High-performance Photocatalytic System Research Articles

Bioinspired Material for High-Performance Photocatalytic Systems

Bioinspired Material for High-Performance Photocatalytic Systems

Directed Electron Delivery from a Pb-Free Halide Perovskite to a Co(II) Molecular Catalyst Boosts CO2 Photoreduction Coupled with Water Oxidation.

The development of high-performance photocatalytic systems for CO2 reduction is appealing to address energy and environmental issues, while it is challenging to avoid using toxic metals and organic sacrificial reagents. We here immobilize a family of cobalt phthalocyanine catalysts on Pb-free halide perovskite Cs2AgBiBr6 nanosheets with delicate control on the anchors of the cobalt catalysts. Among them, the molecular hybrid photocatalyst assembled by carboxyl anchors achieves the optimal performance with an electron consumption rate of 300±13 μmol g-1 h-1 for visible-light-driven CO2-to-CO conversion coupled with water oxidation to O2, over 8 times of the unmodified Cs2AgBiBr6 (36±8 μmol g-1 h-1), also far surpassing the documented systems (<150 μmol g-1 h-1). Besides the improved intrinsic activity, electrochemical, computational, ex-/in situ X-ray photoelectron and X-ray absorption spectroscopic results indicate that the electrons photogenerated at the Bi atoms of Cs2AgBiBr6 can be directionally transferred to the cobalt catalyst via the carboxyl anchors which strongly bind to the Bi atoms, substantially facilitating the interfacial electron transfer kinetics and thereby the photocatalysis.

Enhancing CO2 photoreduction via the perfluorination of Co(II) phthalocyanine catalysts in a noble-metal-free system

The manufacture of high-performance photocatalytic systems based on earth-abundant elements remains a key challenge, urging operative strategies for catalyst design. Herein, we present the construction of an efficient and noble-metal-free molecular system for the photoreduction of CO2 to CO using a Cu(I) photosensitizer and Co(II) phthalocyanine catalysts. It was found that the perfluorination of Co(II) phthalocyanine shows enhanced catalytic performance for CO2-to-CO conversion compared with pristine Co(II) phthalocyanines, achieving a remarkable apparent quantum yield of 58.2% at 425 nm, which is three times that of the pristine one (19.0%). The Cu(I)/Co(II) system also achieved a maximum turnover number of 9185 and near-unity selectivity. These improvements can be attributed to the electron-withdrawing effect of the fluorine substituents, which lowers the catalytic overpotential for catalysis and decreases the Gibbs free energy of the rate-determining Co-carboxylate-forming step. This work indicates that perfluorination is an effective approach to optimize the catalytic performance of molecular catalysts.

One-Step Synthesis of Ag2O/Fe3O4 Magnetic Photocatalyst for Efficient Organic Pollutant Removal via Wide-Spectral-Response Photocatalysis-Fenton Coupling.

Photocatalysis holds great promise for addressing water pollution caused by organic dyes, and the development of Ag2O/Fe3O4 aims to overcome the challenges of slow degradation efficiency and difficult recovery of photocatalysts. In this study, we present a novel, environmentally friendly Ag2O/Fe3O4 magnetic nanocomposite synthesized via a simple coprecipitation method, which not only constructs a type II heterojunction but also successfully couples photocatalysis and Fenton reaction, enhancing the broad-spectrum response and efficiency. The Ag2O/Fe3O4 (10%) nanocomposite demonstrates exceptional degradation performance toward organic dyes, achieving 99.5% degradation of 10 mg/L methyl orange (MO) within 15 min under visible light irradiation and proving its wide applicability by efficiently degrading various dyes while maintaining high stability over multiple testing cycles. Magnetic testing further highlighted the ease of Ag2O/Fe3O4 (10%) recovery using magnetic force. This innovative approach offers a promising strategy for constructing high-performance photocatalytic systems for addressing water pollution caused by organic dyes.

Recent Progress of Single-Atom Photocatalysts Applied in Energy Conversion and Environmental Protection.

