Water structure near electrode interfaces may play an important role in controlling CO2 electroreduction. Using plasmon-enhanced vibrational sum frequency generation spectroscopy, we demonstrate the emergence of an interfacial water subpopulation with large electric fields along their OH bonds, when Na2CO3 ions are present near the electrode under applied potential. With molecular dynamics simulations, we show that the approach of aqueous Na2CO3 to electrodes is coupled to the formation of structured and oriented ion complexes, and that the emergent water population is associated with the first solvation shell of these complexes. This water subpopulation is seen even when the sole source of CO3 is its in-situ generation from CO2, indicating that the interfacial species investigated here are likely ubiquitous in CO2 electroreduction contexts.
Electrochemical conversion of CO2 on Cu-based catalysts offers an auspicious strategy for addressing the increasingly serious environmental issues. However, there is still a challenge in the regulation of selectivity for an efficient CO2 conversion process on Cu-based catalysts due to the complexity of the internal structure of catalysts. Herein, we step wisely control the intrinsic grain boundaries (GBs) and Sn doping in Cu substrate to optimize the CO2 reduction reaction (CO2RR) performance of catalyst, which also clearly clarify the contribution of above two factors towards CO2RR performance. As a result, the as-synthesized R-SnCu catalyst with both GBs and Sn doing exhibits the highest CO selectivity of 99 % at -0.8 V versus hydrogen electrode (vs. RHE). In-situ Raman spectroscopy was further used to provide critical evidence of the key intermediates during CO2RR. We find that compared to the catalysts containing only GBs or Sn doping, the R-SnCu catalyst controlled by both GBs and Sn doping exhibits a more pronounced adsorption preference for C-bound *COOH intermediate peaks related to CO generation. These findings provide new ideas for the effective design of high-performance Cu-based CO2RR catalysts.
The recombination of photogenerated charges is always a hinder for the improvement of photocatalytic efficiency. Herein, as a case of study, graphitic carbon nitride (g-C3N4) modified with N vacancies and Yb doping (YbCN) was synthesized by the thermal polymerization of ytterbium nitrate and melamine. The optimized sample showed a photocatalytic efficiency of 99.9% within 30 min for degrading tetracycline (TC) under visible light irradiation (lambda > 420 nm), which was 24 times than pure g-C3N4. The experimental results and density functional theory (DFT) calculations support that the enhanced performance for photocatalytic decomposition of TC was attributed to the doped Yb3+ and the formation of N vacancies. The doped Yb3+ and induced polarization can expand the light responsive range and inhibit the recombination of photogenerated carriers. Moreover, the introduction of Yb3+ in g-C3N4 can accelerate the adsorption and activation of O-2 to generate O-1(2), O-center dot(2)- and (OH)-O-center dot. Furthermore, the photocatalytic degradation pathway of TC was revealed by HPLC-MS and DFT calculations. Finally, the optimized sample catalyst was also employed for photocatalytic decomposition of TC in practical conditions including tap, river, and lake water. It was found that inorganic ions in real water can influence the photocatalytic degradation of TC. This work disclosed a strategy for the rational design of efficient g-C3N4-based materials for practical environmental remediation.
Strong metal-support interactions (SMSIs) play a pivotal role in enhancing the catalytic activity and stability of supported metal catalysts in heterogeneous thermal catalysis, but construction of effective SMSIs remains challenging in electrocatalysis. As a ubiquitous and versatile support for electrocatalysts, carbon materials are generally too inert to generate SMSIs with the loaded metal active sites. We hereby report a CVD-based method to prepare Ru nanoparticles on arrays of oxygen-and nitrogen-doped CNTs grown on the fibers of carbon paper (Ru/ONCNT@CP). The SMSIs were manifested by electronic structure tuning of Ru nanoparticles and their partial embedment in the carbon support. The SMSIs result in optimized Gibbs free energy of H*, lowered energy barrier of H2O dissociation, and enhanced catalyst robustness. Combined with the hierarchical microstructure, high surface area and hydrophilic/aerophobic nature, the Ru/ONCNT@CP electrode displays excellent HER catalytic activity in 1 M KOH, requiring overpotentials of only 73, 180, and 252 mV to achieve current densities of 100, 500, and 800 mA cm(-2), respectively. Moreover, the Ru/ONCNT@CP electrode exhibits outstanding stability, with negligible current decay after 120 h HER operation at 100 mA cm(-2). This work features an effective and scalable approach for preparation of metal-loaded-carbon electrocatalysts with engineered microstructure and SMSIs.
