Electrocatalytic Synthesis of Urea: An In-depth Investigation from Material Modification to Mechanism Analysis.

Industrial urea synthesis production uses NH3 from the Haber-Bosch method, followed by the reaction of NH3 with CO2, which is an energy-consuming technique. More thorough evaluations of the electrocatalytic C-N coupling reaction are needed for the urea synthesis development process, catalyst design, and the underlying reaction mechanisms. However, challenges of adsorption and activation of reactant and suppression of side reactions still hinder its development, making the systematic review necessary. This review meticulously outlines the progress in electrochemical urea synthesis by utilizing different nitrogen (NO3 -, N2, NO2 -, and N2O) and carbon (CO2 and CO) sources. Additionally, it delves into advanced methods in materials design, such as doping, facet engineering, alloying, and vacancy introduction. Furthermore, the existing classes of urea synthesis catalysts are clearly defined, which include 2D nanomaterials, materials with Mott-Schottky structure, materials with artificially frustrated Lewis pairs, single-atom catalysts (SACs), and heteronuclear dual-atom catalysts (HDACs). A comprehensive analysis of the benefits, drawbacks, and latest developments in modern urea detection techniques is discussed. It is aspired that this review will serve as a valuable reference for subsequent designs of highly efficient electrocatalysts and the development of strategies to enhance the performance of electrochemical urea synthesis.

Additives for Aqueous Zinc-Ion Batteries: Recent Progress, Mechanism Analysis, and Future Perspectives.

Aqueous zinc-ion batteries (ZIBs) stand out as a promising next-generation electrochemical energy storage technology, offering notable advantages such as high specific capacity, enhanced safety, and cost-effectiveness. However, the application of aqueous electrolytes introduces challenges: Zn dendrite formation and parasitic reactions at the anode, as well as dissolution, electrostatic interaction, and by-product formation at the cathode. In addressing these electrode-centric problems, additive engineering has emerged as an effective strategy. This review delves into the latest advancements in electrolyte additives for ZIBs, emphasizing their role in resolving the existing issues. Key focus areas include improving morphology and reducing side reactions during battery cycling using synergistic effects of modulating anode interface regulation, zinc facet control, and restructuring of hydrogen bonds and solvation sheaths. Special attention is given to the efficacy of amino acids and zwitterions due to their multifunction to improve the cycling performance of batteries concerning cycle stability and lifespan. Additionally, the recent additive advancements are studied for low-temperature and extreme weather applications meticulously. This review concludes with a holistic look at the future of additive engineering, underscoring its critical role in advancing ZIB performance amidst the complexities and challenges of electrolyte additives.

Three-dimensional analysis of puncture needle path through safety triangle approach PLD and design of puncture positioning guide plate.

OBJECTIVE: In this study, the three-dimensional relationship between the optimal puncture needle path and the lumbar spinous process was discussed using digital technology. Additionally, the positioning guide plate was designed and 3D printed in order to simulate the surgical puncture of specimens. This plate served as an important reference for the preoperative simulation and clinical application of percutaneous laser decompression (PLD). METHOD: The CT data were imported into the Mimics program, the 3D model was rebuilt, the ideal puncture line N and the associated central axis M were developed, and the required data were measured. All of these steps were completed. A total of five adult specimens were chosen for CT scanning; the data were imported into the Mimics program; positioning guide plates were generated and 3D printed; a simulated surgical puncture of the specimens was carried out; an X-ray inspection was carried out; and an analysis of the puncture accuracy was carried out. RESULTS: (1) The angle between line N and line M was 42°~55°, and the angles between the line M and 3D plane were 1°~2°, 5°~12°, and 78°~84°, respectively; (2) As the level of the lumbar intervertebral disc decreases, the distance from point to line and point to surface changes regularly; (3) The positioning guide was designed with the end of the lumbar spinous process and the posterior superior iliac spine on both sides as supporting points. (4) Five specimens were punctured 40 times by using the guide to simulate surgical puncture, and the success rate was 97.5%. CONCLUSION: By analyzing the three-dimensional relationship between the optimal puncture needle path and the lumbar spinous process, the guide plate was designed to simulate surgical puncture, and the individualized safety positioning of percutaneous puncture was obtained.

