Fig. 1: Synthetic illustration and characterization of core-shell structured catalysts.

a Schematic illustration of the synthesis for core-shell structured catalysts. b, d TEM images of TiO2/C3N4 and TiO2/C2N, respectively. c, e TEM-EDS mapping images of TiO2/C3N4 and TiO2/C2N, respectively. f Raman spectra (inset: magnification of local areas) of TiO2, TiO2/C3N4, and TiO2/C2N. g Solid-state 13C nuclear magnetic resonance (NMR) spectra of TiO2/C3N4 and TiO2/C2N. h O 1s XPS spectra of TiO2, TiO2/C3N4, and TiO2/C2N. i Pore size distributions of TiO2/C3N4 and TiO2/C2N.