Metal Phosphorous Trichalcogenides (MPCh3 ): From Synthesis to Contemporary Energy Challenges

Advanced materials for micro/nanorobotics

Autonomous micro/nanorobots capable of performing programmed missions are at the forefront of next-generation micromachinery. These small robotic systems are predominantly constructed using functional components sourced from micro- and nanoscale materials; therefore, combining them with various advanced materials represents a pivotal direction toward achieving a higher level of intelligence and multifunctionality. This review provides a comprehensive overview of advanced materials for innovative micro/nanorobotics, focusing on the five families of materials that have witnessed the most rapid advancements over the last decade: two-dimensional materials, metal-organic frameworks, semiconductors, polymers, and biological cells. Their unique physicochemical, mechanical, optical, and biological properties have been integrated into micro/nanorobots to achieve greater maneuverability, programmability, intelligence, and multifunctionality in collective behaviors. The design and fabrication methods for hybrid robotic systems are discussed based on the material categories. In addition, their promising potential for powering motion and/or (multi-)functionality is described and the fundamental principles underlying them are explained. Finally, their extensive use in a variety of applications, including environmental remediation, (bio)sensing, therapeutics, etc., and remaining challenges and perspectives for future research are discussed.

Synthesis of Graphitic Carbon Coated ZnPS3 and its Superior Electrochemical Properties for Lithium and Sodium Ion Storage

Graphitic carbon-coated ZnPS3 is prepared via direct phosphosulfurization and high energy mechanical milling (HEMM) with multiwall carbon nanotubes (MWCNTs) and first introduced as an anode for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The HEMM process with MWCNTs reduces the particle size of as-synthesized ZnPS3 bulk to 100-500 nm and yields the ≈5 nm thick graphitic carbon coated ZnPS3 nanoparticles, which are the nanocomposites of 5 nm sized nanocrystallites embedded in the amorphous matrix. The ZnPS3 electrode undergoes the combined conversion and alloying reactions with Li and Na ions and exhibits high initial discharge and charge capacities in both LIBs and SIBs. The graphitic carbon-coated ZnPS3 electrode exhibits excellent high-rate capability and long-term cyclability. The superior electrochemical properties can be attributed to high electrical conductivity, high Li ion mobility, and high reversibility and structural stability derived from the graphitic carbon-coated nanoparticles. This study demonstrates that the novel graphitic carbon-coated ZnPS3 is a promising anode material for both LIBs and SIBs and the graphitic carbon coating methodology by HEMM is expected to apply to the various metal oxides, sulfides, and phosphides.

Electronic Correlations in FexNiyPS3 Van der Waals Materials: Insights from Angle-Resolved Photoelectron Spectroscopy and DFT

Recently layered antiferromagnetic materials with different magnetic orderings attract increased attention. It was found that these properties can be preserved down to the monolayer limit opening large perspectives for their applications in (opto)spintronics and sensing, however, lacking the experimental results on electronic structure studies. Here the results of angle-resolved photoelectron spectroscopy (ARPES) studies accompanied by DFT calculations for FexNiyPS3 layered van der Waals (vdW) alloys are presented, addressing the effects of electronic correlations in these materials. It is demonstrated that in the case of FePS3 the top of the valence band is formed by the hybrid Fe 3d-S 3p states and is of pure S 3p character for NiPS3, respectively, whereas for the mixed Fe-Ni-based vdW alloy the electronic structure is a sum of contributions from the parent compounds. The obtained results give a clear understanding of the nature of the insulating state in studied MPX3 materials and pave the way on their applications in different areas.

Sonication-assisted liquid phase exfoliation of two-dimensional CrTe3 under inert conditions

Liquid phase exfoliation (LPE) has been used for the successful fabrication of nanosheets from a large number of van der Waals materials. While this allows to study fundamental changes of material properties' associated with reduced dimensions, it also changes the chemistry of many materials due to a significant increase of the effective surface area, often accompanied with enhanced reactivity and accelerated oxidation. To prevent material decomposition, LPE and processing in inert atmosphere have been developed, which enables the preparation of pristine nanomaterials, and to systematically study compositional changes over time for different storage conditions. Here, we demonstrate the inert exfoliation of the oxidation-sensitive van der Waals crystal, CrTe3. The pristine nanomaterial was purified and size-selected by centrifugation, nanosheet dimensions in the fractions quantified by atomic force microscopy and studied by Raman, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and photo spectroscopic measurements. We find a dependence of the relative intensities of the CrTe3 Raman modes on the propagation direction of the incident light, which prevents a correlation of the Raman spectral profile to the nanosheet dimensions. XPS and EDX reveal that the contribution of surface oxides to the spectra is reduced after exfoliation compared to the bulk material. Further, the decomposition mechanism of the nanosheets was studied by time-dependent extinction measurements after water titration experiments to initially dry solvents, which suggest that water plays a significant role in the material decomposition.

