Photocatalytic Reaction Pathway Research Articles

Structurally Locked High-Crystalline Covalent Triazine Frameworks Enable Remarkable Overall Photosynthesis of Hydrogen Peroxide.

The development of green and efficient hydrogen peroxide (H2O2) production is of great interest but remains challenging. Herein, we develop a new and simple strategy via locking the coplanarity in highly crystalline covalent triazine frameworks (CTFs) to remarkably boost direct photosynthesis of H2O2 from oxygen and water. The exfoliated ultrathin 2D-CTF nanosheets exhibit excellent photocatalytic H2O2 evolution with an ultrahigh solar-to-chemical efficiency of 0.91% and a superb apparent quantum yield of 16.8% at 420 nm, surpassing all previous CTFs and most of the metal-free photocatalysts ever reported. Our detailed experimental and theoretical studies reveal that the spatially locked structure in the crystalline CTF photocatalyst can not only greatly enhance the separation and transfer of photoexcited charge-carriers for promoting H2O2 photogeneration but also alter the local electronic structures that unexpectedly turn water oxidation from a four-electron route to a two-electron pathway, resulting in a 100% atom utilization efficiency. This work provides valuable insights into the designed synthesis of highly efficient metal-free photocatalysts and precise control over photocatalytic reaction pathways in organic materials.

Rational design of S‒scheme Cd0.5Zn0.5S/CeO2 heterojunction for enhanced photooxidation of antibiotics and photoreduction of Cr(VI)

Current photocatalysts endowed with oxidation and reduction capabilities for pharmaceuticals and heavy metals removal face numerous challenges, such as a lack of sufficient reactive sites, poor electron-hole separation, and limited oxidation and reduction capabilities. In this study, we aimed to overcome these limitations by employing a simple solvothermal method to fabricate a novel S-scheme heterojunction, Cd0.5Zn0.5S/CeO2. The optimal Cd₀.₅Zn₀.₅S/CeO2 heterojunction achieved a maximum ciprofloxacin degradation efficiency of 86 % within 30 min, showing a remarkable improvement of 2.4 and 4.6 times compared to pristine Cd₀.₅Zn₀.₅S and CeO2, respectively. The heterojunction also demonstrated a remarkable 100 % photoreduction efficiency of Cr(VI) within 30 min, which is double the photodegradation performance of the individual materials. The combination of Cd₀.₅Zn₀.₅S with CeO2 to form the Cd₀.₅Zn₀.₅S/CeO2 S-scheme heterojunction effectively enhanced spatial photo-carrier separation and optimized the photo-redox capability, resulting in a substantial improvement in photocatalytic performance and stability. Through radical trapping experiments, the primary reactive species responsible for CIP degradation were identified as h⁺, OH•, and •O₂⁻. Additionally, e⁻ was determined to be the key species responsible for the photoreduction of Cr(VI). Based on these findings, we proposed a plausible photocatalytic reaction pathway for the simultaneous elimination of both CIP and Cr(VI). This study underscores the significant potential of the Cd0.5Zn0.5S/CeO2 S-scheme heterojunction for advanced wastewater treatment applications, highlighting its innovative approach and superior performance.

Pyrene‐Alkyne‐Based Conjugated Porous Polymers with Skeleton Distortion‐Mediated ⋅O2− and 1O2 Generation for High‐Selectivity Organic Photosynthesis

