Carbonization and H3PO4 activation of fern Dicranopteris linearis and electrochemical properties for electric double layer capacitor electrode

Today, the world's climate change is a growing problem, plant carbon sequestration is one of the effective ways to mitigate climate change by reducing greenhouse gases, mostly carbon gases. Dicranopteris linearis (D. linearis), a common fern species in the tropic or subtropic ecoregions, has been recently recognized as a potential feedstock to produce highly porous biochar. This study aims to enhance the specific surface area (SSA) and pore volumes of biochars derived from the D. linearis by H3PO4 activation and examine electrical properties of the activated biochars and their possible usage for the electric double-layer capacitor (EDLC) electrode. The treated raw fern was activated with H3PO4 85% by the three different mixing ratios 1:0, 1:1, and 1:3 (w/w) and then pyrolysis under N-2 flow maintained at 500 degrees C for 1 h. The performance as the electrode for an EDLC was evaluated in 1 mol L-1 H2SO4 solution for the H3PO4-activated samples. The SSA and pore volumes were drastically increased after activation. The maximum SSA and pore volume were 1212 m(2) g(-1) and 1.43 cm(3) g(-1), respectively for the biochar activated at 400 degrees C with a weight mixing ratio 1:3 (w/w) between the fern and H3PO4 acid while these values of the biochar at 400 degrees C were 12 m(2) g(-1) and 0.02 cm(3) g(-1), respectively. The biochar activated at 600 degrees C with the mixing ratio 1:1 (w/w) showed the maximum capacitance value, ca. 108 F g(-1) at 1 mV s(-1). The activation using H3PO4 showed a positive tendency to enhance electrochemical properties and it could be a premise toward a higher performance of EDLC from the D. linearis derived activated biochar.