期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 138, 期 8, 页码 2705-2711出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.5b12069
关键词
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资金
- 973 project [2013CB632405]
- National Natural Science Foundation of China (NSFC) [21590811, 21137004, 21525729, 21221002]
- Strategic Priority Research Program of Chinese Academy of Sciences [XDA09030200]
Hematite is a promising material for solar water splitting; however, high efficiency remains elusive because of the kinetic limitations of interfacial charge transfer. Here, we demonstrate the pivotal role of proton transfer in water oxidation on hematite photoanodes using photoelectrochemical (PEC) characterization, the H/D kinetic isotope effect (KIE), and electrochemical impedance spectroscopy (EIS). We observed a concerted proton-electron transfer (CPET) characteristic for the rate-determining interfacial hole transfer, where electron transfer (ET) from molecular water to a surface-trapped hole was accompanied by proton transfer (PT) to a solvent water molecule, demonstrating a substantial KIE (similar to 3.5). The temperature dependency of KIE revealed a highly flexible proton transfer channel along the hydrogen bond at the hematite/electrolyte interface. A mechanistic transition in the rate-determining step from CPET to ET occurred after OH- became the dominant hole acceptor. We further modified the proton electron transfer sequence with appropriate proton acceptors (buffer bases) and achieved a greater than 4-fold increase in the PEC water oxidation efficiency on a hematite photoanode.
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