Emerging frontiers of Z-scheme photocatalytic systems

Renewable hemicellulose-based materials for value-added applications

The importance of renewable resources and environmentally friendly materials has grown globally in recent time. Hemicellulose is renewable lignocellulosic materials that have been the subject of substantial valorisation research. Due to its distinctive benefits, including its wide availability, low cost, renewability, biodegradability, simplicity of chemical modification, etc., it has attracted increasing interest in a number of value-added fields. In this review, a systematic summarizes of the structure, extraction method, and characterization technique for hemicellulose-based materials was carried out. Also, their most current developments in a variety of value-added adsorbents, biomedical, energy-related, 3D-printed materials, sensors, food packaging applications were discussed. Additionally, the most recent challenges and prospects of hemicellulose-based materials are emphasized and examined in-depth. It is anticipated that in the near future, persistent scientific efforts will enable the renewable hemicellulose-based products to achieve practical applications.

Oxygen vacancies and Y-O-Ag bonds in the Z-scheme heterojunction cooperate to promote photodegradation of organic pollutants

Y2O3 is a cost-effective and environmentally friendly wide-band gap photocatalyst with extensive application potential. However, its limited ability to be excited by visible light restricts its practical uses. In this study, we coupled the narrow bandgap semiconductor AgI with Y2O3 to form a Z-scheme heterostructure, significantly promoting its photocatalytic degradation activity. Characterization and experimental results demonstrated the formation of Y-O-Ag bonds through coupling with AgI, leading to an increase in oxygen vacancies in Y2O3, which promotes the chemisorption of H2O and O2. The Y-O-Ag bond introduction promotes electron transfer, improves hole utilization, and boosts energy transfer efficiency, thus promoting the efficient generation of ·OH and 1O2. The photocatalytic degradation rates of RhB and o-nitrophenol by 7.5% AgI/Y2O3 were 26.5 and 4 times higher than those of pure Y2O3, respectively. This study provides theoretical support for the Z-scheme heterojunction to improve photocatalytic activity and offers efficient solutions and practical design ideas for sewage purification.

In-situ producing CsPbBr3 nanocrystals on (001)-faceted TiO2 nanosheets as S‑scheme heterostructure for bifunctional photocatalysis

Fabricating a cost-effective yet highly active photocatalyst to reduce CO2 to CO and oxidize benzyl alcohol to benzaldehyde simultaneously, is challenging. Herein, we construct an S-scheme 0D/2D CsPbBr3/TiO2 heterostructure for bifunctional photocatalysis. An in-situ synthetic route is used, which enables the precise integration between CsPbBr3 nanocrystals and ultrathin TiO2 nanosheets exposed with (001) facets (termed as TiO2-001), resulting in a tightly coupled heterointerface and desirable band offsets. The as-prepared CsPbBr3/TiO2-001heterojunctions exhibit boosted charge carrier kinetics, particularly, quick carrier separation/transfer and efficient utilization. Experimental results and theoretical calculations validate the S-scheme route in CsPbBr3/TiO2-001, which allows the enrichment of strongly conserved electrons-holes at conduction and valence bands of CsPbBr3 and TiO2-001, respectively. Consequently, compared to its counterparts, an excellent bifunctional activity (with 24 h reusability) is realized over CsPbBr3/TiO2-001, where the production rate of CO and benzaldehyde reach up to 78.06 μmol g-1h-1 and 1.77 mmol g-1h-1 respectively, without employing any sacrificial agents. This work highlights the development of perovskite-based heterostructures and describes the efficient harnessing of redox potentials and charge carriers towards combined photocatalytic systems.

Novel Z-scheme MgFe2O4/Bi2WO6 heterojunction for efficient photocatalytic degradation of tetracycline hydrochloride: Mechanistic insight, degradation pathways and density functional theory calculations

In this study, a new Z-scheme MgFe2O4/Bi2WO6 heterojunction was successfully prepared by hydrothermal and wet ball milling process. The results of the study showed that after 90 min of visible light exposure, the photocatalytic degradation of tetracycline hydrochloride (TCH) by 25%-MgFe2O4/Bi2WO6 heterojunction was as high as 95.82%, and the highest photocatalytic rate (0.0281 min-1) was 4.61 and 3.43 times higher than that of pure Bi2WO6 (0.0061 min-1) and MgFe2O4 (0.0082 min-1), respectively. Furthermore, spin-polarized density functional theory (DFT) calculations were performed to provide additional evidence of the presence of a Z-scheme charge transfer mechanism between MgFe2O4 and Bi2WO6. We investigated the effects of initial TCH concentration, pH, coexisting ions and different water sources on the efficiency of photocatalytic degradation of TCH in composite samples. The recovery experiments demonstrated that the MgFe2O4/Bi2WO6 composites had good stability and repeatability. A series of experimental results showed that 25%-MgFe2O4/Bi2WO6 had a larger specific surface area, better ultraviolet and visible absorbance, superior charge transfer and higher efficiency of photogenerated electron-hole pair separation. This paper provides new ideas for the design and preparation of new Z-scheme heterojunctions and has great prospects for practical applications in the field of wastewater treatment.

Recent Advances in LDH/g-C3N4 Heterojunction Photocatalysts for Organic Pollutant Removal

Environmental pollution has been decreased by using photocatalytic technology in conjunction with solar energy. An efficient method to obtain highly efficient photocatalysts is to build heterojunction photocatalysts by combining graphitic carbon nitride (g-C3N4) with layered double hydroxides (LDHs). In this review, recent developments in LDH/g-C3N4 heterojunctions and their applications for organic pollutant removal are systematically exhibited. The advantages of LDH/g-C3N4 heterojunction are first summarized to provide some overall understanding of them. Then, a variety of approaches to successfully assembling LDH and g-C3N4 are simply illustrated. Last but not least, certain unmet research needs for the LDH/g-C3N4 heterojunction are suggested. This review can provide some new insights for the development of high-performance LDH/g-C3N4 heterojunction photocatalysts. It is indisputable that the LDH/g-C3N4 heterojunctions can serve as high-performance photocatalysts to make new progress in organic pollutant removal.

