The Superaerophobic N-Doped Carbon Nanocage with Hydrogen Spillover Effort for Enhanced Hydrogen Evolution.

Under the high current density, the excessive strong adsorption of H* intermediates and H2 accumulation the catalysts are the major obstacle to the industrial application of hydrogen evolation reaction (HER) catalysts. Herein, through experimental exploration, it is found that the superaerophobic Nitrogen (N)-doped carbon material can promote the rapid release of H2 and provide H* desorption site for the hydrogen spillover process, which makes it have great potential as the catalysts support for hydrogen spillover. Based on this discovery, this work develops the hydrogen spillover catalyst with electron-rich Pt sites loaded on N-doped carbon nanocage (N-CNC) with adjustable work function. Through a series of comprehensive electrochemical tests, the existence of hydrogen spillover effort has been proved. Moreover, the in situ tests showed that pyrrolic-N can activate adjacent carbon sites as the desorption sites for hydrogen spillover. The Pt@N-1-CNC with the minimum work function difference (ΔΦ) between Pt NPs and support shows superior hydrogen evolution performance, only needs overpotential of 12.2 mV to reach current density of 10 mA cm-2 , outstanding turnover frequency (TOF) (44.7 s-1 @100 mV) and superior durability under the 360 h durability tests at current density of 50 mA cm-2 .

Monometallic Ultrasmall Nanocatalysts via Different Valence Atomic Interfaces Boost Hydrogen Evolution Catalysis.

Synergistic monometallic nanocatalysts have attracted much attention due to their high intrinsic activity properties. However, current synergistic monometallic nanocatalysts tend to suffer from long reaction paths due to restricted nanoscale interfaces. In this paper, we synthesized the interstitial compound N-Pt/CNT with monometallic atomic interfaces. The catalysts are enriched with atomic interfaces between higher valence Ptδ+ and Pt0, allowing the reaction to proceed synergistically within the same component with an ideal reaction pathway. Through ratio optimization, N2.42-Pt/CNT with a suitable ratio of Ptδ+ and Pt0 is synthesized. And the calculated turnover frequency of N2.42-Pt/CNT is about 37.4 s-1 (-0.1 V vs reversible hydrogen electrode (RHE)), six times higher than that of the commercial Pt/C (6.58 s-1), which is the most intrinsically active of the Pt-based catalysts. Moreover, prepared N2.42-Pt/CNT exhibits excellent stability during the chronoamperometry tests of 200 h. With insights from comprehensive experiments and theoretical calculations, Pt with different valence states in monometallic atomic interfaces synergistically accelerates the H2O dissociation step and optimizes the Gibbs free energy of H* adsorption. And the existence of desirable hydrogen transfer paths substantially facilitates hydrogen evolution reaction kinetics.

Highly conductive Ti3C2 MXene-supported CoAl-layered double hydroxide nanosheets for ultrasensitive electrochemical detection of organophosphate pesticide fenitrothion.

A novel electrochemical method is presented for ultrasensitive detection of the organophosphate pesticide (OPP) fenitrothion by using Ti3C2 MXene/CoAl-LDH nanocomposite as the electrode modifier. The Ti3C2 MXene/CoAl-LDH nanocomposite is synthesized by growing CoAl-LDH in situ on MXene nanosheets. The combination of two ultrathin 2D materials provides more active sites, larger specific surface area, superior adsorption properties, and better electrical conductivity, which leads to rapid electron-transfer and mass-transfer between the substrate electrode and analytes when it is acted as the electrochemical sensing material. In addition, through the chelation of phosphate groups with the Ti defect sites enriched in MXene, OPP is adsorbed on the electrode. Consequently, the corresponding modified electrode gives rise to a wide linear response range of 0.03 ~ 120 µmol/L for the differential pulse voltammetry detection of fenitrothion with a low detection limit of 5.8 nmol/L (3σ). The method offers good repeatability, stability, selectivity, and practicability for real samples. This strategy provides a reference platform for the electrochemical monitoring of trace OPPs residue by using MXene/LDH-based nanocomposites.

