Trends in Reactivity of Electrodeposited 3D Transition Metals on Gold Revealed by Operando Soft X -Ray Absorption Spectroscopy During Water Splitting
J. J. Velasco-Vélez1,2, Travis E. Jones1, Verena Pfeifer1, Chung-Li Dong3,4, Yu-Xun Chen3, Chieh-Ming Chen3, Hsin-Yu Chen3, Ying-Rui Lu3, Jin-Ming Chen4, R. Schlögl1,2, A. Knop-Gericke1, 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
* presenting author:Cheng-Hao Chuang,
We activated gold electrodes for their use as electrocatalyst for water splitting by
electrodepositing Cu, Ni and Co. A combination of operando X-ray absorption spectroscopy and potentiometric control under aqueous conditions revealed the trends in reactivity yielded by these electrodes, which are directly associated with the cross- and overpotentials as well as the occupancy of the 3d orbitals. It was found that under anodic polarization the materials electrodeposited on gold suffer from a lack of stability, while under cathodic polarization they exhibit stable behavior. The observed activity is strongly related to the lack of stability shown by these composites under anodic polarization revealing a dynamic process ruled by corrosion. By operando X-ray absorption, we established that the overall enhancement of the activity for the oxygen evolution reaction is directly attributable to the cross-potential and corrosion process of the electrodeposited materials. It is associated with the high potential deposition, which is the origin of the incipient oxidation-corrosion resistance of the lattice.We conclude that the observed trends in the total current are directly associated with the loss of oxygen in the metal-oxide lattice and the subsequent dissolution of metallic ions in the electrolyte under anodic polarization.

Keywords: In-situ liquid cell, X-ray Absorption spectrum, Electrochemical reaction, EC-STM, Water splitting