Transient Photocurrent Response Research Articles

Photo-, Thermo-, Electrochromic, Erasable Inkless Printing, Ions Detection, and UV Detector Properties of Viologen Compounds Based on Homomolybdate/Keggin POMs.

Three POMs-based viologen compounds with different structures were successfully constructed under solvothermal and hydrothermal conditions, [Cu(1,4-cby)2(H2O)0.5(β-Mo8O26)0.5]·C3H7NO·3H2O (1), [H2(1,4-cby)2]·(β-Mo8O26) (2) (1,4-cby·Cl = 1-(4-carboxybenzyl)-4,4'-bipyridine chloride), [H2(1,4-cbyy)2]·(SiMo12O40) (3) (1,4-cbyy·Cl = 1-(4-cyanobenzyl)-4,4'-bipyridine chloride). Compound 1 is a structure with the number "eight-like" metal-organic chain with Cu as the nodes, and compounds 2 and 3 are fascinating structures connected by hydrogen bonding interactions. More importantly, compounds 1-3 exhibit a good response to both light and electricity and the thermal response of compound 1 was also studied. The reasons for the response of compounds 1-3 to external stimuli were analyzed through methods such as UV-Vis, EPR, and XPS. In addition, the transient photocurrent response results of compounds 1-3 are the same as those obtained from kinetic calculations. Meanwhile, the coated filter paper based on compound 3 has been successfully applied in erasable inkless printing and anti-counterfeiting, the test paper of 3 can also detect metal ions, and the films based on compounds 1-3 are a flexible and portable ultraviolet (UV) detector.

Construction novel highly active photocatalytic H2 evolution over noble-metal-free trifunctional Cu3P/CdS nanosphere decorated g-C3N4 nanosheet

Hydrogen energy possesses immense potential in developing a green renewable energy system. However, a significant problem still exists in improving the photocatalytic H2 production activity of metal-free graphitic carbon nitride (g-C3N4) based photocatalysts. Here is a novel Cu3P/CdS/g-C3N4 ternary nanocomposite for increasing photocatalytic H2 evolution activity. In this study, systematic characterizations have been carried out using techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), Raman spectra, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area analysis (BET), electrochemical impedance (EIS), and transient photocurrent response measurements. Surprisingly, the improved 3CP/Cd-6.25CN photocatalyst displays a high H2 evolution rate of 125721 μmol h−1 g−1. The value obtained exceeds pristine g-C3N4 and Cu3P/CdS by 339.8 and 7.6 times, respectively. This could be the maximum rate of hydrogen generation for a g–C3N4–based ternary nanocomposite ever seen when exposed to whole solar spectrum and visible light (λ > 420 nm). This research provides fresh perspectives on the rational manufacture of metal-free g-C3N4 based photocatalysts that will increase the conversion of solar energy. By reusing the used 3CP/Cd/g-C3N4 photocatalyst in five consecutive runs, the stability of the catalyst was investigated, and their individual activity in the H2 production activity was assessed. To comprehend the reaction mechanisms and emphasise the value of synergy between the three components, several comparison systems are built.

Fabricated S-scheme BiOBr/Cu2O heterojunction photocatalyst for adjusting conversion of CO2 to CH4

The preparation of heterojunction photocatalysts with staggered energy band structures and proper interfacial contacts is an effective way to improve CO2 conversion. This study adopted a simple hydrothermal method to form Cu2O on the surface of BiOBr, and s scheme BiOBr/Cu2O heterojunctions with close contacts were constructed. The rate of CO2 reduction over the catalyst was tested in a gas-solid reactor simulating sunlight. The results show that the BiOBr/Cu2O composite moderately yields CH4 with an efficiency of 22.78 μmol g−1h−1 for conversion from CO2 to CH4 in visible light, while pure BiOBr yields only CO. In addition, Transient photocurrent response, Electrochemical impedance spectroscopy, and Photoluminescence measurements demonstrated that the BiOBr/Cu2O had a strong photogenerated carrier transfer and separation and high photo-availability, while key intermediates favoring CH4 yield were found by in situ IR. Finally, the possible photocatalytic mechanism was explored based on the energy band structures of BiOBr and Cu2O in the characterization.

