Fecha de publicación: -- Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE This study systematically tracks the structural evolution of polyacrylonitrile-based carbon fibers during carbonization from 300°C to 1300°C. Unactivated carbonized fiber powders are directly used as electrodes. Changes in functional groups, graphitization ordering, and pore structure at different carbonization temperatures are examined and correlated with specific capacitance and charge storage capacity.


ABSTRACT
The structural evolution of polyacrylonitrile (PAN) fibers at different carbonization temperatures was systematically studied, and its influence on the fundamental electrochemical performance was preliminarily explored. During low-temperature carbonization (300°C–500°C), unreacted cyano and conjugated carbonyl groups within thermal oxidation stabilization (TOS) fibers participated in cyclization and crosslinking. From 800°C, the conjugated carbonyl groups were eliminated through dehydration, accompanied by increased crystallite size and decreased d (002) and I
D/I
G ratio, indicating enhanced graphitization ordering. At higher temperatures, the I
D/I
G ratio stabilized, indicating a high degree of graphitization. The specific capacitance first decreased sharply and then increased with the rising carbonization temperature. The 300°C carbonized fibers exhibited the highest specific capacitance, attributed to abundant surface functional groups that dominate pseudocapacitive behavior. With increasing temperature, the decomposition of non-carbon elements reduces active sites, and the low graphitization degree led to poor electron transport, causing a decline in capacitance. At 1300°C, enhanced graphitization and conductivity restored the capacitance, yet it remained lower than at 300°C, indicating functional groups contribute more to specific capacitance than conductivity improvement alone. This work offers insights into the carbonization mechanism of PAN fibers and the design of carbon fiber electrodes for energy storage applications.