Ultrathin Nanosheets Research Articles

Ag2Se nanoparticles anchored on S-g-C3N4 nanosheets towards efficient photocatalytic tetracycline hydrochloride removal and H2 generation

To improve the stability of Ag based co-catalysts and to increase the photocatalytic performance of graphitic carbon nitride (g-C3N4), Ag2Se nanoparticles were grown onto superior thin sulfur-doped g-C3N4 nanosheets which was fabricated via two-step thermal polymerization at high temperature. Ultrathin S-doped g-C3N4 nanosheets were prepared via two-step thermal polymerization using melamine and thiourea. The ratios of Ag2Se were adjusted to fabricate a series of Ag2Se/S-g-C3N4 (Ag2Se/SCN) composite samples by controlled solvothermal synthesis. S-doping plays an important role in mono-dispersion of Ag2Se nanoparticles on S-g-C3N4 nanosheets because of the control of growth sites. The photocatalytic removal of tetracycline hydrochloride test indicates that sample Ag2Se/SCN-3 with Ag2Se loading of 3 % reveals the best removal effect, in which tetracycline hydrochloride of 60 % is removed within 60 min. Photocatalytic hydrogen generation test results without co-catalyst addition demonstrate that sample Ag2Se/SCN-3 exhibits the best H2 evolution rate of 2116.35 μmol·g−1·h−1, which is 3.8 times of that of pure carbon nitride. The photocatalytic mechanism tests suggest that Schottky heterojunctions are formed in the Ag2Se/S-g-C3N4 composites. The formation of Schottky heterojunctions improved the separation efficiency of photogenerated charge carriers. The incorporation of Ag2Se nanoparticles (as the co-catalyst) on S-g-C3N4 nanosheets is the key for drastically improving the photocatalytic performance and eliminating the use of Pt co-catalyst during the photocatalytic processes.

Regulating Spin Polarization via Axial Nitrogen Traction at Fe-N5 Sites Enhanced Electrocatalytic CO2 Reduction for Zn-CO2 Batteries.

Single Fe sites have been explored as promising catalysts for the CO2 reduction reaction to value-added CO. Herein, we introduce a novel molten salt synthesis strategy for developing axial nitrogen-coordinated Fe-N5 sites on ultrathin defect-rich carbon nanosheets, aiming to modulate the reaction pathway precisely. This distinctive architecture weakens the spin polarization at the Fe sites, promoting a dynamic equilibrium of activated intermediates and facilitating the balance between *COOH formation and *CO desorption at the active Fe site. Notably, the synthesized FeN5, supported on defect-rich in nitrogen-doped carbon (FeN5@DNC), exhibits superior performance in CO2RR, achieving a Faraday efficiency of 99 % for CO production (-0.4 V vs. RHE) in an H-cell, and maintaining a Faraday efficiency of 98 % at a current density of 270 mA cm-2 (-1.0 V vs. RHE) in the flow cell. Furthermore, the FeN5@DNC catalyst is assembled as a reversible Zn-CO2 battery with a cycle durability of 24 hours. In situ IR spectroscopy and density functional theory (DFT) calculations reveal that the axial N coordination traction induces a transformation in the crystal field and local symmetry, therefore weakening the spin polarization of the central Fe atom and lowering the energy barrier for *CO desorption.

Ultrathin Porous Carbon Nitride Anchored with Pt Nanoclusters for Synergistic Enhancement of Hydrogen Production in Alkaline Photocatalytic Polyester Reforming.

Photocatalytic reforming (PR) of polyester waste, fueled by renewable sources like solar energy, offers a sustainable method for producing clean H2 and valuable by-products under mild conditions. The design of high-performance photocatalyst plays a pivotal role in determining the efficacy of an alkaline polyester PR system, influencing H2 generation activity and selectivity. Here, ultrathin porous carbon nitride nanosheets (UP-CN) loaded with Pt nanoclusters (Pt NCs, average diameter of 1.7nm) with uniform Pt NCs distribution are introduced. The resulting Pt NCs/UP-CN catalyst can accelerate charge and mass transfer while providing additional active sites, achieving superior H2 generation rates of 11.69mmol gcat -1 h-1 and 2923mmol gPt -1 h-1 under AM 1.5 light, which nine times higher than that of Pt nanoparticles-bulk graphitic carbon nitride composite (1.29mmol gcat -1 h-1 and 258mmol gPt -1 h-1) as counterpart. This performance also surpasses that of previously reported carbon nitride-based and TiO2-based photocatalysts. Moreover, the density functional theory calculations reveal a significant reduction in the energy barrier for the water dissociation step (H2O + * → *H + OH) at the interface between UP-CN and anchored Pt NCs, showcasing the synergistic effect between Pt NCs and UP-CN. This catalytic system also exhibits universality across various polyester plastics.