Effects of carbon-silicon structure on photochemical activity of biochars

Biochar has raised increasing concerns because of its great environmental impacts. It is known that the photocatalytic property of biochar is related to its carbon component and dissolved black carbon, but the effect of silicon component is ignored, and the effect of silicon and carbon phases was far less studied. This study systematically explored the photochemistry of silicon-rich and silicon-deficient biochar under light irradiation by using hexavalent chromium (Cr(VI)) and sulfadiazine as representative pollutants for photoreduction and photooxidation, respectively. It was found that biochar had photoreduction activity under the enhancement of electron donors, and 80.1% Cr(VI) can be removed by biochar with crystalline silicon and carbon (i.e., RH900) after 12 h irradiation. Meanwhile after low temperature pyrolysis, biochar with amorphous silicon and carbon (i.e., RH600) had great photooxidation capacity, and 71.90% organic pollutant was degraded within 24 h. The reaction was illustrated by transient photocurrent response, and hydroxyl radical generation measurement, and other tests. A new photochemical mechanism of the synergy between silicon and carbon model was proposed to elucidate the redox reactions of pollutants under the light. Graphitic carbon or crystalline silicon formed under high temperature played a role of valence band which was excited under light irradiation and the effect of electron donors to benefit photoreduction, while amorphous silicon formed under low temperature facilitated photooxidation process by increasing reactive oxygen species concentration. This study provided a gist for biochar production and application in the field of photocatalysis, and contributed to the broader understanding of biochar geochemical behavior in natural sunlit system.

Sol-gel extended hydrothermal synthesis of BiFeO3 nano-beads for excellent photocatalytic and photo-electrochemical properties under natural light irradiation

The synthesized BiFeO3haslow cost,distinctive structure,large specific surface area, and outstanding electrical and mechanical properties, making itstable, non-toxic, and cost-effective material that can be used in photocatalytic applications. Here, we report the successful synthesis of a pure-phase BiFeO3nano-beads through a well-controlled sol–gel extended hydrothermal strategy. The structural, morphological, and optical properties of as-prepared BiFeO3nano-beads were studied by X-ray Diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Brunauer-Emmett-Teller (BET) and Ultraviolet–visible–near-infrared (UV–vis–NIR) transmittance spectrophotometer. It was observed that BiFeO3nano-beads exhibit strong absorption in the UV and visible light region and the corresponding lowest band gap has been estimated to be 2.13 eV. The photo-electrochemical (PEC) properties of the prepared photo-anodes were analyzed with electrochemical impedance spectroscopy (EIS) and chronoamperometry analysis (CA). Electron transfer of the charge carriers and transient photo-current response were enhanced for BiFeO3nano-beads as studied by EIS and CA. The as-prepared BiFeO3nano-beads showed excellent photocatalytic and photo-electrochemical (PEC) properties for enhanced degradation of methylene blue (MB) and hydrogen evolution activity (14.7 mmol g−1h−1) in the presence of Platinum asco-catalyst were carried out under natural light irradiation at ambient temperature.

Enhanced photocatalyst with TiO2-anchored iron tailings structure for highly efficient degradation of doxycycline hydrochloride

The low utilization of sunlight and fast recombination of photogenerated electron-hole pairs (e−/h+) are the main reasons preventing the wide application of titanium dioxide (TiO2) in photocatalysis. A novel hybrid composite of TiO2/iron tailings (TITs) was synthesized in this study via a facile method as a photocatalyst for the degradation of doxycycline hydrochloride (DOX). The design beneficially enhances the light absorption capacity because the TITs composite photocatalyst has a narrower band gap (2.77 eV), larger light absorption edge (448 nm), and restrains recombination of photogenerated e−/h+, which is attributed to the TITs composite photocatalyst having a lower photoluminescence (PL) strength, a higher transient photo-current response, and a smaller Nyquist plot radius, as compared with pure TiO2. The DOX removal efficiency by TITs during photocatalytic degradation was 98.37% within 120 min under a Xe lamp and 76.73% within 180 min under sunlight, which were 1.23- and 1.46-fold higher than that of pure TiO2, respectively. The DOX removal rate increased by 3.8-fold after swine wastewater was diluted 20 times. This study provides an economical method for the clean recycling of iron tailings and identifies cheap raw materials for the preparation of photocatalytic materials, reducing the cost of photocatalytic materials applied to wastewater treatment, which is helpful for promoting the practical application of TiO2-based photocatalysts.

