Au–Cd1−xZnxS core–alloyed shell nanocrystals: boosting the interfacial charge dynamics by adjusting the shell composition

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2018, Vol.6 (36), p.17503-17513
• Main Authors: Ying-Chih Pu, Wei-Ta, Chen, Mei-Jing, Fang, Yu-Lin, Chen, Kai-An Tsai, Wei-Hao, Lin, Yung-Jung, Hsu
• Format: Article
• Language: English
• Subjects: Charge efficiency; Composition; Conduction; Conduction bands; Core-shell structure; Crystals; Electron transfer; Empirical analysis; Gold; Nanocrystals; Oxidation; Photoluminescence; Photons; Shells; Spectroscopy; Spectrum analysis
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c8ta05539d

Au–Cd1−xZnxS core–shell nanocrystals (NCs) with controllable shell compositions (from x = 0 to x = 0.37) were synthesized by using the hot-injection method. By increasing the mole fraction of ZnS in the Cd1−xZnxS shell, the conduction band of Cd1−xZnxS can be cathodically shifted to cause an increase of energy difference between the conduction band level of the Cd1−xZnxS shell and the Fermi level of the Au core, thereby enlarging the driving force of interfacial electron transfer to enhance the photoelectrochemical (PEC) efficiency. The interfacial charge dynamics of the samples were examined by time-resolved photoluminescence (TRPL) spectroscopy. The results showed that the interfacial electron transfer rate constant (ket) from the Cd1−xZnxS shell to the Au core was increased by 2 orders of magnitude, from 2.41 × 107 to 4.91 × 109 s−1 as the mole fraction of ZnS increased from 0 to 0.37. Furthermore, PEC characterization, including Mott–Schottky analysis and photovoltage decay measurements, illustrated that gradually introducing ZnS into the shell composition of Au–Cd1−xZnxS NCs can modify the band structure and enhance the effectiveness of interfacial ET for advancing the PEC properties. The practical use of Au–Cd1−xZnxS NCs in PEC methanol oxidation was also demonstrated, revealing their promising potential as viable photoelectrodes for various PEC applications. The present study delivers an alternative approach of modulating the interfacial ET dynamics of core–shell MSNs by means of shell composition adjustment. The illustrations provide an empirical guideline to the intelligent design of core–shell metal–semiconductor nanoheterostructures (MSNs) for the desired PEC applications.