Enhancing the performance of 3D porous N-doped carbon in oxygen reduction reaction and supercapacitor via boosting the meso-macropore interconnectivity using the “exsolved” dual-template

The rational design and preparation of hierarchically porous carbons feature high on the wish list of academia and industry alike. However, creating interconnected pores of distinct dimensions is no easy task. Starting from the precursor design, we present a novel synthesis strategy of porous carbons that much enhances the pore interconnectivity. The 500 °C pyrolysis of chelated Mg and Fe nitrilotriacetates creates Fe-doped MgO template, sizing 50–400 nm. While embedded in the carbon matrix, these pyrolysis-generated templates undergo an additional phase transformation at the sequential 900 °C pyrolysis, exsolving well-dispersed smaller Fe nanoparticles, typically sizing 5–45 nm, on the MgO surface. This offers a contiguous network of dual templates for meso- and macropores. A simple acid washing yields a hierarchically porous, N-doped carbon with a high specific surface area of 1560 m² g⁻¹ and a high mesopore volume of 1.9 cm³ g⁻¹. This carbon exhibits a half-wave potential of 0.77 V vs. RHE in the oxygen reduction reaction at pH 13. Besides, it also renders a specific capacitance of 321 F g⁻¹ at 5 mV s⁻¹ during the capacitor measurement.