Efficient Photoinduced Charge Separation Research Articles

Promoted Charge Separation and Long-Lived Charge-Separated State in Porphyrin-Viologen Dyad Nanoparticles.

Developing light-harvesting systems with efficient photoinduced charge separation and long-lived charge-separated (CS) state is desirable but still challenging. In this study, we designed a zinc porphyrin photosensitizer covalently linked with viologen (ZnP-V) that can be prepared into nanoparticles in aqueous solution. In DMF solution, the monomeric ZnP-V dyads show no electron transfer between the ZnP and viologen units. In contrast, the ZnP-V nanoparticles in aqueous solution show fast charge separation with a CS state lifetime of up to 4.3 ms. This can be attributed to charge hopping induced by aggregation or distance modification between the donor and acceptor induced by electronic interaction. Nevertheless, the lifetime of the CS state is orders of magnitude longer than for molecular aggregates reported previously. The ZnP-V nanoparticles show enhanced photocatalytic hydrogen production as compared to the ZnP nanoparticles and still hold promise for other applications such as photovoltaic devices and photoredox catalysis.

Tailoring Morphology in Hydrothermally Synthesized CdS/ZnS Nanocomposites for Extraordinary Photocatalytic H2 Generation via Type-II Heterojunction

CdS@ZnS core shell nanocomposites were prepared by a one-pot hydrothermal route. The morphology of the composite was tuned by simply changing the Zn2+ precursor concentration. To characterize the samples prepared, various techniques were employed, including XRD, FESEM, TEM, XPS and UV-vis DRS. The band gaps of CdS and ZnS were measured to be 2.26 and 3.32 eV, respectively. Compared with pure CdS, the CdS@ZnS samples exhibited a slight blue shift, which indicated an increased band gap of 2.29 eV. The CdS@ZnS core shell composites exhibited efficient photocatalytic performance for H2 generation under simulated sunlight illumination in contrast to pure CdS and ZnS. Additionally, an optimized H2 generation rate (14.44 mmol·h−1·g−1cat) was acquired at CdS@ZnS-2, which was approximately 4.6 times greater than that of pure CdS (3.12 mmol·h−1·g−1cat). Moreover, CdS@ZnS heterojunction also showed good photocatalytic stability. The process of charge separation over the photocatalysts was investigated using photoelectrochemical analysis. The findings indicate that the CdS@ZnS nanocomposite has efficient charge separation efficiency. The higher H2 generation activity and stability for CdS@ZnS photocatalysts can be attributed to the intimate interface in the CdS@ZnS core–shell structure, which promoted the light absorption intensity and photoinduced charge separation efficiency. It is expected that this study will offer valuable insights into the development of efficient core shell composite photocatalysts.

Novel Bi2WO6/MWCNT nanohybrids synthesis for high-performance photocatalytic activity of ciprofloxacin degradation under simulated sunlight irradiation

In this research, novel Bi2WO6/MWCNT nanohybrids were synthesized via a cost-effective hydrothermal route. The photocatalytic performance of these specimens was tested through the photodegradation of Ciprofloxacin (CIP) under simulated sunlight. Various physicochemical techniques systematically characterized the prepared pure, Bi2WO6/MWCNT nanohybrid photocatalysts. The XRD and Raman spectra revealed the structural/phase properties of Bi2WO6/MWCNT nanohybrids. FESEM and TEM pictures revealed the attachment and distribution of plate-like Bi2WO6 nanoparticles along the nanotubes. The optical absorption and bandgap energy of Bi2WO6 was affected by the addition of MWCNT, which was analyzed by UV-DRS spectroscopy. The introduction of MWCNT reduces the bandgap value of Bi2WO6 from 2.76 to 2.46 eV. The BWM-10 nanohybrid showed superior photocatalytic activity for CIP photodegradation; 91.3% of CIP was degraded under sunlight irradiation. The PL and transient photocurrent test confirm that photoinduced charge separation efficiency is better in BWM-10 nanohybrids. The scavenger test indicates that h+ & •O2 have mainly contributed to the CIP degradation process. Furthermore, the BWM-10 catalyst demonstrated outstanding reusability and firmness in four successive cycles. It is anticipated that the Bi2WO6/MWCNT nanohybrids will be employed as photocatalysts for environmental remediation and energy conversion. This research presents a novel technique for developing an effective photocatalyst for pollutant degradation.

