Quantum Confinement Controls Photocatalysis: A Free Energy Analysis for Photocatalytic Proton Reduction at CdSe Nanocrystals
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- 作者：Jing Zhao ; Michael A. Holmes ; Frank E. Osterloh
- 刊名：ACS Nano
- 出版年：2013
- 出版时间：May 28, 2013
- 年：2013
- 卷：7
- 期：5
- 页码：4316-4325
- 全文大小：683K
- 年卷期：v.7,no.5(May 28, 2013)
- ISSN：1936-086X
文摘
The ability to adjust the mechanical, optical, magnetic, electric, and chemical properties of materials via the quantum confinement effect is well-understood. Here, we provide the first quantitative analysis of quantum-size-controlled photocatalytic H2 evolution at the semiconductor鈥搒olution interface. Specifically, it is found that the hydrogen evolution rate from illuminated suspended CdSe quantum dots in aqueous sodium sulfite solution depends on nanocrystal size. Photoelectrochemical measurements on CdSe nanocrystal films reveal that the observed reactivity is controlled by the free energy change of the system, as determined by the proton reduction potential and the quasi-Fermi energy of the dots. The corresponding free energy change can be fitted to the photocatalytic activity using a modified Butler鈥揤olmer equation for reaction kinetics. These findings establish a quantitative experimental basis for quantum-confinement-controlled proton reduction with semiconductor nanocrystals. Electrochemical data further indicate that proton reduction occurs at cadmium sites on the dots, and that charge separation in these nanocrystals is controlled by surface effects, not by space charge layers.r>