Photoinduced Hole Transfer Research Articles

Doping-free Janus homojunction solar cell with efficiency exceeding 23%

Photovoltaic solar cell is one of the main renewable energy sources, and its power conversion efficiency (PCE) is improved by employing doping or heterojunction to reduce the photogenerated carrier recombination. Here, we propose a straightforward strategy for constructing high-PCE homojunction solar cells, where intrinsic driving forces can simultaneously enhance the efficiency of carrier separation and transport. Thanks to the intrinsic dipole of Janus structure, doping-free Janus homojunction has naturally not only a type-II band alignment to promote the photoexciton dissociation, but also a reduced effective bandgap to enhance light absorption. More importantly, the interfacial dipole can facilitate the separation of carriers into different layers, thereby promoting carrier separation; and the intrinsic dipole across the Janus structure can drive photoinduced electron and hole transfer to opposite layers, enhancing carrier transport. We illustrate the concept in titanium-based Janus monolayer homojunction, where the theoretically observed PCE reaches 23.22% of TiSSe homojunction. In contrast to the previous cell architectures that require complex processing procedures and often result in defects, the doping-free homojunction configuration promises both high PCE and significantly lower manufacturing costs. Our work opens an avenue to design low-cost, high-efficiency solar cells.

The Diverse Electrochemistry and Photophysics of Pyrrolopyrroles

Pyrrole is among the most popular molecular scaffolds for biology. Tetrapyrroles, such as porphyrins, corrins and their derivatives, are the quintessential redox centers and chromophores exhibiting a wide range of electrochemical and optical characteristics. Similarly, pyrrolopyrroles, built on condensed five-member rings with nitrogens as heteroatoms, offer scaffolds for organic chromophores with diversity of redox and photophysical properties. For example, pyrrolo[3,2-b]pyrroles are stable electron-rich UV absorbers with quadrupole symmetry (Acc. Chem. Res. 2017, 50, 2334-2345). They can act as immensely potent electron donors and attaching electron-accepting moieties to them leads to the emergence of a myriad of optical phenomena, such as excited-state symmetry breaking (Commun. Chem. 2020, 3, 190) and generating white fluorescence by tuning donor-acceptor electronic coupling (Chem. Sci. 2023). Attaching carbonyls to the pyrrolopyrrole rings drastically changes their electronic properties, making them pronouncedly electron deficient and shifting their absorption to the visible spectral region. For example, 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-diones, or diketopyrrolopyrroles (DPPs) for short, are excellent electron acceptors and photooxidants (Adv. Opt. Matter. 2015, 3, 2018-320). Their reduction potentials are susceptible to localized electric fields, which has allowed demonstrating dipole-induced rectification of photoinduced hole transfer (Angew. Chem. Int. Ed. 2018, 57, 12365-12369). This field susceptibility extends to the optical properties of DPPs, providing an extra dimension in their utility for photonics and optoelectronics. DPPs, and pyrrolopyrroles in general, are built on small bicyclic scaffolds, i.e., considerably smaller than those of other multi-pyrrole chromophores. The small size enhances the susceptibility of their redox properties to solvation and makes them attractive photoprobes. Therefore, this class of compounds have become indispensable agents for electrochemical and photonic science and engineering.

WO3/BiOBr S-Scheme Heterojunction Photocatalyst for Enhanced Photocatalytic CO2 Reduction.

The photocatalytic CO2 reduction strategy driven by visible light is a practical way to solve the energy crisis. However, limited by the fast recombination of photogenerated electrons and holes in photocatalysts, photocatalytic efficiency is still low. Herein, a WO3/BiOBr S-scheme heterojunction was formed by combining WO3 with BiOBr, which facilitated the transfer and separation of photoinduced electrons and holes and enhanced the photocatalytic CO2 reaction. The optimized WO3/BiOBr heterostructures exhibited best activity for photocatalytic CO2 reduction without any sacrificial reagents, and the CO yield reached 17.14 μmol g-1 after reaction for 4 h, which was 1.56 times greater than that of BiOBr. The photocatalytic stability of WO3/BiOBr was also improved.

