Synergetic Advantages of Atomically Coupled 2D Inorganic and Graphene Nanosheets as Versatile Building Blocks for Diverse Functional Nanohybrids

Rational regulation of post-electrodialysis electrochromic anion exchange membranes via TiO2@Ag synergistically strengthens visible-light photocatalytic anti-contamination activity

Membrane-contamination during electrodialysis (ED) process is still a non-negligible challenge, while irreversible consumption and unsustainability have become the main bottlenecks limiting the improvement of anion exchange membranes (AEMs) anti-contamination activity. Here, we introduce a novel approach to design AEMs by chemically assembling 4-pyndinepropanol with bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) in an electrochromic-inspired process. Subsequently, the co-mingled TiO2@Ag nanosheet with the casting-solution were sprayed onto the surface of the substrate membrane to create a micrometer-thick interfacial layer. The addition of Ag nanoparticles (NPs) enhances the active sites of TiO2, resulting in stronger local surface plasmon resonance (LSPR) effects and reducing its energy band gap limitation (From 3.11 to 2.63 eV). Post-electrodialysis electrochromic AEMs incorporating TiO2@Ag exhibit synergistic enhancement of sunlight absorption, effectively suppressing photogenerated carrier binding and promoting migration. These resultant-membranes demonstrate significantly improved bacterial inhibition properties (42.0-fold increase for E. coli) and degradation activity (7.59-fold increase for rhodamine B) compared to pure TiO2 membranes. Importantly, they maintain photocatalytic activity without compromising salt-separation performance or stability, as the spraying process utilizes the same substrate materials. This approach to rational design and regulation of anti-contamination AEMs offers new insights into the collaborative synergy of color-changing and photocatalytic materials.

Crucial Role of Metal Coordination Number in Optimizing Electrocatalyst Activity of Holey Large-Area 2D Ru Nanosheets

Low-dimensional metal nanostructures have attracted considerable research attention, owing to their potential as catalysts. A controlled reductive phase transition of monolayer RuO2 nanosheets could provide an effective way to produce holey large-area 2D Ru nanosheets with tailored defect structures and metal coordination number. The locally optimized holey Ru metal nanosheet, with a metal coordination number of ∼10.2, exhibited excellent electrocatalytic activity for the hydrogen evolution reaction (HER) with a reduced overpotential of 38 mV in a 1 M KOH electrolyte. The creation of a highly anisotropic holey nanosheet morphology with optimization of local structure was quite effective in developing efficient catalyst materials. The universal importance of controlling the coordination number was confirmed through a comparative study of Ru nanoparticles, which showed optimized HER activity with an identical metal coordination number. The coordination number plays a pivotal role in governing electrocatalytic activity, which could be ascribed to the formation of the most active structure for HER at most 2 defects near active sites (2,2'), resulting in the stabilization of a dihydrogen Ru-(H2) intermediate and the increased contribution of Volmer-Tafel mechanism.

Ammonolysis-Driven Exsolution of Ru Nanoparticle Embedded in Conductive Metal Nitride Matrix to Boost Electrocatalyst Activity

Exsolution is an effective method for synthesizing robust nanostructured metal-based functional materials. However, no studies have investigated the exsolution of metal nanoparticles into metal nitride substrates. In this study, a versatile nitridation-driven exsolution method is developed for embedding catalytically active metal nanoparticles in conductive metal nitride substrates via the ammonolysis of multimetallic oxides. Using this approach, Ti1-xRuxO2 nanowires are phase-transformed into holey TiN nanotubes embedded with exsolved Ru nanoparticles. These Ru-exsolved holey TiN nanotubes exhibit outstanding electrocatalytic activity for the hydrogen evolution reaction with excellent durability, which is significantly higher than that of Ru-deposited TiN nanotubes. The enhanced stability of the Ru-exsolved TiN nanotubes can be attributed to the Ru nanoparticles embedded in the robust metal nitride matrix and the formation of interfacial Ti3+─N─Ru4+ bonds. Density functional theory calculations reveal that the exsolved Ru nanoparticles have a lower d-band center position and optimized hydrogen affinity than deposited Ru nanoparticles, indicating the superior electrocatalyst performance of the former. In situ Raman spectroscopic analysis reveals that the electron transfer from TiN to Ru nanoparticles is enhanced during the electrocatalytic process. The proposed approach opens a new avenue for stabilizing diverse metal nanostructures in many conductive matrices like metal phosphides and chalcogenides.

