Meng Li,Huaisuo Yao,Shunyu Yao,Gang Chen,Jingxue Sun
Lattice strain is a new strategy for promoting photocatalytic activity in order to source more sustainable energy. Vacancy-induced strain is an effective tactic for lattice deformation. Herein, a CdS/Bi 2 S 3 heterojunction structure containing sulfur vacancies (CdS/Bi 2 S 3 -V S ) is synthesized by a one-step solvothermal method. When there are sulfur vacancies in the Bi 2 S 3 lattice (Bi 2 S 3 -V S ), the surrounding atoms move toward sulfur vacancies. This phenomenon lengthens the bonds between surrounding atoms, resulting in tensile stress. Strain engineering adjusts the energy band structure to reduce the interface barrier height, thus effectively improving the interface charge transfer rate. Moreover, density functional theory (DFT) calculations explore the influence of different strain levels on the band structure and Gibbs free energy. The strain-regulated band structure provides a new approach and effectively reduce the interface barrier.
Fabrication of hybrid system coupling inorganic semiconductor photosensitizer with molecular catalyst provides a promising approach to achieve highly efficient CO 2 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/Bi 2 S 3 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 CO 2 into CO and H 2 under visible-light irradiation. The sulfur vacancy in CdS surface can be reduced by the formation of CdS/Bi 2 S 3 heterostructure. The content of Bi 2 S 3 can be modulated via tailoring the ion-exchange reaction time. The resulting effect on the performace of CO 2 photoreduction has been investigated in detail. Benefiting from the enhanced separation and utilization of charge carriers, CdS/Bi 2 S 3 -0.5 h/FeTCPP hybrid catalyst exhibits 8.2 times CO yield (1.93 mmol/g/h) and 1.7 times H 2 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/Bi 2 S 3 heterostructure is coupled with FeTCPP. In the CdS/Bi 2 S 3 heterostructure, electrons transfer mainly from the conduction band of CdS to Bi 2 S 3 , while it is mainly from the conduction band of CdS to FeTCPP in the CdS/Bi 2 S 3 /FeTCPP hybrid.
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