Few-layer Black Phosphorus Nanosheets Research Articles

Electrosynthesis of an Improbable Directly Bonded Phosphorene-Fullerene Heterodimensional Hybrid toward Boosted Photocatalytic Hydrogen Evolution.

Phosphorene and fullerene are representative two-dimensional (2D) and zero-dimensional (0D) nanomaterials respectively, constructing their heterodimensional hybrid not only complements their physiochemical properties but also extends their applications via synergistic interactions. This is however challenging because of their diversities in dimension and chemical reactivity, and theoretical studies predicted that it is improbable to directly bond C60 onto the surface of phosphorene due to their strong repulsion. Here, we develop a facile electrosynthesis method to synthesize the first phosphorene-fullerene hybrid featuring fullerene surface bonding via P-C bonds. Few-layer black phosphorus nanosheets (BPNSs) obtained from electrochemical exfoliation react with C60 2- dianion prepared by electroreduction of C60, fulfilling formation of the "improbable" phosphorene-fullerene hybrid (BPNS-s-C60). Theoretical results reveal that the energy barrier for formation of [BPNS-s-C60]2- intermediate is significantly decreased by 1.88 eV, followed by an oxidization reaction to generate neutral BPNS-s-C60 hybrid. Surface bonding of C60 molecules not only improves significantly the ambient stability of BPNSs, but also boosts dramatically the visible light and near-infrared (NIR) photocatalytic hydrogen evolution rates, reaching 1466 and 1039 μmol h-1 g-1 respectively, which are both the highest values among all reported BP-based metal-free photocatalysts.

Enhancing the efficient degradation of BPS using the BPNS-CdS composite catalyst under visible light

Black phosphorus nanosheets (BPNS), a novel two-dimensional nanomaterial, find extensive applications in the field of photocatalysis. With the prohibition of bisphenol A (BPA), the utilization of bisphenol S (BPS), which is more resistant to degradation than BPA, has been steadily increasing. In this study, few-layer BPNS was prepared using an improved liquid-phase exfoliation method, showcasing its commendable specific surface area and notable adsorption capacity. Subsequently, a new type of nanocomposite material, BPNS-Cadmium sulfide (CdS), was hydrothermal synthesized involving BPNS and CdS. We conducted comparative assessments of BPNS, CdS, and their composite materials to identify the most efficient catalysts. Ultimately, we found that the composite material BPNS-CdS exhibited the highest capability for degrading BPS in an alkaline environment, achieving an impressive degradation rate of 86.9%. Notably, the degradation rate remained higher in an acidic environment compared to a neutral one. Through Electron Spin Resoance (ESR) experiments, it is revealed that BPNS-CdS, when exposed to visible light, generates •O2−, •OH, and h+ as confirmed. Additionally, we tested and validated the carrier separation and migration abilities of BPNS-CdS while also calculating the band gap for each material. Building upon these results, a possible photocatalysis mechanism experiment was proposed. Finally, the degradation products were analyzed using High-Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS) and put forth a plausible pathway for the BPS degradation, and it was found that 4-Phenolsulfonic acid, Ethyl protocatechuate and Isophthalic acid are the main intermediates of BPS. This study contributes to a deeper understanding of the synergy between non-metallic catalysts like BPNS and metal catalysts like CdS. It also offers new insights into the degradation mechanisms and pathways for BPS.

