We hypothesize that the carbon shells that form around Ni particles under pyrolysis conditions would both attenuate XPS signal and limit the probe depth to the near-surface region of the particles where a native Ni oxide layer would form and give Ni 2+ signal. Finally, X-ray absorption spectroscopy (XAS) at the Ni K-edge was performed to assess the chemical state and bonding environment of the Ni atoms in the 61 NiPACN samples (Figure ).