One-step hydrothermal synthesis of S-scheme heterojunction Bi2O3/Bi2Sn2O7 composites with enhanced photocatalytic CO2 reduction performance

In this study, a kind of S-scheme heterojunction Bi2O3/Bi2Sn2O7 composite material is firstly prepared by one-step hydrothermal method through adjusting the molar amount of Bi source, which further improves the photocatalytic CO2 reduction performance compared with pure Bi2Sn2O7. Combined with work-enthalpy data using density functional theory calculations, the photoexcited electrons are directionally transferred from Bi2O3 to Bi2Sn2O7 for the formation of S-scheme mechanism, achieving the significant improvement in the photoinduced charge separation efficiency and CO2 photoreduction activity to CO for as-prepared Bi2O3/Bi2Sn2O7 composite. A feasible photocatalytic CO2 reduction mechanism of S-scheme heterojunction Bi2O3/Bi2Sn2O7 composite is proposed and investigated. Our findings should provide the significant theoretical guidance and experimental data for achieving the S-scheme heterojunction construction and CO2 green conversion into low-carbon chemical fuels.

A Photosensitizing Metal–Organic Framework as a Tandem Reaction Catalyst for Primary Alcohols from Terminal Alkenes and Alkynes

AbstractOwing to the wide and growing demand for primary alcohols, the development of efficient catalysts with high regioselectivity remains a worthwhile pursuit. However, according to Markovnikov's rule, it is a challenge to obtain primary alcohols with high yields and regioselectivity from terminal alkenes or alkynes. Herein, we report the synthesis of a photosensitizing two‐dimensional (2D) metal–organic framework (MOF) from cyclic trinuclear copper(I) units (Cu‐CTUs) and a boron dipyrro‐methene (Bodipy) ligand. The MOF features broadband light absorption, excellent photoinduced charge separation efficiency, and photochemical properties. By integrating the copper‐catalyzed hydroboration and photocatalyzed aerobic oxidation, it can catalyze terminal alkenes and alkynes to produce primary alcohols via a one‐pot tandem reaction with excellent regioselectivity, good overall yields in two‐step reactions (up to 85 %), broad substrate compatibility (32 examples) and good reusability under mild conditions.

A Photosensitizing Metal-Organic Framework as a Tandem Reaction Catalyst for Primary Alcohols from Terminal Alkene and Alkyne.

Due to the wide and growing demand for primary alcohols, the development of efficient catalysts with high regioselectivity remains a worthwhile pursuit. However, according to the Markovnikov's rule, it is challenge to obtain primary alcohols with high yields and regioselectivity from terminal alkenes or alkynes. Herein, we reported the synthesis of a photosensitizing two-dimensional (2D) metal-organic framework (MOF) from cyclic trinuclear copper(I) units (Cu-CTUs) and boron dipyrro-methene (Bodipy) ligand. The MOF features broadband light absorption, excellent photoinduced charge separation efficiency, and photochemical properties. By integrating the copper-catalyzed hydroboration and photocatalyzed aerobic oxidation, it can catalyze terminal alkenes and alkynes to produce primary alcohols via one-pot tandem reaction with excellent regioselectivity, good overall yields in two-step reactions (up to 85%), broad substrate compatibility (32 examples) and good reusability under mild conditions.

