nwill inevitably exhibit good electrochemical capacitive properties. Juglans male flowers have been distinguished by dissection\nfrom anthers. Isolation of pollen grains from anthers was carried\nout using sieving from suitable sieves (45–200 μm). Juglans sporopollenin exine microcapsules (SECs)\nwere separated from the intine and protoplasm by acetolysis in combination\nwith reflux. The solution containing SECs, metal ions, and Ni foam\nwas put into a Teflon-lined hydrothermal container, and then, it was\nreacted at 120 °C for 15 h. The resulting precipitate, as well\nas the Ni foam, was heat-treated at 300 and 360 °C for 3 h in\nair. The raw pollen, chemically treated pollen, and cobalt-coated\nSEC (CoSEC) and CoSEC/Ni foam were characterized using scanning electron\nmicroscopy, Brunauer–Emmett–Teller surface area analysis,\nthermogravimetric analysis, and X-ray diffraction techniques. Two\ndifferent types of supercapacitor electrode designs, with the use\nof exine microcapsules of Juglans sporopollenin,\nwere performed for the first time. The maximum specific capacitance\nwas up to 1691 F g^–1 at 5 A g^–1.