AbstractReactive oxygen species (ROS) play a crucial role in determining photocatalytic reaction pathways, intermediate species, and product selectivity. However, research on ROS regulation in polymer photocatalysts is still in its early stages. Herein, we successfully achieved series of modulations to the skeleton of Pyrene‐alkyne‐based (Tetraethynylpyrene (TEPY)) conjugated porous polymers (CPPs) by altering the linkers (1,4‐dibromobenzene (BE), 4,4′‐dibromobiphenyl (IP), and 3,3′‐dibromobiphenyl (BP)). Experiments combined with theoretical calculations indicate that BE‐TEPY exhibits a planar structure with minimal exciton binding energy, which favors exciton dissociation followed by charge transfer with adsorbed O2 to produce ⋅O2−. Thus BE‐TEPY shows optimal photocatalytic activity for phenylboronic acid oxidation and [3+2] cycloaddition. Conversely, the skeleton of BP‐TEPY is significantly distorted. Its planar conjugation decreases, intersystem crossing (ISC) efficiency increases, which makes it more prone for resonance energy transfer to generate 1O2. Therefore, BP‐TEPY displays best photocatalytic activity in [4+2] cycloaddition and thioanisole oxidation. Both above reactant conversion and its product selectivity exceed 99 %. This work systematically reveals the intrinsic structure–activity relationship among the skeleton structure of CPPs, excitonic behavior, and selective generation of ROS, providing new insights for the rational design of highly efficient and selective CPPs photocatalysts.

Pyrene-Alkyne-Based Conjugated Porous Polymers with Skeleton Distortion-Mediated ⋅O2 - and 1O2 Generation for High-Selectivity Organic Photosynthesis.

Reactive oxygen species (ROS) play a crucial role in determining photocatalytic reaction pathways, intermediate species, and product selectivity. However, research on ROS regulation in polymer photocatalysts is still in its early stages. Herein, we successfully achieved series of modulations to the skeleton of Pyrene-alkyne-based (Tetraethynylpyrene (TEPY)) conjugated porous polymers (CPPs) by altering the linkers (1,4-dibromobenzene (BE), 4,4'-dibromobiphenyl (IP), and 3,3'-dibromobiphenyl (BP)). Experiments combined with theoretical calculations indicate that BE-TEPY exhibits a planar structure with minimal exciton binding energy, which favors exciton dissociation followed by charge transfer with adsorbed O2 to produce ⋅O2 -. Thus BE-TEPY shows optimal photocatalytic activity for phenylboronic acid oxidation and [3+2] cycloaddition. Conversely, the skeleton of BP-TEPY is significantly distorted. Its planar conjugation decreases, intersystem crossing (ISC) efficiency increases, which makes it more prone for resonance energy transfer to generate 1O2. Therefore, BP-TEPY displays best photocatalytic activity in [4+2] cycloaddition and thioanisole oxidation. Both above reactant conversion and its product selectivity exceed 99 %. This work systematically reveals the intrinsic structure-activity relationship among the skeleton structure of CPPs, excitonic behavior, and selective generation of ROS, providing new insights for the rational design of highly efficient and selective CPPs photocatalysts.

Photocatalytic reaction pathways and mechanisms investigation for effective organic pollution degradation via in-situ construction of BiOCl/UiO66-NH2 heterostructure

Constructing heterostructured photocatalysts is a desirable strategy for the enhanced degradation performance of pollutants from wastewater. In this work, BiOCl/UiO66-NH2 photocatalysts were constructed by in-situ solvothermal method. The composites presented enhanced photocatalytic activity for the degradation of Ciprofloxacin (CIP), Tetracycline hydrochloride (TC) and Rhodamine B (RhB) under simulated sunlight. The formation of the porous structure via the introduction of UiO66-NH2 not only enhances the adsorption ability of the catalyst but also promotes light harvesting, which enables the samples to exhibit high photocatalytic performance. In addition, the probable photodegradation pathways and mechanisms were studied in detail. This work provides an effective route for removing various pollutants in wastewater with heterojunction photocatalysts.

Ball Milling of La2O3 Tailors the Crystal Structure, Reactive Oxygen Species, and Free Radical and Non-Free Radical Photocatalytic Pathways.