Highly sensitive toluene sensor based on silver Ear-Like F-doped Co3O4 templated from Co(OH)F Guided by SiO2 nanospheres

This study successfully synthesized “silver ear-like” Co(OH)F using 15 nm SiO2 spheres as seeds. Gas sensitivity of Co(OH)F with and without SiO2 spheres to toluene was compared at different annealing temperatures. The results demonstrate that the Co(OH)F-Si-350 sensor exhibits optimal gas sensitivity to toluene, with a response of 35 (Rg/Ra) to 100 ppm of toluene at 220℃, with response and recovery times of 50 s and 80 s, respectively. Notably, the sensor detected toluene concentrations as low as 50 ppb, indicating good sensitivity to low concentrations. These findings suggest that the structural transformation resulting from the introduction of SiO2 nanospheres, forming ultra-thin nanosheet clusters (∼12 nm), provides abundant active sites, effectively promoting substance diffusion and adsorption/desorption processes. Additionally, the incorporation of fluorine enhances the Lewis acidity of the material, facilitating the formation of stable adsorption states for gas molecules on the surface. These results reveal the significant impact of the structural transformation caused by the introduction of SiO2 nanospheres on gas sensitivity, providing a strong theoretical foundation for further optimizing gas sensor design.

Tailor-made the ultrathin nanosheet and acid site accessibility of mordenite zeolite for carbonylation of dimethyl ether

Precisely tailored nano-morphology and crystal growth endures mordenite (MOR) zeolites with reduced internal diffusion resistance, enabling greater accessibility of existing acid sites to further stimulate catalysis. Controllable synthesis nanosheet MOR zeolite thinner than 20 nm along at least one dimension is highly attractive but remains great challenge. Herein, c axis along the [001] direction shortened MOR nanosheets with a thickness of 10–20 nm was synthesized. As expected, the mass transfer performance over the nanosheet sample is significantly improved by 2.5 times compared with the conventional nano-morphology. Furthermore, more Brønsted acid sites (BAS) can be induced into 8-membered ring (8-MR) pores in the nanosheet MOR zeolite. The conversion of dimethyl ether (DME) to methyl acetate over the ultrathin MOR zeolite is increased from 17.4 % to 71.7 % compared to that of the conventional nanoparticle. The DME conversion was stable at 70.0 % after reaction 80 h, when the acid sites located in 12-membered ring pores was poisoned by the pyridine molecule. Unexpectedly, we discovered that the desorption behavior of pyridine is also influenced by the accessibility of acid site, not only by the amount of BAS in 8-MR. The unique nanosheet structure with short c axis reduces the spatial stability of pyridine adsorbed on BAS in the 8-MR side pocket and the BAS in the 8-MR side pocket can be recovered at lower temperatures. Herein, a new insight into of DME carbonylation catalyzed by ultrathin nanosheet of MOR zeolite is revealed.

Atomically dispersed nickel-bismuth dual-atom sites for high rate electrochemical CO2 reduction

We report a diatomic-site catalyst configuration constituted by Ni-N3 and Bi-N4 embedded in ultrathin nitrogenated carbon nanosheets (Ni/Bi-N-C) which showed dramatically improved activity and selectivity for the conversion of CO2 to CO. Specifically, the catalyst exhibited high CO Faradaic efficiency (FECO) of above 90 % over a wide potential window from −0.76 to −2.22 versus reversible hydrogen electrode with the maximum CO partial current density up to 312 mA cm−2 in a flow cell, and coupled with robust durability. Ni/Bi-N-C-based membrane electrode assembly (MEA) device presented ultrahigh FECO of 95.7 % at 750 mA and over 100 h of continuous operation without decay under constant current density of 100 mA cm−2. Mechanistic studies and density functional theory calculations reveal that regulating the CO2RR catalytic performance via nearby Ni and Bi active sites can potentially break the activity benchmark of the single metal counterparts because the neighboring Ni and Bi active sites work in synergy to decrease the reaction barrier for the formation of *COOH and desorption of *CO. This work presents an efficient combination of two metal atomic sites which was designed by optimizing the interaction between the atomic sites and key reaction intermediates, resulting in the high-rate electrocatalytic CO2 reduction.

