An Elemental Phosphorus Photocatalyst with a Record High Hydrogen Evolution Efficiency

Transforming Red Phosphorus Photocatalysis: Dual Roles of Pre-Anchored Ru Single Atoms in Defect and Interface Engineering

Crystalline red phosphorus (CRP), known for its promising photocatalytic properties, faces challenges in photocatalytic hydrogen evolution (PHE) due to undesired inherent charge deep trapping and recombination effects induced by defects. This study overcomes these limitations through an innovative strategy in integrating ruthenium single atoms (Ru1) within CRP to simultaneously repair the intrinsic undesired vacancy defects and serve as the uniformly distributed anchoring sites for a controllable growth into ruthenium nanoparticles (RuNP). Hence, a highly functionalized CRP with Ru1 and RuNP (Ru1-NP/CRP) with concerted effects in regulating electronic structures and promoting interfacial charge transfer has been achieved. Advanced characterizations unveil the pioneering dual role of pre-anchored Ru1 (analogous to the "Tai Chi" principle) in transforming CRP photocatalysis. The regulations of vacancy defects on the surface of CRP minimize the detrimental deep charge trapping, resulting in the prolonged lifetime of active charges. With the well-distributed in situ growth of RuNP on Ru1 sites, the constructed robust "bridge" that connects CRP and RuNP facilitates constructive interfacial charge transfer. Ultimately, the synergistic effect induced by the pre-anchored Ru1 endows Ru1-NP/CRP with an exceptional PHE rate of 3175 μmol h-1 g-1, positioning it as one of the most efficient elemental-based photocatalysts available. This breakthrough underscores the crucial role of pre-anchoring metal single atoms at defect sites of catalysts in enhancing sustainable hydrogen production.

Quasi-One-Dimensional Fibrous Phosphorus: An Air-Stable Low-Symmetry Semiconductor with High Anisotropy

Due to their novel optical and optoelectronic properties, 2D materials have received increasing interest for optoelectronics applications. However, when the width of the channel layer decreases to the nanoscale, the properties of 2D materials can be seriously influenced due to the boundary defects and the approximation of physical dimensions and mean free path of the electron. That brings many challenges to developing novel electronics. Hence, researchers began to maintain their focus on 1D semiconductors without boundary defects and surfaces. Herein, fibrous phosphorus, another Quasi-1D layered semiconducting phosphorus allotrope with air-stable low symmetry, is reported. We found the in-plane anisotropic Raman response and excitation and exciton emission at room temperature. Moreover, the raw materials of fibrous phosphorus are nontoxic and abundant on the earth. These excellent properties will make it a highly competitive material for future applications in the optoelectronic area.

Renaissance of elemental phosphorus materials: properties, synthesis, and applications in sustainable energy and environment

The polymorphism of phosphorus-based materials has garnered much research interest, and the variable chemical bonding structures give rise to a variety of micro and nanostructures. Among the different types of materials containing phosphorus, elemental phosphorus materials (EPMs) constitute the foundation for the synthesis of related compounds. EPMs are experiencing a renaissance in the post-graphene era, thanks to recent advancements in the scaling-down of black phosphorus, amorphous red phosphorus, violet phosphorus, and fibrous phosphorus and consequently, diverse classes of low-dimensional sheets, ribbons, and dots of EPMs with intriguing properties have been produced. The nanostructured EPMs featuring tunable bandgaps, moderate carrier mobility, and excellent optical absorption have shown great potential in energy conversion, energy storage, and environmental remediation. It is thus important to have a good understanding of the differences and interrelationships among diverse EPMs, their intrinsic physical and chemical properties, the synthesis of specific structures, and the selection of suitable nanostructures of EPMs for particular applications. In this comprehensive review, we aim to provide an in-depth analysis and discussion of the fundamental physicochemical properties, synthesis, and applications of EPMs in the areas of energy conversion, energy storage, and environmental remediation. Our evaluations are based on recent literature on well-established phosphorus allotropes and theoretical predictions of new EPMs. The objective of this review is to enhance our comprehension of the characteristics of EPMs, keep abreast of recent advances, and provide guidance for future research of EPMs in the fields of chemistry and materials science.

Spontaneous Formation of Low Valence Copper on Red Phosphorus to Effectively Activate Molecular Oxygen for Advanced Oxidation Process

Efficient spontaneous molecular oxygen (O₂) activation is an important technology in advanced oxidation processes. Its activation under ambient conditions without using solar energy or electricity is a very interesting topic. Low valence copper (LVC) exhibits theoretical ultrahigh activity toward O₂. However, LVC is difficult to prepare and suffers from poor stability. Here, we first report a novel method for the fabrication of LVC material (P-Cu) via the spontaneous reaction of red phosphorus (P) and Cu²⁺. Red P, a material with excellent electron donating ability and can directly reduce Cu²⁺ in solution to LVC via forming Cu-P bonds. With the aid of the Cu-P bond, LVC maintains an electron-rich state and can rapidly activate O₂ to produce ·OH. By using air, the ·OH yield reaches a high value of 423 μmol g^-1 h^-1, which is higher than traditional photocatalytic and Fenton-like systems. Moreover, the property of P-Cu is superior to that of classical nano-zero-valent copper. This work first reports the concept of spontaneous formation of LVC and develops a novel avenue for efficient O₂ activation under ambient conditions.

