Efficiency enhancement of photoelectrochemical water splitting by heterostructures Ag/MoS2/ZnO photoanode / Chia Mei Yuen

Chia , Mei Yuen (2022) Efficiency enhancement of photoelectrochemical water splitting by heterostructures Ag/MoS2/ZnO photoanode / Chia Mei Yuen. Masters thesis, Universiti Malaya.

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Abstract

Current work focuses on the preparation of Ag/MoS2/ZnO thin film as photoanode and evaluation of its efficiency for photoelectrochemical (PEC) water splitting. The sample is fabricated via facile wet-chemical synthesis method, where seedless hydrothermal growth of zinc oxide (ZnO) nanorods is conducted first followed by decoration of molybdenum disulfide (MoS2) flakes that integrated with silver (Ag) nanoparticles on ZnO nanorod’s surface via drop-coating method. The experimental design is based on cost saving concept without the need of excessive chemicals yet time-consuming seeding process and decoration/integration process. In each stage of samples preparation, the most optimum sample will be selected for to be used as matrix for following stage sample preparation. In first stage, ZnO nanorods were grown on indium doped tin oxide (ITO) via seeding process while that of aluminium doped zinc oxide (AZO) is without seeding process. It is found that although ZnO nanorods grown on ITO have smaller diameter but ZnO nanorods grown on AZO is more stable according to chronoamperometry measurement. In second stage, ZnO nanorods grown on AZO was chosen as matrix for MoS2 flakes decoration and the PEC results shows that ZnO nanorods that was decorated with three layers MoS2 flakes gives the highest photocurrent density. In last stage, Ag nanoparticles (with different weight percentage) were integrated onto MoS2 flakes to form Ag/MoS2 nanocomposite. Thereafter, this nanocomposite is integrated onto ZnO nanorods thin film for PEC application. The presence of Ag has renders plasmonic effect that can significantly reduce the recombination rate of electrons and holes in MoS2, where 20 wt% Ag/MoS2/ZnO gave the best PEC performance, 6 times higher in photoconversion efficiency and 8 times higher in hydrogen gas production is observed as-compared to the results of bare ZnO nanorods.

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