The evolution of hierarchical porosity in self-templated nitrogen-doped carbons and its effect on oxygen reduction electrocatalysis

摘要: Pyrolitic self-templating synthesis is an effective method for creating hierarchically porous N-doped carbons. We study the evolution of microstructure in self-templated carbons derived from magnesium nitrilotriacetate, 600–1000 °C temperature range. The materials are characterised using N2 adsorption, Hg intrusion, X-ray diffraction, photoelectron spectroscopy, Raman elemental analysis, scanning electron microscopy and transmission microscopy. display high specific surface areas (up to 1830 m2 g−1), pore volumes 3.1 mL g−1). Interestingly, each porosity type – micro, meso, macro evolves along its own route. Micropore growth most significant between 600 700 °C, yet it slows down stops around 800 °C; this indicates that micropores form by removal tarry matter interstices graphitic sheets, rather than physical/chemical etching these sheets. Mesopores, templated spontaneously forming MgO nanoparticles, become dominant at further agglomeration particles leads macropore templating 900 °C. explained particles, as monitored XRD broadening. Furthermore, degree disorder decreases with pyrolysis temperature, significantly ID/IG ratio dropping 1.36 1.17. Correspondingly, in-plane length crystallites increases series, 14 17 nm. Although nitrogen content 6.9 4.1 at%, pyridinic nitrogens remains constant. then measure performance electrocatalysts oxygen reduction reaction (ORR) pH 13 rotating disk electrode voltammetry electrochemical impedance spectroscopy. Remarkably, ORR activity trend independent concentration or disorder. Instead, governed microstructural parameters, importantly area microporosity.