Field Of Photocatalysis Research Articles

Efficient C(sp3)-H Bond Oxidation on Perovskite Quantum Dots Based on Ce-Oxygen Affinity.

Perovskite quantum dots (QDs) have shown attractive prospects in the field of visible photocatalysis, especially in the synthesis of high value-added chemicals. However, under aerobic conditions, the stable operation of QD catalysts has been limited by the reactive oxygen species (ROS) generated by photoexcitation, especially superoxide species O2⋅-. Here, we propose a strategy of Ce3+ doping in perovskite QDs to guide superoxide species for photocatalytic oxidation reactions. In C(sp3)-H bond oxidation of hydrocarbons, superoxide species were rapidly generated and efficiently utilized on the surface of perovskite QDs, which achieves the stable operation of the catalytic system and obtains a high product conversion rate (15.3 mmol/g/h for benzaldehydes). The mechanism studies show that the strong Ce-oxygen affinity accelerates the relaxation process of photoinduced exciton transfer to superoxide species and inhibits the radiative recombination pathway. This work provides a new idea of utilizing oxygen species on perovskite surface and broadens the design strategy of high-performance QD photocatalysts.

Efficient C(sp3)−H Bond Oxidation on Perovskite Quantum Dots Based on Ce‐Oxygen Affinity

AbstractPerovskite quantum dots (QDs) have shown attractive prospects in the field of visible photocatalysis, especially in the synthesis of high value‐added chemicals. However, under aerobic conditions, the stable operation of QD catalysts has been limited by the reactive oxygen species (ROS) generated by photoexcitation, especially superoxide species O2⋅−. Here, we propose a strategy of Ce3+ doping in perovskite QDs to guide superoxide species for photocatalytic oxidation reactions. In C(sp3)−H bond oxidation of hydrocarbons, superoxide species were rapidly generated and efficiently utilized on the surface of perovskite QDs, which achieves the stable operation of the catalytic system and obtains a high product conversion rate (15.3 mmol/g/h for benzaldehydes). The mechanism studies show that the strong Ce‐oxygen affinity accelerates the relaxation process of photoinduced exciton transfer to superoxide species and inhibits the radiative recombination pathway. This work provides a new idea of utilizing oxygen species on perovskite surface and broadens the design strategy of high‐performance QD photocatalysts.

Lattice Distortion Induced Ta‐doped BaTiO3 for Efficient Photocatalytic Water Splitting for Hydrogen Production

AbstractBaTiO3, as a perovskite type material with excellent chemical stability and suitable conduction, has been widely studied in the field of photocatalysis. However, it can only absorb ultraviolet light because of its wide band gap. Herein, the lifetime of photogenerated electrons of BaTiO3 doped with Ta5+ can be enhanced. To study the band structure and photocatalytic performance of Ta‐doped BaTiO3, sol‐gel assisted solid‐phase method was employed to prepare BaTiO3 doped with varying Ta5+ doping amounts, and the structure characteristic and formation mechanism of the Ta‐doped BaTiO3 were analyzed. The results showed that the heat treatment temperature reached 1052.7 °C, sufficient thermodynamic conditions were obtained for Ta5+ to dope into the BaTiO3 lattice, and lattice distortion occurred in BaTiO3. Meanwhile, the particle size after doping decreased with the increase of Ta5+ doping amount. The 1.25 mol %Ta5+‐doped BaTiO3 had the lowest band gap (3.077 eV), and the photocatalytic water splitting had the best hydrogen evolution activity, which was 2.4 times that of BaTiO3. Furthermore, the conductance potential of 1.25 mol %Ta5+‐doped BaTiO3 was more negative than that of BaTiO3, which improved the thermodynamic advantage of the photocatalytic water splitting, and it had higher and more stable photoresponse and photogenerated carrier migration rate.

