Preparation of Au-BiVO4 heterogeneous nanostructures as highly efficient visible-light photocatalysts

Construction of Ultrathin BiVO4-Au-Cu2O Nanosheets with Multiple Charge Transfer Paths for Effective Visible-Light-Driven Photocatalytic Degradation of Tetracycline

In this study, unique BiVO4-Au-Cu2O nanosheets (NSs) are well designed and multiple charge transfer paths are consequently constructed. The X-ray photoelectron spectroscopy measurement during a light off-on-off cycle and redox capability tests of the photo-generated charge carriers confirmed the formation of Z-scheme heterojunction, which can facilitate the charge carrier separation and transfer and maintain the original strong redox potentials of the respective component in the heterojunction. The ultrathin 2D structure of the BiVO4 NSs provided sufficient surface area for the photocatalytic reaction. The local surface plasmon resonance (LSPR) effect of the electron mediator, Au NPs, enhanced the light absorption and promoted the excitation of hot electrons. The multiple charge transfer paths effectively promoted the separation and transfer of the charge carrier. The synergism of the abovementioned properties endowed the BiVO4-Au-Cu2O NSs with satisfactory photocatalytic activity in the degradation of tetracycline (Tc) with a removal rate of ≈80% within 30 min under visible light irradiation. The degradation products during the photocatalysis are confirmed by using ultra-high performance liquid chromatography-mass spectrometry and the plausible degradation pathways of Tc are consequently proposed. This work paves a strategy for developing highly efficient visible-light-driven photocatalysts with multiple charge transfer paths for removing organic contaminants in water.

Photocatalytic Activity of Ag Nanoparticles Deposited on Thermoexfoliated g-C3N4

The limited access to fresh water and the increased presence of emergent pollutants (EPs) in wastewater has increased the interest in developing strategies for wastewater remediation, including photocatalysis. Graphitic carbon nitride (g-C3N4) is a 2D non-metal material with outstanding properties, such as a 2.7 eV bandgap and physicochemical stability, making it a promising photocatalyst. This work reports the process of obtaining high-surface-area (SA) g-C3N4 using the thermal-exfoliation process and the posterior effect of Ag-nanoparticle loading over the exfoliated g-C3N4 surface. The photocatalytic activity of samples was evaluated through methylene blue (MB) degradation under visible-light radiation and correlated to its physical properties obtained by XRD, TEM, BET, and UV-Vis analyses. Moreover, 74% MB degradation was achieved by exfoliated g-C3N4 compared to its bulk counterpart (55%) in 180 min. Moreover, better photocatalytic performances (94% MB remotion) were registered at low Ag loading, with 5 wt.% as the optimal value. Such an improvement is attributed to the synergetic effect produced by a higher SA and the role of Ag nanoparticles in preventing charge-recombination processes. Based on the results, this work provides a simple and efficient methodology to obtain Ag/g-C3N4 photocatalysts with enhanced photocatalytic performance that is adequate for water remediation under sunlight conditions.

The visible-light-driven photocatalytic reduction of Cr6+ using BiVO4: assessing the effect of Au deposition and the reaction parameters

In this work, fern-leaf-like BiVO4 was used to photocatalytically reduce Cr6+ in water. Nanosized BiVO4 displayed bandgap energy and specific surface area of 2.49 eV and 5.65 m2 g-1, respectively. Metallic Au nanoparticles were deposited on the BiVO4 to increase the photocatalytic performance. To optimize the reaction conditions, the sacrificial agents methanol, ethanol, formic acid, dimethyl sulfoxide, and KI were tested, while different catalyst dosages and Au loadings were assessed. The best sacrificial agent was formic acid, which was used at an optimal concentration of 0.01 mol L-1. The complete removal of Cr6+ was attained after 90 min of visible light irradiation using a catalyst dosage of 1.5 g L-1. Depositing metallic Au nanoparticles barely improved the photocatalytic performance, thus unmodified BiVO4 was used to remove Cr6+ in tap water. The matrix effect slowed the photocatalytic process, and the complete removal of Cr6+ was achieved in 120 min. Cr3+ and Cr6+ species were precipitated on the catalyst surface at the end of the photocatalytic process; still, BiVO4 displayed high stability after three reaction cycles.

