title: Water oxidation and oxygen monitoring by cobalt-modified fluorine-doped tin oxide electrodes.
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. O2 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 ~5.
authors.affiliation: Department of Chemistry, CB# 3290, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors.forename: Caleb A
authors.initials: CA
authors.lastname: Kent
authors.forename: Javier J
authors.initials: JJ
authors.lastname: Concepcion
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Dares
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Torelli
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Rieth
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Miller
authors.forename: Paul G
authors.initials: PG
authors.lastname: Hoertz
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Meyer
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D004566:Electrodes; D005461:Fluorine / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis* / Q000737:chemistry*; D013499:Surface Properties; D017971:Tin Compounds / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D017971:Tin Compounds; D014867:Water; D005461:Fluorine; D003035:Cobalt; C045358:stannic oxide; D010100:Oxygen