One-step photodeposition of spatially separated CuOx and MnOx dual cocatalysts on g-C3N4 for enhanced CO2 photoreduction

The rapid recombination of photogenerated carriers of photocatalysts greatly limits their actual application in CO2 conversion into valuable chemicals. Herein, dual CuOx and MnOx cocatalysts are decorated on g-C3N4 nanosheets via a one-step photodeposition strategy. Benefiting from the repulsion between Cu2+ and Mn2+ cations, a novel g-C3N4-based heterostructure loaded with spatially separated CuOx and MnOx nanoparticle dual cocatalysts has been successfully fabricated. Cu favors the trapping of electrons, while MnOx tends to collect holes. Moreover, the Cu2O/g-C3N4 p-n heterojunction also accelerates the charge separation. As a result, the photogenerated holes and electrons flow into and out of the photocatalyst, respectively, resulting in enhanced charge separation for achieving efficient CO2 photoreduction over CuOx/g-C3N4/MnOx. Accordingly, the optimized CuOx/g-C3N4/MnOx exhibits an improved CO production rate of 5.49 μmol g-1 h-1, which is 27.5 times higher than that of bare g-C3N4.

Designing Non-Fluorinated Superhydrophobic Fabrics with Durable Stability and Photocatalytic Functionality

The ability of a superhydrophobic fabric to stay dry and clean has aroused great interest in daily life. Especially, the development of an eco-friendly non-fluorinated water-repellent textile has become a hot topic in recent years. We present a green strategy to achieve self-cleaning textile by in situ deposition of zinc oxide (ZnO) nanoparticles on cotton with subsequent polydimethylsiloxane modification. The prepared cotton fabric exhibits superior water repellency with a water contact angle of 157°. Meanwhile, this superhydrophobic surface can easily be ruined by oil contaminants and then exhibit a decreased water contact angle of 0°. However, the oil-contaminated surface can recover its water repellency after being irradiated. After six cycles of contamination using oleic acid and successive photodegradation, the fabric surface remains superhydrophobic. The obtained superhydrophobic surface does not adversely affect the fabric's strength and air permeability. Therefore, the developed superhydrophobic cotton fabrics have the potential to be used in a variety of industrial scenarios and in daily life.

Noble metal-free ternary cobalt-nickel phosphides for enhanced photocatalytic dye-sensitized hydrogen evolution and catalytic mechanism investigation

Transition metal phosphides have emerged as compelling alternatives to noble metal catalysts for photocatalytic hydrogen evolution, owing to their high efficiency, stability, ease of preparation, and low-cost-effectiveness. This study investigates a series of binary and ternary phosphides predominantly composed of cobalt and nickel employed for photocatalytic dye-sensitized hydrogen evolution. Under the optimal dye-to-catalyst mass ratio, CoNiP exhibited the highest hydrogen evolution activity (12.96 mmol g-1 h-1), demonstrating more significant and satisfactory performance than a variety of other reported materials. This can be attributed to the high conductivity and low hydrogen evolution overpotential of phosphides, which result from their metallic characteristics and the presence of free electrons, which promote efficient electron transfer between the catalyst and sensitizer. Density functional theory calculations revealed that the cobalt incorporation into the binary phosphides causes a negative shift in the average d-band center for CoNiP, weakening the adsorption affinity of the catalyst towards H2 molecules, thus effectively improving the hydrogen evolution rate compared to the pure binary phosphides. This work provides valuable insights for the development of low-cost and high-performance ternary phosphide photocatalysts.

Fe3O4 quantum dots mediated P-g-C3N4/BiOI as an efficient and recyclable Z-scheme photo-Fenton catalyst for tetracycline degradation and bacterial inactivation

Photo-Fenton technology integrated by photocatalysis and Fenton reaction is a favorable strategy for water remediation. Nevertheless, the development of visible-light-assisted efficient and recyclable photo-Fenton catalysts still faces challenges. This study successfully constructed a novel separable Z-scheme P-g-C₃N₄/Fe₃O₄QDs/BiOI (PCN/FOQDs/BOI) heterojunction via in-situ deposition method. The results showed that the photo-Fenton degradation efficiency for tetracycline over optimal ternary catalyst reached 96.5% within 40 min at visible illumination, which was 7.1 and 9.6 times higher than its single photocatalysis and Fenton system, respectively. Moreover, PCN/FOQDs/BOI possessed excellent photo-Fenton antibacterial activity, which could completely inactivate 10⁸ CFU·mL^-1 of E. coli and S. aureus within 20 and 40 min, respectively. Theoretical calculation and in-situ characterization revealed that the enhanced catalysis behavior resulted from the FOQDs mediated Z-scheme electronic system, which not only facilitated photocreated carrier separation of PCN and BOI while maintaining maximum redox capacity, but also accelerated H₂O₂ activation and Fe³⁺/Fe²⁺ cycle, thus synergistically forming more active species in system. Additionally, PCN/FOQDs/BOI/Vis/H₂O₂ system displayed extensive adaptability at pH range of 3-11, removal universality for various organic pollutants and attractive magnetic separation property. This work would provide an inspiration for design of efficient and multifunctional Z-scheme photo-Fenton catalyst in water purification.

Recent Advances in Porous Carbon Materials as Electrodes for Supercapacitors

Porous carbon materials have demonstrated exceptional performance in various energy and environment-related applications. Recently, research on supercapacitors has been steadily increasing, and porous carbon materials have emerged as the most significant electrode material for supercapacitors. Nonetheless, the high cost and potential for environmental pollution associated with the preparation process of porous carbon materials remain significant issues. This paper presents an overview of common methods for preparing porous carbon materials, including the carbon-activation method, hard-templating method, soft-templating method, sacrificial-templating method, and self-templating method. Additionally, we also review several emerging methods for the preparation of porous carbon materials, such as copolymer pyrolysis, carbohydrate self-activation, and laser scribing. We then categorise porous carbons based on their pore sizes and the presence or absence of heteroatom doping. Finally, we provide an overview of recent applications of porous carbon materials as electrodes for supercapacitors.

