B and N Codoped Cellulose-Supported Ag-/Bi-Doped Mo(S,O)3 Trimetallic Sulfo-Oxide Catalyst for Photocatalytic H2 Evolution Reaction and 4-Nitrophenol Reduction

Cellulose plays a significant role in designing efficient and stable cellulose-based metallic catalysts, owing to its surface functionalities. Its hydroxyl groups are used as anchor sites for the nucleation and growth of metallic nanoparticles and, as a result, improve the stability and catalytic activity. Meanwhile, cellulose is also amenable to surface modifications to be more suitable for incorporating and stabilizing metallic nanoparticles. Herein, the Ag-/Bi-doped Mo(S,O)3 trimetallic sulfo-oxide anchored on B and N codoped cellulose (B-N-C) synthesized by a facile approach showed excellent stability and catalytic activity for PHER at 573.28 μmol/h H2 with 25 mg of catalyst under visible light, and 92.3% of the 4-nitrophenol (4-NP) reduction was achieved within 135 min by in situ-generated protons. In addition to B and N codoping, our use of the calcination method for B-N-C preparation further increases the structural disorders and defects, which act as anchoring sites for Ag-/Bi-doped Mo(S,O)3 nanoparticles. The Ag-/Bi-doped Mo(S,O)3@B-N-C surface active site also stimulates H2O molecule adsorption and activation kinetics and reduces the photogenerated charge carrier's recombination rate. The Mo4+ → Mo6+ electron hopping transport and the O 2p and Bi 6s orbital overlap facilitate the fast electron transfer by enhancing the electron's lifetime and photoinduced charge carrier mobility, respectively. In addition to acting as a support, B-N-C provides a highly conductive network that enhances charge transport, and the relocated electron in B-N-C activates the H2O molecule, which enables Ag-/Bi-doped Mo(S,O)3@B-N-C to have appreciable PHER performance.

Double metals sites synergistically enhanced photocatalytic N2 fixation performance over Bi24O31Br10@Bi/Ti3C2Tx Ohm junctions

At present, it is a research hotspot to realize green synthetic ammonia by using solar energy. Exploring cheap and efficient co-catalysts for enhancing the performance of photocatalysts is a challenge in the field of energy conversion. In order to boost the charge separation/transfer of the photocatalyst and widen the visible light absorption, Bi24O31Br10@Bi/Ti3C2Tx with double Ohm junction is successfully fabricated by in situ growth of metal Bi and loading Ti3C2Tx MXene on the surface of Bi24O31Br10. The dual active sites of Bi and Ti3C2Tx MXene not only broaden the light adsorption of Bi24O31Br10 but also serve as excellent 'electronic receptor' for synergically enhancing the separation/transfer efficiency of photogenerated electrons/holes. Meanwhile, temperature programmed desorption (TPD) result revealed that MXene and Bi can promote N2 adsorption/activation and NH3 desorption over Bi24O31Br10@Bi/Ti3C2Tx. As a result, under mild conditions and without the presence of hole scavenger, the ammonia synthesis efficiency of Bi24O31Br10@Bi/Ti3C2Tx-20 % reached 53.86 μmol g-1cat for three hours which is 3.2 and 53.8 times of Bi24O31Br10 and Ti3C2Tx, respectively. This study offers a novel scheme for the construction of photocatalytic systems and demonstrates Ti3C2Tx MXene and metal Bi as a promising and cheap co-catalyst.

An overview on recent progress in photocatalytic air purification: Metal-based and metal-free photocatalysis

