Design and Synthesis of Highly Porous Activated Carbons from Sargassum as Advanced Electrode Materials for Supercapacitors

Abstract

The synthesis of three-dimensional porous biomass carbon was investigated using sargassum as precursor employing KOH, ZnCl 2 and H 3 PO 4 as the activators for the application as electrode materials for supercapacitors. H 3 PO 4 activation resulted in the plugging of pore structure due to the formation of crystallized phosphorus, while three-dimensional framework of porous carbons were synthesized applying ZnCl 2 and KOH. Compared with ZnCl 2 (441.14 m 2 g −1 ), larger surface area was achieved by KOH activation (2486.18 m 2 g −1 ) at 700°C, leading to the significantly better electrochemical performance. The porosity of KOH activated carbon was further improved by adjusting the activation temperature, and a high surface area of 3170.02 m 2 g −1 was obtained by two-step activation of firstly 400°C activation for 45 min and then 800°C for 2 h (KOH-400-800). KOH-400-800 electrode exhibited a high capacitance of 316 F g −1 at 1 A g −1 with good rate capacity (84% retention at 10 A g −1 ) and excellent cycling stability of 99.4% capacitance retention after 5000 cycles. The KOH-400-800 sample also showed a high energy density of 41.67 W h kg −1 and a power density of 320.51 W kg −1 at a current density of 1 A g −1 in the voltage range of 0-1 V.

Sargassum in Mexico: from environmental problem to valuable resource

“…Activated carbons from sargassum in supercapacitors also presented high specific gravimetric capacitance, good rate capacity, and excellent cycling stability near 95% [149]. Hence, nanocarbons from pelagic Sargassum can be considered a good material for electrodes in electrochemical systems.…”

“…Pelagic Sargassum chemical composition opens the opportunity to develop new nanostructured tailored materials for multiple applications, such as energy generation [142,143], medicine [144], antibacterial agents [145,146], and environmental remediation tools [147,148]. Recently, nanocarbons materials have been produced from brown sargassum for their use in electrochemical systems such fuel cells as [142] and supercapacitors [149], where the algae was activated at different temperatures presenting high specific surface areas <2500 m 2 /g. In the case of the alkaline fuel cell, the oxygen reduction reaction parameters of the nitrogen-doped carbon show comparable results with the traditional Pt electrocatalyst material [142].…”

Using Biochar and Coal as the Electrode Material for Supercapacitor Applications

“…Four key temperature points during KOH activation were put forward in the reference (Wang and Kaskel, 2012) which indicate that the important product of K 2 CO 3 forms in reaction at about 400 • C as shown in Equation (2), KOH completely reacts at about 600 • C, K 2 CO 3 decomposes into CO 2 and K 2 O and metallic K forms at 700 • C in Equation 4and 5, and pyrolysis of K 2 CO 3 is finished at ∼800 • C. At higher temperature, C could reacts with CO 2 in Equation (6). Based on the conclusions of Equation (2-6), and the activated carbon has a better supercapacitor performance at 800 • C in the reference (Guo et al, 2019), so the temperature of KOH activation in this experiment was set at 800…”

Geometrical effects on ionic diffusion in carbon‐carbon symmetric supercapacitors

“…35 N 2 adsorptiondesorption isotherm provides good accuracy for the surface characteristics of porous materials with pore sizes in both micro-and meso-ranges 35 and is widely used for ACs. [36][37][38] The N 2 adsorption-desorption isotherm is more suitable to the analysis of porous materials with pore widths larger than 1 or 1.5 nm, through which relatively large electrolyte ions, such as BF 4 − ; (0.98 nm) and Et 4 N + (1.48 nm), 39 migrate. It is known that the size and porous structure of ACSs play important roles in energy storage.…”

“…H 2 is a good candidate for the characterization of the carbonaceous materials prepared for the applications for H 2 adsorption and separation 35 . N 2 adsorption‐desorption isotherm provides good accuracy for the surface characteristics of porous materials with pore sizes in both micro‐ and meso‐ranges 35 and is widely used for ACs 36‐38 . The N 2 adsorption‐desorption isotherm is more suitable to the analysis of porous materials with pore widths larger than 1 or 1.5 nm, through which relatively large electrolyte ions, such as BF 4 − ; (0.98 nm) and Et 4 N + (1.48 nm), 39 migrate.…”