Construction of Z-scheme photocatalyst with p-n heterojunction of molecular semiconductors for enhanced photocatalytic water oxidation

Abstract

Here, the donor-acceptor organic composites of n-type perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and p-type cobalt phthalocyanine (CoPc) semiconductors are firstly synthesized and optimized for photocatalytic oxygen evolution (POE) as catalyst. The POE rate of 12.30 mmol·g−1·h−1 with the apparent quantum yield of 4.00 % at 475 nm can be achieved under visible light (> 420 nm), as compared with 1.58 mmol.g−1.h−1 of PTCDA. Under the full UV-Vis light (> 320 nm), the rate is up to 17.65 mmol·g−1·h−1. The systematical experiments clearly reveal the generation of dual-channel energy transfer of fluorescence resonance from CoPc to PTCDA and electron transfer from oxygen groups in PTCDA to Co atom in CoPc under UV-Vis light irradiation. Consequently, the formation of Z-scheme p/n heterojunction in CoPc/PTCDA composite greatly enhances the POE performance due to the lifetime increase of metal-ligand charge transfer exciton in CoPc (44.83 vs. 2.95 ps) and perylene cationic exciton (20.13 vs. 2.13 ps).