Edge-selective covalent passivation of black phosphorus nanosheets by fullerene C70 toward enhanced antimicrobial performance

In the fight against bacterial infection, conventional antibiotic treatment encounters the formidable challenges of drug resistance and sluggish development. Non-metallic two-dimensional (2D) nanomaterials such as black phosphorus (BP) have emerged as promising non-antibiotic antimicrobial candidates due to its peculiar physiochemical properties, but face hurdles including low ambient stability and limited antibacterial activity, hindering its widespread utilization in disinfection. Herein, few-layer BP nanosheets (BPNSs) were covalently passivated by edge-selectively grafting fullerene C70 via a one-step solid-state mechanochemical route, and for the first time the covalently functionalized BPNSs is employed in disinfection. Fullerene edge-selective covalent passivation not only effectively overcomes the obstacles of poor ambient stability, but also substantially enhances the antibacterial activities of BPNSs. The BPNSs-C70 hybrid (denoted as BPNSs-C70) was applied as a novel non-metallic and non-antibiotic nano-antibacterial agent. Under 660 nm visible light irradiation, BPNSs-C70 demonstrates high generation capacity of reactive oxygen species (ROS), resulting in boosted in vitro and in vivo antibacterial efficacies against methicillin-resistant Staphylococcus aureus (MRSA) relative to the pristine BPNSs with exceptional biocompatibility. The significantly enhanced antibacterial performance of BPNSs-C70 is attributed to the synergistically improved singlet oxygen (1O2) and hydroxyl radicals (•OH) generation originated from the intramolecular electron transfer from BPNSs to C70.

Charge transfer interfaces across black phosphorus/Co, N Co-doped carbon heterojunction for enhanced electrocatalytic water splitting

The practicality of electrochemical water-splitting technology relies on the development of novel and efficient bifunctional electrocatalysts capable of facilitating both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Black phosphorus (BP) holds tremendous promise for HER and OER electrocatalysis owing to its fully exposed atoms and high carrier mobility. However, the electrocatalytic performance of BP is still much lower than the expected theoretical limit, presenting an exciting challenge for further advancements. Herein, we embed electrochemically exfoliated few-layer BP nanosheets in higher Fermi level (EF) of cobalt, nitrogen co-doped carbons to form a new heterojunction (CoNC-BP), as efficient bifunctional electrocatalysts toward HER and OER for the advancement overall water splitting applications. A directed interfacial electron transfer is realized from CoNC to BP, facilitated by the lowering Fermi level (EF). This interfacial electron transfer plays a crucial role in optimizing the adsorption and desorption of active intermediates, while also introducing an abundance of hypervalent Co sites. These factors collectively contribute to the remarkable electrocatalytic activities of HER and OER performance, leading to the efficient performance of the developed CoNC-BP heterojunction in water-splitting applications. This work demonstrates a promising breakthrough that can inspire the design of high-efficiency catalysts.

Fullerene Covalent Passivation of Black Phosphorus Nanosheets toward Enhanced Near-Infrared-II Photothermal Therapy

Photothermal therapy (PTT) triggered by near-infrared-II (NIR-II, 1000-1700 nm) light is developed as a potential tumor therapy technique with deeper tissue penetration capacity and higher allowable laser power density of the skin than NIR-I (750-1000 nm) biowindow. Black phosphorus (BP) with excellent biocompatibility and favorable biodegradability demonstrates promising applications in PTT but suffers from low ambient stability and limited photothermal conversion efficiency (PCE), and utilization of BP in NIR-II PTT is scarcely reported. Herein, we develop novel fullerene covalently modified few-layer BP nanosheets (BPNSs) with ∼9-layer thickness through an easy one-step esterification process (abbreviated BP-ester-C60), bringing about the dramatically enhanced ambient stability of BPNSs due to bonding of the hydrophobic C60 with high stability and the lone electron pair on the phosphorus atom. BP-ester-C60 is then applied as a photosensitizer in NIR-II PTT, delivering a much higher PCE than the pristine BPNSs. Under 1064 nm NIR-II laser irradiation, in vitro and in vivo antitumor studies reveal that BP-ester-C60 exhibits dramatically enhanced PTT efficacy with considerable biosafety relative to the pristine BPNSs. This is interpreted by the boost of NIR light absorption on account of the modulation of the band energy level resulting from intramolecular electron transfer from BPNSs to C60.

