Separation Of Photoexcited Carriers Research Articles

Competing Activation and Deactivation Mechanisms in Photodoped Bismuth Oxybromide Nanoplates Probed by Single-Molecule Fluorescence Imaging.

Oxygen vacancies in semiconductor photocatalysts play several competing roles, serving to both enhance light absorption and charge separation of photoexcited carriers as well as act as recombination centers for their deactivation. In this Letter, we show that single-molecule fluorescence imaging of a chemically activated fluorogenic probe can be used to monitor changes in the photocatalytic activity of bismuth oxybromide (BiOBr) nanoplates in situ during the light-induced formation of oxygen vacancies. We observe that the specific activities of individual nanoplates for the photocatalytic reduction of resazurin first increase and then progressively decrease under continuous laser irradiation. Ensemble structural characterization, supported by electronic-structure calculations, shows that irradiation increases the concentration of surface oxygen vacancies in the nanoplates, reduces Bi ions, and creates donor defect levels within the band gap of the semiconductor particles. These combined changes first enhance photocatalytic activity by increasing light absorption at visible wavelengths. However, high concentrations of oxygen vacancies lower the photocatalytic activity both by introducing new relaxation pathways that promote charge recombination before photoexcited electrons can be extracted and by weakening binding of resazurin to the surface of the nanoplates.

Photocatalytic degradation of naphthalene on CeVO4 nanoparticles under visible light

Various morphologies and structure properties of CeVO4 photocatalysts were prepared via ethylene glycol (EG)-aided hydrothermal method and characterized by XRD, SEM, EDX, TEM, XPS, UV–Vis diffuse reflectance, PL emission and transient photocurrent responses, respectively. The influence of EG content on morphology and structure of as-prepared samples was examined as regard the photodegradation performance of naphthalene (Nap) in natural seawater. The results showed that Ce2 (CeVO4) sample with 10 mL EG addition exhibited the highest photodegradation efficiency of Nap, because the fusiform morphology of Ce2 sample favoredthe transportation of visible light and the separation of photoexcited carriers. In addition, the possible intermediate products were detected by FTIR, 3D fluorescence and GC–MS and the results showed only one mechanism of Nap direct conversion to CO2 and H2O was include in the photocatalytic reaction by Ce2 sample. The active species were detected by ESR and trapping experiments and the results showed that ∙OH played a more significant role in the photochemical degradation. Finally, the possible photodegradation mechanism of Nap over Ce2 sample was proposed on the basis of intermediate products and the active species formed in photodegradation process, and Ce4+/Ce3+ redox centers of Ce2 sample was performed under the irradiation of visible light.

Experimental and Theoretical Study into Interface Structure and Band Alignment of the Cu2Zn1-x Cd x SnS4 Heterointerface for Photovoltaic Applications.

To improve the constraints of kesterite Cu2ZnSnS4 (CZTS) solar cell, such as undesirable band alignment at p–n interfaces, bandgap tuning, and fast carrier recombination, cadmium (Cd) is introduced into CZTS nanocrystals forming Cu2Zn1–xCdxSnS4 through cost-effective solution-based method without postannealing or sulfurization treatments. A synergetic experimental–theoretical approach was employed to characterize and assess the optoelectronic properties of Cu2Zn1–xCdxSnS4 materials. Tunable direct band gap energy ranging from 1.51 to 1.03 eV with high absorption coefficient was demonstrated for the Cu2Zn1–xCdxSnS4 nanocrystals with changing Zn/Cd ratio. Such bandgap engineering in Cu2Zn1–xCdxSnS4 helps in effective carrier separation at interface. Ultrafast spectroscopy reveals a longer lifetime and efficient separation of photoexcited charge carriers in Cu2CdSnS4 (CCTS) nanocrystals compared to that of CZTS. We found that there exists a type-II staggered band alignment at the CZTS (CCTS)/CdS interface, from cyclic voltammetric (CV) measurements, corroborated by first-principles density functional theory (DFT) calculations, predicting smaller conduction band offset (CBO) at the CCTS/CdS interface as compared to the CZTS/CdS interface. These results point toward efficient separation of photoexcited carriers across the p–n junction in the ultrafast time scale and highlight a route to improve device performances.