Synergistic Spatial Confining Effect and O Vacancy in WO3 Hollow Sphere for Enhanced N2 Reduction

Visible-light-driven N2 reduction into NH3 in pure H2O provides an energy-saving alternative to the Haber-Bosch process for ammonia synthesizing. However, the thermodynamic stability of N≡N and low water solubility of N2 remain the key bottlenecks. Here, we propose a solution by developing a WO3-x hollow sphere with oxygen vacancies. Experimental analysis reveals that the hollow sphere structure greatly promotes the enrichment of N2 molecules in the inner cavity and facilitates the chemisorption of N2 onto WO3-x-HS. The outer layer's thin shell facilitates the photogenerated charge transfer and the full exposure of O vacancies as active sites. O vacancies exposed on the surface accelerate the activation of N≡N triple bonds. As such, the optimized catalyst shows a NH3 generation rate of 140.08 μmol g-1 h-1, which is 7.94 times higher than the counterpart WO3-bulk.

Sonochemically assisted the synthesis and catalytic application of bismuth-based photocatalyst: A mini review

Recently, bismuth (Bi)-based photocatalysts have been a well-deserved hotspot in the field of photocatalysis owning to their photoelectrochemical properties driven by the distortion of the Bi 6 s orbital, while their narrow band gap and poor quantum efficiency still restrict their application. With the development of ultrasonic technology, it is expected to become a broom to clear the application obstacles of Bi-based photocatalysts. The special forces and environmental conditions brought by ultrasonic irradiation play beneficial roles in the preparation, modification and performance releasement of Bi-based photocatalysts. In this review, the role and influencing factors of ultrasound in the preparation and modification of Bi-based photocatalysts were introduced. Crucially, the mechanism of the improving the performance for various types of Bi-based photocatalysts by ultrasound in the whole process of photocatalysis was deeply analyzed. Then, the application of ultrasonic synergistic Bi-based photocatalysts in contaminants treatment and energy conversion was briefly introduced. Finally, based on an unambiguous understanding of ultrasonic technology in assisting Bi-based photocatalysts, the future directions and possibilities for ultrasonic synergistic Bi-based photocatalysts are explored.

Multidimensional applications and potential health implications of nanocomposites

This study reviews the concept, classifications, and techniques involved in the synthesis of nanocomposites. The environmental and health implications of nanoparticles and composite materials were detailed, as well as the applications of nanocomposites in water remediation, antibacterial application, and printed circuit boards. The study gave insights into the challenges of water pollution treatment and provided a broad list of nanocomposites that have been explored for water remediation. Moreover, the emergence of multi-drug resistance to many antibiotics has made current antibiotics inadequate in the treatment of disease. This has engineered the development of alternative strategies in the drug industries for the production of effective therapeutic agents, comprising nanocomposites with antibacterial agents. The new therapeutic agents known as nanoantibiotics are more efficient and have paved the way to handle the challenges of antibiotic resistance. In printed circuit boards, nanocomposites have shown promising applications because of their distinct mechanical, thermal, and electrical characteristics. The uniqueness of the write-up is that it provides a broad explanation of the concept, synthesis, application, toxicity, and harmful effects of nanocomposites. Thus, it will provide all-inclusive awareness to readers to identify research gaps and motivate researchers to synthesize novel nanocomposites for use in various fields.

Nanoprecipitated CoPi enhanced photoelectrochemical water oxidation toward sensitive and selective Co2+ detection

The detection of heavy metal ions Co²⁺ is of great significance to the environment and human health. Herein, a simple, highly selective and sensitive photoelectrochemical detection strategy for Co²⁺ was developed based on the enhanced activity by nanoprecipitated CoPi on the Au nanoparticle decorated BiVO₄ electrode. The new photoelectrochemical sensor has a low detection limit of 0.03 μΜ and wide detection range of 0.1-10, and 10-6000 μΜ, with a high selectivity over other metal ions. The Co²⁺ concentration in tap water and commercial drinking water has also been successfully determined with the proposed method. Scanning electrochemical microscopy technique was employed to characterize the photocatalytic performance and heterogenous electron transfer rate of electrodes in situ, further revealing the photoelectrochemical sensing mechanism. Besides determining Co²⁺ concentration, this approach of enhanced catalytic activity by nanoprecipitation can be further extended to develop a variety of electrochemical, photoelectrochemical and optical sensing platforms for many other hazardous ions and biological molecules.

Synergism of Co/Na in BiVO4 microstructures for visible-light driven degradation of toxic dyes in water

In this work, we report a synergism of Co/Na in Co@Na-BiVO₄ microstructures to boost the photocatalytic performance of bismuth vanadate (BiVO₄) catalysts. A co-precipitation method has been employed to synthesize blossom-like BiVO₄ microstructures with incorporation of Co and Na metals, followed by calcination at 350 °C. The structure and morphology of the as-prepared photocatalysts are characterized by XRD, Raman, FTIR, SEM, EDX, AFM, UV-vis/DRS and PL techniques. Dye degradation activities are evaluated by UV-vis spectroscopy, in which methylene blue, Congo red and rhodamine B dyes are chosen for comparative study. The activities of bare BiVO₄, Co-BiVO₄, Na-BiVO₄, and Co@Na-BiVO₄ are compared. To evaluate the ideal conditions, various factors that affect degradation efficiencies have been investigated. The results of this study show that the Co@Na-BiVO₄ photocatalysts exhibit higher activity than bare BiVO₄, Co-BiVO₄ or Na-BiVO₄. The higher efficiencies were attributed to the synergistic role of Co and Na contents. This synergism assists in better charge separation and more electron transportation to the active sites during the photoreaction.