A Spear and Shield-Inspired Ar Plasma Safeguard Few-Layer Black Phosphore with Firefighting of Epoxy Resin.

Appearing as an innovative and efficient strategy, a facile strategy of a plasma ball mill is carried out to prepare few-layer black phosphorus nanosheets (BPNSs), for abating the fire risk of epoxy resin (EP). A spear and shield-inspired Ar plasma emergeed through a plasma ball mill to prevent Ar@BP nanosheets from oxidation compared with the preparation of BP nanosheets (MBPNSs) in a mechanical ball mill. The absorption coefficient in the synchrotron radiation spectrum is increased by 16.91%, indicating that BP is effectively protected by Ar proof. The Vienna ab initio simulation reveals that the combination of Ar@BP with oxygen cannot proceed spontaneously with the binding energy of 4.44eV. With the introduction of 1.5 wt% Ar@BP, the total heat release (THR), total smoke release (TSR), total smoke production(TSP), CO, and CO2 yield, compared with that of EP, are descended by 30.40%, 24.41%, 24.10%, 33.23%, and 37.60%, respectively, indicating excellent flame retardancy property. It is attributed to the condensed and gas phase function. Meanwhile, the tensile strength and elongation at break increase by 27.92% and 56.04%, respectively, with the incorporation of 1.5 wt% Ar@BP.

Rational design and construction of novel hierarchical Au/BPNSs/ZnIn2S4 heterojunction photocatalyst for enhancing photocatalytic H2 production under visible light

A novel hierarchical Au/black phosphorus nanosheets/ZnIn2S4 (Au/BPNSs/ZIS) heterojunction photocatalyst has been successfully synthesized in this work, in which ZnIn2S4 (ZIS) nanosheets were first grown in situ on black phosphorus nanosheets (BPNSs) using the solvothermal method. Au nanoparticles were then photo-deposited on the outer surface of the ZIS. The hydrogen evolution rate of the optimal Au/BPNSs/ZIS is 1674 μmol·h−1·g−1, which is 5 and 17 times higher than that of pure ZIS and few-layer BPNSs, respectively. The photocatalyst of BPNSs/ZIS is primarily attributed to the formation of Zn-P bonds between them to stabilize the connection of BPNSs/ZIS heterojunctions, according to X-ray photoelectron spectroscopy (XPS). At the same time, the work function calculation reveals that the interface electric field formed from ZIS to BPNSs is the driving force of interface charge transfer, allowing photoexcited electrons to migrate directionally on the interface and improve hydrogen evolution efficiency under visible light irradiation. Furthermore, Au nanoparticles are photo-deposited on the ZIS surface to form Schottky junctions, which improves photocatalytic performance even further. This work offers a novel approach to developing BP-based heterojunctions in photocatalysis.

Electrochemically exfoliated phosphorene nanosheet thin films for wafer-scale near-infrared phototransistor array

Two-dimensional (2D) black phosphorus (BP), or phosphorene, has recently emerged as a promising 2D semiconductor because of its p-type charge transport behavior and near-infrared photoresponsivity. However, the application of BP in practical electronic and optoelectronic devices is hindered by challenges in producing high-quality BP films over large areas. In this manuscript, we present a facile solution-based process to create wafer-scale BP films for fabrication of p-channel field-effect transistors that are responsive to near infrared light. Few-layer BP nanosheets are first exfoliated from the bulk crystal via electrochemical intercalation of cationic molecules and then vacuum-filtered through an anodic aluminum oxide membrane. The resulting BP film can be transferred onto an SiO2-coated silicon substrate, thereby allowing for realization of field-effect transistors after electrode deposition and thermal annealing. The transistor array exhibits spatial uniformity in electrical performance with an average hole mobility of ~0.002 cm2 V−1 s−1 and on/off ratio of 130. Furthermore, gate-induced modulation of the BP channel allows for enhancement in the photoresponsivity for 1550-nm light illumination up to 24 mA W−1, which benefits the application of the phototransistor array for near infrared imaging.