Synthesis of Fibrous Phosphorus Micropillar Arrays with Pyro-Phototronic Effects

The bottom-up preparation of two-dimensional material micro-nano structures at scale facilitates the realisation of integrated applications in optoelectronic devices. Fibrous Phosphorus (FP), an allotrope of black phosphorus (BP), is one of the most promising candidate materials in the field of optoelectronics with its unique crystal structure and properties.^[1] However, to date, there are no bottom-up micro-nano structure preparation methods for crystalline phosphorus allotropes.^[1c, 2] Herein, we present the bottom-up preparation of fibrous phosphorus micropillar (FP-MP) arrays via a low-pressure gas-phase transport (LP-CVT) method that controls the directional phase transition from amorphous red phosphorus (ARP) to FP. In addition, self-powered photodetectors (PD) of FP-MP arrays with pyro-phototronic effects achieved detection beyond the band gap limit. Our results provide a new approach for bottom-up preparation of other crystalline allotropes of phosphorus.

Rust triggers rapid reduction of Cr6+ by red phosphorus: The importance of electronic transfer medium of Fe3

Red phosphorus (P) is one of the metalloid materials, with five external electrons, it should be an excellent electron donor. However, the activity of red P to reduce Cr⁶⁺ is limited. Due to electrostatic repulsion, it is difficult for the electrons on the red P to transfer to the chromate anion (Cr⁶⁺). Interestingly, we found that Fe³⁺ derived from rust, waste iron or Fe³⁺ reagents can be used as the electron transport medium to solve the electron transport obstacles between red P and Cr⁶⁺. As a result, the reduction of Cr⁶⁺ by red P/rust system takes only 20 min, which is far lower than the 140 min of red P. The reduction rate of Cr⁶⁺ in the red P/rust system is about 12.3 times that of red P. The reaction mechanism is that red P is not easy to access chromate anions but can easily adsorb Fe³⁺. The adsorbed Fe³⁺ will be reduced to Fe²⁺ by red P, and the regenerated Fe²⁺ will diffuse into the solution to rapidly reduce Cr⁶⁺. Therefore, this work provides an alternative waste iron reuse pathway and also sheds light on the important role of electron medium in reduction reaction.

Enhanced photocatalytic activity of 3D hierarchical RP/BP/BiOCOOH via oxygen vacancies and double heterojunctions

A 3D hierarchical RP/BP/BiOCOOH double heterostructures with abundant oxygen vacancies (OVs) was obtained by hydrothermal process and its photocatalytic activity was investigated by degradation of TC-HCl with different light sources and various natural water. The physicochemical characteristics of RP/BP/BiOCOOH heterojunctions were systematically characterized via TEM, XPS, EPR, EIS et al. Compared with BiOCOOH, the photocatalytic activity of RP/BP/BiOCOOH was obviously enhanced. Under simulated solar light irradiation, 60.5% of TC-HCl was removed by 3%RP/BP/BiOCOOH. And the rate constant of 3%RP/BP/BiOCOOH was 2.95 times than that of BiOCOOH. Traces of small molecular organics were beneficial to improve photocatalytic efficiency. The process of photocatalytic degradation and the cytotoxicity of intermedia products of TC-HCl were discussed via HPLC-MS, 3D-EEM, and antibacterial properties test. Based on the results of trapping experiments and ESR tests, •OH and •O₂^- were the most significant reactive oxygen species. The enhanced photocatalytic activity was ascribed to two reasons: 1 double heterojunctions structure enhanced the separation efficiency of carriers, 2 the introduction of OVs and BP/RP expanded the response range of light. This work provides a feasible strategy that non-metallic element semiconductor is used to modify the wide band gap semiconductor to enhance the photocatalytic efficiency.