A review of research trends on the usage of photocatalysis for wastewater treatment: bibliometric analysis

Photocatalysis is seen as a viable alternative to treating water pollution, due to its flexibility, low cost, and ability to use visible light which is a plentiful and free energy source. Hence, determining the topics of interest and widening collaboration networks will go a long way in improving research in this field. In this study, we aimed to analyze the global research trends on the usage of photocatalysis for wastewater treatment using bibliometric analysis, centered on the outputs of publications, co-authorships, countries of affiliation, and author's keyword co-occurrences. Bibliometric analysis is a review method that is well-known and more conversant to Social Science. Employing it in Physical Science, which is rarely seen, will provide an avenue and yet another method of determining common research topics as well as the potential opportunities and future research in the field. A potential hybrid review paper of great importance to future research in the area will be produced. A total of 1373 articles published within 27 years between 1993 and 2020 were extracted from the Scopus database. In the beginning, less attention was given to the said topic, because after the oldest article was published in 1993, there was no record of other publications until after 5 years (1998). However, from 2002 there was a growing interest in research in that field, with a cumulative increase every year to date, except for a few years with fewer publications. Meanwhile, the number of publications has risen significantly from 2017 to 2020, with an increase of more than 70 publications every year; this is expected to increase rapidly in the coming years. Recently researchers are focusing on developing efficient photocatalysts for contaminants of emerging concern, like pharmaceutical and refinery wastewater, however, the usage of conducting polymers to produce nanocomposite which was found to be very effective is still lagged in wastewater treatment, as such it will be a good area of future research on effective photocatalysts for wastewater treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40899-023-00868-5.

BiVO4 As a Sustainable and Emerging Photocatalyst: Synthesis Methodologies, Engineering Properties, and Its Volatile Organic Compounds Degradation Efficiency

Bismuth vanadate (BiVO₄) is one of the best bismuth-based semiconducting materials because of its narrow band gap energy, good visible light absorption, unique physical and chemical characteristics, and non-toxic nature. In addition, BiVO₄ with different morphologies has been synthesized and exhibited excellent visible light photocatalytic efficiency in the degradation of various organic pollutants, including volatile organic compounds (VOCs). Nevertheless, the commercial scale utilization of BiVO₄ is significantly limited because of the poor separation (faster recombination rate) and transport ability of photogenerated electron-hole pairs. So, engineering/modifications of BiVO₄ materials are performed to enhance their structural, electronic, and morphological properties. Thus, this review article aims to provide a critical overview of advanced oxidation processes (AOPs), various semiconducting nanomaterials, BiVO₄ synthesis methodologies, engineering of BiVO₄ properties through making binary and ternary nanocomposites, and coupling with metals/non-metals and metal nanoparticles and the development of Z-scheme type nanocomposites, etc., and their visible light photocatalytic efficiency in VOCs degradation. In addition, future challenges and the way forward for improving the commercial-scale application of BiVO₄-based semiconducting nanomaterials are also discussed. Thus, we hope that this review is a valuable resource for designing BiVO₄-based nanocomposites with superior visible-light-driven photocatalytic efficiency in VOCs degradation.

Growth of villi-microstructured bismuth vanadate (Vm-BiVO4) for photocatalytic degradation of crystal violet dye

In this work, villi-microstructured Au-loaded BiVO₄ photocatalysts were successfully synthesized by hydrothermal method. The as-synthesized photocatalysts were characterized by XRD, Raman, UV-Vis-DRS, PL, SEM and EDX techniques. The presence of metallic Au on the surface of Vm-BiVO₄ support boosts the photocatalytic performance to degrade toxic crystal violet dye. The enhanced activities were attributed to the surface plasmon resonance (SPR) of Au which efficiently broadens the visible light response. SPR increases the electron population in Vm-BiVO₄ and forms a Schottky barrier at the interface between Au and Vm-BiVO₄ which enhances the separation efficiency of photoinduced charges. Various factors affecting photocatalytic degradation of crystal violet (CV) were studied to find optimum conditions. In addition, a radical trapping study indicates that ˙O₂ ^- is the main active species in the degradation process of cationic CV dye. All photocatalytic degradation reactions were monitored by UV-Vis spectrophotometry (PerkinElmer/λ-365).

