Figure 1
a) The main features of the in situ XPS cell design, (i-v) are detailed in the text. b) The x-ray angle of incidence and take-off of photoelectrons at the IL/WE boundary. c) A photograph of the 3D-printed XPS cell secured to the XPS sample stage, with an Al WE and Pt wire CE and REs.
XPS of Electrochemical Systems
Cyclic voltammetry (CV) measurements were performed in tandem with XPS analysis, with the X-ray beam focussed on the electrode-electrolyte interface at the WE. To focus the x-rays, a line scan of survey spectra was recorded across the boundary between the IL and the WE (Fig. 2.a-b). The boundary was identified where a good signal was measured for both the IL and WE species (F 1s and Al 2p). CV measurements performed at different potential ranges (Fig. 2.c) revealed different Na ion behaviour. For the range 0 – 2 V, there was no changes observed in the Na 1s spectra (Fig. 2.d), whereas for the larger potential range of 0 – 2.2 V, a new reduced species was observed at 2.2 V (Fig. 2.e). This could be due the formation of NaF as part of the CEI. The applied potential also resulted in binding energy shifts for Na 1s, F 1s and Al 2p species, with a negative shift observed for negative potentials.
2a: IL/WE Boundary
Figure 2a: The IL/WE boundary observed using the NEXSA G2 internal microscope camera
2b: Line scan spectra
Figure 2b: Line scan of survey spectra across IL/WE boundary
2c: CV spectra
Figure 2c: Cyclic voltammogram scans were recorded in tandem with the XPS measurements from 0 – 2 V (green) and 0 – 2.2 V (purple)
2d: 0-2V cycling Na 1s
Figure 2d: Na 1s spectra recorded during CV cycling between 0 – 2 V
2e: 0-2.2V cycling Na 1s
Figure 2e: Na 1s spectra recorded during CV cycling between 0 – 2.2 V.