Z-scheme WOx/Cu-g-C3N4 heterojunction nanoarchitectonics with promoted charge separation and transfer towards efficient full solar-spectrum photocatalysis

Construction of Z-scheme heterojunctions has been considered one superb method in promoting solar-assisted charge carrier separation of carbon-based materials to achieve efficient utilization of solar energy in hydrogen production and CO₂ reduction. One interesting concept in nanofabrication that has become trend recent years is nanoarchitectonics. A heterostructure photocatalyst constructed based on the idea of nanoarchitectonics using the combination of g-C₃N₄, metal and an additional semiconducting nanocomposite is investigated in this paper. Z-scheme tungsten oxide incorporated copper modified graphitic carbon nitride (WO_x/Cu-g-C₃N₄) heterostructures are fabricated via immobilization of WO_x on Cu nanoparticles modified superior thin g-C₃N₄ nanosheets. Mechano-chemical pre-reaction and a two-step high-temperature thermal polymerization process are the keys in attaining homogeneous distribution of Cu nanoparticles in g-C₃N₄ nanosheets. The horizontal growth of homogeneously distributed WO_x nanobelts on Cu modified g-C₃N₄ (Cu-g-C₃N₄) base via solvothermal synthesis is achieved. The photocatalytic performances of the heterostructures are evaluated through water splitting and CO₂ photoreduction measurements in full solar spectrum irradiation condition. The presence of Cu nanoparticles in the composite system improves charge transport between g-C₃N₄ and WO_x and thus enhances the photocatalytic performances (H₂ generation and CO₂ photoreduction) of the composite material, while the presence of WO_x nanocomposites enhances light absorption of the composite material in the near infrared range. The synthesized heterostructure with optimized WO_x to Cu-g-C₃N₄ ratio and in case of no co-catalyst addition exhibits enhanced photocatalytic H₂ evolution (4560 μmolg^-1h^-1) as well as excellent CO₂ reduction rate (5.89 μmolg^-1h^-1 for CO generation).

Optimized fabrication of Cu-doped ZnO/calcined CoFe‒LDH composite for efficient degradation of bisphenol a through synergistic visible-light photocatalysis and persulfate activation: Performance and mechanisms

A novel magnetically separable Cu/ZnO/CoFe‒CLDH composite, whose synthesis was optimized using the Taguchi approach, was optimally synthesized by hydrothermally coupling Cu-doped ZnO and calcined CoFe-LDH. The synthesized Cu/ZnO/CoFe‒CLDH was applied to construct a synergistic process of integrating visible-light photocatalysis (VPC) with persulfate activation (PSA) and to degrade bisphenol A (BPA). Various characterizations proved that Cu/ZnO/CoFe‒CLDH possessed excellent physicochemical, optoelectronic and magnetic properties, thereby enhancing the catalytic performance. The Cu/ZnO/CoFe‒CLDH composite achieved highly efficient BPA degradation during the synergistic VPC‒PSA process, and its reaction rate constant (0.74 h^-1) was 6.17-, 4.11-, and 2.85-fold higher than that of Cu/ZnO, CoFe‒CLDH, and Cu/ZnO/CoFe‒CLDH (VPC only), respectively. Moreover, the effects of the catalyst dosage, initial pollutant concentration, solution pH, persulfate dosage and coexisting ions on BPA degradation were comprehensively investigated. Radical-trapping experiments revealed that the contributions of ·OH, SO₄·^‒, ·O₂^-, and ¹O₂ involved in BPA degradation. Based on the intermediates identified by LC/MS, the main BPA degradation pathways were determined, the overall trend of which reflects a decreasing ecotoxicity. This study verified the effectiveness of the synergistic VPC‒PSA process with Cu/ZnO/CoFe‒CLDH, which could be used as a new reference for removing organic micropollutants from water.

Carbon Dots Based Photoinduced Reactions: Advances and Perspective

Seeking clean energy as an alternative to traditional fossil fuels is the inevitable choice to realize the sustainable development of the society. Photocatalytic technique is considered a promising energy conversion approach to store the abundant solar energy into other wieldy energy carriers like chemical energy. Carbon dots, as a class of fascinating carbon nanomaterials, have already become the hotspots in numerous photoelectric researching fields and particularly drawn keen interests as metal-free photocatalysts owing to strong UV-vis optical absorption, tunable energy-level configuration, superior charge transfer ability, excellent physicochemical stability, facile fabrication, low toxicity, and high solubility. In this review, the classification, microstructures, general synthetic methods, optical and photoelectrical properties of carbon dots are systematically summarized. In addition, recent advances of carbon dots based photoinduced reactions including photodegradation, photocatalytic hydrogen generation, CO₂ conversion, N₂ fixation, and photochemical synthesis are highlighted in detail, deep insights into the roles of carbon dots in various systems combining with the photocatalytic mechanisms are provided. Finally, several critical issues remaining in photocatalysis field are also proposed.