Tumor Microenvironment Triggered the In Situ Synthesis of an Excellent Sonosensitizer in Tumor for Sonodynamic Therapy

An ultrasound-triggered sonodynamic therapy has shown great promise for cancer therapy. However, its clinical applications are very limited because the traditional sonosensitizers tend to suffer from very poor efficiency combined with low retention in cancer cells and low tumor selectivity. Therefore, sonosensitizers with higher effectivity, higher tumor cell retention, and higher tumor cell specificity are highly required. Herein, we constructed a Ti2C(OH)X nanosheet, which was a poor sonosensitizer but had a long circulation in the blood system. However, it was very interesting to find that the tumor microenvironment could in situ turn Ti2C(OH)X nanosheet into a novel and excellent sonosensitizer with a nanofiber structure in tumors, exhibiting excellent ability to generate reactive oxygen species (ROS) under ultrasound. Moreover, the nanofiber structure made it very difficult to get out of cancer cells, highly enhancing the retention of the sonosensitizer in the tumor, thereby enabling it to effectively and selectively kill cancer cells in vivo. Our findings demonstrate that the strategy of the tumor microenvironment triggering the in situ synthesis of an effective sonosensitizer in tumor provided a promising means to simultaneously increase the efficiency, sonosensitizer retention in cancer cells, and cancer selectivity, thereby effectively killing cancer cells but causing little damage to healthy tissues via the sonodynamic therapy.

Enhanced photocatalytic and antibacterial activities of S-scheme SnO2/Red phosphorus photocatalyst under visible light

The construction of wide bandgap semiconductors with heterojunctions is an effective strategy to improve the photocatalytic activity of narrow-bandgap semiconductors, such as red phosphorus (RP). The novel step-scheme (S-scheme) heterojunction can separate photocarriers effectively while retaining the high reduction-oxidation capacity of the catalyst. Herein, a SnO₂/hydrothermally treated RP (SnO₂/HRP) S-scheme heterojunction was constructed and was found to display superior performance in the photocatalytic degradation of pollutants and the disinfection of bacteria. The 5%SnO₂/HRP (mass ration of SnO₂ with 5 wt%) composite had the strongest photocatalytic activity. It could degrade 97.5% of Rhodamine B (RhB) after 12 min of light exposure. The photodegradation rate constant of this composite reached 2.96 × 10^-1 min^-1, which was 4.4 and 59.2 times higher than that of pure HRP and SnO₂, respectively. Furthermore, this S-scheme heterojunction composite exhibited a higher efficient photocatalytic antibacterial rate (99.4%) for Escherichia coli (E. coli) under visible-light irradiation, than pure HRP (66.4%) and SnO₂ (72.9%). Further mechanistic investigations illustrated that the intimate contact between HRP and SnO₂ in the S-scheme system heterojunction could effectively boost carrier transfer and improve the photocatalytic activity of the semiconductor. This investigation provided an efficient recyclable S-scheme heterojunction composite for the photocatalytic degradation of pollutants and bacteria.

Solution phase synthesis of the less-known Form II crystalline red phosphorus

Form II crystalline red phosphorus was grown by solvothermal reactions. XRD patterns match well with Roth’s results in 1947. Polyphosphide anions captured during phosphorus phase transformation support the “dissolution–crystallization” mechanism.

Red Phosphorus: An Up-and-Coming Photocatalyst on the Horizon for Sustainable Energy Development and Environmental Remediation

Photocatalysis is a perennial solution that promises to resolve deep-rooted challenges related to environmental pollution and energy deficit through harvesting the inexhaustible and renewable solar energy. To date, a cornucopia of photocatalytic materials has been investigated with the research wave presently steered by the development of novel, affordable, and effective metal-free semiconductors with fascinating physicochemical and semiconducting characteristics. Coincidentally, the recently emerged red phosphorus (RP) semiconductor finds itself fitting perfectly into this category ascribed to its earth abundant, low-cost, and metal-free nature. More notably, the renowned red allotrope of the phosphorus family is spectacularly bestowed with strengthened optical absorption features, propitious electronic band configuration, and ease of functionalization and modification as well as high stability. Comprehensively detailing RP's roles and implications in photocatalysis, this review article will first include information on different RP allotropes and their chemical structures, followed by the meticulous scrutiny of their physicochemical and semiconducting properties such as electronic band structure, optical absorption features, and charge carrier dynamics. Besides that, state-of-the-art synthesis strategies for developing various RP allotropes and RP-based photocatalytic systems will also be outlined. In addition, modification or functionalization of RP with other semiconductors for promoting effective photocatalytic applications will be discussed to assess its versatility and feasibility as a high-performing photocatalytic system. Lastly, the challenges facing RP photocatalysts and future research directions will be included to propel the feasible development of RP-based systems with considerably augmented photocatalytic efficiency. This review article aspires to facilitate the rational development of multifunctional RP-based photocatalytic systems by widening the cognizance of rational engineering as well as to fine-tune the electronic, optical, and charge carrier properties of RP.

