Iron−nitrogen-coordinated carbon-supported (FeNC) catalysts have been explored for application as oxygen depolarized cathode (ODC) catalysts that perform oxygen reduction reaction (ORR) in electrochemical chlorine production systems. One important requirement for ODC catalysts is the resistance to poisoning of their ORR active sites in the presence of chloride anions. This work combines the use of experimental and computational methods to study the effect of exposure of the FeNC catalyst to chloride anions. Electrochemical measurements indicate partially reversible poisoning of the FeNC catalyst in the presence of chloride anions under ORR conditions. Calculations performed using density functional theory on various FeN x C y site models are used to study competitive adsorption between the Cl − anions and O 2 via both direct nonelectrochemical adsorption of O 2 and via a proton-electron transfer step to form OOH* through the ORR associative mechanism. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy measurements together with density functional theory predictions of binding energies and Bader charges indicate a poisoning effect caused by adsorption of Cl − anions on the Fe-centered active sites of FeNC catalysts. The results presented in this work also help explain the partial poisoning effect in FeNC catalysts, wherein certain FeN x C y sites are poisoned by Cl − , while others are not. For some sites, the Cl − poisoning effect is found to be reversed when the applied potential reaches ∼0 V versus the reference hydrogen electrode.

Nitrogen-doped carbon nanostructures (CN x ) have been shown to be promising catalysts to replace Pt-based materials for oxygen reduction reaction (ORR) in PEM fuel cell cathodes. This work reports the use of a combination of post-reaction X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) aimed at examining changes to the nitrogen species in CN x after potential application in an oxygen saturated acidic electrolyte. The results hence obtained reveal interesting changes to the pyridinic, quaternary and pyridinic N + O À binding energy envelopes as a result of protonation of sites and formation of ORR intermediates after the CN x electrodes were subjected to electrochemical potential holds in the kinetic and mass transfer limited regimes of the ORR cyclic voltammogram of the catalyst.

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