CdS nanoparticles sensitization of Al-doped ZnO nanorod array thin film with hydrogen treatment as an ITO/FTO-free photoanode for solar water splitting

Chih-Hsiung Hsu,Dong-Hwang Chen

doi:10.1186/1556-276x-7-593

Abstract

Aluminum-doped zinc oxide (AZO) nanorod array thin film with hydrogen treatment possesses the functions of transparent conducting oxide thin film and 1-D nanostructured semiconductor simultaneously. To enhance the absorption in the visible light region, it is sensitized by cadmium sulfide (CdS) nanoparticles which efficiently increase the absorption around 460 nm. The CdS nanoparticles-sensitized AZO nanorod array thin film with hydrogen treatment exhibits significantly improved photoelectrochemical property. After further heat treatment, a maximum short current density of 5.03 mA cm−2 is obtained under illumination. They not only are much higher than those without CdS nanoparticles sensitization and those without Al-doping and/or hydrogen treatment, but also comparable and even slightly superior to some earlier works for the CdS-sensitized zinc oxide nanorod array thin films with indium tin oxide (ITO) or fluorine-doped tin oxide (FTO) as substrates. This demonstrated successfully that the AZO nanorod array thin film with hydrogen treatment is quite suitable as an ITO/FTO-free photoanode and has great potentials in solar water splitting after sensitization by quantum dots capable of visible light absorption.

Highlights

In recent years, hydrogen energy has found increased attention as a renewable and clean energy source in scientific community and government organizations [1,2,3]
It was found that the chemical bath deposition of cadmium sulfide (CdS) nanoparticles did not destroy the 1-D morphology of Aluminum-doped zinc oxide (AZO) nanorod array thin films
The AZO nanorod array thin film with hydrogen treatment has been sensitized by CdS nanoparticles successfully via chemical bath deposition as a novel indium tin oxide (ITO)/FTOfree composite photoelectrode for solar water splitting

Summary

Introduction

Hydrogen energy has found increased attention as a renewable and clean energy source in scientific community and government organizations [1,2,3]. Its energy-band structure and physical properties are similar to those of TiO2, but it has higher electronic mobility which is favorable for electron transport. It has the potential as an alternate of TiO2 in photovoltaic or photoelectrochemical devices [13]. Both TiO2 and ZnO are not photocatalytic in the visible light region. Since most of the solar frequency spectrum intensity is located in the wavelength range of 400–800 nm, the drawback of nonabsorbing ability in the visible light region significantly limited their hydrogen generation efficiency in the photoelectrochemical cells [14]. To enhance the charge-transport property by increasing the direct electron conduction, the other important strategy was the development of their 1-D nanostructures such as nanorods [24,31,32], nanowires [16,21,22,26,33], and nanotubes [25,34,35]

Methods

Results

Conclusion