Construction of CuBi2O4/CdO p-n buried junction for boosted photoelectrochemical water splitting

The rational design and construction of interface heterostructures, which can simultaneously accelerate the photoinduced carrier separation and enhance the surface hydrogen evolution kinetics, is of great necessity for photoelectrochemical (PEC) water splitting. Here we construct a CuBi2O4/CdO p-n buried junction for boosting the PEC hydrogen evolution. Compared to the bare CuBi2O4 photocathode, the CuBi2O4/CdO heterojunction reveals an anodic shift of 170 mV for the onset potential and achieves a cathodic photocurrent density of 0.32 mA cm−2 at 0.4 V vs. RHE, as well as improved long-term stability under AM 1.5 G illumination without sacrificial reagent. The experimental characterizations and theoretical calculations confirm the significance of the CuBi2O4/CdO p-n junction in increasing the photoinduced charge separation efficiency and reducing the activation energy of hydrogen evolution reaction (HER), which accounts for enhanced PEC performance. Meanwhile, the change of photoexcited charge-transition route evidenced by DFT calculation in CuBi2O4/CdO provides the fundamental explanation for spatial charge separation, which is responsible for the improved PEC hydrogen evolution stability. The present work highlights the importance of constructing heterojunctions to boost the PEC performance and elucidates the probable intrinsic mechanism involved in the interface.

Design of AIEgen‐based porphyrin for efficient heterogeneous photocatalytic hydrogen evolution

AbstractTetraphenylethylene (TPE)‐conjugated porphyrin TPE‐ZnPF is synthesized in high yield and characterized by single‐crystal X‐ray diffraction. The propeller‐shaped TPE groups not only enable exceptional aggregation‐induced emission (AIE) in the solid state but also abolish the strong π‐π stacking of porphyrin moieties and thus prohibit aggregation‐caused quenching (ACQ). TPE‐ZnPF aggregates feature long‐lived photoexcited states, which subsequently suppress non‐radiative decay channels and enhance emission intensity. Moreover, its aggregates show more efficient light‐harvesting ability due to the Förster resonance energy transfer from the TPE energy donor to the porphyrin core energy acceptor, well‐defined nanosphere morphology, and more efficient photoinduced charge separation than the porphyrin Ph‐ZnPF, which possesses ACQ and agglomerated morphology. As a result, an excellent photocatalytic hydrogen evolution rate (ηH2) of 56.20 mmol g‒1 h‒1 is recorded for TPE‐ZnPF aggregates, which is 94‐fold higher than that of the aggregates of Ph‐ZnPF (0.60 mmol g‒1 h‒1) without the TPE groups.

Facile synthesis of Z-scheme CeO2@AgBr heterojunction for improved dye degradation

CeO2 nanorods were synthesized by the hydrothermal method and coupled with AgBr via deposition approach. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmet-Teller (BET) and diffuse reflection spectroscopy (DRS) were used to characterize the structure, morphology and optical properties of the samples. The photoinduced charge separation efficiency was determined by transient photocurrent response and photoluminescence (PL) spectra. The effect of CeO2 loading on the Rhodamine B (RhB) degradation in CeO2@AgBr composites was also investigated. The results indicated that 40 wt%-CeO2@AgBr photocatalyst demonstrated the highest photocatalytic activity than pure CeO2 and AgBr. The trapping experiment showed that holes (h+) and superoxide radicals (•O2−) were the main active species for the degradation of RhB. The improved photocatalytic activity of CeO2@AgBr catalysts were attributed to the formation of Z-scheme heterojunction, which effectively inhibited the recombination of photoinduced electron-hole pairs.

Revealing the Role of Donor/Acceptor Interfaces in Nonfullerene-Acceptor Based Organic Solar Cells: Charge Separation versus Recombination.

