Innovative treatment of industrial effluents through combining ferric iron and attapulgite application.

The escalation of industrial activities has escalated the production of pharmaceutical and dyeing effluents, raising significant environmental issues. In this investigation, a hybrid approach of Fenton-like reactions and adsorption was used for deep treatment of these effluents, focusing on effects of variables like hydrogen peroxide concentration, catalyst type, pH, reaction duration, temperature, and adsorbent quantity on treatment effectiveness, and the efficacy of acid-modified attapulgite (AMATP) and ferric iron (Fe(III))-loaded AMATP (Fe(III)-AMATP) was examined. Optimal operational conditions were determined, and the possibility of reusing the catalysts was explored. Employing Fe3O4 as a heterogeneous catalyst and AMATP for adsorption, CODCr was reduced by 78.38-79.14%, total nitrogen by 71.53-77.43%, and phosphorus by 97.74-98.10% in pharmaceutical effluents. Similarly, for dyeing effluents, Fe(III)-AMATP achieved 79.87-80.94% CODCr, 68.59-70.93% total nitrogen, and 79.31-83.33% phosphorus reduction. Regeneration experiments revealed that Fe3O4 maintained 59.48% efficiency over three cycles, and Fe(III)-AMATP maintained 62.47% efficiency over four cycles. This work offers an economical, hybrid approach for effective pharmaceutical and dyeing effluent treatment, with broad application potential.

Novel combination of iron-carbon composite and Fenton oxidation processes for high-concentration antibiotic wastewater treatment.

The research presented herein explores the development of a novel iron-carbon composite, designed specifically for the improved treatment of high-concentration antibiotic wastewater. Employing a nitrogen-shielded thermal calcination approach, the investigation utilizes a blend of reductive iron powder, activated carbon, bentonite, copper powder, manganese dioxide, and ferric oxide to formulate an efficient iron-carbon composite. The oxygen exclusion process in iron-carbon particles results in distinctive electrochemical cells formation, markedly enhancing wastewater degradation efficiency. Iron-carbon micro-electrolysis not only boosts the biochemical degradability of concentrated antibiotic wastewater but also mitigates acute biological toxicity. In response to the increased Fe2+ levels found in micro-electrolysis wastewater, this research incorporates Fenton oxidation for advanced treatment of the micro-electrolysis byproducts. Through the synergistic application of iron-carbon micro-electrolysis and Fenton oxidation, this research accomplishes a significant decrease in the initial COD levels of high-concentration antibiotic wastewater, reducing them from 90,000 mg/L to about 30,000 mg/L, thus achieving an impressive removal efficiency of 66.9%. This integrated methodology effectively reduces the pollutant load, and the recycling of Fe2+ in the Fenton process additionally contributes to the reduction in both the volume and cost associated with solid waste treatment. This research underscores the considerable potential of the iron-carbon composite material in efficiently managing high-concentration antibiotic wastewater, thereby making a notable contribution to the field of environmental science.

Synthesis of Efficient S-Scheme Heterostructures Composed of BiPO4 and KNbO3 for Photocatalytic N2 Fixation and Water Purification.

The preparation of catalysts with heterojunction structures is a strategy to achieve efficient charge separation and high photocatalytic activity of photocatalysts. In this work, BiPO4/KNbO3 heterostructure photocatalysts were fabricated by a combination of hydrothermal and precipitation methods and subsequently employed in catalyzing N2-to-NH3 conversion and RhB degradation under light illumination. Morphological analysis revealed the effective dispersion of BiPO4 on KNbO3 nanocubes. Band structure analysis suggests that KNbO3 and BiPO4 exhibit suitable band potentials to form an S-scheme heterojunction. Under the joint action of the built-in electric field at the interface, energy band bending, and Coulomb attraction force, photogenerated electrons and holes with low redox performance are consumed, while those with high redox performance are effectively spatially separated. Consequently, the BiPO4/KNbO3 shows enhanced photocatalytic activity. The NH3 production rate of the optimal sample is 2.6 and 5.8 times higher than that of KNbO3 and BiPO4, respectively. The enhanced photoactivity of BiPO4/KNbO3 is also observed in the photocatalytic degradation of RhB. This study offers valuable insights for the design and preparation of S-scheme heterojunction photocatalysts.

In Situ Fabrication of an S-Scheme NaNbO3/Bi2O2CO3 Heterojunction for Enhanced Performance in Photocatalytic Nitrogen Fixation.