Polyhedral Au Nanoparticle/MoOx Heterojunction-Enhanced Ultrasensitive Dual-Mode Biosensor for miRNA Detection Combined with a Nonenzymatic Cascade DNA Amplification Circuit.

A novel homologous surface-enhanced Raman scattering (SERS)-electrochemical (EC) dual-mode biosensor based on a 3D/2D polyhedral Au nanoparticle/MoOx nanosheet heterojunction (PAMS HJ) and target-triggered nonenzyme cascade autocatalytic DNA amplification (CADA) circuit was constructed for highly sensitive detection of microRNA (miRNA). Mixed-dimensional heterostructures were prepared by in situ growth of polyhedral Au nanoparticles (PANPs) on the surface of MoOx nanosheets (MoOx NSs) via a seed-mediated growth method. As a detection substrate, the resulting PAMS HJ shows the synergistic effects of both electromagnetic and chemical enhancements, efficient charge transfer, and robust stability, thus achieving a high SERS enhancement factor (EF) of 4.2 × 109 and strong EC sensing performance. Furthermore, the highly efficient molecular recognition between the target and smart lock probe and the gradually accelerated cascade amplification reaction further improved the selectivity and sensitivity of our sensing platform. The detection limits of miRNA-21 in SERS mode and EC mode were 0.22 and 2.69 aM, respectively. More importantly, the proposed dual-mode detection platform displayed excellent anti-interference and accuracy in the analysis of miRNA-21 in human serum and cell lysates, indicating its potential as a reliable tool in the field of biosensing and clinical analysis.

Precise Interstitial Built-In Electric Field Tuning for Hydrogen Evolution Electrocatalysis.

The built-in electric field (BEF) has become an effective means of adjusting the electronic structure and hydrogen spillover to influence the adsorption of intermediates. However, the previously reported BEF cannot be tuned continuously and precisely. Herein, a series of nanocatalysts with interstitial BEF were successfully synthesized, and the effect of precisely tuned interstitial BEF on the intermediate's adsorption and hydrogen spillover was systematically investigated using changing the insertion of interstitial B. Three catalysts with different BEF strengths were obtained by changing the interstitial content (B0.22-Cu/NC, B0.30-Cu/NC, B0.41-Cu/NC), and it was demonstrated that B0.30-Cu/NC gave the best catalytic performance for hydrogen evolution reactions (HERs). The turnover frequency (TOF) value is shown to reach 0.36 s-1 at just -0.1 V vs. RHE, which is about 3 times that of Cu (0.12 s-1). For the HER, it is one of the best Cu-based catalysts reported to date (Table S3). Besides, when the catalyst was applied to the cathode of the PEM water electrolyzer, B0.30-Cu/NC exhibited long-time stability at a water-splitting current density of 500 mA cm-2. Density functional theory and in situ Raman spectroscopy suggest that a suitable interstitial BEF can not only optimize the intermediate's adsorption but also promote hydrogen spillover.

Mixture Phases Engineering of PtFe Nanofoams for Efficient Hydrogen Evolution.

Phase engineering is a promising but challenging approach to construct PtFe-based catalysts with efficient hydrogen evolution reaction (HER) performance. Herein, the authors successfully synthesize PtFe nanofoams with face center cubic (fcc) phase, with simple cubic crystalline (scc) phase and with the mixture phases of fcc and scc phases (PtFe-mix) by hydrogen-assisted calcination for the first time. By benchmarking the HER activity, PtFe-mix exhibits excellent activity in 1.0 m KOH, requiring an overpotential of 28 mV to achieve 10 mA cm-2 , which is better than the commercial Pt/C (34 mV). PtFe-mix also possesses remarkable stability up to 24 h. Density functional theory calculations further verify that PtFe-mix shows a more suitable d-band center and lower energy barrier for the initial water dissociation, facilitating the HER process. This work provides a meaningful strategy to design PtFe-based catalysts with efficient activity for hydrogen evolution.

MnOx Film-Coated NiFe-LDH Nanosheets on Ni Foam as Selective Oxygen Evolution Electrocatalysts for Alkaline Seawater Oxidation.

