X-ray Photoelectron Spectroscopic Investigation of Plasma Enhanced Chemical Vapor Deposited NiOx, NiOx(OH)y, and CoNiOx,(OH)y: Influence of the Chemical Composition on the Catalytic Activity for the Oxygen Evolution Reaction

We report here the plasma-enhanced chemical vapor deposition and electrocatalytic characterization of pure NiOx and NiOx(OH)(y). Whereas NiOx is deposited if oxygen is used as a reactive gas, the use of air as a reactive gas leads to the deposition of the NiOx(OH)(y), which is electrochemically more active than the NiOx. By recording X-ray photoelectron spectra from the as-deposited catalysts and after their electrochemical investigations, we determined that the electrochemical activity correlates with the amount of hydroxide sites on the surface. Such a behavior was already observed for CoOx and CoOx(OH)(y). As a consequence, CoNiOx(OH)(y) was deposited using air as a reactive gas to study the influence of nickel on the electronic structure of CoOx(OH)(y) and its effect on the electrochemical activity.