Ultrasonic Exfoliation Research Articles

Synthesis and Hydrogen Production Performance of MoP/a-TiO2/Co-ZnIn2S4 Flower-like Composite Photocatalysts.

Semiconductor photocatalysis is an effective strategy for solving the problems of increasing energy demand and environmental pollution. ZnIn2S4-based semiconductor photocatalyst materials have attracted much attention in the field of photocatalysis due to their suitable energy band structure, stable chemical properties, and good visible light responsiveness. In this study, ZnIn2S4 catalysts were modified by metal ion doping, the construction of heterojunctions, and co-catalyst loading to successfully prepare composite photocatalysts. The Co-ZnIn2S4 catalyst synthesized by Co doping and ultrasonic exfoliation exhibited a broader absorption band edge. Next, an a-TiO2/Co-ZnIn2S4 composite photocatalyst was successfully prepared by coating partly amorphous TiO2 on the surface of Co-ZnIn2S4, and the effect of varying the TiO2 loading time on photocatalytic performance was investigated. Finally, MoP was loaded as a co-catalyst to increase the hydrogen production efficiency and reaction activity of the catalyst. The absorption edge of MoP/a-TiO2/Co-ZnIn2S4 was widened from 480 nm to about 518 nm, and the specific surface area increased from 41.29 m2/g to 53.25 m2/g. The hydrogen production performance of this composite catalyst was investigated using a simulated light photocatalytic hydrogen production test system, and the rate of hydrogen production by MoP/a-TiO2/Co-ZnIn2S4 was found to be 2.96 mmol·h-1·g-1, which was three times that of the pure ZnIn2S4 (0.98 mmol·h-1·g-1). After use in three cycles, the hydrogen production only decreased by 5%, indicating that it has good cycle stability.

Easy three steps gC3N4 exfoliation for excellent photocatalytic activity – An in-depth comparison with conventional approaches

Producing an ultrathin nanostructure through exfoliation of carbon nitride (gC3N4) significantly enhances the photoactivity of the material. However, the influence of the exfoliation method on the properties and photocatalytic activity of gC3N4 nanosheets is still poorly understood. In this study, conventional methods such as thermal, chemical and ultrasonic exfoliation of gC3N4 nanosheets have been compared with a three-step exfoliation method. The three-step exfoliation strategy allows the control of the microstructure, light absorption property, morphology and visible light photoactivity of gC3N4 nanosheets. Products show a superior photocatalytic efficiency under simulated sunlight compared to gC3N4 nanosheets obtained with conventional exfoliation methods. Degradation kinetics of this material are also superior. gC3N4 nanosheets prepared by three-step exfoliation exhibit a high specific surface area, optimal band gap energy structure, higher electron density and more efficient charge separation than products of conventional exfoliation methods. This new three-step exfoliation strategy is an easy way for obtaining high performance gC3N4 nanosheets for water purification.

Construction of a novel coordination polymer for selective fluorescence recognition and efficient adsorption of tryptophan in aqueous solution

The efficient separation and purification of L-tryptophan (L-Trp) from fermentation broth are essential for reducing production costs. Here, we report a new 1,1́-binaphthyl-based copper coordination polymer (R-Cu CP) that enables selective fluorescence recognition and efficient adsorption of L-Trp from aqueous solutions. A three-dimensional (3D) CP with a suitable cavity size (17 × 8 Å) was constructed by coordinating copper ions with the dicarboxylate ligand (R)-H3L derived from 1,1́-binaphthyl phosphoric acid. The prepared R-Cu CP exhibits extraordinary adsorption of L-Trp, up to 1055 mg/g. The specific fluorescence quenching response to L-Trp can be achieved by the ultrasonic exfoliation of two-dimensional (2D) CP nanosheets (CPNs). X-ray photoelectron spectroscopy and density functional theory calculations revealed that the efficient adsorption of L-Trp by R-Cu CP is due to the synergistic effect of coordination interactions, hydrogen bonding interactions, electrostatic interactions, and host–guest interactions, and the quenching mechanism is attributed to the photoinduced electron transfer from L-Trp to R-Cu CP and the competitive absorption of excitation energy by L-Trp.

