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

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.

Enhancing Oxygen Reduction Reaction Catalytic Activity Using a Sub‐Stoichiometric CaTiO3−δ Additive

“…Here, the surface properties and oxidation states of the elements in the CTO compound have been investigated by XPS measurements performed on the most active catalyst composition Pt : CTO 1 : 1 (Figure S2, Supplementary Information). The observed peaks at 346.6 and 350.1 eV (Figure S2a) are related to Ca 2p 3/2 and Ca 2p 1/2 , respectively, confirming the presence of Ca 2+ . With respect to oxygen, both structural and chemisorbed oxygens are detected and the binding energy of O 1s is shifted from 529.8 in a Pt‐free CTO sample (data not shown in this work) to 532.0 eV (Figure S2c) in our Pt : C/CTO sample, suggesting a stronger interaction/coordination of the perovskite metal oxide in the composite catalyst.…”

“…The observed peaks at 346.6 and 350.1 eV ( Figure S2a) are related to Ca 2p 3/2 and Ca 2p 1/2 , respectively, confirming the presence of Ca 2 + . [28] With respect to oxygen, both structural and chemisorbed oxygens are detected and the binding energy of O 1s is shifted from 529.8 in a Pt-free CTO sample (data not shown in this work) to 532.0 eV ( Figure S2c) in our Pt : C/CTO sample, suggesting a stronger interaction/coordination of the perovskite metal oxide in the composite catalyst. The two main peaks observed for the transition metal ( Figure S2b) are attributed to Ti 2p 3/2 at 459.1 eV and to Ti 2p 1/2 at 464.7 eV [28] of the Ti 4 + cationic structure.…”

“…With respect to oxygen, both structural and chemisorbed oxygens are detected and the binding energy of O 1s is shifted from 529.8 in a Pt‐free CTO sample (data not shown in this work) to 532.0 eV (Figure S2c) in our Pt : C/CTO sample, suggesting a stronger interaction/coordination of the perovskite metal oxide in the composite catalyst. The two main peaks observed for the transition metal (Figure S2b) are attributed to Ti 2p 3/2 at 459.1 eV and to Ti 2p 1/2 at 464.7 eV of the Ti 4+ cationic structure. Moreover, an additional small peak at 454.8 eV appears in the Pt/C : CTO spectrum (Figure S2b), likely due to Ti 2+ , confirming the sub‐stoichiometry of the perovskite here proposed.…”

Effect of Ni doping on the structural, optical and photocatalytic activity of MoS2, prepared by Hydrothermal method

“…Such phenomena are leading the excited electrons to move from valance to conduction band in limited period of time. Hence with the increment of Ni contents the photodegradation for both MB and RhB dyes are enriching [36,37]. Figure 7 shows plot of C/C o versus irradiation time (C and C o are the residual and initial concentration dyes) for MB and RhB dyes.…”

NaBH4-Reduction Induced Evolution of Bi Nanoparticles from BiOCl Nanoplates and Construction of Promising Bi@BiOCl Hybrid Photocatalysts

“…The photoexcitation of Bi nanoparticles is ascribed to the localized surface plasmon resonance. It is well established the excited metal nanoparticles can act as excellent electron sinks [69], and as a result, the photoexcited electrons in the CB of BiOCl will be transferred to Bi nanoparticles. Simultaneously, the LSPR-induced electrons in Bi nanoparticles could be also transferred to the CB of BiOCl, as depicted in Figure 14b.…”