Ultrabroad spectral response and excellent SERS performance of PbS-assisted Au/PbS/Au nanostars

Noble metal nanomaterials have many excellent optical properties due to localized surface plasmon resonance induced by external electric and magnetic fields. The plasmon-enhanced optical properties of nanomaterials can be controlled by changing their shapes or compositions. Here, we use a gentle approach to synthesize Au/PbS/Au nanostars with multiple tips and explore the surface-enhanced Raman scattering (SERS) activity, the second harmonic generation (SHG), and photocatalytic performance. The Au/PbS/Au nanostars have ultrabroad spectral responses and significantly enhanced local electric fields near the sharp tips. The size and tip length of the Au/PbS/Au nanostars can be adjusted by changing the amount of HAuCl₄. The Au/PbS/Au nanostars exhibit largely enhanced SERS activity and photocatalytic degradation efficiency compared with the Au bipyramids and the Au BPs@PbS nanocrystals. In addition, the SHG of Au/PbS/Au nanostars is also significantly enhanced due to asymmetry and local field enhancement. This research shows potential in many applications ranging from photophysics to photochemistry.

Synthesis of Ce0.1La0.9MnO3 Perovskite for Degradation of Endocrine-Disrupting Chemicals under Visible Photons

The UN Environmental Protection Agency has recognized 4-n-Nonylphenol (NP) and bisphenol A (BPA) as among the most hazardous chemicals, and it is essential to minimize their concentrations in the wastewater stream. These industrial chemicals have been witnessed to cause endocrine disruption. This report describes the straightforward hydrothermal approach adopted to produce Ce0.1La0.9MnO3 (CLMO) perovskite’s structure. Several physiochemical characterization approaches were performed to understand the Ce0.1La0.9MnO3 (CLMO) perovskite crystalline phase, element composition, optical properties, microscopic topography, and molecular oxidation state. Here, applying visible photon irradiation, the photocatalytic capability of these CLMO nanostructures was evaluated for the elimination of NP and BPA contaminants. To optimize the reaction kinetics, the photodegradation of NP and BPA pollutants on CLMO, perovskite was studied as a specification of pH, catalyst dosage, and initial pollutant concentration. Correspondingly, 92% and 94% of NP and BPA pollutants are degraded over CLMO surfaces within 120 and 240 min, respectively. Since NP and BPA pollutants have apparent rate constants of 0.0226 min−1 and 0.0278 min−1, respectively, they can be satisfactorily fitted by pseudo-first-order kinetics. The decomposition of NP and BPA contaminants is further evidenced by performing FT-IR analysis. Owing to its outstanding photocatalytic execution and simplistic separation, these outcomes suggest that CLMO is an intriguing catalyst for the efficacious removal of NP and BPA toxicants from the aqueous phase. This is pertinent for the treatment of endocrine-disrupting substances in bioremediation.

Combined Schottky junction and doping effect in CdxZn1-xS@Au/BiVO4 Z-Scheme photocatalyst with boosted carriers charge separation for CO2 reduction by H2O

A Z-scheme photosystems combining Schottky junction and loading of applicable bandgap semiconductor is beneficial for enhancing the charge carriers' separation/transfer as well as maintain their excellent redox ability. Here, Cd_xZn_1-xS@Au was in-situ deposited on the (010) facets of BiVO₄ taking Au as a bridge for constructing a sandwich structure Cd_xZn_1-xS@Au/BiVO₄ Z-scheme photocatalyst. The electrons in BiVO₄ (010) migrate unidirectionally to Au nanoparticles across the Schottky junction and effectively suppress opposite electrons flow, then be captured by the excited holes in Cd_xZn_1-xS. Furthermore, Zn-doping also contributes to an appropriate redox ability and charge carriers separation. Benefiting from the dual-facilitated effects, the ternary Cd_xZn_1-xS@Au/BiVO₄ exhibited superior photocatalytic activity for CO₂ reduction under visible light irradiation using H₂O as a reducing agent, as compared with CdS and CdS@Au/BiVO₄. Furthermore, the intermediate product HCOO* fixed on the surface of Cd_xZn_1-xS@Au/BiVO₄ is identified by in-situ FT-IR, playing a key role in the conversion of CO₂ to CO and then improve photocatalytic selectivity.

The electrospun-assisted assembly of bismuth-modified BiVO4 porous nanofibers with enhanced photocatalytic performance

Bismuth vanadate (BiVO4) is a promising photocatalytic material for use in environmental protection and water splitting.

