Transfer Of Photogenerated Electrons Research Articles

Construct organic/inorganic heterojunction photocatalyst of benzene-ring-grafted g-C3N4/CdSe for photocatalytic H2 evolution

Photocatalytic water splitting to produce hydrogen is a vital research direction for alleviating the energy crisis. Herein, benzene-ring grafted g-C3N4 nanotubes (Ph-g-C3N4) were prepared skillfully and coupled with CdSe nanoparticles which was realized efficiently hydrogen production. The addition of CdSe nanoparticles enhanced the stability of the catalytic system dispersion in water, and the absorbance of the composites catalyst CdSe/Ph-g-C3N4 (CPG) was enhanced. In addition, the CPG had been characterized to have low resistance and efficient photogenerated electron separation efficiency. The Ph-g-C3N4 nanotubes with a three-dimensional structure can provide an anchoring platform for CdSe nanoparticles and effectively prevent the agglomeration of CdSe. The constructed composites catalyst achieved the efficient transfer of photogenerated electrons as known from photoluminescence spectroscopy test analysis. When CdSe nanoparticles were anchored to Ph-g-C3N4, the electron transfer rate of the constructed composite was about twice that of the Ph-g-C3N4, which facilitates the hydrogen evolution reaction. The character and electron transfer pathways of the photocatalysts were investigated theoretically by performing density functional calculations. The finding provides a new idea for the doping of photocatalysts and the design of organic/inorganic heterojunction composites photocatalyst to achieve an efficient hydrogen production system.

Single-atom Nb anchored on graphitic carbon nitride for boosting electron transfer towards improved photocatalytic performance

Single-atom Nb anchored on g-C3N4 was prepared by facile thermal polymerization. Compared with pure g-C3N4, optimized Nb-anchoring samples exhibited excellent CO and CH4 yield and higher photocatalytic oxidation efficiency in degrading amoxicillin (AMX). Combining DFT calculations and experimental results, the enhanced photocatalytic performance was attributed to anchored single-atom Nb in terms of Nb-C and the formation of N defects. Anchoring with single-atom Nb contributed to the formation of N defects in g-C3N4, inducing the formation of polarized Nb-C bonds with high conductivity accelerating the directional transfer of photogenerated electrons and holes. Moreover, this restrained the relatively high charge carrier recombination rate of g-C3N4. Additionally, N defects with solitary electrons could enhance the charge density and serve as active centers for a photocatalytic reaction. The present work underlines the importance of the synergistic effect of anchoring Nb and simultaneously generating N defects for developing a new generation of g-C3N4-based photocatalysts.

Efficient dye degradation and concurrent electricity generation using silver bromide-embedded titanium dioxide

Removal of dissolved organic matters, like dyes, from industrial wastewater is challenging due to complexity with their exceptional stability and ability to pass through filters. In this study, we have synthesized silver bromide nanoparticles-embedded polycrystalline titania (AgBr-x/TiO2) by a simple one-pot synthesis route. The degradation of reactive green dye with simultaneous electrical energy generation is demonstrated with developed AgBr-x/TiO2 photo-anodes. The structural and morphological analyses reveal that the fine AgBr nanocrystals are embedded in submicron sized TiO2 particles. The composite particles with various AgBr compositions were synthesized. The embedded-structure gives better heterojunction between AgBr and TiO2, and facilitates the transfer of photogenerated electrons compared to simple mixture. The visible light absorption of the composite was monotonically increased with AgBr composition. A flat optical absorption profile was obtained at 50% AgBr composition. The developed AgBr-x/TiO2 photo-anode shows the initial rate of dye degradation four-fold higher than the commercial grade TiO2 nanoparticles, where the generated power was 2.6 times high. The degradation by-product contains water-insoluble sludge which has the similar optical absorption profile of feed water. It is observed that the dye removal is predominantly through decolourization and coagulation. Conclusively, the developed AgBr-x/TiO2 photo-anode could realize a self-sustained wastewater treatment unit where the required electricity is produced by dye degradation.