Organic solar cells (OSCs) based on nonfullerene-acceptors (NFAs) have achieved rapid development, while the role of donor/acceptor (D/A) interfaces in NFA based heterosystems has not been fully addressed. Here, we clarify that the photoinduced spontaneous charge separation efficiency in typical NFA heterosystems can reach up to 67%, and the charge separation efficiency contributed by the D/A interface is only 25%. The more important role of D/A interfaces is reducing the charge recombination rate, especially optimizing the competition between radiative and nonradiative charge recombination, thus reducing the nonradiative voltage loss. Systematical simulations demonstrate that there exists an optimal interfacial distance for a fixed energy offset, at which the D/A interface can reduce the nonradiative voltage loss by a maximum value of 0.12 V. Hence, we propose that optimizing the interfacial distance combined with the actual interfacial energy offset of a given heterosystem is important to develop its best photovoltaic performance.

Cation exchange synthesis of hollow-structured cadmium sulfide for efficient visible-light-driven photocatalytic hydrogen evolution

Efficient solar absorption and photoinduced charge separation are extremely important for solar-energy conversion on semiconductor photocatalysts. To advance the photocatalytic performance, we developed a general templated-assisted reverse cation exchange strategy to successfully synthesize hollow-structured CdS semiconductors with the textile structural surface. The crystal phase, particle morphology, optical/electrical properties, and photocatalytic performance of the as-syntheszied sample are investiagted by XRD, SEM, TEM, XPS, DSR, PL, ESR photoelectrochemical measurements, and Photocatalytic H2 evolution test. The final CdS sample exhibits an enhanced photocatalytic hydrogen evolution rate of up to 965 μmol·g−1 h−1, 2.8 times higher than the reported CdS nanorods. Based on the experimental and characterization results, the improved photocatalytic activity of the cadmium sulfide semiconductor can be ascribed to the special hollow cubic structure with a thin shell, which can enhance the light-harvesting ability and provide abundant photocatalytic active sites for facilitating the separation of photogenerated electron/hole pairs. This synthetic strategy may pave a new path for the rational design of efficient sulfur-based semiconductor photocatalysts for solar driven H2 production.

G-C3N4/ZnWO4 nanocomposites as efficient and stable S-scheme photocatalysts for hydrogen evolution

The use of photocatalysis to decompose water and produce hydrogen (H2) is a promising green energy technology with numerous potential applications. In this study, the design of g-C3N4/ZnWO4 (CN/ZWO) accompanied by an “S-scheme” heterojunction mechanism is reported for the first time, along with a thorough investigation of their photocatalytic H2 evolution activity and mechanism. It was found that the CN/ZWO nanocomposites effectively address the inherent issues of band gap defects, instability, and poor H2-evolving photocatalytic performance of pure CN. The CN/ZWO-0.15 in particular exhibited particularly high photocatalytic activity (1.195 mmol g−1 h−1), being 17.57 and 7.71 times more effective than pure CN and ZWO, respectively. In addition, the CN/ZWO-0.15 displayed good stability over a period of 12 h (four cycles) while maintaining its high activity. The presence of the nanocomposites was confirmed using TEM and in situ irradiated XPS (ISI-XPS), and the mechanism at the heterojunction was determined to be the S-scheme via ISI-XPS, EPR and theoretical calculations. The S-scheme mechanism involves the effective utilization of the valence-conduction band gap width of the system and the efficient photoinduced charge separation, and is believed to be responsible for the superior H2 release ability of the nanocomposites. This work presents a novel approach involving an S-scheme heterojunction to overcome the intrinsic defects of CN-based photocatalysts.

Hollow core-shell LDH@N-HCS/CN S-scheme photocatalyst with the enhanced visible-light activity