Antimonene quantum dots as bifunctional fluorescent sensors for rapid detection of cation (Fe3+) and anions (CrO42−, Cr2O72−)

As an emerging bandgap material, antimonene quantum dots (AQDs) have attracted much attention due to their unique structure and outstanding physical and chemical properties. However, the research on the optical properties of AQDs is still in the initial stage and needs further exploration. Herein, the fluorescent AQDs were synthesized by ultrasonic liquid-phase exfoliation, combined with a hydrothermal treatment process. The as-prepared AQDs exhibit good fluorescence characteristics and have a fluorescence quantum yield value of 7.56%. Besides, the AQDs show good stability under different salt concentrations. Especially, the AQDs show high selectivity and rapid detection of Fe3+, CrO42−, and Cr2O72− ions in an aqueous solution with good anti-interference ability. The relatively low limit of detection for Fe3+ based on AQDs was 6.85 µM, and the limits of detection for CrO42−, and Cr2O72− were 23.0 and 5.91 µM, respectively. The mechanism for the fluorescence quenching of the AQDs can be attributed to the synergistic effect of the internal filter effect and the oxidation–reduction reaction between the AQDs and analytes. This work provided a simple synthesis method to easily prepare the AQDs with a larger yield, which can be applied to rapidly detect Fe3+ cation, and CrO42−, and Cr2O72− anions.

Bodipy-Based Metal-Organic Frameworks Transformed in Solid States from 1D Chains to 2D Layer Structures as Efficient Visible Light Heterogeneous Photocatalysts for Forging C-B and C-C Bonds.

Boron dipyrromethene (also known as bodipy), as a class of versatile and robust fluorophores and a structural analogue of porphyrins, has received a great deal of interests in the field of light-harvesting and energy-transfer processes. However, the fabrication of bodipy monomers into metal-organic frameworks (MOFs) and the exploitation of their potential still lags behind the porphyrin MOFs. In this work, two bodipy-based MOFs, BMOF 1D with 1D chain structure and BMOF 2D with 2D layer structure, were assembled by using dicarboxyl-functionalized bodipy ligands. BMOF 1D can also be converted to BMOF 2D by inserting additional ligands into BMOF 1D to cross-link the adjacent chains into the rhombic grid layer. During this process, spontaneous exfoliation occurred simultaneously and resulted in the formation of several hundred nanometer thickness BMOF 2D (nBMOF 2D), which can be further exfoliated into one-layer MOF nanosheets (BMON 2D) by using the ultrasonic liquid exfoliation method in a high yield. Featuring the distinct bodipy scaffolds in the porous frameworks, both BMOF 2D and BMON 2D displayed high reactivity and recyclability in the photocatalytic inverse hydroboration and cross-dehydrogenative coupling reactions to afford α-amino organoborons and α-amino amides in moderate to high yields. This work not only highlights the cascade utilization of ligand installation and ultrasonic liquid exfoliation methods to provide the single-layer MOF sheets in high yields but also advances the bodipy-based MOFs as a new type of heterogeneous photocatalysts in the forging of C-B and C-C bonds driven by visible light.

Preparation and Conductivity of Polymer-Modified Graphene Films

The Hummers method was used to make graphite oxide, and ultrasonic exfoliation at 25°C and 90°C was used to make graphene oxide (GO). At a low temperature, polyethyleneimine (PEI) was used as a reducing and changing agent for graphene oxide (GO) to make dispersions of graphene that were modified with PEI. Optoelectronics’ electron and infrared spectroscopy showed how temperature affected PEI’s ability to break down GO. The results show that PEI can partially reduce GO at 25°C. At 90°C, the grafted PEI gradually dissociated from the GO sheet. The graphene dispersion was filtered and assembled into a PEI-GO film, and its conductivity was found to be 117S.m-1, hopefully conductive material for graphene.