Photocatalysis driven by solar energy is a feasible strategy to alleviate energy crises and environmental problems. In recent years, significant progress has been made in developing advanced photocatalysts for efficient solar-to-chemical energy conversion. Single-atom catalysts have the advantages of highly dispersed active sites, maximum atomic utilization, unique coordination environment, and electronic structure, which have become a research hotspot in heterogeneous photocatalysis. This paper introduces the potential supports, preparation, and characterization methods of single-atom photocatalysts in detail. Subsequently, the fascinating effects of single-atom photocatalysts on three critical steps of photocatalysis (the absorption of incident light to produce electron-hole pairs, carrier separation and migration, and interface reactions) are analyzed. At the same time, the applications of single-atom photocatalysts in energy conversion and environmental protection (CO2 reduction, water splitting, N2 fixation, organic macromolecule reforming, air pollutant removal, and water pollutant degradation) are systematically summarized. Finally, the opportunities and challenges of single-atom catalysts in heterogeneous photocatalysis are discussed. It is hoped that this work can provide insights into the design, synthesis, and application of single-atom photocatalysts and promote the development of high-performance photocatalytic systems.

Photocatalytic degradation of organic pollutants in the presence of selected transition metal nanoparticles: review

Photocatalysis has attracted a lot of attention in recent years due to its potential in solving energy and environmental issues. Efficient light absorption and charge separation are two of the key factors for the exploration of high-performance photocatalytic systems, which are generally difficult to obtain from a single photocatalyst. The combination of various materials to form heterojunctions provides an effective way to better harvest solar energy and facilitate charge separation and transfer, thus enhancing photocatalytic activity and stability. This review concisely summarizes the recent development of visible light responsive heterojunctions, including the preparation and performance of semiconductor/semiconductor junctions and semiconductor/metal junctions and their mechanism for enhancing light harvesting and charge separation/transfer. In this regard, this review presents some unitary, binary and ternary CeO2 photocatalysts used for the degradation of organic pollutants. We expect this review to provide the type of guidelines for readers to gain a clear picture of nanotechnology and the fabrication and application of different types of heterostructured photocatalysts.

Realizing high-efficiency carrier separation in 3D hierarchical carbon nitride nanosheets via intramolecular donor-acceptor motifs strategy

The insufficient visible light responsive region and fast charge recombination probability are still the key obstacles for designing high-performance photocatalytic system. Herein, a “One Stone, Two Birds” strategy was reported in three-dimensional (3D) hierarchical graphitic carbon nitride (g-C3N4) nanosheet with intramolecular donor-acceptor (D-A) motifs (3D CN) photocatalyst, which solved two urgent problems simultaneously. The 3D hierarchical nanosheets structure endowed 3D CN with abundantly exposed reaction active sites and cross-plane diffusion channels. The formation of internal D-A system facilitated the light absorption and accelerated the transfer and separation of charge carriers. Furthermore, the introducing of D-A motifs optimized the bandgap of g-C3N4 and negative-shifted conduction band position. The as-prepared 3D CN showed excellent visible-light photocatalytic H2 performance, with H2 evolution rate of 2521.2 μmol h−1/g, which was six times higher than the pristine CN. This outstanding performance was ascribed to the synergistic effect of 3D hierarchical nanosheets structure and intramolecular D-A motifs. This current work provides a novel insight to design and construct of 3D hierarchical CN nanostructures with D-A motifs simultaneously, which can be further promising applications for clean and sustainable energy conversion.

Three-phase interface photocatalysis for the enhanced degradation and antibacterial property