In this study, NaNbO3 microcubes were introduced during the preparation of Bi2O2CO3 nanosheets to construct a series of NaNbO3/Bi2O2CO3 heterojunctions with varying NaNbO3 content. Their photoactivities for N2 fixation were examined and compared. Results demonstrated that 7.5% NaNbO3/Bi2O2CO3 had the highest photoactivity. The NH3 production rate under simulated solar light is 453.1 µmol L-1 g-1 h-1, representing 2.0 and 3.8-fold increases compared to those of Bi2O2CO3 and NaNbO3, respectively. A comprehensive investigation encompassing the physical and chemical properties of the NaNbO3/Bi2O2CO3 photocatalyst was conducted. Bi2O2CO3 nanosheets were discovered to be distributed on the NaNbO3 microcubes surface. The addition of NaNbO3 exhibited nearly no effect on the photoabsorption performance and specific surface area of the Bi2O2CO3. However, the tight contact between NaNbO3 and Bi2O2CO3 and their appropriate band positions led to the formation of a heterojunction structure between them. The electron drift occurring in the interface region induces the creation of an internal electric field and energy band bending. This facilitates the transfer of photogenerated electrons and holes through an S-scheme mechanism, achieving efficient separation without compromising the redox performance. As a result, the NaNbO3/Bi2O2CO3 composite exhibits exceptional performance in the photocatalytic nitrogen fixation reaction. This study expands the application of S-scheme photocatalysts in the field of N2 reduction and provides insights into the preparation of efficient S-scheme photocatalysts.

Preparation of NaNbO3 microcube with abundant oxygen vacancies and its high photocatalytic N2 fixation activity in the help of Pt nanoparticles.

In this study, the photocatalytic N2 immobilization performance of NaNbO3 is enhanced via oxygen vacancy introduction and Pt loading. The designed Pt-loaded NaNbO3 with rich oxygen defects (Pt/O-NaNbO3) is synthesized by combining ion-exchange and photodeposition methods. Characterization result indicates that the O-NaNbO3 has hollow microcube morphology and higher surface area than NaNbO3. The introduced oxygen defects greatly affect the energy band structure. The band gap is slightly narrowed and the conduction band is raised, allowing O-NaNbO3 to generate electrons with strong reducibility. Moreover, the oxygen defects reduced the work function of NaNbO3, leading to increased charge separation in the bulk phase. The loaded Pt nanoparticles can further increase the surface charge separation via the formed Schottky barriers between Pt and O-NaNbO3, which was thought to be the primary cause of the increased photocatalytic activity. Additionally, the oxygen vacancies and metal Pt also contribute to the adsorption and activation of N2. Under the combined effect of the above changes, Pt/O-NaNbO3 presents much higher photoactivity than NaNbO3. The optimized NH3 production rate reaches 293.3 µmol/L g-1h-1 under simulated solar light, which is approximately 2.2 and 20.2 times higher than that of O-NaNbO3 and NaNbO3, respectively. This research offers a successful illustration of how to improve photocatalytic N2 fixation and may shed some light on how to design and construct efficient photocatalysts by combining several techniques.

Novel Bi2WO6/ZnSnO3 heterojunction for the ultrasonic-vibration-driven piezocatalytic degradation of RhB.

This study designed and prepared a new piezoelectric catalytic nanomaterial, Bi2WO6/ZnSnO3, and applied it in piezocatalytic water purification. Results indicated that the composite had superior piezocatalytic efficiency and stability in rhodamine B (RhB) degradation under ultrasonic vibration. The Bi2WO6/ZnSnO3 sample with 10% Bi2WO6 had the optimum activity with a degradation rate of 2.15 h-1, which was 7.4 and 11.3 times that of ZnSnO3 and Bi2WO6, respectively. Various characterizations were conducted to study the morphology, structure, and piezoelectric properties of the Bi2WO6/ZnSnO3 composites and reveal the reasons for their improved piezocatalytic performance. Results showed that ZnSnO3 cubes were dispersed throughout the surface of Bi2WO6 nanosheets, which enhanced the specific surface area and facilitated the piezocatalytic reaction. Additionally, type-II heterojunction structures formed at the contact interface of Bi2WO6 and ZnSnO3, driving the migration of piezoelectric-induced electrons and holes. Accordingly, the separation efficiency of charge carriers improved, and the piezoelectric catalytic activity was significantly enhanced. This study may provide a potential composite catalyst and a promising idea for the design of highly efficient piezoelectric catalyst.

Hydrogenolysis of glycerol over TiO2-supported Pt-WOx catalysts: Effects of the TiO2 crystal phase and WOx loading.