Synthesis of one-dimensional hierarchical Bi2O3 with enhanced photocatalytic reduction of Cr(VI) and degradation of organic compounds under simulated sunlight

A one-dimensional (1D) hierarchical Bi2O3 is obtained by calcining hierarchical Bi2O2CO3. Hierarchical Bi2O3 exhibits good photocatalytic activity. Results show that 50 mg/L of Cr(VI) solution, 50 mg/L of tetracycline and 40 mg/L of biphenol A can be photodegraded in 10, 10 and 20 min under simulated sunlight with an apparent rate constant value of 0.331, 0.179 and 0.214 min−1, respectively. This enhanced photocatalytic performance is mainly ascribed to special hierarchical structure and the more negative CB position. Radical capture and EPR measurements all prove the superoxide (O2−) radical is the major active species for photocatalytic reaction. The transient photocurrent responses, PL emission and electrochemical impedance indicate 1D hierarchical Bi2O3 displays an improved separation efficiency of photogenerated e-h pairs. These findings would inspire many research for developing high-performance catalysts using under simulated sunlight.

Enhanced photocatalytic hydrogen production from Co-MOF/CN by nitrogen and sulfur co-doped coal-based carbon quantum dots

A novel composite photocatalyst for photocatalytic decomposition of water for hydrogen evolution was successfully synthesized by in-situ growth of nitrogen and sulfur co-doped coal-based carbon quantum dots (NSCQDs) nanoparticles on the surface of sheet cobalt-based metal-organic framework (Co-MOF) and graphitic carbon nitride (g-C3N4, CN). The structure and properties of the obtained catalysts were systematically analyzed. NSCQDs effectively broaden the absorption of Co-MOF and CN in the visible region. The new composite photocatalyst has high hydrogen production activity and the hydrogen production rate reaches 6254 μmol/(g·h) at pH = 9. At the same time, NSCQDs synergy Co-MOF/CN composites have good stability. After four cycles of hydrogen production, the performance remains relatively stable. The transient photocurrent response and Nyquist plot experimental results further demonstrate the improvement of carrier separation efficiency in composite catalysts. The semiconductor type (n-type semiconductor) of the single-phase catalyst was determined by the Mott–Schottky test, and the band structure was analyzed. The conductive and valence bands of CN are −0.99 and 1.72 eV, respectively, and the conduction and valence bands of Co-MOF are −1.85 and 1.33 eV, respectively. The mechanism of the photocatalytic reaction can be inferred, that is, Z-type heterojunction is formed between CN and Co-MOF, and NSCQDs was used as cocatalyst.

Photocatalysis-PMS oxidation system based on CQDs-doped carbon nitride nanosheets for degradation of residual drugs in water.

Graphite-like carbon nitride (g-C3N4) is favored for its excellent physicochemical properties. However, the high complexation rate of photogenerated carriers greatly limits its practical applications. Based on this, a novel CQDs-doped carbon nitride nanosheets composite (CNS/CQDs) was prepared and applied to the visible light-induced activation of peroxymonosulfate (PMS) for meloxicam (Mel) and tetracycline (TC) degradation. The photocatalytic degradation of Mel and TC were remarkably promoted in the CNS/CQDs+PMS+vis system. Mel photodegradation of 99.90% was achieved over 30 min with 20 mg CNS/CQDs and 20 mg PMS at pH11. And TC photodegradation of 95.97% was achieved over 45 min with 20 mg CNS/CQDs and 20 mg PMS at nature pH6.5. The TOC mineralization rates of Mel and TC were 75.49% and 52.00%, respectively. The transient photocurrent response and electrochemical impedance measurements (EIS) results indicated that the doping of CQDs could improve the charge transfer efficiency of pure g-C3N4, and CNS/CQDs had a low charge transfer resistance. Capture experiments and EPR tests explored the effective actives in the CNS/CQDs+PMS+vis system. Possible degradation pathways of Mel were also analyzed. This study provides valid residual drugs degradation under the dual conditions of visible light catalytic oxidation and persulfate oxidation, which will be a novel perspective for advanced oxidation technology to effectively remove organic pollutants from water.