Novel graphene quantum dots modified NH2-MIL-125 photocatalytic composites for effective antibacterial property and mechanism insight

Bacterial infection threatens human health, so the design of efficient and stable photocatalytic antibacterial materials has attracted widespread attention. In this regard, a novel photocatalyst GQDs/NH2-MIL-125 (GQDs: graphene quantum dots) was prepared by the solvothermal method for photocatalytic disinfection. Since the addition of GQDs enhanced the absorption of visible light and also accelerated the transfer of photogenerated electrons, the photocatalytic performance of GQDs/NH2-MIL-125 was significantly improved. 5 wt% GQDs loading sample (2-GQDs/NH2-MIL-125) exhibited the best antibacterial properties. The killing efficiency by 2-GQDs/NH2-MIL-125 against E. coli and S. aureus (107 CFU·mL−1) increased from 40 % and 75 % by NH2-MIL-125 to 92 % and 93 % within 60 min, respectively. Moreover, through the single-wavelength antibacterial experiments, it was found that the introduction of GQDs led to a wide-range-responsive antibacterial effect. Through photocatalytic trapping experiments and ESR analysis, the dominant roles of superoxide radicals (•O2–) were confirmed in the antibacterial process. Finally, by studying the state of bacteria via TEM, confocal fluorescent images, and gel electrophoresis, it was found that the active substances not only destroyed the cell membranes but also further destroyed DNA to achieve the purpose of completely killing bacteria. This work provides a new method for the rapid disinfection of pathogenic microorganisms using GQDs-related photocatalysts.

Enhanced single-electron transfer for efficiently photocatalytic H2O2 production over g-C3N4 decorated with TEMPO-oxidized cellulosic carbon

Designing efficient semiconductors for photocatalytic oxygen reduction reaction (ORR) without sacrificial agent is an urgent challenge for H2O2 production under ambient condition. Graphite carbon nitride (g-C3N4) exhibits controllable regulation in band structure and light absorption for photocatalytic process. However, the photocatalytic H2O2 synthesis by pristine g-C3N4 is poor due to the fast recombination of photogenerated carriers and unfavorable selectivity of ORR. To enhance the photocatalytic H2O2 production, different types of carbon can use in combination with g-C3N4. In the present work, we show how cellulose fiber from bamboo can lead to hybrid C/ g-C3N4 photocatalyst with enhanced photocatalytic activity and H2O2 production rate of 121.75 μmol·L−1·h−1, which is 6.2-fold higher than that of pure g-C3N4 without any sacrificial agent. The experimental results confirmed that TEMPO-cellulose derived hydrophilic carbon can not only accelerate the transfer of photo-generated electrons as well as efficient charge carrier separation, but also promote the sequential two-step single-electron ORR route. Thus, this work provides a pioneering perspective for tuning the electronic interaction between g-C3N4 and cellulosic carbon for enhanced photocatalytic H2O2 synthesis.

Ternary Polyaniline@Bi2O3-BiOCl Nanocomposites as Innovative Highly Active Photocatalysts for the Removal of the Dye under Solar Light Irradiation.

Ternary PANI@Bi2O3-BiOCl nanocomposites were successfully synthesized during the oxidative polymerization of aniline monomer in the presence of Bi2O3. PANI@Bi2O3-BiOCl nanocomposites were characterized by several analytical techniques, including X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), N2 physisorption, UV-Vis Diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The effective PANI-semiconductor interaction promotes the fast separation and transfer of photogenerated electrons and holes, enhancing the photocatalytic efficiency of the materials towards methylene blue (MB) degradation under solar light irradiation. The best results were obtained by 0.5%PANI@Bi2O3-BiOCl, leading to 80% MB degradation in 2 h, four times higher than pristine Bi2O3-BiOCl. Moreover, 0.5%PANI@Bi2O3-BiOCl maintained stable photocatalytic performances for four cycles without significant activity loss. Various scavengers (isopropyl alcohol, formic acid, and benzoquinone) were used to identify the active species by trapping holes and radicals generated during the photocatalytic degradation process. Finally, a probable photocatalytic mechanism of PANI@Bi2O3-BiOCl photocatalyst was suggested.