Plasmon Coupling-Induced Hot Electrons for Photocatalytic Hydrogen Generation

We present the fabrication of core-shell-satellite Au@SiO₂ -Pt nanostructures and demonstrate that LSPR excitation of the core Au nanoparticle can induce plasmon coupling effect to initiate photocatalytic hydrogen generation from decomposition of formic acid. Further studies suggest that the plasmon coupling effect induces a strong local electric field between the Au core and Pt nanoparticles on the SiO₂ shell, which enables creation of hot electrons on the non-plasmonic-active Pt nanoparticles to participate hydrogen evolution reaction on the Pt surface. In addition, small SiO₂ shell thickness is required in order to obtain a strong plamon coupling effect and achieve efficient photocatalytic activities for hydrogen generation.

Plasmonic Coupling Architectures for Enhanced Photocatalysis

Plasmonic photocatalysis is a promising approach for solar energy transformation. Comparing with isolated metal nanoparticles, the plasmonic coupling architectures can provide further strengthened local electromagnetic field and boosted light-harvesting capability through optimal control over the composition, spacing, and orientation of individual nanocomponents. As such, when integrated with semiconductor photocatalysts, the coupled metal nanostructures can dramatically promote exciton generation and separation through plasmonic-coupling-driven charge/energy transfer toward superior photocatalytic efficiencies. Herein, the principles of the plasmonic coupling effect are presented and recent progress on the construction of plasmonic coupling architectures and their integration with semiconductors for enhanced photocatalytic reactions is summarized. In addition, the remaining challenges as to the rational design and utilization of plasmon coupling structures are elaborated, and some prospects to inspire new opportunities on the future development of plasmonic coupling structures for efficient and sustainable light-driven reactions are raised.

Improvement in NO2 Gas Sensing Properties of Semiconductor-Type Sensors by Loading Pt into BiVO4 Nanocomposites at Room Temperature

In the present study, we report the first attempt to prepare a conducive environment for Pt/BiVO₄ nanocomposite material reusability for the promotion of sustainable development. Here, the Pt/BiVO₄ nanocomposite was prepared using a hydrothermal method with various weight percentages of platinum for use in NO₂ gas sensors. The surface morphologies and structure of the Pt/BiVO₄ nanocomposite were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The results showed that Pt added to BiVO₄ with 3 wt.% Pt/BiVO₄ was best at a concentration of 100 ppm NO₂, with a response at 167.7, and a response/recovery time of 12/35 s, respectively. The Pt/BiVO₄ nanocomposite-based gas sensor exhibits promising nitrogen dioxide gas-sensing characteristics, such as fast response, highly selective detection, and extremely short response/recovery time. Additionally, the mechanisms of gas sensing in Pt/BiVO₄ nanocomposites were explored in this paper.

A photo-Fenton nanocomposite ultrafiltration membrane for enhanced dye removal with self-cleaning properties

Membrane fouling is an ongoing challenge in the membrane filtration process. Herein, a photocatalytic membrane comprising a reactive layer was fabricated by engineering partially reduced graphene oxide/Ag nanoparticles/MIL-88A (prGO/Ag/M88A, pGAM) photocatalysts on the PVDF substrate membranes. Benefiting from the high conductivity of prGO and the surface plasmon resonance (SPR) effect of Ag nanoparticles (Ag NPs), the photo-sensitivity of the prGO/Ag/M88A is significantly enhanced. Compared to the membrane in the dark condition, the pGAM membrane displayed an enhanced dye removal efficiency (∼99.7%) and significantly improved permeability (∼189 L·m^-2·h^-1 bar^-1) towards dye contaminants based on the synergistic filtration/photo-Fenton processes. Significantly, the membrane retained high perm-selectivity after 10 cyclic runs (183 L·m^-2·h^-1 bar^-1 of permeability and 98.1% of dye removal), and its nano-channel structure did not collapse under high pressure (0.1-0.4 MPa). The membrane also exhibits antifouling properties with a high water flux recovery of more than 90%. In addition, the pGAM membrane exhibited a high MB degradation efficiency (∼90%) when it is directly used as a photocatalyst in the photo-Fenton system. The mechanism of the self-cleaning is also proposed through quenching experiments. The results of this study demonstrate that this self-cleaning membrane has huge promise for membrane anti-fouling and wastewater remediation.

