Preparation of High-Performance Hierarchical Porous Activated Carbon via a Multistep Physical Activation Method for Supercapacitors

Abstract

Biomass-derived activated carbons (ACs) are regarded as important electrode materials for supercapacitors (SCs) due to their abundance and large specific surface areas (SSAs). Here, we develop a multistep physical activation strategy by combining water vapor and CO2 activation to prepare apricot shell-derived activated carbons (ASACs). Compared to the traditional single physical activation method, such a multistep activation strategy is conducive to forming an excellent hierarchical porous structure. The as-obtained ACVC-4 displays a high SSA and pore volume, and its effective pore volume and the mesoporous volume fraction are 0.720 cm3 g–1 and 55.76%, respectively. Furthermore, the ACVC-4 has a superior specific capacitance of 39.17 F g–1 at 0.5 A g–1 as the electrode material in the 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte for SCs. When the current density increases from 0.5 to 10 A g–1, its capacitance retention rate reaches 87.77%, which is far higher than that of other ASACs and commercial YP-50F. We believe that the multistep activation strategy for preparing ACs could open a new way to obtain high-performance electrode materials for SCs.

CO2-Activation Nanofiber Carbon Paper as a High-Performance Interlayer for Trapping Polysulfides in Li–S Batteries

“…This reveals that CO 2 behaves as an oxidant and tends to react with the C atom that is adjacent to quaternary N or −C–O–C (Figure a,b). CO is then released, and the edges or defects appear in the graphitic lattice; thus, quaternary N is changed to pyrrolic or pyridinic N, and −C–O–C is changed to −CO or −COOH. − …”

Quasi-Solid, Bio-Renewable Supercapacitors Based on Cassava Peel and Cassava Starch and the Use of Carbon Dots as Performance Enhancers

“…As illustrated in Figure d, the Raman scattering spectra of CC and AC displayed two dominant peaks, including the D band at 1361 cm –1 and the G band at 1565 cm –1 , representing the disordered and graphitic carbon structures, respectively. The I D / I G intensity ratio of CC is 1.28 while that of AC increased to 1.32, which means that the highly defected carbon structure due to the disruption of the sp 2 bond of the carbon increased with respect to the ordered carbon structure after activation . Next, the nitrogen adsorption–desorption studies were carried out to measure the specific surface area, pore size, and pore volume (Table ).…”

“…The I D /I G intensity ratio of CC is 1.28 while that of AC increased to 1.32, which means that the highly defected carbon structure due to the disruption of the sp 2 bond of the carbon increased with respect to the ordered carbon structure after activation. 29 Next, the nitrogen adsorption−desorption studies were carried out to measure the specific surface area, pore size, and pore volume (Table 1). The comparison of nitrogen adsorption−desorption isotherms of AC and CC was shown in Figure 2e.…”

Advances in Micro-/Mesopore Regulation Methods for Plant-Derived Carbon Materials

“…Compared with multi-step activation, single-step activation has the advantages of low energy consumption and time saving [ 86 ]. The essence of this strategy is the redox reaction between the C element in the carbon material and the other elements in the oxidizing gases [ 87 ]. Table 2 shows the application of the physical activation method in plant-based carbon materials.…”

“…As shown in Figure 8 a, the specific surface area and microporosity were up to 1145 m 2 /g and 50.3%, respectively. Ding et al [ 87 ] investigated the effect of different preparation processes on the properties of the materials and found that the material subjected to multi-step activation displayed higher specific surface area (1690 m 2 /g) and pore volume (0.93 cm 3 /g), while one-step activation yielded a relatively high microporosity (72.0%), which is about 1700, 162, and 72 times larger than that of the unactivated materials, respectively. Phothong [ 89 ] and Khuong [ 90 ] investigated the effect of CO 2 activation temperature and activation time on the pore structure of bamboo-derived carbon materials, respectively.…”