Nanocellulose/carbon dots hydrogel as superior intensifier of ZnO/AgBr nanocomposite with adsorption and photocatalysis synergy for Cr(VI) removal

A novel nanocellulose/carbon dots hydrogel (NCH) was fabricated using cellulose nanofibrils (CN), carbon dots (CD) and zinc oxide (ZnO)/silver bromide (AgBr) nanocomposite, where CD enhanced amino group-induced adsorption of hexavalent chromium (Cr(VI)) and promoted the photocatalytic properties of ZnO/AgBr nanocomposite via the transfer of photogenerated electrons, resulting in enhanced efficiency in the removal of Cr(VI) from aqueous solution. The structure, morphology, and physicochemical properties of the prepared NCH were characterized, with the results of adsorption and photocatalysis experiments showing the maximum theoretical adsorption capacity of the NCH to be 315 mg/g, 219 times that of the ZnO/AgBr nanocomposite; the apparent removal rate constant of the NCH was 0.0319 min−1, 11.7 times that of the ZnO/AgBr nanocomposite. Furthermore, the removal performance of NCH was attributed to CD-enhanced synergistic adsorption and photocatalysis effects, supported by characterization and experimental results. This work provides insight into the design and fabrication of a novel adsorptive photocatalyst with CD-enhanced synergistic adsorption and photocatalysis effects for removing Cr(VI) from aqueous solution.

Variable valence Mo5+/Mo6+ ionic bridge in hollow spherical g-C3N4/Bi2MoO6 catalysts for promoting selective visible light-driven CO2 photoreduction into CO

Herein, the catalysts of ultrathin g-C3N4 surface-modified hollow spherical Bi2MoO6 (g-C3N4/Bi2MoO6, abbreviated as CN/BMO) were fabricated by the co-solvothermal method. The variable valence Mo5+/Mo6+ ionic bridge in CN/BMO catalysts can boost the rapid transfer of photogenerated electrons from Bi2MoO6 to g-C3N4. And the synergy effect of g-C3N4 and Bi2MoO6 components remarkably enhance CO2 adsorption capability. CN/BMO-2 catalyst has the best performances for visible light-driven CO2 reduction compared with single Bi2MoO6 and g-C3N4, i.e., its amount and selectivity of CO product are 139.50 μmol g−1 and 96.88% for 9 h, respectively. Based on the results of characterizations and density functional theory calculation, the photocatalytic mechanism for CO2 reduction is proposed. The high-efficient separation efficiency of photogenerated electron-hole pairs, induced by variable valence Mo5+/Mo6+ ionic bridge, can boost the rate-limiting steps (COOH*-to-CO* and CO* desorption) of selective visible light-driven CO2 conversion into CO. It inspires the establishment of efficient photocatalysts for CO2 conversion.

Fabrication of CuBi2O4/Bi2MoO6 p-n heterojunction as synergistic photoelectric catalyst for efficient removal of ciprofloxacin in photo-electro-Fenton-like system

Ciprofloxacin (CIP) has been widely detected in aquatic ecosystems due to antibiotics abuse and its refractory, which seriously affected public health and ecological safety. Herein, we devised a photo-electro-Fenton-like (PEF-like) system for efficient removal of CIP. CuBi2O4/Bi2MoO6 (CBMO) p-n heterojunction composites were successfully fabricated through hydrothermal and solvothermal methods. Significantly, CBMO composite catalysts were not only able to generate ·OH by the Cu+ activation of H2O2 during electro-Fenton process, the following synergistic effects in the photo-Fenton process simultaneously promoted the production of more ·OH. The internal electric field (IEF) in the p-n heterojunction was conducive to the directional transfer of photogenerated electrons, thus promoting the spatial separation of photogenerated carriers. Moreover, photogenerated electrons could directly or indirectly activate H2O2 to yield more abundant ·OH, thus improving photoelectric catalytic activity. Consequently, the degradation efficiency of CIP during PEF-like system was 97.4% in 90 min and the mineralization efficiency finally reached 78.5% in 180 min. The prepared CuBi2O4/Bi2MoO6‐40 (CBMO-40) possessed great stability and structural integrity after six consecutive cycles. Furthermore, the CBMO-40 in PEF-like system showed superior performance for the removal of diverse antibiotics, including quinolones, tetracyclines and sulfonamides, which revealed the broad applicability of CBMO-40 for the antibiotics removal in PEF-like system.