General and Scalable Synthesis of Mesoporous 2D MZrO2 (M = Co, Mn, Ni, Cu, Fe) Nanocatalysts by Amorphous-to-Crystalline Transformation

In modern heterogeneous catalysis, it remains highly challenging to create stable, low-cost, mesoporous 2D photo-/electro-catalysts that carry atomically dispersed active sites. In this work, a general shape-preserving amorphous-to-crystalline transformation (ACT) strategy is developed to dope various transition metal (TM) heteroatoms in ZrO2, which enabled the scalable synthesis of TMs/oxide with a mesoporous 2D structure and rich defects. During the ACT process, the amorphous MZrO2 nanoparticles (M = Fe, Ni, Cu, Co, Mn) are deposited within a confined space created by the NaCl template, and they transform to crystalline 2D ACT-MZrO2 nanosheets in a shape-preserving manner. The interconnected crystalline ACT-MZrO2 nanoparticles thus inherit the same structure as the original MZrO2 precursor. Owing to its rich active sites on the surface and abundant oxygen vacancies (OVs), ACT-CoZrO2 gives superior performance in catalyzing the CO2-to-syngas conversion as demonstrated by experiments and theoretical calculations. The ACT chemistry opens a general route for the scalable synthesis of advanced catalysts with precise microstructure by reconciliating the control of crystalline morphologies and the dispersion of heteroatoms.

Enhancing Hydrogen Evolution Reaction Activity of Palladium Catalyst by Immobilization on MXene Nanosheets

Efficient catalysts with minimal content of catalytically active noble metals are essential for the transition to the clean hydrogen economy. Catalyst supports that can immobilize and stabilize catalytic nanoparticles and facilitate the supply of electrons and reactants to the catalysts are needed. Being hydrophilic and more conductive compared with carbons, MXenes have shown promise as catalyst supports. However, the controlled assembly of their 2D sheets creates a challenge. This study established a lattice engineering approach to regulate the assembly of exfoliated Ti3C2Tx MXene nanosheets with guest cations of various sizes. The enlargement of guest cations led to a decreased interlayer interaction of MXene lamellae and increased surface accessibility, allowing intercalation of Pd nanoparticles. Stabilization of Pd nanoparticles between interlayer-expanded MXene nanosheets improved their electrocatalytic activity. The Pd-immobilized K+-intercalated MXene nanosheets (PdKMX) demonstrated exceptional electrocatalytic performance for the hydrogen evolution reaction with the lowest overpotential of 72 mV (@10 mA cm-2) and the highest turnover frequency of 1.122 s-1 (@ an overpotential of 100 mV), which were superior to those of the state-of-the-art Pd nanoparticle-based electrocatalysts. Weakening of the interlayer interaction during self-assembly with K+ ions led to fewer layers in lamellae and expansion of the MXene in the c direction during Pd anchoring, providing numerous surface-active sites and promoting mass transport. In situ spectroscopic analysis suggests that the effective interfacial electron injection from the Pd nanoparticles strongly immobilized on interlayer-expanded PdKMX may be responsible for the improved electrocatalytic performance.

Incorporation of Photo- and Thermoresponsive N-Salicylidene Aniline Derivatives into Cobalt and Zinc Layered Hydroxides