Bi2O2CO3/red phosphorus S-scheme heterojunction for H2 evolution and Cr(VI) reduction

Red phosphorus (RP) has a suitable energy band structure and excellent photocatalytic properties. However, there are some problems, such as low quantum efficiency and serious photogenerated electron-hole recombination. The S-scheme heterostructure shows great potential in facilitating the separation and transfer of photogenerated carriers and obtaining strong photo-redox ability. Herein, hydrothermally treated red phosphorus (HRP) was combined with Bi₂O₂CO₃ to construct Bi₂O₂CO₃/HRP S-scheme heterojunction composite. The Bi₂O₂CO₃ content was optimized, and the 5 %Bi₂O₂CO₃/HRP composite obtained at 5 %Bi₂O₂CO₃ mass fraction exhibited the strongest photoreduction ability. The Cr(VI) photoreduction and photolytic hydrogen production rates were as high as 0.22 min^-1 and 157.2 μmol •h^-1, which were 7.3 and 3.0 times higher than those of HRP, respectively. The promoted photocatalytic activity could be attributed to the formation of S-scheme heterojunctions, which accelerated the separation and transfer of useful photogenerated electron-hole pairs, while enhancing the recombination of relatively useless photogenerated electron-hole pairs, thereby resulting in the highest photocurrent density (17.3 μA/cm²) of the 5 %Bi₂O₂CO₃/HRP composite, which was 1.6 and 4.3 times higher than pure Bi₂O₂CO₃ (10.5 μA/cm²) and pure HRP (4.0 μA/cm²), respectively. This work would provide an advanced approach to enhance the photocatalytic activity of RP.

Controllable preparation of crystalline red phosphorus and its photocatalytic properties

Single-element phosphorus has received extensive attention in recent years because of its remarkable photocatalytic properties. In the present experiment, amorphous red phosphorus was controllably transformed into [P12(4)]P2[and Hittorf's phosphorus structures by performing bismuth catalysis. The temperature-controllable chemical vapor transport reaction realized the conversion of more than 90% of amorphous red phosphorus to single-phase crystalline red phosphorus. Under very mild ultrasonic treatment, the high-quality [P12(4)]P2[microbelts and Hittorf's phosphorus microrods were stripped into a few layers of nanobelts and sheet-like structures, respectively. As non-metallic catalysts, their rapid photocatalytic degradations of pollutants (methyl orange) and high hydrogen evolution rates revealed the rapid charge transfer and application potential of the crystalline red phosphorus catalyst. The results of this work could provide new ideas for the development of phosphorus-based crystalline photocatalytic systems.

In situ constructed oxygen-vacancy-rich MoO3-x /porous g-C3N4 heterojunction for synergistically enhanced photocatalytic H2 evolution

A simple method was developed for enhanced synergistic photocatalytic hydrogen evolution by in situ constructing of oxygen-vacancy-rich MoO3-x /porous g-C3N4 heterojunctions. Introduction of a MoO3-x precursor (Mo(OH)6) solution into g-C3N4 nanosheets helped to form a porous structure, and nano-sized oxygen-vacancy-rich MoO3-x in situ grew and formed a heterojunction with g-C3N4, favorable for charge separation and photocatalytic hydrogen evolution (HER). Optimizing the content of the MoO3-x precursor in the composite leads to a maximum photocatalytic H2 evolution rate of 4694.3 μmol g-1 h-1, which is approximately 4 times higher of that of pure g-C3N4 (1220.1 μmol g-1 h-1). The presence of oxygen vacancies (OVs) could give rise to electron-rich metal sites. High porosity induced more active sites on the pores' edges. Both synergistically enhanced the photocatalytic HER performance. Our study not only presented a facile method to form nano-sized heterojunctions, but also to introduce more active sites by high porosity and efficient charge separation from OVs.

Photocatalytic degradation of ibuprofen on S-doped BiOBr

Doping heterogeneous atoms into BiOX is recognized as an effective method to improve its photocatalytic activity. Here, S-doped BiOBr (S-BiOBr) was synthesized via a solvothermal method in the absence of water, which is supposed to substitute O as S^2- in the lattice. This material is firstly used for the visible-light-driven degradation of ibuprofen, a model anti-inflammatory drug. The degradation efficiency of S-BiOBr is much higher than that of pure BiOBr. The degradation kinetic constant for S-BiOBr (2.48 × 10^-2 min^-1) is about 3 times as high as that of pure BiOBr (0.83 × 10^-2 min^-1). It is found that S-doping tunes the band structure of BiOBr, leading to a narrower band gap and thus higher utilization efficiency of visible light. The degradation of ibuprofen on S-BiOBr can be attributed to the generation of H₂O₂ and OH radicals. OH radical plays a synergistic role along with holes in the photocatalytic degradation process, which is supposed to be better than the reported single hole- or superoxide-dominant reaction. This work reveals a previously unrecognized and more efficient method for the degradation of organic contaminants on BiOBr.