Effective graphene incorporation of strontium niobate–doped titanium oxide for photocatalytic hydrogen production

To meet the increasing global demand for clean energy and mitigate the impact of CO2 emissions on climate change, the production of photocatalytic hydrogen through water splitting is a compelling scientific and technological objective. Despite considerable efforts, the establishment of a reliable and highly efficient system for hydrogen generation powered by visible light remains challenging. In this study, we developed a solar-active strontium niobate-doped titanium oxide incorporated with graphene (Sr2Nb2O7–rGO–TiO2), characterized by various analytical techniques such as optical, morphological, HR-TEM, XPS, and XRD. Sr2Nb2O7–rGO–TiO2 demonstrated enhanced photocatalytic H2 evolution under solar irradiation without requiring precious-metal doping. The maximum H2 production performance rate of 1769 μmol/g/h was attained with the Sr2Nb2O7–rGO–TiO2 composites, significantly surpassing those of the bare (TiO2: 210 μmol/g/h, Sr2Nb2O7: 88 μmol/g/h) and binary (TiO2–rGO: 430 μmol/g/h, Sr2Nb2O7–rGO: 176 μmol/g/h, and Sr2Nb2O7–TiO2: 880 μmol/g/h) photocatalysts. The enhanced performance of the Sr2Nb2O7–rGO–TiO2 composite is attributable to the synergistic effect of rGO acting as an electron-transfer bridge. Thus, with the integration of rGO, absorption is attainable in an extended range up to 445 nm (2.90 eV), suggesting that the composite material could enable the catalyst to absorb more visible light. Additionally, the composite exhibited minor degradation after five consecutive cycles, demonstrating its excellent stability and reusability for hydrogen generation. Based on a comprehensive evaluation of the ESR and transient photocurrent response, a potential Z-scheme mechanism for the photocatalytic H2 generation activity over Sr2Nb2O7–rGO–TiO2 was suggested. The Z-scheme processability allows more electrons to contribute to the H2 evolution reduction. In this study, we developed a non-toxic, cost-effective, highly efficient, and recyclable photocatalyst for H2 production.

The Enhanced Photocatalytic Performance of Pr Doped Cu2O Under Visible Light

AbstractCuprous oxide (Cu2O) has a narrow band gap of 2.1–2.3 eV, which facilitates the absorption of visible light and the photocatalytic removal of pollutants from water. However, the catalytic efficiency of Cu2O has been affected by the rapidly compounding carriers in the photocatalytic process. In order to achieve adequate separation of the photogenerated carriers, a straightforward liquid‐phase reduction technique was used in this study to successfully obtain praseodymium‐doped cuprous oxide Pr : Cu2O (0, 1, 3, and 5 mol %). Praseodymium ions were successfully doped into the Cu2O lattice interstitial, as demonstrated by XRD and SEM studies, and the doped praseodymium ions decreased the crystallite size. The FT‐IR peak also confirmed the existence of Cu2O at 631 cm−1. With the increase of Pr doping to 3 %, the band gap gradually decreased to 2.12 eV. Experiments on the degradation of methyl orange (MO) under visible light irradiation showed that 3 % Pr : Cu2O photocatalyst showed the best photocatalytic performance. The Pr doping reduced the recombination of photogenerated electron‐hole pairs and enhanced the photocatalytic activity of Cu2O, according to the analysis results of PL, EIS and transient photocurrent response. Combining these results with active radical capture experiments, the functioning mechanism of the Pr : Cu2O photocatalyst was examined.

Perovskite CuO@BaSnO3 nanorods photocatalysts with promoted visible light ability for desulfurization of thiophene