Ultrathin graphitic carbon nitride (g-C3N4) nanosheets: Synthesis, properties, and photocatalytic application

In recent years graphitic carbon nitride (g-C3N4) has been considered the most popular candidate for replacing graphene and other similar materials in various applications. The g-C3N4 has unique electronic and mechanical properties, huge photoluminescence in the wide optical region, and promising properties in energy conversion and storage, water splitting, etc. Here we show a simple method of bulk g-C3N4 (BCN) synthesis using thermal polymerization of melamine and ultrathin 2D g-C3N4 nanosheets (NCN) prepared by ultrasonic exfoliation of BCN in water. The g-C3N4 samples were tested with XRD, FTIR, Raman, luminescence spectroscopy, and N2 adsorption at 77 K. We characterize its photocatalytic properties in H2 evolution by direct water splitting. We utilize the low-cost 10 W white LEDs photoreactor with visible light and flow conditions. In the water-splitting reaction, we found that the NCN were about 5 times more reactive than the primary BCN sample.

Effects of green solvents and surfactants on the characteristics of few-layer graphene produced by dual-frequency ultrasonic liquid phase exfoliation technique

Nowadays, one of the promising methods for scalable graphene production is ultrasound-aided liquid phase exfoliation (ULPE) of graphite. Two current limiting factors of ULPE are the use of harmful solutions (such as N-Methyl-2-pyrrolidone or Dimethylformamide) and a relatively low graphene yield. In this study, we demonstrate a new dual frequency (20 kHz and 1174 kHz) ULPE approach in various eco-friendly media, which enabled us to produce various few-layer graphene (FLG) solutions of high quality. By implementing sophisticated characterisation techniques consisting of Raman spectroscopy, UV–vis spectroscopy and high-resolution electron microscopy, the final graphene flakes structure was confirmed to correlate the properties of each individual solution. The thinner (∼3 layers) and larger (∼1.5 μm2) flakes were observed while using just water, with the highest yield (11%) of smaller FLG flakes to be achieved in the mixture of water and a surfactant. In order to understand the cavitation mechanism in different solutions, the ULPE process was investigated by acoustic measurements. This study demonstrates the crucial role of ethanol (as a solvent) and surfactants as it regulates the cavitation power and intensity of the ultrasonic field and, thereby, the cavitation effectiveness. It is suggested that the mixture of water, ethanol and a surfactant is the best medium for ULPE process where a high yield of low-defective FLG flakes can be obtained in a solution stable at least for 3 months (around 80%).

Dextran-assisted ultrasonic exfoliation of two-dimensional metal-organic frameworks to evaluate acetylcholinesterase activity and inhibitor screening

Acetylcholinesterase (AChE) is regarded as a biomarker of Alzheimer's disease (AD), and its inhibitors show great potential in AD therapy as AChE can increase the neurotoxicity of the amyloid component that induces AD. Because of this, it is crucial and significant to develop a simple and highly sensitive strategy to monitor AChE levels and screen highly efficient AChE inhibitors. Herein, we synthesize an ultrathin two-dimensional (2D) metal-organic framework (MOF) based on copper-catecholate (Cu-CAT) via dextran assisted ultrasound exfoliation, followed by construction of a sensitive sensor for the monitoring AChE and screening of its inhibitors. By adding AChE, the acetylthiocholine (ATCh) substrate is hydrolyzed to be thiocholine (TCh), which decreases the peroxidase-like activity of Cu-CAT nanosheets (Cu-CAT NSs), impairing the signal reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) to oxidized-TMB (ox-TMB). In the presence of an AChE inhibitor, the signal can be gradually restored. The newly developed sensor shows high sensitivity and selectivity for AChE and huperzine A (HA, an effective drug for AD, an acetylcholine receptor antagonist), as well as for AD drug discovery from traditional Chinese herbs. The limit of detection of the sensor for AChE is 0.01 mU mL−1 and the average IC50 value of HA is 30.81 nM under the optimal of catalysis conditions. Compared with the 3D bulk Cu-CAT, the current 2D Cu-CAT NSs exhibit higher peroxidase activity due to more catalytic active site exposure. This study provides a strategy to prepare an ultrathin 2D MOF with high catalytic activity and new insights for the construction of a biosensor to monitor AChE and new AD drugs.

