Jahn-Teller Distortions Induced by in situ Li Migration in λ-MnO2 for Boosting Electrocatalytic Nitrogen Fixation.

Lithium-mediated electrochemical nitrogen reduction reaction (Li-NRR) completely eschews the competitive hydrogen evolution reaction (HER) occurred in aqueous system, whereas the continuous deposition of lithium readily blocks the active sites and further reduces the reaction kinetics. Herein, we propose an innovative in situ Li migration strategy to realize that Li substitutes Mn sites in λ-MnO2 instead of evolving into the dead Li. Comprehensive characterizations corroborate that the intercalation of Li+ at high voltage breaks the structural integrity of MnO6 octahedron and further triggers unique Jahn-Teller distortions, which promotes the spin state regulation of Mn sites to generate the ameliorative eg orbital configuration and accelerates N≡N bond cleavage via eg -σ and eg -π* interaction. To this end, the resulted cationic disordered LiMnO4 delivers the recorded highest NH3 yield rate of 220 µg h-1 cm-2 and a Faradaic efficiency (FE) 83.80 % in organic electrolyte.

Monolithic coherent LABS lidar based on an integrated transceiver array.

We demonstrate a monolithic frequency-modulated continuous-wave (FMCW) lidar chip with an integrated transceiver array based on lens-assisted beam steering (LABS) technology. It enables beam emitting, steering, receiving, and coherent detecting on a single chip with simultaneous distance and velocity detection. An integrated transceiver is designed with a composite structure of a Bragg grating in the middle and a U-shaped photodetector (PD) surrounding it. For a proof-of-concept demonstration, a chip with 2 × 2 switchable transceiver array is fabricated. A monolithic coherent LABS lidar system with a scanning angle of 2.86° and a scanning speed of 5.3 µs is implemented for 5 m ranging and 0.45 m/s velocity detection.

Monolithic transceiver for lens-assisted beam-steering Lidar.

We demonstrate a monolithic transceiver based on a CMOS-compatible silicon photonic platform for lens-assisted beam-steering (LABS) light detecting and ranging (Lidar) application. By implementing an on-chip two-dimensional transceiver array and off-chip lens, beam emitting, steering, and receiving are realized simultaneously on a single chip. The transceiver is designed with a structure of a U-shaped vertical Ge photodetector surrounding a grating for high-efficiency light transmission and reception. The on-chip photodetector has a bandwidth of 87 MHz, a responsivity of 0.3A/W, and a detection sensitivity of -20dBm. For proof-of-concept demonstration, a time-of-flight Lidar system is achieved for target ranging with a detection distance of 5.2 m, a scanning angle of 2.86°, and a scanning speed of 5.3µs . This work demonstrates a feasible solution to integrated Lidar with beam emitting and receiving on one single chip based on LABS.

Unveiling Electrochemical Urea Synthesis by Co-Activation of CO2 and N2 with Mott-Schottky Heterostructure Catalysts.

Electrocatalytic C-N bond coupling to convert CO2 and N2 molecules into urea under ambient conditions is a promising alternative to harsh industrial processes. However, the adsorption and activation of inert gas molecules and then the driving of the C-N coupling reaction is energetically challenging. Herein, novel Mott-Schottky Bi-BiVO4 heterostructures are described that realize a remarkable urea yield rate of 5.91 mmol h-1 g-1 and a Faradaic efficiency of 12.55 % at -0.4 V vs. RHE. Comprehensive analysis confirms the emerging space-charge region in the heterostructure interface not only facilitates the targeted adsorption and activation of CO2 and N2 molecules on the generated local nucleophilic and electrophilic regions, but also effectively suppresses CO poisoning and the formation of endothermic *NNH intermediates. This guarantees the desired exothermic coupling of *N=N* intermediates and generated CO to form the urea precursor, *NCON*.

Bottom-up Design of Bimetallic Cobalt-Molybdenum Carbides/Oxides for Overall Water Splitting.