Compared to freshwater electrolysis, seawater electrolysis to produce hydrogen is preferable and more promising, but this technology is plagued by the electrode's corrosion and oxidative reactions of the competitive Cl- ion on the anode. To develop efficient oxygen evolution reaction (OER) catalysts for seawater electrolysis, the ultrathin MnOx film-covered NiFe-layered double-hydroxide nanosheet array is directly assembled on Ni foam (MnOx/NiFe-LDH/NF) by hydrothermal and electrodeposition in turn. This catalyst demonstrates excellent OER-selective activity in alkaline saline electrolytes. In 1 M KOH/0.5 M NaCl and 1 M KOH/seawater electrolytes, MnOx/NiFe-LDH/NF exhibits lower overpotentials at 100 mA cm-2 (η100 values of 265 and 276 mV, respectively) and Tafel slopes (73 and 77 mV decade-1, respectively) than does the NiFe-LDH/NF electrode (η100 values of 298 and 327 mV and Tafel slopes of 91 and 140 mV decade-1, respectively). In alkaline saline solutions, the stability and durability of the former are also better than those of the latter. The good OER selectivity and catalytic performance are attributed to the MnOx overlayer that selectively blocks Cl- anions from approaching catalytic centers, and the good conductivity, fast kinetics, more oxygen vacancies, and abundant active sites of MnOx/NiFe-LDH/NF. The robust stability is due to the enhanced resistance for Cl- corrosion stemming from the MnOx protective film. Hence, MnOx/NiFe-LDH/NF can act as a promising OER electrocatalyst for alkalized natural seawater electrolysis.

Polyaniline functionalized CoAl-layered double hydroxide nanosheets as a platform for the electrochemical detection of carbaryl and isoprocarb.

The preparation of the polyaniline/CoAl-layered double hydroxide composite (PANI/CoAl-LDH) is presented by ultrasonic mixing the uniform PANI- and CoAl-LDH-building blocks, both of which are synthesized in a microemulsion system. Due to the improved surface area, increased adsorptive and catalytic sites, and enhanced conductivity, the PANI/CoAl-LDH-modified glassy carbon electrode (GCE) delivers rapid electron-transfer and mass-transfer between the substrate electrode and analytes. Consequently, PANI/CoAl-LDH/GCE demonstrates outstanding electrocatalytic activity toward carbaryl and isoprocarb with good selectivity, stability, and reproducibility. The amperometric sensor gives rise to a wide linear range of 0.1 ~ 150 µM for both carbaryl and isoprocarb at 0.19 and 0.39 V (vs. SCE), respectively. Their limits of detection are respectively 6.8 and 8.1 nM. This sensor is successfully used for the determination of carbaryl and isoprocarb pesticides in real vegetable samples with a relative standard deviation below 4%.

Size-dependent light scattering of CoOOH nanoflakes for convenient and sensitive detection of alkaline phosphatase in human serum.

As a natural enzyme, alkaline phosphatase (ALP) plays an essential role in clinicopathological examinations and biomedical research, and is capable of hydrolyzing the phosphate group of l-ascorbic acid-2-phosphate (AAP) to yield l-ascorbic acid (L-AA). L-AA reduced cobalt oxyhydroxide (CoOOH) nanoflakes to Co2+ , leading to a smaller size and weaker light scattering, which could be monitored by electron microscopic images and optical spectra. The indirect detection of ALP was achieved by the reduced light scattering signal of CoOOH nanoflakes. Under optimal conditions, the decrease in scattering intensity was proportional to the ALP concentration over the range 0.1-160 U/L and the detection limit was 0.034 U/L (3σ/k). Compared with other assays, this proposed light scattering method was more convenient and economic for ALP sensing. The method was successfully applied to ALP analysis in human serum samples, and was similar to the results obtained by commercial kits.

Simultaneous determination of eight neonicotinoid insecticides, fipronil and its three transformation products in sediments by continuous solvent extraction coupled with liquid chromatography-tandem mass spectrometry.