Air pollution is becoming a distinctly growing concern and the most pressing universal problem as a result of increased energy consumption, with the multiplication of the human population and industrial enterprises, resulting in the generation of hazardous pollutants. Among these, carbon monoxide, nitrogen oxides, Volatile organic compounds, Semi volatile organic compounds, and other inorganic gases not only have an adverse impact on human health both outdoors and indoors, but have also substantially altered the global climate, resulting in several calamities around the world. Thus, the purification of air is a crucial matter to deal with. Photocatalytic oxidation is one of the most recent and promising technologies, and it has been the subject of numerous studies over the past two decades. Hence, the photocatalyst is the most reassuring aspirant due to its adequate bandgap and exquisite stability. The process of photocatalysis has provided many benefits to the atmosphere by removing pollutants. In this review, our work focuses on four main themes. Firstly, we briefly elaborated on the general mechanism of air pollutant degradation, followed by an overview of the typical TiO₂ photocatalyst, which is the most researched photocatalyst for photocatalytic destruction of gaseous VOCs. The influence of operating parameters influencing the process of photocatalytic oxidation (such as mass transfer, light source and intensity, pollutant concentration, and relative humidity) was then summarized. Afterwards, the progress and drawbacks of some typical photoreactors (including monolithic reactors, microreactors, optical fiber reactors, and packed bed reactors) were described and differentiated. Lastly, the most noteworthy coverage is dedicated to different types of modification strategies aimed at ameliorating the performance of photocatalysts for degradation of air pollutants, which were proposed and addressed. In addition, the review winds up with a brief deliberation for more exploration into air purification photocatalysis.

Bi-based photocatalysts for bacterial inactivation in water: Inactivation mechanisms, challenges, and strategies to improve the photocatalytic activity

Bi-based photocatalysts have been considered suitable materials for water disinfection under natural solar light due to their outstanding optical and electronic properties. However, until now, there are not extensive reviews about the development of Bi-based materials and their application in bacterial inactivation in aqueous solutions. For this reason, this work has focused on summarizing the state of the art related to the inactivation of Gram- and Gram + pathogenic bacteria under visible light irradiation using different Bi-based micro and nano structures. In this sense, the photocatalytic bacterial inactivation mechanisms are analyzed, considering several modifications. The factors that can affect the photocatalytic performance of these materials in real conditions and at a large scale (e.g., water characteristics, pH, light intensity, photocatalyst dosage, and bacteria level) have been studied. Furthermore, current alternatives for improving the photocatalytic antibacterial activity and reuse of Bi-based materials (e.g., surface engineering, crystal facet engineering, doping, noble metal coupling, heterojunctions, Z-scheme junctions, coupling with graphene derivatives, magnetic composites, immobilization) have been explored. According to several reports, inactivation rate values higher than 90% can be achieved by using the modified Bi-based micro/nano structures, which become them excellent candidates for photocatalytic water disinfection. However, these innovative photocatalytic materials bring a variety of future difficulties and opportunities in water disinfection.

Influence of oxygen vacancy defects on Aurivillius phase layered perovskite oxides of bismuth towards photocatalytic environmental remediation

The low light absorption and rapid recombination of photogenerated charge carriers are primary contributors to the low activity of various photocatalysts. Fabrication of oxygen vacancy defect-rich materials for improved photocatalytic activities has been attracting tremendous attention from researchers all over the world. In this work, we have compared the photocatalytic activities of oxygen vacancy-rich Bi₂MoO₆(BMO-O_V) and Bi₂WO₆(BWO-O_V) for the degradation of a model pharmaceutical pollutant, ciprofloxacin under visible light irradiation. The photocatalytic activity was increased from 47% to 77% and 40% to-67% for BMO-O_Vand BWO-O_V, respectively in comparison to pristine oxides. This enhancement can be ascribed to suppressed charge carrier recombination and increased surface active sites. In addition, scavenger studies have been done to explain the role of photoinduced charge carriers in the degradation mechanism. Moreover, oxygen vacancy-rich photocatalysts have remained stable even after three consecutive cycles, making them promising materials for practical applications. Overall, this work provides deeper insight into the design and development of oxygen vacancy-rich materials.

