Manipulation of Charge-Transfer Kinetics via Ti₃C₂T_x (T = −O) Quantum Dot and N-Doped Carbon Dot Coloading on CdS for Photocatalytic Hydrogen Production

Abstract

Photocatalytic water cracking for hydrogen (H 2 ) evolution is a fascinating technology to tackle the energy and environmental crisis. Here, Ti 3 C 2 T x (T = −O) MXene quantum dots (MQDs) and N-doped carbon dots (NCDs) were interspersed on CdS nanoparticles to promote photocatalytic H 2 production. When loaded with 1.0 wt % MQDs and NCDs, the composite (1.0% MNC) achieves a high H 2 -production rate of 5.64 mmol g −1 h −1 , which reaches 13.12 and 2.83 times those of bare CdS (0.43 mmol g −1 h −1 ) and 1.0% Pt/CdS (1.99 mmol g −1 h −1 ), respectively, and achieved 45.7% apparent quantum efficiency (AQE) at 450 nm. The cycling stability, considered to be the Achilles' heel of the CdS-based photocatalyst, has also been significantly improved. Such an augmentation is mainly ascribed to the electron and hole trapping effect of MQDs and NCDs, respectively, which was demonstrated by systematic characterizations, in association with theoretical calculations. This research paves the way for application of carbonbased quantum dots in photocatalysis and also lays the foundation to develop more MXene-based hybrids for solar energy photocatalysis. KEYWORDS: MXene, Ti 3 C 2 T x (T = −O) MQDs, NCDs, photocatalytic H 2 production, cocatalyst

ZnS/C Dual-Quantum-Dots Heterostructural Nanofibers for High-Performance Photocatalytic H2O2 Production

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S-Scheme and Schottky Junction Synchronous Regulation Boost Hierarchical CdS@Nb2O5/Nb2CTx (MXene) Heterojunction for Photocatalytic H2 Production

“…The work functions (φ) of the photocatalysts were measured by UPS; the value might be calculated by subtracting the photon energy of He I (21.22 eV) from the binding energy of the secondary cutoff edge. ,− As shown in Figure d, the φ of Nb 2 C T x , Nb 2 O 5 /Nb 2 C T x , Nb 2 O 5 , and CdS were estimated to be 4.12, 3.93, 3.71, and 3.82 eV, respectively. On the one hand, it indicated that the Fermi levels ( E F ) of Nb 2 O 5 and CdS were higher than that of Nb 2 C T x (Figure e), so the metallic Nb 2 C T x MXene can build a Schottky junction with Nb 2 O 5 or CdS .…”