Innovative design of hierarchical cobalt-based borate functionalized black phosphorus structure with petal-like wrinkle: Enhancing the fire safety and mechanical properties of epoxy resin

The weak anti-oxidation and smoke-suppression abilities limit the use of black phosphorus (BP) in the preparation of high-performance flame-retardant epoxy resin (EP) composites. Here, aromatic diazonium chemistry was used to graft phenylboronic acid on the surface of few-layer BP nanosheets (BPNSs) to obtain passivated BP-based nanomaterials (BP-DPBA). Then, a novel multifunctional nano flame retardant [email protected] was obtained by anchoring amorphous cobalt-based borate (Co-BO) on the surface of BP-DPBA through a low-temperature reduction reaction. Subsequently, [email protected] was incorporated into EP matrix in the form of nanofillers and formed a mechanically enhanced system. As expected, EP nanocomposites containing 2 wt% [email protected] achieves greatly improvements in thermal stability and fire safety, with 93% increase in char yield (CY) during pyrolysis, 48.4% and 41.7% decrease in peak heat release rate (PHRR) and total heat release (THR) during combustion respectively, a limiting oxygen index (LOI) value up to 32.5% and a UL94 rating of V0. In addition, the presence of Co-BO greatly improves the ability of BP to suppress toxic smoke. Specifically, EP/[email protected] 2.0 achieves a 25.4% reduction in total smoke production (TSP) during combustion. In particular, the maximum 36.2% and 73.2% increases are achieved in storage modulus and impact strength, respectively, confirming that [email protected] can effectively enhance the mechanical properties of EP. Therefore, this work provides a feasible solution for loading high-valence metal compounds on the surface of BPNSs, and prepared high-performance EP nanocomposites with enhanced fire safety and mechanical properties.

One-step co-precipitation method to construct SnO quantum dots modified black phosphorus nanosheets for room-temperature trace NH3 sensing

Black phosphorus (BP) which was an appealing two-dimensional (2D) material, had gained considerable recognition in gas sensing due to its large specific surface area, high carrier mobility and small out-plane conductivity, however, most existing studies were focused on the detection of the humidity and strongly oxidizing NOx gas. As a excellent gas sensing material, BP should have great potential in universal gas sensors. To overcome these constraints, this report proposed modifying few-layer BP nanosheets with SnO quantum dots (QDs) to detect trace NH3 at room temperature (25 °C). Compared with the BP sensor, the proposed BP-SnO-4 sensor demonstrated a significant response to 10 ppm NH3 (3.3 vs 0.8, which was among the best-reported case of BP-involving NH3 detection). The theoretical detection limit was as low as 0.8 ppt, demonstrating the considerable potential of the BP-SnO-4 sensor in the detection of NH3. The constituent ratio-optimized BP-SnO sensors exhibited higher response, less baseline drift and stronger long-term stability when compared with pure BP counterparts. Specific adsorption sites, numerous p-n BP-SnO heterojunctions and SnO nanoparticles involved passivation were primarily responsible for these improvements. This work revealed improved NH3 sensing of BP nanosheets through the incorporation of SnO QDs, thus enriching the alternative strategies of developing universal BP-based gas sensors.

High-Performance TPE-S Modified by a Flame-Retardant System Based on Black Phosphorus Nanosheets.

Few-layer black phosphorus nanosheets (BPs) combined with melamine cyanurate and poly(phenylene oxide) were used to prepare a flame-retardant thermoplastic elastomer based on polystyrene (TPE-S) for the first time. Compared with neat TPE-S, BP-modified TPE-S with a phosphorus content of 7.98% (TPE-S/BP-7.98) passed the UL-94 vertical burning V-0 rating, and the limiting oxygen index value increased to 24.0%. The peak heat release rate (PHRR), total heat release, and the average combustion effective heat of TPE-S/BP-7.98 were decreased by 61.8, 26.0, and 35.3%, respectively. The time to PHRR was increased from 90 s (neat TPE-S) to 170 s. Scanning electron microscopy of frozen fracture sections showed favorable compatibility and dispersibility of BPs in TPE-S. In addition, the introduction of BPs showed the most negligible effect on the mechanical properties of TPE-S compared with other flame retardants (aluminum hypophosphite and red phosphorus).