Composition and phase engineering of metal chalcogenides and phosphorous chalcogenides

Two-dimensional (2D) materials with multiphase, multielement crystals such as transition metal chalcogenides (TMCs) (based on V, Cr, Mn, Fe, Cd, Pt and Pd) and transition metal phosphorous chalcogenides (TMPCs) offer a unique platform to explore novel physical phenomena. However, the synthesis of a single-phase/single-composition crystal of these 2D materials via chemical vapour deposition is still challenging. Here we unravel a competitive-chemical-reaction-based growth mechanism to manipulate the nucleation and growth rate. Based on the growth mechanism, 67 types of TMCs and TMPCs with a defined phase, controllable structure and tunable component can be realized. The ferromagnetism and superconductivity in FeX_y can be tuned by the y value, such as superconductivity observed in FeX and ferromagnetism in FeS₂ monolayers, demonstrating the high quality of as-grown 2D materials. This work paves the way for the multidisciplinary exploration of 2D TMPCs and TMCs with unique properties.

Expediting Oxygen Evolution by Optimizing Cation and Anion Complexity in Electrocatalysts Based on Metal Phosphorous Trichalcogenides

Purposely changing the rate-determining step (RDS) of oxygen evolution reaction (OER) remains a major challenge for enhancing the energy efficiency of electrochemical splitting of water. Here we show that the OER RDS can be regulated by simply varying the cation and anion complexity in a family of the metal phosphorous trichalcogenide electrocatalysts (MPT₃ , where M=Fe, Ni; T=S, Se), achieving an exceptionally high OER activity in (Ni,Fe)P(S,Se)₃ , as demonstrated by its ultra-low Tafel slope (34 mV dec^-1 ) and a very low overpotential compared to many relevant OER catalysts. This is strongly supported by density functional theory calculations, which showed that this catalyst has a nearly optimal OER activity descriptor value of ΔG(O*)-ΔG(OH*)=1.5 eV. We also found that the activity descriptor is proportional to a newly proposed cation/anion complexity index that consists of pairwise contributions from cation-anion bonds in a catalyst compound, revealing the pivotal role of the cation-anion interactions in determining the catalyst performance and providing a simple way for predicting catalytic activities.

Exfoliated 2D Layered and Nonlayered Metal Phosphorous Trichalcogenides Nanosheets as Promising Electrocatalysts for CO2 Reduction

Two-dimensional (2D) materials catalysts provide an atomic-scale view on a fascinating arena for understanding the mechanism of electrocatalytic carbon dioxide reduction (CO₂ ECR). Here, we successfully exfoliated both layered and nonlayered ultra-thin metal phosphorous trichalcogenides (MPCh₃ ) nanosheets via wet grinding exfoliation (WGE), and systematically investigated the mechanism of MPCh₃ as catalysts for CO₂ ECR. Unlike the layered CoPS₃ and NiPS₃ nanosheets, the active Sn atoms tend to be exposed on the surfaces of nonlayered SnPS₃ nanosheets. Correspondingly, the nonlayered SnPS₃ nanosheets exhibit clearly improved catalytic activity, showing formic acid selectivity up to 31.6 % with -7.51 mA cm^-2 at -0.65 V vs. RHE. The enhanced catalytic performance can be attributed to the formation of HCOO* via the first proton-electron pair addition on the SnPS₃ surface. These results provide a new avenue to understand the novel CO₂ ECR mechanism of Sn-based and MPCh₃ -based catalysts.

