Wastewater purification with different precursors of carbon dots dominated titanium dioxide: Mechanism insight

Abstract

Controlled deposition of co-catalysts on the requisite surfaces is highly crucial for myriad applications related to photocatalysis. However, the complex preparation process and different precursors may affect their photocatalytic performance. Here, carbon dots (CDs)-doped TiO2 nanosheets (CDs/TNs), which possess high photocatalytic activity and wastewater purification ability, were synthesized using different precursors of CDs (citric acid: CA and ammonium citrate: AC). Then, the prepared CA-CDs/TNs and AC-CDs/TNs were compared using different techniques. The results illustrated that the particle sizes for AC-CDs and CA-CDs are 1.50 ± 0.204 nm and 3.98 ± 0.37 nm. Compared with AC-CDs, the lattice spacing of CA-CDs is 0.195 nm, which is narrower than that of AC-CDs. Meanwhile, CDs are successfully doped on the surface of TNs. Both CA-CDs/TNs and AC-CDs/TNs exhibit outstanding photodegradation activity and robust stability. And the photocatalytic performance of CDs/TNs increases firstly and then decreases with increasing the amount of CDs. Specially, 0.2CA-CDs/TNs exhibit the highest degradation efficiency, having removed ~91.6% of CR (2 h), 90.2% of RhB (2 h) and 96.1% of TC (1 h), which are 5.70%, 7.13% and 6.7% higher than that of 0.2AC-CDs/TNs. Meanwhile, the removal performance of bright green (BG) and azorubine (ZB) were also performed. As expected, CDs activate TNs to remove BG (91.08% within 150 min) and ZB (86.69% within 4 h) more efficiently. Finally, the feasible degradation pathways of the pollutants are discussed.