Progressively stimulating carrier motion over transient metal chalcogenide quantum dots towards solar-to-hydrogen conversion

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 1; no. 22; pp. 11926 - 11937
• Main Authors: Zhu, Shi-Cheng, Wang, Zi-Chen, Tang, Bo, Liang, Hao, Liu, Bi-Jian, Li, Shen, Chen, Zhixin, Cheng, Nian-Cai, Xiao, Fang-Xing
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 07.06.2022
• Subjects: absorption; Carrier lifetime; Catalysts; Chalcogenides; Charge transfer; Charge transport; Chemisorption; Density; Doping; Efficiency; energy; Heterostructures; Hydrogen; Hydrogen evolution; hydrogen production; Metal ions; Nickel; Photocatalysis; photocatalysts; photosensitizing agents; Photosynthesis; Protons; Quantum dots; Self-assembly; Separation; synergism; Synergistic effect; Transition metal compounds; Valence band; Water splitting
• ISSN: 2050-7488; 2050-7496; 2050-7496
• DOI: 10.1039/d2ta02755k

The solar-to-hydrogen conversion efficiency in photocatalytic water splitting heavily depends on the accumulation of multiple electrons at the catalytically active sites and rapid charge transport/separation. Herein, we demonstrate the construction of 0D-2D nickel-doped and Ti 3 C 2 T X MXene (MN)-encapsulated transition metal chalcogenide quantum dot (TMC QD:Ni)/Ti 3 C 2 T X MN heterostructures via an elaborate electrostatic self-assembly strategy. The mechanistic studies revealed that the defects induced by atomic-level foreign metal ion doping create a mid-bandgap state, which broadens the optical absorption range and extends the photo-excited carrier lifetime of the TMC QDs. The density functional calculation results verified that Ni 2+ ion doping introduces a donor impurity level and increases the density of state at the valence band maximum, leading to a significant increase in the number of active sites and lower energy barrier for photocatalytic hydrogen evolution. The subsequent self-assembly of TMC QDs:Ni on the Ti 3 C 2 T X MN framework further accelerates the charge separation and transfer due to the formation of an ideal unidirectional electron migration pathway by Ti 3 C 2 T X MN, which functions as an electron-withdrawing mediator. The synergistic effect of Ni 2+ ion doping and Ti 3 C 2 T X MN decoration significantly decreases the charge transfer resistance at the photosensitizer (TMC QD)/co-catalyst (Ti 3 C 2 T X MN) interface and promotes the chemisorption of protons on the catalyst surface, resulting in an excellent solar-to-hydrogen conversion efficiency. Our work provides valuable guidance for the rational design of high-efficiency photocatalysts via precise atomic-level metal ion doping and co-catalyst modulation towards emerging artificial photosynthesis. Metal ion doping and MXene encapsulation for stimulating electron-withdrawing effect are harnessed to boost charge separation towards solar-to-hydrogen conversion.