The selective hydrogenolysis of glycerol to 1,3-propanediol (1,3-PDO) with high added value is attraction but challenging. Pt-WOx-based catalysts have been extensively studied in the selective hydrogenolysis of glycerol. The catalyst support and the physicochemical state of WOx play important roles on this reaction. In this paper, Pt-WOx catalysts supported on TiO2 with different crystal forms were prepared and studied for their catalytic performance in hydrogenolysis of glycerol. It was observed that the catalytic performance of anatase-type (A-type) TiO2-supported catalyst (Pt/W/A-Ti) is much better than that of the rutile-type (R-type) TiO2 catalyst (Pt/W/R-Ti) due to its higher stability. Furthermore, the influence of W loading amount and state were thoroughly investigated for the Pt/W/A-Ti catalysts, and Pt/W/A-TiO2 with 5 wt% loading of WOx achieved the best catalytic performance (100% conversion of glycerol and 41% yield of 1,3-PDO under the optimal reaction conditions), owing to the suitable WOx domains and high dispersion of W species, as evidenced by XRD patterns and TEM images. Mechanism study by in-situ DRIFTS experiments indicated that glycerol was first converted to 3-hydroxypropanal and then converted to 1,3-PDO through subsequent reactions.

CuS/KTa0.75Nb0.25O3 nanocomposite utilizing solar and mechanical energy for catalytic N2 fixation.

This work synthesized a novel CuS/KTa0.75Nb0.25O3 (KTN) heterojunction composite and firstly applied it in photocatalytic and piezocatalytic reduction of N2 to NH3. XRD, Raman, XPS, SEM, and TEM analyses indicate that CuS nanoparticles closely adhered to the surface of KTN nanorods, which facilitates the migration of electrons between the two semiconductors. Mott-Schottky and valence band XPS analysis shows that KNbO3 shows a higher conduction band than CuS, indicating that CuS mainly acts as electron trappers to capture the photogenerated electrons from KTN. Because of the great enhanced spatial separation of photogenerated charge carriers, the CuS/KTN presents much higher performance than pure KNT, which is further confirmed by 1H NMR analysis of the reaction solution. An interesting finding is that synthesized CuS/KTN not only performs well under light irradiation but also can work in an ultrasonic bath, indicating its great potential in photo/piezocatalytic conversion of N2 to NH3. The optimal 10 %CuS/KTN shows an NH3 production rate of 36.2 µmol L-1 g-1 h-1 under ultrasonic vibration, which reaches 7.4 times that of KTN. The electrons generated by KTN through the piezoelectric effect can be captured by CuS, which endows the electrons a longer life to participate in the reaction, thereby improving the catalytic reaction performance.

Facile preparation of novel nickel sulfide modified KNbO3 heterojunction composite and its enhanced performance in photocatalytic nitrogen fixation.

This work was designed to prepare a novel NiS/KNbO3 p-n heterojunction composite for efficient photocatalytic nitrogen fixation under simulated sunlight. The NiS/KNbO3 photocatalyst was prepared through a two-step hydrothermal method. X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy analyses proved that NiS nanoparticles were closely decorated on the surface of KNbO3 nanorods, to facilitate the migration of electrons between the two semiconductors. Mott-Schottky analysis indicated that the Femi level of KNbO3 is higher than that of NiS. Thus, the electron migration from KNbO3 to NiS occurs naturally. This migration elevates the band potential of NiS, makes NiS/KNbO3 form a type-II photocatalyst, and generates an internal electric field in the composite. The synergetic effect of the internal electric field and the type-II band structure endows NiS/KNbO3 with high efficiency in the spatial separation of photogenerated electron-hole pairs, verified by electrochemical impedance spectroscopy and transient photocurrent experiments. Therefore, NiS/KNbO3 presents good efficiency in photocatalytic N2 reduction with an NH3 production rate of 155.6 µmol·L-1·g-1·h-1, which is 1.9 and 6.8 times higher than those of KNbO3 and NiS, respectively. UV-visible diffuse reflectance spectroscopy and N2-adsorption experiments were also performed to investigate the effect of light absorption and surface area on the photocatalytic reaction. Nevertheless, compared with the great promotion effect in charge separation, the contribution of the two factors can be ignored.

Membrane fouling caused by biological foams in a submerged membrane bioreactor: Mechanism insights.