A highly crystalline face-on π-conjugated polymer based on alkoxythiophene-flanked benzobisthiazole for organic photovoltaics

The use of noncovalent intramolecular interactions constitutes a powerful design strategy for preparing π-conjugated polymers featuring high backbone coplanarities and thereby high crystallinities. Herein, we report the design and synthesis of an alkoxythiophene-flanked benzobisthiazole (BBTz) as a new building unit for π-conjugated polymers, which was subsequently copolymerized to give a simple BBTz-bithiophene copolymer with alkyl and alkoxy groups (PDBTz2). Owing to the S···O noncovalent intramolecular interactions between the alkoxy oxygens and thiazole sulfurs in BBTz, PDBTz2 showed greater coplanarity and crystallinity than its alkyl counterpart, PDBTz1. Interestingly, the backbone orientation was completely altered from the edge-on orientation observed for PDBTz1 to a face-on orientation for PDBTz2, which is preferable for organic photovoltaics (OPVs). In addition, the electron-donating nature of the alkoxy group increased the HOMO energy level of PDBTz2 compared to that of PDBTz1, which enabled photoinduced hole transfer from a nonfullerene acceptor, Y6, to the polymer. As a result, the short-circuit current density of an organic photovoltaic cell based on PDBTz2 and Y6 was significantly greater than that of a cell based on PDBTz1 and Y6. This study confirmed that alkoxythiophene-flanked BBTz is a promising building unit for high-performance π-conjugated polymers.

G-C3N4/In2O3 heterojunction films and their excellent photocatalytic performance in fruit preservation and organic dye degradation

We prepared g-C3N4/In2O3 composite films on the wire mesh of stainless steel by a hydrothermal method combined with annealing. XRD, SEM, and XPS results confirmed the heterojunction formation of g-C3N4/In2O3. UV–vis spectroscopy showed that the heterojunction films exhibited enhanced visible light absorption capacity compared with the pristine In2O3 films. Compared with the individual In2O3 films, the PL intensity of the g-C3N4/In2O3 composite films was remarkably reduced, their photocurrent density was significantly increased, and the semicircle in EIS plots was reduced. All the above changes are attributed to the heterojunction formation between g-C3N4 and In2O3. According to our proposed mechanism, photogenerated electrons transfer from g-C3N4 to In2O3 while the holes move in the opposite direction. Therefore, the spatial transfer and separation of photoinduced electrons and holes was achieved. In other words, the recombination efficiency of photogenerated electrons and holes was remarkably suppressed. In photocatalytic RhB degradation, g-C3N4/In2O3 heterojunction films exhibited much higher photocatalytic activity than the pristine In2O3 films. In our self-made photocatalytic fruit-preservation system, these g-C3N4/In2O3 heterojunction films showed excellent fruit preservation ability. Specifically, the bananas remained turquoise green without turning yellow or black spots, even black patches, after a seven-day evaluation period.

Trifluoromethyl‐Substituted Perylene Diimides for Rapid and Sensitive Film‐Based Fluorescence Detection of Methamphetamine and Cocaine Hydrochloride

AbstractFilm‐based fluorescence sensors are attractive for rapid and on‐site detection of illicit drugs, due to their potential for portability, high sensitivity and reusability. Three new bay‐substituted perylene diimide derivatives are synthesized , P1‐CH3 (1‐methyl), P1‐CF3 (1‐trifluoromethyl), and P1‐(CF3)2 (1,7‐di‐trifluoromethyl) that can be solution processed into thin films capable of detecting methamphetamine hydrochloride (MA•HCl) and cocaine•HCl via a luminescence quenching mechanism. The ionization potentials of the materials are sufficiently high to enable photoinduced hole transfer to occur, which led to the luminescence quenching. The trifluoromethyl‐substituted PDIs exhibit superior sensitivity and reversibility of the luminescence quenching process. In particular, P1‐(CF3)2 shows a limit of detection to MA•HCl of ≈100 ng after a 15‐second exposure, and its luminescence can be fully recovered either through mild heating or being placed in an air flow. Furthermore, by using the luminescence quenching and recovery responses of four PDI sensing materials it is possible to differentiate MA•HCl, cocaine•HCl, from aspirin, caffeine, sugar, and (sebum) skin oil in around a minute.