2D Functionalized Germananes: Synthesis and Applications

In the realm of 2D layered materials, the monoelemental group 14 Xene, germanene, as the germanium analog of graphene, has emerged as the next prospective candidate. Preceded by silicon, germanium is widely used in the semiconductor industry; thus, germanene is deemed compatible with existing semiconductor technologies. Germanene consists of mixed sp² -sp³ -hybridized networks in a buckled hexagonal honeycomb structure. Chemical exfoliation of Zintl phases, such as CaGe₂ , specifically the topotactical deintercalation in acidic media, removes the alkaline earth metal ions Ca²⁺ , giving rise to layered germanane (germanene with the Ge centers covalently saturated with terminal hydrogen atoms). Diverse variants of functionalized germananes (with covalent group(s) termination) can be obtained by varying the topotactical deintercalation precursors, elevating the game with limitless functionalization possibilities for customizable properties or new functionalities. The preparation of Zintl phases to the details of functionalized and modified germananes and their properties, and the additional exfoliation step to achieve mono- or few-layer germananes, are comprehensively covered. The progress and challenges of 2D functionalized germananes in optoelectronics, catalysis, energy conversion and storage, sensors, and biomedical areas are reviewed. This review provides insight into designing and exploring this class of atomically thin semiconductors in realizing future nanoarchitectonics.

Two-Dimensional Iron Phosphorus Trisulfide as a High-Capacity Cathode for Lithium Primary Battery

Metal phosphorus trichalcogenide (MPX₃) materials have aroused substantial curiosity in the evolution of electrochemical storage devices due to their environment-friendliness and advantageous X-P synergic effects. The interesting intercalation properties generated due to the presence of wide van der Waals gaps along with high theoretical specific capacity pose MPX₃ as a potential host electrode in lithium batteries. Herein, we synthesized two-dimensional iron thio-phosphate (FePS₃) nanoflakes via a salt-template synthesis method, using low-temperature time synthesis conditions in single step. The electrochemical application of FePS₃ has been explored through the construction of a high-capacity lithium primary battery (LPB) coin cell with FePS₃ nanoflakes as the cathode. The galvanostatic discharge studies on the assembled LPB exhibit a high specific capacity of ~1791 mAh g^-1 and high energy density of ~2500 Wh Kg^-1 along with a power density of ~5226 W Kg^-1, some of the highest reported values, indicating FePS₃'s potential in low-cost primary batteries. A mechanistic insight into the observed three-staged discharge mechanism of the FePS₃-based primary cell resulting in the high capacity is provided, and the findings are supported via post-mortem analyses at the electrode scale, using both electrochemical- as well as photoelectron spectroscopy-based studies.

A novel exfoliated manganese phosphoselenide as a high-performance anode material for lithium ions storage

Layered manganese phosphoselenide (MnPSe3) is expected to be a potential anode for Li ions storage due to it combines the merits of phosphorus with metal selenide. It promotes charge transfer and ensures a high theoretical capacity of up to 746 mA h g−1. In this work, a comprehensive study clearly demonstrated that bulk MnPSe3 electrode is the inability to maintain the integrity of the structure with severe detectable fracture or pulverization after full lithiation/delithiation, resulting in poor rate capability and cycling stability. Additionally, exfoliated few-layered MnPSe3 nanoflakes by the ultrasonic method show enhanced electrical conductivity and resistance to volume expansion. It has a high initial discharge/charge capacity reaching to 524/796 mA h g−1 and outstanding cycling stability with charge capacities of 709 mA h g−1 after 100 cycles at 0.2 A g−1 within the potential window of 0.005–3 V vs. Li+/Li. While further improving the cycles, the retention rate was still held at ∼72% after 350 cycles. This work provides new insights into exploiting new novel layered materials, such as MnPSe3 as anodes for lithium-ion batteries.

Realizing the high energy density and flexibility of a fabric electrode through hierarchical structure design

The exploration of high-energy density flexible electrodes through reasonable structural design is the key to realizing the overall portability and wearability of devices. Herein, a free-standing hybrid nanofabric with superior mechanical and electrochemical stabilities is reported for flexible lithium-ion batteries (LIBs). The hybrid nanofabric is prepared by electrospinning and carbonization, during which the self-cyclization of polyacrylonitrile (PAN) is hindered by its reaction with melamine, resulting in a highly disordered and expanded turbostratic carbon structure with nickel metal thiophosphate (NiPS₃) nanosheets embedded in it. The coordinated movement of the electrospun-derived 1D nanofiber, the super toughness of the hard carbon structure and the interlayer slipping of NiPS₃ endow the hybrid nanofabric with excellent tolerance to large-scale deformation. It can be folded three times in half and quickly return to its original state. When used as the anode for LIBs, no additional binder, conducting agent and current collector are needed. The free-standing anode not only shows excellent cycling (797.5 mA h g^-1 after 1000 cycles at 1 A g^-1) and rate (more than 56% capacity retained from 0.1 to 2 A g^-1) performances, but also maintains its original electrochemical properties after being folded 300 times at 120°, 180° and 360°. This work provides a synergistic strategy to simultaneously enhance the energy density and flexibility of a fabric electrode, paving the way for the application of advanced flexible energy storage systems.

