Structural and Morphological Properties of Nanoporous Carbon Materials Obtained from Biomass

The present work investigated the structural and morphological properties of nanoporous carbon materials obtained from biomass, specifically waste coffee grounds, through thermochemical alkaline activation at various temperatures (400-900 °C). The influence of the temperature of chemical activation of plant raw materials on the porosity and structure of the obtained carbon materials was investigated. It is shown that the obtained carbon materials have a specific surface area of 400-1050 m2/g and a pore volume of 0.23-0.51 cm3/g, depending on the activation temperature. The study revealed that micropores with sizes ranging from 0.65 to 1.25 nm dominated the porous structure, particularly at higher activation temperatures.It was established that an increase in the obtaining temperature to 600 ºC leads to a decrease in the size of carbon particles, which was attributed to the partial combustion of smaller fragments. In contrast, at temperatures between 700-900 °C, the size of carbon fragments increased from 6.5 nm to 8.5 nm, likely due to the thermal decomposition of lignin and hemicellulose components in the biomass. Furthermore, at temperatures above 800 °C, an increase in the content of sp3 carbon was noted, indicating the transformation of the carbon structure. The results demonstrated that the optimal activation temperature range for obtaining highly porous carbon materials with well-developed surface areas was 800-900 °C. This temperature range facilitated the formation of a microporous structure with a significant fraction of pores below 1.25 nm in diameter. By adjusting the activation temperature, it is possible to obtain carbon materials with controlled morphology and optimized porosity, making them suitable for energy storage applications.