Local Charge Density Research Articles

Engineering ZnIn2S4 Nanosheets with Zinc Vacancies: Unleashing Enhanced Photocatalytic Degradation of Tetracycline.

Defect engineering is a highly effective strategy for accelerating charge transfer and enhancing the performance of photocatalysts. In this study, ZnIn2S4 nanosheets were designed and prepared with controlled Zn vacancies to optimize the electronic band structure and localized charge density of ZnIn2S4. EPR results confirmed the formation of Zn vacancies. This modification enabled efficient capture of photoexcited charges in defect centers, thereby prolonging the carrier's lifetime. Theoretical calculations demonstrated that these vacancies induced the formation of new defect states and highly efficient surface reaction sites. As anticipated, under visible light irradiation, the photocatalytic tetracycline removal rate of the ZnIn2S4 nanosheets with Zn vacancies reached 82.8% within 60 min, significantly higher than that observed for the pristine ZnIn2S4 sample. These findings offer valuable insights into the deliberate construction of metal-vacancy-containing photocatalytic nanomaterials for the enhanced degradation of micropollutants.

Internal Electron-Donation Allocation Design for Intrinsic Solubilization of Lithium Nitrate in Ester Electrolyte for Stable Lithium Metal Batteries.

Lithium metal batteries (LMBs) have become a hot topic in the research of next-generation advanced battery technology due to their high specific energy. However, the high reaction activity between lithium metal and electrolyte is considered one of the key bottlenecks limiting large-scale applications of LMBs. As a classic electrolyte additive, LiNO3 significantly improves the stability of lithium metal in ether-based electrolytes. However, its solubility in carbonate-based electrolytes widely used in lithium-ion batteries is extremely low, and its protective effect on lithium metal is limited, which has become a key obstacle to the commercial application of lithium metal batteries. Here, we enhanced the local negative charge density of carbonyl oxygen atoms in carbonate molecules by introducing electron donors, making it easier for them to coordinate with Li+, thereby weakening the interaction between Li+ and NO3-, and significantly increasing the solubility of LiNO3 in ester electrolytes. The modified ester solvent promotes the derivatization and decomposition of salt anions, leading to the formation of a dense SEI layer rich in LiF and LiNxOy. This significantly improves the stability of lithium metal in ester-based electrolytes. The assembled Li||Li symmetric battery shows excellent cycling performance of over 4000 hours.

Boosting Photoluminescence of Rare-Earth-Based Double Perovskites by Isoelectronic Doping of ns2 Metal Ions.

Doping of ns2 metal ions as an energy transfer (ET) bridge can significantly elevate the photoluminescence properties. Nonetheless, the fundamental influence of ns2 metal ions on the local lattice structures remains unclear, hindering the advancement of functional materials. Herein, Sb3+ doped rare earth double perovskites is employed as a typical case to demonstrate this issue. It is found that the isoelectronic doping of Sb3+ ions not only enhances the ET efficiency but also changes their localized electronic and lattice structures. Both density functional theory (DFT) and Judd-Ofelt (J-O) theory calculations provide unambiguous evidence that the isoelectronic doping of Sb3+ ions enables a more localized charge density in the [LnCl6]3- (Ln: Lanthanide) octahedron and reduces the symmetry of the environment around the Ln3+, facilitating the radiative transition rates of Ln3+ while enhancing their ET efficiency. Compared with Cs2NaScCl6:Ln3+, the ET efficiency of Cs2NaScCl6:Sb3+/Ln3+ is enhanced by 1.5-fold, reaching up to 98.3%. To the best of available knowledge, this work is the first to unravel the intrinsic mechanism of enhanced ET process enabled by isoelectronic doping via DFT and J-O theory. This research sheds light on understanding the mechanism of photophysics and rational design of the functional perovskite materials.