Noble-metal-free Ni2P modified step-scheme SnNb2O6/CdS-diethylenetriamine for photocatalytic hydrogen production under broadband light irradiation

Step-scheme (S-scheme) photocatalytic system has been considered as an effective method for solar energy conversion by utilizing broadband solar energy, realizing easy separation of photoexcited carriers and strong redox ability. Herein, the novel ternary Ni2P cocatalysted two-dimensional (2D)/2D SnNb2O6/CdS-diethylenetriamine (SNO/CdS-D) system was designed and fabricated. The S-scheme SNO/CdS-D heterostructure gives photocatalytic hydrogen production of 7808 μmol g−1 h−1, which is about 130.13 and 2.35 times stronger than that of SNO and CdS-D. Further, noble-metal-free Ni2P cocatalyst is decorated into SNO/CdS-D heterostructure, the photocatalytic hydrogen evolution performance could be enhanced to 11,992 μmol g−1 h−1. Additionally, XPS analysis and DFT calculation revealed the carriers moves from CdS-D to SNO and then to Ni2P in the Ni2P-SNO/CdS-D nanocomposite. This work will give a reliable and clear insight into the interface and surface design of the 2D catalysts and offer a broadband photocatalytic hydrogen evolution process without noble metal cocatalysts.

Enhanced photoexcited carrier separation in Ta3N5/SrTaO2N (1D/0D) heterojunctions for highly efficient visible light-driven hydrogen evolution

Tantalum nitride (Ta3N5) is one of the most promising photocatalysts for overall water splitting owing to its suitable band structure and high solar-to-hydrogen conversion efficiency. However, photocatalytic performance of pristine Ta3N5 is still restricted by its high recombination rate of photo-induced carriers. Building up a heterojunction at the semiconductor/semiconductor interface is an effective way to reduce the recombination rate of photoexcited carriers. In this work, a novel type II hetero-structured photocatalyst (denoted as Ta3N5/STON) composed of one-dimensional (1D) Ta3N5 nanorods and zero-dimensional (0D) SrTaO2N (STON) nanoparticles has been developed via a simple one-step nitridation of 1D Sr2KTa5O15 (SKTO) nanorods. Compared with pristine Ta3N5, STON and Ta3N5/STON (mix) composite, Ta3N5/STON (1D/0D) heterojunctions exhibit a remarkably enhanced hydrogen production rate (77.31 µmol h−1 g−1) under visible light irradiation, which is 386.6, 11.9 and 8.8 times higher than that of Ta3N5, STON and Ta3N5/STON (mix) composite, respectively. The unique 1D/0D structure in Ta3N5/STON heterojunction, as well as the intimate interface contact between Ta3N5 and SrTaO2N, fosters the spatial charge separation and transfer efficiency to a large extent, leading to an improved hydrogen evolution rate. Our work suggests a new strategy toward the rational design of 1D/0D heterojunction photocatalyst for efficient solar-to-hydrogen conversion.

Delayed Charge Recombination by Open‐Shell Organics: Its Application in Achieving Superb Photodetectors with Broadband (400–1160 nm) Ultrahigh Sensitivity and Stability

