Bifu Luo

Fabrication of a Ag/Bi3TaO7 Plasmonic Photocatalyst with Enhanced Photocatalytic Activity for Degradation of Tetracycline

A novel Ag/Bi3TaO7 plasmonic photocatalyst has been prepared by a simple photoreduction process. The as-prepared Ag/Bi3TaO7 photocatalyst exhibited an enhanced photocatalytic activity for the degradation of tetracycline (TC) compared to that of a bare Bi3TaO7 catalyst. The 1 wt % Ag-loaded Bi3TaO7 sample showed the highest photocatalytic efficiency for TC degradation (85.42%) compared with those of the other samples. The enhanced photocatalytic activity could be ascribed to the synergistic effect of the surface plasmon resonance caused by Ag nanoparticles. Electrochemical impedance spectroscopy demonstrated that the incorporation of silver nanoparticles onto the Bi3TaO7 surface promoted the separation of photogenerated carriers. In addition, an electron spin resonance (ESR) and trapping experiment revealed that the photoinduced active species hydroxyl radical and superoxide radical were the main active species in the photocatalytic process of TC degradation. The photocatalytic reaction mechanism was discussed by active species trapping and ESR analysis.

Ag-Decorated ATaO3 (A = K, Na) Nanocube Plasmonic Photocatalysts with Enhanced Photocatalytic Water-Splitting Properties

Tantalate semiconductor nanocrystals have been at the forefront of the photocatalytic conversion of solar energy to supply hydrogen owing to their favorable and tunable optical and electronic properties as well as advances in their synthesis. However, a narrow band gap is required for response to improve the efficiency of the photocatalysts. Here we propose an efficient enhancement of the H2 generation under simulated sunlight and visible light irradiation by a dispersion of Ag-decorated KTaO3 and NaTaO3 nanocubes. X-ray diffraction and UV-vis diffuse reflectance spectra are used to characterize the products. Transmission electron microscope (TEM) and high-resolution high-angle annular dark-field scanning TEM (HAADF-STEM) images show that the Ag nanoparticles (NPs) are uniformly loaded on the surfaces of KTaO3 and NaTaO3. The photocatalytic water-splitting results over Ag-decorated KTaO3 and NaTaO3 show that the rate for H2 evolution from aqueous CH3OH solutions is up to 185.60 and 3.54 μmol/h·g under simulated sunlight and the rate for H2 evolution is more than 2 times than that of pure NaTaO3 and KTaO3 materials. However, under purely visible light illumination the highest H2 evolution of 25.94 and 0.83 μmol/h·g is observed in the case of Ag-decorated KTaO3 and NaTaO3 nanocubes. To the best of our knowledge, this is the first time that the photocatalytic water-splitting activity of the prepared Ag-decorated KTaO3 and NaTaO3 nanocubes has been reported.

An in situ photoelectroreduction approach to fabricate Bi/BiOCl heterostructure photocathodes: understanding the role of Bi metal for solar water splitting

This paper presents for the first time a novel method of depositing plasmonic Bi nanoparticles on BiOCl nanosheets (Bi/BiOCl) via insitu photoelectroreduction, and Bi/BiOCl as the photocathode enabled solar water splitting in a TiO2–Bi/BiOCl photoelectrochemical (PEC) system. It is one of the challenges to understand the relationship between the PEC performance and the composite ratio of Bi/BiOCl, and the density functional theory calculation results show that charges obviously transfer from the Bi cluster to the BiOCl (001) surface. The structure of Bi/BiOCl photocathode has been successfully optimized, according to the current–potential curves and charge injection efficiency. The highly enhanced PEC activity could be attributed to the dual roles of Bi nanoparticles in enhancing the charge transfer and surface plasmon resonance (SPR) effect. More importantly, the optimal Bi/BiOCl photocathode achieved a solar hydrogen evolution rate of 2.4 µmol h−1 under full spectrum illumination (100 mW cm−2).