In search of new multifunctional hybrid materials and in order to investigate the influence of chemical modification on the possible synergy between properties, the carboxylate and sulfonate derivatives of photo- and thermochromic N-salicylidene aniline were successfully inserted into Co(II)- and Zn(II)-based layered simple hydroxides, resulting in four novel hybrids: Co-N-Sali-COO, Co-N-Sali-SO3, Zn-N-Sali-COO, and Zn-N-Sali-SO3. All synthesized hybrids adopt a double organic layered configuration, which prevents the cis-trans photoisomerization ability of N-Sali-R molecules in the hybrids. However, the Zn hybrids exhibit fluorescence upon exposure to UV light due to the excited-state intramolecular proton transfer (ESIPT) mechanism. The thermally stimulated keto-enol tautomerization of N-salicylidene aniline in the hybrids was related with the changes in interlamellar spacings observed by temperature-dependent PXRD. This tautomerization process was prominently evident in the Co-N-Sali-SO3 hybrid (about 11% increase in d-spacing upon decreasing the temperature to -180 °C). Finally, the Co-N-Sali-R hybrids exhibit the typical magnetic behavior associated with Co(II)-based LSHs (ferrimagnetic ordering at TN = 6.8 and 7.7 K for Co-N-Sali-COO and Co-N-Sali-SO3, respectively). This work offers insights into isomerization in LSHs and the ESIPT mechanism's potential in new luminescent materials and prospects for designing new multifunctional materials.

Defect-Regulated Two-Dimensional Superlattice of Holey g-C3N4TiO2 Nanohybrids: Contrasting Influence of Vacancy Content on Hybridization Impact and Photocatalyst Performance

Defect engineering provides an effective way to explore efficient nanostructured catalysts. Herein, we synthesize defect-regulated two-dimensional superlattices comprising interstratified holey g-C3N4 and TiO2 monolayers with tailorable interfacial coupling. Using this interfacial-coupling-controlled hybrid system, a strong interdependence among vacancy content, performance, and interfacial coupling was elucidated, offering key insights for the design of high-performance catalysts. The defect-optimized g-C3N4-TiO2 superlattice exhibited higher photocatalytic activity toward visible-light-induced N2 fixation (∼1.06 mmol g-1 h-1) than defect-unoptimized and disorderly assembled g-C3N4-TiO2 homologues. The high photocatalytic performance of g-C3N4-TiO2 was attributed to the hybridization-induced defect creation, facilitated hydrogenation of adsorbed nitrogen, and improvement in N2 adsorption and charge transport. A comparison of the defect-dependent photocatalytic activity of g-C3N4, g-C3N4 nanosheets, and g-C3N4-TiO2 revealed the presence of optimal defect content for improving photocatalytic performance and the continuous increase of hybridization impact with the defect content. Sophisticated mutual influence among defect, electronic coupling, and photocatalytic ability underscores the importance of defect fine control in exploring high-performance hybrid photocatalysts. Along with the DFT calculation, the excellent photocatalyst performance of defect-optimized g-C3N4-TiO2 can be ascribed to the promotion of the uphill *N hydrogenation step as well as to enhancement of N2 adsorption, charge transfer kinetics, and mass transports.

Electrochemically Versatile Graphite Nanoplatelets Prepared by a Straightforward, Highly Efficient, and Scalable Route

Nanostructured carbon materials with tailor-made structures (e.g., morphology, topological defect, dopant, and surface area) are of significant interest for a variety of applications. However, the preparation method selected for obtaining these tailor-made structures determines the area of application, precluding their use in other technological areas of interest. Currently, there is a lack of simple and low-cost methodologies versatile enough for obtaining freestanding carbon nanostructures that can be used in either energy storage or chemical detection. Here, a novel methodology for the development of a versatile electrochemically active platform based on freestanding graphite nanoplatelets (GNP) has been developed by exploiting the interiors of hollow carbon nanofibers (CNF) comprising nanographene stacks using dry ball-milling. Even though ball-milling could be considered as a universal method for any carbonaceous material, often, it is not as simple (one step, no purification, and no solvents), efficient (just GNP without tubular structures), and quick (just 20 min) as the sustainable method developed in this work, free of surfactants and stabilizer agents. We demonstrate that the freestanding GNP developed in this work (with an average thickness of 3.2 nm), due to the selective edge functionalization with the minimal disruption of the basal plane, can act either as a supercapacitor or as a chemical sensor, showing both a dramatic improvement in the charge storage ability of more than 30 times and an enhanced detection of electrochemically active molecules such as ascorbic acid with a 236 mV potential shift with respect to CNF in both cases. As shown here, GNP stand as an excellent versatile alternative compared to the standard commercially available carbon-based materials. Overall, our approach paves the way for the discovery of new nanocarbon-based electrochemical active platforms with a wide electrochemical applicability.

