Figure 4.

Analysis of the Ni 2p stack of region A1a of the Ni–N–C-high sample. (a) Ni 2p X-ray absorption spectra (XAS) of the particles and the carbonaceous matrix of region A1a of the Ni–N–C-high sample. (b) XAS spectra of Ni(0) NiTPP, O-NiPc, and Ni₃S₂ on absolute optical density (OD1) scales. Note the scaling used to optimize the visibility of the spectral features. Quantitative component maps of (c) Ni(0), (d) NiTPP, and (e) Ni₃S₂ derived from an SVD fit. The grayscale indicates the thickness based on the use of absolute OD1 reference spectra. (f) Rescaled color-coded composite of the Ni(0) (dark red), NiTPP (dark green), and Ni₃S₂ (dark blue) component maps.