G-C3N4/polyvinyl alcohol-sodium alginate aerogel for removal of typical heterocyclic drugs from water

Heterocyclic drugs (HCDs) detected at high frequencies in wastewater have raised great concerns and their advanced removal has been the hotspot for safe water reuse in recent years. Two-dimensional graphitic carbon nitride (g-C3N4) and its photocatalytic systems are increasingly emerging, however, there are inevitable drawbacks of stacking and difficulty in recycling, resulting in decreased pollutant removal and limited application. Herein, for the first time, this paper reported a three-dimensional g-C3N4/polyvinyl alcohol-sodium alginate aerogel (g-C3N4/PVA-SA aerogel) photocatalyst synthesized by ultrasonic exfoliation and in-situ polymerization for typical HCDs (sulfadiazine (SDZ), sulfamethoxazole (SMX), and carbamazepine (CBZ)) removal in water. The reduced stacking of g-C3N4 dispersed in PVA-SA aerogel was achieved as revealed by scanning electron microscopy (SEM) and X-ray diffractometer (XRD) analysis, and g-C3N4/PVA-SA aerogel was observed to possess encouraging degradation efficiencies and rates for SDZ (100%, 0.0249 min−1), SMX (100%, 0.1762 min−1) and CBZ (69.8%, 0.0056 min−1), which were improved by 50%–60% and 133%–216% compared to those of g-C3N4, respectively. Meanwhile, environmental impact factors such as pH and coexisting ions had less impact on the degradation of SDZ and SMX by g-C3N4/PVA-SA aerogel. The novel aerogel also had a good recyclability, with less than 5% reduction in degradation efficiency after five cycles observed. The photodegradation of SDZ, SMX and CBZ was confirmed to be driven by ⋅O2− and h+ through scavenger-quenching experiments. The new low carbon and recyclable g-C3N4/PVA-SA aerogel reported in this study indicated a good potential for efficient removal of HCDs from water, which provides an alternative strategy for advanced purification and safe reuse of wastewater.

Preparation of boron nitride nanosheets by glucose-assisted ultrasonic cavitation exfoliation.

Boron nitride nanosheets (BNNSs) have been widely used in many fields due to their excellent properties. However, low preparation rates and difficulty in functionalization hinder their further development. This study proposes a novel glucose-assisted ultrasonic cavitation exfoliation (GAUCE) method with glucose as an auxiliary solution to prepare BNNSs. Results show that the method has a high preparation yield of 55.58%, which is higher than the average preparation yield of 33.86%. The mechanism of preparing BNNSs by GAUCE was also investigated. The exfoliation of BNNSs was achieved using the energy of ultrasonic cavitation bubble collapse, which will break the interlayer forces in h-BN. The grafting of hydroxyl groups decomposed by glucose on the edge and surface of BNNSs during cavitation prevented the re-aggregation of the nanosheets, thereby increasing the exfoliation yield of BNNSs. In addition, the contact angle of BNNSs prepared by GAUCE was reduced, and the hydrophilicity was greatly improved.

Piezoelectric-enhanced photocatalytic performance of porous carbon nitride nanosheets.