Earth-abundant transition-metal-based catalysts for electrochemical water splitting are critical for sustainable energy schemes. In this work, we use a rational design method for the synthesis of ultrasmall and highly dispersed bimetallic CoMo carbide/oxide particles deposited on graphene oxide. Thermal conversion of the molecular precursors [H3 PMo12 O40 ], Co(OAc)2 ⋅4 H2 O and melamine in the presence of graphene oxide gives the mixed carbide/oxide (Co6 Mo6 C2 /Co2 Mo3 O8 ) nanoparticle composite deposited on highly dispersed, N,P-doped carbon. The resulting composite shows outstanding electrocatalytic water-splitting activity for both the oxygen evolution and hydrogen evolution reaction, and superior performance to reference samples including commercial 20 % Pt/C & IrO2 . Electrochemical and other materials analyses indicate that Co6 Mo6 C2 is the main active phase in the composite, and the N,P-doping of the carbon matrix increases the catalytic activity. The facile design could in principle be extended to multiple bimetallic catalyst classes by tuning of the molecular metal oxide precursor.

Controlled Synthesis of Silver Micro/Nano Leaves for Oxygen Reduction and CO2 Reduction.

In this study, three different Ag micro/nano leaves were successfully synthesized through a galvanic displacement reaction by adjusting the concentration of Ag+. The catalytic activities of the prepared Ag micro/nano leaves toward ORR showed strong dependence on their morphology. An optimal concentration of Ag+ can result in a well-defined Ag micro/nano leaves with both crystallization and surface area, which showed the best activity towards ORR in alkaline media. In addition, the prepared Ag micro/nano leaves also showed high activity towards CO2 reduction, which required a potential of -0.8 V versus RHE to selectively convert CO2 to CO with the faradaic efficiency at about 20%. Compared with the Ag plate at the same overpotential, the FE has increased by 5-fold.

Nitrogen-rich core-shell structured particles consisting of carbonized zeolitic imidazolate frameworks and reduced graphene oxide for amperometric determination of hydrogen peroxide.

Core-shell structured particles were prepared from carbonized zeolitic imidazolate frameworks (ZIFs) and reduced graphene oxide (rGO). The particles possess a nitrogen content of up to 10.6%. The loss of nitrogen from the ZIF is avoided by utilizing the reduction and agglomeration of graphene oxide with suitable size (>2 µm) during pyrolysis. The resulting carbonized ZIF@rGO particles were deposited on a glassy carbon electrode to give an amperometric sensor for H2O2, typically operated at a voltage of -0.4 V (vs. Ag/AgCl). The sensor has a wide detection range (from 5 × 10-6 to 2 × 10-2 M), a 3.3 µM (S/N = 3) detection limit and a 0.272 µA·µM-1·cm-2 sensitivity, much higher than that of directly carbonized ZIFs. The sensor material was also deposited on a screen-printed electrode to explore the possibility of application. Graphical abstract Nitrogen doped carbon (NC) derived from carbonized zeolitic imidazolate frameworks is limited because of low nitrogen content. Here, nitrogen-rich NC@reduced graphene oxide (rGO) core-shell structured particles are described. The NC@rGO particles show distinctly better H2O2 detection performance than NC.

A Colorimetric Fluorescent Probe for SO2 Derivatives-Bisulfite and Sulfite at Nanomolar Level.

A colorimetric fluorescent probe with fluorescence emission feature sensitive to SO2 derivatives, i.e. bisulfite (HSO3-) and sulfite (SO32-), was developed based on the HSO3-/SO32--mediated nucleophilic addition reaction of the probe that. This probe exhibited SO32- sensing ability with detection limit down to 46 nM and desired selectivity over other reference anions and redox species. The preliminary fluorescence bioimaging experiments have validated the practicability of the as-prepared probe for SO2 derivatives sensing in living cells.

Mixed-Valent Mn16-Containing Heteropolyanions: Tuning of Oxidation State and Associated Physicochemical Properties.