High-efficient C3N4-viologen charge transfer systems for promoting photocatalytic H2 evolution through band engineering

Accelerating the charge transfer (CT) capability of photocatalysts is an efficient way to improve the overall photocatalytic performance, yet the precise regulation of CT in photocatalyst systems is still lacking. In this paper, a series of hybrid photocatalysts composed of graphitic carbon nitride (CN) and various viologens (V) were prepared for the photocatalytic hydrogen evolution (PHE) from water splitting under visible-light irradiation. Considering the fixed energy structure of CN, the different electron-withdrawing substituents were introduced to engineer the band structure of V delicately and modulate the CT process between CN and V. It was shown that all the hybrid photocatalysts CN-x%Vy exhibited higher photocatalytic performance, of which CN–1%V3, possessing the strongest electron withdrawing group (-NO2), demonstrated the best PHE performance (3572.3 μmol g−1 h−1), exceeding 29 times over the unmodified CN. It was proposed that the introduction of V can optimize the interfacial photogenerated electron transfer (CN→V→Pt) of the whole photocatalytic system effectively. We highlighted the V as an efficient chemical segment to modify semiconductors toward enhanced activity due to the following unique characteristics: (i) the unique redox ability, (ii) the easy synthetic methods for controlling the band structures precisely, and (iii) the inherent positively charged feature. This work provides a deep understanding of CT for the rational design of high-performance photocatalysts through band engineering.

An NIR-Driven Upconversion/C3N4/CoP Photocatalyst for Efficient Hydrogen Production by Inhibiting Electron-Hole Pair Recombination for Alzheimer's Disease Therapy.

Redox imbalance and abnormal amyloid protein (Aβ) buildup are key factors in the etiology of Alzheimer's disease (AD). As an antioxidant, the hydrogen molecule (H2) has the potential to cure AD by specifically scavenging highly harmful reactive oxygen species (ROS) such as •OH. However, due to the low solubility of H2 (1.6 ppm), the traditional H2 administration pathway cannot easily achieve long-term and effective accumulation of H2 in the foci. Therefore, how to achieve the continuous release of H2 in situ is the key to improve the therapeutic effect on AD. As a corollary, we designed a rare earth ion doped g-C3N4 upconversion photocatalyst, which can respond to NIR and realize the continuous production of H2 by photocatalytic decomposition of H2O in biological tissue, which avoids the problem of the poor penetration of visible light. The introduction of CoP cocatalyst accelerates the separation and transfer of photogenerated electrons in g-C3N4, thus improving the photocatalytic activity of hydrogen evolution reaction. The morphology of the composite photocatalyst was shown by transmission electron microscopy, and the crystal structure was studied by X-ray diffractometry and Raman analysis. In addition, the ability of g-C3N4 to chelate metal ions and the photothermal properties of CoP can inhibit Aβ and reduce the deposition of Aβ in the brain. Efficient in situ hydrogen production therapy combined with multitarget synergism solves the problem of a poor therapeutic effect of a single target. In vivo studies have shown that UCNP@CoP@g-C3N4 can reduce Aβ deposition, improve memory impairment, and reduce neuroinflammation in AD mice.

Synthesis of SiO2-doped BiOX (X = Cl, Br) II-type heterojunctions and 2H-MoS2-doped SiO2@BiOX Z-scheme heterojunctions: A comparative study

In this research, II-type SiO2@BiOX (X = Cl, Br) was synthesized by loading SiO2 microspheres onto 2D layered BiOX using a simple one-step hybrid solvothermal method. On this basis, the two-dimensional bismuth oxyhalide layer was modified by using 2H-MoS2 layer and compounded with SiO2 microspheres to form 2H-MoS2@SiO2@BiOX (X = Cl, Br) Z-scheme heterostructured photocatalysts. The energy band structure and photogenerated carrier transport mechanism of the composite photocatalysts were analyzed by various characterization methods, and the transport efficiency of photogenerated carriers of II-type heterojunction and Z-scheme heterojunction were compared. The differences in photocatalytic activities of II-type heterojunctions and Z-scheme heterojunctions were shown by microscopic mechanisms and macroscopic phenomena. The photocatalytic degradation experiments showed that the doping of 2H-MoS2 acted as a conducting medium in the p-BiOX/n-SiO2 heterostructure, which changed the photogenerated electron transfer and formed the Z-scheme heterojunction structure, thus promoting the photocatalytic activity. In this study, the structure of BiOX-based composite photocatalyst was optimized and constructed, and a new idea was provided for the design and construction of II-type heterojunction and Z-scheme heterojunction photocatalysts.