Neonicotinoids (NEOs) and fipronil (FIP) are insecticides that are widely used in modern agriculture and have received considerable attention in recent years due to their adverse effects on non-target organisms in the environment. In the present study, a new method to simultaneously detect eight common NEO insecticides and FIP and its three transformation products (FIPs) in sediments was developed using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) based on a combined pretreatment of continuous solvent extraction (CSE) and solid phase extraction (SPE). Under optimized conditions, 5.0 g of freeze-dried sediment samples were initially extracted with methanol (20 mL)-methanol (15 mL)-water (20 mL) in sequence, and then the extract was cleaned with hydrophilic-lypophilic balance SPE cartridges, and HPLC-MS/MS analysis was conducted. The established method was validated to be sensitive, linear, accurate, and precise. The limits of detection (LOD) and limits of quantification (LOQ) of target compounds were 0.012-0.055 µg/kg d.w and 0.031-0.091 µg/kg d.w, respectively. Good linearity (R2 > 0.990) was observed between 4.0 × 10-2 and 20.0 µg/kg d.w. The recovery rates of all target insecticides were between 75.5% and 98.5%, and the relative standard deviations (RSD) were all less than 15.0% at the low, medium, and high spiked levels. Finally, the optimized method was applied to analyze 12 target insecticides in the sediments obtained from Jiaozhou Bay of China and its main inflow rivers. Acetamiprid, thiamethoxam, fipronil sulfide, and fipronil sulfone were detected in the river sediment samples at the concentration from

Amperometric sensing of catechol by using a nanocomposite prepared from Ag/Ag2O nanoparticles and N,S-doped carbon quantum dots.

This work describes the synthesis of a nanocomposite consisting of Ag2O, silver nanoparticles and N,S-doped carbon quantum dots (Ag2O/Ag@NS-CQD). The NS-CQD were prepared by hydrothermal treatment of p-aminobenzenesulfonic acid. They act as both the reducing and stabilizing agent for synthesis of Ag2O/Ag@NS-CQD. The composite was characterized by UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The glassy carbon electrode (GCE) was modified by coating it with Ag2O/Ag@NS-CQD. It exhibits excellent amperometric response to catechol, typically at a low working potential of around 0.25 V. Under the best experimental conditions, the sensor has a wide linear response (0.2 to 180 µM) and a low detection limit (13 nM; at S/N = 3). The method was applied to analysis of spiked water samples and gave satisfactory results. Graphical abstract Schematic representation of the preparation of the Ag/Ag2O@N,S-doped carbon quantum dots composite using p-aminobenzenesulfonic acid and silver nitrate as the starting materials. The corresponding modified glassy carbon electrode exhibits the excellent amperometric sensing performance toward catechol at pH 7.0 with low detection limit and good selectivity.

Band structure and dispersion engineering of strongly coupled plasmon-phonon-polaritons in graphene-integrated structures.

We theoretically investigate the polaritonic band structure and dispersion properties of graphene using transfer matrix methods, with strongly coupled graphene plasmons (GPs) and molecular infrared vibrations as a representative example. Two common geometrical configurations are considered: graphene coupled subwavelength dielectric grating (GSWDG) and graphene nanoribbons (GNR). By exploiting the dispersion and the band structure, we show the possibility of tailoring desired polaritonic behavior in each of the two configurations. We compare the strength of coupling occurring in both structures and find that the interaction is stronger in GNR than that of GSWDG structure as a result of the stronger field confinement of the edge modes. The band structure and dispersion analysis not only sheds light on the physics of the hybridized polariton formation but also offers insight into tailoring the optical response of graphene light-matter interactions for numerous applications, such as biomolecular sensing and detection.

Amorphous diamond-structured photonic crystal in the feather barbs of the scarlet macaw.