Photoinduced energy and electron transfer at graphene quantum dot/azobenzene interfaces

The photophysical properties of azobenzene–graphene quantum dot interfaces show enhanced photoinduced hole and energy transfer rates for the trans isomer, making it the acvite specie compared to the cis isomer.

Perylene Diimide Based Fluorescent Sensors for Drug Simulant Detection: The Effect of Alkyl-Chain Branching on Film Morphology, Exciton Diffusion, Vapor Diffusion, and Sensing Response.

Luminescence-based sensing has been demonstrated to be a powerful method for rapid trace detection of chemical vapors (analytes). Analyte diffusion has been shown to be the critical factor for real-time luminescence-based detection of explosive analytes via photoinduced electron transfer in amorphous films of conjugated polymers and dendrimers. However, similar studies to determine the critical factors for sensing have not been performed on materials that employ photoinduced hole transfer (PHT) to detect low electron affinity analytes such as illicit drugs. Nor have such studies been performed on semicrystalline sensing films. We have developed a family of perylene diimide-based sensing materials capable of undergoing PHT with amine-group containing analytes. It was found that the choice of branched alkyl chain [1-hexylheptyl (PHH), 2-hexyloctyl (PHO), or 2,2-dihexyloctyl (PDHO)] attached to the nitrogen atoms of the imide moiety strongly affected the solution-processed film morphology. PHH and PHO were found to contain crystalline phases, whereas PDHO was essentially amorphous. The degree of crystallinity strongly influenced exciton diffusion, with PHH and PHO exhibiting exciton diffusion coefficients that were 20× and 10× greater than the value of the amorphous PDHO. The degree of film crystallinity was also found to be critical when the films were applied to detect N-methylphenethylamine (MPEA), a simulant of methamphetamine. While PHH had the largest exciton diffusion coefficient [(1.0 ± 0.2) × 10-2 cm2 s-1] and analyte uptake (12.3 ± 1.8 ng) it showed the smallest quenching efficiency (2.6% ng-1). In contrast, PHO, which sorbed the least analyte (6.1 ± 0.4 ng) of the three compounds, had the largest quenching efficiency (7.1% ng-1) due to its molecular packing and hence exciton diffusion coefficient [(4.5 ± 1.4) × 10-3 cm2 s-1] not being affected by sorption of the analyte. These results show that when applying fluorescent films in practical detection scenarios there is a potential trade-off between a high exciton diffusion constant and analyte diffusion for semicrystalline sensing materials and that a high exciton diffusion coefficient in an as-cast film does not necessarily translate into a more efficient fluorescent quenching. The results also show that sensing materials that form semicrystalline films, whose packing is not disrupted by analyte diffusion, provide a route for overcoming these effects and achieving high sensitivity.

Differentiating Between V- and G-Series Nerve Agent and Simulant Vapours Using Fluorescent Film Responses.

In-field rapid and reliable identification of nerve agents is critical for the protection of Defence and National Security personnel as well as communities. Fluorescence-based detectors can be portable and provide rapid detection of chemical threats. However, most current approaches cannot differentiate between dilute vapors of nerve agent classes and are susceptible to false positives due to the presence of common acids. Here a fluorescence-based method is shown for rapid differentiation between the V-series and phosphonofluoridate G-series nerve agents and avoids false positives due to common acids. Differentiation is achieved through harnessing two different mechanisms. Detection of the V-series is achieved using photoinduced hole transfer whereby the fluorescence of the sensing material is quenched in the presence of the V-series agent. The G-series is detected using a turn-on mechanism in which a silylated excited state intramolecular proton transfer sensing molecule is selectively deprotected by hydrogen fluoride, which is typically found as a contaminant and/or breakdown product in G-series agents such as sarin. The strategy provided discrimination between classes, as the sensor for the G-series agent class is insensitive to the V-series agent, and vice versa, and neither responded to common acids.