Non-free radical photocatalysis with metal oxide catalysts is an important advanced oxidation process that enables the removal of various emerging environmental pollutants, such as tetracycline. Here, four hexagonal La2O3 photocatalysts with different densities of oxygen vacancy and crystalline features are synthesized and then further treated by ball milling. Ball milling of these La2O3 photocatalysts is found to increase the amount of oxygen vacancies on their surfaces and thereby the amount of 1O2 species produced by them. The photocatalytic degradation of TC by these La2O3 photocatalysts depends on the oxygen vacancies present on them. Furthermore, the ones with a strong (101) diffraction peak remove tetracycline from water systems largely with 1O2 and •OH species, whereas those with a weak (101) diffraction peak do so mainly via 1O2 and direct electron transfer (DET) process. Their overall catalytic properties are also studied by density functional theory calculations. Moreover, the organic products produced from tetracycline by La2O3 photocatalysts containing a strong (101) diffraction peak are found to be less toxic than those produced by La2O3 photocatalysts containing a weak (101) diffraction peak. This study also provides convincing evidence that the structures of La2O3 determine the species that is produced by it and that end up mediating photocatalytic reaction pathways (i.e., free radical versus non-free radical) to degrade an emerging environment pollutant.

A highly stable TiO2/covalent organic framework heterojunction photocatalyst boosting charge transfer for visible-light-driven CO2 reduction

In this study, we present a novel heterojunction photocatalyst (TiO2-TTCOF) boosting charge transfer for visible-light-driven CO2 to CO conversion without photosensitizer or sacrificial agents. The 10% TiO2-TTCOF heterojunction photocatalyst is able to catalyze CO2 conversion, resulting in a highest CO production rate of 139.1 μmol g−1 with a selectivity of 96% and O2 production rate of 73.1 μmol g−1. Additionally, time-resolved fluorescence decay spectra confirmed the heterostructure between TTCOF and TiO2 can promote photoelectron transfer. The ATR-IFTS spectra indicated the photocatalytic reaction pathway.

In Situ Multicolor Imaging of Photocatalytic Degradation Process of Permanganate on Single Bismuth-Based Metal-Organic Frameworks.

Bismuth-based metal-organic frameworks (Bi-MOFs) have emerged as important photocatalysts for pollutant degradation applications. Understanding the photocatalytic degradation mechanism is key to achieving technological advantage. Herein, we apply dark-field optical microscopy (DFM) to realize in situ multicolor imaging of the photocatalytic degradation process of permanganate (MnO4-) on single CAU-17 Bi-MOFs. Three reaction kinetic processes such as surface adsorption, photocatalytic reduction, and disproportionation are revealed by combining the time-lapsed DFM images with optical absorption spectra, indicating that the photocatalytic reduction of purple MnO4- first produces beige red MnO42- through a one-electron pathway, and then MnO42- disproportionates into yellow MnO2 on CAU-17. Meanwhile, we observe that the deposition of MnO2 cocatalysts enhances the surface adsorption reaction and the photocatalytic reduction of MnO4- to MnO42-. Unexpectedly, it is found that isopropanol as a typical hole scavenger can stabilize MnO42-, avoiding disproportionation and causing the alteration of the photocatalytic reaction pathway from a one-electron avenue to a three-electron (1 + 2) process for producing MnO2 on CAU-17. This research opens up the possibility of comprehensively tracking and understanding the photocatalytic degradation reaction at the single MOF particle level.

Versatile polydopamine-mediated growth of N and C co-doped hollow porous TiO2 spheres with oxygen vacancies for visible-light-driven oxidation of acetaldehyde

Developing visible-light-responsive TiO2-based photocatalysts provides a promising avenue for addressing VOCs pollution. Herein, polydopamine (PDA) template pyrolysis waste was in-situ up-cycled for simultaneous growth of N and C co-doped hollow porous TiO2 microreactors (H-NT-0.2) in air. The resulting H-NT-0.2 with a highly intact hollow structure, thin spherical shell (∼ 13 nm) and high porosity possesses the highest N and C co-doping ratio and largest oxygen vacancies (OVs) amount, leading to the highest concentration of reactive oxygen species (ROS) among all H-NT-x. A crucial role of OVs in enhancing H2O adsorption for the generation of hydroxyl radicals (⋅OH) has been revealed by DFT calculations. As a result, H-NT-0.2 shows the highest photocatalytic oxidation (PCO) efficiency of flowing acetaldehyde gas (90%) under visible light irradiation, which exceeds 3.5 times of commercial TiO2 (P25)), and outperforms most of the reported photocatalysts. The growth mechanism, as well as the photocatalytic reaction pathways, were analyzed based on TG-MS and in-situ DRIFTS results, respectively. This work provides an economical, green and feasible strategy to develop advanced visible-light-responsive photocatalysts for aldehydes VOCs abatement in practical applications.