Anchored Cu single atoms on porous g-C3N4 for superior photocatalytic H2 evolution from water splitting

One of the most promising strategies for producing hydrogen is photocatalytic water splitting, in which the photocatalyst is a key component. Among many semiconductor photocatalysts, g-C₃N₄ has attracted great attention due to its narrow band gap, excellent stability and low cost. However, practical application is limited by its poor intrinsic activity. In this work, a high-performance porous g-C₃N₄ (PCN) photocatalyst with anchored Cu single atoms (CuSAs) was synthesized by a one-step co-heating approach. The obtained Cu1.5-PCN displays an excellent hydrogen evolution rate (HER) of 2142.4 μmol h^-1 g^-1 under visible light (=420 nm), which is around 15 and 109 times higher than those of PCN and bulk g-C₃N₄, respectively. In addition, it also shows good stability during H₂ evolution. The results of experimental research and DFT simulations indicate that the single Cu ions formed bonds with the N-ring and these remain stable. Meanwhile, the special electronic structure of the Cu-N charge bridge extends the light absorption band to the visible-light region (380-700 nm). This high-performance and low-cost photocatalyst has great potential in solar energy conversion.

Tunable Donor-Acceptor Linear Conjugated Polymers Involving Cyanostyrylthiophene Linkages for Visible-Light-Driven Hydrogen Production

In this paper, an atom- and step-economic direct C-H arylation polymerization (DArP) strategy was developed to access cyanostyrylthiophene (CST)-based donor-acceptor (D-A) conjugated polymers (CPs) used for photocatalytic hydrogen production (PHP) from water reduction. The new CST-based CPs CP1-CP5 with varied building blocks were systematically studied by X-ray single-crystal analysis, FTIR, scanning electron microscopy, UV-vis, photoluminescence, transient photocurrent response, cyclic voltammetry measurements, and a PHP test, which showed that the phenyl-cyanostyrylthiophene-based CP3 exhibits a superior hydrogen evolution rate (7.60 mmol h^-1 g^-1) compared to other conjugated polymers. The structure-property-performance correlation results obtained in this study will provide an important guideline for the rational design of high-performance D-A CPs for PHP applications.

Enhanced Titania Photocatalyst on Magnesium Oxide Support Doped with Molybdenum

Titania photocatalysts supported on mesoporous MgO carriers doped with Mo(VI) ions were prepared and characterized by XRD, BET nitrogen adsorption, FT-IR, and EPR methods. The photocatalytic activity was evaluated by bleaching an aqueous dye solution in the presence of a dispersed photocatalyst and by bleaching the dry surface of a solid tablet of photocatalyst using rhodamine B and nigrosin as model organic pollutants. It was established that TiO2 photocatalyst based on MgO carrier doped with 1 wt.% Mo(VI) ions, with the ratio of MgO:TiO2 = 1:0.5, possessed the highest activity under UV radiation. The increase in the content of molybdenum up to 10 wt.% leads to the formation of a MoO3 nanophase on the MgO surface, the formation of an isotype n–n heterojunction at the MoO3/TiO2 interface, and photocatalytic activity under the action of visible light.

Preparation and Performance Study of the Anodic Catalyst Layer via Doctor Blade Coating for PEM Water Electrolysis

The membrane electrode assembly (MEA) is the core component of proton exchange membrane (PEM) water electrolysis cell, which provides a place for water decomposition to generate hydrogen and oxygen. The microstructure, thickness, IrO₂ loading as well as the uniformity and quality of the anodic catalyst layer (ACL) have great influence on the performance of PEM water electrolysis cell. Aiming at providing an effective and low-cost fabrication method for MEA, the purpose of this work is to optimize the catalyst ink formulation and achieve the ink properties required to form an adherent and continuous layer with doctor blade coating method. The ink formulation (e.g., isopropanol/H₂O of solvents and solids content) were adjusted, and the doctor blade thickness was optimized. The porous structure and the thickness of the doctor blade coating ACL were further confirmed with the in-plane and the cross-sectional SEM analyses. Finally, the effect of the ink formulation and the doctor blade thickness of the ACL on the cell performance were characterized in a PEM electrolyzer under ambient pressure at 80 °C. Overall, the optimized doctor blade coating ACL showed comparable performance to that prepared with the spraying method. It is proved that the doctor blade coating is capable of high-uniformity coating.

Efficient Visible-Light Driven Photocatalytic Hydrogen Production by Z-Scheme ZnWO4/Mn0.5Cd0.5S Nanocomposite without Precious Metal Cocatalyst

How to restrain the recombination of photogenerated electrons and holes is still very important for photocatalytic hydrogen production. Herein, Z-scheme ZnWO4/Mn0.5Cd0.5S (ZWMCS) nanocomposites are prepared and are applied as visible-light driven precious metal cocatalyst free photocatalyst for hydrogen generation. The ZnWO4/Mn0.5Cd0.5S nanocomposites with 30 wt% ZnWO4 (ZWMCS-2) can reach a photocatalytic hydrogen evolution rate of 3.36 mmol g−1 h−1, which is much higher than that of single ZnWO4 (trace) and Mn0.5Cd0.5S (1.96 mmol g−1 h−1). Cycling test reveals that the ZMWCS-2 nanocomposite can maintain stable photocatalytic hydrogen evolution for seven cycles (21 h). The type of heterojunction in the ZWMCS-2 nanocomposite can be identified as Z-scheme heterojunction. The Z-scheme heterojunction can effectively separate the electrons and holes, so that the hydrogen generation activity and stability of the ZWMCS-2 nanocomposite can be enhanced. This work provides a highly efficient and stable Z-scheme heterojunction photocatalyst for hydrogen generation.

Surface-Functionalized Ti3C2Tx MXene as a Kind of Efficient Lubricating Additive for Supramolecular Gel

Low interlaminar shear stress, high mechanical strength, and tunable structure make Ti₃C₂T_x MXene a burgeoning star as solid lubricants and lubricant additives. Although surface modification strategy can improve its compatibility with base oils, it will eventually settle due to gravity. Additionally, base oils are prone to leakage, creep, and volatilization, which limit their application. To address these issues, supramolecular gels with surface-modified Ti₃C₂T_x were conceived. Apart from the lubrication effect, the high thermal conductivity of Ti₃C₂T_x MXene accelerated the phase transition rate of supramolecular gels. The thermal-reversible and creep-resistant properties distinguish them from other conventional lubricants. The tribological tests showed that the 500 solvent neutral (SN) supramolecular gel with 0.10 wt % Ti₃C₂T_x-octadecylphosphonic acid (Ti₃C₂T_x-ODPA) reduced the coefficient of friction (COF) by 46.32% and wear volume by 81.18% compared with pure 500SN oil. Moreover, they also performed well in load-carrying capacity, temperature tolerance, and speed adaptability. This work puts forward a new approach to prepare MXene-based lubricants tailored for some severe lubrication conditions. These exceptional features enable their application in rolling bearings, some gears, and other low maintenance mechanisms.