Nano heterojunction of double MOFs for improved CO2 photocatalytic reduction performance

Metal-organic frameworks (MOFs), featuring semiconductor-like behavior, are promising for the photocatalytic reduction of CO2. While their practical application is hindered by the disadvantages of low charge migration efficiency and fast electron-hole pair complexation. In this paper, a simple solvothermal method was used to load NH2-UiO-66 onto the surface of MIL-101(Cr) to form a nano type II heterojunction double MOFs composite of NH2-UiO-66 @MIL-101. The results show that the heterostructure of NH2-UiO-66 @MIL-101 promotes the separation of photogenerated electron-hole pairs and accelerates the interfacial photogenerated electron transfer under light, and the NH2-UiO-66 @MIL-101 type II heterojunction exhibits higher activity for photocatalytic reduction of CO2 compared with pure MIL-101(Cr) and NH2-UiO-66. In addition, the possible photocatalytic mechanism was further elucidated to demonstrate the increased photocatalytic activity of NH2-UiO-66 @MIL-101. This study provides effective insights for designing efficient MOFs photocatalysts for CO2 reduction to enhance the photocatalytic activity for environmental protection and governance.

3D nanothorn cluster-like Zn-Bi2S3 sensitized WO3/ZnO multijunction with electron-storage characteristic and adjustable energy band for improving sustained photoinduced cathodic protection application

Solar energy-driven photoinduced cathodic protection (PICP) technology utilizes solar energy to protect marine metallic structures against severe marine corrosion. To enhance the solar energy utilization and strengthen dark-state application for realizing long-term protection, herein, a 3D nanothorn cluster-like WO3/ZnO/Zn-Bi2S3 multijunction with electron-storage characteristic and adjustable energy band was constructed. It exhibited an enhanced continuous release of photogenerated electron and sustained cathodic protection in dark conditions. Exposed to only 100 s of simulated sunlight irradiation, the WO3/ZnO/Zn-Bi2S3could store 5.27×10−2 C electrons and provide up to 5460 s of sustained CP for the coupled metal after light stops, which was 10.8 and 3.5 times higher than those of WO3/ZnO (4.89×10−3 C) and WO3/Zn-Bi2S3 (1.51×10−2 C), respectively. The WO3 nanothorn cluster-like substrate with reversible valence transformation of W6+/W5+ together with the large surface area and one-dimensional transmission path can store photogenerated electrons under illumination and release photogenerated electrons after light stops efficiently. Notably, the tri-phase heterojunction with introduction of intermediate “Carrier Springboard” ZnO between WO3 and Zn-Bi2S3 contributed to the building of well-matched energy band gradient to strengthen the directional backward transfer of photogenerated electrons and holes. The energy band of Bi2S3 sensitizer was adjusted towards negative direction by doping with zinc element to boost PICP application performance. The reversible valence transformation of Bi3+/Bi5+ could promote the consumption of photogenerated holes. These synergistically enhanced the sustained PICP performance of the WO3/ZnO/Zn-Bi2S3 photoelectrode both in dark and light conditions. This design shed light on energy-storage photoelectrodes for long-term PICP of metallic materials.