Bismuth-based complex oxides for photocatalytic applications in environmental remediation and water splitting: A review

As an emerging group of visible-light-driven photocatalysts, bismuth-based complex oxides have attracted considerable attention owing to their outstanding photo-oxidation ability and high performance in decomposition of organic contaminants and water oxidation via photocatalytic processes. However, the relatively low level of the conduction band limits their further application in photocatalytic hydrogen evolution and overall water splitting processes. In this paper, three representative and most-studied Bi-based complex oxides of BiOX (X = Cl, Br, I)/BiFeO₃/Bi₂WO₆ are discussed mainly for environmental pollutants degradation and oxygen generation from water splitting. We present a comprehensive overview of their fundamental compositions, electronic structures and synthesis strategies. On the basis of analyzing the structural-property-activity relationships, detailed approaches for enhancement of their photocatalytic performance have been addressed and compared including morphology/facets control, heterostructures construction and introduction of oxygen vacancies. In addition, several techniques such as engineering energy band and building a Z-scheme system have been proposed to modulate the energy band positions of the photocatalysts and overcome the bottleneck to realize overall water splitting into H₂ and O₂ simultaneously. Finally, remarks on the current challenges, research directions and future perspectives are presented to provide guidance for designing and configuring highly efficient solar-light-driven photocatalysts in the field of environmental purification and energy conversion.

Recent advances in photocatalytic remediation of emerging organic pollutants using semiconducting metal oxides: an overview

Many untreated and partly treated wastewater from the home and commercial resources is being discharged into the aquatic environment these days, which contains numerous unknown and complex natural and inorganic compounds. These compounds tend to persist, initiating severe environmental problems, which affect human health. Conventionally, physicochemical treatment methods were adopted to remove such complex organic chemicals, but they suffer from critical limitations. Over time, photocatalysis, an advanced oxidation process, has gained its position for its efficient and fair performance against emerging organic pollutant decontamination. Typically, photocatalysis is a green technology to decompose organics under UV/visible light at ambient conditions. Semiconducting nanometal oxides have emerged as pioneering photocatalysts because of large active surface sites, flexible oxidation states, various morphologies, and easy preparation. The current review presents an overview of emerging organic pollutants and their effects, advanced oxidation processes, photocatalytic mechanism, types of photocatalysts, photocatalyst support materials, and methods for improving photodegradation efficiency on the degradation of complex emerging organic pollutants. In addition, the recent reports of metal-oxide-driven photocatalytic remediation of emerging organic pollutants are presented in brief. This review is anticipated to reach a broader scientific community to understand the first principles of photocatalysis and review the recent advancements in this field.

Synthesis and Enhanced Light Photocatalytic Activity of Modulating Band BiOBrXI1-X Nanosheets

The photocatalysis technique has been proven to be a promising method to solve environmental pollution in situations of energy shortage, and has been intensively investigated in the field of pollutant degradation. In this work, a band structure-controlled solid solution of BiOBr_XI_1−X (x = 0.00, 0.05, 0.10, 0.15, 0.20, 1.00) with highly efficient light-driven photocatalytic activities was successfully synthesized via simple solvothermal methods. The phase composition, crystal structure, morphology, internal molecular vibration, optical properties, and energy band structure were characterized and analyzed by XRD, SEM, HRTEM, XPS, Raman, and UV Vis DRS. To evaluate the photocatalytic activity of BiOBr_XI_1−X, rhodamine B was selected as an organic pollutant. In particular, BiOBr_0.15I_0.85 displayed significantly enhanced photocatalytic activity by virtue of modulating the energy band position, optimizing redox potentials, and accelerating carrier separation. Moreover, the enhancement mechanism was elucidated on the basis of band structure engineering, which provides ideas for the design of highly active photocatalysts for practical application in the fields of environmental issues and energy conservation.

A highly sensitive photoelectrochemical aptasensor based on BiVO4 nanoparticles-TiO2 nanotubes for detection of PCB72

In this work, a simple and highly sensitive photoelectrochemical (PEC) aptasensor has been developed for detecting PCB72 based on TiO₂ nanotubes (NTs) decorated with BiVO₄ nanoparticles (NPs). The BiVO₄ NPs-TiO₂ NTs composites prepared through a simple hydrothermal method exhibit good visible-light adsorption ability, high PEC response and perfect photo-excited stability. The synthesized composites were explored as the photoactive sensing materials for development of a PEC sensing platform for the first time. Here, Au nanoparticles (NPs) were first deposited the composites, and the anti-PCB72 aptamer molecules were immobilized on the Au NPs-deposited BiVO₄ NPs-TiO₂ NTs. The developed PEC aptasensor exhibits high sensitivity and specificity for PCB72 with a wide linear range from 1 ng/L to 500 ng/L and a low detection limit of 0.23 ng/L. The application of the aptasensor was evaluated by determining PCB 72 in the environment water samples. Thus, a simple and efficient PEC sensing platform was established for detecting the content of PCBs in the environment.

