Facile Synthesis of Sustainable Biomass-Derived Porous Biochars as Promising Electrode Materials for High-Performance Supercapacitor Applications

Abstract

Preparing sustainable and highly efficient biochars as electrodes remains a challenge for building green energy storage devices. In this study, efficient carbon electrodes for supercapacitors were prepared via a facile and sustainable single-step pyrolysis method using spruce bark as a biomass precursor. Herein, biochars activated by KOH and ZnCl2 are explored as templates to be applied to prepare electrodes for supercapacitors. The physical and chemical properties of biochars for application as supercapacitors electrodes were strongly affected by factors such as the nature of the activators and the meso/microporosity, which is a critical condition that affects the internal resistance and diffusive conditions for the charge accumulation process in a real supercapacitor. Results confirmed a lower internal resistance and higher phase angle for devices prepared with ZnCl2 in association with a higher mesoporosity degree and distribution of Zn residues into the matrix. The ZnCl2-activated biochar electrodes’ areal capacitance reached values of 342 mF cm−2 due to the interaction of electrical double-layer capacitance/pseudocapacitance mechanisms in a matrix that favors hydrophilic interactions and the permeation of electrolytes into the pores. The results obtained in this work strongly suggest that the spruce bark can be considered a high-efficiency precursor for biobased electrode preparation to be employed in SCs.

Preparation and Characterization of Pulp and Paper Mill Sludge-Activated Biochars Using Alkaline Activation: A Box–Behnken Design Approach

“…The other samples have broken structures with high roughness, but no holes are observed on their surfacesas a consequence, they presented lower SSA than SB10 and SB13. The holes in SB10 and SB13 are macropores with considerable importance for the solid–liquid contact, allowing passage for pollutants or electrolytes to the smaller pores in the inner structure of the biochars, thereby maximizing the accumulation of pollutants (if used as adsorbent) or charge storage (if used as electrodes) into the cavities. , …”

“…The holes in SB10 and SB13 are macropores with considerable importance for the solid−liquid contact, allowing passage for pollutants or electrolytes to the smaller pores in the inner structure of the biochars, thereby maximizing the accumulation of pollutants (if used as adsorbent) or charge storage (if used as electrodes) into the cavities. 34,35 3.4.2. Raman Analysis.…”

Organic Crosslinked Polymer-Derived N/O-Doped Porous Carbons for High-Performance Supercapacitor

“…Nitrogen doping has been demonstrated to be an effective way to improve the wettability and conductivity of carbon materials and can also provide additional pseudocapacitance for supercapacitors. Generally, nitrogen-doped carbon materials can be prepared using two synthetic strategies, namely by the pyrolysis of nitrogen-containing precursors, such as biomass [18], synthetic polymers [19], small molecules [20], and ionic liquids [21], or by the chemical or thermal modification of premade carbon materials with reagents/gases containing nitrogen atoms [22]. Zhang et al [23] used urea as a nitrogen-containing precursor and KOH as the activator to prepare a carbon material with an appropriate amount of N doping, which yielded a nitrogen-doped carbon material with a porous structure and large specific surface area.…”

Heteroatom-Doped Hierarchically Porous Biochar for Supercapacitor Application and Phenol Pollutant Remediation

“…Moreover, biochars are widely studied as electrode materials or catalysts because of their high specific surface area (SSA), adjustable pore structure, abundant surface heteroatom dopants, and good electrical conductivity [ 3 , 4 ]. A variety of biomasses have been converted into biochar materials for applications including electrochemical supercapacitors [ 5 , 6 , 7 , 8 ], electrosynthesis [ 9 , 10 ], and environmental remediation [ 11 , 12 , 13 ].…”