High-performance Photocatalysts Research Articles

Defective h-BNs-Supported Pd Nanoclusters: An Efficient Photocatalyst for Selective Oxidation of 5-Hydroxymethylfurfural.

5-hydroxymethylfurfural (HMF) is one of the most promising biomass-based chemicals that is used to produce many kinds of important compounds. Especially, the selective conversion of HMF to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), an important chemical feedstock, has high industrial significance but is technically challenging. In this study, we present a high-performance photocatalyst for selective oxidation of HMF to HMFCA. By integrating an ultrasmall amount of palladium (Pd) nanoclusters (1.12‰ in weight) on defective hexagonal boron nitride nanosheets (Pd/defective h-BN nanosheets (dh-BNs)), outstanding photocatalytic performance can be achieved, resulting in up to a 95% HMF conversion ratio with an 82% HMFCA selectivity. The performance is considerably higher than that of pristine dh-BNs and Pd on defect-free h-BNs. More importantly, this Pd/dh-BNs catalyst maintains a high catalytic activity after eight cycles, demonstrating robust catalytic stability. Density functional theory calculations indicate that Pd/dh-BNs can lower the energy barrier for HMF oxidation and facilitate the desorption of HMFCA, which contributes to the high selectivity catalytic performance. This study not only introduces a promising photocatalyst for sustainable chemical transformations but can also provide valuable insights into the design of advanced photocatalytic material for biorefinery applications.

Green Synthesis of Silver-Incorporated Rutile TiO2 for Enhanced Photocatalytic Degradation of Ciprofloxacin and Carmine G Dye Pollutants

Developing sustainable TiO2-based photocatalysts for environmental remediation is an increasingly significant area of research. However, a limited understanding of the long-term ecological impact of these photocatalysts poses a barrier to their practical and industrial-scale applications. To address this challenge, this work employed a green synthesis approach to prepare an Ag/TiO2 photocatalyst designed to improve environmental compatibility and enhance efficiency in pollutant degradation. Ag/TiO2 was synthesized using mushroom biomass as a natural capping to evaluate its effectiveness in the degradation of ciprofloxacin (CIP) and azo Carmine G dye (ACGD). The mushroom biomass served as a renewable cost-effective support for Ag incorporation, while the Ag modification of TiO2 could enhance the photocatalyst’s performance. Structural, chemical, and morphological characterization techniques were applied and showed that the Ag/TiO2 particles consisted of irregularly shaped nanoparticles. The CIP removal reached 82.46% after 300 min and ACGD removal efficiency went up to 83.64%. The enhanced performance is attributed to the unique electronic and structural properties of Ag-modified TiO2. This study highlights the potential of Ag/TiO2 synthesized via green methods as a high-performance photocatalyst for the effective remediation of pharmaceutical and dye pollutants in wastewater treatment applications.

Fine-tune the structural components of porous frameworks for photocatalytic hydrogen production.

With the depletion of fossil fuels and increasing pollution problems, green and sustainable energy supply attracts worldwide attention. Hydrogen is a green and high-density energy substance, and photocatalytic hydrogen generation is an effective and sustainable method.Therefore, developing high-performance photocatalysts plays a crucial role in practical application. Porous frameworks with large surface areas and diversified structures are considered promising candidates for photocatalysts. This review summarizes the recent progress on porous frameworks and their derivatives through fine-tuning structural components in terms of building monomers, functional groups, and metal hybridization for photocatalytic production of hydrogen. Adetailed correlation is conducted between the structural features of porous frameworks and photocatalysis capability. In addition, we summarized the advantages of porous materials for photocatalytic hydrogen production and future development.