Boosting Alkaline Hydrogen Oxidation Kinetics through Interfacial Environments Induced Surface Migration of Adsorbed Hydroxyl

Constructing bifunctional sites through heterojunction engineering to accelerate water formation has become a pivotal strategy to improve the alkaline hydrogen oxidation reaction (HOR) kinetics, which is mainly focused on the synergistic effect of neighboring sites and the energetics of the surface reaction steps. However, the roles of the surface migration of key intermediates that go beyond the bifunctional mechanism limited to neighboring atoms have usually been ignored. Using the heterostructured Ni3C‐Ni catalyst as a model, we found that the rapid surface migration of OHad species from the positively charged Ni3C to the negatively charged Ni component played a decisive role in facilitating water formation. Such unprecedented surface migration of OHad is induced by the large discrepancy between the local surface charge densities and interfacial environments of the Ni3C and Ni components under operating conditions. Benefiting from this, the resultant Ni3C‐Ni exhibited outstanding mass activity for the alkaline HOR, which was approximately 19‐fold and 21‐fold higher than those of Ni and Ni3C, respectively. These findings not only provide novel insights into the alkaline HOR mechanism of heterostructured catalysts but also open new avenues for developing advanced electrocatalysts for alkaline fuel cells.

Boosting Alkaline Hydrogen Oxidation Kinetics through Interfacial Environments Induced Surface Migration of Adsorbed Hydroxyl.

Constructing bifunctional sites through heterojunction engineering to accelerate water formation has become a pivotal strategy to improve the alkaline hydrogen oxidation reaction (HOR) kinetics, which is mainly focused on the synergistic effect of neighboring sites and the energetics of the surface reaction steps. However, the roles of the surface migration of key intermediates that go beyond the bifunctional mechanism limited to neighboring atoms have usually been ignored. Using the heterostructured Ni3C-Ni catalyst as a model, we found that the rapid surface migration of OHad species from the positively charged Ni3C to the negatively charged Ni component played a decisive role in facilitating water formation. Such unprecedented surface migration of OHad is induced by the large discrepancy between the local surface charge densities and interfacial environments of the Ni3C and Ni components under operating conditions. Benefiting from this, the resultant Ni3C-Ni exhibited outstanding mass activity for the alkaline HOR, which was approximately 19-fold and 21-fold higher than those of Ni and Ni3C, respectively. These findings not only provide novel insights into the alkaline HOR mechanism of heterostructured catalysts but also open new avenues for developing advanced electrocatalysts for alkaline fuel cells.

Wettability regulation of the electric double-layer structural evolution of complex fluids: Insights into thermodynamic and electrical properties

Understanding the structural evolution at the electrode is essential for accurate prediction of complex fluid applications, where the carbon nanotube is chosen as the carrier of CO2-ionic liquids (ILs) in electroreduction. Then, the electrical double layer with tunable wettability is investigated by molecular dynamics simulations. The competition and cooperation between van der Waals and Coulomb interactions are evaluated by examining the structural and electric characteristics. When an external potential (φ) is initiated, the co-ions are repelled from the electrode and the counter-ions compete with CO2 in the electric double layer (EDL), with different thermodynamics produced by varying the proportion of CO2/ionic liquid. As the solid–liquid interaction parameter (β) increases, more counter-ions aggregate, producing double density peaks for Tf2N− and sharply increasing the density of CO2. With increases in β and φ, the local charge density and local field potential increase, and the EDL thickness decreases. However, the location of the CO2 density layer shifts ahead to the counter-ions, weakening their shielding effect and capacitance. Using a combination of structural analysis, the first and second peaks of Tf2N− of EDL are composed of sulfonyl and trifluoromethyl, respectively. As a response, the steric hindrance of CO2 decreases, and more molecules migrate to the surface in a parallel orientation. The structural evolution is quantitatively evaluated in terms of the entropy, results show that the orientation transition is prominent in structural evolution. The coupling relation between thermodynamic and electrical properties plays a pivotal role in determining the structural evolution of complex mixtures, and these findings could benefit the advancement of ILs-based CO2 electroreduction and other complex fluid applications.