Though sludge foaming often occurs and thus causes serious membrane fouling in membrane bioreactors (MBRs), the fouling mechanisms related with the foaming phenomenon have not been well addressed, hindering better understanding and solving foaming problem. In this work, it was interestingly found that, the foulants during the foaming period possessed extremely high specific filtration resistance (SFR) (over 1016 m kg-1) and strong adhesion ability to membrane surface. Chemical characterization showed that the proteins (178.57 mg/L) and polysaccharides (209.21 mg/L) in the foaming sample were about 6.4 times and 5.4 times of those in the supernatant sample, suggesting existence of a mechanism permitting continuous production of these foulants in the MBR during the foaming period. It was revealed that the fouling caused by foams was associated with gel layer filtration process, and the extremely high SFR can be interpreted by chemical potential change in the gel filtration process depicted in Flory-Huggins theory. Meanwhile, analyses by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory showed that the strong adhesion ability stemmed from the high interaction energy between the foaming foulants and membrane surface. In addition, 16S rDNA gene sequencing identified that the abundance of the foaming related bacteria species in the sludge suspension during the foaming period was more than 10 times of that during the non-foaming period. This study offered new mechanism insights into foaming fouling in MBRs.

Facile fabrication of novel Ag2S/K-g-C3N4 composite and its enhanced performance in photocatalytic H2 evolution.

This work synthesized a novel Ag2S/K-g-C3N4 photocatalyst which was effective in photocatalytic hydrogen production under simulated sunlight and visible light. Systematic investigation including TG, XRD, FT-IR, DRS, XPS, N2-adsorption, SEM, TEM, PL, and photoelectrochemical analyses was executed to examine the structure, optical property and charge separation efficiency of the as-prepared photocatalysts. Result indicated that potassium was successfully doped into the g-C3N4 framework via direct heating the mixture of melamine and potassium iodide at 520 °C, which increases the BET surface area, broadens the visible light response region, and elevates the separation efficiency of electron-hole pairs. The modification of Ag2S nanoparticles on the optimal K-g-C3N4 sample further improves the surface charge separation efficiency via a type-II mechanism, which was believed to be the key role in photocatalytic reaction. The best Ag2S/K-g-C3N4 hybrid shows a photocatalytic H2 generation rate of 868 and 96 µmol·g-1·h-1 under simulated sunlight and visible light, respectively. This value is 2.7 and 1.3 times greater than that of g-C3N4 and K-g-C3N4, respectively. Meanwhile, the Ag2S/K-g-C3N4 displayed high photocatalytic stability. A probable mechanism of the synthesized photocatalyst was also suggested.

Effectively H2 generation over CdS/KTa0.75Nb0.25O3 composite via water splitting.

The present work reports a novel CdS/KTa0.75Nb0.25O3 (KTN) composite photocatalyst which was synthesized via a facile deposition method. The photocatalytic reaction in Na2S solution indicated that the as-synthesized composite presented excellent performance in water splitting under simulated sunlight and visible light. A thorough investigation was performed to reveal the origin of the high performance. X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) experiments proved that CdS nanopartilces were uniformly dispersed on the surface of KTN naocubes. UV-visible diffuse reflection spectroscopy (DRS) analysis indicated that the addition of CdS improved the ability to absorb visible light. N2-adsorption analysis showed that the difference in surface area of the CdS/KTN composites was very small. Photoluminescence (PL) spectroscopy, electrochemical impedance spectroscopy (EIS), and transient photocurrent response (PC) analyses suggested that the added CdS greatly elevated the charge separation efficiency, which was considered as the key character of the composite. On the basis of the characterization results and the band structure of the two semiconductors, it is deduced that the CdS/KTN composite works according to a type-II mechanism under simulated sunlight. The optimal sample demonstrated a H2-generation rate of 1252 µmol·g-1·h-1, which is 260 and 48 times higher than that of KTN and CdS, respectively. Under visible light, photosensitization mechanism works in the composite. The synergetic effect of CdS and KTN in H2 production was also observed. Meanwhile, the composite also presented high photocatalytic stability. Considering the high activity and stability, the CdS/KTN may have potential application in photocatalytic H2 generation.

In-situ synthesis of AgNbO3/g-C3N4 photocatalyst via microwave heating method for efficiently photocatalytic H2 generation.