Giant anisotropic photonics in the 1D van der Waals semiconductor fibrous red phosphorus

A confined electronic system can host a wide variety of fascinating electronic, magnetic, valleytronic and photonic phenomena due to its reduced symmetry and quantum confinement effect. For the recently emerging one-dimensional van der Waals (1D vdW) materials with electrons confined in 1D sub-units, an enormous variety of intriguing physical properties and functionalities can be expected. Here, we demonstrate the coexistence of giant linear/nonlinear optical anisotropy and high emission yield in fibrous red phosphorus (FRP), an exotic 1D vdW semiconductor with quasi-flat bands and a sizeable bandgap in the visible spectral range. The degree of photoluminescence (third-order nonlinear) anisotropy can reach 90% (86%), comparable to the best performance achieved so far. Meanwhile, the photoluminescence (third-harmonic generation) intensity in 1D vdW FRP is strong, with quantum efficiency (third-order susceptibility) four (three) times larger than that in the most well-known 2D vdW materials (e.g., MoS2). The concurrent realization of large linear/nonlinear optical anisotropy and emission intensity in 1D vdW FRP paves the way towards transforming the landscape of technological innovations in photonics and optoelectronics.

Enhanced Near-Infrared Photocatalytic Eradication of MRSA Biofilms and Osseointegration Using Oxide Perovskite-Based P-N Heterojunction

Methicillin-resistant Staphylococcus aureus (MRSA) biofilm infections after orthopedic implant increase the risk of failure and potentially cause amputation of limbs or life-threatening sepsis in severe cases. Additionally, satisfactory bone-implant integration is another important indicator of an ideal implant. Here, an antibiotic-free antibacterial nanofilm based on oxide perovskite-type calcium titanate (CTO)/fibrous red phosphorus (RP) on titanium implant surface (Ti-CTO/RP) in which the P-N heterojunction and internal electric field are established at the heterointerface, is designed. Near-infrared light-excited electron-hole pairs are effectively separated and transferred through the synergism of the internal electric field and band offset, which strongly boosts the photocatalytic eradication of MRSA biofilms by reactive oxygen species with an efficacy of 99.42% ± 0.22% in vivo. Additionally, the charge transfer endows the heterostructure with hyperthermia to assist biofilm eradication. Furthermore, CTO/RP nanofilm provides a superior biocompatible and osteoconductive platform that enables the proliferation and osteogenic differentiation of mesenchymal stem cells, thus contributing to the subsequent implant-to-bone osseointegration after eradicating MRSA biofilms.

Visible-light driven rapid bacterial inactivation on red phosphorus/titanium oxide nanofiber heterostructures

Photocatalytic water disinfection has emerged as a promising approach for water purification. However, exploring efficient and rapid visible light driven materials for photocatalytic bacterial inactivation is still a challenging problem. Herein, red phosphorus/titanium oxide (TiO₂@RP) nanofibers were developed for effective water disinfection by a vacuum ampoule strategy. The complete E. coli and S. aureus (7-log CFU mL^-1) could be rapidly killed within 25 min and 30 min over the optimized TiO₂@RP heterostructure under the white LED irradiation. The efficient photocatalytic antibacterial activity should be mainly ascribed to the synergetic enhancement in light absorption by RP decoration and charge migration and separation by the interface between TiO₂ and RP. And then more unpaired photo-carriers would be transferred to the surface to facilitate the generation of photo-holes, •O₂^- radicals, and H₂O₂ species, which could destroy the bacterial cells efficiently.

Elemental red phosphorus-based photocatalysts for environmental remediation: A review

The low-cost and environmentally benign elemental red phosphorus (RP) is a new class of photocatalysts with tunable bandgaps (ca. 1.5-2.4 eV) and has a strong visible-light response. It has been considered as a promising metal-free photocatalyst for solving the energy crisis and environmental problems. Unfortunately, due to the low-charge carrier mobility, and serve charge trapping effects, its photocatalytic activity is still restricted in comparison with the traditional compound photocatalysts. Considerable efforts, such as morphology modification, cocatalysts addition, heterostructure construction, charge trapping mitigation, have been conducted to improve the photocatalytic activity of the RP photocatalysts. In this review, the physical and chemical properties and the synthetic strategies of the RP photocatalysts were summarized along with the application in environmental remediation accompanied by the photocatalytic reaction mechanism. Finally, an overview and outlook on the problems and future avenues in designing and constructing advanced RP photocatalysts were also proposed.