Achieving Ultrahigh-Rate and Low-Temperature Sodium Storage of FePS3 via In Situ Construction of Graphitized Porous N-Doped Carbon

Sodium-ion batteries (SIBs) have become an important supplementation to lithium-ion batteries. Unfortunately, the low capacity and inferior low-temperature performance of traditional hard carbon led to limited energy density and a range of applications of SIBs. Herein, we present high-performance SIBs via embedding FePS₃ in graphitized porous N-doped carbon (FPS/GPNC) using coordination polymerization reaction. Such unique graphitized pores are in situ-constructed by the self-aggregation of Fe nanoparticles with high surface energy at high temperatures, which affords a three-dimensional open channel and a graphitized conductive network for fast transportation of Na⁺ and electrons. Moreover, an ingenious buffer barrier composed of graphitized pores is constructed for FePS₃ to withstand volume fluctuation during cycling. Consequently, a superior capacity of 354.2 mAh g^-1 is delivered even when the rate increases to 50 A g^-1. The impressing cycling lifespan up to 4700 cycles is achieved at 30 A g^-1 with excellent retention of 84.4%. Interestingly, the low-temperature performance (-20 °C) of FePS₃ is explored for the first time, and excellent stability (502.6 mAh g^-1 maintained after 100 cycles at 0.1 A g^-1) is obtained, indicating huge potential of practical application. This work provides insights into designing high-rate, high-capacity, and low-temperature SIBs.

Engineering van der Waals Materials for Advanced Metaphotonics

The outstanding chemical and physical properties of 2D materials, together with their atomically thin nature, make them ideal candidates for metaphotonic device integration and construction, which requires deep subwavelength light-matter interaction to achieve optical functionalities beyond conventional optical phenomena observed in naturally available materials. In addition to their intrinsic properties, the possibility to further manipulate the properties of 2D materials via chemical or physical engineering dramatically enhances their capability, evoking new science on light-matter interaction, leading to leaped performance of existing functional devices and giving birth to new metaphotonic devices that were unattainable previously. Comprehensive understanding of the intrinsic properties of 2D materials, approaches and capabilities for chemical and physical engineering methods, the resulting property modifications and novel functionalities, and applications of metaphotonic devices are provided in this review. Through reviewing the detailed progress in each aspect and the state-of-the-art achievement, insightful analyses of the outstanding challenges and future directions are elucidated in this cross-disciplinary comprehensive review with the aim to provide an overall development picture in the field of 2D material metaphotonics and promote rapid progress in this fast emerging and prosperous field.

Synthesis of Magnesium Phosphorous Trichalcogenides and Applications in Photoelectrochemical Water Splitting

Promising applications of metal phosphorous trichalcogenides (M₂ P₂ X₆ or MPX₃ ) have been predicted in optoelectronics, photoelectrocatalysis, and water-splitting reactions, mainly due to its wide bandgap. Transition metals are widely used in the synthesis of MPX₃ , however, divalent cations of alkaline earth metals can also be constituents in MPX₃ 2D layered structures. Herein, MgPX₃ (X = S, Se) are synthesized and their photoelectrochemical (PEC) activity is tested in the hydrogen evolution and oxygen evolution reaction (OER) regions under a wide range of wavelengths. MgPSe₃ photoelectrode shows the best PEC performance with a response of 1.6 ± 0.1 mA cm^-2 under 420 nm. In the light-assisted OER, a 200 mV improvement is obtained in the overpotential at 10 mA cm^-2 for MgPSe₃ . The better performance of MgPSe₃ is consistent with its lower optical bandgap (E_g  = 3.15 eV), as a result of the variation of electronegativity between selenide and sulfide.