Enhanced Visible-Light Photocatalysis Activity of TiO2/Ag Nanocomposites Prepared by the Ultrasound-Assisted Sol–Gel Method: Characterization and Degradation–Mineralization of Cationic and Anionic Dyes

Coupling TiO2 with various elements could enhance its photocatalytic activity. In this study, an innovative ultrasound-assisted sol–gel method was used to synthesize TiO2/Ag(x%) by varying Ag–support mass (x = 9.3, 17.1, and 23.6%), followed by calcination at 450 °C for 30 min. The aim was to demonstrate that Ag compositing improves photoactivity under visible light (>400 nm). The synthesized photocatalysts were assessed for their effectiveness in the degradation and mineralization of Methylene Blue (MB) and Acid Orange 7 (AO7) using visible lamps emitting in the range of 400–800 nm. Characterization of the prepared photocatalysts was performed by using Raman spectroscopy, SEM/EDS, pHpzc, and UV–visible spectroscopy. Raman spectroscopy confirmed the predominance of the anatase phase in all the photocatalysts. The photodegradation efficiencies of the selected dyes, MB and AO7, reached 99% (pH 6) and 95% (pH 3) after 180 min of irradiation, respectively. The best performance for the degradation of the two dyes was observed with TiO2/Ag9.3%, showing optimal kinetics at this doping concentration. The improved photoactivity of the TiO2/Ag composite is due to a decrease in the recombination rate of electron/hole (e−/h+) and a decrease in the band gap from 3.13 to 2.49 eV. The mineralization rate of both dyes under visible light is about 9.3%, indicating the presence of refractory by-products that resist complete degradation. Under UVA irradiation, complete mineralization is obtained. This study confirms the potential of TiO2/Ag composite as a high-performance and cost-effective photocatalyst for solar environmental remediation, highlighting the role of silver in extending light absorption into the visible region and improving charge separation.

Annealing construction of in situ heterojunction for photocatalytic degradation of bisphenol A

Here, we report the synthesis of bismuth oxyiodide (BiOI) photocatalysts with oxygen vacancy defects by a one-pot solvothermal method followed by annealing in a nitrogen atmosphere. This method allows the oxygen vacancy concentration to be tuned and provides new insights into defect engineering of photocatalytic materials. We found that the Bi2O3/BiOI heterojunction formed after annealing at 400°C significantly improves the photocatalytic performance, which provides a new strategy for the optimal design of structures for efficient photocatalysts. Using a combination of characterization techniques such as X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), as well as density-functional theory (DFT) calculations, we have elucidated the photocatalytic mechanism of the Bi2O3/BiOI heterojunctions, highlighting their role in facilitating the photogenerated charge-carrier separation and transfer. The optimized A-B40 samples exhibited photocatalytic degradation efficiencies of up to 99.7% for bisphenol A (BPA), highlighting their potential for remediation of environmental pollutants. This study presents a method for the preparation of high-performance BiOI-based photocatalysts, which offers valuable theoretical and experimental prospects for the development of eco-friendly photocatalytic materials.

Synthesis of high-performance photocatalysts for solar-driven hydrogen production and carbon dioxide reduction

Synthesis of high-performance photocatalysts for solar-driven hydrogen production and carbon dioxide reduction

Highly efficient BODIPY-based covalent triazine frameworks for photocatalytic H2O2 production and photodegradation

Photocatalysts based on covalent triazine frameworks (CTFs) showcased excellent prospect in treating wastewater contaminated with organic compounds. However, effectively combining adsorption and degradation processes presents a significant hurdle for enhancing photocatalytic efficiency. This work focuses on the elegant design of an advanced photocatalyst based on sulfonated A-D-A-type CTFs, with enhanced photosynthesis of H2O2, and photodegradation efficiency of 99 % degradation of 10 ppm BPA in just 15 min and 25 ppm RhB in only 5 min. This enhancement can be ascribed to heightened photocurrent mobility, significant reduction in electrochemical impedance, narrowed band gap, and enhanced dispersibility compared to the non-sulfonated counterpart of the CTF-based photocatalyst. Mechanistic investigations suggested that the photodegradation of BPA and RhB are dominated by ·O2– and 1O2, respectively. This finding will provide a useful guide to the design of high-performance photocatalyst for wastewater remediation.

Molecular Engineering of Covalent Organic Frameworks for Photocatalytic Hydrogen Evolution from Water.