Coupling defect-inherent built-in electric fields to promote directional charge migration for rapid photocatalytic degradation of levofloxacin

By enhancing the intrinsic built-in electric field (IEF) of the catalyst through defect engineering, and coupling the IEF of the catalyst via an S-type heterojunction structure, a 3-in-1 IEF is formed, which drives the directional migration of electrons and holes, and can effectively improve photocatalytic performance. In this paper, an oxygen vacancy-type Bi2WO6 (Ov-BWO) composite with twin-type Zn0.5Cd0.5S (ZCS) was synthesized to construct an S-scheme heterojunction. The twin structure results in an IEF in ZCS that points from the twin plane Zn to the twin boundary S. The oxygen vacancies, on the other hand, create an internal electric field from Bi and W to O by altering the local charge density. By coupling the IEF of the catalyst through the S-type heterojunction, an enhanced IEF is formed, pointing from the twin plane Zn to the O in Ov-BWO, enabling rapid directional migration of photogenerated charge carriers. Furthermore, potential Levofloxacin (LVFX) intermediates and degradation pathways were found by combining Liquid chromatography-mass spectrometry (LC-MS) data with Density Functional Theory (DFT) simulations. This study systematically elucidates the photocatalytic degradation system, from catalyst design to the degradation process of pollutants, through the analysis of theoretical calculations and experimental results.

Engineering of novel vanadium-doped Ni4N@CuCoN0.6 heterostructure for enhancing urea oxidation reaction at high current density

Herein, the vanadium-doped Ni4N@CuCoN0.6 heterostructure with brush shape structure supported on copper foam (denoted as V-doped-Ni4N@CuCoN0.6/CF) is prepared to serve as a highly-performing UOR electrocatalyst at high current density (E10/500/1000 = 1.26/1.40/1.45 V). Thanks to the construction of heterojunction, the local charge density undergoes redistribution at the V-doped-Ni4N@CuCoN0.6/CF interface in a 1.0 M KOH + 0.5 M urea solution, thereby significantly enriching the active site and facilitating the adsorption process of urea molecules. Notably, V doping exerts an additional influence by modulating the electronic structure of the catalyst, potentially optimizing the urea adsorption/CO2 desorption process and reducing the energy barrier for the rate-determining step. Operando electrochemical impedance spectroscopy results show direct oxidation for urea molecules on the surface of V-doped-Ni4N@CuCoN0.6/CF, indicating that V-doping and heterostructure can effectively improve electron transfer. Furthermore, because the brush shape structure can be beneficial for bubble release and liquid transport on the catalyst’s surface, for UOR stability, V-Ni4N@CuCoN0.6/CF can maintain at 500 mA cm−2 for 80 h.

Eley−Rideal path enhanced NH3-SCR: Central Fe atoms activation for electron transfer promotion

Manganese modified Fe2O3 catalyst is a promising candidate to replace the commercial NH3-SCR catalyst for controlling NOx emission due to its superior performance and N2 selectivity at low temperature. In order to elucidate the effects of different modification methods of Mn on physicochemical properties and reaction mechanism in Fe-Mn binary catalysts, two kinds of Mn modified Fe2O3 are prepared by co-precipitation and impregnation method, respectively. Compared with MnO2 loaded Fe2O3, Mn doped Fe2O3 achieves above 85 % of NOx conversion with 20 % increase in N2 selectivity within 100–200°C. Transient reaction experiments and DFT calculation results prove that doping Mn effectively increases the reaction rate of the main reaction and reduces the formation of N2O through Eley−Rideal path. The formation of multiple Fe-O-Mn structures after Mn doping facilities the formation of coordination bond between the central Fe atoms and NH3 via modulating local charge density of Fe atoms, effectively improving the adsorption of NH3 and preventing its excessive oxidation, which leads to high activity and N2 selectivity at low temperature. This mechanism provides theoretical support for increasing the activity and N2 selectivity of NH3-SCR catalysts at low temperature and gains clear insight on the interaction between binary metal oxides.

Droplet Electrophoresis with Internal Free Ions: Effect of Permittivity Changes in the Electric Double Layer.