The two 16-manganese-containing, Keggin-based 36-tungsto-4-silicates [Mn(III)10Mn(II)6O6(OH)6(PO4)4(A-α-SiW9O34)4](28-) (1) and [Mn(III)4Mn(II)12(OH)12(PO4)4(A-α-SiW9O34)4](28-) (2) have been prepared by reaction of the trilacunary Keggin precursor [A-α-SiW9O34](10-) with either Mn(OOCCH3)3·2H2O (for 1) or MnCl2·4H2O (for 2), in aqueous phosphate solution at pH 9. Polyanions 1 and 2 comprise mixed-valent, cationic {Mn(III)10Mn(II)6O6(OH)6}(24+) and {Mn(III)4Mn(II)12(OH)12}(24+) cores, respectively, encapsulated by four phosphate groups and four {SiW9} units in a tetrahedral fashion. Both polyanions were structurally and compositionally characterized by single-crystal XRD, IR, thermogravimetric analysis, and X-ray absorption spectroscopy. Furthermore, studies were performed probing the magnetic, electrochemical, oxidation catalytic, and Li-ion battery performance of 1 and 2.

Sequential Synthesis of 3 d-3 d, 3 d-4 d, and 3 d-5 d Hybrid Polyoxometalates and Application to the Electrocatalytic Oxygen Reduction Reactions.

The Co7 (AlePy)2 polyoxometalate, which encloses a {(PW9 )2 Co(II) 7 } core covalently bound to two free aminopyridine groups through bisphosphonate ligands (AlePy), has been isolated. It can be used as a precursor, allowing the synthesis of heterometallic hybrid compounds, as illustrated by the characterization of cobalt/zinc (Co7 (AlePyZn)2 ), cobalt/palladium (Co7 (AlePyPd)2 ), and cobalt/platinum (Co7 (AlePyPt)2 ) species. A composite based on the water-insoluble precious metal-free Co7 (AlePyZn)2 compound and the low-cost carbon material Vulcan XC-72 has been selected as a cathode material (Co7 Zn/C) for oxygen reduction reaction studies. The electrocatalytic performances of the Co7 Zn/C hybrids were assessed at neutral and basic pH, showing that Co7 Zn/C exhibits high selectivity for the four-electron reduction of O2 . Moreover, its durability is superior to that of a commercial Pt/C catalyst with 20 % loading. Also, comparative studies performed in the presence of methanol have indicated that Co7 Zn/C has a much better tolerance to the crossover effect than Pt/C. Altogether, these results indicate for the first time that, even in neutral media, polyoxometalate/carbon composites can represent low-cost oxygen reduction catalysts that can function stably, for a long time, and with high performance.

Cu2ZnSnS4-Ag2S Nanoscale p-n Heterostructures as Sensitizers for Photoelectrochemical Water Splitting.

A cation exchange-based route was used to produce Cu2ZnSnS4 (CZTS)-Ag2S nanoparticles with controlled composition. We report a detailed study of the formation of such CZTS-Ag2S nanoheterostructures and of their photocatalytic properties. When compared to pure CZTS, the use of nanoscale p-n heterostructures as light absorbers for photocatalytic water splitting provides superior photocurrents. We associate this experimental fact to a higher separation efficiency of the photogenerated electron-hole pairs. We believe this and other type-II nanoheterostructures will open the door to the use of CZTS, with excellent light absorption properties and made of abundant and environmental friendly elements, to the field of photocatalysis.

Ti2-Containing 18-Tungsto-2-Arsenate(III) Monolacunary Host and the Incorporation of a Phenylantimony(III) Guest.

The novel Ti2-containing, sandwich-type 18-tungsto-2-arsenate(III) [(Ti(IV)O)2(α-As(III)W9O33)2](14-) (1) was successfully synthesized by the reaction of [TiO](2+) species with [α-As(III)W9O33](9-). The monolacunary polyanion 1 is solution-stable, and a further reaction with 1 equiv of phenylantimony(III) dichloride resulted in [C6H5Sb(III)(Ti(IV)O)2(α-As(III)W9O33)2](12-) (2). Both polyanions 1 and 2 were structurally characterized in the solid state and solution. Electrochemical studies were also performed on both polyanions.