L-cysteine-modified gold nanostars for SERS-based copper ions detection in aqueous media.

Gold nanostars coated with cysteine (Cys-AuNSs) were successfully synthesized and used in SERS-based copper ions (Cu(2+)) detection in aqueous media. The strong coordination ability of cysteine (Cys) with Cu(2+) and the resulting Cys-AuNSs-Cu complex formation led to AuNSs aggregation and the drastic change in intensity and strength of COOH band spectra. The aggregation of AuNSs yielded distinct SERS signals, which exhibited remarkable sensitivity and selectivity for Cu(2+) over other metal ions. Using this SERS-based sensing method, we have achieved a practical detection limit of 10 µM. Such AuNSs-based detection could provide promising alternative choices for future SERS-active AuNSs application.

Insight into the mechanism of selective catalytic reduction of NO(x) by propene over the Cu/Ti(0.7)Zr(0.3)O2 catalyst by Fourier transform infrared spectroscopy and density functional theory calculations.

The mechanism of selective catalytic reduction of NOx by propene (C3H6-SCR) over the Cu/Ti0.7Zr0.3O2 catalyst was studied by in situ Fourier transform infrared (FTIR) spectroscopy and density functional theory (DFT) calculations. Especially, the formation and transformation of cyanide (-CN species) during the reaction was discussed. According to FTIR results, the excellent performance of the Cu/Ti0.7Zr0.3O2 catalyst in C3H6-SCR was attributed to the coexistence of two parallel pathways to produce N2 by the isocyanate (-NCO species) and -CN species intermediates. Besides the hydrolysis of the -NCO species, the reaction between the -CN species and nitrates and/or NO2 was also a crucial pathway for the NO reduction. On the basis of the DFT calculations on the energy of possible intermediates and transition states at the B3LYP/6-311 G (d, p) level of theory, the reaction channel of -CN species in the SCR reaction was identified and the role of -CN species as a crucial intermediate to generate N2 was also confirmed from the thermodynamics view. In combination of the FTIR and DFT results, a modified mechanism with two parallel pathways to produce N2 by the reaction of -NCO and -CN species over the Cu/Ti0.7Zr0.3O2 catalyst was proposed.

Cubic CuFe2O4 Spinel with Octahedral Fe Active Sites for Electrochemical Dechlorination of 1,2-Dichloroethane.

CuFe2O4 spinel has been considered as a promising catalyst for the electrochemical reaction, while the nature of the crystal phase on its intrinsic activity and the kind of active site need to be further explored. Herein, the crystal phase-dependent catalytic behavior and the main active sites of CuFe2O4 spinel for electrochemical dechlorination of 1,2-dichloroethane are carefully studied based on the combination of experiments and theoretical calculations. Cubic and tetragonal CuFe2O4 are successfully prepared by a facile sol-gel method combined with high temperature calcination. Impressively, CuFe2O4 with the cubic phase shows a higher activity and ethylene selectivity compared to CuFe2O4 with the tetragonal phase, suggesting a significant facilitation of electrocatalytic performance by the cubic crystal structure. Moreover, the octahedral Fe atom on the surface of cubic CuFe2O4(311) is the active site responsible to produce ethylene with the energy barrier of 0.40 eV. This work demonstrates the significance of crystal phase engineering for the optimization of electrocatalytic performance and offers an efficient strategy for the development of advanced electrocatalysts.

Role of hydroxyl radicals and mechanism of Escherichia coli inactivation on Ag/AgBr/TiO2 nanotube array electrode under visible light irradiation.

