Nitrogen Chemistry and Pore Hierarchy Direct ORR Pathways in Polyazine–Derived Carbon Foams

Hierarchically porous, high surface area, nitrogen‐rich carbon foams were prepared by carbonizing aromatic and aliphatic polyazine‐based precursors. By varying precursor chemistry, nitrogen speciation and pore hierarchy were independently tuned, yielding specific surface areas up to 2874 m 2 ·g −1 and nitrogen contents between 0.3 and 6.2 wt %. As a use case, the foams were evaluated as electrocatalysts for the oxygen reduction reaction (ORR) in acidic medium. AliPAZ‐CF exhibits a more positive onset potential (0.60 V vs. RHE), a current density of 1.1 mA·cm −2 at 0.4 V and an H 2 O 2 selectivity of 78% reflecting distinct ORR pathway preferences arising from differences in nitrogen chemistry and pore hierarchy. CO 2 activation increased microporosity and specific surface area but reduced total nitrogen content and H 2 O 2 selectivity, whereas subsequent NH 3 treatment restored nitrogen functionalities, shifted the onset positively and promoted the 4e − ORR pathway. Correlating Raman and x‐ray photoelectron spectroscopy with electrochemistry indicates that pyrrolic/hydrogenated‐pyridinic nitrogen embedded in hierarchical micro/meso/macroporous frameworks favors the selective 2e − ORR to H 2 O 2 , while higher pyridinic nitrogen content combined with increased microporosity directs the reaction toward H 2 O. These results establish mechanistic design rules that link nitrogen configuration and hierarchical porosity to control of the ORR pathway in metal‐free carbon catalysts.