The Art of Constructing Black Phosphorus Nanosheet Based Heterostructures: From 2D to 3D

Pt nanoparticles anchored by oxygen vacancies in MXenes for efficient electrocatalytic hydrogen evolution reaction

The improvement of the hydrogen evolution reaction (HER) performance of nanomaterials is associated with the interfacial synergistic interaction and their hydrogen adsorption kinetics. Nevertheless, it is still a challenge to accelerate the proton transfer and optimize the HER kinetics by constructing Pt-supported heterostructures based on the hydrogen spillover phenomenon. Herein, oxygen vacancies on the surface of MXene nanosheets were constructed via a high-temperature annealing method, which was employed to anchor/stabilize Pt nanoparticles and fabricate a Pt/MXene heterostructure. EPR and XPS analyses verified the presence of oxygen vacancies, which could enhance the intrinsic HER activity of the MXene. The HER catalytic performance was investigated by taking into account the surface structure of the MXene affected by the annealing temperature, the concentration of Pt and the number of deposition cycles. Electrochemical results showed that Pt/MXene with higher utilization of Pt was obtained at 900 °C and 0.05 mgPt mL-1. The 0.05-Pt/MXene-900 obtained at deposition of 60 cycles in 0.5 M H2SO4 solution exhibited the optimized HER activity. The overpotential was 22 mV at a current density of 10 mA cm-2 and the Tafel slope was 42.41 mV dec-1. Furthermore, the accelerated HER kinetics was mainly due to the electron trapping ability of the MXene, small particles of Pt, as well as the enhanced charge transfer between the oxygen vacancies of the MXene and Pt. This strategy for constructing Pt-supported heterostructures based on the vacancy anchoring effects provides new ideas for the design of well-defined electrocatalysts toward the HER.

Stabilizing electron-rich Ni single-atoms on black phosphorus nanosheets boosts photocatalytic carbon dioxide reduction

The development of unique single-atom catalysts with electron-rich feature is essential to promoting the photocatalytic CO2 reduction, yet remains a big challenge. Here, a conceptionally new single-atom catalyst constructed from atomically dispersed Ni-P3 species on black phosphorus (BP) nanosheets (BP-Ni) is synthesized for realizing highly efficient visible-light-driven CO2 reduction when trapping photogenerated electrons from homogeneous light absorbers in the presence of triethanolamine as the sacrificial agent. Both the experimental and theoretical calculation data reveal that the Ni-P3 species on BP nanosheets own the electron-rich feature that can improve the photogenerated charge separation efficiency and lower the activation barrier of CO2 conversion. This unique feature makes BP-Ni exhibit the much higher activity as cocatalyst in the photocatalytic CO2 reduction than BP nanosheets. The BP-Ni can also be applied as a cocatalyst for enhanced photocatalytic CO2 reduction after combining with CdSe/S colloidal crystal photocatalyst. The present study offers valuable inspirations for the design and construction of effective catalytic sites toward photocatalytic CO2 reduction reactions.

Study on synergistic effects of 4f levels of erbium and black phosphorus/SnNb2O6 heterostructure catalysts by multiple spectroscopic analysis techniques

Lanthanide single atom modified catalysts are rarely reported because the roles of lanthanide in photocatalysis are difficult to explain clearly. Based on the construction of Er single atom modified black phosphorus/SnNb2O6 (BP/SNO) heterojunctions, the synergistic effect of 4f levels of Er and heterostructures was studied by combining steady-state, transient, and ultrafast spectral analysis techniques with DFT theoretical calculations. According to the Judd-Ofelt theory of lanthanide ions, the CO2 photoreduction test under single wavelength excitation verifies that the 4F7/2/2H11/2 → 4I15/2 emissions of Er in BPEr/SNOEr can be more easily absorbed by SNO and BP, further proving the role of the 4f levels. As a result, the CO and CH4 yields of BPEr/SNOEr-10 under visible light irradiation are 10.7 and 10.1 times higher than those of pure BP, respectively, and 3.4 and 1.5 times higher than those of SNO. The results of DFT calculations show that the Er single atoms can cause surface reconstruction, regulate the active sites of BP, and reduce the energy change value in the key steps (CO2* + H+ + e- → COOH* and COOH* → CO* + H2O). This work provides novel insights into the design of lanthanide single atom photocatalysts for CO2 reduction.

