In situ and operando observation of surface oxides during oxygen evolution reaction on copper

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 Ȃ400 mV above the OER onset. The presence of CuO, Cu 2 O and Cu 4 O 3 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.

Application of In Situ Techniques for the Characterization of NiFe‐Based Oxygen Evolution Reaction (OER) Electrocatalysts

“…During OER, the metal oxide radicals considered as the catalytic intermediates for O À Ob ond formation are formed at the oxide/electrolyte interface. [16,[64][65][66][67][68] Thus,c hanges of valence state during OER monitored by in situ XAS may reflect these transition metal oxide radicals.However,XAS is abulk sensitive technique,soonly an average valence state of…”

Alkaline manganese electrochemistry studied byin situandoperandospectroscopic methods – metal dissolution, oxide formation and oxygen evolution

“…In former studies our group successfully employed in situ spectroscopic ellipsometry (SE) to probe metal supported oxide layer thicknesses simultaneously with spectral changes that can be attributed to composition changes in electrochemical setups. [24][25][26] It was shown that passive oxide films forming on Cu dissolve because of single charge oxygen vacancy formation during the OER. 25 In situ and operando measurements on metallic Cu showed that metastable Cu 4 O 3 forms before the oxide dissolution.…”

State of the Surface of Antibacterial Copper in Phosphate Buffered Saline

“…In comparable works in NaOH, 17,53 no peak at ≈300 cm −1 was observed. Phosphate peaks around 1000 cm −1 are were not observed in the presence of this peak.…”

“…3) is qualitatively different from the ones obtained in alkaline environment. 17,53 Fig. 3a shows absorption spectra obtained during a CV experiment.…”