Noniridescent coloration by the spongy keratin in parrot feather barbs has fascinated scientists. Nonetheless, its ultimate origin remains as yet unanswered, and a quantitative structural and optical description is still lacking. Here we report on structural and optical characterizations and numerical simulations of the blue feather barbs of the scarlet macaw. We found that the sponge in the feather barbs is an amorphous diamond-structured photonic crystal with only short-range order. It possesses an isotropic photonic pseudogap that is ultimately responsible for the brilliant noniridescent coloration. We further unravel an ingenious structural optimization for attaining maximum coloration apparently resulting from natural evolution. Upon increasing the material refractive index above the level provided by nature, there is an interesting transition from a photonic pseudogap to a complete bandgap.

Unusual electromagnetic scattering by cylinders of topological insulator.

Topological insulators (TIs) show unusual optical responses resulting from a topological magnetoelectric (TME) effect. In this paper, we study theoretically the scattering of electromagnetic waves by circular TI cylinders. In certain configurations, the bulk scattering can be suppressed, leading to strong scattering in the backward direction in both Rayleigh and Mie scattering regimes due to the TME effect. At antiresonances, an interesting filed trapping phenomenon is found which is absent in conventional dielectric cylinders.

Organic carbon in wet deposition of an urbanized coastal bay, North China: Flux, sources and biogeochemical implications.

The process of atmospheric organic carbon (OC) entering the ocean through wet deposition plays a crucial role in the global carbon cycle. To gain insights into the biogeochemical dynamics of OC at the land-sea margin, we conducted an extensive four-year investigation on precipitation OC in Jiaozhou Bay (JZB). The results showed that the volume-weighted mean concentration of particulate OC (POC) and dissolved OC (DOC) in precipitation were 0.38 and 2.06 mg C L-1 with an average wet deposition flux of OC for 2666.5 mg C m-2 yr-1. The source of POC in precipitation is predominantly by the C3 plant emission and burning and fossil fuel combustion. Wet deposition contributed 986.6 t yr-1 of OC of which 506.3 t yr-1 of bioavailable DOC, which could have significant implications for carbon cycle in the JZB. This study could enhance the understanding of the marine atmospheric OC in coastal areas.

Unraveling the crucial contribution of additive chromate to efficient and stable alkaline seawater oxidation on Ni-based layered double hydroxides.

Seawater electrolysis to generate hydrogen offers a clean, green, and sustainable solution for new energy. However, the catalytic activity and durability of anodic catalysts are plagued by the corrosion and competitive oxidation reactions of chloride in high concentrations. In this study, we find that the additive CrO42- anions in the electrolyte can not only promote the formation and stabilization of the metal oxyhydroxide active phase but also greatly mitigate the adverse effect of Cl- on the anode. Linear sweep voltammetry, accelerated corrosion experiments, corrosion polarization curves, and charge transfer resistance results indicate that the addition of CrO42- distinctly improves oxygen evolution reaction (OER) kinetics and corrosion resistance in alkaline seawater electrolytes. Especially, the introduction of CrO42- even in the highly concentrated NaCl (2.5 M) electrolyte prolongs the durability of NiFe-LDH to almost five times the case without CrO42-. Density functional theory calculations also reveal that the adsorption of CrO42- can tune the electronic configuration of active sites of metal oxyhydroxides, enhance conductivity, and optimize the intermediate adsorption energies. This anionic additive strategy can give a better enlightenment for the development of efficient and stable oxygen evolution reactions for seawater electrolysis.

Thermal Shock Synthesis for Loading Sub-2 nm Ru Nanoclusters on Titanium Nitride as a Remarkable Electrocatalyst toward Hydrogen Evolution Reaction.

