High performance carbonized bamboo fibers were synthesized for a wide range of temperature dependent energy storage applications. The structural and electrochemical properties of the carbonized bamboo fibers were studied for flexible supercapacitor applications. The galvanostatic charge-discharge studies on carbonized fibers exhibited specific capacity of ~510F/g at 0.4 A/g with energy density of 54 Wh/kg. Interestingly, the carbonized bamboo fibers displayed excellent charge storage stability without any appreciable degradation in charge storage capacity over 5,000 charge-discharge cycles. The symmetrical supercapacitor device fabricated using these carbonized bamboo fibers exhibited an areal capacitance of ~1.55 F/cm2 at room temperature. In addition to high charge storage capacity and cyclic stability, the device showed excellent flexibility without any degradation to charge storage capacity on bending the electrode. The performance of the supercapacitor device exhibited ~65% improvement at 70 °C compare to that at 10 °C. Our studies suggest that carbonized bamboo fibers are promising candidates for stable, high performance and flexible supercapacitor devices.

In search of affordable, flexible, lightweight, efficient and stable supercapacitors, metal oxides have been shown to provide high charge storage capacity but with poor cyclic stability due to structural damage occurring during the redox process. Here, we develop an efficient flexible supercapacitor obtained by carbonizing abundantly available and recyclable jute. The active material was synthesized from jute by a facile hydrothermal method and its electrochemical performance was further enhanced by chemical activation. Specific capacitance of 408 F/g at 1 mV/s using CV and 185 F/g at 500 mA/g using charge-discharge measurements with excellent flexibility (~100% retention in charge storage capacity on bending) were observed. The cyclic stability test confirmed no loss in the charge storage capacity of the electrode even after 5,000 charge-discharge measurements. In addition, a supercapacitor device fabricated using this carbonized jute showed promising specific capacitance of about 51 F/g, and improvement of over 60% in the charge storage capacity on increasing temperature from 5 to 75 °C. Based on these results, we propose that recycled jute should be considered for fabrication of high-performance flexible energy storage devices at extremely low cost.

This paper reports the yields and product composition obtained from the stepwise pyrolysis of pine wood in a fluidized bed reactor. The first step temperature was varied between 260 °C and 360 °C. After the first step, the solid residue was cooled to ambient temperature and pyrolyzed again at 530 °C. If the first step temperature was below 290 °C, the cumulated yields (the sum of steps 1 and 2) were identical to yields of the single-step experiment at 530 °C. This indicates that the chemical and transfer processes taking place below 290 °C do not lead to chemical and structural changes that affect the outcome of the processes occurring in the temperature range from 290 °C to 530 °C. When the first step temperature was higher than 310 °C the cumulated yields of char, water, light organic compounds, and furans were higher, whereas the cumulated yields of volatiles (gases plus organic liquids) were lower than those obtained if the pyrolysis was conducted in a single step at 530 °C. To explain these observations, a mechanism is proposed in which the main emphasis lies on the competition between routes that lead to char formation and routes that release compounds from the biomass particle. Single compounds and lumped groups could not be concentrated with the stepwise approach. A separation into lighter and heavier oils turned out to be possible.

The interplay of chemistry, heat and mass transfer at particle and reactor levels was studied for the fast pyrolysis of cellulose.