This paper is designed for elevating the photocatalytic H2-evoultion performance of g-C3N4 through the modification of AgNbO3 nanocubes. Via the microwave heating method, g-C3N4 was in-situ formed on AgNbO3 surface to fabricate a close contact between the two semiconductors in forty minutes. X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) experiments were performed to confirm the binary structure of the synthesized AgNbO3/g-C3N4 composite. N2-adsorption and visible diffuse reflection spectroscopy (DRS) analyses indicated that the addition of AgNbO3 to g-C3N4 showed nearly negligible influence on the specific surface area and the optical property. Photoluminescence (PL) spectroscopy experiment suggested that the AgNbO3/g-C3N4 displayed reduced PL emission and longer lifetime of photoexcited charge carriers than g-C3N4, which could be ascribed to the suitable band potential and the intimate contact of g-C3N4 and AgNbO3. This result was also confirmed by the transient photocurrent response experiment. The influence of the enhanced charge separation was displayed in their photocatalytic reaction. AgNbO3/g-C3N4 sample showed enhanced performance in photocatalytic H2-generation under visible light illumination. The H2-evolution rate is determined to be 88 µmol·g-1·h-1, which reaches 2.0 times of g-C3N4. This study provides a feasible and rapid approach to fabricate g-C3N4 based composite.

Lattice Engineering on Metal Cocatalysts for Enhanced Photocatalytic Reduction of CO2 into CH4.

Photocatalytic conversion of CO2 into CH4 represents an appealing approach to alleviate the world's continued reliance on fossil fuels and global warming resulting from increasing CO2 concentrations in the atmosphere. However, its practical application is greatly limited by serious electron-hole recombination in the photocatalysts and the production of CO and H2 as side reactions. Herein, for the first time, it is demonstrated that the photocatalytic reduction of CO2 to CH4 can be significantly improved through the simultaneous alloying and hydriding of metal cocatalysts. The isolation of Cu and H atoms in Pd lattices play three roles in the enhancement of CO2 to CH4 conversion: 1) Cu atoms provide catalytic sites to reduce CO2 into CO and then to CH4 to suppress H2 evolution; 2) H atoms improve the electron-trapping ability of cocatalysts; and 3) H atoms accelerate the reduction of CO to CH4 , which is the rate-limiting procedure in the conversion of CO2 into CH4 . Arising from the synergistic interplay between Pd-H and Cu-CO sites, C3 N4 -Pd9 Cu1 Hx (15 mg) achieves 100 % selectivity for CH4 production with an average rate of 0.018 µmol h-1 under visible-light irradiation. This work provides insights into the design of a cocatalyst for highly selective CO2 conversion through lattice engineering at atomic precision.

Application of Ag/AgBr/GdVO4 composite photocatalyst in wastewater treatment.

Ag/AgBr/GdVO4 composite photocatalysts were designed and synthesized in this paper. The physical and chemical structures, as well as optical properties of the synthesized composite were investigated via XRD, XPS, TEM, and UV-vis. It is found that the composite showed a ternary heterojunction structure of Ag, AgBr and GdVO4. Meanwhile, it has a high intensity of light current, indicating its high separation efficiency of electron and hole. Photocatalytic oxidation of rhodamine B (RhB) under visible light irradiation was performed to investigate the activity of the Ag/AgBr/GdVO4 composite. Result indicates that it shows excellent photocatalytic activity. Under visible light irradiation for 12min, about 80% of RhB (30µmol/L) was degraded. The degradation rate is estimated to be 0.253 min-1, which is three times higher than that of pure AgBr. The high photoactivity can be ascribed to the synergetic effect of AgBr, GdVO4, and Ag nanoparticle in separation of electron-hole pairs.

A Hierarchical Bipyridine-Constructed Framework for Highly Efficient Carbon Dioxide Capture and Catalytic Conversion.

As a C1 feedstock, CO2 has the potential to be uniquely highly economical in both a chemical and a financial sense. Porous materials bearing particular binding and active sites that can capture and convert CO2 simultaneously are promising candidates for CO2 utilization. In this work, a bipyridine-constructed polymer featuring a high surface area, a hierarchical porous structure, and excellent stability was synthesized through free-radical polymerization. After metalation, the resultant catalysts exhibited superior activities in comparison with those of their homogeneous counterparts in the cycloaddition of CO2 to epoxides. The high performance of the heterogeneous catalysts originates from cooperative effects between the CO2 -philic polymer and the embedded metal species. In addition, the catalysts showed excellent stabilities and are readily recyclable; thus, they are promising for practical utilization for the conversion of CO2 into value-added chemicals.

Novel indicators for thermodynamic prediction of interfacial interactions related with adhesive fouling in a membrane bioreactor.