Enhanced photocatalytic oxidation of 5-hydroxymethylfurfural using a green bimetallic sulfide catalyst ZnxCd(1-x)S

A novel bimetallic sulfide catalyst, ZnxCd(1-x)S, synthesized via a one-step hydrothermal process, has demonstrated exceptional efficiency in the efficient oxidation of 5-hydroxymethylfurfural (HMF) to 2, 5-dimethylacylfuran (DFF). This transformation is achieved under environmentally benign conditions: without any external oxidant at room temperature and atmospheric pressure, with water as the solvent and visible light. The unique 3D flower-like nanosphere structure of Zn0.4Cd0.6S, characterized by a synergistic composition of ZnS and CdS, facilitates the simultaneous photocatalytic oxidation of water and HMF. The synergistic action of superoxide (∙O2-) and single-linear state oxygen (1O2) served as the main active radicals generated in situ from water photolysis. Remarkably, Zn0.4Cd0.6S exhibited an excellent performance, achieving a remarkable product yield over 50 % and 75 % selectivity after only 3 h. This work presents a sustainable approach to the valorization of HMF and advances the field of photocatalysis without reliance on additional oxidants.

Facile Construction of a Double-Heterojunction Perovskite Quantum Dot System for Efficient Photocatalytic Cr6+ Reduction.

Based on their excellent stability, high carrier mobility, and wide photoresponse range, composites formed by embedding perovskite quantum dots (PQDs) into metal-organic frameworks (PQDs@MOF) show great development potential in the field of photocatalysis, including the toxic hexavalent chromium (Cr6+) degradation, CO2 reduction, H2 production, etc. However, the rapid recombination of photogenerated carriers is still a major obstacle to the improvement of photocatalytic performance, and the internal mechanism of photocatalysis is still unclear. In this work, we construct a novel double heterojunction photocatalyst by encapsulating CsPbBr3 PQDs in Zr-based metal-organic frameworks (UiO-67) and loading additional hole-acceptor pentylenetetrazol (PTZ). Spontaneous photoinduced charge-transfer and separation between interfaces are confirmed by time-resolved photoluminescence and transient absorption spectroscopy. Furthermore, compared with pure UiO-67, the photoactivity of CsPbBr3 PQDs@UiO-67@PTZ increased 3-fold due to the long-lived charge-separated state. Our findings provide a new guideline for the design of PQDs@MOF-based photocatalysts with long-lived photogenerated carriers and outstanding photocatalytic activity.

Accessible New Non-Quantum Dot Cs2PbI2Cl2-Based Photocatalysts for Efficient Hole-Driven Photocatalytic Applications.

Efficient, low-cost photocatalysts with mild synthesis conditions and stable photocatalytic behavior have always been the focus in the field of photocatalysis. This study proves that non-quantum-dot Cs2PbI2Cl2-based materials, created by a simple method, can be successfully employed as new high-efficient photocatalysts. The results demonstrate that two-dimensional Cs2PbI2Cl2 perovskite can achieve over three times higher photocatalytic performance compared to three-dimensional CsPbBr3 perovskite. Moreover, the photocatalytic performance of Cs2PbI2Cl2 can be further improved by constructing a heterojunction structure, such as Cs2PbI2Cl2/CsPbBr3. Cs2PbI2Cl2 can connect well with CsPbBr3 through a simple method, resulting in tight bonding at the interface and efficient carrier transfer. Cs2PbI2Cl2/CsPbBr3 exhibits notable 5-fold and 10-fold improvements in photocatalytic performance and rate compared to CsPbBr3. Additionally, Cs2PbI2Cl2/CsPbBr3 demonstrates superb stable catalytic performance, with nearly no decrease in photocatalytic performance after 7 months (RH = 20% ± 10, T = 25 °C ± 5). This study also reveals that the photocatalytic process based on Cs2PbI2Cl2/CsPbBr3 can directly oxidize organic matter using holes, without relying on the generation of intermediate reactive oxygen species from water or oxygen (such as ·OH or ·O2-), showcasing further potential for achieving high photocatalytic efficiency and selectivity in anhydrous/anaerobic catalytic reactions and treating recalcitrant pollutants.

