Abstract
Efficient solar driven photoelectrochemical (PEC) response by enhancing charge separation has attracted great interest in the hydrogen generation application. The formation of one-dimensional ZnO nanorod structure without bundling is essential for high efficiency in PEC response. In this present research work, ZnO nanorod with an average 500 nm in length and average diameter of about 75 nm was successfully formed via electrodeposition method in 0.05 mM ZnCl2 and 0.1 M KCl electrolyte at 1 V for 60 min under 70 °C condition. Continuous efforts have been exerted to further improve the solar driven PEC response by incorporating an optimum content of TiO2 into ZnO nanorod using dip-coating technique. It was found that 0.25 at % of TiO2 loaded on ZnO nanorod film demonstrated a maximum photocurrent density of 19.78 mA/cm2 (with V vs. Ag/AgCl) under UV illumination and 14.75 mA/cm2 (with V vs. Ag/AgCl) under solar illumination with photoconversion efficiency ~2.9% (UV illumination) and ~4.3% (solar illumination). This performance was approximately 3–4 times higher than ZnO film itself. An enhancement of photocurrent density and photoconversion efficiency occurred due to the sufficient Ti element within TiO2-ZnO nanorod film, which acted as an effective mediator to trap the photo-induced electrons and minimize the recombination of charge carriers. Besides, phenomenon of charge-separation effect at type-II band alignment of Zn and Ti could further enhance the charge carrier transportation during illumination.
Highlights
ZnO nanostructure is a rapidly developing metal oxide
An enhancement of photocurrent density and photoconversion efficiency occurred due to the sufficient Ti element within TiO2 -ZnO nanorod film, which acted as an effective mediator to trap the photo-induced electrons and minimize the recombination of charge carriers
Copious researches proved that performance of ZnO nanorod photocatalyst could be improved by coupling with another semiconductor photocatalyst [1,2]
Summary
ZnO nanostructure is a rapidly developing metal oxide. With its vast nano-architecture, ZnO nanorod shape is the most studied photocatalyst in photoelectrochemical (PEC) response. Noticeable limitation, its poor solar illumination absorption and rapid recombination charge carrier losses, hinder further practice in electronic application. Copious researches proved that performance of ZnO nanorod photocatalyst (solar illumination absorption and recombination of charge carrier losses) could be improved by coupling with another semiconductor photocatalyst [1,2]. The objective of this research work is to study the PEC system performance from TiO2 -ZnO nanocomposite photoelectrode under ultraviolet (UV) and solar illumination. The novelty lies via the simple combination of electrodeposition and dip-coating that have not been approached by any other researcher (Table 1)
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