Fabrication of g-C3N4@porphyrin nanorods hybrid material via CTAB surfactant-assisted self-assembly for photocatalytic degradation of Cr(VI) and methylene blue

Photocatalysts are an attractive solution for pollutant degradation under sunlight irradiation. One approach that has been proposed to enhance their activity is to combine two semiconductors, which can broaden the photon energy harvesting regions and improve charge separation. Herein, a facile approach to fabricating a g-C3N4@porphyrin nanorods hybrid material is presented using CTAB surfactant-assisted self-assembly of monomeric porphyrin molecules and g-C3N4 nanomaterials. Using different technical methods, the hybrid material was studied, and it was found that the porphyrin nanorods on the surface of g-C3N4 were all in the same place. The photocatalytic performance of the hybrid material was evaluated by investigating its behavior for the photo-oxidation and -degradation of Cr+6 ions and methylene blue organic dye under simulated sunlight irradiation. High photocatalytic performance towards these two pollutants was exhibited by the hybrid material with a removal percentage of nearly 100% after 100 min of reaction time under the simulated sunlight spectrum. Also, a possible photocatalytic mechanism of the C3N4@porphyrin nanorods photocatalyst was proposed. This mechanism involved the efficient separation and transfer of photo-induced electrons and holes on the surface of the hybrid material. This work offers a simple and efficient method for creating high-performance photocatalysts, and we have made progress in our understanding of their photocatalytic mechanisms. The findings have important implications for wastewater treatment and solar energy conversion. The use of this hybrid material may contribute to addressing environmental challenges and assist in building sustainable energy systems.

Effect of the halogen substitution on the interfacial properties of MAPbI3 (110)/Ti3C2T2 (001): First-principles calculations

To improve the optoelectronic properties and charge extraction efficiency of perovskite devices, precise device design and expert interface engineering are essential. In this study, we utilized first-principles simulations to investigate the structural, electrical, and optical characteristics of the interfaces between MAPbI3 and Ti3C2T2 (T = Cl, Br, I). Our computed charge density differences indicate that the internal electric field of MAPbI3/Ti3C2T2 promotes the transfer and separation of photoinduced electrons and holes. Furthermore, the heterostructures exhibit enhanced optical absorption, with higher absorption intensity observed in the visible band. Notably, the PbI2/Ti3C2Br2 interface shows the strongest cohesive energy, charge transfer, and optical absorption among the interfaces investigated. These findings provide detailed insights into the atomic-level interfacial properties of MAPbI3/Ti3C2T2 and offer valuable theoretical recommendations for the development of novel perovskite devices.

Charge Transfer in Amine-Free CsPbBr3 Perovskite Nanocrystals and Organic Hole-Acceptor Hybrid Structures

Outstanding optoelectronic properties of cesium lead bromide (CsPbBr3) perovskite nanocrystals (PNCs) are recognized in various photonic devices. The surface chemistry of PNCs determines the excited states of PNCs, and their interactions with charge drive redox-active molecules. Here, we have investigated the potential difference between the surface modification of different CsPbBr3-based PNCs (amine-free and amine-based) with the hole-accepting organic molecule, i.e., 7,7-diethyl-5,7-dihydroindeno[2,1-b] carbazole (SPS-IND-Cbz). We have evaluated photoinduced hole transfer (PHT) with the steady-state photoluminescence and lifetime decay curves. Excitingly, the resulting PHT in amine-free CsPbBr3 PNC was nearly twice that of the amine-based CsPbBr3 PNC. Further, we have studied the photocurrent density of amine-free CsPbBr3 PNCs in the newly introduced organic molecule (SPS-IND-Cbz), enhancing the photocurrent responsivity, which could open a promising perspective for implementing these fascinating materials in various photonic strategies.