Biomedical engineering of two-dimensional MXenes

The emergence of two-dimensional (2D) transition metal carbides, carbonitrides and nitrides, referred to MXenes, with a general chemical formula of M_n+1X_nT_x have aroused considerable interest and shown remarkable potential applications in diverse fields. The unique ultrathin lamellar structure accompanied with charming electronic, optical, magnetic, mechanical and biological properties make MXenes as a kind of promising alternative biomaterials for versatile biomedical applications, as well as uncovering many new fundamental scientific discoveries. Herein, the current state-of-the-art advances of MXenes-related biomaterials are systematically summarized in this comprehensive review, especially focusing on the synthetic methodologies, design and surface engineering strategies, unique properties, biological effects, and particularly the property-activity-effect relationship of MXenes at the nano-bio interface. Furthermore, the elaborated MXenes for varied biomedical applications, such as biosensors and biodevices, antibacteria, bioimaging, therapeutics, theranostics, tissue engineering and regenerative medicine, are illustrated in detail. Finally, we discuss the current challenges and opportunities for future advancement of MXene-based biomaterials in-depth on the basis of the present situation, aiming to facilitate their early realization of practical biomedical applications.

Two-Dimensional High-Entropy Metal Phosphorus Trichalcogenides for Enhanced Hydrogen Evolution Reaction

Developing earth-abundant and highly effective electrocatalysts for hydrogen evolution reaction (HER) is a prerequisite for the upcoming hydrogen energy society. Two-dimensional (2D) high-entropy metal phosphorus trichalcogenides (MPCh₃) have the advantages of both near-continuous adsorption energies of high-entropy alloys (HEAs) and large specific surface area of 2D materials, which are excellent catalytic platforms. As a typical 2D high-entropy catalyst, Co_0.6(VMnNiZn)_0.4PS₃ nanosheets with high-concentration active sites are successfully demonstrated to show enhanced HER performance: an overpotential of 65.9 mV at a current density of 10 mA cm^-2 and a Tafel slope of 65.5 mV dec^-1. Decent spectroscopy characterizations are combined with density function theory analyses to show the scenario for the enhancement mechanism by a high-entropy strategy. The optimized S sites on the edge and P sites on the basal plane provide more active sites for hydrogen adsorption, and the introduced Mn sites boost water dissociation during the Volmer step. Two-dimensional high-entropy MPCh₃ provides an avenue for the combination of HEAs and 2D materials to enhance the HER performance, which also provides an alternative materials platform to explore and design superior catalysts for various electrochemical systems.

Shining Light on Anion-Mixed Nanocatalysts for Efficient Water Electrolysis: Fundamentals, Progress, and Perspectives

This review introduces recent advances of various anion-mixed transition metal compounds (e.g., nitrides, halides, phosphides, chalcogenides, (oxy)hydroxides, and borides) for efficient water electrolysis applications in detail. The challenges and future perspectives are proposed and analyzed for the anion-mixed water dissociation catalysts, including polyanion-mixed and metal-free catalyst, progressive synthesis strategies, advanced in situ characterizations, and atomic level structure-activity relationship. Hydrogen with high energy density and zero carbon emission is widely acknowledged as the most promising candidate toward world's carbon neutrality and future sustainable eco-society. Water-splitting is a constructive technology for unpolluted and high-purity H₂ production, and a series of non-precious electrocatalysts have been developed over the past decade. To further improve the catalytic activities, metal doping is always adopted to modulate the 3d-electronic configuration and electron-donating/accepting (e-DA) properties, while for anion doping, the electronegativity variations among different non-metal elements would also bring some potential in the modulations of e-DA and metal valence for tuning the performances. In this review, we summarize the recent developments of the many different anion-mixed transition metal compounds (e.g., nitrides, halides, phosphides, chalcogenides, oxyhydroxides, and borides/borates) for efficient water electrolysis applications. First, we have introduced the general information of water-splitting and the description of anion-mixed electrocatalysts and highlighted their complementary functions of mixed anions. Furthermore, some latest advances of anion-mixed compounds are also categorized for hydrogen and oxygen evolution electrocatalysis. The rationales behind their enhanced electrochemical performances are discussed. Last but not least, the challenges and future perspectives are briefly proposed for the anion-mixed water dissociation catalysts.

Telemedicine platform for health assessment remotely by an integrated nanoarchitectonics FePS3/rGO and Ti3C2-based wearable device

Due to the emergence of various new infectious (viral/bacteria) diseases, the remote surveillance of infected persons has become most important, especially if hospitals need to isolate infected patients to prevent the spreading of pathogens to health care personnel. Therefore, we develop a remote health monitoring system by integrating a stretchable asymmetric supercapacitor (SASC) as a portable power source with sensors that can monitor the human physical health condition in real-time and remotely. An abnormal body temperature and breathing rate could indicate a person's sickness/infection status. Here we integrated FePS₃@graphene-based strain sensor and SASC into an all-in-one textile system and wrapped it around the abdomen to continuously monitor the breathing cycle of the person. The real body temperature was recorded by integrating the temperature sensor with the SASC. The proposed system recorded physiological parameters in real-time and when monitored remotely could be employed as a screening tool for monitoring pathogen infection status.