AbstractMonolayer transition‐metal dichalcogenides have inspired worldwide efforts in optoelectronic devices but real applications are hindered with their reduced optical absorption due to their atomically ultrathin signature. In this study, by utilizing their biradical nature such as excellent absorption coefficient, broad bandwidth from the ultraviolet to near‐infrared region, and small triplet–singlet energy gap, a series of helicene 5,14‐diaryldiindeno[2,1‐f:1′,2′‐j]picene (DDP) derivatives (1ab, 1ac, and 1bb) are integrated with monolayer MoS2 for extraordinary photodetector performance and outstanding stability. Via comprehensive time‐resolved studies, the interfacial charge‐transfer process from the DDPs to the MoS2 layer is evidenced by the stabilized exciton property of the organics (1ac)/MoS2 heterostructure. Significantly, the 1ac/MoS2 photodetector exhibits an ultrahigh photoresponsivity of 5 × 107 A W−1 and a fast response speed of 45 ms due to the highly efficient photoexcited carrier separation and the matched type‐II energy band alignment. The biradical 1ac/MoS2 hybrid photodetector shows no sign of degradation after one‐month operation. The results pave a new avenue for biradical based high‐performance and super‐broadband optoelectronic devices.

Synthesis of core/shell Ti/TiOx photocatalyst via single-mode magnetic microwave assisted direct oxidation of TiH2

Submicron core/shell Ti/TiOx photocatalyst is successfully synthesized via single-mode magnetic microwave (SMMW) assisted direct oxidation of planetary ball-milled TiH2. The thickness of TiOx shell including highly concentrated defects such as Ti3+ and/or oxygen vacancies is controllable in the range from 6 to over 18 nm by varying the treatment time in the SMMW assisted reaction. In addition to its quite narrow optical bandgap (1.34–2.69 eV) and efficient visible-light absorption capacity, the submicron Ti/TiOx particle exhibits superior photocatalytic performance towards H2 production from water under both UV and visible-light irradiation to compare with a commercial TiO2 photocatalyst (P-25). Such excellent performance can be achieved by the synergetic effect of enhancement in visible light absorption capacity and photo-excited carrier separation because of the highly concentrated surface defects and the specific Ti/TiOx core/shell structure, respectively.

Efficient separation of photoexcited carriers in a g-C3N4-decorated WO3 nanowire array heterojunction as the cathode of a rechargeable Li-O2 battery.

Utilization of solar energy is very important for alleviating the global energy crisis; however, solar-to-electric energy conversion in a compact battery is a great challenge. High charging overpotential of conventional aprotic Li-O2 batteries still restricts their practical application. Herein, we propose a photo-involved rechargeable Li-O2 battery to not only realize direct solar-to-electric energy conversion/storage but also address the overpotential issue. In this photo-involved battery system, the g-C3N4-decorated WO3 nanowire array (WO3@g-C3N4 NWA) heterojunction semiconductor is used as both the photoelectrode and oxygen electrode. Upon charging under visible-light irradiation, the photoexcited holes and electrons are in situ generated on the WO3@g-C3N4 NWA heterojunction cathode. The fabrication of the heterojunction can distinctly reduce the recombination rate between electrons and holes, while photon-generated carriers are effectively and quickly separated and then migrate under a large current density. The discharge product (Li2O2) can be oxidized to O2 and Li+ with a reduced charging voltage (3.69 V) by the abundant photoexcited holes, leading to high energy efficiency, good cycling stability and excellent rate capability. This newly photo-involved reaction scheme could open new avenues toward the design of advanced solar-to-electric energy conversion and storage systems.

Tunable Photocatalytic Water Splitting by the Ferroelectric Switch in a 2D AgBiP2Se6 Monolayer.