Robust Porous TiN Layer for Improved Oxygen Evolution Reaction Performance

The poor reversibility and slow reaction kinetics of catalytic materials seriously hinder the industrialization process of proton exchange membrane (PEM) water electrolysis. It is necessary to develop high-performance and low-cost electrocatalysts to reduce the loss of reaction kinetics. In this study, a novel catalyst support featured with porous surface structure and good electronic conductivity was successfully prepared by surface modification via a thermal nitriding method under ammonia atmosphere. The morphology and composition characterization-confirmed that a TiN layer with granular porous structure and internal pore-like defects was established on the Ti sheet. Meanwhile, the conductivity measurements showed that the in-plane electronic conductivity of the as-developed material increased significantly to 120.8 S cm−1. After IrOx was loaded on the prepared TiN-Ti support, better dispersion of the active phase IrOx, lower ohmic resistance, and faster charge transfer resistance were verified, and accordingly, more accessible catalytic active sites on the catalytic interface were developed as revealed by the electrochemical characterizations. Compared with the IrOx/Ti, the as-obtained IrOx/TiN-Ti catalyst demonstrated remarkable electrocatalytic activity (η10 mA cm−2 = 302 mV) and superior stability (overpotential degradation rate: 0.067 mV h−1) probably due to the enhanced mass adsorption and transport, good dispersion of the supported active phase IrOx, increased electronic conductivity and improved corrosion resistance provided by the TiN-Ti support.

Z-scheme Bi2O3/CuBi2O4 heterojunction enabled sensitive photoelectrochemical detection of aflatoxin B1 for health care, the environment, and food

Designing a photoelectrochemical (PEC) biosensor with preponderant sensitivity and anti-interference is a challenge for detecting small molecules in real samples with complex matrices. To this end, the Bi₂O₃/CuBi₂O₄ was synthesized in one step to enhance visible light's absorption ability, transferring the interfacial carrier's efficiency, a high-active Z-scheme heterojunction, and a photocathode biosensor was proposed. For the first time, we used the density functional theory to verify a Z-scheme transfer pathway of photogenerated electrons in Bi₂O₃/CuBi₂O₄ and the energy band structure of Bi₂O₃ and CuBi₂O₄, respectively. Bi₂O₃/CuBi₂O₄-based PEC biosensor was developed for competive immunoassay of small molecular, aflatoxin B1 (AFB1) as an example, resulting in a low detection limit of 297.4 fg/mL and a linear range of 1.4 pg/mL-280 ng/mL in urine, water, peanut, and wheat samples. Using spiked experiments, the satisfied repeatability, reproducibility, stability, and specificity of the Bi₂O₃/CuBi₂O₄-based PEC biosensor indicated a promise for application in health care, the environment, and food.

Nanostructured IrO x supported on N-doped TiO2 as an efficient electrocatalyst towards acidic oxygen evolution reaction

Reducing the Ir consumption without compromising the catalytic performance for the oxygen evolution reaction (OER) is highly paramount to promote the extensive development of the environmentally-friendly solid polymer electrolyte water electrolysis (SPEWE) system. Herein, TiO₂ is doped with N through facile NH₃ gas treatment and innovatively employed to support IrO _x nanoparticles towards acidic OER. N-doping action not only dramatically boosts the electrical conductivity and dispersing/anchoring effects of TiO₂, but also effectively improves the electron-transfer procedure. As a result, the IrO _x /N-TiO₂ electrocatalyst exhibits prominent catalyst utilization, catalytic activity and stability. Specifically, the overpotential required to deliver 10 mA cm^-2 is only 270 mV, and the mass activity climbs to 278.7 A g_Ir ^-1 @ 1.55 V_RHE. Moreover, the single cell voltage is only 1.761 V @ 2.0 A cm^-2 when adopting IrO _x /N-TiO₂ as the anode catalyst, which is 44 mV lower than that of the commercial IrO₂ counterpart.

Au-TiO2/Ti Hybrid Coating as a Liquid and Gas Diffusion Layer with Improved Performance and Stability in Proton Exchange Membrane Water Electrolyzer

The liquid and gas diffusion layer is a key component of proton exchange membrane water electrolyzer (PEMWE), and its interfacial contact resistance (ICR) and corrosion resistance have a great impact on the performance and durability of PEMWE. In this work, a novel hybrid coating with Au contacts discontinuously embedded in a titanium oxidized layer was constructed on a Ti felt via facile electrochemical metallizing and followed by a pre-oxidization process. The physicochemical characterizations, such as scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction results confirmed that the distribution and morphology of the Au contacts could be regulated with the electrical pulse time, and a hybrid coating (Au-TiO₂/Ti) was eventually achieved after the long-term stability test under anode environment. At the compaction force of 140 N cm^-2, the ICR was reduced from 19.7 mΩ cm² of the P-Ti to 4.2 mΩ cm² of the Au-TiO₂/Ti. The corrosion current density at 1.8 V (RHE) is 0.689 μA cm^-2. Both the ICR and corrosion resistance results showed that the prepared protective coating could provide comparable ICR and corrosion resistance to a dense Au coating.