Semiconductor photocatalysis, as a means of utilizing stranded renewable solar resources, is now emerging as a viable and promising approach for increasingly severe water pollution. In this work, a high-performance photocatalytic system has been fabricated by immobilizing spiky TiO2/Au nanohybrids on one side of hydrophobic nanoPE substrate (PE-TiO2/Au) that forces the enabling of air–liquid–solid triphase photocatalytic interface. Such a triphase system allows efficient oxygen access to the photocatalyst surface, which is feasible for charge separation and reactive oxygen species (ROS) production. Two modes of triphase systems with different gas flow paths were constructed, in which PE-TiO2/Au was floating on the aqueous solution surface (exposed mode) or immersing in aqueous phase (immersed mode). It is worth mentioning that the exposed PE-TiO2/Au enables a more efficient oxygen supply, thus leading to a 5.5-fold and 1.8-fold higher reaction kinetics as compared to normal liquid–solid diphase system and immersed PE-TiO2/Au. Meanwhile, PE-TiO2/Au also exerts bactericidal effect under visible light irradiation, which effectively inactivates S.aureus (>99.9%) in a lean period of 30 min. The qualities of high lethality rate and short reaction time are endowed to PE-TiO2/Au due to the co-effect of unique triphase interface microenvironment and elaborate heterojunction of spiky TiO2/Au nanohybrids. In this paper, we have revealed for the first time that the antibacterial efficiency can be effectively improved by increasing the oxygen supply with the construction of three-phase interface, which represents a promising option in designing highly efficient photocatalytic systems for sewage purification applications.

An Overview on the Photocatalytic Degradation of Organic Pollutants in the Presence of Cerium Oxide (CeO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;) Based Nanoparticles: A Review

Considerable efforts have been devoted to enhancing the photocatalytic activity and solar energy utilization of photocatalysts. Photocatalysis has attracted much attention in recent years due to its potential in solving energy and environmental issues. The fabrication of various materials (coupled or doped) to form heterojunctions provides an effective way to better harvest solar energy and to facilitate charge separation and transfer, thus enhancing the photocatalytic activity and stability. Efficient light absorption and charge separation are two of the key factors for the exploration of high performance photocatalytic systems, which is generally difficult to be obtained in a single photocatalyst. In this review, we briefly summarizes the recent development heterostructured semiconductors, including the preparation and performances of semiconductor/semiconductor junctions, semiconductor/metal junctions, and their mechanism in the area of environmental remediation and water splitting for enhanced light harvesting and charge separation/transfer, describe some of the progress and resulting achievements, and discuss the future prospects. The scope of this review covers a variety of type photocatalysts, focusing particularly on Ceria (CeO₂) heterostructured photocatalysts. We expect this review to provide a guideline for readers to gain a clear picture of fabrication and application of different type heterostructured photocatalysts.

Cadmium sulfide quantum dots/dodecahedral polyoxometalates/oxygen-doped mesoporous graphite carbon nitride with Z-scheme and Type-II as tandem heterojunctions for boosting visible-light-driven photocatalytic performance

It is known that fabrication of tandem heterojunctions between different types of heterojunctions can promote the charge separation. Herein, novel cadmium sulfide quantum dots (CdS QDs)/dodecahedral phosphotungstic acid potassium K3PW12O40 (KPW)/oxygen-doped mesoporous graphite carbon nitride (meso-g-C3N4) nanosheets tandem heterojunctions are prepared by the hydrothermal method combined with direct template calcination and in-situ chemical sedimentation strategy. The results show that tandem heterojunctions formed by the Z-Scheme heterojunction between CdS QDs and KPW and the type-II heterojunction between CdS QDs and meso-g-C3N4 can extend the optical response into visible light region. Importantly, under visible light irradiation, photocatalytic hydrogen production rate and photocatalytic Cr6+ removal rate over CdS/KPW/meso-g-C3N4 is higher than that of KPW and CdS/KPW. This remarkable photocatalytic performance is due to the effective charge separation and transfer of the special tandem heterojunction structure. This novel tandem heterojunction will offer new insights for fabricating other high-performance photocatalytic systems.

Wide spectral response photothermal catalysis-fenton coupling systems with 3D hierarchical Fe3O4/Ag/Bi2MoO6 ternary hetero-superstructural magnetic microspheres for efficient high-toxic organic pollutants removal

3D hierarchical Fe3O4/Ag/Bi2MoO6 magnetic microspheres are fabricated through hydrothermal-photoreduction strategy, which fabricate an advanced photocatalytic-Fenton coupling system. The H2O2 produced by photocatalysis could form the photo-Fenton system when combined with Fe3O4 under light illumination. The introduction of Ag nanoparticles could induce the localized surface plasmon resonance (LSPR), which provides “hot electrons” for promoting photocatalysis. The addition of Fe3O4 achieve the successful coupling of photocatalysis-Fenton, and enhanced the broad spectrum response of the final composite sample. The 3D hierarchical Fe3O4/Ag/Bi2MoO6 exhibit excellent UV–Vis-NIR-driven photocatalytic performance for mineralization of high-toxic Aatrex and Bisphenol A. The addition of magnetic Fe3O4 is conducive to the magnetic separation, which favors practical application. The strategy provides thought-provoking insights for constructing new types of high-performance photocatalytic system.