Through the utilisation of mechanical energy, piezocatalysis and piezophotocatalysis have emerged as promising strategies to tackle the current energy and environmental issues. In this work, porous graphitic carbon nitride (g-C3N4) nanosheets were synthesised via a novel self-templating process followed by ultrasonic exfoliation to produce materials with a thickness of 1.5-2nm and a high specific surface area of 59.48m2/g. Piezo-response force microscopy (PFM) indicated that the as-prepared porous g-C3N4 nanosheets show excellent piezoelectric response. Moreover, the porous g-C3N4 nanosheets exhibit remarkable piezophotocatalytic degradation of Rhodamine B (RhB), showing an optimal first-order rate constant (k=0.301min-1) under visible light and ultrasonic co-excitation, which was 2.3 times the value under visible light irradiation alone and 9.7 times the value under only ultrasonic excitation. A piezoelectric field generated by ultrasonic excitation drove photogenerated electrons and holes in opposite directions to migrate towards the surface of the nanosheets, resulting in the generation of more reactive radicals and thereby accelerating RhB degradation. By highlighting the potential of porous g-C3N4 nanosheets as a piezo-semiconductor for environmental remediation applications, this study paves the way for developing a new method for converting solar and mechanical energy via a piezo-mediation photocatalytic reaction.

Induced abundant oxygen vacancies in Sc2VO5-δ /g-C3N4 heterojunctions for enhanced photocatalytic degradation of levofloxacin.

Sc2VO5-δ /g-C3N4 heterojunctions (SVCs) with abundant oxygen vacancies (OVs) were synthesized by ultrasonic exfoliation combined with the thermal etching method. The structures, OVs and spatial separation of the photogenerated carriers were systematically characterized. The results manifested that the SVCs were successfully constructed via the strong interaction between g-C3N4 (CN) and Sc2VO5-δ (SV). The SVCs possessed a higher concentration of OVs than that of pristine CN and SV. The formation of the SVC heterostructures and the optimization of the OVs were the two major factors to accelerate the separation of the charge carriers and finally to improve the photocatalysis performance. The as-prepared 10%SVC (containing 10 wt% of SV) catalyst exhibited the highest OV concentration and the best photocatalytic performance. The levofloxacin (LVX) photodegradation activity showed a positive correlation with the OV concentration. The photocatalytic degradation efficiencies were 89.1, 98.8 and 99.0% on 10%SVC for LVX, methylene blue (MB) and rhodamine B (RhB), respectively. These photodegradation processes followed the pseudo first order kinetic equation. The apparent rate constant (k app) of LVX degradation on 10%SVC was 11.0 and 7.5 times that of CN and SV. The h+, ˙OH and ˙O2 - were the major reactive species in the photodegradation process.

An eco-friendly solution for liquid phase exfoliation of graphite under optimised ultrasonication conditions

Ultrasonic assisted liquid phase exfoliation (ULPE) is a promising method for the large scale production of 2D materials. Currently, toxic solvents such as N-Methyl-2-pyrrolidone (NMP) are commonly used for the production of graphene. In this paper four solvents; three green solvents (water, ethanol and water/ethanol) plus NMP for comparison, were sonicated and examined in terms of their bubble dynamics and acoustic emissions. Advanced fundamental analysis was conducted using high-speed imaging synchronised with acoustic pressure measurements complemented by shadowgraphic photography of the emitted shockwaves, in order to determine a suitable eco-friendly solvent medium from a cavitation bubbles dynamics perspective. Thereafter, ULPE of graphite in the optimum solvent took place for 2 h under controlled ultrasonication parameters. The produced graphene samples were characterised by employing a series of techniques consisting of Ultraviolet–visible (UV–Vis) and Raman spectroscopy as well as transmission electron microscopy (TEM). A mixture of deionised water and ethanol was shown to produce a yield twice that of pure water, comprising of high quality few layer graphene (3–5 Ls) with an average area of ∼1.15 (μm)2 and stability of ∼78% for the duration of six months. This combination is a promising eco-friendly substitute for future commercial manufacturing of graphene.

Ammonia Electrosynthesis with a Stable Metal-Free 2D Silicon Phosphide Catalyst.