Plasmonic Hot Carrier‐Driven Photoelectrochemical Processes: Principle, Detection and Application

AbstractUtilizing hot carriers induced by surface plasmon resonance in solar energy conversion to chemical fuels is a crucial issue in the field of photocatalysis. To achieve practical efficiency in plasmonic hot carrier application to photocatalysts, it is essential to theoretically and experimentally understand the generation, relaxation, and transfer of hot carriers. Photoelectrochemical (PEC) processes can offer a pathway to investigate the transfer dynamics of hot electrons (or hot holes) and enhance the efficiency of both hot carrier transfer and catalytic activity. This work summarizes a theoretical and experimental understanding of the hot carrier effect, emphasizing the hot carrier transfer dynamics to investigate the exact role of hot carriers in PEC reactions. The principles of hot carrier detection, diverse applications of hot carrier‐based photocatalysis, and perspectives for possible future progress are discussed.

Exploring the in‐situ Development of A 1 D/2 D Gadolinium Iron Oxide/Tungsten Disulfide Photocatalyst to Improve Tetracycline Degradation Mediated by Visible Light

AbstractIn the field of photocatalysis, heterojunction photocatalysts have garnered a lot of attention due to their high‐efficiency interfacial charge‐transfer property and their nanoarchitecture. Herein, GdFeO3/WS2 is successfully synthesized by the in‐situ growth method and holds significant catalytic properties and efficient degradation for tetracycline. Using WS2 as a co‐catalyst could reduce e‐ and h+ recombination, improving GdFeO3’s photocatalytic performance. The GdFeO3/WS2 possesses a bandgap of 1.9 eV, 178.9 m2 g−1 specific surface area, 0.2 nm pore size, and a lifespan of 6 ns. The optimal GdFeO3/WS2 photocatalyst exhibits a maximum removal of 96.2 % at a tetracycline concentration of 10 mg/L, a pH of 3, and 40 mg of photocatalyst in an irradiation time of 90 min. Tetracycline has a higher photocatalytic efficiency in visible light (96.2 %) than in sunlight (72.6 %). Trapping tests revealed that the major reactive species for tetracycline removal in an aqueous solution are ⋅⋅OH, and ⋅⋅O2‐. The recycle experiment shows no deactivation of the GdFeO3/WS2 photocatalyst after 5 recycles. This study sheds light on the rational design of the GdFeO3/WS2 photocatalyst as a potential material for treating wastewater.

Rare earth-doped carbon nitride composite Ce-based metal-organic framework for visible light-driven nitrogen fixation catalysis

The utilization of visible light for photocatalytic nitrogen fixation offers a sustainable and eco-friendly strategy for the production of ammonia. The present study focuses on the synthesis of a series of rare earth-doped carbon nitride composite ultraviolet-activated Ce-UiO-66 catalysts, denoted as RECN-actMOF, for efficient nitrogen fixation. Rare earth doping modulates the band structure of carbon nitride, facilitating the formation of a type-I heterojunction with Ce-UiO-66 and promoting photocarrier generation at nitrogen fixation sites. Among these, Sm-doped SmCN-actMOF exhibits high visible-light absorption and efficient utilization of photocarriers, resulting in an apparent quantum efficiency (AQE) of 1.58% under 495 nm light irradiation. This study provides a pathway for enhancing the nitrogen fixation efficiency of photocatalysts through the incorporation of rare earth elements, and expanding the potential applications of rare earth materials in the field of photocatalysis.

In situ fabrication of 2D Ti3C2/1T&2H-MoS2/TiO2 photocatalyst for sulfamethazine degradation

Sunlight-driven photocatalysis is a very appealing approach for solving the current energy crisis because it will not cause secondary pollution. Titanium dioxide (TiO2) has attracted much attention in the field of photocatalysis due to its simple preparation, environmental friendliness and easy modification. However, reducing the band gap and expanding the light absorption range to reduce the carrier recombination rate of TiO2 is still a huge challenge. Herein, we report a two-dimensional (2D) Ti3C2/1 T&2 H-MoS2/TiO2 photocatalyst obtained by in situ growth of a 1 T&2 H-MoS2/TiO2 Z-scheme heterojunction on a highly conductive Ti3C2 MXene surface. The spectral response range of the resulting Ti3C2/1 T&2 H-MoS2/TiO2 (Ti3C2:1 T&2 H-MoS2:TiO2= 1:10:10) photocatalyst was broadened to 696 nm and the band gap was reduced to 1.83 eV, which was responsible for the strong light-harvesting capacity and improved charge separation. The activity of the Ti3C2/1 T&2 H-MoS2/TiO2 photocatalyst was evaluated by photocatalytic degradation of sulfamethazine (SMZ). The degradation rate of SMZ reached 99.8 % after 90 min of illumination. These results demonstrate that the combination of Ti3C2 MXene and heterojunction is a feasible strategy to enhance the light-harvesting capacity and charge transport in photocatalytic reaction.