Design and engineering of high-performance photocatalytic systems based on metal oxide–graphene–noble metal nanocomposites

Coupling metal oxide photocatalysts with functional nanomaterials such as noble metal- and molecular graphene-based nanostructures and engineering their structural and optoelectronic properties can lead to high-performance photocatalytic systems.

Improving removal of 4-chlorophenol using a TiO2 photocatalytic system with microwave and ultraviolet radiation

A conventional photocatalytic system is a viable tool to purify wastewaters, whereas poor degradation performance due to diverse pollutants under various conditions still leaves it behind commercial markets. This study aimed to determine the degradation efficiency and mechanism of 4-chlorophenol in a hybrid system integrating a series of unit processes such as a conventional TiO2 photocatalytic reactor as well as microwave and ultraviolet (UV) radiation. The decomposition (rate) of 4-chlorophenol was assessed with respect to the microwave intensity, pH, circulating fluid velocity, hydrogen peroxide level, and oxygen gas injection, along with a mix of individual processes. Results showed that there were favorable conditions for improving the degradation performance within certain limits. However, a significant synergy effect was also observed in the combined processes, which was substantially larger than any single process. Out of them, the best degradation performance was achieved using microwave irradiation and hydrogen peroxide in the photocatalytic reactor. The four intermediates (i.e., benzoquinone, hydroquinone, 4-chlorocatechol, and hydroxyhydroquinone) appeared to be generated through hydroxyl radicals-mediated hydroxylation and dechlorination in the proposed photocatalytic pathway. The present research is expected to provide new insights into designing the high performance photocatalytic system with affordable cost.

Recent Progress on Visible Light Responsive Heterojunctions for Photocatalytic Applications

Photocatalysis has attracted much attention in recent years due to its potential in solving energy and environmental issues. Even though numerous achievements have been made, the photocatalytic systems developed to date are still far from practical applications due to the low efficiency and poor durability. Efficient light absorption and charge separation are two of the key factors for the exploration of high performance photocatalytic systems, which is generally difficult to be obtained in a single photocatalyst. The combination of various materials to form heterojunctions provides an effective way to better harvest solar energy and to facilitate charge separation and transfer, thus enhancing the photocatalytic activity and stability. This review concisely summarizes the recent development of visible light responsive heterojunctions, including the preparation and performances of semiconductor/semiconductor junctions, semiconductor/cocatalyst junctions, semiconductor/metal junctions, semiconductor/non-metal junctions, and surface heterojunctions, and their mechanism for enhanced light harvesting and charge separation/transfer.

Enhancement of Photo-Oxidation Activities Depending on Structural Distortion of Fe-Doped TiO2 Nanoparticles.

To design a high-performance photocatalytic system with TiO2, it is necessary to reduce the bandgap and enhance the absorption efficiency. The reduction of the bandgap to the visible range was investigated with reference to the surface distortion of anatase TiO2 nanoparticles induced by varying Fe doping concentrations. Fe-doped TiO2 nanoparticles (Fe@TiO2) were synthesized by a hydrothermal method and analyzed by various surface analysis techniques such as transmission electron microscopy, Raman spectroscopy, X-ray diffraction, scanning transmission X-ray microscopy, and high-resolution photoemission spectroscopy. We observed that Fe doping over 5 wt.% gave rise to a distorted structure, i.e., Fe2Ti3O9, indicating numerous Ti3+ and oxygen-vacancy sites. The Ti3+ sites act as electron trap sites to deliver the electron to O2 as well as introduce the dopant level inside the bandgap, resulting in a significant increase in the photocatalytic oxidation reaction of thiol (–SH) of 2-aminothiophenol to sulfonic acid (–SO3H) under ultraviolet and visible light illumination.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1263-6) contains supplementary material, which is available to authorized users.