Metal-free broad-spectrum PTCDA/g-C3N4 Z-scheme photocatalysts for enhanced photocatalytic water oxidation

Exploiting highly-efficient, broad-spectrum responsive and noble-metal-free water oxidation photocatalyst is a major challenge in the field of photocatalysis. Herein, we tackle this challenge by synthesizing Z-scheme PTCDA/g-C3N4 photocatalysts, which can absorb light with wavelength short than 600 nm, for visible light photocatalytic O2 production from water. Owing to the evident conduction and valance band energy level difference between PTCDA and g-C3N4, the PTCDA/g-C3N4 photocatalysts exhibit efficient charge carrier separation through a Z-scheme mechanism, as demonstrated by the transient photocurrent responses and time-resolved fluorescence decay spectra analysis. Benefitting from the synergetic effect of the broad visible light absorption capacity and efficient charge separation, the optimized PTCDA/g-C3N4 photocatalyst shows the highest O2 evolution rate of 847 μmol·h−1·g−1 under visible light irradiation in the presence of Co3O4 as a cocatalyst and AgNO3 as the sacrificial reagent. An apparent quantum yield of 4.5% was achieved under monochromatic light irradiation at 420 nm.