It is a great challenge to effectively increase the charge separation and active sites of earth-abundant graphitic carbon nitride (CN) semiconductors to improve the photocatalytic performance. Looking for a highly active cocatalyst has attracted attention because of their potential to resolve the issues of low charge separation and low specific surface area of CN. A core-shell cocatalyst composed of nitrogen doped hollow carbon spheres (N-HCS) as the core and LDH nanoplates as the photoactive shell has been designed to increase the pristine CN active sites and charge separation. N-HCS acted as the support for LDH nanoplates to prevent particle agglomeration and served as the fast electron transfer channels to enhance the photoinduced charge separation efficiency. The ternary nanocomposites exhibited superior activity for nonyl phenol and Acid Blue 92 degradation compared to the unmodified CN under the visible light. The optimized deposition of LDH@N-HCS (15 wt%) on the CN surface resulted in 7-fold higher activity than without the cocatalyst. The improved photocatalytic activity of the ternary composite compared to CN could be attributed to two factors: efficient electron-hole pair separation due to LDH nanoplates and CN interface, and the presence of the N-HCS as an electron collector. The porous hollow structure of the cocatalyst exposes the numerous surface-active sites that favor visible light photocatalytic performance and supplies multiple reflection of photons into the cavity, increasing the usage ratio of light. This work will supply a novel strategy to rationally fabricate a noble metal-free binary cocatalyst for efficient visible light activity.

Carbon dots-embedded amorphous nickel oxide for highly enhanced photocatalytic redox performance.

Amorphous materials reveal promising prospects in photocatalysis for the abundant active sites and tunable electronic configuration due to the lattice flexibility. However, the intrinsic lattice distortion could also cause the self-trapping effect and results in the recombination of photogenerated carriers. This disadvantage could be modified by the small size of amorphous domains for reducing charge migration distance. For this purpose, carbon dots (CDs) are introduced as the heterogeneous nucleus to regulate the configuration and composition of the amorphous nickel oxides for efficient utilization of photocarriers in catalytic reactions. The resultant nanocomposites a-NiOx/CDs show the densely distributed CDs embedded in the amorphous nickel oxide with dual valences of Ni2+ and Ni3+, and they reveal superior activities in photocatalytic oxidation and reduction compared with the single amorphous nickel oxide. The extraordinary photocatalytic performance is attributed to the synergetic function of their excellent separation efficiency of photoinduced charges and the cyclic conversion between Ni2+ and Ni3+ in the defects. This work provides inspiration for the modification and photocatalytic application of the amorphous materials.

Piperazine-Linked Metalphthalocyanine Frameworks for Highly Efficient Visible-Light-Driven H2O2 Photosynthesis.

Artificial photosynthesis of H2O2 from O2 reduction provides an energy-saving, safe, and green approach. However, it is still critical to develop highly active and selective 2e- oxygen reduction reaction photocatalysts for efficient H2O2 production owing to the unsatisfactory photosynthesis productivity. Herein, two new two-dimensional piperazine-linked CoPc-based covalent organic frameworks (COFs), namely, CoPc-BTM-COF and CoPc-DAB-COF, were afforded from the nucleophilic substitution reaction of hexadecafluorophthalocyaninato cobalt(II) (CoPcF16) with 1,2,4,5-benzenetetramine (BTM) or 3,3'-diaminobenzidine (DAB). Powder X-ray diffraction analysis in combination with electron microscopy and a series of spectroscopic technologies reveals their crystalline porous framework with a fully conjugated structure and eclipsed π-stacking model. Ultraviolet-visible diffuse reflectance absorption spectra unveil their excellent light absorption capacity in a wide range of 400-1000 nm. This, together with their enhanced photo-induced charge separation and transport efficiency as disclosed by photocurrent response and photoluminescence measurements, endows the as-prepared piperazine-linked CoPc-based COFs with superior photocatalytic activity toward O2-to-H2O2 conversion under visible-light irradiation (λ > 400 nm). In particular, CoPc-BTM-COF exhibits a record-high H2O2 yield of 2096 μmol h-1 g-1 among the COF-based photocatalysts and an impressive apparent quantum yield of 7.2% at 630 nm. The present result should be helpful for fabricating high-performance and low-cost photocatalysts for visible-light-driven H2O2 photosynthesis.

