Growth-control of hexagonal CdS-decorated ZnO nanorod arrays with low-temperature preheating treatment for improved properties and efficient photoelectrochemical applications

Huey Jing Tan; Zulkarnain Zainal; Zainal Abidin Talib; Hong Ngee Lim; Suhaidi Shafie; Sin Tee Tan; Noor Nazihah Bahrudin

doi:10.1039/d3ra01492d

Growth-control of hexagonal CdS-decorated ZnO nanorod arrays with low-temperature preheating treatment for improved properties and efficient photoelectrochemical applications

RSC Adv. 2023 May 11;13(21):14393-14411. doi: 10.1039/d3ra01492d. eCollection 2023 May 9.

Authors

Huey Jing Tan¹, Zulkarnain Zainal^{1

2}, Zainal Abidin Talib³, Hong Ngee Lim¹, Suhaidi Shafie⁴, Sin Tee Tan^{5

6}, Noor Nazihah Bahrudin¹

Affiliations

¹ Department of Chemistry, Faculty of Science, Universiti Putra Malaysia 43400 UPM Serdang Selangor Malaysia zulkar@upm.edu.my.
² Nanomaterials Synthesis and Characterization Laboratory, Institute of Nanoscience and Nanotechnology, Universiti Putra Malaysia 43400 UPM Serdang Selangor Malaysia.
³ Department of Physics, College of Natural Sciences, Jeonbuk National University Jeonju-si Jeollabuk-do 54896 Republic of Korea.
⁴ Functional Nanotechnology Devices Laboratory, Institute of Nanoscience and Nanotechnology, Universiti Putra Malaysia 43400 UPM Serdang Selangor Malaysia.
⁵ Department of Physics, Faculty of Science, Universiti Putra Malaysia 43400 UPM Serdang Selangor Malaysia.
⁶ School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia 43600 UKM Bangi Selangor Darul Ehsan Malaysia.

Abstract

The limitations of oxide semiconductor-based solar cells in achieving high energy conversion efficiencies have prompted incessant research efforts towards the creation of efficient heterostructures. Despite its toxicity, no other semiconducting material can fully replace CdS as a versatile visible light-absorbing sensitizer. Herein, we explore the aptness of preheating treatment in the successive ionic layer adsorption and reaction (SILAR) deposition technique and improve the understanding of the principle and the effects of a controlled growth environment on thus-formed CdS thin films. Single hexagonal phases of nanostructured cadmium sulfide (CdS)-sensitized zinc oxide nanorods arrays (ZnO NRs) have been developed without the support of any complexing agent. The influences of film thickness, cationic solution pH and post-thermal treatment temperature on the characteristics of binary photoelectrodes have been investigated experimentally. Interestingly, the preheating-assisted deposition of CdS, which is rarely applied for the SILAR technique, resulted in improved photoelectrochemical performance similar to the post-annealing effect. The X-ray diffraction pattern revealed that optimized ZnO/CdS thin films were polycrystalline with high crystallinity. Examination of the morphology of the fabricated films via field emission scanning electron microscopy showed that film thickness and medium pH altered the growth mechanism of nanoparticles, thereby changing their particle sizes, which had a significant influence on the film's optical behavior. The effectiveness of CdS as a photosensitizer and the band edge alignment for ZnO/CdS heterostructures were evaluated using ultra-violet visible spectroscopy. Facile electron transfer in the binary system as evidenced in electrochemical impedance spectroscopy Nyquist plots, therefore, promotes higher photoelectrochemical efficiencies from 0.40% to 4.30% under visible light illumination as compared with the pristine ZnO NRs photoanode.