Role of surface defects on visible light enabled plasmonic photocatalysis in Au–ZnO nanocatalysts

Abstract

Visible light photocatalytic activity of the plasmonic gold-zinc oxide (Au-ZnO) nanorods (NRs) is investigated with respect to the surface defects of the ZnO NRs, controlled by annealing the NRs in ambient at different temperatures. IntroductionPhotocatalysis by nanostructured metal oxides has been extensively explored in the past due to the potential application in controlling the environmental pollutants for complete mineralization. AbstractVisible light photocatalytic activity of the plasmonic gold-zinc oxide (Au-ZnO) nanorods (NRs) is investigated with respect to the surface defects of the ZnO NRs, controlled by annealing the NRs in ambient at different temperatures. Understanding the role of surface defects on the charge transfer behaviour across a metal-semiconductor junction is vital for efficient visible light active photocatalysis. Au nanoparticles (NPs) are in situ deposited on the surface of the ZnO NRs having different surface defect densities, demonstrating efficient harvesting of visible light due to the surface plasmon absorption. The surface defects in the ZnO NRs are probed by using photoluminescence (PL) spectroscopy, X-ray photoemission spectroscopy (XPS), and photo-electro-chemical current-voltage measurements to study the photo-generated charge transfer efficiency across the Au-ZnO Schottky interface. The results show that the surface situated oxygen vacancy sites in the ZnO NRs significantly reduce the charge transfer efficiency across the Au-ZnO Schottky interfaces lowering the photocatalytic activity of the system. Reduction in the oxygen vacancy sites through annealing the ZnO NRs resulted in the enhancement of visible light enabled photocatalytic activity of the Au-ZnO plasmonic nanocatalyst, adding vital insight towards the design of efficient plasmonic photocatalysts. rsc_RA_c5ra16569e higher surface-to-volume ratios resulting in improved catalytic activity compared to their bulk counterparts. Metal oxides, for example, titanium dioxide (TiO 2 ), zinc oxide (ZnO), etc. are commonly used as photocatalysts, and are typically active under ultra-violet (UV) light due to their wide band gap energies. In recent times, designing photocatalysts that can be activated by visible light is one of the major research areas in order to efficiently and cost-effectively utilize them using the sunlight. Activation of wide bandgap metal oxide photocatalysts under visible light irradiation can be achieved in various ways, among which doping with transition metals, 4-6 creating intermediate defects, 7,8 sensitizing with visible light active dyes or other semiconductors materials, 9-11 narrow bandgap semiconductor coupling 12-14 etc. are some of the commonly used methods.Sensitizing the metal oxide photocatalysts with noble metal NPs to harvest visible light utilizing the surface plasmon resonance (SPR) absorption of the metallic NPs, and hence the name plasmonic photocatalysis, is emerging as a new area for designing smart photocatalysts. 15,16 Plasmonic photocatalysis typically involves distribution of ...

Hollow Au‐ZnO/CN Nanocages Derived from ZIF‐8 for Efficient Visible‐Light‐Driven Hydrogen Evolution from Formaldehyde Alkaline Solution

“…Based on the above results and previous work,, , we propose a mechanism of photocatalytic H 2 production from HCHO alkaline solution on hollow Au 0.40 ‐ZnO/CN, as illustrated in Figure . According to this mechanism, the plasmonic Au nanoparticles act as a sensitizer generating hot electrons under visible‐light irradiation.…”

Importance of Plasmonic Heating on Visible Light Driven Photocatalysis of Gold Nanoparticle Decorated Zinc Oxide Nanorods

“…Incorporation of metal NPs, such as gold (Au) and silver (Ag) into the semiconductor photocatalysts brings drastic enhancement in the photocatalytic activity under both ultraviolet (UV) and visible light irradiation, owing to the several advantages offered by the metal-semiconductor composites, such as enhanced visible light harvesting due to the localized SPR effect from the metal NPs, reduced electron-hole (e-h) pair diffusion length, efficient photo-generated charge separation and transfer and localized heating effect from the metal NPs56.…”

Plasmon‐Enhanced Photoluminescence and Photocatalysis Reactions in Metal‐Semiconductor Nanomaterials: UV‐Generated Hot Electron in Gold‐Zinc Oxide

“…Consequently, the coupling interaction between AuNPs and ZnO semiconductor nanostructures have been studied by several researchers, mainly to examine the sensor applications, [21][22][23][24][25] as well as the photocatalytic activity of the hybrid systems. [26][27][28][29][30][31][32][33] The addition of impurities into the ZnO nano-objects leads to the evolution of its structural, photoelectric, and photocatalytic properties. [34][35][36][37] The resulted exciton-plasmon interaction was found to highly affect the near band edge (NBE) emission efficiency of the semiconductor, where previously, PL enhancement or quenching were observed after doping metallic nanoparticles (e. g. Au, Ag) to ZnO.…”