Modulation of electric currents through single-molecule junctions is usually achieved by synthesis of molecules with desired functionalities, in conjunction with suitable molecule–electrode contacts through specific anchoring groups. An alternative to this approach, barely explored so far, is to use structured electrodes, where conductivity could eventually be controlled by changing the specific anchoring site within the very same electrode. Here, we theoretically investigate how to exploit the pronounced anisotropy of corrugated graphene deposited on Ru(0001) (Gr/Ru) to tailor single-molecule conductivity in 4-aminophenyl and 4-aminobenzonitrile. We show that currents induced in the upper and lower anchoring positions in the Gr/Ru moiré are substantially different, irrespective of the chosen molecule. The magnitude of these currents can differ by as much as an order of magnitude at specific bias voltages. We also show that both molecules display rectifying properties, which can differ by up to a factor of five in different anchoring sites. Interestingly, the observed modulations strongly depend on the chemical binding nature between the molecule and the electrode, (strong) covalent bond for 4-aminophenyl and (weak) physisorption for 4-aminobenzonitrile. All this suggests that Gr/Ru can be an ideal electrode to modulate single-molecule electric conductivity under experimental conditions that are available in many laboratories.
The highly specific capture of radioactive iodine vapor generated during spent fuel reprocessing exerts a pivotal influence on ensuring the sustainable development of nuclear energy. In this study, we successfully prepared pyrazole-directed functionalized leather waste collagen fiber composite (Pyrazole@ACF) by immobilizing pyrazole ring through Schiff base reaction on the alkaline-activated collagen fiber (ACF) interface. The peak capacity for capturing iodine vapor by Pyrazole@ACF is shown to be 3.494 g/g, which is markedly higher compared to that of ACF (0.928 g/g). Pyrazole@ACF was characterized using FE-SEM, FT-IR, and XPS, revealing the release of numerous active functional groups from ACF that facilitated iodine-induced capture and pyrazole ring immobilization. Furthermore, the interaction mechanism between functional groups and iodine was further elucidated through Density Functional Theory (DFT) calculations. The iodine capture effect of Pyrazole@ACF is primarily ascribed to the existence of active functional groups (C = O, -OH, and -NH2) on ACF, as well as the charge transfer occurring between the grafted pyrazole moieties and iodine, ultimately leading to the generation of I-3(-) polyiodide complexes and subsequent iodine capture. Consequently, Pyrazole@ACF exhibits a strong specific capture capability for iodine vapor, along with excellent thermal stability and iodine immobilization properties, meeting the application requirements under practical conditions.
Selectivity of acetylene over CeO2 supported single Pd catalyst (Pd1/CeO2(1 1 1)) and 1,10-phenanthroline-5,6dione (PDO)-liganded Pd single catalyst (Pd1-PDO/CeO2(1 1 1)) was studied by density functional theory calculations combined with microkinetic modeling as well as ab initio molecular dynamics (AIMD) in this work. The present results show that the PDO-ligand can stabilize the single Pd catalyst through strong Pd-O/Pd-N interaction, which is further conformed by AIMD simulation. In the presence of PDO ligand, which contains Pd-O/PdN bonds, the single atom Pd is oxidized and becomes more stable. It was also found that the adsorption strength of C2H2 is weaker than C2H4 on single Pd, whereas opposite trend holds for PDO-liganded Pd single catalyst, indicating potential higher C2H4 formation electivity for Pd1-PDO/CeO2(1 1 1). Reaction mechanism analysis and microkinetic modeling demonstrate that the catalytic activity of C2H2 hydrogenation decreases but the C2H4 formation selectivity increases when PDO ligand was introduced, which agrees with the experimental observation. Moreover, the free energy change of C2H4 desorption as well as its further hydrogenation was quantitative studied by AIMD simulation, verifies that the PDO ligand indeed helps ethene desorption at high reaction temperature. It is hoped the present work may extend to other ligands which contain -O or -N groups that can bind with single metal atom strongly like -OH groups.