Applications of Graphene in Five Senses, Nervous System, and Artificial Muscles

Graphene remains of great interest in biomedical applications because of biocompatibility. Diseases relating to human senses interfere with life satisfaction and happiness. Therefore, the restoration by artificial organs or sensory devices may bring a bright future by the recovery of senses in patients. In this review, we update the most recent progress in graphene based sensors for mimicking human senses such as artificial retina for image sensors, artificial eardrums, gas sensors, chemical sensors, and tactile sensors. The brain-like processors are discussed based on conventional transistors as well as memristor related neuromorphic computing. The brain-machine interface is introduced for providing a single pathway. Besides, the artificial muscles based on graphene are summarized in the means of actuators in order to react to the physical world. Future opportunities remain for elevating the performances of human-like sensors and their clinical applications.

Stabilization and Performance Enhancement Strategies for Halide Perovskite Photocatalysts

Solar-energy-powered photocatalytic fuel production and chemical synthesis are widely recognized as viable technological solutions for a sustainable energy future. However, the requirement of high-performance photocatalysts is a major bottleneck. Halide perovskites, a category of diversified semiconductor materials with suitable energy-band-enabled high-light-utilization efficiencies, exceptionally long charge-carrier-diffusion-length-facilitated charge transport, and readily tailorable compositional, structural, and morphological properties, have emerged as a new class of photocatalysts for efficient hydrogen evolution, CO₂ reduction, and various organic synthesis reactions. Despite the noticeable progress, the development of high-performance halide perovskite photocatalysts (HPPs) is still hindered by several key challenges: the strong ionic nature and high hydrolysis tendency induce instability and an unsatisfactory activity due to the need for a coactive component to realize redox processes. Herein, the recently developed advanced strategies to enhance the stability and photocatalytic activity of HPPs are comprehensively reviewed. The widely applicable stability enhancement strategies are first articulated, and the activity improvement strategies for fuel production and chemical synthesis are then explored. Finally, the challenges and future perspectives associated with the application of HPPs in efficient production of fuels and value-added chemicals are presented, indicating the irreplaceable role of the HPPs in the field of photocatalysis.

Covalently Interlayer-Confined Organic-Inorganic Heterostructures for Aqueous Potassium Ion Supercapacitors

Artificial assembly of organic-inorganic heterostructures for electrochemical energy storage at the molecular level is promising, but remains a great challenge. Here, a covalently interlayer-confined organic (polyaniline [PANI])-inorganic (MoS₂ ) hybrid with a dual charge-storage mechanism is developed for boosting the reaction kinetics of supercapacitors. Systematic characterizations reveal that PANI induces a partial phase transition from the 2H to 1T phases of MoS₂ , expands the interlayer spacing of MoS₂ , and increases the hydrophilicity. More in-depth insights from the synchrotron radiation-based X-ray technique illustrate that the covalent grafting of PANI to MoS₂  induces the formation of MoN bonds and unsaturated Mo sites, leading to increased active sites. Theoretical analysis reveals that the covalent assembly facilitates cross-layer electron transfer and decreases the diffusion barrier of K⁺ ions, which favors reaction kinetics. The resultant hybrid material exhibits high specific capacitance and good rate capability. This design provides an effective strategy to develop organic-inorganic heterostructures for superior K-ion storage. The K-ion storage mechanism concerning the reversible insertion/extraction upon charge/discharge is revealed through ex situ X-ray photoelectron spectroscopy.