Photocatalytic water splitting is a promising technology to solve the energy crisis and provide renewable and clean energies. Recently, although numerous 2D materials have been proposed as the photocatalytic candidates, the strategies to effectively modulate photocatalytic reactions and conversion efficiency are still lacking. Herein, based on first-principles calculations, we show that the photocatalytic activities and energy conversion efficiency can be well tuned by ferroelectric-paraelectric phase transition of a AgBiP2Se6 monolayer. It is found that the AgBiP2Se6 monolayer has a higher potential and driving forces of photogenerated holes for water oxidation in the ferroelectric phase, but higher corresponding values of photogenerated electrons for the hydrogen reduction reaction in the paraelectric phase. Besides, the solar-to-hydrogen energy conversion efficiency is also tunable with the phase transition; it is up to 10.04% at the ferroelectric phase due to the better carrier utilization, but only 6.66% at the paraelectric phase. Moreover, the exciton binding energy is always smaller in the paraelectric state than that in the ferroelectric state, indicating that the ferroelectric switch could also make a directional adjustment to the photoexcited carrier separation. Our theoretical investigation not only reveals the importance of ferroelectric polarization on water splitting, but also opens an avenue to modify the photocatalytic properties of 2D ferroelectric materials via a ferroelectric switch.

Flexible Quasi-2D Perovskite/IGZO Phototransistors for Ultrasensitive and Broadband Photodetection.

Organic-inorganic hybrid perovskites (PVKs) have recently emerged as attractive materials for photodetectors. However, the poor stability and low electrical conductivity still restrict their practical utilization. Owing to the quantum-well feature of two-dimensional (2D) Ruddlesden-Popper PVKs (2D PVKs), a promising quasi-2D PVK/indium gallium zinc oxide (IGZO) heterostructure phototransistor can be designed. By using a simple ligand-exchange spin-coating method, quasi-2D PVK fabricated on flexible substrates exhibits a desirable type-II energy band alignment, which facilitates effective spatial separation of photoexcited carriers. The device exhibits excellent photoresponsivity values of >105 A W-1 at 457 nm, and broadband photoresponse (457-1064 nm). By operating the device in the depletion regime, the specific detectivity is found to be 5.1 × 1016 Jones, which is the record high value among all PVK-based photodetectors reported to date. Due to the resistive hopping barrier in the quasi-2D PVK, the device can also work as an optoelectronic memory for near-infrared information storage. More importantly, the easy manufacturing process is highly beneficial, enabling large-scale and uniform quasi-2D PVK/IGZO hybrid films for detector arrays with outstanding ambient and operation stabilities. All these findings demonstrate the device architecture here provides a rational avenue to the design of next-generation flexible photodetectors with unprecedented sensitivity.

Direct Growth of Perovskite Crystals on Metallic Electrodes for High-Performance Electronic and Optoelectronic Devices.

Metal halide perovskite has attracted enhanced interest for its diverse electronic and optoelectronic applications. However, the fabrication of micro- or nanoscale crystalline perovskite functional devices remains a great challenge due to the fragility, solvent, and heat sensitivity of perovskite crystals. Here, a strategy is proposed to fabricate electronic and optoelectronic devices by directly growing perovskite crystals on microscale metallic structures in liquid phase. The well-contacted perovskite/metal interfaces ensure these heterostructures serve as high-performance field effect transistors (FETs) and excellent photodetector devices. When serving as an FET, the on/off ratio is as large as 106 and the mobility reaches up to ≈2.3 cm2 V-1 s-1 . A photodetector is displayed with high photoconductive switching ratio of ≈106 and short response time of ≈4 ms. Furthermore, the photoconductive response is proved to be band-bending-assisted separation of photoexcited carriers at the Schottky barrier of the silver and p-type perovskites.

Rigorous design of outermost surface of TiO2 via one-step single-mode magnetic microwave field toward highly efficient visible-light photocatalyst

