Venice's macroalgae-derived active material for aqueous, organic, and
solid-state supercapacitors
Abstract
In this study, self-doped porous activated biochar derived from Venice
lagoon’s Sargassum brown macroalgae (ABS) has been successfully prepared
through thermochemical carbonization (pyrolysis) followed by CO2
physical activation and used as electrodes for supercapacitor (SC)
applications. The ABS exhibits a remarkable specific surface area of 821
m2 g-1 and heteroatoms (N, O, and S) doping, both key features to attain
high-performance carbon-based SC electrodes. The electrochemical
performances of ABS-based SCs were assessed in three different
electrolytes. Two are aqueous (i.e., 1 M H2SO4 and 8 M NaNO3), while the
third one is the prototypical organic, namely 1 M TEABF4 in
acetonitrile. In these three electrolytes, the ABS-based electrodes
exhibited specific capacitance values (Cg) of 109.5, 79.0, and 64.3 F
g-1, respectively, at a current density of 0.1 A g-1. The capacitive
performance resulted in SC energy densities of 3.45 Whkg-1 at 22.5
Wkg-1, 6.35 Whkg-1 at 36.1Wkg-1, and 12.4 Whkg-1 at 57.4 Wkg-1 and
maximum power densities of 147, 222, and 378 kWkg-1 in the acidic,
quasi-neutral aqueous electrolyte and organic electrolyte, respectively.
The ABS electrodes were used to realize a flexible solid-state SC based
on the sulfonated polyether ether ketone (SPEEK):functionalized niobium
disulfide flakes (f-NbS2) composite membrane. The flexible solid-state
SC displayed a remarkable 97% Cg retention even under various
mechanical stresses, including bending up to 1000 times and folding
angles up to 180º, while keeping a Coulombic efficiency above 98%. This
study reveals algae-derived ABS as a promising sustainable source of
active materials for