A ternary Ag/AgBr/TiO(2) nanotube array electrode with enhanced visible-light activity was synthesized by a two-step approach including electrochemical process of anodization and an in situ photoassisted deposition strategy. The dramatically enhanced photoelectrocatalytic activity of the composite electrode was evaluated via the inactivation of Escherichia coli under visible light irradiation (λ>420 nm), whose performance of complete sterilization was much superior to other reference photocatalysts. PL, ESR, and radicals trapping studies revealed hydroxyl radicals were involved as the main active oxygen species in the photoelectrocatalytic reaction. The process of the damage of the cell wall and the cell membrane was directly observed by ESEM, TEM, and FTIR, as well as further confirmed by determination of potassium ion leakage from the killed bacteria. The present results pointed to oxidative attack from the exterior to the interior of the Escherichia coli by OH(•), O(2)(•-), holes and Br(0), causing the cell to die as the primary mechanism of photoelectrocatalytic inactivation.

Synthesis and photoinduced charge-transfer properties of a ZnFe2O4-sensitized TiO2 nanotube array electrode.

TiO2 nanotube arrays sensitized with ZnFe2O4 nano-crystals were successfully fabricated by a two-step process of anodization and a vacuum-assistant impregnation method followed by annealing. The sample was studied by an environmental scanning electron microscope, a transmission electron microscope, energy-dispersive X-ray analysis, and X-ray diffraction to characterize its morphology and chemical composition. Ultraviolet-visible (UV-vis) absorption spectra and a photoelectrochemical measurement approved that the ZnFe2O4 sensitization enhanced the probability of photoinduced charge separation and extended the range of the photoresponse of TiO2 nanotube arrays from the UV to visible region. In addition, the behaviors of photoinduced charge transfer in a TiO2 nanotube array electrode before and after sensitization by ZnFe2O4 nanocrystals were comparatively studied. The photoluminescence of the TiO2 nanotube array electrode became suppressed, and the surface photovoltage responses on the spectrum were significantly enhanced after the introduction of ZnFe2O4 nanocrystals. The transfer dynamics of the photoinduced charges were observed directly by a transient photovoltage measurement, which revealed a fast charge separation at the interface between ZnFe2O4 nanocrystals and TiO2 nanotubes upon light excitation.

Current Progress of Electrocatalysts for Ammonia Synthesis Through Electrochemical Nitrogen Reduction Under Ambient Conditions.

Ammonia, one of the most important chemicals and carbon-free energy carriers, is mainly produced by the traditional Haber-Bosch process operated at high pressure and temperature, which results in massive energy consumption and CO2 emissions. Alternatively, the electrocatalytic nitrogen reduction reaction to synthesize NH3 under ambient conditions using renewable energy has recently attracted significant attention. However, the competing hydrogen evolution reaction (HER) significantly reduces the faradaic efficiency and NH3 production rate. The design of high-performance electrocatalysts with the suppression of the HER for N2 reduction to NH3 under ambient conditions is a crucial consideration for the development of electrocatalytic NH3 synthesis with high FE and NH3 production rate. Five kinds of recently developed electrocatalysts classified by their chemical compositions are summarized, with particular emphasis on the relationship between their optimal electrocatalytic conditions and NH3 production performance. Conclusions and perspectives are provided for the future design of high-performance electrocatalysts for electrocatalytic NH3 production. The Review can give practical guidance for the design of effective electrocatalysts with high FE and NH3 production rates.

Boosting interfacial charge transfer and electricity generation for levofloxacin elimination in a self-driven bio-driven photoelectrocatalytic system.

Recently, molybdenum disulfide (MoS2) has stimulated significant research interest as a promising electrode candidate in solar cells and energy conservation fields. Unfortunately, the short lower electron/hole migration lifetimes and easy agglomeration hamper its wide practical applications to some extent. Herein, interface engineering coupled with a bio-assisted photoelectrochemical (PEC) strategy is presented to construct a 0D MoS2 quantum dot (QD)/1D TiO2 nanotube electrode for pollutant elimination. Aimed at accelerating charge transfer over the 0D/1D composite interface, three types of coupling PEC models were developed to optimize the catalytic performance. The single chamber microbial fuel cell (SCMFC)-PEC integrated system was found to be the best alternative for levofloxacin (LEV) elimination (0.029 min-1), and the sequential SCMFC-PEC further realized the whole system self-running independently. In addition, the interfacial electron migration and LEV degradation pathways were thoroughly investigated by LC/TOF/MS coupled with density functional theory (DFT) calculations to clearly elucidate the electron transfer paths, LEV-attacked sites and mineralization pathways in a joint sequential SCMFC-PEC system. As such, the constructed self-recycling system provides a new platform for bio-photo-electrochemical utilization, which could exhibit promising potential in environmental purification.