Among numerous efforts toward preparation of visible-light TiO2, recently design and control for chemical structure of TiO2 outermost surface have been paid strong attention to enhance photocatalytic performance. We have previously succeeded in direct synthesis of structurally well-controlled TiO2 with highly concentrated Ti3+ from metal titanium particle via single-mode magnetic microwave (SMMW)-assisted reactions. Here, we demonstrate synthesis of Ti3+ and interstitial nitrogen (Nint) co-doped TiO2 in Ar/O2/N2 system during one-step SMMW-assisted reactions, where chemical structure of outermost surface is rigorously controlled. In addition, such one-step-generated TiO2 shows significant thermal stability which has not been achieved in previously reported deficient TiO2 even through several step reactions. Additionally, the synthesized co-doped TiO2 with specific surface structures shows superior visible-light photocatalytic performance for photo-degradation of rhodamine B. The mechanism of outermost surface formation is systematically investigated by characterizations of XRD, XPS, UV–Vis absorption and PL. It demonstrates that the specific TiO2 surface including highly concentrated Ti3+ and Nint can be attributed to the rapid heat-dynamics during the reaction, which enhance the efficiency for separation of photo-excited carriers. The one-step SMMW-assisted reactions on metallic particle as bottom-up process will open new strategy for material design of functional metal oxides.

High-Responsivity Photovoltaic Photodetectors Based on MoTe2/MoSe2 van der Waals Heterojunctions

Van der Waals heterojunctions based on transition metal dichalcogenides (TMDs) show promising potential in optoelectronic devices, due to the ultrafast separation of photoexcited carriers and efficient generation of the photocurrent. Herein, this study demonstrated a high-responsivity photovoltaic photodetector based on a MoTe2/MoSe2 type-II heterojunction. Due to the interlayer built-in potential, the MoTe2/MoSe2 heterojunction shows obvious photovoltaic behavior and its photoresponse can be tuned by the gate voltage due to the ultrathin thickness of the heterojunction. This self-powered photovoltaic photodetector exhibits an excellent responsivity of 1.5 A W−1, larger than previously reported TMDs-based photovoltaic photodetectors. Due to the high-efficiency separation of electron-hole pairs and ultrafast charge transfer, the light-induced on/off ratio of current switching is larger than 104 at zero bias, and the dark current is extremely low (~10−13 A). These MoTe2/MoSe2 type-II heterojunctions are expected to provide more opportunities for future nanoscale optoelectronic devices.

Assembling Bi2MoO6/Ru/g-C3N4 for Highly Effective Oxygen Generation from Water Splitting under Visible-Light Irradiation.

Water oxidation is a kinetically challenging reaction for photocatalytic overall water splitting. Producing one molecule of O2 will consume four electrons, so it is an extremely difficult obstacle for researchers. Here, a Bi2MoO6/Ru/g-C3N4 composite was obtained by a gentle hydrothermal method, which could oxidize water into O2 highly efficiently. The optimal O2 production reached 328.34 μmol·g-1·h-1 under visible light irradiation. Moreover, the catalyst presented excellent stability, as shown by a still sustentative 91.4% photocatalytic activity and invariant textural structure after seven recycling tests. The ternary material had the smallest resistance, which indicated that it has a good photoelectron conductive tunnel, and a rapid transfer route is proposed through Bi2MoO6 → Ru → g-C3N4 → NaIO3 (electron acceptor). The massive holes (h+) with high oxidative potential are surely enriched due to the quick electron migration, being fit for a large promotion of the multiple-electron water oxidative proceedings. Therefore, the metallic Ru provided a powerful bridge for efficient transfer of the interface electrons which could be beneficial to spatial separation of photoexcited carriers without the loss of the high redox capacity. Finally, it is proposed that the Ru-assisted electron transport and constituent synergy in Bi2MoO6/Ru/g-C3N4 composite play crucial roles to its enhanced light utilization, efficient photoelectric conversion property, and high-producing oxygen capability.

