Fundamental Mechanistic Origin of ORR Activity in g-C3N5: A Comprehensive Electronic-Scale Analysis of Nitrogen-Vacancy Engineering

다국어 초록 (Multilingual Abstract)

Understanding the fundamental origin of catalytic activity in metal-free carbon nitrides is essential forrational ORR design. Here, we perform a systematic DFT-based analysis to uncover how distinct nitrogen vacancies (N2,N3, N4) fundamentally reshape the structural, electronic, and thermodynamic landscape of g-C3N5. Among allconfigurations, the N2-vacancy shows the lowest formation energy and induces a favorable electronic reconstructionthat balances the adsorption of O*, OOH*, and OH*. Free-energy analysis reveals that only the N2-defective surfaceachieves a near-ideal ORR energy profile with the smallest deviation in ΔG1–ΔG4, whereas N3 and N4 defects generatesevere overbinding and endergonic steps. Electronic descriptors confirm that the N2-vacancy moderates p-band statesand redirects O* adsorption to the more stable N3’ site, establishing the mechanistic origin of its superior activity. Thesefindings provide fundamental design principles for vacancy-engineered, metal-free ORR catalysts.