Hydrothermal synthesis of porous rh-In2O3 nanostructures with visible-light-driven photocatalytic degradation of tetracycline

In this paper, well-defined 3D flower-like porous rhombohedral In2O3 (rh-In2O3) nanostructures were successfully synthesized via the hydrothermal method combined with post-thermal treatments. Interestingly, 3D flower-like c-In2O3 nanostructures could also be obtained by simply adjusting the annealing temperature according to this reaction route. The possible growth mechanism of the obtained flower-like In2O3 nanostructures was proposed based on a series of contrasting experimental observations depending on the different reaction conditions as well as our understanding. Whats more, we also investigated the photocatalytic activities of bulk In2O3, 3D flower-like rh-In2O3, and c-In2O3 nanostructures for the degradation of tetracycline (TC) under visible light. Photocatalytic degradation results indicated that 3D flower-like porous rh-In2O3 nanostructures exhibited the highest photocatalytic activities. The possible photocatalytic mechanism for the degradation of TC in 3D flower-like porous rh-In2O3 nanostructures was also discussed.

Enhanced photoelectrochemical and photocatalytic activity by Cu2O/SrTiO3 p–n heterojunction via a facile deposition–precipitation technique

In our study, a new visible-light-driven photocatalyst Cu2O/SrTiO3 (C/S) heterojunction was firstly prepared by a simple, facile and effective deposition–precipitation technique. The particle size of the Cu2O nanoparticle is only about 5 nm and the SrTiO3 (STO) nanocube is about 50 nm when modified by Cu2O nanoparticles. The samples are used as photocatalysts for photodegrading tetracycline (TC) under visible light irradiation. The 9-Cu2O/SrTiO3 (9-C/S) sample heterojunction shows the highest TC degradation ratio (77.65%), which is caused by the photogenerated electrons of the Cu2O nanoparticles moving from the conduction band of Cu2O to that of SrTiO3, resulting in the separation of electrons and holes. This study not only shows a possibility for substituting noble metals with low-cost Cu2O nanoparticles in photocatalytic degradation but also exhibits a facile deposition–precipitation technique for synthesizing narrow/wide band gap photocatalysts.

Facile Preparation of Bi 24 O 31 Cl 10 Nanosheets for Visible-Light-Driven Photocatalytic Degradation of Tetracycline Hydrochloride

Novel visible-light-driven Bi24O31Cl10 nanosheets were firstly prepared via a facile solvothermal method followed a thermal treatment. The physicochemical properties of as-synthesized sample was characterized by X-ray diffraction, X-rays photoelectron spectroscopy, scanning electronic microscopy, transmission electron microscopy, and UV–Vis spectroscopy. The photocatalytic activity of the photocatalyst was evaluated by degradation of tetracycline hydrochloride (TC-HCl) under visible-light irradiation. Results shown that the Bi24O31Cl10 nanosheets exhibited dramatically enhanced photocatalytic activity towards TC-HCl degradation in comparison with the traditional BiOCl and TiO2 (P25). The nanosheets also displayed excellent photochemical stability for efficient removal of TC-HCl. This work provides a simple approach to fabricate the novel Bi-based nanomaterial and will bring about potential application in treatment of antibiotic pollutant.Graphical Abstract

Effective bandgap narrowing of Cu–In–Zn–S quantum dots for photocatalytic H2 production via cocatalyst-alleviated charge recombination