Hierarchical nanohybrid of CuS/NiS2/Ti3C2 heterostructure with boosting charge transfer for efficient photocatalytic hydrogen evolution

Fabricating heterostructure photocatalysts with co-catalysts can improve the separation and transfer of photo-induced electrons and holes for photocatalysis reactions. Herein, Ti3C2Tx nanosheets are obtained by chemical etching via the hydrothermal route and serve as a template for growing photocatalysts. NiS2 nanoparticles and CuS nanoneedles are deposited sequentially on the surface of Ti3C2Tx nanosheets to form “Type II” CuS/NiS2/Ti3C2Tx hierarchical heterostructure via the solvothermal method. The enormous nanoneedles morphology provides enlarged active sites for the photocatalytic processes. The fabricated CuS/NiS2/Ti3C2Tx heterostructure delivers an increased hydrogen generation rate of 32.66 mmol g−1 h−1, which is higher than that of pure CuS (2.38 folds), NiS2 (1.93 folds), and NiS2/Ti3C2Tx (1.71 folds). CuS/NiS2/Ti3C2Tx heterostructure also performs a superior hydrogen evolution retention of 97.7% after 4 cycles (one cycle lasts 4 h), implying its decent structural stability and light corrosion resistance. The reasons are ascribed to the constructed “Type II” heterostructure of CuS/NiS2 with higher active sites, improved conductivity, and efficient separation of electrons and holes. DFT calculation and Mott-Schottky plots results elucidate the formation mechanism of CuS/NiS2/Ti3C2Tx “Type II” structure. CuS/NiS2/Ti3C2Tx heterostructure also obtains a reduced bandgap with increased light absorption. The van der Waals force between 2D materials enhances the transfer of photo-generated electrons. This work demonstrates that designing hierarchical co-catalyst heterostructure without non-noble can effectively promote water splitting in the solar-to-chemical system.

Fluorescent sensors for the detection of free-base illicit drugs – Effect of tuning the electronic properties

Fluorescence-based detection of chemical vapours is of interest for low power, portable devices that can be used in the field. Detection using fluorescence quenching via photoinduced electron transfer has been widely explored for the detection of chemicals that have high electron affinities. However, the method cannot be used for compounds that have low electron affinities such as illicit drugs. In this manuscript we describe a family of four compounds that are designed to have large ionisation potentials and are capable of detecting free-base illicit drugs via a photoinduced hole transfer process. The materials are composed of a 2-(9,9-di-n-propylfluoren-2-yl)benzothiadiazole (Fl-BT) base unit, with its properties tuned through addition of different donor (9,9-di-n-propylfluorene) (Fl-BT-Fl) and acceptor [aldehyde (Fl-BT-CHO) and dicyanovinyl (Fl-BT-DCV)] units. The compounds could be solution processed to form good quality, neat thin films with photoluminescence quantum yields of between 35 % and 87 %. The films of the compounds containing the aldehyde and dicyanovinyl electron withdrawing groups were able to detect the vapours of (+)-methamphetamine, (±)-3,4-methylenedioxyamphetamine, cocaine, and fentanyl, whereas the parent Fl-BT could not detect cocaine nor (±)-3,4-methylenedioxyamphetamine. In contrast, Fl-BT-Fl could only detect fentanyl. Combining the response of all four sensing materials provides a method for discriminating both fentanyl and (+)-methamphetamine. Finally, we found that while the ionisation potential was a key parameter for detecting free-base drugs, factors such as the physical interaction of the analytes with the sensing films were also important.

Tunable Selectivity of Photocatalytic Benzyl Alcohol Transformation over Ag-Ion-Exchanged CdS Nanowires