Red Phosphorus Decorated TiO2 Nanorod Mediated Photodynamic and Photothermal Therapy for Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC) is a serious and tenacious disease. Photodynamic therapy (PDT) and photothermal therapy (PTT) are effective means of cancer treatment. However, PDT combined with PTT has been rarely reported in ccRCC treatment. In the present study, by developing the core-shell structured TiO₂ @red phosphorus nanorods (TiO₂ @RP NRs) as a photosensitizer, the feasibility and effectiveness of synchronous PDT and PTT treatments for ccRCC are demonstrated. The core-shell structured TiO₂ @RP NRs are synthesized to drive the PDT and PTT for ccRCC, in which the RP shell is the sensitizer even in the near-infrared (NIR) region. The optimized TiO₂ @RP NRs can respond to NIR and produce local heat under irradiation. The NRs are estimated in ccRCC treatments via cell counting kit-8 assay, propidium iodide staining, qRT-PCR, and reactive oxygen species (ROS) probes in vitro, while terminal deoxynucleotidyl transferase dUTP nick-end labeling is conducted in vivo. After NIR irradiation, TiO₂ @RP NRs can efficiently kill ccRCC cells by producing local heat and ROS and cause low injury to normal kidney cells. Furthermore, treatment with TiO₂ @RP NRs and NIR can kill significant numbers of deep-tissue ccRCC cells in vivo. This work highlights a promising photo-driven therapy for kidney cancer.

Fibrous Phase Red Phosphorene as a New Photocatalyst for Carbon Dioxide Reduction and Hydrogen Evolution

2D photocatalysts are one of the hottest issues in energy and material science. In the field of photocatalysis, a 2D material with an appropriate bandgap of 1.3 to 2.0 eV is desirable. Herein, a new kind of fibrous phase red phosphorene with a bandgap between 1.43 to 1.54 eV is obtained. This is much better than black phosphorus because the bandgap of black P depends of its layer number. The black P needs to be as thin as 1-2 layers for suitable band diagram, which is difficult to control. The fibrous red phosphorene is first used for photocatalytic CO₂ reduction, and its activity is superior to the majority of mainstream photocatalysts and reaches a record-high value among phosphorus. Besides, its activity in hydrogen evolution is higher than most of the phosphorus photocatalysts. The intralayer charge transfer is much easier than interlayer transfer. The mobility of electron and hole along the phosphorene plane is about 20 times higher than that perpendicular to different layers. The activity sites is at region between the two P[21] chains. These regions are easy to be exposed for fibrous phase phosphorene, making it to exhibit high activity.

Bifunctional black phosphorus: coupling with hematite for Z-scheme photocatalytic overall water splitting

Z-scheme 2D–2D BP/α-Fe₂O₃ heterostructure enables preferable photocatalytic properties for efficient overall water splitting under visible light.

In situ growth of metal-free snowflake-like 1D/2D phosphorus element heterostructures for photocatalytic overall pure-water splitting

In this work, we report a novel phosphorus element heterostructure with a snowflake-like morphology consisting of 1D rod-like black phosphorus (BP) and 2D flake-like red phosphorus (RP).

Visible-light photocatalytic activity enhancement of red phosphorus dispersed on the exfoliated kaolin for pollutant degradation and hydrogen evolution

The semiconductor photocatalyst is crucial for dealing with the current environmental and energy crises. However, the large-scale applications of the reported semiconductor materials are hampered by the recombination of electrons and holes, low kinetic properties, and slow reaction rates. Herein, a three-dimensional structured kaolin/hydrothermally treated red phosphorus (K/HRP) composite photocatalyst was synthesized. The composition ratio was optimized, and the K₇/HRP composites (contained 7%) exhibited the highest photocatalytic activity. The rhodamine B photodegradation rate constant and the hydrogen production rate were 0.25 min^-1 and 252 μmol h^-1 g^-1, which were higher than those of HRP by 12.4 and 7.2 times, respectively. The enhancement of the HRP photocatalytic activity was attributed to the presence of K, which inhibited the overgrowth and the agglomeration of HRP and shortened the carrier migration distance. The electrostatic interaction between the K and the HRP effectively promoted the separation of photogenerated charge carriers. In addition, the three-dimensional structure of the K and the HRP construct enhanced the light absorption and provided a pollution-free and large-area transport interface for carriers. This work has paramount guiding importance in the preparation of high-efficiency, cheap, and recyclable nanocomposite photocatalyst materials.

What's the gap? A possible strategy for advancing theory, and an appeal for experimental structure data to drive that advance

There is substantial demand for theoretical/computational tools that can produce correct predictions of the geometric structure and band gap to accelerate the design and screening of new materials with desirable electronic properties. DFT-based methods exist that reliably predict electronic structure given the correct geometry. Similarly, when good spectroscopic data are available, these same methods may, in principle, be used as input to the inverse problem of generating a good structural model. The same is generally true for gas-phase systems, for which the choice of method is different, but factors that guide its selection are known. Despite these successes, there are shortcomings associated with DFT for the prediction of materials' electronic structure. The present paper offers a perspective on these shortcomings. Fundamentally, the shortcomings associated with DFT stem from a lack of knowledge of the exact functional form of the exchange–correlation functional. Inaccuracies therefore arise from using an approximate functional. These inaccuracies can be reduced by judicious selection of the approximate functional. Other apparent shortcomings present due to misuse or improper application of the method. One of the most significant difficulties is the lack of a robust method for predicting electronic and geometric structure when only qualitative (connectivity) information is available about the system/material. Herein, some actual shortcomings of DFT are distinguished from merely common improper applications of the method. The role of the exchange functional in the predicted relationship between geometric structure and band gap is then explored, using fullerene, 2D polymorphs of elemental phosphorus and polyacetylene as case studies. The results suggest a potentially fruitful avenue of investigation by which some of the true shortcomings might be overcome, and serve as the basis for an appeal for high-accuracy experimental structure data to drive advances in theory.