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation.

The development of long-wavelength photoinduced copper-catalyzed azide–alkyne click (CuAAC) reaction routes is attractive for organic and polymer chemistry. In this study, we present a novel synthetic methodology for the photoinduced CuAAC reaction utilizing exfoliated two-dimensional (2D) few-layer black phosphorus nanosheets (BPNs) as photocatalysts under white LED and near-IR (NIR) light irradiation. Upon irradiation, BPNs generated excited electrons and holes on its conduction (CB) and valence band (VB), respectively. The excited electrons thus formed were then transferred to the CuII ions to produce active CuI catalysts. The ability of BPNs to initiate the CuAAC reaction was investigated by studying the reaction between various low molar mass alkyne and azide derivatives under both white LED and NIR light irradiation. Due to its deeper penetration of NIR light, the possibility of synthesizing different macromolecular structures such as functional polymers, cross-linked networks and block copolymer has also been demonstrated. The structural and molecular properties of the intermediates and final products were evaluated by spectral and chromatographic analyses.

Surface Functionalization of Black Phosphorus with Nitrenes: Identification of P=N Bonds by Using Isotopic Labeling

Surface functionalization of two-dimensional crystals is a key path to tuning their intrinsic physical and chemical properties. However, synthetic protocols and experimental strategies to directly probe chemical bonding in modified surfaces are scarce. Introduced herein is a mild, surface-specific protocol for the surface functionalization of few-layer black phosphorus nanosheets using a family of photolytically generated nitrenes (RN) from the corresponding azides. By embedding spectroscopic tags in the organic backbone, a multitude of characterization techniques are employed to investigate in detail the chemical structure of the modified nanosheets, including vibrational, X-ray photoelectron, solid state 31 P NMR, and UV-vis spectroscopy. To directly probe the functional groups introduced on the surface, R fragments were selected such that in conjunction with vibrational spectroscopy, 15 N-labeling experiments, and DFT methods, diagnostic P=N vibrational modes indicative of iminophosphorane units on the nanosheet surface could be conclusively identified.

(Invited) Laser-Assisted Exfoliation of Black Phosphorus with Thickness Control for Li-Ion Batteries

Few-layer black phosphorus (BP) is an emerging two-dimensional (2D) material with exciting properties such as tunable bandgap and high charge carrier mobility, which make it a suitable candidate for energy storage applications. However, its preparation remains challenging. Currently, the exfoliation of bulk crystal to its few-layer form assisted by liquid-phase exfoliation (LPE) process using ultrasonic agitation is commonly adopted, which is time-consuming and suffers low efficiency and lack of morphologic control. In this study, we demonstrate a highly-efficient route for the scalable production few-layer BP nanosheets using a pulsed laser in low-boiling point solvents. By adjusting the laser irradiation time and solvent type, the morphology (layer number and lateral size) of the few-layer BP nanosheets is tuned with a narrow distribution (layer number from 3 to 13, lateral size from <2 µm to >5 µm). The laser-assisted exfoliation is understood by a plasma quenching mechanism and interlayer interaction weakened by the in situ generated vapor bubbles. The fine control of thickness and lateral size of the BP nanosheets enables us to study their impact on Li-ion battery performance when applied as anode material. We present herein the correlation of the layer number and larger lateral size of BP with the electronic conductivity, Li+ ion transfer rate and diffusivity, as well as long-term cyclability, revealing the morphology-dependent battery performance. Figure 1

Room-Temperature and Humidity-Resistant Trace Nitrogen Dioxide Sensing of Few-Layer Black Phosphorus Nanosheet by Incorporating Zinc Oxide Nanowire.

