Fig. 2: Synthesis and characterizations of LnNi-PHI.

a Schematic illustration for the synthesis of LnNi-PHI catalysts by cation exchange method. b Amount of nickel and ligand in LnNi-PHI determined by ICP-OES and 1H-NMR analysis. c XRD patterns. d XPS survey spectra. e TEM images. f PL spectra. g Transient photocurrent response. h Schematic drawing of band structures.