AVS 62nd International Symposium & Exhibition
    In-Situ Spectroscopy and Microscopy Focus Topic Tuesday Sessions
       Session IS+AS+SA+SS-TuM

Paper IS+AS+SA+SS-TuM3
Probig the Liquid-Solid Interface of polycrystalline Pt in 1.0 M KOH using Ambient Pressure Photoemission Spectroscopy and "Tender" X-rays

Tuesday, October 20, 2015, 8:40 am, Room 211C

Session: In-situ Studies of Solid-liquid Interfaces
Presenter: Marco Favaro, Lawrence Berkeley National Laboratory (LBNL)
Authors: M. Favaro, Lawrence Berkeley National Laboratory (LBNL)
B. Jeon, Lawrence Berkeley National Laboratory (LBNL)
P.N. Ross, Lawrence Berkeley National Laboratory (LBNL)
Z. Hussain, Lawrence Berkeley National Laboratory (LBNL)
J. Yano, Lawrence Berkeley National Laboratory (LBNL)
Z. Liu, Lawrence Berkeley National Laboratory (LBNL)
E.J. Crumlin, Lawrence Berkeley National Laboratory (LBNL)
Correspondent: Click to Email
With the previous success in soft X-ray AP-XPS gas-solid interface1a-e probing, researchers have started to gain insights into the liquid-solid boundaries1d. Taking the cue from these new research frontiers, we have developed on BL 9.3.1 at the Advanced Light Source (LBNL) a new liquid phase AP-XPS system (based on a Scienta R4000 HiPP-2 analyzer) that will shed new light on the understanding of the chemical changes at the electrode surfaces during normal working conditions, leading to a great enhancement of our knowledge on the most important processes in energy conversion and storage2a,b. The combination of this new system with synchrotron radiation in the “tender” X-ray region (between 2 and 7 keV), allows us to probe the interface between thin liquid and solid phases using high kinetic energy photons and then, thanks to the in operando approach, directly track the phenomena occurring at the electrode liquid-solid interface during the electrochemical reactions of interest. The technique developed at BL 9.3.1 allows the study of both gas-liquid and liquid-solid interfaces, for pressures up to a hundred of Torr2a.

In order to deeply investigate the possibilities offered by this new technique and, at the same time, to establish a benchmark, a reference material such as polycrystalline Pt has been studied in 1.0 M KOH electrolyte. In this talk we will demonstrate that it is possible to have fine control of the applied potential2a,b, measuring the core level binding energy shift of the of the oxygen 1s and potassium 2p photoemission lines, according to the applied external potential. Moreover we will discuss the observation, under in operando conditions, of the changes of the surface oxidation state2b of Pt triggered by the applied potential. Thanks to the innovative experimental approach, we have observed the in situ formation of Pt(II) and Pt(IV) species during the oxygen evolution reaction (OER), as well as the reversibility of the surface chemistry passing from anodic to cathodic potentials (up to the hydrogen evolution reaction, HER).

[1] a. Lu et al., Sci. Rep. 2, 715 (2012); b. Zhang et al., Nat. Mat. 9, 944 (2010); c. Axnanda et al., Nano Lett. 13, 6176 (2013); d. Starr et al., Chem. Soc. Rev. 42, 5833 (2013); e. Mudiyanselage et al., Angew. Chem. Int.Ed. 52, 5101 (2013).

[2] a. S. Axnanda, E. Crumlin et al., Sci. Rep., accepted; b. E. Crumlin et al., in preparation.