A novel hysteroscopic hook for extracting retained contraceptive intrauterine devices under direct vision.

OBJECTIVE: The study evaluated the efficacy of removing retained intrauterine devices (IUDs) under direct vision using a novel hysteroscopic hook. METHODS: In a retrospective observational study, 83 patients (group 1) underwent IUD extraction using a hysteroscopic IUD removal hook (HIRH) and 60 patients (group 2) underwent traditional hysteroscopic IUD extraction. We recorded the blood loss, operation time and success rate. RESULTS: The operation time was shorter (10.7 vs. 17.7 min; p < 0.001) and the success rate higher in group 1 compared with group 2 (odds ratio 1.09; p = 0.027). CONCLUSIONS: The HIRH is an effective, simple, inexpensive and durable tool for the direct visual removal of IUDs partially embedded in the endometrium and for damaged IUDs.

Multinuclear cobalt(II)-containing heteropolytungstates: structure, magnetism, and electrochemistry.

Interaction of the trilacunary Keggin polyanions [A-α-XW9O34](10-) (X = Si(IV), Ge(IV)) with Co(II) and phosphate ions in aqueous, basic media and under mild heating leads to the formation of the tetrameric, Co16-containing heteropolytungstates [{Co4(OH)3PO4}4(A-α-XW9O34)4](32-) (X = Si(IV), Ge(IV)). Both polyanions were characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, and thermogravimetric and elemental analyses. Furthermore, the electrochemical and magnetic properties of these isostructural polyanions were investigated.

Graphene-CdS quantum dots-polyoxometalate composite films for efficient photoelectrochemical water splitting and pollutant degradation.

rGO-CdS-H2W12 nanocomposite film was successfully fabricated by a layer-by-layer self-assembly method. The composite film was characterized by techniques such as UV-Vis spectra, XPS, and AFM. The composite film showed high photoelectronic response under the illumination of sunlight. Both current-voltage curves and photocurrent transient measurements demonstrated that the photocurrent response of the rGO-CdS-H2W12 composite film was enhanced five-fold compared with CdS film. This can be attributed to the photoinduced electron transfer between CdS, H2W12 and rGO, which promotes the charge separation efficiency of CdS. The introduction of GO enhanced the charge separation and transportation. More importantly, various pollutants can be treated as electron donors, and can thus be degraded and produce hydrogen at the same time, at a low bias voltage under the irradiation of solar light.

The Influence of Supervisor-Postgraduate Relationship on Master's Students' Research Learning Engagement-The Mediating Effect of Academic Aspiration.

Research learning engagement is the basic element of master's students' innovation output, and the supervisor is the first responsible body for master's students' cultivation. Exploring the influence of the supervisor-postgraduate relationship on master's students' research learning engagement, with a focus on the mediating role of academic aspiration, is of great significance for the improvement of master's students' cultivation quality. We surveyed 569 master's students at a university in Wuhan, China, using 3 measurement tools: the Supervisor-Postgraduate Relationship Scale, the Research Learning Engagement Scale, and the Academic Aspirations Scale. The results showed that: (1) The supervisor-postgraduate relationship positively and significantly predicted master's students' research learning engagement, and academic aspiration played a fully mediating role in the process. (2) There were differences in the effects of the three dimensions of the supervisor-postgraduate relationship on master's students' research learning engagement, with research collaboration having the greatest total effect on the impact of master's students' research learning engagement. This study emphasizes the importance of the supervisor-postgraduate relationship and academic aspirations and provides some implications for improving the research learning engagement of master's students.

The ionic liquids upon perchlorate to promote the C-C/C-O bonds cleavage in alkali lignin under photothermal synergism.