Surmounting the issues of high-sensitivity and room-temperature detection toward trace NO2 gas is of paramount importance in the fields of human health and ultralow emission. Recently, black phosphorus (BP), a novel two-dimensional material, has gained considerable interest to achieve this goal. However, related work is far from satisfactory due to sluggish response, insufficient recovery, and fragile stability. In this scenario, we report on an inspiring NO2 sensor featuring composite film of few-layer BP nanosheets and zinc oxide (ZnO) nanowires serving as the sensing layer. Compared with BP-only counterpart, BP-ZnO sensor exhibited enhanced performance including boosted response (74% vs. 37.7% toward 50 ppb, which was among the best performances of BP involved NO2 sensors), accelerated response speed, better long-term stability, and strengthened humidity-repelling properties. In addition, excellent selectivity toward trace NO2 gas was revealed. These improvements could be ascribed into porous film, abundant sorption sites, numerous p-n heterojunctions, and passivation effect of ZnO nanowires on BP nanosheets. Furthermore, the proposed basic-solution assisted BP exfoliation favored film deposition, and enabled versatile composition design involving BP nanosheets in the future. In brief, the as-prepared BP-ZnO NO2 sensors paved the avenue for further BP applications and enriched its underlying transduction mechanism in gas sensing.

Construction of hierarchical functionalized black phosphorus with polydopamine: A novel strategy for enhancing flame retardancy and mechanical properties of polyvinyl alcohol

As a rising star of two-dimensional (2D) materials, single or few-layer black phosphorus (BP) possess great potential as nanofiller in fabricating polymer nanocomposites, due to its thermodynamic stability, nano-size effect and structural characteristics. Herein, few-layer BP nanosheets were scalable exfoliated via solvent-thermal method, the Lithium ion intercalation was achieved during this procedure. Follow by a polydopamine (PDA) encapsulated BP sandwich nanostructure was developed by oxidation–reduction strategy, which improved the air stability of few-layer BP and its interfacial compatibility with polymer matrix. As could be expected, the PDA encapsulated BP (BP-PDA) can effectively enhance the mechanical properties and flame retardancy of polyvinylalcohol (PVA) nanocomposite films. For instance, the PVA/BP-PDA5.0 nanocomposite film loaded with 5 wt% BP-PDA exhibited 57.2% maximum decrease in peak heat release rate and 47.9% maximum reduction in total heat release. Meanwhile, while the BP-PDA loading achieved 2 wt%, PVA/BP-PDA2.0 nanocomposite film revealed an 81.1% increase in the tensile strength. In particular, onaccountofdual protection of the PDA encapsulation and polymer matrix embedding, the air stability of BP in PVA matrix was significantly improved. As an evidence, the ratio of Ag1/Ag2 in Raman spectra of BP-PDA decreased from the initial 0.72 to 0.62, even after exposed to air for five months, indicating a low level of oxidation. This work provides a novel strategy for scalable exfoliation and functionalization of BP, and enables a wide range of potential applications of BP in polymer nanocomposites.

Improving room-temperature trace NO2 sensing of black phosphorus nanosheets by incorporating benzyl viologen