Metal-free 2D phosphorus-based materials are emerging catalysts for ammonia (NH3 ) production through a sustainable electrochemical nitrogen reduction reaction route under ambient conditions. However, their efficiency and stability remain challenging due to the surface oxidization. Herein, a stable phosphorus-based electrocatalyst, silicon phosphide (SiP), is explored. Density functional theory calculations certify that the N2 activation can be realized on the zigzag Si sites with a dimeric end-on coordinated mode. Such sites also allow the subsequent protonation process via the alternating associative mechanism. As the proof-of-concept demonstration, both the crystalline and amorphous SiP nanosheets (denoted as C-SiP NSs and A-SiP NSs, respectively) are obtained through ultrasonic exfoliation processes, but only the crystalline one enables effective and stable electrocatalytic nitrogen reduction reaction, in terms of an NH3 yield rate of 16.12µgh-1 mgcat. -1 and a Faradaic efficiency of 22.48% at -0.3V versus reversible hydrogen electrode. The resistance to oxidization plays the decisive role in guaranteeing the NH3 electrosynthesis activity for C-SiP NSs. This surface stability endows C-SiP NSs with the capability to serve as appealing electrocatalysts for nitrogen reduction reactions and other promising applications.

Synthesis and Structure of ZnO-Decorated Graphitic Carbon Nitride (g-C3N4) with Improved Photocatalytic Activity under Visible Light

The volume of dye production in the chemical industry is growing rapidly every year. Given the global importance of clean water resources, new wastewater treatment solutions are required. Utilizing photocatalysis by harvesting solar energy represents a facile and promising solution for removing dangerous pollutants. This study reports the possibility of increasing the photocatalytic activity of g-C3N4 by creating nanocomposites with ZnO. Exfoliated g-C3N4/ZnO nanocomposites were synthesized by heat treatment of urea and subsequent ultrasonic exfoliation of the colloidal solution by introducing zinc acetate. The uniformity of the distribution of ZnO nanoparticles is confirmed by the method of elemental mapping. The obtained X-ray diffractograms of the obtained nanocomposites show typical X-ray reflections for g-C3N4 and ZnO. It was found that the introduction of oxide into g-C3N4 leads to an increase in the specific surface area values due to the developed ZnO surface. The maximum value of the specific surface area was obtained for a sample containing 7.5% ZnO and was 75.2 m2/g. The g-C3N4/7.5% ZnO sample also demonstrated increased photocatalytic activity during the decomposition of methylene blue under the influence of visible light, which led to a twofold increase in the reaction rate compared to initial g-C3N4.

Sulfonated cobalt phthalocyanine-stabilized graphene: Ultrasonic exfoliation and application in anticorrosion of aluminum

Aqueous phase exfoliation (APE) has become a promising method of the graphene preparation. However, it still has some disadvantages, such as low yield and the influence of residual stabilizer on its application. Herein we report a method of the graphene preparation via APE of graphite assisted by sulfonated cobalt phthalocyanine (CoPcS) as the stabilizer. A high yield of graphene can be obtained at low concentration of CoPcS. The yield was 3.2 % in single exploitation, and the total yield reached to 7.3 % after three cycles of exfoliation. The sizes of the prepared graphene sheets were in micron level, and the percentage of few-layer graphene (<5) reached 93 %. The π-π interaction of graphene with CoPcS, as well as the repulsive interaction between negatively charged CoPcS ions, played a crucial role in stabilizing the graphene dispersion. The as-exfoliated graphene powder served directly as a filler in the epoxy coating on the surface of aluminum to improve the protection performance of the coating. A simple, cost-effective, and potential avenue has been provided to product and utilize high-quality graphene materials.

