High-Yield Production of Low-Defect Graphene via Scalable Liquid Exfoliation Using Biodegradable Saponin Surfactant

Scalable synthesis of low-defect graphene through green routes remains a critical bottleneck for industrial applications. We report a biodegradable saponin surfactant extracted from honey locust (HL) that enables high-yield (7.24% over 5 cycles) production of few-layer graphene (≤5 layers) via energy-efficient aqueous-phase exfoliation. Only 0.8 mg/mL of HL surfactant is required to achieve a graphene concentration of 1.02 mg/mL, which is 5 times higher than that achieved using sodium dodecyl sulfonate (SDS) at equivalent dosages. The resulting graphene exhibits ultralow structural defects, as indicated by an ID/IG ratio of 0.15, compared to 0.23–1.37 for synthetic surfactants. Mechanistic studies reveal that HL’s conjugated saponin structure induces spatial repulsion forces, effectively suppressing graphene restacking during centrifugation. The preserved graphene quality enables multifunctional material engineering: (1) oil-absorbent sponges fabricated by dip-coating exhibit 121 g/g adsorption capacity for viscous oils, maintaining >85% efficiency through 15 compression cycles; (2) electrically conductive hair coatings eliminate 86.6% static charges and achieve temperature changes of +1.85 °C/s and −1.07 °C/s at optimal loading, combining aesthetic coloring with enhanced safety. Life-cycle analysis confirms the superiority of HL over petrochemical surfactants in terms of carbon footprint and biodegradability. This work provides a scalable and sustainable approach to graphene production, with potential applications in environmental and wearable technologies.