A novel cascade utilization of Camellia oleifera shell waste for co-production of xylo-oligosaccharides and high-performance hard carbon: processes and mechanisms.

Abstract

Camellia oleifera shell (COS), a lignin- and hemicellulose-rich cultivation byproduct, offers significant potential for resource extraction. In this study, we developed an integrated biorefinery approach using mild metal chloride-catalyzed hydrothermal pretreatment to vaporize COS waste. Under optimized conditions (0.03 M AlCl₃, 170 °C, 60 min), hemicellulose-rich COS was selectively depolymerized into xylo-oligosaccharides (XOS) with a yield of 49.8 %. This efficient Lewis acid-catalyzed method produced high XOS yields and cellulose- and lignin-enriched solid residues. Compared to untreated samples, these residues, with reduced hemicellulose content, yielded hard carbon with increased interlayer spacing and closed pore structures, exhibiting superior sodium storage ability. This approach contrasts with traditional enzymatic hydrolysis and fermentation pathways. The hard carbon anode was incorporated into sodium-ion batteries, demonstrating practical feasibility with an initial reversible capacity (IRC) of 348 mAh g^-1, an initial coulombic efficiency (ICE) of 70.5 %, and capacity retention of 91.7 % after 100 cycles. This dual-product approach maximizes COS utilization and synergizes renewable chemical production with advanced energy storage, highlighting the unique advantages of our approach to XOS synthesis and material optimization, showcasing a clear advantage over existing single-product pathways.