Existing methods for the photocatalytic transformation of aromatic alcohols to value-added products via C–C cross-coupling are inefficient and insufficiently selective. Herein, a series of cadmium sulfide nanowires (CdS NWs) loaded with Ag2S (denoted as Ag2S@CdS NWs) are constructed via a simple Ag+ exchange protocol for the photocatalytic transformation of benzyl alcohol. We successfully demonstrated that the selectivity toward specific products in the photocatalytic transformation of benzyl alcohol over Ag+-exchanged CdS NWs is controlled by varying the amount of exchanged Ag+ ions. Notably, the product of the photocatalytic reaction was dependent on the amount of Ag+ ions exchanged: with a Ag+ exchange of <5 mol %, the C–C coupling product was obtained with >90% selectivity and >95% transformation yield owing to photoinduced electron transfer from the conduction band of CdS to Ag2S. Conversely, with a Ag+ exchange of >7 mol %, a cocatalyst in which Ag2S and Ag are mixed was produced, and benzaldehyde was obtained with >90% selectivity and >90% transformation yield because of photoinduced hole transfer from the valence band of CdS to Ag2S/Ag. This study proves that Ag2S@CdS NWs can be used as a basis for the development of heterojunction photocatalysts for the conversion of aromatic alcohols into value-added products via C–C cross-coupling reactions or photooxidation toward aromatic aldehyde.

Facile preparation of cyclized polyacrylonitrile modified FeWO4 with superior visible-light-driven photocatalysis

This paper reported the preparation of a novel high-performance visible-light-active photocatalyst (cyclized polyacrylonitrile (CPAN)/FeWO4 nanocomposite) from inexpensive and readily available polyacrylonitrile (PAN), FeSO4·7H2O, and Na2WO4·2H2O via a facile and practical approach. For the application to photocatalytic reduction of Cr(VI), the as-prepared CPAN/FeWO4 nanocomposite demonstrated not only substantially higher photocatalytic activity than FeWO4 nanoparticles, but also fairly good durability under visible-light irradiation. Besides, the as-prepared CPAN/FeWO4 also demonstrated a high efficiency in the visible-light-driven photocatalytic reduction of Cr(VI) in dilute black chromium-plating solution. The enhanced photocatalytic activity of the as-prepared CPAN/FeWO4 photocatalyst was attributed to the formation of n-p heterojunction, which facilitated the separation and transfer of photo-induced holes and electrons. Furthermore, the photocatalytic experimental conditions also heavily influenced the Cr(VI) reduction rate over the as-prepared CPAN/FeWO4 photocatalyst. This study provided useful information on the exploitation of PAN to modify semiconductor photocatalysts to create new higher efficiency visible-light-active CPAN/semiconductor composite photocatalysts.

Carbonate mediated hole transfer boosting the photocatalytic degradation of organic pollutants over carbon nitride nanosheets

Inspired by the important role of the manganese enzyme in photo-induced hole transfer of natural photosynthesis, we have developed an innovative carbonate-mediated-hole-transfer strategy for boosting the photocatalytic degradation of organic pollutants. We found that the carbonate species can effectively extract the photo-generated hole in the valence band of carbon nitride to generate ·CO3− and leaves electron in the conduction band for oxygen reduction to generate ·OH. The generated ·CO3− can be returned to its pristine state of CO32− via the oxidation of organic pollutants. The unique ·CO3−/CO32− shuttle could largely improve the charge separation via the fast hole extraction that leads to enhanced ·OH generation for accelerating the photocatalytic degradation of organic pollutants. As expected, the as-prepared carbon nitride exhibits markedly enhanced photocatalytic performance toward formaldehyde, p-chlorophenol, and phenol degradation than the one without carbonate as additive. The conceptual study demonstrated here may offer new viewpoints in designing high-efficient photocatalytic systems for environmental applications.

Green fabrication of h-BN/g-C3N4 with efficient holes transfer towards highly improved photocatalytic CO2 reduction and RhB degradation