CsPbBr3/TiO2 Z-type heterojunction for rhodamine B catalysis and efficient photodetectors

Halide perovskites have attracted widespread attention in the fields of photovoltaics, LEDs, lasers, and photocatalysis due to their unique optoelectronic properties. Here, we proposed a method to synthesize CsPbBr3/TiO2 composite material by embedding precursors into mesoporous titanium dioxide pores and inducing in-situ growth of the perovskites within the pores. Due to the encapsulation of mesoporous TiO2, CsPbBr3 maintains its excellent luminescent characteristics in water, air, and at high temperatures. Furthermore, the Z-type heterojunction structure formed between mesoporous TiO2 and internal CsPbBr3 significantly enhances the photo-generated current, and the response time has increased by 1.7 times.

Performance and mechanic insights into potassium-oxygen co-doping graphic carbon nitride for UV photocatalytic oxidation of carbamazepine

Graphitic carbon nitride (g-C3N4) has good prospect in the field of photocatalysis, but its small specific surface area and low photogenerated carrier separation efficiency limit the large-scale application in photocatalytic wastewater treatment. In this study, the one-step thermal polymerization method was employed to synthesize potassium and oxygen co-doped g-C3N4 (OCN-3), which was used in photocatalytic degradation of carbamazepine (CBZ). Compared with the original g-C3N4, the pseudo first-order kinetic constant of CBZ degradation by OCN-3 was increased from 0.00820 min−1 to 0.17529 min−1 under UV irradiation. The results of competitive oxidation kinetics experiment demonstrated that ·OH played a main role in CBZ degradation. The photoelectric experiments and calculation based on density functional theory revealed that potassium and oxygen atoms can not only regulate the local electron density, but also reduce the band gap width and promote electron transfer as well as photogenerated carrier separation. Furthermore, OCN-3 was loaded on carbon cloth to prepare supported photocatalyst, which can be conveniently applied in continuous wastewater treatment reactor, and the results shows that the degradation efficiency of CBZ remains over 90% within 600 min continuous operation when the hydraulic retention time was 1.25 h.

Preparation and piezoelectric assisted photocatalytic degradation of BaTiO3/SrTiO3 nanocomposites

Piezoelectric materials capable of generating an inherent electric field under strain, exhibit promising applications in in-situ piezocatalysis and enhanced photocatalytic activities. SrTiO3 (STO) is a photocatalytic material, but it faces challenges such as low efficiency in photogenerated carrier separation and transfer, as well as limited reduction and oxidation reactions. To address these issues, this study utilized the piezoelectric properties of tetragonal BaTiO3 (BTO) nanoparticles and the photocatalytic properties of STO to prepare BaTiO3/SrTiO3 composite materials for piezoelectric assisted photocatalytic degradation of dyes. Disperse BTO nanoparticles with different mass ratios in STO spinning solution to produce a suspension, which is electrospun to form BTO-STO-1:x. The optimal degradation performance and catalytic activity of BTO-STO-1:x were determined through testing to identify the best composite material. It provides a robust foundation for underpinning the coupling mechanism between the enhancement of piezoelectricity and photocatalytic effect, offering an efficient pathway for advancing the field of piezoelectric assisted photocatalysis.

Metal-Free C60-Doped Mesoporous Carbon Nitride Drives Red-Light Photocatalysis.

The pursuit of novel strategies for synthesizing high-performance nanostructures of graphitic carbon nitride (g-C3N4) has garnered increasing scholarly attention in the field of photocatalysis. Herein, we have successfully designed a metal-free photocatalyst by integrating mesoporous carbon nitride (mpg-C3N4) and C60 through a straightforward and innovative method, marking the first instance of such an achievement. Under red light, the C60/mpg-C3N4 composite exhibited a significantly accelerated rhodamine B (RhB) photodecomposition rate, surpassing bulk g-C3N4 by more than 25.8 times and outperforming pure mpg-C3N4 by 7.8 times. The synergistic effect of C60 and the mesoporous structure significantly enhanced the photocatalytic performance of g-C3N4 by adjusting its electronic structure, broadening the light absorption range, increasing the active sites, and reducing the recombination of photogenerated carriers. This work presents a promising avenue for harnessing a metal-free, stable, efficient photocatalyst driven by red light, with potential for enhancing solar energy utilization in environmental remediation.