A three-dimensional DNA walker and silver nanoparticles promoting lattice-strain-driven photo-induced electron transfer for high-performance semi-homogeneous biosensing

As an important tumor marker, the ultra-sensitive detection of low-abundance microRNAs provides important data support for early warning of tumors. Herein, taking microRNA-141 as the target model, a novel enzyme-free semi-homogeneous photoelectrochemical (SHO-PEC) biosensor was designed by entropy-driven three-dimensional (3D) DNA walker with exponential signal amplification, magnetic enrichment and separation of pseudo-targets, bridged CdTe@ZnS quantum dots to promote photocathodic current enhancement, and in situ generated silver nanoparticles (NPs) to accelerate charge separation. In this protocol, ZnS shell passivates the surface defects of the soft core CdTe, introducing considerable strain that causes electrons to extend towards the shell, which is responsible for the higher photocurrent response. Also, the Ag NPs enable ultrafast photogenerated electron transfer by forming Schottky junctions. These two unique sensitized mechanisms were proposed for the first time in PEC sensing. Moreover, a one-step simple electrode modification strategy avoids tedious layer-by-layer assembly and rinsing steps. These make the "signal-on" SHO-PEC biosensor with remarkable advantages of high sensitivity, good specificity, strong reliability, fast speed, easy operation, and low cost. This research provides a new initiative for the development of PEC sensing platforms with excellent comprehensive performance.

In-situ synthesis of novel dual S-scheme AgI/Ag6Mo7O24/g-C3N4 heterojunctions with tandem structure for photocatalytic degradation of organic pollutants

The controllable design of multivariate heterojunction with sequential structures is of significant relevance for breaking the performance limit of binary composite photocatalysts. In this work, the novel dual S-scheme ternary-component AgI/Ag6Mo7O24/exfoliated g-C3N4 (ECN) composite was prepared by a two-step in-situ synthetic strategy. The energy band bending at the heterointerface and the formation of dual built-in electric field could be observed due to distinct work functions of different components in the ternary composite. Benefiting from the sequential heterojunction structure, the AgI/Ag6Mo7O24/ECN composite achieved 98.7% removal efficiency of 2-nitrophenol (2-NP) within 70 min under visible light irradiation, and AgI/Ag6Mo7O24/ECN also showed higher degradation efficiency for a variety of organic pollutants such as methylene blue (MB), rhodamine B (RhB), methyl orange (MO), 4-nitrophenol (4-NP), 2-sec-butyl-4,6-dinitrophenol (DNBP) and tetracycline (TC). Notably, •OH and •O2− played dominant roles in the AgI/Ag6Mo7O24/ECN set up, which was consistent with the dual S-scheme charge transfer mechanism. In-depth insights for the photodegradation of 2-NP were presented based on a combined DFT study and GC-MS analysis. Additionally, the photoreduction of Ag+ in AgI/Ag6Mo7O24/ECN was also evaded by the fast transfer of photogenerated electrons through the dual S-scheme pathway, achieving the effect of killing two birds with one stone.

Nickel Phosphide Clusters Sensitized TiO2 Nanotube Arrays as Highly Efficient Photoanode for Photoelectrocatalytic Urea Oxidation

AbstractThe photoelectrocatalytic urea oxidation reaction (PEC‐UOR) holds a great promise for the wastewater remediation and energy production. However, the low efficiency of semiconductor/cocatalysts type photoanodes for UOR restricts their applications in photoelectrocatalytic system. Herein, a new semiconductor/cocatalyst, Ni2P clusters sensitized TiO2 nanotube arrays photoanode (Ni2P/TiO2‐NTAs) for PEC‐UOR with high efficiency are developed. The 1D TiO2‐NTAs structure accelerates urea molecules diffusion and promotes CO2 gas release at the electrode interface. Meanwhile, Ni2P is also beneficial to urea molecule absorption and CO2 desorption and enable to lower the energy barrier for amine (NH) dehydrogenation. Furthermore, the robust interfacial charge transfer pathway between Ni2P and TiO2 interface promotes the separation of photogenerated electrons and holes and the transfer of photogenerated electrons from Ni2P to TiO2. Therefore, this photoanode shows excellent PEC‐UOR performance with the potential of 1.43 V versus reversible hydrogen electrode (RHE) when the current density reaches 10 mA cm−2, which is much lower than that of 2.24 V versus RHE and 1.58 V versus RHE for TiO2‐NTAs and Ni(OH)2/TiO2‐NTAs, respectively.