Strong correlation between electronic structure and geometry might be capitalized upon to tune the DFT functional.

NIR light-assisted phototherapies for bone-related diseases and bone tissue regeneration: A systematic review

Recently, the rapid development of biomaterials has induced great interest in the precisely targeted treatment of bone-related diseases, including bone cancers, infections, and inflammation. Realizing noninvasive therapeutic effects, as well as improving bone tissue regeneration, is essential for the success of bone‑related disease therapies. In recent years, researchers have focused on the development of stimuli-responsive strategies to treat bone-related diseases and to realize bone regeneration. Among the various external stimuli for targeted therapy, near infrared (NIR) light has attracted considerable interests due to its high tissue penetration capacity, minimal damage toward normal tissues, and easy remote control properties. The main objective of this systematic review was to reveal the current applications of NIR light-assisted phototherapy for bone-related disease treatment and bone tissue regeneration. Database collection was completed by June 1, 2020, and a total of 81 relevant studies were finally included. We outlined the various therapeutic applications of photothermal, photodynamic and photobiomodulation effects under NIR light irradiation for bone‑related disease treatment and bone regeneration, based on the retrieved literatures. In addition, the advantages and promising applications of NIR light-responsive drug delivery systems for spatiotemporal-controlled therapy were summarized. These findings have revealed that NIR light-assisted phototherapy plays an important role in bone-related disease treatment and bone tissue regeneration, with significant promise for further biomedical and clinical applications.

Elemental red phosphorus-based materials for photocatalytic water purification and hydrogen production

Semiconductor-based photocatalysis is a renewable and sustainable technology to solve global environmental pollution and energy shortage problems. It is essential to exploit highly efficient photocatalyst materials. Recently, Earth-abundant elemental red phosphorus (RP) with broader light-harvesting and appropriate band structure characteristics has been widely studied in photocatalysis. In this review, the crystal and electronic structures of RP (e.g., amorphous, Hittorf's and fibrous phosphorus) materials are firstly summarized along with the current advancement in the synthesis strategies of RP and RP-based materials in photocatalysis accompanied by a thorough discussion of the applications of RP-based materials in photocatalytic pollutant degradation, bacterial inactivation, and water splitting. Finally, this review also offers some guidance and perspectives for the future design of efficient visible-light-driven photocatalysts.

Polymer Nanofibers Exhibiting Remarkable Activity in Driving the Living Polymerization under Visible Light and Reusability

Visible light-driving syntheses have emerged as a powerful tool for organic synthesis and for the preparation of macromolecules under mild and environmentally benign conditions. However, precious but nonreusable photosensitizers or photocatalysts are often required to activate the reaction, limiting its practicality. Here, it is reported that poly(1,4-diphenylbutadiyne) (PDPB) nanofibers exhibit remarkable activity in driving the living free radical polymerization under visible light. Moreover, PDPB nanofibers are very stable under irradiation of visible light and can be reused without appreciable loss of activity even after repeated cycling. The nanofiber will be a promising photocatalyst with excellent reusability and stability for the reactions driven by visible light.

Band-Gap and Charge Transfer Engineering in Red Phosphorus-Based Composites for Enhanced Visible-Light-Driven H2 Evolution

It is known that the low lifetime of photogenerated carriers is the main drawback of elemental photocatalysts. Therefore, a facile and versatile one-step strategy to simultaneously achieve the oxygen covalent functionalization of amorphous red phosphorus (RP) and in situ modification of CdCO₃ is reported. This strategy endows RP with enhanced charge carrier separation ability and photocatalytic activity by coupling band-gap engineering and heterojunction construction. The as-prepared nCdCO₃ /SO-RP (n=0.1, 0.25, 0.5, 1.0) composites exhibited excellent photocatalytic H₂ evolution activity (up to 516.3 μmol g^-1  h) from visible-light-driven water splitting (λ>400 nm), which is about 17.6 times higher than that of pristine RP. By experimental and theoretical investigations, the roles of surface oxygen covalent functionalization, that is, prolonging the lifetime of photogenerated carriers and inducing the negative shift of the conduction band potential, were studied in detail. Moreover, the charge transfer mechanism of these composites has also been proposed. In addition, these composites are stable and can be reused at least for three times without significant activity loss. This work may provide a good example of how to promote the activity of elemental photocatalysts by decorating their atomic structure.

