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Encapsulating Fe3C in carbon layers has emerged as an innovative strategy for protecting Fe3C while preserving its high oxygen reduction activity. However, fundamental questions persist regarding the active sites of encapsulated Fe3C due to the restricted accessibility of oxygen molecules to the metal sites. Herein, the intrinsic electron transfer mechanisms of Fe3C nanoparticles encapsulated in N‐doped carbon materials are unveiled for oxygen reduction electrocatalysis. The precision‐structured C1N1 material is used to synthesize N‐doped carbons with encapsulated Fe3C, significantly enhancing catalytic activity (EONSET = 0.98 V) and achieving near‐100% operational stability. In anion‐exchange membrane fuel cells, an excellent peak power density of 830 mW cm−2 is reached at 60 °C. The experimental and computational results revealed that the presence of Fe3C cores dynamically triggers electron transfer to the outermost carbon layer. This phenomenon amplifies the oxygen reduction reaction performance at N sites, contributing significantly to the observed catalytic enhancement. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new hierarchy-connectivity factor (HCF) is proposed. • Connectivity is determined through gas adsorption–desorption isotherm analysis. • Dual-shape slit-cylinder model is employed to precisely assess the textural properties. • The HCF usefulness is showed using carbon materials for supercapacitors electrodes. To provide a comprehensive description of hierarchical pore networks and optimize micro-mesoporous materials, it is essential to consider pore connectivity as a parameter. This study introduces an innovative hierarchy-connectivity factor (HCF) that includes the volume, size, and connectivity data of pores within the pore network. This study covers micro-mesoporous biosourced carbons, with ordered or disordered mesoporous structures, and three commercial activated carbons derived from petroleum coke and biomass. A dual-shape slit-cylinder model was employed to precisely assess the textural properties of these carbons. The proposed methodology evaluates connectivity exclusively through gas adsorption–desorption isotherm analysis, providing a rapid and practical tool for characterizing the porous network of carbon materials. The efficacy of this HCF is demonstrated in the examination of carbon materials functioning as electrodes for supercapacitors. Overall, this research transcends the field of gas adsorption-based studies, highlighting the importance of evaluating the pore network connectivity within carbon materials in order to optimize them for a particular application. Importantly, this contribution could be extended beyond the scope of carbon materials, encompassing a broader spectrum of porous materials. [ABSTRACT FROM AUTHOR]

This study demonstrates that ammonia concentration when doping carbons using hydrothermal treatment has crucial impact on textural properties. The latter translates into an improvement of the electrochemical performance of carbon materials, when used into electrochemical capacitors, especially at high-rate performance. Nitrogen-doped carbons were synthesized by subjecting tannin to hydrothermal carbonization in ammonia solutions of varying concentrations. After carbonization and CO 2 activation, the as-produced activated carbons (ACs) were tested as electrodes for electrochemical capacitors in symmetric configuration using 1 M H 2 SO 4 as aqueous electrolyte. Interestingly, ammonia concentration during the hydrothermal synthesis step did not significantly affect the final N content (ca. 3 and 4 at. %) nor the nitrogen and oxygen functionalities on the surface. However, the use of ammonia had crucial impact on the textural properties developed by CO 2 activation, and therefore on the electrochemical performance of the ACs. The best-performing N-doped AC showed specific electrode capacitance values, based on carbon material, of 212 F g−1 at 0.5 A g−1 and outstanding capacitance retention of ca. 71 % at 40 A g−1. It also showed high cycling stability, with capacitance retention of ca. 96 % after 30,000 cycles. Furthermore, this AC outperformed similar reported materials, achieving a specific energy of 4.6 W h kg−1 at 12.1 kW kg−1. [Display omitted] • Nitrogen doping through ammonia enhances electrochemical properties. • Ammonia concentration does not significantly affect N content or surface chemistry. • Ammonia concentration affects textural properties, boosted post-CO 2 activation. • N-doped tannin-derived carbons exhibit great performance even at high-power demand.. [ABSTRACT FROM AUTHOR]