The effect of pH, coagulation bath, and reduction on characteristic properties of continuous graphene oxide fiber

This study focuses on the effect of different process parameters including pH of GO dispersion, hydrazine reduction, number of coagulation bath on the properties of graphene oxide (GO) fibers produced through wet spinning method. Produced GO fibers have been characterized by scanning electron microscopy, Raman, X-ray diffraction methods, and an electrical conductivity meter. Results show that pH3 hydrazine reduction causes an expansion of the fiber volume and formation of porous fiber structure with higher defects. The crystal structure of GO fibers was also observed to be affected by hydrazine reduction, leading to decreased interlayer spacing and increased crystalline size and number of layer as compared to the reference (unreduced) one. Single coagulation bath was found to result in crystal on the fiber surface because of the calcium chloride (CaCI₂) salt, which provides higher electrical conductivity than triple coagulation bath. The pH value of GO dispersion was found to influence the crystal structures of the GO fiber, resulting in lower interlayer spacing, lower crystallinity degree, and higher crystallite size in the pH5 sample as compared to that of pH3 for triple coagulation baths. The results obtained in this study are expected to contribute to and shed light for further studies on carbon-based fiber materials such as GO fiber and reduced GO fiber that can have different application fields including electronic smart textiles, graphene-based membranes, gas adsorption, energy application such as lithium ion battery, and ultrafiltration applications.