0D/2D/3D ternary Au/Ti3C2/TiO2 photocatalyst based on accelerating charge transfer and enhanced stability for efficiently hydrogen production

The development of multi-components composited photocatalytic materials with strong interaction is a key approach to realize the spatial separation and fast transfer of charge carriers in H2 production. In this study, 2D layered Ti3C2 with –OH group was introduced to stabilize thiolate-protected Au clusters by strong electrostatic interaction and coupled with TiO2 nanoparticles to build a 0D/2D/3D ternary Au/Ti3C2/TiO2 photocatalyst for H2 evolution. In this composited material, Ti3C2 can serve as the electron transfer intermedium accelerating charge transfer from TiO2 to Au clusters. Au/Ti3C2/TiO2 shows excellent photocatalytic performance for H2 production (7989 μmol⋅g-1h−1), approximately 13.7 times higher than that of Au/TiO2. Photoluminescence spectra and photoelectrochemical results confirm that the introducing of layered Ti3C2 into ternary Au/Ti3C2/TiO2 material can markedly suppress the photogenerated charge recombination and thus enhance the charge separation efficiency. Moreover, after several cyclic reactions, Au/Ti3C2/TiO2 maintained a high stability and durability, indicating the strong interaction of Ti3C2 with Au and TiO2. This work not only highlights the significant role of MXene for the enhancement of photogenerated electron transfer, but also demonstrates a clearly objective to construct a suitable composited photocatalyst for H2 production.

Rational design of MoS2@COF hybrid composites promoting C-C coupling for photocatalytic CO2 reduction to ethane

Photocatalytic CO2 reduction into high-value C2+ products such as ethane is quite exciting but challenging due to multielectron steps involved and sluggish C-C coupling kinetics. Herein, a well-designed MoS2@COF hybrid composite is prepared for efficient and selective CO2 photoreduction to C2H6. In-depth experimental and theoretical studies reveal that the interfacial electric field built in the heterojunction accelerates the photogenerated electrons transfer from MoS2 to COF under light irradiation, greatly facilitating charge separation and transfer and thus enhancing the activity and C2H6 selectivity for CO2 photoreduction. The optimized MoS2@COF-15 achieves C2H6 production rate up to 56.2 μmol·g−1·h−1 with 83.8% of selectivity, which is about 8.6 and 31.2 times higher than that of pristine MoS2 and COF under identical conditions. The in-situ DRIFTS and DFT calculations indicate that the structure of MoS2@COF composite can promote the adsorption of *CO and the formation of *COCO, facilitating C-C coupling to convert into C2H6 product.

Multifunctional photocatalyst of graphitic carbon embedded with Fe2O3/Fe3O4 nanocrystals derived from lichen for efficient photodegradation of tetracycline and methyl blue

ABSTRACT We propose a feasible and economical method of constructing biomass-based multifunctional photocatalysts with excellent adsorption performance and high photodegradation abilities toward tetracycline (TC) and methyl blue (MB) under visible light. A series of novel hybrids of porous graphitic carbon embedded with Fe2O3/Fe3O4 nanocrystals (denoted as Fe2O3/Fe3O4@C) were derived from lichen doped with different dosages of Fe3+ by calcination at 700°C under a N2 atmosphere. The Fe2O3/Fe3O4@C hybrids exhibited nanoflake-like shapes, mesoporous structures, and efficient visible light harvesting, thus indicating enhanced adsorption ability and photoactivity toward pollutants. The formed Fe2O3/Fe3O4 heterojunction improved the separation efficiency and inhibited the recombination of photogenerated carriers, whereas the carbon network improved the transfer of photogenerated electrons. Under optimised conditions, the Fe2O3/Fe3O4@C-1 hybrid demonstrated enhanced photodegradation efficiencies of 96.4% for TC and 100% for MB under visible light. In addition, electron spin resonance and trapping measurements were performed to identify active species and determine the photocatalytic mechanism toward pollutants. •O2 − and •OH were the active species involved, playing critical roles in the TC and MB photodegradation processes. In addition, a bacterium test revealed that the products of TC degradation by Fe2O3/Fe3O4@C-1 showed low biological toxicity. This work provides a promising preparation strategy or biomass-based photocatalysts for application in environmental pollutant treatment.