Mixed Metal Thiophosphate Fe2-xCoxP2S6: Role of Structural Evolution and Anisotropy

Metal chalcophosphates, M₂P₂Q₆ (M = transition metals; Q = chalcogen), are notable among the van der Waals materials family for their potential magnetic ordering that can be tuned with an appropriate choice of the metal or chalcogen. However, there has not been a systematic investigation of the basic structural evolution in these systems with alloying of the crystal subunits due to the challenge in the diffusion process of mixing different metal cations in the octahedral sites of M₂P₂Q₆ materials. In this work, the P₂S₅ flux method was used to enable the synthesis of a multilayered mixed metal thiophosphate Fe_2-xCo_xP₂S₆ (x = 0, 0.25, 1, 1.75, and 2) system. Here, we studied the structural, vibrational, and electronic fingerprints of this mixed M₂P₂Q₆ system. Structural and elemental analyses indicate a homogeneous stoichiometry averaged through the sample over multiple layers of Fe_2-xCo_xP₂S₆ compounds. It was observed that there is a correlation between the intensity of specific phonon modes and the alloying concentration. The increasing Co alloying concentration shows direct relations to the in-plane [P₂S₆]^4- and out-of-plane P-P dimer vibrations. Interestingly, an unusual nonlinear electronic structure dependence on the metal alloying ratio is found and confirmed by two distinct work functions within the Fe_2-xCo_xP₂S₆ system. We believe this work provides a fundamental structural framework for mixed metal thiophosphate systems, which may assist in future studies on electronic and magnetic applications of this emerging class of binary cation materials.

Two-dimensional biomaterials: material science, biological effect and biomedical engineering applications

To date, nanotechnology has increasingly been identified as a promising and efficient means to address a number of challenges associated with public health. In the past decade, two-dimensional (2D) biomaterials, as a unique nanoplatform with planar topology, have attracted explosive interest in various fields such as biomedicine due to their unique morphology, physicochemical properties and biological effect. Motivated by the progress of graphene in biomedicine, dozens of types of ultrathin 2D biomaterials have found versatile bio-applications, including biosensing, biomedical imaging, delivery of therapeutic agents, cancer theranostics, tissue engineering, as well as others. The effective utilization of 2D biomaterials stems from the in-depth knowledge of structure-property-bioactivity-biosafety-application-performance relationships. A comprehensive summary of 2D biomaterials for biomedicine is still lacking. In this comprehensive review, we aim to concentrate on the state-of-the-art 2D biomaterials with a particular focus on their versatile biomedical applications. In particular, we discuss the design, fabrication and functionalization of 2D biomaterials used for diverse biomedical applications based on the up-to-date progress. Furthermore, the interactions between 2D biomaterials and biological systems on the spatial-temporal scale are highlighted, which will deepen the understanding of the underlying action mechanism of 2D biomaterials aiding their design with improved functionalities. Finally, taking the bench-to-bedside as a focus, we conclude this review by proposing the current crucial issues/challenges and presenting the future development directions to advance the clinical translation of these emerging 2D biomaterials.

Stable flexible photodetector based on FePS3/reduced graphene oxide heterostructure with significant enhancement in photoelectrochemical performance

Herein, FePS₃/reduced graphene oxide heterostructure has been prepared via a typical hydrothermal process, and flexible photodetectors based on hybrids have been subsequently fabricated. The photoresponse measurement results demonstrate that the photodetector exhibits obvious photoelectric conversion behavior without applied potential, indicating that the device possesses the capability to be self-powered. In addition, the photocurrent density of the as-fabricated photodetectors reaches up to 125 nA cm^-2under 90 mW cm^-2illumination intensity without an external power source, which is 5.86 times higher than single FePS₃-based devices. Furthermore, the maximum attenuation in photocurrent density of the as-fabricated flexible photodetectors measured at -0.3 V after different bending cycles and bending angles is 29.8% and 17.7%, respectively. These results demonstrate that the as-fabricated photodetectors have excellent flexibility and provide a simple and effective strategy for the construction of flexible photodetectors.