Polyoxometalate-based hybrid materials with electronic interaction boosting photocatalytic H2 evolution coupled with alcohol oxidation

Efficient separation of the mixed H2 and O2 products is a crucial step in the photocatalytic overall water splitting process, often hindered by the slow kinetics of the O2-producing half-reaction. One effective approach is to employ organic substrates that can capture the holes, thereby enhancing the overall reaction rate and yielding valuable alcohol oxidation products in parallel. Enhance electronic structure advantages through electrostatic interactions and intermolecular hydrogen bonding, thereby facilitating accelerated electron transfer and boosting the intrinsic photocatalytic activity. This is the first study that demonstrates the successful implementation of Ru oxo cluster-based hybrid materials with electronic interaction and intermolecular hydrogen bonding, NaH[Ru(bpy)3][Ru8(CO3)4(CO)16Cl4]·EtOH·5H2O. The triethanolamine sacrificial reaction system has a remarkable 15-fold increase in H2 evolution, alongside concurrent H2 production coupled with 1-(4-chlorophenyl)ethanol oxidation reactions (with a selectivity of 99 %). This observed enhancement is three times higher (HER = 1.60 mmol⋅g−1⋅h−1) than a discrete catalyst NaH2(TPA)[Ru8(CO3)4(CO)16Cl4]·EtOH·5H2O (HER = 0.48 mmol⋅g−1⋅h−1). Activity contrast experiments were conducted to gain insights into the photocatalytic reaction pathways, enabling the proposal of potential mechanisms that further elucidate the process. This research presents a significant expansion in the realm of designing and developing novel multifunctional artificial photocatalysts based on polyoxometalate (POMs) with enhanced electronic interactions. These advancements open up exciting possibilities for diverse economic and ecological photoredox applications.

Visible‐light‐driven photocatalytic degradation of antibiotics by newly molding g‐C3N4/graphitized biochar composites

AbstractNewly molding g‐C3N4/graphitized biochar (g‐C3N4/GSBC) molding composites photocatalytic material with superior photocatalytic activity were successfully synthesized by the impregnation‐roasting process. The photocatalytic behavior of g‐C3N4/GSBC was assessed in the photocatalytic degradation of antibiotic pollutants, including sulfamethoxazole(SMZ), ciprofloxacin(CIP), and tetracycline(TC), under visible light illumination. The successful composited of g‐C3N4 with GSBC was demonstrated by various characterization results, in which the 5 : 1 mass loading ratio showed the best performance. g‐C3N4/GSBC possessed a larger specific surface area (71.09 m2/g), suitable band gap (2.66 eV), more catalytically active species, and higher utilization efficiency of visible light than powdered g‐C3N4. The removal efficiency of the new composite was higher than that of g‐C3N4 for the three antibiotics, with removal efficiencies of 87.2 %, 83.2 %, and 72.2 % for SMZ, TC, and CIP, respectively. The analysis of its photodegradation mechanism revealed that h+ and ⋅O2− are responsible for the antibiotics′ decomposition. According to the HPLC‐MS results, the possible photocatalytic mechanism and reaction pathways have been proposed. This work provided a new way for the synthesis of molding photocatalysts as an efficient photocatalyst for the degradation of organic contaminants.

