Gradient Heating-Induced Bi-Phase Synthesis of Carbon Quantum Dots on Graphene-Coated Carbon Cloth for Efficient Photoelectrocatalysis

The challenges of secondary pollution and limited stability of metallic catalysts/quantum dots that are used for water treatment must be resolved in the emerging ecofriendly environmental systems. Conversely, carbon materials, specifically, conventional carbon quantum dots (C-CQDs) have emerged as an abundant, stable, and biocompatible alternative for visible-light-driven photocatalysts that are used for water treatment. Despite these advantages, the fast charge recombination in quantum-confined systems, complex purification, and limited optoelectronic performance are bottlenecks in the practical application of C-CQDs. To address these issues, we proposed a scalable structural design of C-CQDs with enhanced photocatalytic and diverse optical (fluorescence and absorbance) properties. The synthesis process of CQDs was primarily modified to yield a highly amorphous core carbon quantum dots (AC-CQDs), which was controlled by varying the synthesis temperature. The low initial temperature during the synthesis of the AC-CQDs yields an amorphous core, which provides a high electrical resistance; hence, the indirect recombination occurring through core conductivity is significantly suppressed. The n-p junction was realized in the AC-CQD structure, hence instead of fast recombination, efficient charge channeling was observed. To ensure scalable synthesis and stability, AC-CQDs were directly grown on reduced graphene oxide, which was coated on a carbon fabric to fabricate a textile-structured electrode. Efficient charge separation in the proposed catalyst electrode structure offers significantly improved photoelectrocatalytic activity, i.e., 100% effluent dye degradation in 25 min