2022 Forgash Scholar
Jishnudas Chakkamalayath
Interfacial Processes in Perovskite-Metal Hybrid Structure for Photocatalytic Applications
Department of Chemistry and Biochemistry
Faculty Advisor: Prashant Kamat
Semiconductor-metal heterostructures are widely used in photocatalytic water splitting and other light-driven chemical transformations.[1] The presence of a noble metals such as gold at the semiconductor surface can allow the capture of photogenerated electrons and facilitates overall charge separation. The photocatalytic performance of such a noble metal-modified semiconductor can lower the overpotential for reduction of H+ ions to produce clean hydrogen (H2) for renewable energy. CsPbBr3 nanocrystals are a nanoscale metal halide perovskite material which offer a wide variety of useful properties for photocatalysis, including high luminescence, high absorption coefficient and defect tolerance. Modification of CsPbBr3 with a noble metal such as gold (CsPbBr3-Au) to form a hybrid structure can further increase its photocatalytic ability.
The design of CsPbBr3-Au was recently reported from our group and the electron transfer from CsPbBr3 to Au was established. However, the Au nanoparticles are ejected from the surface of CsPbBr3 and aggregate to form large nanoparticles under photoirradiation making the hybrid structure unstable [2]. To remedy this issue, in this project, I will design a photostable CsPbBr3-Au heterostructure. This will be achieved by using a thin CdS shell around CsPbBr3 making it tolerant to polar solvents [3] and then ligating it with bifunctional ligands. The bifunctional ligands will ensure strong binding between the perovskite and metal. This project will also explore the effect of distance between Au and perovskite and size of the Au nanoparticles on potential electron/energy transfer. This will give the optimum conditions to employ CsPbBr3-Au hybrid structure in photocatalysis and photovoltaics.
Project Objectives
The primary objective of this project is to design stable CsPbBr3/CdS-Au heterostructure and elucidate the interfacial processes for photocatalytic applications.
Objective 1: CsPbBr3/CdS will be synthesized and capped with bifunctional ligands. Au nanoparticles will be anchored on the perovskite structures with the help of thiol group in the bifunctional ligands. Transmission Electron Microscopy (TEM) analysis will be utilized to confirm the formation of heterostructure.
Objective 2: Next, absorption and photoluminescence measurements will be carried out on CsPbBr3/CdS nanocrystals and CsPbBr3/CdS-Au hybrid structures to investigate how the optical properties change in the presence of Au nanoparticles and the photostability of the hybrid structures.
Objective 3: Excited-state behavior will be monitored using femtosecond transient absorption measurements. Coupling the analysis with absorption and photoluminescence measurements, the presence of energy or electron transfer will be established.
Objective 4: The chain length of the bifunctional ligands will be varied by using cysteamine (short chain) and 11-mercaptoundecanoic acid (long chain) and also the size of the Au nanoparticles will be varied to establish the dependence of size of the metal and distance in the electron/energy transfer processes.
[1] Kamat et al., J. Phys. Chem. B 2002
[2] Chakkamalayath et al., J. Phys. Chem. C 2021
[3] Kipkorir et al., Chem. Sci. 2021