Polymeric Carbon Nitride-Derived Photocatalysts for Water Splitting and Nitrogen Fixation

Photocatalysis is a promising energy conversion and environmental restoration technology. The main focus of photocatalysis is the development and manufacture of highly efficient photocatalysts. Semiconductor-based photocatalysis technology based on harnessing solar energy is considered as an attractive approach to solve the problems of global energy shortage and environmental pollution. Since 2009 pioneering work has been carried out on polymeric carbon nitride (PCN) for visible photocatalytic water splitting, thus PCN-based photocatalysis has become a hot research topic, demanding significant research attention. This article reviews the physical and chemical properties, synthesis methods, and the methods to control the morphology, heteroatom doping, and construction of heterojunctions to improve the performance of PCN-based photocatalysts in water splitting and nitrogen fixation. Through different design strategies, the photo-generated electron-hole pair separation efficiency of PCN materials can be effectively improved, thereby improving their photocatalytic performance. Finally, the challenges of PCN-based photocatalysts in water splitting and nitrogen fixation applications are discussed herein. It is strongly believed that through different design strategies, efficient PCN-based photocatalysts can be constructed for both water splitting and nitrogen reduction. These excellent modification strategies can be used as a guiding theory for photocatalytic reactions of other promising catalysts and further promote the development of photocatalysis.

Biomolecular l-tryptophan as a hole mediator anchored on g-C3N4 exhibits remarkably enhanced photocatalytic H2 evolution

A novel g-C₃N₄-based composite coupled with levorotatory-tryptophan restrains the recombination of photogenerated holes and electrons, exhibiting enhanced photocatalytic H₂ production.

Structural features and morphology of titanium dioxide–bismuth vanadate heterojunctions

Titanium dioxide TiO2 (TO) and bismuth vanadate BiVO4 (BVO) are promising photoactive semiconducting oxides for heterogeneous photocatalysis devoted to water treatment, pollutant degradation and water splitting processes.

Z-scheme BiVO4/Ag/Ag2S composites with enhanced photocatalytic efficiency under visible light

The Z-scheme BiVO4/Ag/Ag2S photocatalyst was fabricated via a two-step route. The as-prepared samples were characterized by XRD, FE-SEM, HRTEM, XPS and UV-vis diffuse reflectance spectroscopy. The results of PL and photocurrent response tests demonstrate that the ternary BiVO4/Ag/Ag2S composites had a high separation and migration efficiency of photoexcited carriers. As a result, the ternary photocatalyst exhibits enhanced photocatalytic activity for decomposing Rhodamine B (RhB) under LED light (420 nm) irradiation. The results of trapping experiments demonstrate both h+ and ˙OH play crucial roles in decomposing RhB molecules. Additionally, the energy band structures and density of states (DOS) of BiVO4 and Ag2S were investigated via the density functional theory (DFT) method. Finally, a Z-scheme electron migration mechanism of BiVO4 → Ag → Ag2S was proposed based on the experimental and calculated results.

Sepiolite supported BiVO4 nanocomposites for efficient photocatalytic degradation of organic pollutants: Insight into the interface effect towards separation of photogenerated charges

Although the construction of clay-supported photocatalyst is a promising strategy to develop the low cost and high activity photocatalyst, only few works researched the effect of their interfaces on the photocatalytic performance. Herein, a monoclinic BiVO₄/sepiolite nanocomposite was fabricated as case to study the transport mechanism of photogenerated carries based on the interfaces effect. The obtained BiVO₄/sepiolite nanocomposites exhibited excellent visible light photocatalytic performance. The photocatalytic degradation rates of antibiotic tetracyclines (TCs) and methylene blue (MB) by the nanocomposites are 2 and 5.34 times higher than that by pure BiVO₄ under visible light irradiation. XPS and Raman spectra confirmed the strong interfaces effect existing between BiVO₄ and sepiolite clay. Moreover, PL and transient photocurrent response suggested that the strong interfaces effect effectively promoted the separation of photogenerated electron-hole pairs and further enhanced the photocatalytic performance. In addition, the results of trapping experiments revealed that the photo-induced holes (h⁺) were the dominant active species in the photocatalytic mechanism. This work illuminates the photocatalytic mechanism of monoclinic BiVO₄/sepiolite nanocomposites and provides a novel strategy for designing the clay-supported photocatalyst for degradation of organic pollutants.

InGaN Nanorods Decorated with Au Nanoparticles for Enhanced Water Splitting Based on Surface Plasmon Resonance Effects

Photoelectrochemical (PEC) water splitting has great application potential in converting solar energy into hydrogen energy. However, what stands in the way of the practical application of this technology is the low conversion efficiency, which can be promoted by optimizing the material structure and device design for surface functionalization. In this work, we deposited gold nanoparticles (Au NPs) with different loading densities on the surface of InGaN nanorod (NR) arrays through a chemical solvent route to obtain a composite PEC water splitting system. Enhanced photocatalytic activity, which can be demonstrated by the surface plasmon resonance (SPR) effect induced by Au NPs, occurred and was further confirmed to be associated with the different loading densities of Au NPs. These discoveries use solar water splitting as a platform and provide ideas for exploring the mechanism of SPR enhancement.

