In situ and operando observation of surface oxides during oxygen evolution reaction on copper. (10th May 2017)

• Record Type: Journal Article
• Authors: Toparli, Cigdem; Sarfraz, Adnan; Wieck, Andreas D.; Rohwerder, Michael; Erbe, Andreas
• Is Part Of: Electrochimica acta. Volume 236(2017)
• Page Start: 104
• Page End: 115
• Publication Date: 2017-05-10
• Subjects: Defect formation -- Passivity -- Transpassivity -- Oxygen evolution reaction -- Copper oxides; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2017.03.137
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract : Graphical abstract: Abstract : Highlights: Spectroscopic ellipsometry and Raman spectroscopy used to study surfaces during OER Layer thickness decreases after start of oxygen evolution Photoluminescence shows defect formation during running oxygen evolution Oxide becomes unstable towards defect formation Abstract: Formation and dissolution of oxide on copper under transpassive conditions, i.e. during OER and transpassive dissolution, in alkaline electrolyte was investigated by a combination of electrochemical techniques and in situ and operando Raman and photoluminescence (PL) spectroscopy, as well as spectropscopic ellipsometry. Experiments were conducted under potentiodynamic and potentiostatic polarisation in 0.1M NaOH. In chronoamperometry experiments with steps between potentials, oxide thickness continued increasing beyond the onset of OER. The thickness dropped significantly from >10 nm to <5 nm ≈400 mV above the OER onset. The presence of CuO, Cu2 O and Cu4 O3 was observed by Raman spectroscopy after the onset of OER. Correlating with the thickness drop, strong PL was observed at 1.55 eV, indicating the formation of singly charged oxygen vacancies V O +, following the classical PL spectrum interpretation from the literature. PL observation speaks against vacancy pair coalescence as mechanism of dissolution. After electrochemical experiments, the films were n-type semiconductors, not p-type conductors as expected for copper oxides. Results indicate that transpassive dissolution may be triggered by the instability of the oxide with respect to defect formation.