Highly efficient visible-light driven solar-fuel production over tetra(4-carboxyphenyl)porphyrin iron(III) chloride using CdS/Bi2S3 heterostructure as photosensitizer

Fabrication of hybrid system coupling inorganic semiconductor photosensitizer with molecular catalyst provides a promising approach to achieve highly efficient CO2 reduction into solar fuels, as the semiconductor nanomaterials can meet the prerequisites of visible-light photoresponse and high charge-separation efficiency for achieving high photocatalytic efficiency. In this work, CdS/Bi2S3 heterostructures have been prepared via an ion-exchange reaction and employed as the photosensitizer to couple with tetra(4-carboxyphenyl)porphyrin iron(III) chloride (FeTCPP) molecular catalyst for photoreduction of CO2 into CO and H2 under visible-light irradiation. The sulfur vacancy in CdS surface can be reduced by the formation of CdS/Bi2S3 heterostructure. The content of Bi2S3 can be modulated via tailoring the ion-exchange reaction time. The resulting effect on the performace of CO2 photoreduction has been investigated in detail. Benefiting from the enhanced separation and utilization of charge carriers, CdS/Bi2S3-0.5 h/FeTCPP hybrid catalyst exhibits 8.2 times CO yield (1.93 mmol/g/h) and 1.7 times H2 yield (6.08 mmol/g/h) of CdS/FeTCPP hybrid catalyst. More important, the results of energy level alignment, electron spin resonance and photocatalysis indicate that electron-transfer direction can be changed once the CdS/Bi2S3 heterostructure is coupled with FeTCPP. In the CdS/Bi2S3 heterostructure, electrons transfer mainly from the conduction band of CdS to Bi2S3, while it is mainly from the conduction band of CdS to FeTCPP in the CdS/Bi2S3/FeTCPP hybrid.