Accelerated Decoloration of Organic Dyes from Wastewater Using Ternary Metal/g-C3N4/ZnO Nanocomposites: An Investigation of Impact of g-C3N4 Concentration and Ni and Mn Doping

Wastewater from many sectors that contains hazardous organic pollutants exacerbates environmental contamination. Consequently, outstanding photocatalytic substances that can successfully degrade hazardous substances are needed to provide pollution-free water. From this perspective, zinc oxide/g-C3N4-based composites are desirable due to their low cost, strong reactivity, and environmental friendliness. So, in the current investigation, sequences of Mn/g-C3N4/ZnO (Mn/GZ) and Ni/g-C3N4/ZnO (Ni/GZ) nanocomposites (NCs) containing different concentrations (wt.%) of g-C3N4 were made via the co-precipitation process. The chemical makeup and morphological characteristics of the produced composites were ascertained via the techniques of transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Fourier transform infrared (FTIR), photoluminescence (PL), and UV spectrophotometry. Methyl orange (MO) and Eriochrome Black T (EBT) dyes were used as target pollutants to assess the composite materials’ photocatalytic effectiveness. Compared to g-C3N4/ZnO and g-C3N4, the produced Mn/GZ and Ni/GZ NCs displayed better photocatalytic activity. The improved photocatalytic efficiency of the Ni/GZ and Mn/GZ NCs might be credited to synergistic interactions at the g-C3N4 and ZnO interface that result in a more efficient separation and conduction of photo-induced charges. Furthermore, the Ni/Mn atoms act as the facilitators to improve electron–hole pair separation and conduction in NCs. The nanocomposites were found to be incredibly stable, with consistently high dye decoloration efficiency over five catalytic cycles. Hence, Ni/GZ and Mn/GZ could potentially be very effective and adaptable photocatalysts for the photocatalytic decoloration of wastewater pollutants.

Construction of a Well-Defined S-Scheme Heterojunction Based on Bi-ZnFe2O4/S-g-C3N4 Nanocomposite Photocatalyst to Support Photocatalytic Pollutant Degradation Driven by Sunlight

Currently, organic dyes and other environmental contaminants are focal areas of research, with considerable interest in the production of stable, high-efficiency, and eco-friendly photocatalysts to eliminate these contaminants. In the present work, bismuth-doped zinc ferrite (Bi-ZnFe2O4) nanoparticles (NPs) and bismuth-doped zinc ferrites supported on sulfur-doped graphitic carbon nitride (Bi-ZnFe2O4/S-g-C3N4) (BZFG) photocatalysts were synthesized via a hydrothermal process. SEM, XRD, and FTIR techniques were used to examine the morphological, structural, and bonding characteristics of the synthesized photocatalysts. The photocatalytic competence of the functional BZFG nanocomposites (NCs) was studied against MB under sunlight. The influence of Bi (0.5, 1, 3, 5, 7, 9, and 11 wt.%) doping on the photocatalytic performance of ZnFe2O4 was verified, and the 9%Bi-ZnFe2O4 nanoparticles exhibited the maximum MB degradation. Then, 9%Bi-ZnFe2O4 NPs were homogenized with varying amounts of S-g-C3N4 (10, 30, 50, 60, and 70 wt.%) to further enhance the photocatalytic performance of BZFG NCs. The fabricated Bi-ZnFe2O4/30%S-g-C3N4 (BZFG-30) composite outperformed ZnFe2O4, S-g-C3N4 and other BZFG NCs in terms of photocatalytic performance. The enriched photocatalytic performance of the BZFG NCs might be ascribed to a more efficient transfer and separation of photo-induced charges due to synergic effects at the Bi-ZnFe2O4/S-g-C3N4 interconnection. The proposed modification of ZnFe2O4 using Bi and S-g-C3N4 is effective, inexpensive, and environmentally safe.