The incomplete recovery of Transition Metal Dichalcogenides (TMD) based gas sensors hinders their reliability and scalability. The leading cause of incomplete recovery is the strong chemisorption of gas analytes, such as defects or grain boundaries on the active surface of 2D TMDs. Herein, we demonstrate an improvement in the recovery rate of TMD gas sensors by selectively passivating the TMD surface defects or vacancies with Al2O3 via atomic layer deposition. Scanning electron microscopy analysis confirms that the nucleation and growth of atomic-layer-deposited Al2O3 occur along the grain boundaries and defects of the 2D MoS2 and WS2, not covering the inert basal plane. In addition, the Raman, photoluminescence, and X-ray photoelectron spectroscopy data show lower surface defect densities and a slight n-doping effect of Al2O3. This unique selectively defect-passivated TMD gas sensor shows a 400 % response toward 10 ppm of NO2, along with an increase in the recovery rate from 74 to 96 %, even at room temperature, as the number of atomic layer deposition cycles increases. Also, the recovery rate of NH3, a reducing gas, shows an increase of more than 30 %. Thus, the method proposed here is a promising strategy for improving the recovery rate of 2D TMD gas sensors.
The interfaces between superconductors and ferromagnets serve as a nurturing environment for spin-triplet superconducting pairs, where their spins align with the ferromagnetic moments, enabling the conduction of non-dissipative spin-polarized supercurrents that hold immense potential for spintronics applications and sci-entific advancements. In this study, we explore the spin-triplet superconductivity and the non-dissipative spin-polarized current in the YBa2Cu3O7(YBCO)/ La0.67Sr0.33MnO3(LSMO) bilayers with X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). The induced Cu moment at the interfaces exhibits three distinct alignment states: antiparallel, perpendicular, and parallel to the net moment of the LSMO ferromagnetic layer. Remarkably, the in-plane superconducting critical current experiences a sudden enhancement and displays a slower decaying trend to the applied magnetic field when the Cu-moment un-dergoes a transition from the antiparallel to the perpendicular state with respect to the LSMO magnetization. These findings shed light on the manipulation of induced Cu moments at interfaces, providing valuable insights for controlling spin-triplet states and enhancing non-dissipative spin-polarized supercurrents.
Currently, titanium dioxide (TiO2) has been demonstrated as a significant photocatalyst for the efficient removal of reactive dyes in dyeing effluents. However, due to the easy recombination of photogenerated carriers and electrostatic repulsion with reactive dye, single TiO2 cannot achieve satisfactory removal efficiency to reactive dye which is commonly used in cellulose fibers dyeing. Therefore, we prepared hollow titanium dioxide (H-TiO2) by alkaline treatment etching method and introduced quaternary ammonium groups on the surface of H-TiO2 photocatalyst (QAS-H-TiO2) by nucleophilic addition reaction. Improving the adsorption capabilities of C. I. reactive red 2 (RR2) and simultaneously separating the photogenerated carriers via the nitrogen cation of the quaternary ammonium groups facilitated the enhancement of its RR2 removal. The experimental results indicated that the utilization of QAS-H-TiO2 substantially bolstered the removal efficiency of RR2. The impact of molecular structure of quaternary ammonium salts on the adsorption ability of RR2, and the mechanism of regulation for photogenerated carriers, were investigated. It was found that the grafting of the quaternary ammonium group enabled mass and electron transfer channels, resulting in faster adsorption of dyes and separation of photogenerated carriers. This study presents a novel approach for preparing efficient QAS-H-TiO2 for high-performance organic dye removal.