Covalent organic frameworks (COFs) have demonstrated significant potential as photocatalysts for efficiently generating hydrogen through photocatalytic water splitting. However, the design of COFs with distinct organic unit blocks at a molecular level profoundly influences their photocatalytic performance. In this study, we synthesized a series of β-ketoamine COFs through molecular engineering of nitrogen sites, including phenyl-structured TpBD, phenylpyridine-structured TpPpy, phenylpyrimidine-structured TpPpm, and bipyridine-structured TpBpy. Advanced characterization techniques reveal that TpPpm and TpBpy with more nitrogen sites exhibit superior efficiencies in electron transfer and charge separation compared to TpBD and TpPpy, thereby endowing them with enhanced photocatalytic performance for hydrogen evolution from water. As a result, the photocatalytic hydrogen production rates of TpPpm (33.80 mmol g-1 h-1) and TpBpy (29.18 mmol g-1 h-1) surpass those of TpBD (20.82 mmol g-1 h-1) and TpPpy (27.49 mmol g-1 h-1). Additionally, due to the different plane symmetries between Ppm and Bpy resulting from the various positions of nitrogen sites, TpPpm displays superior photochemical properties and better photocatalytic performance compared to TpBpy. Moreover, theoretical calculation results further confirm the exceptional intramolecular charge transfer ability of TpPpm among all COFs. This work underscores the significance of precisely controlling N sites in COFs for designing high-performance photocatalysts.

Construction of 3D nanoflower Bi2WO6/Bi4O5Br2 Z-scheme heterojunction with an internal electric field for enhanced photocatalytic activity

For photocatalytic technology, the establishment of an internal electric field has garnered significant attention due to its remarkable efficacy in facilitating the separation of photogenerated charge carriers. In this study, a 3D nanoflower Bi2WO6/Bi4O5Br2 Z-type heterojunction was successfully synthesized. Notably, 11WB demonstrated excellent photocatalytic performance, achieving a 94.2% antibacterial rate against Pseudomonas aeruginosa within 30 min and a 93.5% degradation rate of Rhodamine B within 100 min. Characterization and theoretical calculations revealed that the formation of the heterojunction induced an internal electric field at the interface and adhered to the photogenerated charge carriers transfer mechanism characteristic of Z-type heterojunctions, thereby enhancing both separation and transfer efficiency of photogenerated charge carriers, significantly boosting photocatalytic activity. This work is anticipated to offer valuable insights for designing high-performance photocatalysts through the strategic construction of internal electric fields.

The polarization effect promotes 2D GeSe/XS2 (X=Sn, Zr, Hf) van der Waals heterostructure formed S-scheme photocatalyst

S-scheme heterostructures (HSs) have garnered considerable attention due to their advantages, including enhanced redox capabilities and superior light utilization efficiency, positioning S-scheme HSs as a central focus in photocatalysis research and development. In this study, we explored the photocatalytic properties of GeSe/XS2-(A1, B1) HSs through first-principles calculations. Our findings reveal that the establishment of built-in electric fields (Eint) and polarized electric fields (Ep) facilitates the formation of S-scheme HSs within GeSe/XS2-B1 HSs. Moreover, these GeSe/XS2-B1 HSs can spontaneously achieve water splitting under illumination at a pH of 7, demonstrating an exceptionally high solar-to-hydrogen (STH) efficiency exceeding 33.98%, attributed to their S-scheme mechanism and broad light absorption with a high coefficient. Our investigation indicates that GeSe/XS2-B1 HSs represent a promising candidate for robust high-performance photocatalysts.

Visible-Light-Driven Oxidation of Benzene to Phenol with O2 over Photoinduced Oxygen-Vacancy-Rich WO3.

Direct photocatalytic conversion of benzene to phenol with molecular oxygen (O2) is a green alternative to the traditional synthesis. The key is to find an effective photocatalyst to do the trick. Defect engineering of semiconductors with oxygen vacancies (OVs) is an emerging strategy for catalyst fabrication. OVs can trap electrons to promote charge separation and serving as adsorption sites for O2 activation. However, the randomly distribution of OVs on the semiconductor surface often results in mismatching the charge carrier dynamics under irradiation, thus failing to fulfill the unique advantages of OVs for photoredox functions. Herein, we demonstrate that abundant OVs can be facilely generated and precisely located adjacent to the reductive sites on reducible oxide semiconductors such as tungsten oxide (WO3) via a simple photochemistry strategy. Such photoinduced OVs are well suited for photocatalytic benzene oxidation with O2 as they readily capture photogenerated electrons from the reductive sites of WO3 to activate adsorbed O2. The oxygen-isotope-labeling experiments further confirm that the OVs also facilitate the integration of oxygen atoms from O2 into phenol, revealing in detail the pathway for photocatalytic benzene hydroxylation. This study demonstrates that the photochemistry approach is an appealing strategy for the synthesis of high-performance OVs-rich photocatalysts for solar-induced chemical conversion.