Nanomaterials-Enabled Physicochemical Antibacterial Therapeutics: Toward the Antibiotic-Free Disinfections

Bacterial infection continues to be an increasing global health problem with the most widely accepted treatment paradigms restricted to antibiotics. However, the overuse and misuse of antibiotics have triggered multidrug resistance of bacteria, frustrating therapeutic outcomes, and leading to higher mortality rates. Even worse, the tendency of bacteria to form biofilms on living and nonliving surfaces further increases the difficulty in confronting bacteria because the extracellular matrix can act as a robust barrier to prevent the penetration of antibiotics and resist environmental damage. As a result, the inability to eliminate bacteria and biofilms often leads to persistent infection, implant failure, and device damage. Therefore, it is of paramount importance to develop alternative antimicrobial agents while avoiding the generation of bacterial resistance to prevent the large-scale growth of bacterial resistance. In recent years, nano-antibacterial materials have played a vital role in the antibacterial field because of their excellent physical and chemical properties. This review focuses on new physicochemical antibacterial strategies and versatile antibacterial nanomaterials, especially the mechanism and types of 2D antibacterial nanomaterials. In addition, this advanced review provides guidance on the development direction of antibiotic-free disinfections in the antibacterial field in the future.

MoTe2/InN van der Waals heterostructures for gas sensors: a DFT study

Vertical van der Waals (vdW) heterostructures have shown potential for gas sensing owing to their remarkable sensitivity. However, the optimization process for achieving the best gas sensing performance is complicated by the heterostructure's reliance on both physical and electrical characteristics. This study employs density functional theory (DFT) to analyse the structural and electronic parameters of a MoTe2/InN vdW heterostructure. The findings of this study indicate that the vdW heterostructure has a type-II band alignment with higher adsorption energy towards NH3, NO2, and SO2 than the individual monolayers. In specific, the heterostructure is well suited for NO2 detection but has limitations in reliably detecting NH3 and SO2 due to longer recovery times. We find significant hybridization between the adsorbate and interacting surfaces' orbitals and a notable presence of NO2 molecular orbitals in proximity to the Fermi level. Additionally, dielectric and work function modulations offer a viable means to develop optical-based gas sensors that can selectively detect NO2. Our research provides valuable insights into vdW heterostructure design for high-performance gas sensors.

Aqueous Organic Batteries Using the Proton as a Charge Carrier

Benefiting from the merits of low cost, nonflammability, and high operational safety, aqueous rechargeable batteries have emerged as promising candidates for large-scale energy-storage applications. Among various metal-ion/non-metallic charge carriers, the proton (H+ ) as a charge carrier possesses numerous unique properties such as fast proton diffusion dynamics, a low molar mass, and a small hydrated ion radius, which endow aqueous proton batteries (APBs) with a salient rate capability, a long-term life span, and an excellent low-temperature electrochemical performance. In addition, redox-active organic molecules, with the advantages of structural diversity, rich proton-storage sites, and abundant resources, are considered attractive electrode materials for APBs. However, the charge-storage and transport mechanisms of organic electrodes in APBs are still in their infancy. Therefore, finding suitable electrode materials and uncovering the H+ -storage mechanisms are significant for the application of organic materials in APBs. Herein, the latest research progress on organic materials, such as small molecules and polymers for APBs, is reviewed. Furthermore, a comprehensive summary and evaluation of APBs employing organic electrodes as anode and/or cathode is provided, especially regarding their low-temperature and high-power performances, along with systematic discussions for guiding the rational design and the construction of APBs based on organic electrodes.

Research progress on black phosphorus hybrids hydrogel platforms for biomedical applications

Hydrogels, also known as three-dimensional, flexible, and polymer networks, are composed of natural and/or synthetic polymers with exceptional properties such as hydrophilicity, biocompatibility, biofunctionality, and elasticity. Researchers in biomedicine, biosensing, pharmaceuticals, energy and environment, agriculture, and cosmetics are interested in hydrogels. Hydrogels have limited adaptability for complicated biological information transfer in biomedical applications due to their lack of electrical conductivity and low mechanical strength, despite significant advances in the development and use of hydrogels. The nano-filler-hydrogel hybrid system based on supramolecular interaction between host and guest has emerged as one of the potential solutions to the aforementioned issues. Black phosphorus, as one of the representatives of novel two-dimensional materials, has gained a great deal of interest in recent years owing to its exceptional physical and chemical properties, among other nanoscale fillers. However, a few numbers of publications have elaborated on the scientific development of black phosphorus hybrid hydrogels extensively. In this review, this review thus summarized the benefits of black phosphorus hybrid hydrogels and highlighted the most recent biological uses of black phosphorus hybrid hydrogels. Finally, the difficulties and future possibilities of the development of black phosphorus hybrid hydrogels are reviewed in an effort to serve as a guide for the application and manufacture of black phosphorus -based hydrogels. Recent applications of black phosphorus hybrid hydrogels in biomedicine.