g-C3N4-Based Direct Z-Scheme Photocatalysts for Environmental Applications

Photocatalysis represents a promising technology that might alleviate the current environmental crisis. One of the most representative photocatalysts is graphitic carbon nitride (g-C3N4) due to its stability, cost-effectiveness, facile synthesis procedure, and absorption properties in visible light. Nevertheless, pristine g-C3N4 still exhibits low photoactivity due to the rapid recombination of photo-induced electron-hole (e−-h+) pairs. To solve this drawback, Z-scheme photocatalysts based on g-C3N4 are superior alternatives since these systems present the same band configuration but follow a different charge carrier recombination mechanism. To contextualize the topic, the main drawbacks of using g-C3N4 as a photocatalyst in environmental applications are mentioned in this review. Then, the basic concepts of the Z-scheme and the synthesis and characterization of the Z-scheme based on g-C3N4 are addressed to obtain novel systems with suitable photocatalytic activity in environmental applications (pollutant abatement, H2 production, and CO2 reduction). Focusing on the applications of the Z-scheme based on g-C3N4, the most representative examples of these systems are referred to, analyzed, and commented on in the main text. To conclude this review, an outlook of the future challenges and prospects of g-C3N4-based Z-scheme photocatalysts is addressed.

Stainless Steel-Supported Amorphous Nickel Phosphide/Nickel as an Electrocatalyst for Hydrogen Evolution Reaction

Recently, nickel phosphides (Ni-P) in an amorphous state have emerged as potential catalysts with high intrinsic activity and excellent electrochemical stability for hydrogen evolution reactions (HER). However, it still lacks a good strategy to prepare amorphous Ni-P with rich surface defects or structural boundaries, and it is also hard to construct a porous Ni-P layer with favorable electron transport and gas-liquid transport. Herein, an integrated porous electrode consisting of amorphous Ni-P and a Ni interlayer was successfully constructed on a 316L stainless steel felt (denoted as Ni-P/Ni-316L). The results demonstrated that the pH of the plating solution significantly affected the grain size, pore size and distribution, and roughness of the cell-like particle surface of the amorphous Ni-P layer. The Ni-P/Ni-316L prepared at pH = 3 presented the richest surface defects or structural boundaries as well as porous structure. As expected, the as-developed Ni-P/Ni-316L demonstrated the best kinetics, with η10 of 73 mV and a Tafel slope of ca. 52 mV dec-1 for the HER among all the electrocatalysts prepared at various pH values. Furthermore, the Ni-P/Ni-316L exhibited comparable electrocatalytic HER performance and better durability than the commercial Pt (20 wt%)/C in a real water electrolysis cell, indicating that the non-precious metal-based Ni-P/Ni-316L is promising for large-scale processing and practical use.

Magnetic TiO2/CoFe2O4 Photocatalysts for Degradation of Organic Dyes and Pharmaceuticals without Oxidants

In the current study, CoFe₂O₄ and TiO₂ nanoparticles were primarily made using the sol-gel method, and subsequently, the hybrid magnetic composites of TiO₂ loaded with CoFe₂O₄ (5-15 percent w/w) were made using a hydrothermal procedure. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) were all used to thoroughly characterize the materials. Additionally, the zero-charge point (ZCP) determination, the examination of the pore structure by nitrogen adsorption, and an evaluation of magnetic properties were performed. Six organic dye pollutants were selected to evaluate the performance of the synthesized nanocomposites toward photocatalytic degradation, including methylene blue (MB), methyl orange (MO), crystal violet (CV), acridine orange (AO), rhodamine B (RhB), and rhodamine 6G (R-6G). Photodegradation of tetracycline (TL), a model pharmaceutical pollutant, was also studied under UV and visible light. The composites exhibited a high degradation performance in all cases without using any oxidants. The photocatalytic degradation of tetracycline revealed that the CoFe₂O₄/TiO₂ (5% w/w) composite exhibited a higher photocatalytic activity than either pure TiO₂ or CoFe₂O₄, and thus attained 75.31% and 50.4% degradation efficiency under UV and visible light, respectively. Trapping experiments were conducted to investigate the photodegradation mechanism, which revealed that holes and super oxide radicals were the most active species in the photodegradation process. Finally, due to the inherent magnetic attributes of the composites, their easy removal from the treated solution via a simple magnet became possible.

Photocatalytic Water Splitting Promoted by 2D and 3D Porphyrin Covalent Organic Polymers Synthesized by Suzuki-Miyaura Carbon-Carbon Coupling

This work deals with the synthesis of metal-free and porphyrin-based covalent organic polymers (COPs) by the Suzuki-Miyaura coupling carbon-carbon bond forming reaction to study the photocatalytic overall water splitting performance. Apart from using 5,10,15,20-Tetrakis-(4-bromophenyl)porphyrin, we have chosen different cross-linker monomers to induce 2-dimensional (2D) or 3-dimensional (3D) and different rigidity in their resulting polymeric molecular structure. The synthesised COPs were extensively characterised to reveal that the dimensionality and flexibility of the molecular structure play an intense role in the physical, photochemical, and electronic properties of the polymers. Photoinduced excited state of the COPs was evaluated by nanosecond time-resolved laser transient absorption spectroscopy (TAS) by analysing excited state kinetics and quenching experiments, photocurrent density measurements and photocatalytic deposition of Ru³⁺ to RuO_2, and photocatalysis. In summary, TAS experiments demonstrated that the transient excited state of these polymers has two decay kinetics and exhibit strong interaction with water molecules. Moreover, photocurrent and photocatalytic deposition experiments proved that charges are photoinduced and are found across the COP molecular network, but more important charges can migrate from the surface of the COP to the medium. Among the various COPs tested, COP-3 that has a flexible and 3D molecular structure reached the best photocatalytic performances, achieving a photocatalytic yield of 0.4 mmol H₂ × g_COP-3^-1 after 3 h irradiation.

