Construction of p/n-type Z-scheme heterojunctions for photocatalytic CO2 reduction and water splitting

P/N-type Z-scheme heterojunction of Co-PDI/Cu-CuTCPP is prepared by a simple way. • Multifunctional photocatalytic activity of is achieved for POE, PHE and CO 2 RR. • Catalytic activities for POE and CO 2 RR increase by ~3 and ~12 times, respectively. • The overall CO 2 RR in the aqueous phase can be achieved to yield O 2 , CO and CH 4 . • It is found that Co-O-Cu linkage exists and has important role in photocatalysis. Developing a multifunctional system for photocatalytic water splitting (PWS) and carbon dioxide reduction reaction (CO 2 RR) is a promising approach to achieve the green carbon cycling. Here, the p/n-type Z-scheme heterojunction (Co-PDI/Cu-CuTCPP) between cobalt perylene diimide nanorods (Co-PDI) and copper porphyrin metal-organic framework nanosheets (Cu-CuTCPP NSs) is constructed via a cetyltrimethylammonium bromide (CTAB)-assisted physical method. Systematical characterizations prove the existence of Co–O–Cu linkage, π-π interaction, and electrostatic forces between Co-PDI and Cu-CuTCPP. The effect of Co-PDI/Cu-CuTCPP ratio on the optical, photoelectric and electrical properties, as well as multifunctional photocatalytic activity is investigated and analyzed. Under visible light irradiation (λ > 420 nm), the Co-PDI/Cu-CuTCPP composites exhibit the photocatalytic activities of water splitting to H 2 and O 2 , as well as CO 2 RR to CO and CH 4 , respectively. After optimizing photocatalytic system, the oxygen evolution rate of 18.7 mmol·g −1 ·h −1 is reached, which is a 4.4-fold compared that of pure Co-PDI. The photogenerated electron conversion efficiency during CO 2 RR is 12.9-fold higher in Co-PDI/Cu-CuTCPP than in Cu-CuTCPP. Meanwhile, the overall CO 2 RR in the aqueous phase can be achieved without H 2 production. Mechanism studies reveal the photoelectrical conversion process, and confirm the synergistic role between Co-PDI and Cu-CuTCPP. Download: Download high-res image (310KB) Download: Download full-size image