Construction of novel Z-scheme nitrogen-doped carbon dots/{001} TiO2 nanosheet photocatalysts for broad-spectrum-driven diclofenac degradation: Mechanism insight, products and effects of natural water matrices

The development of broad spectrum UV-visible-near-infrared (NIR) photocatalysts is a primary strategy in the area of photocatalytically mediated pollutant elimination. Herein, we report on a novel broad-spectrum N-doped carbon quantum dot/TiO2 nanosheet with higher surface energy {0 0 1} faceted (NCDS/TNS-001) composites with significantly improved broad-spectrum utilization. Under UV, visible, and near infrared light irradiation, NCDS/TNS-001 exhibited higher photocatalytic activity than those of TNS-001, NCDs/P25, and NCDs/TiO2 with {1 0 1} facets (NCDs/T-101) toward the degradation of diclofenac (DCF). This excellent photocatalytic performance might be attributed to the synergistic effects of the highly active {0 0 1} facets, up-converted fluorescent properties of NCDs, and efficient charge separation induced by fabricated heterostructures. The determination of reactive species revealed that O2 %-was the dominant species during the photocatalytic degradation of DCF. Together with the analysis of the band structure, a potential Z-scheme heterojunction mechanism for NCDs/TNS-001 was deduced. Photocatalytic pathways of the DCF were further proposed based on intermediate identification and TOC detection, which involved decarboxylation, hydroxylation, and ring opening reactions. The sufficient degradation of DCF in natural water matrices indicated that using NCDS/TNS-001 photocatalytic process for the treatment of ambient DCF wastewater is technical possible.