Synthesis and Investigation of Reduced Graphene Oxide - Sulfur Composite Electrode for Lithium-Sulfur Battery

Lithium sulfur (Li-S) batteries have become one of the promising rechargeable storage devices due to its abundancy, low cost, non-toxicity, environmental friendliness and high theoretical specific capacity. However, the insulating nature of sulfur and the shuttling effect of polysulfides have limited their applications. In order to alleviate these problems and make Li-S batteries more promising, we have synthesized a composite of reduced graphene oxide and sulfur (rGO-S) as electrode material for these batteries. In this paper, graphite oxide was prepared from graphite powder by Improved Hummer’s method followed by ultrasonic exfoliation to make Graphene Oxide (GO). The GO suspension was hydrothermally reduced and heated in a hot air oven at 150 °C for 4 hours followed by the addition of sulfur (S) in a ratio of 0.1:1 and 1:1 by mass and heated again at 180 °C for another 4 hours to make a composite of rGO-S. The electrode of the rGO-S composite was prepared by making a slurry of active material, carbon black and polyvinylidene fluoride (PVDF). The sample of GO and rGO were analyzed using Ultraviolet (UV)-Visible and Fourier Transform Infrared (FTIR) spectroscopy. The composite material was analyzed using X-Rays Powder Diffraction (XRD) while the energy density and charge discharge curves of the electrode were analyzed using cyclic voltammetry (CV).

Highly enhanced thermal conductivity from boron nitride nanosheets and MXene phonon resonance in 3D PMMA spheres composites

Efficient thermal management materials are important for the proper operation of integrated circuits. In this work, the high-yield preparation of hydroxylated boron nitride nanosheets (BNNSs) was achieved by high-temperature ablation followed by ultrasonic exfoliation without the use of highly toxic solvents. The small-sized BNNSs have similar phonon vibration properties as the large-sized MXene, and they self-assemble by electrostatic adsorption on PMMA particles to form hybrid spheres. The appearance of thermal percolation threshold indicates the successful construction of thermal conductivity pathway. The exclusion effect is more pronounced for PMMA microspheres with a larger radius, and the best thermal conductivity of 4.13 W/m·K was achieved for the composite with 20 wt% nanosheet filling. The composite exhibited good thermal performance both in the finite element model and when used as an LED heat sink. Furthermore, the incorporation of fillers can also effectively improve the thermal stability and mechanical properties of the composite. Our study provides a facile and environmental exfoliation approach of h-BN and a new strategy for the preparation of high thermal conductivity electronic packaging materials.

Phosphorene nanosheet decorated graphitic carbon nitride nanofiber for photoelectrochemically enhanced hydrogen evolution from water splitting

BackgroundPhosphorene nanosheet is a p-type semiconductor with excellent optoelectronic property and large surface area, while graphitic carbon nitride (g-C3N4) nanofiber is a n-type visible-light-driven photocatalyst. The fabrication of p-n heterostructured nanocomposites for hydrogen evolution from water splitting via photoelectrochemistry is an exceptionally promising technique. MethodPhosphorene and g-C3N4 were prepared by electrospinning and ultrasonic exfoliation procedures, respectively, and then mixed physically by Van deer Waal force to form the p-n heterojunction. The photoelectrochemical hydrogen evolution from water splitting was performed under solar light irradiation. Significant findingsThe morphological analysis show that 100–200 nm phosphorene nanosheets are successfully decorated on 450-nm g-C3N4 nanofibers. After adding 4–18 wt% phosphorene onto g-C3N4 nanofiber (P/CN), the specific surface area of P/CN nanocomposites is in the range of 52.1–68.3 m2 g−1. The addition of 13 wt% phosphorene is optimal for P/CN nanocomposite to maximize the hydrogen evolution rate of 2,208 μmol h−1 g−1 by accelerating the electron transfer to enhance the PEC performance in P/CN heterostructure under illumination. Results have signified that the metal-free P/CN photocatalyst can provide an effective solar-light-responsive capability toward water splitting, which can create a promising strategy to fabricate low-dimensional electrode materials for a wide variety of water-energy nexus and green energy applications.