Ion beam erosion of Si under co-deposition circumstances supports the formation of surface patterns on the nano- and micrometer scale. To evaluate the effect of surfactant sputtering within a setup relevant for ultra precision surface finishing, this work is presented. We present data for samples prepared with Ar ion beam erosion, at low ion energy. Al, Cu, steel, Cr, Ni, Mo, Ti, Ta, Zn and Si were chosen as co-deposition material. Simultaneous irradiation of the co-deposition material and the Si samples were performed with a broad beam ion source. The structuring and pattern formation are discussed with SEM and AFM measurements. It was shown that the evolution of structures on the substrate is induced by the silicide-forming metals. This corresponds with a higher surface roughness. Whereas the non-silicide-forming metals did not show patterning, and accordingly, lower surface roughness. Measurements regarding the Si removal rate showed, that it depends on the co-deposition material. Supporting simulation data proposed that the effect of the co-deposition material on the Si removal is determined by the combination of sputtering and scattering properties of the co-deposition material. The ratio of scattered Ar ions to sputtered metal particles describes the effect on the removal change. For metals which tend to higher scattering, the removal is enhanced. This applies for most of the metals with higher atomic number. Whereas the metals with lower atomic number favor self-sputtering, which results in an decreased Si removal.
Single-atom catalysts (SACs) have attracted considerable attention because of their excellent atomic utilization and catalytic performance. However, the choice of the carrier in SACs plays a decisive role in the catalytic performance. In this work, a series of single transition metal atoms (Fe, Co, Ni, Cu. Zn, Ru, Rh, Pd, Ag, Cd, Os, Ir, Pt, Au, Hg) doped on the two-dimensional(2D) VSe2 monolayer were selected as electrocatalysts, then we sys-tematically calculated and investigated hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as well as electrocatalytic oxygen reduction reaction (ORR) performance for a transition metal atom, doped VSe2 (TM@VSe2) through first-principle calculation. The results show that among all SACs, And Au@VSe2 has the lowest overpotential of 0.45 V, exhibiting excellent catalytic performance of OER. Meanwhile, Pt@VSe2 shows a good catalytic performance of HER with Delta GH* of 0.11 eV and certain catalytic performance of OER as well as ORR (eta OER = 0.72 eV, eta ORR = 0.85 eV), indicating that Pt@VSe2 may be utilized as a moderate triple-functional single-atom catalyst. This work broadens the view of designing multifunctional catalysts based on 2D VSe2 materials and provides a new paradigm for the study of advanced single-atom catalysts.
The extreme saline environment seriously threatens the service life of asphalt pavement. The interface adhesion failure between asphalt and aggregate is fundamental to pavement diseases. Therefore, the interface of asphalt-NaCl solution-mineral was simulated by molecular dynamics to investigate the adhesion failure mechanism between asphalt and aggregate in an extremely saline environment. The results show that the polarization-inducing effects of sodium and chloride ions promote the cross-sectional diffusion of the NaCl solution at the interfaces and contribute to the redistribution and rediffusion of asphalt components, and the formation of hydrogen bonds between water and asphalt components. The NaCl solution prevents the accumulation of sat-urates, resins, and asphaltenes on the SiO2 surface, and strips aromatics from the SiO2 surface due to the interaction. Sodium ions can be attracted to the oxygen atoms on CO32- to occupy active sites on the CaCO3 than asphalt, which makes it easier for chloride ions to penetrate the asphalt molecule and asphalt components to detach from CaCO3. These behaviors effectively impair the adhesion at the asphalt-mineral interface. The 3 wt% and 20 wt% NaCl solutions have the greatest effect on the adhesion work of the asphalt-SiO2 and asphalt-CaCO3, reducing them by 55.93 % and 66.03 %, respectively.
The energy resolution that can be achieved in x-ray photoelectron spectroscopy experiments allows to disentangle the contribution arising from the presence of a large variety of surface atoms in non-equivalent configurations which manifests itself not only with the appearance of different spectral components, but also as unusual lineshape. In the present work, we show that the fit of the C 1s core level spectrum of graphene grown on Ir(111) realized using 200 peaks based on ab initio calculations, accounting for the non-equivalent C atoms in the (10 x 10) moire ' cell, does not improve the fit quality with respect to the use of a single component. On the contrary, the quantitative fit quality can be drastically increased by introducing a dependency of the Lorentzian width on the distance between C and Ir first-layer atoms. This result is associated to the different electronic properties, and in particular to the different density of states of the sigma and pi bands, of C atoms sitting on TOP (hills) or FCC (valleys) regions of graphene which affect the lifetimes of the core-holes generated during the photoemission process.