Black phosphorus (BP), an appealing two-dimensional (2D) material, has attracted considerable attention in gas sensing by virtue of large specific surface area, high carrier mobility and small out-plane conductivity, but undesirably hindered by incomplete recovery and fragile reproducibility especially toward strongly oxidizing NO2 gas. To overcome these limitations, in this report we attempt to incorporate benzyl viologen (BV) with few-layer BP nanosheets to detect trace NO2 at room temperature (20 °C). Compared with BP sensor, BP-BV one showed superior recovery characteristics, repeatability, selectivity and humidity-repelling features. In addition, the sensor response remained quite large and nearly unchanged after BV incorporation (-33 % for BP-BV-1 sensor vs. -32 % for BP counterpart toward 50 ppb NO2, which was among the best cases of BP-involving NO2 detection). Herein, BP layers not only interacted with NO2 gas but also transported electrons. BV mainly played dual roles in the composites during sensing tests. On the one hand, BV offered additional electrons to NO2 gas to compensate for NO2 adsorption loss arising from BV-induced partial covering of some high-energy sorption sites on BP nanosheets. On the other hand, BV effectively passivated BP through occupying these sites, thus maintaining a reversible recovery and a repeatable response. This work revealed an improved NO2 sensing of BP nanosheets by incorporating BV material of optimal content, enriching the alternative strategies for reversible and sensitive operation of novel BP-related sensors.

Few-layer black phosphorus and boron-doped graphene based heteroelectrocatalyst for enhanced hydrogen evolution

Efficient heterostructured electrocatalysts based on two-dimensional few-layer black phosphorus nanosheets and boron-doped graphene are designed for the hydrogen evolution reaction.

Electrochemically Exfoliated Functionalized Black Phosphorene and Its Polyurethane Acrylate Nanocomposites: Synthesis and Applications.

Owing to its mechanical performance, thermal stability, and size effects, single or few-layer black phosphorus (BP) has the potential to prepare the polymer nanocomposites as a candidate of nanoadditives, similar to graphene. The step to realize the scalable exfoliation of single or few-layer BP nanosheets is crucial to BP applications. Herein, we utilized a facile, green, and scalable electrochemical strategy for generating cobaltous phytate-functionalized BP nanosheets (BP-EC-Exf) wherein the BP crystal served as the cathode and phytic acid served as a modifier and an electrolyte simultaneously. Moreover, high-performance polyurethane acrylate/BP-EC-Exf (PUA/BP-EC) nanocomposites are easily prepared by a convenient UV-curable strategy for the first time. Significantly, the conclusion of introducing BP-EC-Exf into the PUA matrix resulted in enhancement in mechanical properties of PUA in terms of the tensile strength (increased by 59.8%) and tensile fracture strain (increased by 88.1%), in the distinct improvement in flame retardancy of PUA in terms of the decreased peak heat release rate (reduced by 44.5%) and total heat release (decreased by 34.5%), and in lower intensities of pyrolysis products including toxic CO. Moreover, it was confirmed by X-ray diffraction and Raman spectra that the air stability of PUA/BP-EC nanocomposites was maintained after exposure to environmental conditions for 4 months. The air-stable BP nanosheets, which were wrapped and embedded in the PUA matrix, can achieve the isolation and protection effect. This modified electrochemical method toward the simultaneous exfoliation and functionalization of BP nanosheets provides an efficient approach for fabricating BP-polymer-based nanocomposites.

Ammonia Synthesis Under Ambient Conditions: Selective Electroreduction of Dinitrogen to Ammonia on Black Phosphorus Nanosheets.

Constructing efficient catalysts for the N2 reduction reaction (NRR) is a major challenge for artificial nitrogen fixation under ambient conditions. Herein, inspired by the principle of "like dissolves like", it is demonstrated that a member of the nitrogen family, well-exfoliated few-layer black phosphorus nanosheets (FL-BP NSs), can be used as an efficient nonmetallic catalyst for electrochemical nitrogen reduction. The catalyst can achieve a high ammonia yield of 31.37 μg h-1 mg-1 cat. under ambient conditions. Density functional theory calculations reveal that the active orbital and electrons of zigzag and diff-zigzag type edges of FL-BP NSs enable selective electrocatalysis of N2 to NH3 via an alternating hydrogenation pathway. This work proves the feasibility of using a nonmetallic simple substance as a nitrogen-fixing catalyst and thus opening a new avenue towards the development of more efficient metal-free catalysts.