Synergy of heterojunction and interfacial strain for boosting photocatalytic H2 evolution of black phosphorus nanosheets

As an emerging post-graphene two-dimensional material, black phosphorus (BP) has attracted enormous interest as a promising cocatalyst for photocatalytic hydrogen (H₂) evolution, however, the activity of either pristine bulk or BP nanosheets is far from satisfactory. Herein, we present an effective strategy to greatly boost the H₂ evolution performance of BP via applying the synergistic effect of heterojunction and interfacial lattice strain. A multilayered heterostructure coupling BP nanosheets and nickel oxide (NiO) nanosheets with abundant interface P-Ni and PO bonds is synthesized and utilized as a proof-of-concept material for our design. Both the experimental and theoretical results have revealed that the strain is formed in BP-NiO multilayered heterostructure. The generated lattice strain induces the charge redistribution at the interface between BP and NiO, which leads to the improved electron transfer efficiency and favorable H* adsorption kinetics for photocatalytic H₂ evolution reaction. As a result, the BP-NiO heterostructure with strain effect exhibits much enhanced photocatalytic H₂ evolution activity in the presence of Eosin Y (EY) as photosensitizer, exceeding that of zero-strained BP/NiO heterostructure and many other reported noble-metal-free cocatalyst.

Size-dependent flame retardancy of black phosphorus nanosheets

Two-dimensional black phosphorus (BP) nanosheets are potential flame-retardant nano-additives. Herein, the effects of the size of BP nanosheets embedded in epoxy resin (EP) on flame retardancy are studied. BP nanosheets with four different sizes are synthesized from bulk BP by different exfoliation methods including solid ball milling, liquid ball milling, ultrasonic liquid exfoliation, and electrochemical exfoliation (samples are designated as sb-BP, lb-BP, us-BP, and ec-BP, respectively). lb-BP exhibits the best dispersion in the EP matrix, and the lb-BP/EP composite shows the best flame-retardancy properties among the four BP/EP composites. Compared to bare EP, lb-BP/EP shows obvious improvements including the reduction in the heat release peak rate by 34.4%, total heat release by 27.0%, peak of smoke production rate by 69.2%, and total production of carbon monoxide by 50.8%. The mechanistic study reveals that lb-BP serves as a barrier and carbonization catalyst to delay combustion. These results confirm the size dependence of flame-retardancy properties of BP nanosheets and the new knowledge provides insights into the size dependent effects of other two-dimensional materials.

Black phosphorus coupled bismuth chloride oxide nanocomposites for efficient photocatalytic CO2 reduction

Photocatalytic CO2 reduction to useful CO and CH4 is significantly boosted by black phosphorus (BP) coupled bismuth oxychloride (BiOCl) nanocomposites, presenting an efficient and reliable approach to green and sustainable solar energy conversion.

State-of-the-Art Advancements of Atomically Thin Two-Dimensional Photocatalysts for Energy Conversion

Excessive use of fossil fuels leads to energy shortages and environmental pollution, threatening human health and social development. As a clean, green, and sustainable technology, generation of renewable energy from...

Ultrathin black phosphorus as pivotal hole extraction layer and oxidation evolution co-catalyst boosting solar water oxidation

Inefficient minority carrier extraction and sluggish oxygen evolution reaction (OER) kinetics are two principal contradictions restricting photoelectrochemical water oxidation. Here, the aforementioned restrictions could be simultaneously alleviated by coupling ultrathin...

Harnessing the Volume Expansion of MoS3 Anode by Structure Engineering to Achieve High Performance Beyond Lithium-Based Rechargeable Batteries

Beyond-lithium-ion storage devices are promising alternatives to lithium-ion storage devices for low-cost and large-scale applications. Nowadays, the most of high-capacity electrodes are crystal materials. However, these crystal materials with intrinsic anisotropy feature generally suffer from lattice strain and structure pulverization during the electrochemical process. Herein, a 2D heterostructure of amorphous molybdenum sulfide (MoS₃ ) on reduced graphene surface (denoted as MoS₃ -on-rGO), which exhibits low strain and fast reaction kinetics for beyond-lithium-ions (Na⁺ , K⁺ , Zn²⁺ ) storage is demonstrated. Benefiting from the low volume expansion and small sodiation strain of the MoS₃ -on-rGO, it displays ultralong cycling performance of 40 000 cycles at 10 A g^-1 for sodium-ion batteries. Furthermore, the as-constructed 2D heterostructure also delivers superior electrochemical performance when used in Na⁺ full batteries, solid-state sodium batteries, K⁺ batteries, Zn²⁺ batteries and hybrid supercapacitors, demonstrating its excellent application prospect.