Enhanced Photocatalytic Performance and Mechanism of Au@CaTiO3 Composites with Au Nanoparticles Assembled on CaTiO3 Nanocuboids.

Yuxiang Yan,Ruishan Li,Zao Yi,Hua Yang,Xiangxian Wang

doi:10.3390/mi10040254

Abstract

Using P25 as the titanium source and based on a hydrothermal route, we have synthesized CaTiO3 nanocuboids (NCs) with the width of 0.3–0.5 μm and length of 0.8–1.1 μm, and systematically investigated their growth process. Au nanoparticles (NPs) of 3–7 nm in size were assembled on the surface of CaTiO3 NCs via a photocatalytic reduction method to achieve excellent Au@CaTiO3 composite photocatalysts. Various techniques were used to characterize the as-prepared samples, including X-ray powder diffraction (XRD), scanning/transmission electron microscopy (SEM/TEM), diffuse reflectance spectroscopy (UV-vis DRS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Rhodamine B (RhB) in aqueous solution was chosen as the model pollutant to assess the photocatalytic performance of the samples separately under simulated-sunlight, ultraviolet (UV) and visible-light irradiation. Under irradiation of all kinds of light sources, the Au@CaTiO3 composites, particularly the 4.3%Au@CaTiO3 composite, exhibit greatly enhanced photocatalytic performance when compared with bare CaTiO3 NCs. The main roles of Au NPs in the enhanced photocatalytic mechanism of the Au@CaTiO3 composites manifest in the following aspects: (1) Au NPs act as excellent electron sinks to capture the photoexcited electrons in CaTiO3, thus leading to an efficient separation of photoexcited electron/hole pairs in CaTiO3; (2) the electromagnetic field caused by localized surface plasmon resonance (LSPR) of Au NPs could facilitate the generation and separation of electron/hole pairs in CaTiO3; and (3) the LSPR-induced electrons in Au NPs could take part in the photocatalytic reactions.

Highlights

The rapid social development has raised two big issues facing mankind, i.e., environmental pollution and energy shortage
A photocatalytic reduction method was employed to hybridize Au NPs on the surface of CaTiO3 NCs synthesized at 200 ◦C for 24 h. 0.1 g of the as-synthesized CaTiO3 NCs and 0.025 g of ammonium oxalate (AO) were successively added in 80 mL of deionized water
Based on the above experimental results, we propose a possible mechanism to elucidate the enhanced photocatalytic performance of the Au NPs modified CaTiO3 NCs, as schematically depicted Figure 10

Summary

Introduction

The rapid social development has raised two big issues facing mankind, i.e., environmental pollution and energy shortage. It is imperative to remove the organic pollutants and purify water resources via a simple, low-cost, green and non-fossil-consumptive technology. In this sense, semiconductor-based photocatalysis has sparked a great interest due to its potential applications in wastewater treatment [3–8]. Semiconductor-based photocatalysis has sparked a great interest due to its potential applications in wastewater treatment [3–8] This technology allows the use of solar light—a sustainable, inexhaustible and economically attractive energy source—as the power source to degrade organic pollutants. Various strategies have been widely applied to modify semiconductor photocatalysts with the aim of facilitating the photoexcited e−/h+ pair separation and widening their light absorption range [14–20]

Methods

Results

Conclusion