The improvement of photocatalysis O2 production over BiVO4 with amorphous FeOOH shell modification

A novel amorphous FeOOH modified BiVO₄ photocatalyst (A-FeOOH/BiVO₄) was successfully produced and characterized by various techniques. The results showed that amorphous FeOOH with about 2 nm thickness evenly covered on BiVO₄ surface, which caused resultant A-FeOOH/BiVO₄ exhibiting higher visible light photocatalytic performance for producing O₂ from water than BiVO₄. When the covered amount of amorphous FeOOH was 8%, the resultant photocatalyst possessed the best photocatalytic performance. To find the reasons for the improvement of photocatalytic property, electrochemical experiments, DRS, PL and BET, were also measured, the experimental results indicated that interface effect between amorphous FeOOH and BiVO₄ could conduce to migration of photogenerated charge, and exhibit stronger light responded capacity. These positive factors promoted A-FeOOH/BiVO₄ presenting improved the photocatalytic performance. In a word, the combination of amorphous FeOOH with BiVO₄ is an effective strategy to conquer important challenges in photocatalysis field.

Understanding Reaction Kinetics by Tailoring Metal Co-catalysts of the BiVO4 Photocatalyst

In this study, the reaction mechanisms of metal-semiconductor composites used as photocatalysts were demonstrated by first preparing bismuth vanadate (BiVO₄) and then performing photodeposition of metal nanoparticles. The photocatalytic activity of metal-BiVO₄ (M-BiVO₄, where M = Pt, Au, Ag) composites were evaluated through dye decomposition under UV-vis irradiation. The photocatalytic efficiency was significantly enhanced after Pt deposition as compared to other M-BiVO₄ composites. The size or shape of BiVO₄ was not the main factor for the efficiency of Pt-BiVO₄. However, a deposited Pt co-catalyst was essential for the photocatalytic decomposition of dye on the BiVO₄ surface. Radical scavengers were employed to elucidate the reaction mechanism during the photocatalytic reaction with the Pt-BiVO₄ composite. This study provides details on the reaction mechanism of the photocatalytic reaction on Pt at the BiVO₄ surface under solar irradiation.

Engineering the Dimensional Interface of BiVO4-2D Reduced Graphene Oxide (RGO) Nanocomposite for Enhanced Visible Light Photocatalytic Performance

Graphene as a two-dimensional (2D) nanoplatform is beneficial for assembling a 2D heterojunction photocatalytic system to promote electron transfer in semiconductor composites. Here a BiVO₄ nanosheets/reduced graphene oxide (RGO) based 2D-2D heterojunction photocatalytic system as well as 0D-2D BiVO₄ nanoparticles/RGO and 1D-2D BiVO₄ nanotubes/RGO nanocomposites are fabricated by a feasible solvothermal process. During the synthesis; the growth of BiVO₄ and the intimate interfacial contact between BiVO₄ and RGO occur simultaneously. Compared to 0D-2D and 1D-2D heterojunctions, the resulting 2D-2D BiVO₄ nanosheets/RGO composites yield superior chemical coupling; leading to exhibit higher photocatalytic activity toward the degradation of acetaminophen under visible light irradiation. Photoluminescence (PL) and photocurrent experiments revealed that the apparent electron transfer rate in 2D-2D BiVO₄ nanosheets/RGO composites is faster than that in 0D-2D BiVO₄ nanoparticles/RGO composites. The experimental findings presented here clearly demonstrate that the 2D-2D heterojunction interface can highlight the optoelectronic coupling between nanomaterials and promote the electron–hole separation. This study will motivate new developments in dimensionality factors on designing the heterojunction photocatalysts and promote their photodegradation photocatalytic application in environmental issues.

Ultrathin MoS2 nanosheets for high-performance photoelectrochemical applications via plasmonic coupling with Au nanocrystals

In this work, we prepared ultrathin MoS2 nanosheets with exposed active edge sites and high electric conductivity that can sufficiently absorb light in the visible region to enable solar energy conversion. The gold nanocrystal-decorated MoS2 nanosheets facilitate sufficiently enhanced photoelectrochemical water splitting in the UV-visible region. Different Au nanostructures, such as Au nanoparticles and nanorods, were modified on the surface of MoS2 nanosheets to promote photoelectrochemical water decomposition. By spin-coating a synthetic gold-modified MoS2 hybrid photoanode on a FTO substrate, the efficiency of photoelectrochemical water oxidation was significantly enhanced, by 2 times (nanorods) and 3.5 times (nanoparticles) in the visible-infrared region; furthermore, the average optical resistance was reduced by a factor of two compared to the MoS2 photoanode without Au, and the photocurrent increases exponentially when the system bias was greater than 0.7 volts. The Au-MoS2 metal-semiconductor interface plays an important role in studying the surface plasmon interactions, charge transfer mechanism, and electric field amplification. This rational design for such a unique hybrid nanostructure explains the plasmon-enhanced photoelectrochemical water splitting. This current contribution provides a new path for using the plasmonic metal/semiconductor heterostructure to effectively harvest UV-visible light for solar fuel generation.