ZnO Nanospheres Fabricated by Mechanochemical Method with Photocatalytic Properties

The preparation of high specific area (86.5 m2/g) ZnO nanospheres with good photocatalytic efficiency via a simple, green and efficient mechanochemical method was reported in this work. The products were characterized by XRD, SEM, TEM, BET and UV–Vis. The ball milling parameters were improved to reduce the agglomeration hazard during the ball milling process, and the specific surface area, band gap and photocatalytic efficiency were investigated in relation to ball milling time. Our study developed the opportunity for the low-cost and facile synthesis of a high specific surface area photocatalyst on a large scale for future industrial applications.

Intramolecular Photoelectrochemical System Using Tyrosine-Modified Antibody-Targeted Peptide as Electron Donor for Detection of Biomarkers

An intramolecular photoelectrochemical (PEC) system is designed from the novel electron donor YYYHWRGWV (Y3-H) peptide ligand for the first time. The bifunctional nonapeptide cannot only rely on the HWRGWV sequence as a site-oriented immobilizer to recognize the crystallizable fragment (Fc) domains of the antibody but also acts as electron donors for PEC generation via three tyrosine (Y) of the N-terminal. The Bi₂WO₆/AgInS₂ heterojunction with a significant visible-light absorption is utilized as a photoelectric generator, and the motivation is ascribed to a proven proposition, namely, that short-wavelength illuminant radiates proteins, causing a decline in bioactivity of immune protein. An innovative biosensor is fabricated using the above strategies for the detection of CYFRA21-1, a biomarker of squamous cell lung carcinoma. This sort of PEC-based sensing platform shows convincing experimental data and could be an effective candidate for clinical application in the future due to their extremely skillful conception.

One-Step Synthesis of Hierarchical Flower-like SnO2/BiOCOOH Microspheres with Enhanced Light Response for the Removal of Pollutants

The low separation rate of electron-hole pairs in single-component photocatalysts severely limits their applications for wastewater treatment. For this study, SnO₂/BiOCOOH photocatalysts in flower-like microspheres were controllably synthesized via a one-step hydrothermal method and were characterized by various advanced techniques. These SnO₂/BiOCOOH nanocomposites demonstrated excellent photocatalytic activities for the degradation of rhodamine B (RhB), titan yellow, and levofloxacin hydrochloride (LVF). Specifically, 98.5% of RhB, 80% of titan yellow, and 85% of LVF were degraded under 5 W LED (λ = 365 nm) light irradiation within 30, 40, and 60 min, respectively. Radical trapping experiments and electron spin resonance results indicated that h⁺ was the dominant active radical, whereas ·O₂^- and ·OH played an auxiliary role in the photocatalytic system. Subsequently, a potential photocatalytic mechanism was proposed based on the experimental results.

Femtosecond-laser-irradiation-induced structural organization and crystallinity of Bi2WO6

Controlling the structural organization and crystallinity of functional oxides is key to enhancing their performance in technological applications. In this work, we report a strong enhancement of the structural organization and crystallinity of Bi2WO6 samples synthetized by a microwave-assisted hydrothermal method after exposing them to femtosecond laser irradiation. X-ray diffraction, UV-vis and Raman spectroscopies, photoluminescence emissions, energy dispersive spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy were employed to characterize the as-synthetized samples. To complement and rationalize the experimental results, first-principles calculations were employed to study the effects of femtosecond laser irradiation. Structural and electronic effects induced by femtosecond laser irradiation enhance the long-range crystallinity while decreasing the free carrier density, as it takes place in the amorphous and liquid states. These effects can be considered a clear cut case of surface-enhanced Raman scattering.