Study on the photocatalytic properties of the ternary ZnO/MgAl-LDH/FeOOH composite photocatalyst with a Type-II and S-scheme linked carrier migration mechanism in degrading TC solution

The synthesis of high-performance photocatalysts represents a pivotal aspect of research into photocatalytic degradation technology. In order to address this need, a novel ZnO/MgAl-LDH/FeOOH ternary composite photocatalyst has been synthesized via a multi-step process involving the hydrothermal, calcination and ultrasonic-assisted wet impregnation methods. The ternary composite photocatalyst was observed to demonstrate effective separation of photogenerated carriers in photocatalysis, following a Type-II and S-scheme linked carrier migration mechanism. An examination of the photocatalytic characteristics of the composite photocatalyst in the degradation of a tetracycline (TC) solution revealed that the reduction of •O2- radicals and the oxidation of •OH radicals resulted in the effective degradation of the TC solution. The degradation efficiency of the TC solution under the photocatalysis of the ternary composite photocatalyst was observed to be 1.54, 1.11 and 3.15 times that of the single-component samples of ZnO, MgAl-LDH and FeOOH, respectively, in 30 min. Moreover, the degradation pathway of TC molecules under the photocatalysis of the composite has been elucidated. The research findings provide a foundation for further investigation into this composite photocatalyst.

Unlocking Topological Effects in Covalent Organic Frameworks for High-Performance Photosynthesis of Hydrogen Peroxide.

Covalent organic frameworks (COFs) offer a compelling platform for the efficient photosynthesis of hydrogen peroxide (H2O2). Constructed with diverse topologies from various molecular building units, COFs can exhibit unique photocatalytic properties. In this study, three π-conjugated 2D sp2 carbon-linked COFs with distinctly different topologies (hcb, sql, and hxl) are designed to investigate the topological effect on the overall photosynthesis of H2O2 from water and oxygen. Despite their similar chemical and band structures, the QP-HPTP-COF with hxl topology outperformed other COFs in the photosynthesis of H2O2, demonstrating a remarkable solar-to-chemical conversion efficiency of 1.41%. Comprehensive characterizations confirmed that the hxl topology can substantially improve charge separation and transfer, thereby significantly enhancing photocatalytic performance. This study not only unravels the topology-directed charge carrier dynamics in COFs but also establishes a molecular engineering framework for developing high-performance photocatalysts for sustainable H2O2 production.

CuO/Cu(OH)2@g-C3N4 derived from CuBTC/g-C3N4 for two channel photocatalytic hydrogen peroxide production

Photocatalytic production of H2O2 is indeed a safe, sustainable and cost-effective technology, offering an environmentally friendly solution to the energy crisis through solar photocatalysis. However, it still faces challenges such as reliance on organic electron donors and pure O2, as well as inefficiencies in hole utilization. To overcome these limitations, a dual-channel photocatalytic system has been developed. In this study, we showcase the efficiency of the CuO/Cu(OH)2@g-C3N4 composite, derived from CuBTC/g-C3N4 via NaOH treatment, as a high-performance dual-channel photocatalyst for H2O2 production. Under visible light (λ ≥ 420 nm), this composite achieves a H2O2 yield of 1354 μmol/L in 120 min without any sacrificial agent, outperforming g-C3N4 by 8.4 times, CuO by 13.6 times and CuO@g-C3N4 by 1.9 times. Quenching experiments and electron paramagnetic resonance spectra confirmed that HO• and O2•− are intermediate products in the photocatalytic process, following a two-step single-electron reaction pathway. The superior activity of CuO/Cu(OH)2@g-C3N4 in H2O2 generation can be attributed to the synergistic effects of OH bonds on the CuO@g-C3N4 Z-type heterojunction and Cu(OH)2. This research presents a straightforward and promising approach for developing highly efficient photocatalysts for energy conversion.