Ultrathin Gd-Oxide Nanosheet as Ultrasensitive Companion Diagnostic Tool for MR Imaging and Therapy of Submillimeter Microhepatocellular Carcinoma.

Early stage hepatocellular carcinoma (HCC) presents a formidable challenge in clinical settings due to its asymptomatic progression and the limitations of current imaging techniques in detecting micro-HCC lesions. Addressing this critical issue, we introduce a novel ultrathin gadolinium-oxide (Gd-oxide) nanosheet-based platform with heightened sensitivity for high-field MRI and as a therapeutic agent for HCC. Synthesized via a digestive ripening process, these Gd-oxide nanosheets exhibit an exceptional acid-responsive profile. The integration of the ultrathin Gd-oxide with an acid-responsive polymer creates an ultrasensitive high-field MRI probe, enabling the visualization of submillimeter-sized tumors with superior sensitivity. Our research underscores the ultrasensitive probe's efficacy in the treatment of orthotopic HCC. Notably, the ultrasensitive probe functions dually as a companion diagnostic tool, facilitating simultaneous imaging and therapy with real-time treatment monitoring capabilities. In conclusion, this study showcases an innovative companion diagnostic tool that holds promise for the early detection and effective treatment of micro-HCC.

Ultrathin BSA-Stabilized Black Phosphorous Nanoreactor Boosts Mild-Temperature Photothermal Therapy Through Modulation of Cellular Self-Defense Fate.

Mild-temperature photothermal therapy (mild-PTT, 42-45°C) offers a higher level of biosafety. However, its therapeutic effects are compromised by the heat shock response (HSR), a cellular self-defense mechanism, which triggers the overexpression of heat shock proteins (HSPs) with the capacity of repairing the damaged tumor cells. Herein, this work fabricates a novel nanoreactor by incorporating up-conversion nanoparticles (UCNPs), chlorin e6 (Ce6), and glucose oxidase (GOx) onto the ultrathin black phosphorus nanosheet (BPNS) (denoted as GOx-BUC). This nanoreactor amplifies mild-PTT effects under irradiation with an 808nm laser, modulating HSPs-mediated cellular self-defense fate. On one hand, upon irradiation with a 980nm laser, UCNPs can transfer energy to excite Ce6, leading to the generation of ROS burst, which achieves indiscriminate damage to HSPs activity in deeper tumor tissues. On the other hand, GOx can consume glucose, thereby depleting the ATP energy supply and further suppressing HSPs expression. Consequently, GOx-BUC exhibits excellent anti-tumor efficacy under mild temperature in a human colorectal cancer mouse model, resulting in complete tumor inhibition with negligible side effects. This black phosphorous nanoreactor, featuring dual-track HSPs destruction functionality, introduces novel perspectives for enhancing mild-PTT effectiveness while maintaining high biosafety.

Biomass Derived Self-Doped Carbon Nanosheets Enable Robust Hole Transport Layers with Ion Buffer for Perovskite Solar Cells.