This study focused on developing indicators to predict adhesive membrane fouling in a membrane bioreactor (MBR). Thermodynamic interactions between membrane surface and foulants in various interaction scenes were comprehensively evaluated. It was revealed that, the total interaction energy in contact could be considered as a critical value affecting adhesion of foulants. Surface hydrophilicity cannot be simply represented by water contact angle. Statistical analysis showed that membrane acid-based (AB) surface tension, Lifshitz-Van der waals (LW) surface tension, total tension, zeta potential and water contact angle had no apparent correlation with adhesive fouling, suggesting the infeasibility of these parameters as fouling predictors. It was found that, interaction between two identical membrane surface in water (ΔGsws) and membrane surface electron donor tension (γ-) strongly correlated with adhesive fouling, and could be reliable indicators to predict adhesive fouling. This study identified the relationships of series membrane surface properties with adhesive fouling in MBRs.

Facet engineered interface design of NaYF4:Yb,Tm upconversion nanocrystals on BiOCl nanoplates for enhanced near-infrared photocatalysis.

The combination of upconversion nanocrystals with a wide-bandgap semiconductor is an efficient strategy to develop near-infrared (NIR)-responsive photocatalysts. The photocatalytic activity of the hybrid structures is greatly determined by the efficiency of the energy transfer on the interface between upconversion nanocrystals and the semiconductor. In this work, we demonstrate the interface design of a NaYF4:Yb,Tm-BiOCl hybrid structure based on the choice of suitable BiOCl facets in depositing NaYF4:Yb,Tm upconversion nanocrystals. It was found that the selective deposition of NaYF4:Yb,Tm nanocrystals on the BiOCl(110) facet can greatly enhance the photocatalytic performance in dye degradation compared with the sample with NaYF4:Yb,Tm nanocrystals loaded on the BiOCl(001) facet. Two effects were believed to contribute to this enhancement: (1) a stronger UV emission absorption ability of the BiOCl(110) facet from NaYF4:Yb,Tm in generating more photo-induced charge carriers resulted from the narrower bandgap; (2) a shorter diffusion distance of photogenerated charge carriers to the BiOCl(110) reactive facet for surface catalytic reactions owing to the spatial charge separation between different facets. This work highlights the rational interfacial design of an upconversion nanocrystal-semiconductor hybrid structure for enhanced energy transfer in photocatalysis.

Modeling three-dimensional surface morphology of biocake layer in a membrane bioreactor based on fractal geometry.

While the adsorptive fouling in membrane bioreactors (MBRs) is highly dependent of the surface morphology, little progress has been made on modeling biocake layer surface morphology. In this study, a novel method, which combined static light scattering method for fractal dimension (Df) measurement with fractal method represented by the modified two-variable Weierstrass-Mandelbrot function, was proposed to model biocake layer surface in a MBR. Characterization by atomic force microscopy showed that the biocake surface was stochastic, disorder, self-similarity, and with non-integer dimension, illustrating obvious fractal features. Fractal dimension (Df) of sludge suspension experienced a significant change with operation of the MBR. The constructed biocake layer surface by the proposed method was quite close to the real surface, showing the feasibility of the proposed method. It was found that Df was the critical factor affecting surface morphology, while other factors exerted moderate or minor effects on the roughness of biocake layer.

Embedding Metal in the Interface of a p-n Heterojunction with a Stack Design for Superior Z-Scheme Photocatalytic Hydrogen Evolution.

The construction of a p-n heterojunction is an efficient strategy to resolve the limited light absorption and serious charge-carrier recombination in semiconductors and enhance the photocatalytic activity. However, the promotion effect is greatly limited by poor interfacial charge transfer efficiency as well as reduced redox ability of charge carriers. In this work, we demonstrate that the embedding of metal Pd into the interface between n-type C3N4 and p-type Cu2O can further enhance the interfacial charge transfer and increase the redox ability of charge carriers through the design of the C3N4-Pd-Cu2O stack nanostructure. The embedded Pd nanocubes in the stack structure not only trap the charge carriers from the semiconductors in promoting the electron-hole separation but also act as a Z-scheme "bridge" in keeping the strong reduction/oxidation ability of the electrons/holes for surface reactions. Furthermore, Pd nanocubes also increase the bonding strength between the two semiconductors. Enabled by this unique design, the hydrogen evolution achieved is dramatically higher than that of its counterpart C3N4-Cu2O structure without Pd embedding. The apparent quantum efficiency (AQE) is 0.9% at 420 nm for the designed C3N4-Pd-Cu2O. This work highlights the rational interfacial design of heterojunctions for enhanced photocatalytic performance.