Enhanced photocatalytic degradation of norfloxacin under visible light by immobilized and modified In2O3/TiO2 photocatalyst facilely synthesized by a novel polymeric precursor method

Ion co-doped photocatalysts with In2O3/TiO2 heterostructure (In2O3/TiO2(m)) were prepared through a new polymeric precursor method. The In2O3/TiO2(m) precursor solution is of salient advantage in coating photocatalysts on various substrates and multiple modifications. The photocatalysts were facilely obtained after the calcination of precursors. Mass ratio of In/Ti was optimized according to their photocatalytic performances, and IT(m)-3 (wIn/Ti = 3%, modified by N, B co-doping) showed the best photocatalytic activity. The band gap was successfully narrowed to 2.37 eV, and In2O3/TiO2 heterostructure was successfully constructed in the photocatalysts. Visible light absorption and separation of photoexcited carriers were significantly enhanced. Under visible light, NOX (20 mg/L in the water) was 100% photodegraded in 10 min, with 100% TOC removed in 25 min. The IT(m)-3-loaded quartz fabrics (ITQ) also showed excellent photocatalytic performance. The photocatalytic activity of ITQ was repeatable and stable in 45 rounds of recycle without centrifugation. Synergetic effect of heterostructure and element doping was considered contributing to the outstanding photocatalysis performance. The polymeric precursor method proposed in this work showed great potential in large-scale preparation and application of immobilized photocatalysts. The synergetic improvement through co-modifications showed its proper compatibility with modifications.

Synthesis of Fe2O3/TiO2 monoliths for the enhanced degradation of industrial dye and pesticide via photo-Fenton catalysis

In this work, magnetic Fe2O3/TiO2 monoliths were successfully synthesized through nanocasting method followed by wet impregnation for the removal of remazol brilliant red X-3BS (RbX) dye and widely used pesticide (Fipronil). The activity of such catalyst combined with the photo-Fenton catalysis was assayed under the UV light irradiation. The effect of various parameters such as pH, catalyst dosage, H2O2 concentration, pollutant concentration and treatment time were also investigated. The optimal pH value (pH 3), H2O2 concentration (60 mM) and catalyst dosage (2 g/L) leads the higher degradation efficiency of RbX (90.57%) within 180 min time. Whereas, it has been found that fipronil exhibited highest degradation efficiency of 88.71% at pH 3 using 10 mM of H2O2 concentration, 1.5 g/L of the catalyst in 120 min time. The Fe2O3/TiO2 monoliths showed remarkable photocatalytic activity as compared to Fe2O3 and TiO2 monoliths. This is attributed to the fact that TiO2 combined with Fe2O3 leads to the effective separation of photo excited carriers which result better degradation efficiency. The kinetics of RbX and fipronil degradation by supported Fe2O3/TiO2 monoliths followed the first-order mechanism. Moreover, synthesized monoliths showed excellent stability and reusability for four cycles of degradation. In addition, the monolithic Fe2O3/TiO2 photo-catalyst can be easier to recover after the treatment process which is more relevant to the practical application point of view.

One-step low-temperature synthesis of 0D CeO2 quantum dots/2D BiOX (X = Cl, Br) nanoplates heterojunctions for highly boosting photo-oxidation and reduction ability

0D/2D heterojunctions, especially quantum dots (QDs)/nanoplates have attracted noteworthy attention for use of the high charge mobility of photoinduced electrons and holes. Herein, we report a novel one-step low-temperature route for the controlled synthesis of CeO2 QDs/BiOX (X = Cl, Br) nanoplates heterojunctions with the self-created in-built Ce4+/Ce3+ redox centers. The as-prepared heterojunctions exhibited outstanding photocatalytic abilities not only for the oxidation of tetracycline (TC) but also for the reduction of hexavalent chromium (Cr6+) although under 5 W white LED light irradiation. The considerably enhanced capabilities were attributed to the improvement of light absorption and the highly effective transfer and separation of photoexcited carriers, which encouraged by the strong synergistic effects of inner Ce4+/Ce3+ redox centers and the formation of intimately contacted interface between CeO2 QDs and BiOX nanoplates. Meanwhile, the likely degradation pathway of TC was proposed on the basis of the intermediate products detected by GC–MS, and the appearance photocatalytic mechanisms were also discussed in detail. This work could open new possibilities to provide some insight into a facile, energy saving and environmental friendly pathway for synthesizing versatile 0D/2D Bi-based heterojunction materials with high photocatalytic performance.