The diffusion of iodine species and lead leakage during device degradation represent the main obstacles restricting the commercial application of perovskite solar cells (PSCs). Cobalt loaded ultrathin carbon nanosheets (Co(III)-CNS) derived from biomass are prepared as ion buffer material to construct robust hole transport layers (HTLs). The carbon nanosheets containing trivalent cobalt ions can facilitate the oxidation of the hole transport material while preserving the structural integrity and electrical properties of HTLs under thermal stress, thereby ensuring efficient carrier transport. The two-dimensional ultrathin graphitized lamellar structure of Co(III)-CNS is conducive to alleviate the corrosive effects of the outward diffusion of iodine species on HTLs and silver electrodes, while avoiding irreversible degradation of PSCs. With the improvement of HTL composition and the related interfaces, Co(III)-CNS doped devices can maintain intact device structure under thermal stress and remain above 80% of the original power conversion efficiency (PCE) after thermal aging at 85 oC for 720 h. Notably, the chemical interactions between heteroatoms of self-doped carbon nanosheets and the mobile lead ions can effectively alleviate lead leakage and avoid the potential impacts of device degradation on ecosystem. Ultimately, the Co(III)-CNS doped PSCs with enhanced thermal stability exhibit a champion PCE of 22.32%.

Regulating the interaction between Bi metal and Bi24O31Br10 nanosheets for efficient photoreduction of CO2

Artificial photosynthesis converting CO2 into valuable compounds has garnered significant interest. However, the insufficient surface activity sites, weak adsorption capacity of CO2 and poor electron-hole separation capability hinder CO2 photoreduction used for practical implementation. Herein, Bi nanoparticles/Bi24O31Br10 composite photocatalyst (Bi/BOB) was designed constructed through in-situ reduction of bismuth metal on the surface of ultra-thin Bi24O31Br10 nanosheets. Bi/BOB exhibits an excellent ability to reduce CO2 to CO. The CO2 reduction rate of the optimized Bi/BOB composite catalyst is 43.07 μmol·g−1·h−1, which is significantly superior to other reported bismuth-based photocatalysts. Experimental characterization and Theoretical simulation calculation reveal that the in-situ reduction of bismuth metal causes significant local lattice distortion and uneven charge distribution, thereby producing a strong interaction between Bi nanoparticles and BOB support. So, it enhances the adsorption and activation of carbon dioxide molecules and reduces the Gibbs free energy barrier during the catalytic reaction. Moreover, the strong interaction helps to enhance the separation of photogenerated charge carriers and stability of catalysts. This study offers research suggestions for the interaction between metal and support to enhance CO2 reduction.

Boosting seawater denitrification in an electrochemical flow cell

Nitrogen compounds in current seawater treatment processes typically are converted to nitrate, threatening seawater quality and marine ecology. Electrochemical denitrification is a promising technique, but its efficiency is severely limited by the presence of excess chloride ions. In this work, a flow-through cell went through an on-demand chlorine-mediated electrochemical-chemical tandem reaction process was designed for efficient seawater denitrification. Equipped with ultrathin cobalt-based nanosheets as the cathode catalyst and commercial IrO2-RuO2/Ti as the anode, the newly designed flow-through cell achieved nitrate removal efficiency that was about 50 times greater than the batch cell and nearly 100 % N2 selectivity. Moreover, nitrite and ammonia can also be removed with over 93 % efficiency in total nitrogen (TN) removal. Furthermore, the concentration of active chlorine in the effluent could be adjusted within two orders of magnitude, enabling on-demand release of active chlorine. Finally, this flow-through cell reduced the TN of actual mariculture tailwater (40.1 mg N L-1 nitrate) to only 5.7 mg N L-1, meeting the discharge standard for aquaculture tailwater of Fujian, China. This work demonstrates the paradigm of deep denitrification from ultra-concentrated chlorine ion wastewater using an on-demand active chlorine-mediated electrochemical-chemical tandem reaction process.

Synergistic effects of (110) facet and oxygen vacancies on hydrangea - like SnO2 for ppb-level formaldehyde sensing

A unique hydrangea-like SnO2 assembled by ultrathin nanosheets interlaced with veins was successfully prepared via hydrothermal process. The sensor based on this material exhibits excellent sensing properties toward formaldehyde at 170 °C, including a high response (8.5 to 1 ppm and 57.7 to 50 ppm), good selectivity, and quick response/recovery (7/16 s), with a detection limit of 3.9 to 80 ppb formaldehyde. These superior sensing characteristics can be attributed to the synergistic effect of the porous ultrathin nanosheets (∼12 nm) and the exposed (110) facets with more oxygen vacancies. The Density functional theory (DFT) calculations are applied to explore the formaldehyde sensing mechanism of the novel structure.