Atomically Thin Holey Two-Dimensional Ru2P Nanosheets for Enhanced Hydrogen Evolution Electrocatalysis

The defect engineering of low-dimensional nanostructured materials has led to increased scientific efforts owing to their high efficiency concerning high-performance electrocatalysts that play a crucial role in renewable energy technologies. Herein, we report an efficient methodology for fabricating atomically thin, holey metal-phosphide nanosheets with excellent electrocatalyst functionality. Two-dimensional, subnanometer-thick, holey Ru₂P nanosheets containing crystal defects were synthesized via the phosphidation of monolayer RuO₂ nanosheets. Holey Ru₂P nanosheets exhibited superior electrocatalytic activity for the hydrogen evolution reaction (HER) compared to that exhibited by nonholey Ru₂P nanoparticles. Further, holey Ru₂P nanosheets exhibited overpotentials of 17 and 26 mV in acidic and alkaline electrolytes, respectively. Thus, they are among the best-performing Ru-P-based HER catalysts reported to date. In situ spectroscopic investigations indicated that the holey nanosheet morphology enhanced the accumulation of surface hydrogen through the adsorption of protons and/or water, resulting in an increased contribution of the Volmer-Tafel mechanism toward the exceptional HER activity of these ultrathin electrocatalysts.

All-Gas-Phase Synthesis of Heterolayered Two-Dimensional Nanohybrids Decorated with Metallic Nanocatalysts for Water Splitting

Herein, a sequential gas-phase process involving air jet milling followed by chemical vapor deposition (CVD), is demonstrated to be an efficient strategy for the fabrication of heterolayered 2D nanohybrids (2DNHs) decorated with nanocatalysts. Tens of grams of the nanohybrids, which is a substantial quantity at the laboratory scale, are produced in the absence of solvents and water, and without the need for an extra purification procedure. Air jet milling enables the development of binary/ternary heterolayered structures consisting of graphene, WSe₂ , and/or MoS₂ via the gas-phase co-exfoliation of their bulk counterparts. Based on the X-ray photoelectron and Raman spectroscopy data, the heterolayers of the 2DNHs exert chemical and electronic effects on each other, while diminishing the interactions between same-component layers. Moreover, the electrochemically active surface area increases by >190% and the charge transfer resistance decreases by >35%. CVD is performed to introduce Pt and Ru nanoparticles with diameters of a few nanometers as additional electrocatalysts into the 2DNHs. The nanocatalyst-decorated 2DNHs show excellent performance for the production of hydrogen and oxygen gases in water-splitting cells. Notably, the proposed all-gas-phase processes allow for the large-scale production of functional 2DNHs with minimal negative environmental impact, which is crucial for the commercialization of nanomaterials.

Interaction of Nucleic Acids with Metal-Organic Framework Nanosheets by Fluorescence Spectroscopy and Molecular Dynamics Simulations

The integration of nanomaterials and nucleic acids has attracted great attention in various research fields, especially biomedical applications. Designing two-dimensional nanomaterials and studying the mechanism of their interaction with nucleic acids are still attractive tasks. Herein, we designed and prepared a class of ultrathin two-dimensional metal-organic framework (MOF) nanosheets, named Zr-BTB MOF nanosheets, composed of Zr-O clusters and 1,3,5-benzenetribenzoate by a bottom-up synthesis strategy. The Zr-BTB MOF nanosheets possessed inherent excellent performance such as a high specific surface area, porosity, and biocompatibility. In addition, we clarified the interaction difference between the Zr-BTB MOF nanosheets and fluorophore-labeled double-stranded DNA and single-stranded DNA via molecular dynamics simulations and fluorescence measurement. Through molecular dynamics simulations, specific interactions between DNA and nanosheets such as forces, binding energies, and binding modes were deeply analyzed and clearly presented. Based on the affinity difference, the system showed the biosensing potential for target DNA detection with considerable specificity, sensitivity, and linearity. Our research results presented the Zr-BTB MOF nanosheet as a platform for nucleic acid detection, showing the potential for hybridization-based biosensing and related biological applications.