Electronic Structure and d-Band Center Control Engineering over Ni-Doped CoP3 Nanowall Arrays for Boosting Hydrogen Production

To address the challenge of highly efficient water splitting into H₂, successful fabrication of novel porous three-dimensional Ni-doped CoP₃ nanowall arrays on carbon cloth was realized, resulting in an effective self-supported electrode for the electrocatalytic hydrogen-evolution reaction. The synthesized samples exhibit rough, curly, and porous structures, which are beneficial for gaseous transfer and diffusion during the electrocatalytic process. As expected, the obtained Ni-doped CoP₃ nanowall arrays with a doping concentration of 7% exhibit the promoted electrocatalytic activity. The achieved overpotentials of 176 mV for the hydrogen-evolution reaction afford a current density of 100 mA cm⁻², which indicates that electrocatalytic performance can be dramatically enhanced via Ni doping. The Ni-doped CoP₃ electrocatalysts with increasing catalytic activity should have significant potential in the field of water splitting into H₂. This study also opens an avenue for further enhancement of electrocatalytic performance through tuning of electronic structure and d-band center by doping.

Cobalt Phosphorous Trisulfide as a High-Performance Electrocatalyst for the Oxygen Evolution Reaction

Two-dimensional (2D) layered materials are currently one of the most explored materials for developing efficient and stable electrocatalysts in energy conversion applications. Some of the 2D metal phosphorous trichalcogenides (M₂P₂X₆ or MPX₃ in its simplified form) have been reported to be useful catalysts for water splitting, although results have been less promising for the sluggish oxygen evolution reaction (OER) due to insufficient activity or compromised stability. Herein, we report the OER catalysis of a series of M₂P₂X₆ (M²⁺ = Mn, Fe, Co, Zn, Cd; X = S, Se). From the series of MPX₃, CoPS₃ yields the best results with an overpotential within the range of values usually obtained for IrO₂ or RuO₂ catalysts. The liquid-phase exfoliation of CoPS₃ even improves the OER activity due to abundant active edges of the downsized sheets, accompanied by the presence of surface oxides. The influence of the OER medium and underlying substrate electrode is studied, with the exfoliated CoPS₃ reaching the lowest overpotential at 234 mV at a current density of 10 mA/cm², also able to sustain high current densities, with an overpotential of 388 mV at a current density of 100 mA/cm², and excellent stability after multiple cycles or long-term operation. Quantum chemical models reveal that these observations are likely tied to moieties on CoPS₃ edges, which are responsible for low overpotentials through a two-site mechanism. The OER performance of exfoliated CoPS₃ reported herein yields competitive values compared to those reported for other Co-based and MPX₃ in the literature, thus holding substantial promise for use as an efficient material for the anodic water-splitting reaction.

A multifunctional Fenton nanoagent for microenvironment-selective anti-biofilm and anti-inflammatory therapy

Bacterial biofilm infections are intractable to traditional antibiotic treatment and usually cause persistent inflammation. Chemodynamic therapy (CDT) based on the Fenton reaction has recently emerged as a promising anti-biofilm strategy. However, the therapeutic efficacy of current Fenton agents often suffers from inefficient Fenton activity and lacks anti-inflammatory capability. Herein, FePS₃ nanosheets (NSs) are explored for the first time as novel microenvironment-selective therapeutic nanoagents for bacterial biofilm infections with both self-enhanced Fenton activity for an anti-biofilm effect and reactive oxygen species (ROS) scavenging properties for an anti-inflammatory effect. In biofilms with acidic microenvironments, FePS₃ NSs release Fe²⁺ to generate toxic ROS by Fenton reaction and reductive [P₂S₆]^4- to enhance the Fenton activity by reducing Fe³⁺ to Fe²⁺. In the surrounding normal tissues with neutral pH, FePS₃ NSs scavenge ROS by reductive [P₂S₆]^4- with an anti-inflammatory effect. This work demonstrates multifunctional Fenton nanoagents with microenvironment-selective ROS generation and elimination properties for effective treatment of bacterial biofilm infections with both anti-biofilm and anti-inflammatory effects.