Enhanced overall water splitting by morphology and electronic structure engineering on pristine ultrathin metal-organic frameworks

Metal-organic frameworks (MOFs) have caused extensive attention attributed to their widespread applications including electrocatalysis by virtue of their distinctive structural characteristics. However, the direct application of pristine MOFs as bifunctional electrocatalysts is quite challenging due to their insufficient active sites and poor electrical conductivity. In this research, the ultrathin tri-metal (Fe, Co, and V) doped FeCoV-NiMOF nanosheet arrays were prepared through a facile hydrothermal method. Benefiting from the distinctive ultrathin (1.5 nm) nanosheet arrays and electronic structure reconfiguration induced by heteroatom doping, the prepared FeCoV-NiMOF displays the low overpotentials of 238, 309, and 408 mV for oxygen evolution reaction (OER) and 144, 255, and 349 mV for hydrogen evolution reaction (HER) at the current densities of 10, 100, and 1000 mA cm−2, respectively, outperforming the vast majority of previously reported bifunctional pristine MOFs. The electrolytic cell utilizing FeCoV-NiMOF as both cathode and anode requires just 1.61 V to attain 10 mA cm−2 and displays superior stability of 100 h at 100 mA cm−2. In the anion exchange membrane electrolyzer, as-prepared FeCoV-NiMOF needs a low cell voltage of 2.16 V at 500 mA cm−2 for effective overall water splitting, demonstrating its substantial potential as bifunctional electrodes for H2 production. The viable and efficient strategy in this study exhibits great prospects to enrich the exploration of bifunctional MOF-based electrocatalysts with superior performance for renewable energy conversion.

Hierarchical ultra-thin porous Co3O4 nanosheets derived from mixed phase α- and β-Co(OH)2 for high sensitivity and ppb-level acetone sensing

Addressing the energy loss of carriers during transmission and achieving high sensitivity detection of target gases facilitates the synthesis of trace-level acetone sensors, which is of great significance in the fields of air quality early warning, health monitoring, and industrial safety monitoring. Here, we propose a strategy where, under hydrothermal conditions, the content of mixed-phase α- and β-Co(OH)2 is regulated by varying the protonation level of 2-methylimidazole in different solutions, leading to the formation of porous monocrystalline Co3O4 microflower structure. The microflower is assembled from ultrathin nanosheets, and the 3D-interconnected macroporous and mesoporous structure provides high surface area and gas diffusion channels. The monocrystalline and two-dimensional structures favor high carrier mobility, enhancing the signal-to-noise ratio. Furthermore, the thickness of the Co3O4 nanosheets is less than twice the Debye length, making their electrical properties completely dependent on surface. DFT calculations also indicate that the few layers Co3O4 model is conducive to acetone adsorption. The Co3O4 sensor exhibits exceptional gas sensing performance towards acetone, with favourable sensitivity (16.83 to 10 ppm), selectivity, and stability, as well as an ultra-low practical detection limit of 10 ppb. Rich point defects and line defects play a significant role in improving the surface activity of the sensitive material as well. This research offers a pathway for designing sensors with exceptional gas sensitivity by employing a straightforward method to control the morphology of sensitive materials, combined with defect engineering to enhance sensing activity.

Photocatalytic reduction of the uranium(Ⅵ) by ultra-thin porous g-C3N4 nanosheets synthesized via microwave-assisted

Graphitic carbon nitride (g-C3N4) has garnered significant attention in the realm of photocatalytic reduction of U(Ⅵ) from aqueous solutions owing to its favorable bandgap and visible light responsiveness. Nevertheless, conventionally prepared bulk g-C3N4 suffers from limitations such as a small specific surface area and high recombination of photo-generated charges, consequently impeding the efficiency of photocatalytic reactions and hampering practical applications. To address these shortcomings, this study presents a novel approach wherein ultra-thin porous g-C3N4 nanosheets were successfully synthesized through the microwave-assisted calcination of urea in a single step. The resulting g-C3N4 nanosheets exhibit a multi-hollow mesh structure with a significantly enlarged specific surface area, the specific surface area and pore size of MCN90 are 170 m²/g and 17 nm, respectively, which are 2.3 times and 8 times that of the bulk g-C3N4. Photocatalytic experiments revealed that these ultra-thin porous nanosheets demonstrate superior performance in the reduction of U(Ⅵ) to U(Ⅳ), achieving a reduction rate of 100 % within 20 minutes for the optimal sample, as opposed to 78 % in 40 minutes for bulk g-C3N4. This enhanced photocatalytic activity can be primarily attributed to the unique ultra-thin porous nanosheet structure, which facilitates increased specific surface areas, improve photoelectric properties, and substantially shortened electron migration distances which reduce the recombination efficiency of photogenerated electrons and holes pairs. Consequently, these findings not only offer insights into the optimization of g-C3N4 for U(Ⅵ) reduction but also provide a valuable reference for the preparation of other two-dimensional ultra-thin porous materials aimed at similar applications.

