Lignosulfonate-Directed Synthesis of Consubstantial Yolk–Shell Carbon Microspheres with Pollen-Like Surface from Sugar Biomass

The carbon materials with diverse morphologies and structures have attracted much interest for various applications. In this work, by introducing lignosulfonate with PEO-PPO-PEO triblock copolymer P123 as soft templates, unique yolk–shell structure with pollen-like surface of carbon microspheres were innovatively synthesized using xylose as the carbon precursor under hydrothermal carbonization. A mechanism for the yolk–shell carbon microspheres formation was proposed. The associations between lignosulfonate and P123 led to the formation of mixed micelles. Owing to the highly branched structure and steric hindrance effect of lignosulfonate, lignosulfonate preferentially assembled at the outer position of double layers of micelles, while linear structure P123 located at the inner position. The xylose assembly process depended on the hydrogen bond interactions between xylose and P123/lignosulfonate soft templates, which do provide appropriate nucleation and growth sites for the assembled particles and affect the formation process simultaneously. What's more, the xylose underwent dehydration, polymerization, and aromatization stages during the hydrothermal carbonization process until the nucleation took place, leading to the in situ formation of carbon particles. The formation mechanism is attributed to relatively complex synergistic effects and will be promising for guiding unique carbon materials synthesis. Additionally, the carbon materials showed good performance in their application in biochemistry and supercapacitor fields.