Preparation of High-Performance Porous Carbon Materials by Citric Acid-Assisted Hydrothermal Carbonization of Bamboo and Their Application in Electrode Materials

Abstract

Renewable energy needs an environmentally friendly and efficient energy storage device. In this work, porous carbon materials with different properties are prepared by citric acid (CA)-assisted hydrothermal carbonization of bamboo and KOH activation. The effects of the ratio of the added CA on the structure of hydrochar and the porous carbon product are studied systematically. It is found that the added CA can improve the carbonization degree of the hydrochar, content of oxygencontaining functional groups, and specific surface area of the final product. The highest specific surface area (3132 m 2 g −1 ) is achieved when 4 g of CA is added (C-HBC-4), which is significantly improved compared to the conventional hydrothermal process. In a three-electrode system, the specific capacitance of C-HBC-4 can reach 435.5 F g −1 at 0.5 A g −1 , which is higher than most other bamboo-derived porous carbon materials previously reported. After 30,000 charge and discharge cycles under a current density of 10 A g −1 , a retention rate of 97% is achieved. The results in this work show a green and viable path for the preparation of high-performance electrode materials for supercapacitors from biomass.

Hydrothermal Carbonization of Waste Biomass: A Review of Hydrochar Preparation and Environmental Application

“…These acids interact with mineral compounds, impacting hydrolysis, dehydration, condensation, and polymerization processes, making the process autocatalytic [49]. Further, citric acid may introduce more functional groups into the carbon skeleton and remove some minerals and organic groups in the biomass feedstock, leading to more rough and porous structures [50,51]. Faradilla et al [52] showed that the addition of citric acid during the HTC treatment of cellulose nanofiber and softwood pulp increased the diameter of formed carbon spheres.…”

Hydrothermal Carbonization Technology for Wastewater Treatment under the “Dual Carbon” Goals: Current Status, Trends, and Challenges

“…The resultant hydrochar had a higher calorific value and energy density, making it suitable for biofuel applications. Chen et al [54] used bamboo powder as raw material and activated the product in citric acid solution under hydrothermal conditions at 180 • C for 6 h. Citric acid is an efficient HTC additive to improve the carbonization degree, to optimize the pore structure distribution, and to introduce more oxygen-containing functional groups (OFGs) to hydrochar, which offer an appropriate precursor to be activated by KOH to improve the specific surface area (SSA) level and electrochemical performance of the activated porous carbon.…”

Advances in biomass-derived carbon composites as electrode materials for supercapacitors

“…A possible solution is adding additives to the HTC process which can greatly enhance their electrochemical characteristics and offer a solid choice for creating superior SCs. To put it in practical terms, Chen et al [28] described the fabrication of porous carbon materials by adding citric acid (CA) to help the HTC of bamboo, which considerably boosted the SSA (3132 m 2 g -1 ) and the specific capacitance (435.5 F g -1 at the current density of 0.5 A g -1 ) of EMs. A similar method was utilized by Susanti et al [29] to synthesis porous carbon materials.…”