Harnessing visible light for sustainable biodiesel production with Ni/Si/MgO photocatalyst

Sustainable energy sources frequently demonstrate greater reliability and resilience in comparison to conventional energy sources. Biodiesel, with its markedly reduced carbon footprint when compared to petroleum-based diesel fuel, owes this advantage to its production from renewable resources. Heterojunction photocatalysts have gained significant interest due to their immense promise in tackling environmental challenges. In this study, a highly efficient photocatalyst, Ni/Si/MgO, for biodiesel production under visible light irradiation was synthesized using a solid-phase reaction method with silica as the silicon source, along with Ni and MgO. The surface functionality of Ni/Si/MgO was crucial for achieving high efficiency of photocatalytic systems, as evident from XPS. The transesterification reaction on the Ni/Si/MgO photocatalyst proceeds by the formation of SiH and SiOH bonds over the catalyst. The photocatalytic activities of Ni/Si/MgO photocatalysts were higher than those of the Si/MgO nanoparticle when exposed to light. Achieving an optimal yield of 98 %, the biodiesel production was carried out under the following reaction conditions: A catalyst dosage of 2 % by weight was utilized, along with a methanol-to-oil molar ratio of 12:1, and the entire procedure was executed within a duration of 3.5 h. Plasmonic near-fields are speculated to be responsible for the increased transesterification activity along the Ni/Si/MgO interface. In order to carry out the transesterification reaction, electron-hole pairs are generated along the Ni/Si/MgO interface, where plasmonic near-fields are highly concentrated. This study contributes a significant perspective on mechanisms governing the process of efficient plasmonic photocatalysis responsive to visible light. These findings hold the potential to offer valuable guidance in the formulation and design of next-generation, high-performance photocatalysts.

One-step construction of Sn-doped Bi2MoO6 nanosheets for enhanced photocatalytic organic pollutants degradation and Cr(VI) reduction

Photocatalytic technology is widely used to remove environmental pollutants, and the development of high-performance photocatalysts is an important prerequisite for boosting photocatalytic processes. Herein, Sn-doped Bi2MoO6 nanosheets were constructed by one-step solvothermal method. The experimental results indicate that the Sn doping not only tunes the band structure of Bi2MoO6, but also effectively promotes the photogenerated charge separation, thus providing abundant free charge for photocatalytic reactions. The optimized Sn-Bi2MoO6-2 sample shows the degradation efficiency of TC and MBT reaching 81% (for 3hours) and 85% (for 2hours), respectively, and the removal efficiency of Cr(VI) is 1.5 times compared with that of pristine Bi2MoO6. Moreover, the experiments with different pH, inorganic cations and anions were carried out to investigate the practical application potential of the photocatalyst, and the Sn-Bi2MoO6-2 also exhibits excellent photocatalytic performance for decomposing antibiotic contaminants in river water. Furthermore, mass spectra and radical trapping experiments explored the possible photocatalytic degradation processes. This work explored the multiple positive roles of Sn-Bi2MoO6 materials in the photocatalytic system, which provides a promising strategy for constructing efficient photocatalysts for environmental remediation.

Preparation of S-scheme heterojunction photocatalyst Y2O3/BiOCl and visible light degradation of ofloxacin: photocatalytic mechanism, DFT calculation, degradation pathway, and toxicity evaluation

The contamination of antibiotics and heavy metals in water is a growing concern, and photocatalytic technology offers a green and efficient solution for removing contaminants from water. In this paper, a novel S-scheme heterojunction photocatalyst Y2O3/BiOCl was successfully designed and synthesized. The degradation of ofloxacin by Y2O3/BiOCl-3 composite photocatalyst under visible light was 87.81%. The main active substance that acts is ·O2-. The proposed primary kinetic constant was 0.0151min-1, 4.98 and 17.97 times higher than BiOCl and Y2O3, respectively. The improved photocatalytic properties exhibited by Y2O3/BiOCl composites stem from establishing an S-scheme heterojunction interface between Y2O3 and BiOCl, significantly enhancing their visible light harvesting capability and facilitating an efficient separation of charge carriers. The pathways and byproducts associated with the degradation of OFX were thoroughly investigated utilizing Density Functional Theory along with High-Resolution Liquid Chromatography coupled with Mass Spectrometry. Furthermore, an assessment of the potential toxicity exhibited by the intermediary degradation compounds was conducted. This article combines Y2O3 with BiOCl to form a photocatalytic material, providing a reference for designing high-performance photocatalysts.

