Direct Growth of Nitrogen-Doped Carbon Quantum Dots on Co(9)S(8) Passivated on Cotton Fabric as an Efficient Photoelectrode for Water Treatment

[Image: see text] Heterogeneous growth of photocatalysts on different porous substrates is a solution to avoid secondary pollution caused by composite photocatalysts themselves. However, the heterogeneous growth of composite photocatalysts with nitrogen-doped carbon quantum dots (NCQDs) inclusions—introduced during synthesis—impedes the direct growth on the substrate. To overcome this problem, NCQDs were grown on a Co(9)S(8) (NCQDs-G@Co(9)S(8)) layer, decorated on cotton fabric. This optimal coupling mode of NCQDs and Co(9)S(8) showed 54% degradation, compared to 33% dye degradation via NCQDs-doped Co(9)S(8) (NCQDs-D@Co(9)S(8)). The change in the crystal structure and its lower loading on fabric results in significantly lower performance of NCQDs-D@Co(9)S(8). Even with the combination of both surface growth and doping (NCQDs-DG@Co(9)S(8)), the performance was still limited to 42%. In addition, the optimum growth concentration of NCQDs on Co(9)S(8) was observed for 7.5 w/w %, resulting in 92% photocatalytic activity (PCA) in 80 min. Comparing different surface states formed in NCQDs using different solvents, water-based surface states (oxygen-rich surface) are most suitable for the dye degradation. NCQDs-G@Co(9)S(8) also offers 67% Cr-VI reduction to Cr-III, showing its suitability for both inorganic and organic compounds. Better electrode performance was related to suitable charge separation of the composite, where –OH groups mainly contribute in the photocatalytic dye degradation..