Droplet electrophoresis (EP) is of interest in biological systems, microfluidics, and separation techniques. We investigate EP of an oil droplet that contains free ions and is stabilized in an electrolyte solution through an amphoteric surfactant. The presence of mobile ions within the droplet leads to the creation of a distinct nonzero space charge density inside the droplet and consequently, formation of an inner EDL inside the droplet in addition to the traditionally considered outside EDL. While we assume the permittivity inside the inner EDL to remain constant, we consider both the case of constant and variable permittivity in the outer EDL. Our findings demonstrate a change in the droplet direction of motion in the electric field when transitioning from acidic to alkaline pH, regardless of permittivity and ionic strength in both oil and electrolyte. We further find a significant reduction in the magnitude of droplet velocity in the case of a variable permittivity due to reduction of the local space charge density within the EDL surrounding the droplet. When decreasing the viscosity ratio of the oil to the electrolyte, in all cases we find a reduction in droplet velocity. This decline is attributed mostly to the formation and strength of a vortex around the droplet. We finally demonstrate that with constant permittivity in the outer EDL, the variation in κaouter has a more significant effect on the droplet's EP velocity than altering κainner. However, in cases where the body forces inside of the droplet dominate, minor changes in the outer electrolyte concentration have no influence on the droplet motion, which is relevant for biological colloids that can contain significant free internal charges. Our results are important for the manipulation of biological colloids, water and waste treatment such as lubricant removal from processing streams.

Transformation of a cellular skyrmion to polyomino-like structures

Topological spin structures with transformable shapes may have potential implications for data storage and computation. Here, we demonstrate that a square cellular skyrmion on an artificial grid pinning pattern can be manipulated by programmed current pulses. We find that parallel short pulses could result in elongation of the skyrmion mainly in the current direction, while parallel long pulses are able to induce elongation in the direction perpendicular to the current due to the intrinsic skyrmion Hall effect. Consequently, a programmed sequence of parallel pulses could lead to transformation of the skyrmion to I-, L-, and Z-shaped polyomino-like structures without affecting the topological charge. In addition, we find that orthogonal pulses could lead to the transformation to more complex polyomino-like structures, including T-shaped and irregular ones. Particularly, when a small T-shaped structure is formed, the topological charge of the system is found to be non-integer due to incomplete compensation of local topological charge densities; however, the T-shaped structure is stable on the attractive pinning pattern. Our results offer an effective way to create polyomino-like spin structures toward functional applications.

Constructing Adsorption Site-Enhanced Vo-BiOCl/rGO Heterostructures for Efficient Response to NO2/NH3 Gases at Room Temperature.

Real-time detection of harmful gases at room temperature has become a serious problem in public health and environmental monitoring. Two-dimensional materials with semiconductor properties BiOCl is a promising gas-sensitive material due to its large specific surface area and adjustable band gap as well as outstanding safety characteristics. However, limited by the weak gas adsorption sites and sluggish charge-transfer ability, the performance of BiOCl could not be fully exploited. Oxygen vacancy (Vo) engineering can introduce lattice defects, thereby significantly increasing the local charge density and enhancing the adsorption of gases, which is an effective strategy to enhance the gas-sensing performance. In this work, we composite BiOCl with a vacancy (Vo-BiOCl) and reduced graphene oxide (rGO) to construct a Vo-BiOCl/rGO heterostructure with enhanced gas adsorption sites. Experimental and theoretical calculations show that Vo can enhance the adsorption of gases and the introduction of rGO forms a high-quality heterostructure with BiOCl, which can effectively reduce the band gap of BiOCl and promote electron transfer, thereby improving the sensitivity of the sensor. Benefiting from above, Vo-BiOCl/rGO achieves the ability to detect low concentrations of NO2/NH3 at room temperature, with high sensitivity (55% at 1 ppm of NO2 and -28% at 1 ppm of NH3), fast response time (40 s at 1 ppm of NO2 and 2 s at 1 ppm of NH3), good stability (over 150 days), and fully recoverable gas sensitivity.

Ion-Selective Transport Promotion Enabled by Angstrom-Scale Nanochannels in Dendrimer-Assembled Polyamide Nanofilm for Efficient Electrodialysis.

