Recent Advances in Plasmonic Photocatalysis Based on TiO2 and Noble Metal Nanoparticles for Energy Conversion, Environmental Remediation, and Organic Synthesis

Plasmonic photocatalysis has emerged as a prominent and growing field. It enables the efficient use of sunlight as an abundant and renewable energy source to drive a myriad of chemical reactions. For instance, plasmonic photocatalysis in materials comprising TiO₂ and plasmonic nanoparticles (NPs) enables effective charge carrier separation and the tuning of optical response to longer wavelength regions (visible and near infrared). In fact, TiO₂ -based materials and plasmonic effects are at the forefront of heterogeneous photocatalysis, having applications in energy conversion, production of liquid fuels, wastewater treatment, nitrogen fixation, and organic synthesis. This review aims to comprehensively summarize the fundamentals and to provide the guidelines for future work in the field of TiO₂ -based plasmonic photocatalysis comprising the above-mentioned applications. The concepts and state-of-the-art description of important parameters including the formation of Schottky junctions, hot electron generation and transfer, near field electromagnetic enhancement, plasmon resonance energy transfer, scattering, and photothermal heating effects have been covered in this review. Synthetic approaches and the effect of various physicochemical parameters in plasmon-mediated TiO₂ -based materials on performances are discussed. It is envisioned that this review may inspire and provide insights into the rational development of the next generation of TiO₂ -based plasmonic photocatalysts with target performances and enhanced selectivities.

A comparative study in single- and binary-contaminant systems: the photodegradation of tetracycline and imidacloprid on flower-shaped Ag/AgBr/BiOBr under visible-light irradiation

A synergistic effect demonstrated in binary-contaminant systems is shown to be caused by the mutually complementary utilization of active species during photodegradation.

Synthesis of Bi₂S₃/BiVO₄ Heterojunction with a One-Step Hydrothermal Method Based on pH Control and the Evaluation of Visible-Light Photocatalytic Performance

The band gaps of bismuth vanadate (BiVO₄) and bismuth sulfide (Bi₂S₃) are about 2.40 eV and 1.30 eV, respectively. Although both BiVO₄ and Bi₂S₃ are capable of strong visible light absorption, electron–hole recombination occurs easily. To solve this problem, we designed a one-step hydrothermal method for synthesizing a Bismuth sulfide (Bi₂S₃)/Bismuth vanadate (BiVO₄) heterojunction using polyvinylpyrrolidone K-30 (PVP) as a structure-directing agent, and 2-Amino-3-mercaptopropanoic acid (l-cysteine) as a sulfur source. The pH of the reaction solution was regulated to yield different products: when the pH was 7.5, only monoclinic BiVO₄ was produced (sample 7.5); when the pH was 8.0 or 8.5, both Bi₂S₃ and BiVO₄ were produced (samples 8.0 and 8.5); and when the pH was 9.0, only Bi₂S₃ was produced (sample 9.0). In sample 8.0, Bi₂S₃ and BiVO₄ were closely integrated with each other, with Bi₂S₃ particles formed on the surface of concentric BiVO₄ layers, but the two compounds grew separately in a pH solution of 8.5. Visible-light photocatalytic degradation experiments demonstrated that the degradation efficiency of the Bi₂S₃/BiVO₄ heterojunction was highest when prepared under a pH of 8.0. The initial rhodamine B in the solution (5 mg/L) was completely degraded within three hours. Recycling experiments verified the high stability of Bi₂S₃/BiVO₄. The synthesis method proposed in this paper is expected to enable large-scale and practical use of Bi₂S₃/BiVO₄.