An overview of the optical properties and applications of black phosphorus

Since the year 2014, when scientists first obtained black phosphorus using a sticky tape to peel the layers off, it has attracted tremendous interest as a novel two-dimensional material. After it was successfully produced, its outstanding optical properties have been unveiled. Various applications based on these properties have been reported. This study mainly reviews the unique optical properties and potential applications of black phosphorus. The optical performances of black phosphorus mainly include linear optical properties and nonlinear optical properties. Some examples include the anisotropic optical response, saturable absorption effect and Kerr effect. The researchers found that the nonlinear saturable absorption coefficients of black phosphorus are better than that of MoS₂ and WS₂ from the visible region to the near-infrared region. Compared with graphene, black phosphorus has a better nonlinear saturable absorption performance. After passivation or surface modification, black phosphorus is stable when exposed to oxygen and water. Herein, black phosphorus has the potential to be used in detector/sensors, solar energy harvesting, photocatalysts, optical saturable absorbers in ultrafast lasers, all optical switches, optical modulation, nanomedicine and some others in the near future.

Black Phosphorus-Based Semiconductor Heterojunctions for Photocatalytic Water Splitting

Solar-to-hydrogen (H₂ ) conversion has been regarded as a sustainable and renewable technique to address aggravated environmental pollution and global energy crisis. The most critical aspect in this technology is to develop highly efficient and stable photocatalysts, especially metal-free photocatalysts. Recently, black phosphorus (BP), as a rising star 2D nanomaterial, has captured enormous attention in photocatalytic water splitting owing to its widespread optical absorption, adjustable direct band gap, and superior carrier migration characteristics. However, the rapid charge recombination of pristine BP has seriously limited its practical application as photocatalyst. The construction of BP-based semiconductor heterojunctions has been proven to be an effective strategy for enhancing the separation of photogenerated carriers. This Minireview attempts to summarize the recent progress in BP-based semiconductor heterojunctions for photocatalytic water splitting, including type-I and type-II heterojunctions, Z-Scheme systems, and multicomponent heterojunctions. Finally, a brief summary and perspective on the challenges and future directions in this field are also provided.

Metal-free photocatalysts for hydrogen evolution

This article provides a comprehensive review of the latest progress, challenges and recommended future research related to metal-free photocatalysts for hydrogen productionviawater-splitting.

Efficient solar-driven nitrogen fixation over an elemental phosphorus photocatalyst

An elemental semiconductor (red phosphorus) based photocatalyst was developed for nitrogen fixation under full-spectrum irradiation without using any hole scavenger.

Tailoring of crystalline structure of carbon nitride for superior photocatalytic hydrogen evolution

Light absorption and carrier transfer, are two sequential and complementary steps related to photocatalysis performance, whereas the collective integration of these two aspects into graphitic carbon nitride (g-C₃N₄) photocatalyst through polycondensation optimization have seldom been achieved. Herein, we report on tailoring the crystalline structure of g-C₃N₄ by avoiding the formation of incompletely reacted N-rich intermediates and selective breaking the hydrogen bonds between the layers of g-C₃N₄ simultaneously. The obtained layer plane ordered porous carbon nitride (LOP-CN) material shows efficient photocatalytic H₂ generation performance. The highest H₂ evolution rate achieved is 53.8 μmol under λ ≥ 400 nm light irradiation, which is 7.4 times higher than that of g-C₃N₄ prepared by convention thermal polycondensation. The substantially boosted photocatalytic activity is mainly ascribed to the efficient charge separation on long-range atomic order layer plane and the extended visible light harvesting ability. This work highlights the importance of crystalline structure tailoring in improving charge separation and light absorption of g-C₃N₄ photocatalyst for boosting its photocatalytic H₂ evolution activity.

Atomically Dispersed Single Co Sites in Zeolitic Imidazole Frameworks Promoting High-Efficiency Visible-Light-Driven Hydrogen Production

As photocatalysis technology could transform renewable and clean solar energy into green hydrogen (H₂ ) energy through solar water splitting, it is regarded as the "Holy Grail" in chemistry field in the 21st century. Unfortunately, the bottleneck of this technique still lies in the exploration of highly active, cost-effective, and robust photocatalysts. This work reports the design and synthesis of a novel zeolitic imidazole framework (ZIF) coupled Zn_0.8 Cd_0.2 S hetero-structured photocatalyst for high-performance visible-light-induced H₂ production. State-of-the-art characterizations and theoretical computations disclose that the interfacial electronic interaction between ZIF and Zn_0.8 Cd_0.2 S, the high distribution of Zn_0.8 Cd_0.2 S on ZIF, and the atomically dispersed coordinately unsaturated Co sites in ZIF synergistically arouse the significantly improved visible-light photocatalytic H₂ production performance.