Constructing titanium carbide MXene/reduced graphene oxide superlattice heterostructure via electrostatic self-assembly for high-performance capacitive deionization

Capacitive deionization has attracted wide concern on accountof its high energy efficiency, low manufacturing cost and environmental friendliness. Nevertheless, the development of capacitive deionization is still impeded because of the scarcity of suitable electrode materials with superior performance. Herein, we successfully prepared the two-dimensional (2D) titanium carbide (Ti₃C₂T_x) MXene/ reduced graphene oxide (rGO) superlattice heterostructure by a facile electrostatic self-assembly strategy and systematically investigated its performance as capacitive deionized electrode materials. The unique 2D/2D superlattice heterostructure not only effectively alleviates the self-stacking problem of Ti₃C₂T_x MXene nanosheets, but also endows the heterostructure with superior conductivity and fast ion diffusion rate. As a result, the MXene/rGO superlattice heterostructure exhibits an outstanding salt (Na⁺) adsorption capacity (48 mg g^-1) at 1.2 V significantly superior to pristine Ti₃C₂T_x MXene nanosheets, along with outstanding long-term cycling performance. Furthermore, the mechanism involved was elucidated through comprehensive characterizations. Therefore, this study offers a new pathway for designing high-performance electrode materials for capacitive deionization.

Ion exchange membrane optimized light-driven photoelectrochemical unit for efficiency simultaneous organic degradation and metal recovery from the mine wastewater

Resource recovery from wastewater is a promising and challenging topic. Herein, a well-designed ion exchange membrane optimized light-driven photoelectrochemical unit (MPECS) was constructed to reduce the effect of inorganic salt on the photoelectrochemical performance of the photoanode. TiO₂/carbon dots/WO₃ (TCDW) photoanode with the indirect Z-scheme heterojunction structure was successfully fabricated, achieving a strong light harvest performance (10.82%) and a high photocurrent density (5.39 mA/cm²). For the simulated solution (0.01 M phenol and 0.01 M CuSO₄), the phenol degradation and Cu recovery efficiencies reached 99.67% and 62.20% in 60 min, respectively, and the corresponding photoelectric conversion efficiency (PECE) reached 4.64% in the TCDW/Pt-based MPECS. For the actual Cu-laden mine wastewater, over 98% of inorganic salt was removed. Compared to the traditional photoelectrochemical system (PECS), the COD removal and Cu recovery efficiencies were further improved by 23.77% and 49.41% in MPECS, respectively. The results exhibited a promising light-driven mine wastewater treatment technology.

Wet-chemical synthesis of two-dimensional metal nanomaterials for electrocatalysis

Two-dimensional (2D) metal nanomaterials have gained ever-growing research interest owing to their fascinating physicochemical properties and promising application, especially in the field of electrocatalysis. In this review, we briefly introduce the recent advances in wet-chemical synthesis of 2D metal nanomaterials. Subsequently, the catalytic performances of 2D metal nanomaterials in a variety of electrochemical reactions are illustrated. Finally, we summarize current challenges and highlight our perspectives on preparing high-performance 2D metal electrocatalysts.

Atom manufacturing of photocatalyst towards solar CO2reduction

Photocatalytic CO₂reduction reaction (CO₂RR) is believed to be a promising remedy to simultaneously lessen CO₂emission and obtain high value-added products, but suffers from the thwarted activity of photocatalyst and poor selectivity of product. Over the past decade, aided by the significant advances in nanotechnology, the atom manufacturing of photocatalyst, including vacancies, dopants, single-atom catalysts, strains, have emerged as efficient approaches to precisely mediate the reaction intermediates and processes, which push forward in the rapid development of highly efficient and selective photocatalytic CO₂RR. In this review, we summarize the recent developments in highly efficient and/or selective photocatalysts toward CO₂RR with the special focus on various atom manufacturing. The mechanisms of these atom manufacturing from active sites creation, light absorbability, and electronic structure modulation are comprehensively and scientifically discussed. In addition, we attempt to establish the structure-activity relationship between active sites and photocatalytic CO₂RR capability by integrating theoretical simulations and experimental results, which will be helpful for insights into mechanism pathways of CO₂RR over defective photocatalysts. Finally, the remaining challenges and prospects in this field to improve the photocatalytic CO₂RR performances are proposed, which can shed some light on designing more potential photocatalysts through atomic regulations toward CO₂conversion.

