Three-Electrode Liquid Reaction Cells combined with Ambient Pressure X-ray Photoelectron Spectroscopy for Electrochemistry Applications in Energy Materials

Chia-Hsin Wang^1*, Chueh-Cheng Yang^1,2, Yuan-Chieh Tseng², Pongsatorn Patta^1,3, Yu-Hsu Chang³

¹Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan
²Department of Materials Science and Engineering, National Yang-Ming Chiao Tung University, Hsinchu, Taiwan
³Department of Mineral resources engineering, National Taipei University of Technology, Taipei, Taiwan

* Presenter:Chia-Hsin Wang, email:wang.ch@nsrrc.org.tw

(Near) Ambient pressure X-ray photoelectron spectroscopy (APXPS) has been considered one of the important surface science technologies to study the chemical state and elemental composition evolution of the materials’ surface within the ten nm under in-situ or in an operando environment. The APXPS end station with the backfilled chamber has been used to perform the gas-solid heterogeneous reaction in several mbar pressure range at TLS BL24A since 2017. Here, we will report three-electrode liquid cells developed at the APXPS end station for liquid-solid reaction, especially in electrochemistry applications for energy materials. In the beginning, a three-electrode static liquid cell containing 140 l acid electrolyte sealed by a Nafion membrane pre-coated electrocatalysts as a working electrode can be transferred into an APXPS chamber without extensively modifying the existing setup to carry out operand XPS measurements during the electrochemistry reactions. The oxidation species evolution on the Pt catalyst layers during the oxygen evolution reaction (OER) has been investigated by the static liquid cell combined with APXPS. According to operando XPS measurements, including depth-profile analysis and valence band spectra, we can conclude that the metallic Pt catalysts with a mesoporous thin layer composed of mix-valent oxidation species enhanced the adsorption ability of water to form hydroxyl groups and the OER activity was boosted through the interface of metallic Pt and mesoporous thin layers. Moreover, a continuous-flow liquid cell was developed and combined on the APXPS chamber for carrying out the long-time operando XPS measurements recently. The zinc substitution iron cobaltite-based spinel structure (ZnxFe1-xCo2O4) with a different amount of Zn substitution (0 < x < 0.6 with steps of 0.2) supported on nickel foam was synthesized and served as electrocatalysts in alkaline solution. In operando APXPS results show the highest Co (IV) percentage in Co 2p spectra, approximately 56%, and an increase of superoxide on the surface in O 1s spectra. We proposed that the Co (IV) and superoxide species are the important intermediates in the OER for iron cobaltite-based spinel structure catalyst to produce oxygen. The results obtained from liquid reaction cells combined with APXPS provide new insights into the OER process and guide the better OER performance materials design.

Keywords: Ambient pressure X-ray photoelectron spectroscopy, Oxygen evolution reaction, Liquid reaction cell, electrochemistry reaction