Anchoring Tailored Low-Index Faceted BiOBr Nanoplates onto TiO2 Nanorods to Enhance the Stability and Visible-Light-Driven Catalytic Activity

In this work, a fantastic one-dimensional (1D) BiOBr/TiO₂ nanorod (NR) heterojunction composite was rationally proposed and designed from the perspective of molecular and interface engineering. The fabricated intimately connected interfacial heterojunction between two-dimensional BiOBr nanoplates and 1D TiO₂ NRs acts as an interfacial nanochannel to promote efficient interfacial charge migration and separation of photogenerated electron-hole pairs. As a result, 1D BiOBr/TiO₂ NR heterojunctions exhibited outstanding visible-light photocatalytic activities and sustained cycling performance. Under visible-light irradiation for 120 min, the reduction efficiency of Cr(VI) over the TB-2 sample (molar ratio: n(Ti)/n(Bi) = 2:1) is as high as 95.4% without adding any scavengers. Furthermore, the sample also shows excellent photodegradation activity of RhB with a much higher apparent rate constant of 0.49 min^-1 and 88.5% total organic carbon removal ratio. Furthermore, the corresponding mechanism of enhanced photocatalytic activity is proposed according to comprehensively investigated results from photoluminescence spectroscopy, photoelectrochemical measurement analysis, and radical trapping experiments. This study provides an attractive avenue to design and fabricate highly efficient 1D NR heterojunction photocatalysts, which possessed a high application value in the field of environmental remediation, especially for wastewater purification.

A ball-in-ball g-C3N4@SiO2 nano-photoreactor for highly efficient H2 generation and NO removal

The design and construction of a nano-photoreactor with some complexity and elaborate functionalities is a novel and fascinating protocol to highly optimize the performances of a g-C₃N₄ photocatalyst. Herein, a ball-in-ball structured g-C₃N₄@SiO₂ composite nano-photoreactor was synthesized via a nanocasting technique combined with a partial etching technique, which showed diverse application potential in environmental protection and photocatalytic hydrogen evolution. As expected, the as-prepared nano-photoreactor exhibits a superior photocatalytic activity and excellent stability with respect to the above-mentioned aspects, and this enhanced performance could be attributed to its unique structural advantages of multiple scattering and reflecting effects, higher degree of crystallinity, and increased active surface area and porosity. More importantly, the nano-photoreactor provides a decent environment within nanoscale domains for catalytic reaction to greatly accelerate the conversion of reactants.

Increased photocatalytic activity of NiO and ZnO in photodegradation of a model drug aqueous solution: Effect of coupling, supporting, particles size and calcination temperature

Mechanically ball-mill prepared clinoptilolite nanoparticles (NC) were used for increasing photocatalytic activity of NiO and ZnO as alone and binary systems. The semiconductors were supported onto the zeolite during calcination of Ni(II)-Zn(II)-exchanged NC at different calcinations temperatures. XRD, FTIR, SEM-EDX, X-ray mapping, DRS, TEM and BET techniques were used for characterization of the samples. The calcined catalysts at 400°C for 4h showed the best photocatalytic activity for metronidazole (MNZ) in aqueous solution. The mole ratio of ZnO/NiO affected the photodegradation efficiency because activity of the coupled catalysts depends to the both e/h production and electron scavenging processes. In the used system, NiO acted as e/h production source and ZnO as an electron sink. Red shifts in band gaps of the supported coupled semiconductors was observed whit respect to monocomponent one, confirming formation of nanoparticles of the semiconductors onto the zeolitic bed. The best activities were obtained for the NiO_1.3-ZnO_1.5/NC (NZ-NC) and NiO_0.7-ZnO_4.3/NC (NZ₃-NC) catalysts at pH 3, 1.2gL^-1 of the catalysts and 1gL^-1 of MNZ.

Novel heterostructured InN/TiO2 submicron fibers designed for high performance visible-light-driven photocatalysis

InN phase was successfully integrated into TiO₂ fiber, which greatly improved its visible-light photocatalytic property.

Construction of a ternary hybrid of CdS nanoparticles loaded on mesoporous-TiO2/RGO for the enhancement of photocatalytic activity

An as-prepared ternary meso-TiO₂/RGO/CdS catalyst to photodegrade MO exhibited enhanced photocatalytic activity under the irradiation of simulated solar light.