Nickel single-atom synergistic iron-nitrogen sites for efficient CO2 electroreduction at a wide potential range

Recently, diatomic site catalysts (DASCs) by introducing a second metal active site have become a research focus in electrochemical CO2 reduction reaction (eCO2RR), as can regulate electronic structure of metal centers and optimize reaction free energies. However, hitherto the studies on the origin of the outstanding performance of DASCs and the accurate identification of active centers are not still clear. Herein, we designed a nickel–iron diatomic site catalyst by loading highly dispersed iron phthalocyanine (FePc) on a nickel single-atom with ultrathin porous nitrogen-doped carbon nanosheet substrate (denoted as FePc/M-LNi-NC). Experimental and calculational results prove that the synergistic catalysis of FePc and carbon nanosheet based Ni single-atom endowed FePc/M-LNi-NC achieving excellent CO2 reduction performance with a maximum CO Faradaic efficiency of 98.8 % at –0.8 V vs. RHE. In particular, the current density of FePc/M-LNi-NC at −1.0 V vs. RHE in an H-type cell (−20.9 mA/cm2) is 5.6 times that of FePc (3.7 mA/cm2). Compared with M-LNi-NC, the potential range of FePc/M-LNi-NC when FECO above 95 % expands from 0.31 to 0.43 V. Density functional theory calculations reveal that the Fe site in FePc/M-LNi-NC has a lower free energy change for *COOH formation (ΔG*COOH) and CO desorption (ΔGCO) than Ni site, thus exhibits higher electrocatalytic activity. Furthermore, the ΔG*COOH on FePc/M-LNi-NC declines from 0.78 to 0.08 eV compared to M-LNi-NC, and the ΔGCO lowers from 1.36 to 0.33 eV compared to FePc, thus FePc/M-LNi-NC achieves high performance for eCO2RR at a wide potential range.

Hole Polaron-Mediated Suppression of Electron-Hole Recombination Triggers Efficient Photocatalytic Nitrogen Fixation.

In the pursuit of successful photocatalytic transformations, challenges persist due to limitations in charge carrier utilization and transfer efficiency, which stemming from rapid recombination. Overcoming these limitations necessitates the exploration of novel mechanisms that enhance the effective separation of photogenerated electron-hole pairs. Herein, deviating from the conventional approach of enhancing carrier migration to separate photogenerated charges and extend their lifetime, the proposal is to directly prevent the recombination of photogenerated electrons and holes by forming hole polarons. Specifically, disordered pores are introduced on the surface of KTaO3 ultrathin sheets, and the clear-cut evidences in electron paramagnetic resonance, photoluminescence, and ultrafast spectroscopy unambiguously confirm the enhanced carrier-phonon coupling, which results in the formation of hole polarons to impede the recombination of photogenerated electron-hole pairs. Taking the challenging nitrogen oxidation reaction as an example, it is found that the hole polarons in atomic-disordered pore KTaO3 ultrathin nanosheets trigger outstanding photo-oxidation performance of nitrogen (N2)to nitrate, with a nitrate-producing rate of 2.1 mg g-1 h-1. This scenario is undoubtedly applicable to a wide variety of photocatalytic reactions due to the common challenge of charge carrier recombination in all photocatalytic processes, manifesting broad implications for promoting photocatalysis performance.