Synthesis, Physical Properties and Electrocatalytic Performance of Nickel Phosphides for Hydrogen Evolution Reaction of Water Electrolysis

Nickel phosphides have been investigated as an alternative to noble metals and have emerged as potential catalysts that can efficiently catalyze the hydrogen evolution reaction (HER). However, the impacts of facet morphology and crystal structure of the nickel phosphides on their catalytic reactivity have not been systematically investigated. Herein, nickel phosphides with different crystalline states were prepared through a facile calcination treatment. It was found that the calcination treatment had important effects on the phase compositions, morphologies, and crystallinity of nickel phosphides, which are closely related to their HER activity. Generally, the crystallized Ni-P catalysts exhibited faster kinetics than the amorphous Ni-P. In particular, the Ni-P 300 showed remarkable HER performance with η10 of ca. 65 mV, along with a very low Tafel slope of ca. 44 mV dec^-1 due to the increased catalytically active sites. Furthermore, the Ni-P 300 exhibited negligible decay during the 140 h galvanostatic electrolysis, showing better catalytic stability than the commercial Pt/C catalyst. Compared with the amorphous Ni-P, the boosted HER activity of the Ni-P 300 could benefit from the mixed nanocrystalline Ni₂P and Ni₃P, which could contribute to the H_ads adsorption/desorption abilities and helped provide more activity sites, promoting the HER performance.

Efficient Photoinduced Thermocatalytic Chemiluminescence System Based on the Z-Scheme Heterojunction Ag3PO4/Ag/Bi4Ti3O12 for H2S Sensing

Cataluminescence as a highly efficient gas transduction principle has attracted wide attention among research in environmental monitoring and clinical diagnosis with increasing awareness of human safety. Nowadays, the development of innovation sensing systems and the construction of the sensing mechanism to improve the analytical performance of compounds remain a major challenge. Herein, we construct an advanced photoinduced thermocatalytic chemiluminescence (PI-TC-CL) gas-sensing system via the introduction of a Z-scheme heterojunction Ag₃PO₄/Ag/Bi₄Ti₃O₁₂ to achieve higher efficient detection of H₂S. The unique electron transport path of the Z-scheme heterojunction and the LSPR effect of Ag nanoparticles fascinate the generation of the photoinduced electron-hole pair on the surface of catalysts when stimulated by LED lamps and slow down the recombination of electron-hole pairs under thermal conditions. Thus, based on the cooperative effect of the Z-scheme heterojunction AgPO/Ag/BTO and PI-TC-CL system, we have successfully established an efficient H₂S CTL detection system, which has a response three times higher than that on the traditional CTL system and even 45 times higher than that on BTO and ranges among the best of the state-of-the-art CTL performance in H₂S detection with the linear range of 0.095-8.87 μg mL^-1 and a limit of detection of 0.0065 μg mL^-1. Besides, to explore the gas-sensing mechanism, the synergetic effects of photoinduction and thermal catalysis are investigated thoroughly via conductivity and electrochemical experiments. This research provides a new perspective of engineering highly efficient catalysts and ingenious sensor systems through designing the nanostructure of materials and synergism catalytic mechanism.

Recent advances in visible-light graphitic carbon nitride (g-C3N4) photocatalysts for chemical transformations

Graphitic carbon nitride (g-C3N4) has emerged as a new research hotspot, attracting broad interdisciplinary attention in the form of metal-free and visible-light-responsive photocatalysts in the field of solar energy conversion and environmental remediation. These photocatalysts have evolved as attractive candidates due to their non-toxicity, chemical stability, efficient light absorption capacity in the visible and near-infrared regions, and adaptability as a platform for the fabrication of hybrid materials. This review mainly describes the latest advances in g-C3N4 photocatalysts for chemical transformations. In addition, the typical applications of g-C3N4-based photocatalysts involving organic transformation reactions are discussed (synthesis of heterocycles, hydrosulfonylation, hydration, oxygenation, arylation, coupling reactions, etc.).

Photocatalytic hydrogen production and storage in carbon nanotubes: a first-principles study

As it is a promising clean energy source, the production and storage of hydrogen are crucial techniques. Here, based on first-principles calculations, we proposed an integral strategy for the production and storage of hydrogen in carbon nanotubes via photocatalytic processes. We considered a core–shell structure formed by placing a carbon nitride nanowire inside a carbon nanotube to achieve this goal. Photo-generated holes on the carbon nanotube surface promote water splitting. Driven by intrinsic electrostatic field in the core–shell structures, protons produced by water splitting penetrate the carbon nanotube and react with photo-generated electrons on the carbon nitride nanowire to produce hydrogen molecules in the carbon nanotube. Because carbon nanotubes have high hydrogen storage capacity, this core–shell structure can serve as a candidate system for photocatalytic water splitting and safe hydrogen storage.

The production and storage of hydrogen in CNNW/CNT core–shell structures via photocatalytic processes.

Enhanced photocatalytic H2 evolution over covalent organic frameworks through an assembled NiS cocatalyst

Covalent organic frameworks (COFs) have been investigated in the field of photocatalysts for H₂ evolution because of their crystalline structure and diversity. However, most of them need the help of noble metals as co-catalysts to realize a high hydrogen evolution. Herein, we chose typical COFs as a platform and constructed NiSX-BD (X: weight fraction of NiS) composites by assembling NiS at room temperature. The NiS nanoparticles are shown to tightly adhere to the COFs surface. Under visible light irradiation (wavelength > 420 nm), the optimized sample with 3 wt% NiS loading exhibits a photocatalytic H₂ evolution rate of 38.4 μmol h⁻¹ (3840 μmol h⁻¹ g⁻¹), which is about 120 folds higher than that of the pure TpBD-COF and better than TpBD-COF/Pt with the same Pt loading (3 wt%). NiS3-BD shows stable hydrogen evolution in at least six consecutive cycle tests totaling 18 h. Further investigation reveals that the loaded NiS can facilitate the transfer of photogenerated electrons from TpBD-COF to the co-catalyst, leading to efficient and high photocatalytic activity. Combining the significant feature of COFs, this study opens up a feasible avenue to boost the photocatalytic H₂ performance by constructing the synergetic effects between COFs and cost-effective material.

