The Electro-Deposition/Dissolution of CuSO4 Aqueous Electrolyte Investigated by in Situ Soft X-ray Absorption Spectroscopy
J. J. Velasco-Vélez1,2, K. Skorupska1, E. Frei2, Yu-Cheng Huang3,4, Chung-Li Dong3, Bing-Jian Su5, Cheng-Jhih Hsu3, Hung-Yu Chou3, Jin-Ming Chen4, Jyh-Fu Lee4, P. Strasser6, R. Schlögl1,2, A. Knop-Gericke2, Cheng-Hao Chuang3*
1Department of Heterogeneous Reactions, Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany
2Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
3Department of Physics, Tamkang University, New Taipei City, Taiwan
4National Synchrotron Radiation Research Center, Hsinchu, Taiwan
5Department of Mechanical Engineering, National Central University, Chungli, Taiwan
6Department of chemistry, Technical University Berlin, Berlin, Germany
* Presenter:Cheng-Hao Chuang,
The electrodeposition nature of copper on a gold electrode in a 4.8 pH CuSO4 solution was inquired using X-ray absorption spectroscopy, electrochemical quartz crystal microbalance and thermal desorption spectroscopy techniques. Our results point out that the electrodeposition of copper prompts the formation of stable oxihydroxide species with a formal oxidation state Cu1+ without the evidence of metallic copper formation (Cu0+). Moreover, the subsequent anodic polarization of Cu2Oaq yields the formation of CuO, in the formal oxidation state Cu2+, which is dissolved at higher anodic potential. It was found that the dissolution process needs less charge than that required for the electrodeposition indicating a non-reversible process most likely due to concomitant water splitting and formation of protons during the electrodeposition.

Keywords: in-situ liquid cell, soft/hard X-ray absorption spectrometer, electrochemical analysis, electrochemical quartz crystal microbalance, thermal desorption spectroscopy