Understanding the Plasmonic Effect of Enhanced Photodegradation with Au Nanoparticle Decorated ZnO Nanosheet Arrays under Visible Light Irradiation

Abstract

Plasmonic-enhanced photocatalysis using visible light is considered a promising strategy for pollution photodegradation. However, there is still a lack of comprehensive and quantitative understanding of the underlying mechanisms and interactions involved. In this study, we employed a two-step process to fabricate arrays of ZnO nanosheets decorated with Au nanoparticles (Au-ZnO NS). Various characterization techniques were used to examine the morphological, structural, and chemical properties of the fabricated Au-ZnO NS array. Furthermore, we systematically investigated the photocatalytic degradation of methyl orange under visible light irradiation using Au-ZnO NS arrays prepared with varying numbers of photochemical reduction cycles. The results indicated that as the number of photochemical reduction cycles increased, the photodegradation efficiency initially increased but subsequently decreased. Under visible light irradiation, the Au-ZnO NS array obtained via four cycles of photochemical reduction exhibits the highest photocatalytic degradation rate of methyl orange 0.00926 min−1, which is six times higher than that of the ZnO NS array. To gain a better understanding of the plasmonic effect on photodegradation performance, we utilized electromagnetic simulations to quantitatively investigate the enhancement of electric fields in the Au-ZnO NS array. The simulations clearly presented the nonlinear dependencies of electric field intensity on the distribution of Au nanoparticles and the wavelength of radiation light, leading to a nonlinear enhancement of hot electron injection and eventual plasmonic photodegradation. The simulated model, corresponding to four cycles of photochemical reduction, exhibits the highest electric field intensity at 550 nm, which can be attributed to its strong plasmonic effect. This work provides mechanistic insights into plasmonic photocatalysts for utilizing visible light and represents a promising strategy for the rational design of high-performance visible light photocatalysts.