Synthesis and characterization of BiVO4 nanoparticles for environmental applications

In the present study, a chemical precipitation method is adopted to synthesize bismuth vanadate nanoparticles. The calcination temperature dependent photocatalytic and antibacterial activities of BiVO₄ nanoparticles are examined. The structural analysis evidences the monoclinic phase of BiVO₄ nanoparticles, where the grain size increases with calcination temperature. Interestingly, BiVO₄ nanoparticles calcined at 400 °C exhibit superior photocatalytic behaviour against methylene blue dye (K = 0.02169 min⁻¹) under natural solar irradiation, which exhibits good stability for up to three cycles. The evolution of antibacterial activity studies using a well diffusion assay suggest that the BiVO₄ nanoparticles calcined at 400 °C can act as an effective growth inhibitor of pathogenic Gram-negative (P. aeruginosa & A. baumannii) and Gram-positive bacteria (S. aureus).

In the present study, a chemical precipitation method is adopted to synthesize bismuth vanadate nanoparticles.

Visible-light photocatalytic performance, recovery and degradation mechanism of ternary magnetic Fe3O4/BiOBr/BiOI composite

The ternary magnetic Fe₃O₄/BiOBr/BiOI (x : 3 : 1) photocatalysts were successfully synthesized by a facile solvothermal method. The samples were characterized by XRD, SEM, EDS, ICP-AES, XPS, UV-vis DRS, PL and VSM. Nitrogen-containing dye RhB was used as a degradation substrate to evaluate the photocatalytic degradation activities of the samples. The photocatalytic performance of Fe₃O₄/BiOBr/BiOI (0.4 : 3 : 1) is superior to other Fe₃O₄/BiOBr/BiOI (x : 3 : 1). Compared with binary magnetic Fe₃O₄/BiOBr (0.5 : 1) prepared in our previous work, the Fe₃O₄/BiOBr/BiOI (0.4 : 3 : 1) has obvious advantages in photocatalytic activity and adsorption capacity. And the specific surface area (48.30 m² g⁻¹) is much larger than that of the previous report (Fe₃O₄/BiOBr/BiOI (0.5 : 2 : 2)) synthesized by a co-precipitation method. Besides, after 25 s of magnetic field, Fe₃O₄/BiOBr/BiOI (0.4 : 3 : 1) can be rapidly separated from water. After eight recycling cycles, the magnetic properties, photocatalytic activity, crystallization and morphology of the Fe₃O₄/BiOBr/BiOI (0.4 : 3 : 1) catalyst remain good. The possible photocatalytic degradation mechanism of RhB under Fe₃O₄/BiOBr/BiOI (0.4 : 3 : 1) photocatalyst was also proposed. The results indicate that the ternary magnetic Fe₃O₄/BiOBr/BiOI (0.4 : 3 : 1) composite with high photocatalytic degradation efficiency, good magnetic separation performance and excellent recyclability and stability has potential application prospect in wastewater.

The ternary magnetic Fe₃O₄/BiOBr/BiOI (x : 3 : 1) photocatalysts were successfully synthesized by a facile solvothermal method.

Electrochemical Oxidation of Organic Pollutants Powered by a Silicon-Based Solar Cell

Currently available (photo-)electrochemical technologies for water treatment establish a trade-off between low-pollutant concentration and costs. This paper aims at decoupling these two variables by designing a photo-oxidation device using earth abundant materials and an electronic-free approach. The proposed device combines a graphite/graphite electrochemical system with a silicon-based solar cell that provides the necessary electrical power. First, the optimum operational voltage for the graphite/graphite electrochemical system was found to be around 1.6 V. That corresponded closely to the voltage produced by an a-Si:H/a-Si:H tandem solar cell of approximately 1.35 V. This configuration was shown to provide the best pollutant degradation in relation to the device area, removing 70% of the initial concentration of phenol and 90% of the methylene blue after 4 h of treatment. The chemical oxygen demand (COD) removal of these two contaminants after 4 h of treatment was also promising, 55 and 30%, respectively. Moreover, connecting several solar cells in series led to higher pollutant degradation but lower COD removal, suggesting that the degradation of the intermediate components is a limiting factor. This is expected to be due to the higher currents achieved by the series-connected configuration, which would favor other reactions such as polymerization over the degradation of intermediate species.