Exploring high-efficient and stable electrocatalyst is essential for oxygen evolution reaction (OER) to deal with its slow kinetic process. Herein, a novel nanocomposite electrocatalyst coupling the amorphous high-entropy borate FeCoNiMnBOx with the high conductivity Ti3C2-MXene has been synthesized by a low-temperature liquid-phase reduction strategy. The FeCoNiMnBOx/MXene shows a low overpotential of 268 mV at a current density of 10 mA cm-2 with a Tafel slope of 39.8 mV dec-1 under alkaline conditions, better than that of pure FeCoNiMnBOx and noble metal RuO2 catalysts. The lamellar MXene in the composite can effectively suppress the aggregation of FeCoNiMnBOx and enhance the utilization of the active sites. The amorphous structure of FeCoNiMnBOx can expose more active sites. The strong interfacial bonding between MXene and FeCoNiMnBOx leads to redistri-bution of the interfacial charge and accelerates the charge transfer, which improve the electrical conductivity of the nanohybrids and promote the oxidation process of metal ions in FeCoNiMnBOx. The interface synergistically coupling effect to accelerate the kinetics of oxygen evolution reaction is demonstrated by in situ electrochemical impedance spectroscopy (EIS). This work provides a new branch for the design of high-efficient electrocatalysts for renewable energy applications.
The most salient features of resistive switching (RS) devices are low energy consumption, fast switching speed, and high-density integration, which render them promising candidates for realizing non-volatile memory and artificial synaptic devices. However, the growth of functional switching layers for RS devices needs innovative deposition techniques. Herein, we utilize a high-throughput vapor-transport-deposition (VTD) technique for synthesizing self-assembled tin-sulfide (SnS) nanoflakes, which are then used as a switching layer to fabricate an RS device. First principle calculations are conducted to understand the optoelectronic properties of SnS by employing density functional theory. The proposed Ag/SnS/Pt memory device exhibits substantial merits, including low-switching voltages (V-SET: 0.22 V and V-RESET: -0.20 V), suitable ON/OFF ratio (similar to 259), excellent endurance (10(6)), and extended memory retention (10(6) s) characteristics. In addition, RS stochasticity is modeled using statistical time-series analysis via Holt's exponential smoothing. Interestingly, the device can emulate multiple synaptic functionalities, including potentiation, depression, paired-pulse facilitation, paired-pulse depression, excitatory postsynaptic current, inhibitory postsynaptic current, and advanced spike-timing dependent plasticity rules. Moreover, the proposed synaptic device can detect the edge of images by utilizing a convolutional neural network. The unique and efficient VTD-SnS-based device will be a potential candidate for high-density non-volatile memory and neuromorphic computing applications.
Superhydrophobic coatings have great potential for applications in daily life and industrial production. In practical applications, however, the excellent mechanical and chemical stability of superhydrophobic surfaces remains a challenge. In this paper, a one-step spraying method, simple in process and low cost, was used to prepare superhydrophobic materials. To investigate the effect of different types of non-fluorinated modifiers on the wettability of the coatings, four silane non-fluorinated modifiers, dodecyltrimethoxysilane, hetradecyltrimethoxysilane, octadecyltrimethoxysilane and polydimethylsiloxane, were selected to prepare superhydrophobic surfaces. The superhydrophobic coating modified by non-fluorinated modifier retained its superhydrophobic performance after 48 h immersion in strong acid, strong alkali and salt solution and 6 months in outdoor environment, with excellent corrosion resistance. Moreover, it showed superior abrasion resistance and durability in sandpaper abrasion and tape peeling cycles tests. The superhydrophobic coating prepared by PDMS had the best overall performance compared with other silane non-fluorinated modifiers, and the separation efficiency of the prepared superhydrophobic cotton fabric could still be maintained above 99 % after 20 oil-water separation cycles. Its water contact angle was 164.8 degrees and sliding angle was 2.3 degrees, and it had the highest first bouncing height after the droplet bouncing test.
