X-ray photoelectron spectroscopy (XPS) was used to assess changes in the electronic state of tungsten as the NC films were reduced. Films were prepared for XPS by electrochemically reducing them at a set potential for 10 minutes, followed by washing of the films with dimethyl carbonate to remove excess electrolyte. The potential used to reduce the films corresponds to the lowest potential used to reversibly color the films. Films were transferred from a glovebox to the XPS using an air-free capsule that mechanically couples to a semi-automatic interface on the XPS. This interface evacuates the capsule via differential pumping to prevent air exposure during the transition from high pressure to ultra-high vacuum (patent 9945761). Preventing air exposure allowed for the transfer of the films to the XPS chamber without contamination or discharging due to contact with water or oxygen. The photoemission spectra of the films were measured using a Kratos X-ray Photoelectron Spectrometer -Axis Ultra DLD using an Al Kα source.