Exposed Zinc Sites on Hybrid ZnIn2S4@CdS Nanocages for Efficient Regioselective Photocatalytic Epoxide Alcoholysis

AbstractPhotocatalytic epoxide alcoholysis through C−O bond cleavage and formation has emerged as an alternative to synthesizing anti‐tumoral pharmaceuticals and fine chemicals. However, the lack of crucial evidence to interpret the interaction between reactants and photocatalyst surface makes it challenging for photocatalytic epoxide alcoholysis with both high activity and regioselectivity. In this work, we report the hierarchical ZnIn2S4@CdS photocatalyst for epoxide alcoholysis with high regioselectivity nearly 100 %. Mechanistic studies unveil that the precise activation switch on exposed Zn acid sites for C−O bond polarization and cleavage has a critical significance for achieving efficient photocatalytic performance. Furthermore, the establishment of Z‐scheme heterojunction facilitates the interface charge separation and transfer. Remarkably, the underlying regioselective photocatalytic reaction pathway has been distinctly revealed.

Exposed Zinc Sites on Hybrid ZnIn2 S4 @CdS Nanocages for Efficient Regioselective Photocatalytic Epoxide Alcoholysis.

Photocatalytic epoxide alcoholysis through C-O bond cleavage and formation has emerged as an alternative to synthesizing anti-tumoral pharmaceuticals and fine chemicals. However, the lack of crucial evidence to interpret the interaction between reactants and photocatalyst surface makes it challenging for photocatalytic epoxide alcoholysis with both high activity and regioselectivity. In this work, we report the hierarchical ZnIn2 S4 @CdS photocatalyst for epoxide alcoholysis with high regioselectivity nearly 100 %. Mechanistic studies unveil that the precise activation switch on exposed Zn acid sites for C-O bond polarization and cleavage has a critical significance for achieving efficient photocatalytic performance. Furthermore, the establishment of Z-scheme heterojunction facilitates the interface charge separation and transfer. Remarkably, the underlying regioselective photocatalytic reaction pathway has been distinctly revealed.

Switching Type I/Type II Reactions by Turning a Photoredox Catalyst into a Photo-Driven Artificial Metalloenzyme

While photocatalysts have been recognized as powerful and environmentally friendly catalysts, harnessing their reactivity still remains challenging. On account of the distinctive reaction compartment that their protein scaffolds provide for the incorporated metal complex, artificial metalloenzymes (ArMs) can improve catalytic reaction rates and stereochemical selectivity. In the present study, we have developed a photo-driven ArM by incorporating a DNA photo-switch metal complex, [Ru(bpy)2dppz]2+ (1), into an apo-form riboflavin-binding protein (RFBP). We report that two potentially competing photocatalytic reaction pathways, i.e., a photoredox reaction and an energy transfer reaction, can be switched by 1 alone and by the ArM. This reaction switching was exploited in selective protein labeling; 1 alone preferentially promotes tyrosine modification, while the ArM promotes histidine modification. The present study thus opens the door for the potential use of ArMs to control the reactivity of photocatalysts.

Photocatalytic degradation of Congo red dye using zinc oxide nanoparticles prepared using Carica papaya leaf extract

In this research, the photocatalytic degradation of Congo red (CR) dye was investigated using hexagonal wurtzite structured zinc (Zn) oxide nanoparticles (ZnO NPs: crystallite size of ∼21 nm and band gap energy of 2.88 eV) prepared through the reduction of a Zn salt using Carica (C.) papaya leaf extract. The Fourier transform infrared (FTIR) spectra revealed the presence of several organic moieties (supplied by the C. papaya leaf extract) on the ZnO surface. High-resolution transmission electron microscope (HRTEM) images showed non-agglomerated and multi-structured (e.g., spherical, semi-spherical, hexagonal, and rod-like) ZnO NPs. The BET analysis indicated the mesoporous structure of ZnO NPs with a high specific surface area of 34 m2/g. The ZnO NPs showed 99.9% degradation of CR dye (120 mg L−1) within 80 min under ultraviolet (UV) irradiation. The ZnO NPs exhibited excellent photocatalytic performance (e.g., quantum yield: 3.18 × 10−4Φ, kinetic reaction rate: 1.43 × 10+3 μmol g−1 h−1, space time yield: 3.18 × 10−5 molecules photon−1 mg−1, and figure-of-merit: 5.53 × 10−9 mol L J−1 g−1 h−1) with a minimum energy consumption of 3.26 × 1022 J mol−1 in comparison to other photocatalytic systems. The photocatalytic reaction pathways of CR dyes are addressed, along with a discussion on its degradation products based on gas chromatography-mass spectrometry (GC-MS) analysis. The overall results of this research indicate that C. papaya-mediated ZnO NPs can be used as an effective option for the degradation of industrial dyes.