The development of single-component photocatalysts with narrow bandgaps (2.0–3.0 eV) has been one of the most important goals for photocatalytic H2 production, for which I–III–VI multinary sulfides play an important role due to their widely tunable composition-dependent bandgap. However, simultaneous bandgap narrowing and photocatalytic activity enhancement in the I–III–VI sulfides are often difficult to achieve due to increased defect states. Here, a series of Cu–In–Zn–S quantum dots (QDs) were synthesized by a facile hydrothermal method focusing on a more profound understanding of bandgap tuning and the subsequent effect on the photocatalytic process by controlling the Cu content. The bandgap of the QDs can be effectively tuned from 2.90 eV to 1.98 eV with an increasing Cuu2006:u2006In ratio from 0.05u2006:u200610 to 2.5u2006:u200610 and a color change from light yellow to dark red. The QDs show photocatalytic H2 production activity even without any cocatalyst, but it quickly starts to decrease with the Cu/In ratio over 0.1u2006:u200610 (bandgap of 2.59 eV), which highly limits the potential for visible light photocatalysis. Interestingly, Pt-loading effectively enhanced not only the tolerance of Cu incorporation, but also enabled a high H2 production activity even with further bandgap narrowing down to ∼2 eV. The best photocatalytic performance of 456.4 μmol h−1 g−1 was achieved for the Cuu2006:u2006Inu2006:u2006Zn ratio of 1u2006:u200610u2006:u20065 with a bandgap of 2.27 eV. This increased tolerance of Cu content may result from a combined effect of charge separation by Pt as the cocatalyst that alleviated the Cu-induced charge recombination. The enhanced charge separation was proved by the photoluminescence quenching of the QDs with the cocatalyst. Electrochemical impedance spectroscopy was further used to study the charge separation properties of this photocatalytic system. This is the first observation of the cocatalyst-enhanced tolerance of Cu resulting from the competition of cocatalyst-induced charge separation and defect-induced charge recombination in multinary sulfides, which provides an interesting view and design guideline for the development of narrow bandgap photocatalysts.

Fabrication of In2S3/NaTaO3 composites for enhancing the photocatalytic activity toward the degradation of tetracycline

The rapid recombination of electrons and holes in a single photocatalyst largely limits its photocatalytic efficiency. Fabricating a heterojunction with suitable band energy of two different semiconductors is considered to be an effective strategy to address this issue and thus improve its photocatalytic activity. In this work, an In2S3/NaTaO3 composite was prepared by a facile hydrothermal reaction. In comparison with pure NaTaO3 and In2S3, the In2S3/NaTaO3 composite exhibits enhanced photocatalytic efficiency towards the degradation of tetracycline hydrochloride (TC) under simulated solar irradiation. The formation of the heterojunction significantly enhances the transfer and separation efficiencies of photo-generated electrons and holes. This could be validated by transient photocurrent responses and electrochemical impedance spectra. The trapping experiment and electron paramagnetic resonance suggest that the holes and superoxide radicals are the main species in the photocatalytic reaction. Finally, a possible photocatalytic mechanism was proposed based on the experimental results and the energy band diagram between NaTaO3 and In2S3.

One-Step Nickel Foam Assisted Synthesis of Holey G-Carbon Nitride Nanosheets for Efficient Visible-Light Photocatalytic H2 Evolution

Graphitic carbon nitride (g-C3N4) with layered structure represents one of the most promising metal-free photocatalysts. As yet, the direct one-step synthesis of ultrathin g-C3N4 nanosheets remains a challenge. Here, few-layered holey g-C3N4 nanosheets (CNS) were fabricated by simply introducing a piece of nickel foam over the precursors during the heating process. The as-prepared CNS with unique structural advantages exhibited superior photocatalytic water splitting activity (1871.09 μmol h-1 g-1) than bulk g-C3N4 (BCN) under visible light (λ > 420 nm) (≈31 fold). Its outstanding photocatalytic performance originated from the high specific surface area (240.34 m2 g-1) and mesoporous structure, which endows CNS with more active sites, efficient exciton dissociation, and prolonged charge carrier lifetime. Moreover, the obvious upshift of the conduction band leads to a larger thermodynamic driving force for photocatalytic proton reduction. This methodology not only had the advantages for the direct and green synthesis of g-C3N4 nanosheets but also paved a new avenue to modify molecular structure and textural of g-C3N4 for advanced applications.