Heterogeneous catalysts embracing metal entities on suitable supports are profound in catalyzing various chemical reactions, and substantial synthetic endeavors in metal-support interaction modulation are made to enhance catalytic performance. Here, it is reported the loading of sub-2 nm Ru nanocrystals (NCs) on titanium nitride support (HTS-Ru-NCs/TiN) via a special Ru-Ti interaction using the high-temperature shock (HTS) method. Direct dechlorination of the adsorbed RuCl3, ultrafast nucleation process, and short coalescence duration at ultrahigh temperatures contribute to the immobilization of Ru NCs on TiN support via producing the Ru-Ti interfacial perimeter. HTS-Ru-NCs/TiN shows remarkable activity toward hydrogen evolution reaction (HER) in alkaline solution, yielding ultralow overpotentials of 16.3 and 86.6 mV to achieve 10 and 100 mA cm-2, respectively. The alkaline and anion exchange membrane water electrolyzers assembled using HTS-Ru-NCs/TiN yield 1.0 A cm-2 at 1.65 and 1.67 V, respectively, which validate its applicability in the hydrogen production industry. Theoretical simulations reveal the favorable formation of Ru─O and Ti─H bonds at the interfacial perimeters between Ru NCs and TiN, which accelerates the prerequisite water dissociation kinetics for enhanced HER activity. This exemplified work motivates the design of specific interfacial perimeters via the HTS strategy to improve the performance of diverse catalysis.

Boron modification promoting electrochemical surface reconstruction of NiFe-LDH for efficient and stable freshwater/seawater oxidation catalysis.

Transition metal-based electrocatalysts generally take place surface reconstruction in alkaline conditions, but little is known about how to improve the reconstruction to a highly active oxyhydroxide surface for an efficient and stable oxygen evolution reaction (OER). Herein, we develop a strategy to accelerate surface reconstruction by combining boron modification and cyclic voltammetry (CV) activation. Density functional theory calculations and in-situ/ex-situ characterizations indicate that both B-doping and electrochemical activation can reduce the energy barrier and contribute to the surface evolution into highly active oxyhydroxides. The formed oxyhydroxide active phase can tune the electronic configuration and boost the OER process. The reconstructed catalyst of CV-B-NiFe-LDH displays excellent alkaline OER performance in freshwater, simulated seawater, and natural seawater with low overpotentials at 100 mA cm-2 (η100: 219, 236, and 255 mV, respectively) and good durability. This catalyst also presents outstanding Cl- corrosion resistance in alkalized seawater electrolytes. The CV-B-NiFe-LDH||Pt/C electrolyzer reveals prominent performance for alkalized freshwater/seawater splitting. This study provides a guideline for developing advanced OER electrocatalysts by promoting surface reconstruction.

Boosting urea-assisted water splitting over P-MoO2@CoNiP through Mo leaching/reabsorption coupling CoNiP reconstruction.

Combining the urea oxidation reaction (UOR) with the hydrogen evolution reaction (HER) is an effective technology for energy-saving hydrogen production. Herein, a bifunctional electrocatalyst with CoNiP nanosheet coating on P-doped MoO2 nanorods (P-MoO2@CoNiP) is obtained via a two-step hydrothermal followed a phosphorization process. The catalyst demonstrates exceptional alkaline HER performance due to the formation of MoO2 and the dissolution/absorption of Mo. Meanwhile, the inclusion of Co and P in the P-MoO2@CoNiP catalyst facilitated the formation of NiOOH, enhancing UOR performance. Density functional theory calculations reveal that the hydrogen adsorption Gibbs free energy (ΔGH*) of P-MoO2@CoNiP is closer to 0 eV than CoNiP, favoring the HER. The catalyst only needs -0.08 and 1.38 V to reach 100 mA cm-2 for catalyzing the HER and UOR, respectively. The full urea electrolysis system driven by P-MoO2@CoNiP requires 1.51 V to achieve 100 mA cm-2, 120 mV lower than the traditional water electrolysis.

Tubular oxide microcavity with high-index-contrast walls: Mie scattering theory and 3D confinement of resonant modes.

Tubular oxide optical microcavities with thin walls (< 100 nm) have been fabricated by releasing pre-stressed Y2O3/ZrO2 bi-layered nanomembranes. Optical characterization demonstrates strong whispering gallery modes with a high quality-factor and fine structures in the visible range, which are due to their high-index-contrast property (high refractive index in thin walls). Moreover, the strong axial light confinement observed in rolled-up circular nanomembranes well agrees with our theoretical calculation by using Mie scattering theory. Novel material design and superior optical resonant properties in such self-rolled micro-tubular cavities promise many potential applications e.g. in optofluidic sensing and lasing.