High H2 Evolution from Quantum Cu(II) Nanodot-Doped Two-Dimensional Ultrathin TiO2 Nanosheets with Dominant Exposed {001} Facets for Reforming Glycerol with Multiple Electron Transport Pathways

Two-dimensional (2D) ultrathin TiO 2 nanosheets doped with quantum Cu(II) nanodots (QCNs) were synthesized through an in situ photodeposition for reforming glycerol. The optimized QCNs dopant exhibited favorable H 2 evolution rate of up to 25-fold compared with bare TiO 2 . The prepared QCNs permeated into the homogeneous {001} facets resulting in discontinuous quantum nanodot doping, which was confirmed by energy-dispersive X-ray (EDX) spectroscopy. Analysis suggests that the suppressed recombination rate of the photoinduced electron–hole pair and the prolonged lifetime are benefits for enhancing photocatalytic performance. A photoinduced interfacial charge-transfer (IFCT) effect introduced by doping QCN was certified by electron spin resonance (ESR) spectroscopy. This offered more photoinduced electrons and holes for redox reaction including H 2 production and CO 2 and CO yields. Electrochemical characterizations were carried out to reveal that QCN could improve the photocurrent density and shift the conduction band (CB) potentials to negative direction. With all the characterizations conducted in this paper, a probable mechanism was proposed to represent the multiple charge-transfer pathways. Here, we provide a new modification strategy for designing QCNs/TiO 2 and explore the mechanism involved in 2D ultrathin nanostructures doped with variable-valence metal quantum nanodots. The multiple charge-transfer pathways system applied to photocatalytic H 2 production and environmental waste disposition in a facile and green manner may be further employed to synthesize other variable-valence metal doping systems.