Insight into the photocatalytic mineralization of short chain chlorinated paraffins boosted by polydopamine and Ag nanoparticles.

Short chain chlorinated paraffins (SCCPs) have attracted increasing attention recently due to their widespread occurrence and persistence in the environment, long-distance transport, and bioaccumulation and toxicity. For the sake of photocatalytic elimination of SCCPs, a kind of polydopamine (PDA) based photocatalyst, echinus-like Fe2O3@PDA-Ag hybrids have been synthesized via coating Fe2O3 with PDA by self-polymerization of dopamine and further loading silver nanoparticles by in situ reduction onto the surface of PDA shell. The photogenerated charges of Fe2O3@PDA-Ag hybrids exhibit long lifetime from transient photovoltage signal, which is of benefit to participate in various subsequent reaction processes before their recombination. Benefiting from the coating of PDA shell and the deposition of Ag nanoparticles, Fe2O3@PDA-Ag hybrids exhibit enhanced photocatalytic activity for the removel of SCCPs as investigated by the in situ Fourier transform infrared spectroscopy, 2.9 times as high as that of Fe2O3, due to the reactive OH radicals. The density functional theory simulation demonstrates the key mechanism of the formation of conjugate bond in the dechlorination process as well as the final product of HCl. The simulation indicates that there are no regularities for the H-abstraction but the dechlorination usually occurs in the adjacent Cl atoms next to the C with H-abstraction.

Hollow porous zinc cobaltate nanocubes photocatalyst derived from bimetallic zeolitic imidazolate frameworks towards enhanced gaseous toluene degradation.

Aiming at promoting the photocatalytic performance of spinel oxides, an efficient method of constructing hollow porous zinc cobaltate (ZnxCo3-xO4) nanocubes was established in this work. Bimetallic zeolitic imidazolate frameworks (ZIFs) were prepared through a facile self-assembly strategy, then hollow ZnxCo3-xO4 nanocubes were obtained by calcining the bimetallic ZIFs precursor. The structural features and optical properties of the ZnxCo3-xO4 nanocubes were comprehensively investigated by a series of characterization techniques. With higher specific surface area (about 100 m2 g-1), enhanced light absorbance in the whole range of 350-800 nm and lowered recombination of photogenerated electron-hole pairs, these hollow nanocubes demonstrated attractive photocatalytic activity in degrading gaseous toluene, superior to traditional stoichiometric ZnCo2O4 nanoparticles. The photocatalytic process and related mechanism of toluene degradation were further investigated with in situ Fourier transform infrared (FTIR) spectroscopy and electron paramagnetic resonance (EPR) techniques. Photo-induced O2- and holes were assigned as main reactive species in the photocatalytic system with hollow ZnxCo3-xO4 nanocubes.

Triple-shelled NiMn2O4 hollow spheres as an efficient catalyst for low-temperature selective catalytic reduction of NOx with NH3.

Unique triple-shelled NiMn2O4 hollow spheres are fabricated by a facile solvothermal method. Owing to its particular triple shell structure, the as prepared NiMn2O4 catalyst exhibits superior low-temperature NH3-SCR catalytic performance, achieving above 90% NOx conversion in the temperature range from 100 °C to 225 °C.

Rational design and synthesis of highly oriented copper-zinc ferrite QDs/titania NAE nano-heterojunction composites with novel photoelectrochemical and photoelectrocatalytic behaviors.