Synthesis of two-Dimensional layered double hydroxide: A systematic overview

Two-dimensional (2D) layered double hydroxides (LDH) are classic materials in fundamental research and practical application. 2D LDH have unique structural features, such as high aspect ratio, high specific surface area,...

In Situ Defect Engineering Route to Optimize the Cationic Redox Activity of Layered Double Hydroxide Nanosheet via Strong Electronic Coupling with Holey Substrate

A defect engineering of inorganic solids garners great deal of research activities because of its high efficacy to optimize diverse energy-related functionalities of nanostructured materials. In this study, a novel in situ defect engineering route to maximize electrocatalytic redox activity of inorganic nanosheet is developed by using holey nanostructured substrate with strong interfacial electronic coupling. Density functional theory calculations and in situ spectroscopic analyses confirm that efficient interfacial charge transfer takes place between holey TiN and Ni-Fe-layered double hydroxide (LDH), leading to the feedback formation of nitrogen vacancies and a maximization of cation redox activity. The holey TiN-LDH nanohybrid is found to exhibit a superior functionality as an oxygen electrocatalyst and electrode for Li-O2 batteries compared to its non-holey homologues. The great impact of hybridization-driven vacancy introduction on the electrochemical performance originates from an efficient electrochemical activation of both Fe and Ni ions during electrocatalytic process, a reinforcement of interfacial electronic coupling, an increase in electrochemical active sites, and an improvement in electrocatalysis/charge-transfer kinetics.

Two-Dimensional Red Phosphorus Nanosheets: Morphology Tuning and Electrochemical Sensing of Aromatic Amines

Synthesis of 2D materials with different morphologies is of significance to reveal their morphology-dependent properties and further explore their morphology-dependent applications. This work reports the synthesis of 2D red phosphorus nanosheets (RPNSs) with different thicknesses by means of a phosphorus-amine method together with regulated electrophilicity of the solution. With graphene as the support, the RPNSs produced in 0.01 m HCl feature a unique 2D nanostructure, uniform distribution, and excellent electrochemical performance. Originating from the reacted characteristics between phosphorus and amine, the interaction of aniline with the RPNSs is clarified theoretically and experimentally by means of density functional theory, X-ray photoelectron spectroscopy, and voltammetry. A covalent bond is confirmed to be formed during the deprotonation of aniline and its binding energy reaches -2.31 eV. Stemming from such an adsorption process, different aromatic amines (e.g., p-nitroaniline, p-phenylenediamine) are sensitively and selectively monitored on the RPNSs. Consequently, this work provides a new way to clarify morphology-dependent properties and applications of novel 2D materials.

Molecular-Level Control of the Intersheet Distance and Electronic Coupling between 2D Semiconducting and Metallic Nanosheets: Establishing Design Rules for High-Performance Hybrid Photocatalysts

Hybridization with conductive nanospecies has attracted intense research interest as a general effective means to improve the photocatalytic functionalities of nanostructured materials. To establish universal design rules for high-performance hybrid photocatalysts, correlations between versatile roles of conductive species and interfacial interaction between hybridized species are systematically investigated through fine-control of intersheet distance between photocatalytically active TiO2 and metallic reduced graphene oxide (rGO)/RuO2 nanosheets. Molecular-level tailoring of intersheet distance and electronic coupling between 2D nanosheets can be successfully achieved by restacking of colloidal nanosheet mixture with variable-sized organic intercalants. While the shortest intersheet distance between restacked TiO2 and rGO nanosheets leads to the highest visible-light-driven photocatalytic activity, the best UV-vis photocatalyst performance occurs for moderate intersheet spacing. These results highlight the greater sensitivity of photoinduced electronic excitation to the intersheet distance than that of interfacial charge transfer. The rGO nanosheet can function as effective charge transport pathway and cocatalyst within ≈1.7 nm distance from the semiconducting nanosheet, and as efficient stabilizer for hybridized photocatalyst within ≈1.8 nm. The present study underscores that the intercalative restacking of colloidal nanosheet mixture with intercalants enables molecular-level control of distance between 2D inorganic/graphene nanosheets, which provides a rational design strategy for high-performance hybrid photocatalysts.