Harvesting Capacitive Carbon by Carbonization of Waste Biomass in Molten Salts

Abstract

Conversion of waste biomass to value-added carbon is an environmentally benign utilization of waste biomass to reduce greenhouse gas emissions and air pollution caused by open burning. In this study, various waste biomasses are converted to capacitive carbon by a single-step molten salt carbonization (MSC) process. The as-prepared carbon materials are amorphous with oxygen-containing functional groups on the surface. For the same type of waste biomass, the carbon materials obtained in Na2CO3-K2CO3 melt have the highest Brunauer-Emmett-Teller (BET) surface area and specific capacitance. The carbon yield decreases with increasing reaction temperature, while the surface area increases with increasing carbonization temperature. A working temperature above 700 °C is required for producing capacitive carbon. The good dissolving ability of alkaline carbonate molten decreases the yield of carbon from waste biomasses, but helps to produce high surface area carbon. The specific capacitance data confirm that Na2CO3-K2CO3 melt is the best for producing capacitive carbon. The specific capacitance of carbon derived from peanut shell is as high as 160 F g(-1) and 40 μF cm(-2), and retains 95% after 10,000 cycles at a rate of 1 A g(-1). MSC offers a simple and environmentally sound way for transforming waste biomass to highly capacitive carbon as well as an effective carbon sequestration method.

Synthesis Strategies of Porous Carbon for Supercapacitor Applications

“…Besides, researchers could exert the unique chemical or structural characteristics of carbon sources to synthesize various porous carbons with different pore structures 43–45. Traditionally, potassium hydroxide (KOH),51,52 sodium hydroxide (NaOH),53,54 zinc chloride (ZnCl 2 ),55 phosphoric acid (H 3 PO 4 ),49,56 sodium carbonate (Na 2 CO 3 ),57 and potassium carbonate (K 2 CO 3 )57,58 have been used as activation agents. For a high‐level summary of the effect of traditional chemical activation agents on porous carbon, the relationships between the SSA and activation temperature of the activated carbon are shown in Figure 3b for a few chemical activation agents 59.…”

Enhanced capacitive properties of commercial activated carbon by re-activation in molten carbonates

“…The preparation of carbon-based materials by molten carbonates treatment of waste biomass was previously reported by our group [20]. In that paper, the detailed investigation on the effect of the temperature, salts and duration was compared and rationalized, suggesting that the optimal conditions for the capacitive of the prepared carbon was 850 C, K 2 CO 3 eNa 2 CO 3 , and 1 h. Therefore, we employed such an "optimal" condition to reactivate the commercial ACs.…”

“…The employed biocompatible molten carbonates are of high heat capacities and good thermal stability, capable of dissolving inert components and increasing porosity of ACs [20].…”

Using Peanut Shells to Construct a Porous MnO/C Composite Material with Highly Improved Lithium Storage Performance

“…prepared a capacitive carbon derived from peanut shell by a simple molten salt pyrolysis route and investigated the electrochemical property for supercapacitors. The as‐obtained carbon showed the specific capacity of 160 F g −1 and retained 95 % after 10000 cycles at 1 A g −1 . For all we know, there are few reports about MnO/C composite material using peanut shell as carbon source.…”