Herein, an advanced approach for transforming ordinary cotton-polyester fabric into a flexible and catalytic current collector is demonstrated for water and urea electrolysis for industrial-scale H2 production, addressing challenges in energy and environmental sustainability. A controlled electroless plating is adopted to deposit conducting metallic Ni-nanoparticles together with NixPy-catalytically active phase on an open macroporous framework of fabric. NiP-fabric electrodes exhibit exceptional hydrogen evolution reaction (HER) in alkaline, acidic, and in artificial Sea-water with overpotential values of 159 mV, 127 mV, and 94 mV at 10 mA/cm2 current density respectively. These electrodes also demonstrate the outstanding oxidation reaction for oxygen evolution and urea oxidation with the potential of just 1.509 V vs RHE (at 20 mA/cm2) and 1.312 V vs RHE (at 10 mA/cm2), with the in-situ formation of more active NiOOH species. A self-supported and macro-porous electrode configuration regulates the adsorption/desorption of intermediates species, enhanced charge and mass transport, and easier desorption of oxygen molecules. Finally, a two-electrode water and urea electrolyzer is constructed by NiP-fabric, which can deliver an H2-production at 100 mA/cm2 at a potential of 1.883 V and 1.611 V, respectively.
Though synergistic interactions between quaternary heteroatom (S, N, P, O) and FexO atoms could significantly improve catalytic performance, however, developing a robust catalyst with quaternary heteroatom-doped carbons and FexO is rarely addressed. We fabricated FeOx@SPNO-C core-shell nanospheres by using cyclotriphosphazene (P3N3)-derived covalent organic-inorganic hybrid frameworks (COIFs) and Fe3O4. The assynthesized FeOx@SPNO-C nanospheres catalyst attained superior PMS activation for degradation of sulfamethoxazole (SMX), achieving 99.5 % removal efficiency in 18 min, 65.1 % mineralization rate, lower iron leaching (0.014 mg/L), and reaction rate constant was 73.6 % higher than sole SPNO-C, counterpart. Non-radical 1O2 generation was the dominant pathway for SMX degradation, which was confirmed by electron paramagnetic resonance (EPR), radical quenching inorganic ions addition experiments, and density functional theory (DFT) calculations. Structural defects, C = O, C = C-C groups, and N/Fe-Nx sites atoms have been revealed to be active sites. The improved degradation of SMX may be attributed to many essential characteristics. Firstly, there is a synergistic impact between FexO and SPNO-C. Additionally, the carbon charge density is high, and there are numerous structural defects present. Furthermore, there is a significant presence of C = O groups, with a higher proportion of sp2 carbon containing sufficient free-flowing pi electrons. Lastly, the presence of N/Fe-Nx sites also contributes to the enhanced degradation of SMX. Several intermediate products were found, and a potential degradation mechanism was postulated. The high performance of FeOx@SPNO-C under harsh experimental conditions makes it a potential candidate for the commercial-scale Fenton-like catalyst.
Effect of ring charge density and ligand number on corrosion inhibition efficiency for N-containing compounds has not been systematically studied. Herein, the above factors were explored by comparison with pyridine (Py), quinoline (Ql) and 2,2 '-bipyridine (By). Further, 4 '-(4-aminophenyl)-2,2 ':6 ',2 ''-terpyridine (NH2-TPy) was syn-thesized to improve anti-corrosion ability. Gravimetric determination, electrochemistry, surface and solution analysis results showed that NH2-TPy demonstrated maximum protection efficiency of 95.37% with mixed in-hibition mechanism. Theoretical calculation explained differences in protective capacity of N-containing het-erocyclic compound by revealing possible anchoring sites and bonding strength. This study provides unique insights for design of new inhibitors and N-containing heterocyclic polymer.