Two-dimensional materials in biomedical, biosensing and sensing applications

Two-dimensional (2D) materials are at the forefront of materials research. Here we overview their applications beyond graphene, such as transition metal dichalcogenides, monoelemental Xenes (including phosphorene and bismuthene), carbon nitrides, boron nitrides along with transition metal carbides and nitrides (MXenes). We discuss their usage in various biomedical and environmental monitoring applications, from biosensors to therapeutic treatment agents, their toxicity and their utility in chemical sensing. We highlight how a specific chemical, physical and optical property of 2D materials can influence the performance of bio/sensing, improve drug delivery and photo/thermal therapy as well as affect their toxicity. Such properties are determined by crystal phases electrical conductivity, degree of exfoliation, surface functionalization, strong photoluminescence, strong optical absorption in the near-infrared range and high photothermal conversion efficiency. This review conveys the great future of all the families of 2D materials, especially with the expanding 2D materials' landscape as new materials emerge such as germanene and silicene.

Towards Antimonene and 2D Antimony Telluride through Electrochemical Exfoliation

Two-dimensional (2D) layered antimony (Sb) and antimony telluride (Sb₂ Te₃ ) are two valuable materials for optoelectronic devices and thermoelectric applications. Preparing high-quality sheets of these materials is the initial phase to promote their expected issues. Herein, micrometer-sized few-to-multilayered sheets of Sb and Sb₂ Te₃ have been obtained by electrochemical exfoliation. The layered rhombohedral Sb was exfoliated in Na₂ SO₄ and Li₂ SO₄ electrolytes by anodic-cationic intercalation, and Sb₂ Te₃ was exfoliated in Na₂ SO₄ . These findings are important contributions for the solution-based room-temperature electrochemical exfoliation, which is stable under glove-box-free conditions, to further improve the production of high-quality exfoliated sheets.

Synthesis, crystal structure, and magnetic properties of layered SmCrS2−xSexO solid solutions

Layered SmCrS_2−xSe_xO (x = 0–2) solid solutions were synthesized which show typical antiferromagnetic orderings.

Iron phosphorus trichalcogenide ultrathin nanosheets: enhanced photoelectrochemical activity under visible-light irradiation

Exploiting novel visible-light sensitive materials for the photoelectrochemical (PEC) technique is deeply meaningful for energy conversion and analytic detection. Owing to the tunable bandgap structure and strong absorption of visible light, the rising-star two-dimensional (2D) metal phosphorus trichalcogenide (MPX₃) nanomaterials are expected to be promising photochemical sensitizers toward PEC biosensors. Moreover, guided by DFT calculations, the FePS₃ nanosheets possessed a narrower bandgap than the bulk form, thereby enabling high availability of visible-light absorption for the FePS₃ nanosheets. In this work, 2D FePS₃ nanosheets were successfully synthesized by a facile salt-templated method. By tuning the proportion of the salt template, the thickness of the FePS₃ nanosheets could be manipulated. As a result, the FePS₃ nanosheets exhibited an obviously enhanced photoelectrochemical behavior with visible light and sensitive detection towards glucose. Being the first experimental report regarding the MPS₃ nanosheets toward PEC activity, our finding can be an essential stepping stone in the pursuit of the further exploration of other 2D materials for the PEC technology.

MoS2 versatile spray-coating of 3D electrodes for the hydrogen evolution reaction

A facile one-step MoS₂ spray-coating method was applied to a range of rigid, flexible, porous and 3D printed carbon-based surfaces, yielding high loadings in MoS₂ flakes. The characterization of MoS₂ flakes from a commercial lubricant spray reveals up to micron-scale bulk sheets of the layered material, constituted in its majority by the semiconducting 2H polymorph, in the presence of the metallic 1T phase. Consequently, the process generates MoS₂ spray-coated surfaces with improved hydrogen evolution reaction (HER) catalytic performance. In the case of carbon-based screen printed electrodes (SPE), a short-term thermal post-treatment of the MoS₂ spray-coated SPE had a further beneficial effect in the HER overpotential. The MoS₂ spray-coated 3D metallic meshes held the lowest HER overpotential of the series. Finally, MoS₂ spray-coated 3D printed electrodes yielded improved heterogeneous charge transfer and a 500 mV shift in the required overpotential at a current density of -10 mA cm^-2. The MoS₂ spray-coated 3D printed electrode displayed an abundant coverage at the inner, external and planar zones of electrodes by the MoS₂ sheets, even after long-term operation conditions. These outcomes can be beneficial for future tailoring of MoS₂ spray-coated surfaces and their implementation in energy conversion technologies.