Fabrication of Cu2 O-based Materials for Lithium-Ion Batteries

The improvement of the performance of advanced batteries has played a key role in the energy research community since its inception. Therefore, it is necessary to explore high-performance materials for applications in advanced batteries. Among the variety of materials applied in batteries, much research has been dedicated to examine cuprous oxide materials as working electrodes in lithium cells to check their suitability as anodes for Li-ion cells and this has revealed great working capacities because of their specific characteristics (polymorphic forms, controllable structure, high cycling capacity, etc.). Thus, cuprous oxide and its composites will be fully introduced in this Review for their applications in advanced batteries. It is believed that, in the future, both the study and the impact of cuprous oxide and its composites will be much more profound and lasting.

Palladium nanoparticles and rGO co-modified BiVO4 with greatly improved visible light-induced photocatalytic activity

A ternary composite, Pd-rGO-BiVO₄, was fabricated with reduced graphene oxide (rGO) and palladium nanoparticles decorated on the surface of BiVO₄. As-prepared samples were tested for the photocatalytic degradation of phenol under visible light irradiation. Enhancement was observed for the ternary structure, merits of which may be as follows: 1) rGO wrapped BiVO₄ facilitated the photogenerated electrons transfer, 2) palladium nanoparticles served as electron acceptors, 3) palladium nanoparticles on the surface were capable of absorbing visible light photons. The uptake of photogenerated charge carriers would improve their separation and more oxidative species may be produced that can participate in the degradation of organics. Due to the SPR effect of palladium nanoparticles on the surface, the harvesting capacity of the photocatalyst to absorb visible light photons was increased, and thus its photocatalytic activity was improved. It should be noted that phenol was more easily adsorbed by rGO due to the π-π interaction between rGO and phenol, which also contributed to the enhancement in the photocatalytic activity. This work provides new evidence to confirm the advances of ternary structures applied in the photocatalytic removal of phenolic compounds in water under visible light irradiation.

Fabrication of Ag-decorated BiOBr-mBiVO4 dual heterojunction composite with enhanced visible light photocatalytic performance for degradation of malachite green

A visible light active Ag-decorated BiVO₄-BiOBr dual heterojunction photocatalyst was prepared using a facile hydrothermal method, followed by the photodeposition of Ag. The photocatalytic activity of the synthesized samples was investigated by monitoring the change in malachite green (MG) concentration upon visible light irradiation. The synthesized sample was highly effective for the degradation of non-biodegradable MG. The enhanced activity observed was ascribed to the efficient separation and transfer of charge carriers across the dual heterojunction structure as verified by photoluminescence measurements. The removal of MG was primarily initiated by hydroxyl radicals and holes based on scavenger's effect. To gain insight into the degradation mechanism, both high performance liquid chromatography and high resolution-quantitative time of flight, electrospray ionization mass spectrometry measurements during the degradation process were carried out. The degradation primarily followed the hydroxylation and N-demethylation process. A possible reaction pathway is proposed on the basis of all the information obtained under various experimental conditions.

Rapid Formation of a Disordered Layer on Monoclinic BiVO4 : Co-Catalyst-Free Photoelectrochemical Solar Water Splitting

A surface disordered layer is a plausible approach to improve the photoelectrochemical performance of TiO₂ . However, the formation of a crystalline disordered layer in BiVO₄ and its effectiveness towards photoelectrochemical water splitting has remained a big challenge. Here, we report a rapid solution process (within 5 s) that is able to form a disordered layer of a few nanometers thick on the surface of BiVO₄ nanoparticles using a specific solution with a controllable reducing power. The disordered layer on BiVO₄ alleviates charge recombination at the electrode-electrolyte interface and reduces the onset potential greatly, which in turn results in a photocurrent density of approximately 2.3 mA cm^-2 at 1.23 V versus the reversible hydrogen electrode (RHE). This value is 2.1 times higher than that of bare BiVO₄ . The enhanced photoactivity is attributed to the increased charge separation and transfer efficiencies, which resolve the intrinsic drawbacks of bare BiVO₄ such as the short hole diffusion length of around 100 nm and poor surface oxygen evolution reactivity.