Two-dimensional Janus heterostructures for superior Z-scheme photocatalytic water splitting

Developing robust water splitting photocatalyst remains a pivot challenge for solar-to-fuel conversion. Herein, two-dimensional (2D) Janus bilayer heterostructures are reported by sulfur-vacancy-confined-in ZnIn2S4 (Vs-ZnIn2S4) and WO3 nanosheets as an all-solid-state Z-scheme prototype. First-principle calculations and experimental observations clearly confirm the spontaneous formation of this redox-mediator-free Z-scheme van der Waals heterostructure at atomic level, not only facilitating the space separation of photoexcited carriers with high charge density, enhancing charge dynamics and optimizing charge lifetime, but also accumulating electrons in conduction band of Vs-ZnIn2S4 and holes in valence band of WO3 by internal electric field through W–S bonds. After integrated by NiS quantum dots, novel 2D/2D NiS/Vs-ZnIn2S4/WO3 heterostructures with high stability exhibited an outstanding visible-light hydrogen evolution rate of 11.09 mmol g−1 h−1 and an apparent quantum efficiency about 72% at 420 nm, the highest value so far reported among the family of ZnIn2S4 photocatalysts. This work not only presents novel Janus heterostructures but also paves the atomic-level structural and interfacial design and the construction of 2D Janus bilayer Z-scheme heterojunctions for solar energy conversion applications.

WC1−x‐Coupled 3D Porous Defective g‐C3N4 for Efficient Photocatalytic Overall Water Splitting

Constrained by the limited visible light harvesting and high photogenerated electron‐hole pair recombination rate, pristine g‐C3N4 typically possesses poor overall water splitting behavior under visible light. To achieve efficient overall water splitting of g‐C3N4 without the assistance of precious metals, herein, a WC1−x‐coupled 3D porous defect g‐C3N4 is constructed through simple one‐step pyrolysis. Due to the introduction of platinum‐like WC1‐x, the effective heterogenization of WC1−x/g‐C3N4 greatly improves the charge separation. In the meanwhile, the 3D multiple microstructures established by the self‐protocol of ultrathin 2D g‐C3N4 nanosheets enhance the light absorption efficiency and optimize the separation of photoexcited carriers. Significantly, the generation of nitrogen defects is capable of bringing about an optimized band structure. Based on those modifications, a significant photocatalytic overall water splitting capacity under visible light is obtained without the sacrificial agent by the prepared 3D WC1−x/g‐C3N4, in which the simultaneous evolution of H2 and O2 was up to 84.1 and 41.7 µmol h−1 g−1, respectively.

Facile synthesis of Bi-modified Nb-doped oxygen defective BiOCl microflowers with enhanced visible-light-driven photocatalytic performance

Bi-modified Nb-doped oxygen defective BiOCl hierarchical microflowers were synthesized through a facile one-pot solvothermal route. The prepared photocatalysts were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicated that the modified BiOCl appeared as hierarchical microflowers composed of nano sheets. The BiOCl synthesized with Nb/Bi = 1:7 in precursor solutions exhibited the best photocatalytic performance for Rhodamine B (RhB) and Tetracycline (TC) degradation under visible light irradiation. Compared with the BiOCl fabricated through a hydrothermal method, the counterpart with oxygen vacancies (OVs) had a better visible-light-driven photocatalytic activity, and the kinetics constant k for the degradation of RhB increased by 728% (525% for TC). After the modification of Bi0 and Nb5+, the constant k further increased by 134% and 82%, respectively, for the degradation of RhB and TC. This enhanced photocatalytic activity was attributed to both the improved visible light absorption caused by the introduction of OVs and the highly efficient separation of photoexcited carriers resulted from Nb5+ doping and Bi0 deposition. Trapping experiments revealed that the photogenerated hole was the dominating active species. This work provides a new facile strategy for the synthesis of visible-light-driven photocatalysts with high performance.