Kinetic analysis of TiO2-based photocatalysts sensitized with chlorophyll-derived dimers for light-driven hydrogen evolution

This study focuses on the kinetic analysis of chlorophyll-based dimer photosensitizers adsorbed on Pt/TiO2 photocatalyst for light-driven hydrogen evolution. To elucidate the detailed mechanism, four photosensitizers, a carboxylated chlorin (Chl) and its dimer derivatives connecting an accessory pigment of chlorin (Chl-PPa), porphyrin (Chl-Por), and bacteriochlorin (Chl-BPPa) were synthesized and their kinetic processes in photocatalytic hydrogen evolution were investigated. The results indicate that Chl-PPa possesses the highest ability to produce photogenerated carriers, with an appropriate excited state lifetime, lowest propensity for charge recombination, and longest charge transfer lifetime. These favorable characteristics contribute to its exceptional photocatalytic activity compared with other photosensitizers. Specifically, the Chl-PPa-sensitized Pt/TiO2 photocatalyst exhibits a remarkable hydrogen generation rate of 5.36 mmol/g/h. Moreover, these photosensitizers demonstrate excellent stability and multiple-experimental consistency. This study provides significant insights into the development of dyad photosensitizers and highlights their practical significance in the field of photocatalysis. By harnessing chlorophyll, we have successfully harnessed efficient and controlled hydrogen fuel generation through photocatalytic water splitting, thus paving the way for future advancements in clean and sustainable energy production.

Phenyl-bridged N,N,N'N'-Tetrasubstituted bis(2-amino-5-thiazolyl) diamine: Synthesis and applications in electrochromism and photocatalytic nitrobenzene reduction

A novel type of triphenylamine derivatives, phenyl-bridged N,N,N′,N′-tetrasubstituted bis(2-amino-5-thiazolyl) diamine (4) and its cationic form (5) were synthesized via the Hantzsch reaction. The UV–Vis spectroscopy, cyclic voltammetry (CV) and density functional theory (DFT) calculation results showed that the diamine possesses excellent redox properties and a narrow optical energy gap (∼1.85 eV). As an electrochromic material, compound 4 exhibits a notable color change from colorless to blue. It maintains stable cycling performance for up to 175 cycles, even within a higher voltage range of −2.4 to 2.4 V. In addition, as a catalyst, compound 5 exhibits good substrate compatibility and an aniline conversion rate of up to 89 % during the photocatalytic reduction of nitrobenzene. These results would contribute to understand the synthesis of triphenylamine electrochromic materials and expand their applications in the field of photocatalysis.

CNT/TiO2 nanocomposite for environmental remediation

Abstract Nanomaterials and their composites have been proven to be effective materials for various energy and environmental applications. In this way, functionalized polymers and their nanocomposites (NCs) are receiving much attention due to their tunable physico-chemical characteristics, cost and ease of availability. As an environmental application, particularly the removal of toxic dyes, photocatalysis has been reported as an emerging technology. The literature survey shows that functionalized polymer nanocomposites (PNCs) as photocatalysts offer an extensive contribution towards the generation of clean, renewable, and practical forms of energy from light-based pollutant removal as environmental remediation. Here, the present concept provides a brief introduction to the field of photocatalysis and environmental remediation, followed by the application of functionalized PNCs. In this view, TiO2–NCs are reported to be effective photocatalytic materials. In the present study, CNT-doped TiO2 NCs samples have been prepared using the sol–gel method and their photocatalytic activity has been investigated through a dye degradation experiment. Compared to the present studies, here the CNT content taken is very low, and it is found to be effective for the dye degradation part of an environmental cleaning application.

In Situ Growth of CuBi2O4/Bi2O3 Z-Scheme Heterostructures for Bifunctional Photocatalytic Applications.

