• Journal Article

Water Oxidation and Oxygen Monitoring by Cobalt-Modified Fluorine-Doped Tin Oxide Electrodes

Citation

Kent, C. A., Concepcion, J. J., Dares, C. J., Torelli, D. A., Rieth, A. J., Miller, A. S., ... Meyer, T. J. (2013). Water Oxidation and Oxygen Monitoring by Cobalt-Modified Fluorine-Doped Tin Oxide Electrodes. Journal of the American Chemical Society, 135(23), 8432-8435. DOI: 10.1021/ja400616a

Abstract

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