Fig. 1: Characterization of metal-free carbocatalyst.
a Proposed formation mechanism of NAC catalysts inside the mesoporous silica template. b DNP-enhanced 15N{1H} CPMAS spectrum of polymer prior to carbonization. c TEM image of NAC-800, where 800 represents the sample preparation temperature. Scale bar, 40 nm. d HAADF-STEM image and EDS mapping of C and N of NAC-800. Scale bar, 40 nm. e DNP-enhanced 15N{1H} CPMAS spectrum of condensed polymers calcined for 10 min at 300 °C. f N1s XPS spectra of NAC catalysts synthesized at different carbonization temperatures, showing pyridinic N (green), pyrrolic N (blue), graphitic N (magenta), and pyridine N-oxide (brown). g Pulsed H2 chemisorption of NAC-800 at 60–360 °C.