Investigating the role of internal electric fields on interfacial charge transfer dynamics in 2D MoSTe/WSeTe heterojunction for photocatalytic water splitting

Introducing the degrees of freedom brought by intrinsic dipole moments into heterojunctions allows for effective manipulation through the combination of different interfaces, thus offering more possibilities for designing high-performance photocatalysts. The influence of internal electric fields (EIN) in Janus materials on heterojunction interface charges is a crucial aspect of understanding the intrinsic mechanisms of charge transfer at interfaces. To address this, we construct four contact modes of MoSTe/WSeTe heterojunctions, considering the work function difference as a mediator to quantify two different electric fields. It is estimated that the influence of the interfacial electric field (EIF) on interfacial charge transfer is approximately 1.6 times that of the EIN (pointing outwards the interface). Moreover, the direction of the EIN varies, resulting in different impacts on interface charges. Subsequently, we also discuss the conditions under which different charge transfer modes are formed at different contact surfaces. On the other hand, the heterojunction of the Te-S mode can serve as a direct Z-Scheme photocatalyst for overall water splitting, and the presence of vacancies is necessary to address the issue of surface passivation. Our study not only refines the intrinsic mechanism of interfacial charge transfer in Janus-based heterojunctions but also predicts a direct Z-Scheme photocatalyst capable of achieving overall water splitting.

Synthesis of Carbon Nitride Polymorphs by Sacrificial Template Method: Correlation between Physicochemical Properties and Photocatalytic Performance.

Carbon nitride compounds (CNCs) in the form of graphitic carbon nitride (g-C3N4) and poly(heptazine imide) were synthesized using different metal chloride salts (MClx), i. e., NaCl, KCl and CaCl2, as sacrificial templates and by varying the MClx to melamine molar ratios. A systematic study of their photocatalytic activity for H2 production in relation to the physicochemical, morphological, and optical properties was carried out. Each sample was tested achieving the highest hydrogen evolution rates of about 7660 μmol g-1 h-1, 5380 μmol g-1 h-1 and 3140 μmol g-1 h-1 using CaCl2, KCl, and NaCl, respectively. This work demonstrates how the synthesis of CNCs with different MClx leads to the production of high-performance photocatalysts due to a combination of factors as the formation of vacancies or cyano groups, a shift in the optical threshold and tuning of micro(nano)structure. The results demonstrate that, when CaCl2 is used as a sacrificial template, porous and exfoliated g-C3N4 nanosheets are formed leading to hydrogen productions which outperform most of the previously reported g-C3N4 prepared using a single synthetic step.

ZnIn2S4 nanosheets with geometric defects for enhanced solar-driven hydrogen evolution and wastewater treatment

The key to development of high-performance and low cost photocatalysts hydrogen evolution and waste degradation is to realize efficient photo-generated charge carrier separation and surface catalytic reaction simultaneously without noble metal co-catalyst. To achieve this goal, a noble metal free ZnIn2S4 photocatalyst with geometric defects has been constructed, in which [In-S]4 tetrahedral vacancies (named as (InS)v) on the surface are created by removing the In and S atoms. Further mechanistic investigation has revealed that the (InS)v not only works as the active sites for reductive reaction, but also improves photo-generated electron-hole separation. As a result, the solar-driven hydrogen evolution rate reaches 10.70 mmol/gh without co-catalyst after optimizing the densities of the (InS)v. The apparent quantum efficiency at 380 nm, 395 nm, 420 nm, 450 nm and 520 nm is as high as 14.0 %, 17.1 %, 12.1 %, 8.2 % and 2.4 %, respectively. In addition, these photocatalysts also achieve a rate of 97.78 % and 91.27 % of RhB and MO within 3 and 60 min, respectively. This work show-case a novel approach to develop dual functional and noble metal free photocatalysts for efficiently utilizing solar energy for hydrogen generation and wastewater treatment.