BackgroundThe desulfurization of fuels is critical to upgrade their performance and to match the demands of sulfur standards MethodMesoporous p-n heterojunctions CuO/BaSnO3 nanorods were fabricated by the hydrothermal process in the presence of polyvinylpyrrolidone. The photocatalytic performance of the synthesized CuO/BaSnO3 nanorods at various CuO percentages compared with the pristine BaSnO3 was evaluated by desulfurising thiophene under visible light illumination Significant findingsXRD and HRTEM results verified the fabrication of perovskite BaSnO3 in cubic structure and CuO in the monoclinic phase, and TEM images of CuO/BaSnO3 exhibited nanorod-like morphology with a length of 100 nm and width of 10 nm decorated with CuO NPs (5 nm). After optimization, the experimental results showed that with a photocatalyst dosage of 2 g/L and CuO percentage of 15%, the maximal desulfurization rate of thiophene was around 100% within 60 min. The rate constant of 15% CuO/BaSnO3 photocatalyst was the maximum, and it was enhanced larger 3.36 times than that of the pristine BaSnO3 nanorods. The photocurrent intensity of 15% CuO/BaSnO3 photocatalyst was enhanced 9.2 times greater than that of pristine BaSnO3. The enhancement of the desulfurization rate illustrated that the creation of an internal electric field through the p-n heterojunction CuO/BaSnO3 system could facilitate the separation of photoinduced holes and electrons, improving the charge transport ability and hence promoting the photocatalytic performance. PL, transient photocurrent responses and electrochemical impedance results were determined to confirm our photocatalytic results. Cycling runs displayed that the obtained CuO/BaSnO3 photocatalyst still exhibited high photocatalytic ability and stability after five cycles. This work is anticipated to strengthen the design of effective and novel p-n heterojunctions photocatalysts for practical photocatalysis applications in terms of H2 production and detoxification of toxic organic compounds.

Novel visible-light-active P-g-CN-based α-Bi2O3/WO3 ternary photocatalysts with a dual Z-scheme heterostructure for the efficient decomposition of refractory ultraviolet filters and environmental hormones: Benzophenones

The ubiquitous and refractory benzophenone (BP)-type ultraviolet filters, which are also endocrine disruptors, were commonly detected in the aquatic matrix and could not be efficiently removed by conventional wastewater treatment processes, thus causing extensive concern. Herein, a novel ternary nanocomposite, P-g-CN/α-Bi2O3/WO3 (P-gBW), was successfully fabricated by mixing cocalcinated components and applied to the decomposition of BP-type ultraviolet filters. The dual-Z-scheme heterostructure of P-gBW enhances visible-light absorption, efficiently facilitates separation and mobility, and prolongs the lifetime of photoinduced charge carriers via double charge transfer mechanisms. The optimum 95 wt% P-gBW exhibited excellent photocatalytic activity, degrading 96% 4-hydroxy benzophenone (4HBP) within 150 min and 93% 2,2′,4,4′-tetrahydroxybenzophenone (BP-2) within 100 min under visible-light illumination, respectively. The pseudo-first-order rate constant of 4HBP (1.15 h−1) was 6.8-, 3.1-, 3.3- and 2.2-fold higher than those of WO3, P-g-CN, α-Bi2O3, and P-g-CN/α-Bi2O3, respectively, while that of BP-2 (1.71 h−1) was 5.2-, 2.2-, 3.2- and 1.5-fold higher, respectively. The improved photocatalytic degradation was attributed to efficient photoinduced charge carrier separation and migration and prevented the recombination of electron holes, as verified by photoluminescence, transient photocurrent response, and electrochemical impedance spectroscopy. Trapping experiments, electron paramagnetic resonance, and band energy position indicated an efficient dual-Z-scheme heterostructure.

CuS Nanoparticles Modified ZnO/CdS Dual Direct Z-type Heterostructure Nanocomposite for Efficient Visible-Light Photocatalytic Degradation RhB

The low-temperature hydrothermal and water bath methods are used to manufacture CuS@ZnO/CdS catalyst. The Rhodamine B degradation rate constant of CuS@ZnO/CdS is around 1.53 × 10−2 min−1, which is 3.9 times greater than that of ZnO. The coupling of CdS and loading of CuS onto ZnO surfaces were evaluated using XRD, SEM, TEM, and XPS. SEM demonstrated that 5 mg of CdS was the most effective in controlling the shape of ZnO nanoflakes. Ultraviolet-visible absorption (UV–vis) and Photoluminescence (PL) spectra reveal that CdS and CuS decreased the bandgap of ZnO and boosted its ability to absorb visible light. Transient photocurrent response (TPR) and electrochemical impedance spectra (EIS) display that CdS and CuS facilitate the quick separation of photoexcited carriers in ZnO. Notably, the optimal weight ratio of CuS was determined to be 15%, since excessive amounts of CuS would operate as recombination centers and cover active sites. Additionally, the dual Z-scheme carriers movement mechanism was proposed using sacrificed agent experiments, and TOC analyzed the mineralization rate of RhB after degradation. In this study, CuS@ZnO/CdS photocatalyst degraded RhB nearly 99% in 80 min, which is superior to the earlier photocatalysts. Therefore, this article holds great significance in the practical application of metal chalcogenide-modified ZnO-based photocatalysts with superior visible light-induced degradation performance in environmental purification.

