title: Using "Tender" X-ray Ambient Pressure X-Ray Photoelectron Spectroscopy as A Direct Probe of Solid-Liquid Interface.
abstract: We report a new method to probe the solid-liquid interface through the use of a thin liquid layer on a solid surface. An ambient pressure XPS (AP-XPS) endstation that is capable of detecting high kinetic energy photoelectrons (7 keV) at a pressure up to 110 Torr has been constructed and commissioned. Additionally, we have deployed a "dip &pull" method to create a stable nanometers-thick aqueous electrolyte on platinum working electrode surface. Combining the newly constructed AP-XPS system, "dip &pull" approach, with a "tender" X-ray synchrotron source (2 keV-7 keV), we are able to access the interface between liquid and solid dense phases with photoelectrons and directly probe important phenomena occurring at the narrow solid-liquid interface region in an electrochemical system. Using this approach, we have performed electrochemical oxidation of the Pt electrode at an oxygen evolution reaction (OER) potential. Under this potential, we observe the formation of both Pt(2+) and Pt(4+) interfacial species on the Pt working electrode in situ. We believe this thin-film approach and the use of "tender" AP-XPS highlighted in this study is an innovative new approach to probe this key solid-liquid interface region of electrochemistry.
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, United States.
authors.forename: Stephanus
authors.initials: S
authors.lastname: Axnanda
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, United States.
authors.forename: Ethan J
authors.initials: EJ
authors.lastname: Crumlin
authors.affiliation: 1] Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, United States [2] State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China.
authors.forename: Baohua
authors.initials: B
authors.lastname: Mao
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, United States.
authors.forename: Sana
authors.initials: S
authors.lastname: Rani
authors.affiliation: 1] Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, United States [2] State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China.
authors.forename: Rui
authors.initials: R
authors.lastname: Chang
authors.affiliation: VG Scienta, Uppsala SE-752 28, Sweden.
authors.forename: Patrik G
authors.initials: PG
authors.lastname: Karlsson
authors.affiliation: VG Scienta, Uppsala SE-752 28, Sweden.
authors.forename: Mårten O M
authors.initials: MO
authors.lastname: Edwards
authors.affiliation: VG Scienta, Uppsala SE-752 28, Sweden.
authors.forename: Måns
authors.initials: M
authors.lastname: Lundqvist
authors.affiliation: VG Scienta, Uppsala SE-752 28, Sweden.
authors.forename: Robert
authors.initials: R
authors.lastname: Moberg
authors.affiliation: Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, United States.
authors.forename: Phil
authors.initials: P
authors.lastname: Ross
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, United States.
authors.forename: Zahid
authors.initials: Z
authors.lastname: Hussain
authors.affiliation: 1] Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, United States [2] State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China [3] School of Physical Science and Technology, ShanghaiTech University, Shanghai 200031, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Liu