In this study, we present an in situ solvothermal approach for synthesizing a highly efficient bifunctional CuBi2O4/Bi2O3 composite catalyst for applications in H2 production and the removal of organic pollutants. Various characterization techniques, including XRD, UV-vis DRS, SEM, TEM, and EIS, were used to characterize the prepared catalyst. Density functional theory calculations confirmed a Z-scheme mechanism, revealing the charge transfer mechanism from the Bi2O3 surface to the CuBi2O4 surface. The composite exhibited a photocurrent of 2.83 × 104 A/cm2 and a hydrogen production rate of 526 μmolg-1h-1 under natural sunlight. Moreover, the catalyst demonstrated efficient degradation of RhB up to 58% in 120 min under 50 W LED illumination. Additionally, multiple recycling tests confirmed its high stability and recyclability, making it a promising candidate for various applications in the field of photocatalysis.

Designed Nanoarchitectures of a BiOBr/BiOI Nanosheet Heterojunction Anchored on Dendritic Fibrous Nanosilica as Visible-Light Responsive Photocatalysts.

Heterojunctions, particularly those involving BiOBr/BiOI, have attracted significant attention in the field of photocatalysis due to their remarkable properties. In this study, a unique architecture of BiOBr/BiOI was designed to facilitate the rapid transfer of electrons and holes, effectively mitigating the recombination of electron-hole pairs. Accordingly, the BiOBr/BiOI nanosheet heterojunction was anchored on dendritic fibrous nanosilica (DFNS) by the immobilization of Bi2O3 nanodots in DFNS and the subsequent reaction with HBr and then HI vapors at room temperature. The 4 nm-Bi2O3 nanodots acted as a sacrificial template to form BiOX nanosheets by reaction with HX vapors (X = Br, I). The BiOBr/BiOI nanosheet heterojunction with the lateral size remained in the range of 90 to 110 nm and a thickness of 15 nm formed on DFNS, where the BiOBr:BiOI ratio in the product was controlled by the exposure time to HX vapors. The reaction sequence (HBr → HI vapors) was a key for the formation of BiOBr/BiOI nanosheet heterojunction with controlled composition. When the reaction of Bi2O3 nanodots with HI vapor was performed in the reverse sequence (HI→ HBr), the substitution of I- with Br- occurred to form BiOBr sheets on DFNS. The BiOBr/BiOI nanosheet heterojunction anchored on DFNS was used as a visible-light-driven photocatalyst for the decomposition of benzene in water under solar light, and its activity was superior to that of single BiOX nanosheets on DFNS.

Triazine and Fused Thiophene-Based Donor-Acceptor Type Semiconducting Conjugated Polymer for Enhanced Visible-Light-Induced H2 Production.

Conjugated polymers have attracted significant attention in the field of photocatalysis due to their exceptional properties, including versatile optimization, cost-effectiveness, and structure stability. Herein, two conjugated porous polymers, PhIN-CPP and ThIN-CPP, based on triazines, were meticulously designed and successfully synthesized using benzene and thiophene as building blocks. Based on UV diffuse reflection spectra, the photonic band gaps of PhIN-CPP and ThIN-CPP were calculated as 2.05 eV and 1.79 eV. The PhIN-CPP exhibited a high hydrogen evolution rate (HER) of 5359.92 μmol·g-1·h-1, which is 10 times higher than that of Thin-CPP (538.49 μmol·g-1·h-1). The remarkable disparity in the photocatalytic performance can be primarily ascribed to alterations in the band structure of the polymers, which includes its more stable benzene units, fluffier structure, larger specific surface area, most pronounced absorption occurring in the visible region and highly extended conjugation with a high density of electrons. The ΔEST values for PhIN-CPP and ThIN-CPP were calculated as 0.79 eV and 0.80 eV, respectively, based on DFT and TD-DFT calculations, which revealed that the incorporation of triazine units in the as-prepared CMPs could enhance the charge transfer via S1 ↔ T1 and was beneficial to the photocatalytic decomposition of H2O. This study presents a novel concept for developing a hybrid system for preparation of H2 by photocatalysis with effectiveness, sustainability, and economy.