Visible-light driven p-n heterojunction formed between α-Bi2O3 and Bi2O2CO3 for efficient photocatalytic degradation of tetracycline.

To improve the efficiency of photocatalytic oxidative degradation of antibiotic pollutants, it is essential to develop an efficient and stable photocatalyst. In this study, a polymer-assisted facile synthesis strategy is proposed for the polymorph-controlled α-Bi2O3/Bi2O2CO3 heterojunction retained at elevated calcination temperatures. The p-n heterojunction can effectively separate and migrate electron-hole pairs, which improves visible-light-driven photocatalytic degradation from tetracycline (TC). The BO-400@PAN-140 photocatalyst achieves the highest pollutant removal efficiency of 98.21% for photocatalytic tetracycline degradation in 1 h (λ > 420 nm), and the degradation efficiency was maintained above 95% after 5 cycles. The morphology, crystal structure, and chemical state of the composites were analysed by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Ultraviolet-visible diffuse reflection, transient photocurrent response, and electrochemical impedance spectroscopy were adopted to identify the charge transfer and separation efficiency of photogenerated electron-hole pairs. The EPR results verified h+ and ˙OH radicals as the primary active species in the photocatalytic oxidation reactions. This observation was also consistent with the results of radical trapping experiments. In addition, the key intermediate products of the photocatalytic degradation of TC over BO-400@PAN-140 were identified via high-performance liquid chromatography-mass spectrometry, which is compatible with two possible photocatalytic reaction pathways. This work provides instructive guidelines for designing heterojunction photocatalysts via a polymer-assisted semiconductor crystallographic transition pathway for TC degradation into cleaner production.

Light‐Emitting Diode Visible‐Light‐Driven Photocatalytic Redox Reactions in Nitrogen Oxide Removal Using β‐Bi2O3/Bi/g‐C3N4 Prepared by One‐Step In Situ Thermal Reduction Synthesis

Traditional photocatalytic oxidation of nitrogen oxide (NO) may cause the more toxic NO2 generation after longtime reaction, and even the ideal final production nitrate may also inevitably cause the poisoning of photocatalysts. Thus, utilizing photocatalytic reduction to remove NO into N2 should be considered more practical but is still challenging currently. Herein, a novel S‐scheme β‐Bi2O3/Bi/g‐C3N4 heterojunction photocatalyst is developed via a one‐step in situ thermal reduction method. The photocatalytic degradation efficiency over this S‐scheme photocatalyst exhibits around 88.7% degradation rate for NO with little NO2 generation under light‐emitting diode light irradiation, which is significantly higher than that of the pristine g‐C3N4 (60%). Interestingly, both reduction of NO into N2 and oxidation of NO into NO3− exist synchronously in the system. The increased degradation efficiency and the efficient reduction pathway occurring should be ascribed to the enhanced generation, separation, and transfer of the photogenerated carriers through the Bi‐bridge S‐scheme heterojunction. This study has provided a new route for regulating the photocatalytic reaction pathway for NO removal through a simple synthesis method.

Honeycomb-like porous carbon loaded with CdS/ZnS heterojunction with enhanced photocatalytic performance towards tetracycline degradation and H2 generation