Transient Photocurrent Response in a Perovskite Single Crystal‐Based Photodetector: A Case Study on the Role of Electrode Spacing and Bias

AbstractTransient photocurrent is a widely applied characterization technique to probe the charge‐carrier photogeneration and extraction dynamics in perovskite optoelectronic devices. Despite the large number of studies on the properties of perovskite single‐crystals (SCs) photodetectors (PDs), the underlying mechanism that governs the spectral line shape of transient photocurrent is not fully understood. Here, methylammonium lead bromide (MAPbBr3)SC based PDs are used to study the effect of different electrode spacing and bias on the transient photocurrent response under blue and green light irradiation. The observed differences in the spectral line shape of the transient photocurrent are explained using three‐step carrier transport model, which reveals the occurrence of carrier trapping and a recombination process in MAPbBr3 SC. The findings are further corroborated by intensity‐dependent photocurrent and impedance spectroscopy analysis of the resulting PDs. This work provides a basic insight into the origin of the different behavior of transient photocurrent response under variable electrode distance, bias, and irradiance light, which is expected to help to further understand and optimize the performance of perovskite based PDs.

Synergistic effect of adsorption and photocatalytic degradation of oilfield-produced water by electrospun photocatalytic fibers of Polystyrene/Nanorod-Graphitic carbon nitride

Graphitic carbon nitride with nanorod structure (Nr-GCN) was synthesized using melamine as a precursor without any other reagents by hydrothermal pretreatment method. XRD, FTIR, SEM, N2 adsorption-desorption from BET, UV–Vis DRS spectroscopy, and photoluminescence were used to characterize the prepared samples. Also, the photoelectrochemical behavior of nanoparticles was studied by photocurrent transient response and cyclic voltammetry analysis. Polystyrene (PS) fibrous mat was fabricated by electrospinning technique and used as a support for the stabilization of the nanoparticles. The performance of the synthesized nanoparticles and photocatalytic fibers (PS/Nr-GCN) was evaluated in oilfield-produced water treatment under visible light irradiation. During this process, oil contaminants were adsorbed by hydrophobic polystyrene fibers and simultaneously degraded by Nr-GCN. The removal efficiency of chemical oxygen demand (COD) has been obtained 96.6% and 98.4% by Nr-GCN and PS/Nr-GCN, respectively, at the optimum conditions of pH 4, photocatalyst dosage 0.5 g/L, COD initial concentration 550 mg/L, and illumination time 150 min. The gas chromatography-mass spectroscopy analysis results showed 99.3% removal of total petroleum hydrocarbons using photocatalytic fibers of PS/Nr-GCN. The results demonstrated that the GCN has outstanding features like controllable morphology, visible-light-driven, and showing high potential in oily wastewater remediation. Moreover, the synergistic effect of adsorption and photocatalytic degradation is an effective technique in oilfield-produced water treatment.

Visible light responding β-SiC/BiOBr S-scheme heterojunction photocatalyst with improved photodegradation efficiency of bisphenol A

A novel S-scheme β-SiC/BiOBr photocatalyst with visible-light-responding was synthesized by a two-step method. The heterostructure is well characterized and the composites exhibit improved photocatalytic activities and good stability of removing bisphenol An under visible light irradiation. The results of transient photocurrent response and photoluminescence tests indicate the improvement in separating photo-induced carriers for β-SiC/BiOBr photocatalyst. According to the active species test, optical band studies and density functional theory calculations, an S-scheme heterojunction prefer to be constructed between β-SiC and BiOBr, which could improve the photo-induced charges separation, reserve strong redox ability, and finally leading to an improved photocatalytic removal effect of bisphenol A.