Composite nanostructures of black TiO2/WO3 on rGO nanosheets for photoelectrochemical water splitting

A uniform dispersion of black TiO2 nanoparticles and WO3 nanorods on rGO nanosheets was assessed for its photoelectrochemical water splitting activity. A facile solution-based approach was employed to synthesize the black TiO2 nanoparticles and WO3 nanorods, whereas the modified Hummer's method was used to prepare the rGO nanosheets. The composite nanostructure was obtained using a solvothermal approach. Visible light absorption was improved significantly, and the bandgap was narrowed for nanocomposites (1.76 eV) than W-TiO2 nanoparticles (3.10 eV). The structural changes were validated using various analytical techniques like XRD, Raman, and XPS analysis. The morphology of the individual constitutions and composites was examined by TEM. Photoelectrochemical analysis showed that the composite nanostructures of black TiO2/WO3/rGO exhibited enhanced water splitting activity under visible light irradiation (0.83 mA cm−2 at 0 V). This enhancement was attributed mainly to the more efficient photoinduced charge (electron–hole) separation and transportation involved in the composite nanostructures.

Linking oxidative and reductive clusters to prepare crystalline porous catalysts for photocatalytic CO2 reduction with H2O

Mimicking natural photosynthesis to convert CO2 with H2O into value-added fuels achieving overall reaction is a promising way to reduce the atmospheric CO2 level. Casting the catalyst of two or more catalytic sites with rapid electron transfer and interaction may be an effective strategy for coupling photocatalytic CO2 reduction and H2O oxidation. Herein, based on the MOF ∪ COF collaboration, we have carefully designed and synthesized a crystalline hetero-metallic cluster catalyst denoted MCOF-Ti6Cu3 with spatial separation and functional cooperation between oxidative and reductive clusters. It utilizes dynamic covalent bonds between clusters to promote photo-induced charge separation and transfer efficiency, to drive both the photocatalytic oxidative and reductive reactions. MCOF-Ti6Cu3 exhibits fine activity in the conversion of CO2 with water into HCOOH (169.8 μmol g−1h−1). Remarkably, experiments and theoretical calculations reveal that photo-excited electrons are transferred from Ti to Cu, indicating that the Cu cluster is the catalytic reduction center.

One-dimensional rod-shaped Ag2Mo2O7/BiOI n-n junctions for efficient photodegradation of tetracycline and rhodamine B under visible light

One-dimensional rod-shaped Ag 2 Mo 2 O 7 /BiOI composite photocatalysts were prepared via a facile hydrothermal-calcining method. The structure, morphologies, and elemental nature of the photocatalysts were characterized. Ag 2 Mo 2 O 7 /BiOI was formed through the attachment of BiOI nanosheets on the surface of Ag 2 Mo 2 O 7 rods, resulting in a 1D/2D heterojunction with larger interface area, more surface-active sites, and faster charge transfer channel. The Ag 2 Mo 2 O 7 /BiOI heterogeneous exhibited excellent and stable photodegradation performances for Rhodamine B (RhB) and Tetracycline (TC) under visible light irradiation. At the optimum composition of 15 wt% BiOI, the Ag 2 Mo 2 O 7 /BiOI heterojunction exhibited a highest degradation rate for RhB and TC, which were 70 times and 16 times higher than those of Ag 2 Mo 2 O 7 , respectively. The improved photocatalytic performance can be attribute to the efficient separation of photoinduced charges caused by the formation of the n-n heterojunction between Ag 2 Mo 2 O 7 and BiOI. Additionally, the dominant active species of photocatalytic reaction were determined to be • O 2 − and h + by free radical capture experiments and ESR test. In addition, a toxicity test with E. coli was carried out, which shows that the photodegraded Tetracycline solution is basically harmless to E. coli. Based on the experimental results and hybrid density functional theory calculation, a plausible photocatalytic mechanism of n-n heterojunction was proposed. • One-dimensional rod-shaped Ag 2 Mo 2 O 7 /BiOI were synthesized by a solvothermal method. • Ag 2 Mo 2 O 7 /BiOI can efficiently degrade Tetracycline. • The toxicity of the degraded tetracycline solution was low by E. coli activity detection. • Charge carriers were separated due to the n-n heterojunction and large interface area.