This work reported that novel highly oriented and vertically aligned stoichiometric copper- and zinc-based ferrites, i.e., Cu0.5Zn0.5Fe2O4 quantum dots (QDs) anchored with TiO2 nanotube array electrode (NAE) composites, with n-n nano-heterojunctions and highly effective simulated solar light harvesting could be successfully achieved via electrochemical anodization followed by a vacuum-assisted impregnation strategy. It has been observed that Cu0.5Zn0.5Fe2O4 QDs/TiO2 NAE composites exhibit distinctly enhanced visible light photoelectrocatalytic (PEC) performance toward the degradation of typical pollutants including sulfamethoxazole (SMX) and methylene blue (MB) as compared to that of pristine TiO2 NAEs, which can be attributed to the synergistic effect of heterostructures with strong interfacial interaction and abundant 1D nanotube array structures to facilitate efficient spatial charge separation and interfacial transfers. The cocatalyst-anchoring of ternary oxides with derived spinel crystal structures onto nanotube arrays forming novel nanocomposites have obviously achieved remarkably enhanced photoelectrochemical (PE) conversion efficiencies, up to a dedicated value of 3.75%, under visible light irradiation as compared to that of 0.88% for aligned standalone TiO2 NAEs. Transient absorption spectroscopy quantitatively indicated long-lived photo-holes with lifetimes exceeding 72.23 µs generated among Cu0.5Zn0.5Fe2O4 QDs/TiO2 NAE nanocomposites. Electron spinning resonance (ESR) demonstrated that more ˙O2- species derived from molecular uptake played the predominant role in the PEC oxidations of SMX and MB species. Moreover, the binding energy of the onset edge (Evf) and Fermi level (Ef) of Cu0.5Zn0.5Fe2O4 QDs/TiO2 NAEs indicated that Cu0.5Zn0.5Fe2O4 QDs modification could considerably enhance the visible light harvesting and adsorption properties of TiO2 NTs. Furthermore, Cu0.5Zn0.5Fe2O4 QDs/TiO2 NAEs achieved up to 50% PEC degradation efficiency and 52.4% COD removal with regard to practical textile wastewater when irradiated by simulated sunlight. This work has provided new insights into the molecular tailing and coupling of multiple spinels with TiO2 NTs possessing remarkable visible light harvesting and sensitization characteristics, which would offer a prospective strategy toward designing highly efficient and easily recyclable photocatalytic materials for environmental remediation and solar energy utilizations and conversions both simultaneously and standalone.

Upconversion carbon quantum dots as visible light responsive component for efficient enhancement of photocatalytic performance.

It finds that CQDs synthesized by hydrothermal method possess obvious upconversion properties that could transfer low energy photons to high energy photons, resulting in enhanced visible light response and utilization. Herein, carbon quantum dots (CQDs) modified TiO2 photocatylysts were successfully prepared by a facile sol-gel method. Photophysical and surficial properties of the as-prepared composite photocatalyst were investigated in details. Furthermore, photocatalytic performance was tested by degrading methylene blue (MB) under visible light irradiation. The degradation efficiency of methylene blue (MB) is as high as 90% within 120min, which is 3.6 times higher than that of pure TiO2.

A Ni2P modified Ti4+ doped Fe2O3 photoanode for efficient solar water oxidation by promoting hole injection.

Nickel phosphide (Ni2P) was used as an excellent water oxidation cocatalyst for photoelectrochemical (PEC) water splitting, which could significantly promote the hole injection efficiency and suppress the back reaction of water oxidation over a Ti4+ doped Fe2O3 photoanode.

Enhanced photocatalytic activity of degrading short chain chlorinated paraffins over reduced graphene oxide/CoFe2O4/Ag nanocomposite.

Short chain chlorinated paraffins have recently attracted great attention because of their environmental persistence and biological toxicity as an important organic pollutant. In this work, reduced graphene oxide/CoFe2O4/Ag (RGO/CoFe2O4/Ag) nanocomposite was prepared and employed for photocatalytic degradation of short chain chlorinated paraffins. The process of photocatalytic degradation of short chain chlorinated paraffins over RGO/CoFe2O4/Ag under visible light (λ>400nm) was investigated by in situ Fourier transform infrared spectroscopy and the related mechanisms were proposed. An apparent degradation ratio of 91.9% over RGO/CoFe2O4/Ag could be obtained under visible light illumination of 12h, while only about 21.7% was obtained with commercial P25 TiO2 under the same experimental conditions, which demonstrates that the RGO/CoFe2O4/Ag nanocomposite is a potential candidate for effective photocatalytic removal of short chain chlorinated paraffins.