Environment‐friendly g‐C3N4/SnO2/BiPO4 for enhanced Rhodamine B photocatalysis under visible‐light

AbstractObjectiveA highly active and stable composite photocatalyst which can be used in practical environmental remediation was developed.Methodsg‐C3N4/SnO2/BiPO4 ternary composites (CN/SO/BPO) were synthesised via simple impregnation, and their texture structure, morphology, and surface composition were deeply characterized.ResultsIn just 25 min under visible‐light radiation, CN/SO/BPO almost eliminated rhodamine B, and the observed rate constant for the reaction was almost 36 and 3 times higher in comparison to that of CN/BPO and SO/BPO, respectively.ConclusionsOn the basis of experimental outcomes and DFT calculation, the direct Z‐type structure of CN/SO/BPO lead to the improved photogenerated charge separation efficiency, as confirmed by surface photovoltage spectroscopy, electrochemical impedance spectroscopy, and transient photocurrent responses.

Potential of novel dual Z-scheme carbon quantum dots decorated MnIn2S4/CdS/Bi2S3 heterojunction for environmental applications.

In this work, CQDs decorated MnIn2S4/CdS/Bi2S3 heterojunction was prepared successfully by hydrothermal technique for photocatalytic disinfection of Escherichia coli (E. coli) and mineralization of methyl orange (MO) dye. The charge transferal route and mineralization process in CQDs-MnIn2S4/CdS/Bi2S3 heterojunction were comprehensively investigated by advanced spectroscopic techniques. The improved visible-light activity and enhanced photo-generated charge transferal efficacy caused dual Z-scheme CQDs-MnIn2S4/CdS/Bi2S3 heterojunction to achieve boosted photodegradation ability. The catalytic degradation trend was followed as CQDs-MnIn2S4/CdS/Bi2S3 > MnIn2S4 > CdS > Bi2S3. The dye was mineralized within 180min under visible light irradiation. The effect of reaction parameters, pH effect, catalyst dosage, and H2O2 addition on MO degradation was also investigated. The degradation rate was maximal at pH 4 with a pseudo-first-order rate constant, 0.0438min-1. The assessment of antibacterial properties revealed that CQDs-MnIn2S4/CdS/Bi2S3 composite effectively inactivated E. coli under visible light. Scavenging experiments, transient photocurrent response, and electron spin resonance spectroscopy suggested that •[Formula: see text] and holes were the dominant reactive species. The Z-scheme heterojunction is recyclable up to ten photocatalytic cycles according to recycling experiments. This research indicates the importance of dual Z-scheme CQDs decorated MnIn2S4/CdS/Bi2S3 heterojunction in wastewater remediation.

Efficient Photocatalytic Degradation of Tetracycline on the MnFe2O4/BGA Composite under Visible Light.

In this work, the MnFe2O4/BGA (boron-doped graphene aerogel) composite prepared via the solvothermal method is applied as a photocatalyst to the degradation of tetracycline in the presence of peroxymonosulfate. The composite's phase composition, morphology, valence state of elements, defect and pore structure were analyzed by XRD, SEM/TEM, XPS, Raman scattering and N2 adsorption-desorption isotherms, respectively. Under the radiation of visible light, the experimental parameters, including the ratio of BGA to MnFe2O4, the dosages of MnFe2O4/BGA and PMS, and the initial pH and tetracycline concentration were optimized in line with the degradation of tetracycline. Under the optimized conditions, the degradation rate of tetracycline reached 92.15% within 60 min, whereas the degradation rate constant on MnFe2O4/BGA remained 4.1 × 10-2 min-1, which was 1.93 and 1.56 times of those on BGA and MnFe2O4, respectively. The largely enhanced photocatalytic activity of the MnFe2O4/BGA composite over MnFe2O4 and BGA could be ascribed to the formation of type I heterojunction on the interfaces of BGA and MnFe2O4, which leads to the efficient transfer and separation of photogenerated charge carriers. Transient photocurrent response and electrochemical impedance spectroscopy tests offered solid support to this assumption. In line with the active species trapping experiments, SO4•- and O2•- radicals are confirmed to play crucial roles in the rapid and efficient degradation of tetracycline, and accordingly, a photodegradation mechanism for the degradation of tetracycline on MnFe2O4/BGA is proposed.