期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 135, 期 23, 页码 8432-8435出版社
AMER CHEMICAL SOC
DOI: 10.1021/ja400616a
关键词
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资金
- UNC Center for Solar Fuels, an Energy Frontier Research Center
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0001011]
- ARPA-E Grant [DE-AR0000140]
- RTI International through the Research Triangle Solar Fuels Institute
Electrocatalytic water oxidation occurs at fluoride-doped tin oxide (FTO) electrodes that have been surface-modified by addition of Co(II). On the basis of X-ray photoelectron spectroscopy and transmission electron microscopy measurements, the active surface site appears to be a single site or small-molecule assembly bound as Co(II), with no evidence for cobalt oxide film or cluster formation. On the basis of cyclic voltammetry measurements, surface-bound Co(II) undergoes a pH-dependent 1e(-)/1H(+) oxidation to Co(III), which is followed by pH-dependent catalytic water oxidation. O-2 reduction at FTO occurs at -0.33 V vs NHE, allowing for in situ detection of oxygen as it is formed by water oxidation on the surface. Controlled-potential electrolysis at 1.61 V vs NHE at pH 7.2 resulted in sustained water oxidation catalysis at a current density of 0.16 mA/cm(2) with 29 000 turnovers per site over an electrolysis period of 2 h. The turnover frequency for oxygen production per Co site was 4 s(-1) at an overpotential of 800 mV at pH 7.2. Initial experiments with Co(II) on a mesoporous, high-surface-area nanoFTO electrode increased the current density by a factor of similar to 5
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