Improving the Photo-Oxidative Performance of Bi2MoO6 by Harnessing the Synergy between Spatial Charge Separation and Rational Co-Catalyst Deposition

It has been reported that photogenerated electrons and holes can be directed toward specific crystal facets of a semiconductor particle, which is believed to arise from the differences in their surface electronic structures, suggesting that different facets can act as either photoreduction or photo-oxidation sites. This study examines the propensity for this effect to occur in faceted, plate-like bismuth molybdate (Bi₂MoO₆), which is a useful photocatalyst for water oxidation. Photoexcited electrons and holes are shown to be spatially separated toward the {100} and {001}/{010} facets of Bi₂MoO₆, respectively, by facet-dependent photodeposition of noble metals (Pt, Au, and Ag) and metal oxides (PbO₂, MnO _x, and CoO _x). Theoretical calculations revealed that differences in energy levels between the conduction bands and valence bands of the {100} and {001}/{010} facets can contribute to electrons and holes being drawn to different surfaces of the plate-like Bi₂MoO₆. Utilizing this knowledge, the photo-oxidative capability of Bi₂MoO₆ was improved by adding an efficient water oxidation co-catalyst, CoO _x, to the system, whereby the extent of enhancement was shown to be governed by the co-catalyst location. A greater oxygen evolution occurred when CoO _x was selectively deposited on the hole-rich {001}/{010} facets of Bi₂MoO₆ compared to when CoO _x was randomly located across all of the facets. The elevated performance exhibited for the selectively loaded CoO _x/Bi₂MoO₆ was ascribed to the greater opportunity for hole trapping by the co-catalyst being accentuated over other potentially detrimental effects, such as the co-catalyst acting as a recombination medium and/or covering reactive sites. The results indicate that harnessing the synergy between the spatial charge separation and the co-catalyst location on the appropriate facets of plate-like Bi₂MoO₆ can promote its photocatalytic activity.

Structure of flower-like hierarchical CdS QDs/Bi/Bi2WO6 heterojunction with enhanced photocatalytic activity

A CdS QDs/Bi/Bi₂WO₆ heterojunction was synthesized via a facile stepwise in situ reduction and deposition process.

Pyrophosphate effect on the photocatalytic degradation of phenol over bare and Pt-deposited Bi2WO6

Pyrophosphate-mediated hole transfer from Pt/Bi₂WO₆to phenol can accelerate phenol degradation in aqueous solutions.

Nanostructured Ternary Metal Tungstate-Based Photocatalysts for Environmental Purification and Solar Water Splitting: A Review

Visible-light-responsive ternary metal tungstate (MWO₄) photocatalysts are being increasingly investigated for energy conversion and environmental purification applications owing to their striking features, including low cost, eco-friendliness, and high stability under acidic and oxidative conditions. However, rapid recombination of photoinduced electron-hole pairs and a narrow light response range to the solar spectrum lead to low photocatalytic activity of MWO₄-based materials, thus significantly hampering their wide usage in practice. To enable their widespread practical usage, significant efforts have been devoted, by developing new concepts and innovative strategies. In this review, we aim to provide an integrated overview of the fundamentals and recent progress of MWO₄-based photocatalysts. Furthermore, different strategies, including morphological control, surface modification, heteroatom doping, and heterojunction fabrication, which are employed to promote the photocatalytic activities of MWO₄-based materials, are systematically summarized and discussed. Finally, existing challenges and a future perspective are also provided to shed light on the development of highly efficient MWO₄-based photocatalysts.