Gold nanostars: Benzyldimethylammonium chloride-assisted synthesis, plasmon tuning, SERS and catalytic activity.

Fabrication of Au nanostars (AuNSs) can expand the application range of Au nanoparticles because of their high electron density and localized surface plasmon resonance (LSPR) on branches. Exploiting this potential requires further refinement of length of the branches and radius of their tips. To this end, we successfully synthesized AuNSs with uniform and sharply-pointed branches by combining benzyldimethylammonium chloride (BDAC) and cetyltrimethylammonium bromide (CTAB) at low BDAC/CTAB ratios. Once mixed with CTAB, BDAC lowers the critical micelle concentration (CMC) for quick formation of the micelles, which provides favorable growth templates for AuNSs formation. Besides, BDAC increases the concentration of Cl(-), which favors Ag(+) in adsorbing on Au facets. This feature is crucial for the yield boosting and synergic shape control of AuNSs regardless of types of Au seeds used. Use of less amounts of seeds as the center of nucleation benefited sharper and longer growth of the branches. AuNSs exhibited excellent enhancement of surface-enhanced Raman scattering (SERS) intensities as the result of high electron density localized at the tips; however, the enhancement degree varied in accordance with the size of branches. In addition, AuNSs showed high catalytic performance toward the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Efficient catalysis over AuNSs originates from their corners, stepped surfaces and high electron density at the tips.

Branch number matters: Promoting catalytic reduction of 4-nitrophenol over gold nanostars by raising the number of branches and coating with mesoporous SiO2.

In this study, we demonstrate for the first time that highly branched gold nanostars (AuNSs) and silica-coated AuNSs (AuNSs@mSiO2) could potentially serve as efficient hydrogenation catalysts. The catalytic activity could be promoted by raising the number of tipped-branches of AuNSs, which reveals that the tips play an important role as active sites. The fabricated sharply-pointed AuNSs benefit the electron transfer from BH4 anions to 4-nitrophenol. Coating AuNSs with mesoporous silica (AuNSs@mSiO2) further enhanced the reduction rate and recyclability, and also contributed to reducing the induction period. The AuNSs@mSiO2 (50-100nm in diameter) are large enough to be catalytically inactive, but they consist of sharply-pointed tips with the radius of 2.6-3.6nm, which are rich in coordinately unsaturated sites similar to those of nanoparticles and clusters. Such features in structure and activity would also extend their application range in heterogeneous catalysis.

Novel phosphorus doped carbon nitride modified TiO2 nanotube arrays with improved photoelectrochemical performance.

Novel phosphorus-doped graphitic-carbon nitride (P-C3N4) modified vertically aligned TiO2 nanotube arrays (NTs) were designed and synthesized. They can significantly enhance the conduction and utilization of photogenerated charge carriers of TiO2 NTs. The heterostructure was successfully fabricated through a three-step process: electrochemical anodization and wet-dipping followed by thermal polymerization. The prepared P-C3N4/TiO2 NTs exhibit enhanced light-absorption characteristics and improved charge separation and transfer ability, thus resulting in a 3-fold photocurrent (1.98 mA cm(-2) at 0 V vs. Ag/AgCl) compared with that of pure TiO2 NTs (0.66 mA cm(-2) at 0 V vs. Ag/AgCl) in 1 M NaOH solution. The prepared P-C3N4/TiO2 NT photoelectrodes also present excellent photocatalytic and photoelectrocatalytic capabilities in the degradation of methylene blue (MB). The kinetic rate of P-C3N4/TiO2 NTs in the photoelectrocatalytic process for MB is 2.7 times that of pristine TiO2 NTs. Furthermore, the prepared sample was used as a photoanode for solar-driven water splitting, giving a H2 evolution rate of 36.6 µmol h(-1) cm(-2) at 1.0 V vs. RHE under simulated solar light illumination. This novel structure with a rational design for a visible light response shows potential for metal free materials in photoelectrochemical applications.