The aim of this paper was to arise more attention to accelerating the separation and migration of photoexcited holes in the enhanced photocatalytic performances of composites. The highly effective h-BN/g-C 3 N 4 was fabricated via an economical and environment-protecting way. Different characterization techniques were utilized to examine the crystal structure, morphology, interface, optical property and specific surface of photocatalysts. Their photosensitivity properties, resistance for charge migration and flat-band potentials were explored by the photoelectrochemical analysis. Remarkably, a substantially larger visible-light catalytic CO 2 reduction of these composites was observed in contrast to pristine g-C 3 N 4 . The composite had the optimum BN dosage of 1 wt% and possessed good stability. The best kinetic constant of RhB degradation was 7.3 times that of bulk g-C 3 N 4 . Plate-like negatively charged BN as an efficient transfer of photoinduced holes were primarily responsible for the highly effective carriers separation in these prepared composites, thus contributing to much more electrons maintained on the conduction band of g-C 3 N 4 with powerful reduction potential to easily induce reduction reactions and the enhanced photocatalytic performance. The present study offers valuable insights into designing of other fresh composites with efficient holes transfer, as well as an approach to resolve the low energy conversing efficiency of g-C 3 N 4 in photocatalytic CO 2 reduction and comprehensive ecological improvement. • Series of effective BN/C 3 N 4 photocatalysts were successfully prepared by a green way. • Various characterizations were used to examine the structure and property of samples. • Composite has a substantially better visible light catalytic CO 2 reduction than C 3 N 4 . • Rate constant of RhB degradation over 1%BN/C 3 N 4 was 7.3 times that of bulk C 3 N 4 . • BN as a fast transfer of photoinduced h + results in an effective carriers separation.

Facile Preparation of Highly Active CO2 Reduction (001)TiO2/Ti3C2Tx Photocatalyst from Ti3AlC2 with Less Fluorine

To date, (001)TiO2/Ti3C2Tx hybridized photocatalyst is usually prepared through the complicated treatment of Ti3AlC2 in the presence of corrosive fluorine with a molar ratio of nF:nTi of more than 20. To reduce the use of corrosive fluorine, herein, exploiting beyond the conventional method, we report a facile synthetic method for (001)TiO2/Ti3C2Tx, elaborately using HF as both an etchant for Al elimination and a morphology control agent for the growth of (001)TiO2 nanosheets, with a sharply diminished use of fluorine (nF:nTi = 4:1) and simplified operation procedures. After optimization, the resulting (001)TiO2/Ti3C2Tx heterojunction exhibited markedly high photocatalytic activity with the CO2 reduction rate of 13.45 μmol g−1 h−1, which even surpasses that of P25 (10.95 μmol g−1 h−1), while the photoelectron selectivity to CH4 is approaching 92.84%. The superior photoactivity is interpreted as the fact that Ti3C2Tx with a lower work function induces photoinduced hole transfer and suppresses the charge recombination, thus facilitating the CO2 multi-electron reduction. This study provides a novel and simple synthesis for (001)TiO2/Ti3C2Tx towards sustainable energy transformations.

Simultaneous growth strategy for constructing a Cu–Fe/carboxylate-decorated carbon composite with improved interface compatibility and charge transfer to boost the visible photocatalytic degradation of tetracycline

Developing efficient photocatalysts for the oxidative degradation of recalcitrant pharmaceutical pollutants is significant and challenging. In this study, a simultaneous growth strategy was proposed to construct an interpenetrating-structured Cu–Fe/carboxylate-decorated carbon (CDC) composite by the one-pot hydrothermal carbonization of a mechanical activation (MA)-treated precursor (starch, FeCl3, and CuCl2) in the presence of a carboxylate. The as-prepared MA-Cu–Fe/CDC composite was used as a highly active photocatalyst for effectively degrading tetracycline (TC), owing to the columnar-structured Cu–Fe-based components, improved interface compatibility, and increased oxygen vacancy concentration. This promoted the utilization efficiency of visible light, charge transfer, and separation of photoinduced holes–electrons, thus effectively boosting the photocatalytic activity. As abundant active radicals were generated by MA-Cu–Fe/CDC under visible light irradiation, 100% of TC was removed after 50 min (kinetic rate constant of 0.092 min−1), and a mineralization ratio of 85.4% was achieved after 180 min. The photocatalytic degradation of TC was a gradual detoxification process. Moreover, MA-Cu–Fe/CDC maintained good photocatalytic activity after five cycles (TC removal of 98.9%), with almost no change in the surface chemical structure and a low leaching rate of metal ions owing to its excellent structural stability. This efficient and stable visible light-driven photocatalyst can potentially be used for constructing a photocatalytic degradation system for the sustainable and energy-conserving treatment of organic contaminants.