Construction of ultra-thin NiMo3S4 nanosheet sphere electrode for high-performance hybrid supercapacitor

The construction of electrode materials with rational morphology and structure based on bimetallic sulfides is crucial to improve the performance of supercapacitors. Ultra-thin three-dimensional nickel molybdenum sulfide nanosheet spheres (NiMo3S4 NSSs) are grown on nickel foam (NF) using a one-step hydrothermal synthesis. NiMo3S4 NSSs have a diameter of ∼ 5 μm and nanosheet thickness of 200 nm. The effects of increasing the hydrothermal synthesis time and molar concentration ratios of Ni2+ to MoO42- on the morphologies of the NiMo3S4 are investigated. Due to the synergistic effect of NiMo3S4 NSSs and bimetallic ions which can provide a larger solution contact areas and improve the redox activity, the electrode exhibits good electrochemical properties. The specific capacity of NiMo3S4 NSSs/NF electrode can reach 1002.4 C/g (1 A/g). After being assembled into a hybrid supercapacitor (HSC) with activated carbon (AC), the energy density can reach 72.1 Wh/kg at the power density of 749.9 W/kg. In addition, the HSC shows an excellent stability of 89 % after 10, 000 charge-discharge cycles (10 A/g).

Synergistic enhancement of singlet oxygen generation in Au and oxygen vacancy co-modified Bi2MoO6 ultrathin nanosheets for efficient ciprofloxacin degradation

Solar-driven molecular oxygen activation (MOA) is crucial for generating reactive oxygen species (ROS) for pollutant degradation, while the low activation efficiency greatly weakens the degradation efficiency. Herein, oxygen vacancies (OVs) and Au nanoparticles are co-introduced into Bi2MoO6 (ABMOH) to enhance the photocatalytic activity of Bi2MoO6 (BMO), thereby promoting MOA efficiency. Density functional theory demonstrates that the introduction of OVs not only improves the molecular oxygen adsorption on BMO, and but also strengthens the O-O bond dissociation of molecular oxygen, which is beneficial to MOA. Meanwhile, the unique localized surface plasmon resonance effect of Au nanoparticles immensely increases the photo-absorption capacity. Crucially, both OVs and Au nanoparticles work as “electron traps” to capture photogenerated electrons, thereby accelerating charge transfer. Based on the advantage of OVs and Au nanoparticles, ABMOH displays excellent MOA efficiency, and the degradation rate constant of ciprofloxacin (CIPF) by ABMOH-4 is 3.62-fold higher than BMO. Free radical trapping experiment and electron spin resonance suggest that singlet oxygen (1O2) can be selectively formed in the ABMOH system for CIPF degradation, and superoxide radical (•O2–) conversion and energy transfer are two pathways for 1O2 formation. This investigation serves as a beacon for the strategic design of high-performance and stable photocatalysts for MOA activation, paving the way for advancements in environmental remediation.

Halloysite-derived hierarchical cobalt silicate hydroxide hollow nanorods assembled by nanosheets for highly efficient electrocatalytic oxygen evolution reaction

The oxygen evolution reaction (OER) is regarded as the bottleneck of electrolytic water splitting. Thus, developing robust earth-abundant electrocatalysts for efficient OER has received a great deal of attention and it is an ongoing scientific challenge. Herein, hierarchical hollow nanorods assembled with ultrathin mesoporous cobalt silicate hydroxide nanosheets (denoted as CoSi) were successfully fabricated, using the silica nanotube derived from halloysite as a sacrificial template, via a simple hydrothermal method. The resulting cobalt silicate hydroxide nanosheets stack with thicknesses ∼10 nm, as confirmed by transmission electron microscopy. The elaborated nanoarchitecture possesses a high specific surface area (SSA) allowing good exposure to the cobalt active centers exhibiting superior catalytic activity vs analogs synthesized using sodium silicate. Among all as-prepared CoSi samples, those synthesized at 150 °C (CoSi-150) exhibited the minimum overpotential of ∼347 mV at a current density of 10 mA cm–2. In addition, CoSi-150 also exhibited superior performance against typical cobalt-based catalysts, and its surface hydroxyl groups were beneficial for the enhancement of OER performance. Furthermore, the CoSi-150 showed excellent durability and stability after the 105 s chronopotentiometry test in 1 M KOH. This design concept provides a new strategy for the low-cost preparation of high-quality cobalt water splitting electrocatalysts.