Accelerating the charge separation efficiency is a crucial approach to improve the photocatalytic performance of semiconductors. The design and synthesis of heterojunctions can effectively inhibit the recombination of photogenerated electron-hole pairs and enhance the charge separation efficiency. In this work, an easy-handling calcination route was proposed to prepare CdS/ZnS heterojunction loaded on honeycomb-like porous carbon (CZS@C) using chitosan as a precursor. The unique honeycomb-like porous structure facilitated the separation and migration of photoexcited electrons and holes, improving the utilization of visible light and shortening the distance of electron transport. The photocatalytic performance of CZS@C was evaluated by the degradation of tetracycline (TC) and H2 production from water splitting under visible light. The optimized CZS@C composite can degrade almost 92.40 % of TC under visible light irradiation in 60 min. Such CZS@C composite presented an excellent photocatalytic activity with H2 production rate of 5.49 mmol h−1 g−1, which was 54.9 and 2.28-folds higher than ZnS@C and CdS@C. Furthermore, the possible photocatalytic reaction mechanism and pathway towards TC degradation and simultaneous H2 generation was proposed.

Selective solar-driven CO2 reduction mediated by 2D/2D Bi2O2SiO3/MXene nanosheets heterojunction

• An ecofriendly 2D/2D heterojunction of Bi 2 O 2 SiO 3 /Ti 3 C 2 was synthesized by a simple wet chemical process. • 2D/2D Bi 2 O 2 SiO 3 /Ti 3 C 2 heterojunction boosts the photo-reactivity of Bi 2 O 2 SiO 3 for CO 2 reduction. • The 2D/2D heterojunction own a short charge transfer distance resulting in effective charge transfer. • The enhanced photocatalytic mechanism of the system was clarified by DFT study. Photocatalytic CO 2 reduction reaction (CO 2 RR) is an environment-friendly technique for clean fuel generation. Developing low-cost and efficient photocatalyst/cocatalyst systems for boosting CO 2 RR is still a challenge. Herein, a novel Bi 2 O 2 SiO 3 /Ti 3 C 2 2D/2D heterojunction photocatalysts are successfully prepared by in situ growth of Bi 2 O 2 SiO 3 on the surface of ultrathin Ti 3 C 2 nanosheets, a kind of MXenes. The observed Bi 2 O 2 SiO 3 /Ti 3 C 2 (BOSO/TC-2) hybrids exhibit a large interface contact area companied with enhanced CO 2 adsorption capability, illustrating excellent 2D/2D interfacial charge transfer behaviors. The total yield of products obtained on the optimized BOSO/TC-2 photocatalyst is 3.8 times that of pristine Bi 2 O 2 SiO 3 nanosheets and achieve near 90% selectivity for CO over CH 3 OH without sacrificial agents, which was higher than most all inorganic Bi-based photocatalysts. Moreover, the mechanism of enhanced photocatalytic activity and reaction pathway was proposed in terms of the DFT study and in situ FTIR analysis. This work might provide new semiconductor/cocatalyst systems for selective CO 2 photoreduction to solar fuels.

Core-shell structured Z-scheme Ag2S/AgIO3 composites for photocatalytic organic pollutants degradation

Constructing direct Z-scheme system is a promising strategy to boost the photocatalytic performance for pollution waters restoration, but it is of great challenge because of the requirement of appropriately staggered energy band alignment and intimate interfacial interaction between semiconductors. Herein, a class of core-shell structured Ag2S–AgIO3 Z-scheme heterostructure photocatalysts are designed and developed. Ag2S is generated by the in-situ ion exchange reaction and anchored on the surface of AgIO3, so the intimate interface between AgIO3 and Ag2S is realized. Integration of AgIO3 and Ag2S extends the ultraviolet absorption of AgIO3 to Vis-NIR region, and also promote the charge separation and migration efficiency, contributing to the enhanced photocatalysis activity for composite catalysts. The optimal Ag2S–AgIO4-4 catalyst exhibits a MO photo-degradation rate constant of 0.298 h−1, which reaches 5.77 and 11.4-folds higher than that of AgIO3 (0.044 h−1) and Ag2S (0.024 h−1). The as-obtained composite catalyst exhibits universally photocatalytic activity in disintegrating diverse industrial pollutants and pharmaceuticals. Particularly, driven by natural sunlight, the Ag2S–AgIO4-4 can effectively decompose MO. A plausible Z-scheme photocatalytic mechanism and reaction pathways of MO degradation over composite catalyst are systemically investigated and proposed.