Surface stoichiometry manipulation enhances solar hydrogen evolution of CdSe quantum dots

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 6; no. 14; pp. 615 - 621
• Main Authors: Huang, Mao-Yong, Li, Xu-Bing, Gao, Yu-Ji, Li, Jian, Wu, Hao-Lin, Zhang, Li-Ping, Tung, Chen-Ho, Wu, Li-Zhu
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2018
• Subjects: Evolution; hydrogen; Hydrogen evolution; hydrogen production; Irradiation; Light irradiation; nickel; Parameter sensitivity; photocatalysis; Quantum dots; Recombination; spectroscopy; Stoichiometry
• ISSN: 2050-7488; 2050-7496; 2050-7496
• DOI: 10.1039/c8ta00385h

Surface stoichiometry is a sensitive parameter affecting the decay dynamics of photogenerated hole-electron pairs of QDs. However, the effect of this manipulation on artificial photocatalytic H 2 evolution is unclear. Here, we report that surface stoichiometry manipulation is a facile and feasible approach for enhancing H 2 photogeneration of QDs. In the absence of an external cocatalyst, a decrease in the surface Se ratio of CdSe QDs from ∼16.7% to ∼4.9% gives a more than 10-fold increase in solar H 2 evolution. Taking Ni( ii ) as an external cocatalyst, CdSe QDs with a surface Se ratio of ∼4.9% can produce ∼1600 ± 151 μmol H 2 gas during 27 h of visible-light irradiation, giving a total turnover number of (1.24 ± 0.12) × 10 5 on CdSe QDs and an apparent quantum yield of 10.1%, which is about 8 times that of CdSe QDs with a surface Se ratio of ∼16.7% under the same conditions. Mechanistic insights obtained by a combination of steady-state and time-resolved spectroscopic techniques indicate that surface stoichiometry exerts a significant influence on the exciton kinetics of CdSe QDs: a higher ratio of surface Se would increase the possibility of exciton recombination through hole trapping, thus depressing the performance of solar H 2 evolution. Surface stoichiometry of QDs is a sensitive parameter affecting the photocatalytic activity of H 2 evolution.