Transforming lignin into aromatic monomers is critically attractive to develop green and sustainable energy supplies. However, the usage of the additional catalysts like metal or base/acid is commonly limited by the caused repolymerized and environmental issues. The key step is to mediate electron transfer in lignin to trigger lignin C-C/C-O bonds cleavage without the catalysts mentioned above. Here, we report that the ionic liquids [BMim][ClO4] was found to trigger lignin electron transfer to cleave the C-C/C-O bonds for aromatic monomers without any additional catalyst. The proton transfer from [BMim]+ to [ClO4]- could polarize the anion and decrease its structure stability, upon which the active hydroxyl radical generated and induced lignin C-C/C-O bonds fragmentation via free radical-mediated routes with the assistance of photothermal synergism. About 4.4 wt% yields of aromatic monomers, mainly composed of vanillin and acetosyringone, are afforded in [BMim][ClO4] under UV-light irradiation in the air at 80 °C. This work opens the way to produce value-added aromatic monomers from lignin using an eco-friendly, energy-efficient, and simple route that may contribute to the sustainable utilization of renewable natural resources.

Carbon quantum dots as novel sensitizers for photoelectrochemical solar hydrogen generation and their size-dependent effect.

As a result of global energy needs, much research has been devoted to the conversion of solar energy to various usable forms, such as chemical energy in the form of hydrogen via water splitting. To make the conversion methods efficient, economically practical, and industrially scalable, sensitizers capable of utilizing visible and near infrared (IR) light need to be developed. Herein, water-soluble, colloidally stable carbon quantum dots (CQDs) are successfully synthesized by a facile one-step alkali-assisted electrochemical method. Owing to their broad visible light absorption, upconversion luminescence properties and efficient electron injection to TiO2, these CQDs can be used as the sensitizer for photoelectrochemical cells and show an optimized photocurrent of 1.2 mA cm(-2) at 0 V versus Ag/AgCl under 100 mW cm(-2) simulated sunlight. The above results indicate that the elementally abundant and environmentally friendly CQDs, as a novel sensitizer, can surely be employed to make full use of the visible spectrum of sunlight for their application in photovoltaic devices.

Facile decoration of Au nanoparticles on CdS nanorods by polyoxometalate with enhanced photocatalytic activities toward hydrogen evolution.

The tri-component hybrid CdS nanorods (NRs)/Au nanoparticles (NPs)@polyoxometalate (POM) was successfully prepared by a facile, efficient and green method. The structural properties and component analysis were studied by Transmission electron microscopy (TEM), X-ray Diffraction (XRD) and UV-Vis spectra. The POMs sever as not only reductant and bridge molecules, but also as co-catalyst to play an important role in the photocatalytic process. The as-prepared nanohybrid shows obviously enhanced photocatalytic activity toward photocatalytic evolution of hydrogen.

Ternary PtZrNi nanorods for efficient multifunctional electrocatalysis towards oxygen reduction and alcohol oxidation.

Pt-based alloys with precise structure and composition design have been considered to be effective and robust novel electrocatalysts for fuel cells. Whereas, the sluggish kinetics of oxygen reduction reaction (ORR) and low intrinsic activity of Pt limited their real application on a large scale. Herein, a novel ternary PtZrNi nanorods (PtZrNi NRs) was synthesized via a facile wet-chemical method to achieve high electrocatalytic performance for both ORR and alcohol oxidation reaction owing to the synergism of chosen three elements and prominent one-dimensional morphology. Specifically, the PtZrNi NRs show enhanced mass and specific activities of 0.755 A mgPt-1 and of 0.97 mA/cm2 at 0.9 VRHE towards ORR in acidic media, which are 4.7 and 4.4 times of those of commercial Pt/C, respectively. Additionally, in alkaline media, the PtZrNi NRs also exhibit superior ORR mass and specific activities of 3.216 A mgPt-1and 4.13 mA/cm2, enhanced by 34.6 and 31.3 times compared with those of commercial Pt/C, respectively. The PtZrNi NRs retain the nanorod shape well without agglomeration after an accelerated durability test (20000 cycles). This work may offer a new perspective for engineering high-performance Pt-based electrocatalysts for commercial fuel cells.