We constructed a novel hybrid photocatalyst by assembling NiS through a milder method. Under visible light irradiation, controlled NiS/TpBD-COF composites can readily optimize photocatalytic performances without a noble cocatalyst.

Robust photocatalytic activity of two-dimensional h-BN/Bi2O3 heterostructure quantum sheets

Herein, defect intrinsic hexagonal boron nitride (h-BN) quantum sheets (QS) and bismuth oxide (Bi₂O₃) QS were prepared from bulk materials by ball milling and solvent stripping, respectively. The h-BN/Bi₂O₃ heterostructure was fabricated via a facile self-assembly method. The structure and performance of samples were systematically characterized. As expected, the layered h-BN QS is tightly coated on the surface of Bi₂O₃ QS in a face-to-face stacking structure and interconnected by strong interface interactions. The introduction of h-BN QS can significantly enhance the separation efficiency of the photogenerated carriers of h-BN/Bi₂O₃. The experimental results show that the photocatalytic activity of h-BN/Bi₂O₃ is markedly improved. The first-order reaction rate constant of the 3wt%-BN/Bi₂O₃ sample is 3.2 × 10^-2 min^-1, about 4.5 times that of Bi₂O₃ QS. By means of the active species capture test, it is found that the main oxidation species are holes (h⁺), followed by hydroxyl radicals (˙OH). Based on the surface charge transfer characteristics, the photogenerated carrier transfer and separation efficiency can be improved by coupling h-BN and a Bi₂O₃ semiconductor to the Schottky heterojunction, and the strong interaction between heterogeneous interfaces also enhances the surface catalytic reaction efficiency, which improves dramatically the photocatalytic performance.

Interior and Surface Synergistic Modifications Modulate the SnNb2O6/Ni-Doped ZnIn2S4 S-Scheme Heterojunction for Efficient Photocatalytic H2 Evolution

Interior and surface synergistic modifications can endow the photocatalytic reaction with tuned photogenerated carrier flow at the atomic level. Herein, a new class of 2D/2D SnNb₂O₆/Ni-doped ZnIn₂S₄ (SNO/Ni-ZIS) S-scheme heterojunctions is synthesized by a simple hydrothermal strategy, which was used to evaluate the synergy between interior and surface modifications. Theoretical calculations show that the S-scheme heterojunction boosts the desorption of H atoms for rapid H₂ evolution. As a result, 25% SNO/Ni_0.4-ZIS exhibits significantly improved PHE activity under visible light, roughly 4.49 and 2.00 times stronger than that of single ZIS and Ni_0.4-ZIS, respectively. In addition, 25% SNO/Ni_0.4-ZIS also shows superior structural stability. This work provides advanced insight for developing high-performance S-scheme systems from photocatalyst design to mechanistic insight.

Low-cost synthesis of a nanocomposite of MoS2 and alkali-activated halloysite nanotubes for photocatalytic RhB degradation

A novel nanocomposite of ultrathin MoS2 nanosheets/alkali-activated halloysite was fabricated via a hydrothermal method, which exhibited improved photocatalytic degradation of rhodamine B compared with the MoS2/HNTs and pristine MoS2.

Synthesis of a UiO-66/g-C3N4 composite using terephthalic acid obtained from waste plastic for the photocatalytic degradation of the chemical warfare agent simulant, methyl paraoxon

In our study, Zr-based UiO-66 (Zr) was synthesized using terephthalic acid obtained from waste plastic. Thereafter, UiO-66/g-C₃N₄ composites were prepared by the solvothermal method, and their photocatalytic activity in the photodegradation of the chemical warfare agent simulant, dimethyl 4-nitrophenyl phosphate (DMNP), was evaluated. The as-synthesized UiO-66/g-C₃N₄ exhibited a high surface area (1440 m² g⁻¹) and a high capillary volume (1.49 cm³ g⁻¹). The UiO-66/g-C₃N₄ samples absorbed a visible light band with bandgap energies of 2.13–2.88 eV. The as-synthesized UiO-66/g-C₃N₄ composites exhibited highly efficient degradation of DMNP with a short half-life (t_1/2 of 2.17 min) at pH 7 under visible light irradiation. The trapping experiments confirmed that the h⁺ and ˙O₂⁻ radicals played an important role in the photocatalytic degradation of DMNP. The UiO-66/g-C₃N₄ catalyst simultaneously performed two processes: the hydrolysis and photocatalytic oxidation of DMNP in water. During irradiation, a p–n heterojunction between UiO-66 and g-C₃N₄ restricted the recombination of photogenerated electrons and holes, resulting in the enhancement in the degradation rate of DMNP.

UiO-66/g-C₃N₄ with a high surface area (1440 m² g⁻¹) and a high capillary volume (1.49 cm³ g⁻¹) exhibited highly efficient degradation of dimethyl 4-nitrophenyl phosphate with t_1/2 = 2.17 min.

EDOT-based conjugated polymers accessed via C–H direct arylation for efficient photocatalytic hydrogen production

3,4-ethylene dioxythiophene (EDOT), as a monomer of commercial conductive poly(3,4-ethylene dioxythiophene) (PEDOT), has been facilely incorporated into a series of new π-conjugated polymer-based photocatalysts, i.e., BSO2-EDOT, DBT-EDOT, Py-EDOT and DFB-EDOT,...

Remarkably Improved Water Splitting Photocatalytic Performance of Crystalline TiO2 Nanobelts Hydrogenated at Atmospheric Pressure with the Assistance of Hydrogen Spillover

The unusual photocatalytic performance of hydrogenated black TiO2 has aroused worldwide interest. However, hydrogena-tion of well-crystallized TiO2 is always thought to be difficult even at rigorous conditions. In present work,...