Solar Water Splitting and Nitrogen Fixation with Layered Bismuth Oxyhalides

Hydrogen and ammonia are the chemical molecules that are vital to Earth's energy, environmental, and biological processes. Hydrogen with renewable, carbon-free, and high combustion-enthalpy hallmarks lays the foundation of next-generation energy source, while ammonia furnishes the building blocks of fertilizers and proteins to sustain the lives of plants and organisms. Such merits fascinate worldwide scientists in developing viable strategies to produce hydrogen and ammonia. Currently, at the forefronts of hydrogen and ammonia syntheses are solar water splitting and nitrogen fixation, because they go beyond the high temperature and pressure requirements of methane stream reforming and Haber-Bosch reaction, respectively, as the commercialized hydrogen and ammonia production routes, and inherit the natural photosynthesis virtues that are green and sustainable and operate at room temperature and atmospheric pressure. The key to propelling such photochemical reactions lies in searching photocatalysts that enable water splitting into hydrogen and nitrogen fixation to make ammonia efficiently. Although the past 40 years have witnessed significant breakthroughs using the most widely studied TiO₂, SrTiO₃, (Ga_1-xZn_x)(N_1-xO_x), CdS, and g-C₃N₄ for solar chemical synthesis, two crucial yet still unsolved issues challenge their further progress toward robust solar water splitting and nitrogen fixation, including the inefficient steering of electron transportation from the bulk to the surface and the difficulty of activating the N≡N triple bond of N₂. This Account details our endeavors that leverage layered bismuth oxyhalides as photocatalysts for efficient solar water splitting and nitrogen fixation, with a focus on addressing the above two problems. We first demonstrate that the layered structures of bismuth oxyhalides can stimulate an internal electric field (IEF) that is capable of efficiently separating electrons and holes after their formation and of precisely channeling their migration from the bulk to the surface along the different directions, thus enabling more electrons to reach the surface for water splitting and nitrogen fixation. Simultaneously, their oxygen termination feature and the strain differences between interlayers and intralayers render the easy generation of surface oxygen vacancies (OVs) that afford Lewis-base and unsaturated-unsaturated sites for nitrogen activation. With these rationales as the guideline, we can obtain striking visible-light hydrogen- and ammonia-evolving rates without using any noble-metal cocatalysts. Then we show how to utilize IEF and OV based strategies to improve the solar water splitting and nitrogen fixation performances of bismuth oxyhalide photocatalysts. Finally, we highlight the challenges remaining in using bismuth oxyhalides for solar hydrogen and ammonia syntheses, and the prospect of further development of this research field. We believe that our mechanistic insights could serve as a blueprint for the design of more efficient solar water splitting and nitrogen fixation systems, and layered bismuth oxyhalides might open up new photocatalyst paradigm for such two solar chemical syntheses.

Low-temperature fabrication of Bi25FeO40/rGO nanocomposites with efficient photocatalytic performance under visible light irradiation

Bismuth ferrite/reduced graphene oxide (Bi₂₅FeO₄₀/rGO) nanocomposites have been synthesized by a hydrothermal method, followed by a simple room temperature liquid phase process.

Band-gap engineering of porous BiVO4 nanoshuttles by Fe and Mo co-doping for efficient photocatalytic water oxidation

We demonstrate the first synthesis of uniform Fe and Mo co-doped BiVO₄ (Fe/Mo-BVO) porous nanoshuttles (PNSs) through a simple solvothermal method combined with a subsequent impregnation thermal treatment.

Fabrication of porous nanoflake BiMO x (M = W, V, and Mo) photoanodes via hydrothermal anion exchange

Most Bi-based photoelectrodes have suitable band gaps and can effectively promote the water oxidation reaction. However, simple preparation methods for Bi-based binary metal oxides as photoanodes are scarce. This paper describes a simple hydrothermal anion exchange method to synthesize Bi-based binary metal oxides with controlled morphologies. This synthesis process uses BiOI as the template and Bi source, which is eventually converted to Bi-based porous nanoflake photoanodes upon reaction with MO _x (M = W, V, and Mo)-containing precursors. The photoanodes show well-shaped porous nanoflake morphologies and exhibit impressive photoelectrochemical properties compared to Bi-based photoanodes synthesized by conventional methods. These three samples possess long-term stability under solar irradiation and show considerable photocurrent for sulfite oxidation.