The ion permeability and selectivity of membranes are crucial in nanofluidic behavior, impacting industries ranging from traditional to advanced manufacturing. Herein, we demonstrate the engineering of ion-conductive membranes featuring angstrom-scale ion-transport channels by introducing ionic polyamidoamine (PAMAM) dendrimers for ion separation. The exterior quaternary ammonium-rich structure contributes to significant electrostatic charge exclusion due to enhanced local charge density; the interior protoplasmic channels of PAMAM dendrimer are assembled to provide additional degrees of free volume. This facilitates the monovalent ion transfer while maintaining continuity and efficient ion screening. The dendrimer-assembled hybrid membrane achieves high monovalent ion permeance of 2.81 mol m-2 h-1 (K+), reaching excellent mono/multivalent selectivity up to 20.1 (K+/Mg2+) and surpassing the permselectivities of state-of-the-art membranes. Both experimental results and simulating calculations suggest that the impressive ion selectivity arises from the significant disparity in transport energy barrier between mono/multivalent ions, induced by the "exterior-interior" synergistic effects of bifunctional membrane channels.

Ion-selective supramolecular membrane with pH-regulated smart nanochannels for lithium extraction

Tunable gating ion-conducting membranes with high water permeability and precise ion selectivity remain urgently demanded in smart nanofiltration for efficient lithium extraction. Herein, inspired by the filtration function of protein channels, we report a smart and high-performance supramolecular membrane constructed via coordination between quaternary ammonium ligands (m-phenylenediamine/polyethyleneimine) and metal ion center (Cu2+). The pore architecture of the supramolecular membrane is dynamic and can be switched by applying pH stimulus, where coordinated interchain expands when exposed to acidic operating conditions and induces concomitantly reinforced electrostatic exclusion due to enhanced local charge density. The tunable gating regularity enables operando modulation of precise ionic separation in situ. The resulting membrane exhibits significantly enhanced water permeance (19.8 L m−2 h−1·bar−1) and simultaneously promoted Li+/Mg2+ selectivity (RMg2+ = 96.4 %), surpassing typical trade-off between permeability and selectivity at pH 3 condition. This study demonstrates the amazing capability of environmental-responsive regulation of membrane pore-channel structure, and provides inspiration for engineering advanced supramolecular membranes for lithium extraction and beyond.

New QSPR molecular descriptors based on low-cost quantum chemistry computations using DFT/COSMO approach

This work presents a simple computational methodology to determine new theoretical molecular descriptor scales convenient for use in QSPR correlations and the analysis of solvation-related properties. On the basis of low-cost quantum chemical computations using DFT/COSMO approach, in particular that implemented in the ADF/COSMO-RS module of the Amsterdam Modeling Studio program package, optimized geometry and local screening charge density of a considered molecule are obtained and related to the proposed descriptors through an a priori simple reasoning. Values of four molecular descriptors, namely volume VCOSMO∗, hydrogen bond/Lewis acidity αCOSMO and basicity βCOSMO, and charge asymmetry of the nonpolar region of the molecule δCOSMO have been calculated and are presented for sets of 128 non-ionic organic molecules and 47 ions composing ionic liquids. Relation of the proposed scales to some others that are widely known or presented recently in the literature has been examined. Although the present methodology is completely independent of any experimental data, the theoretical descriptor scales proposed here have been found to correlate linearly quite well with the respective empirical scales (mostly R2 > 0.8, and for some R2 > 0.9). For non-ionic organics, just the direct proportionality provided adequate fits of the well-established prominent scales such as those of Abraham, Klamt, Kamlet-Taft, Catalan, Gutmann, and Laurence and showed only a few statistically justifiable outliers. For ions composing ILs, the linear fits of seven acidity or basicity scales presented previously with those proposed in this work were of similar quality. Examining the observed outliers, several descriptor values reported in the literature were identified as being in error. Good performance of the new descriptor scales has been demonstrated by employing them for LSER fitting of various solvation-related thermodynamic and kinetic properties such as standard vaporization enthalpy, standard hydration enthalpy, air–water partition coefficient, air-IL partition coefficient, and solvent effects on the activation Gibbs energy or rate constant of SN1 and SNAr reactions. The quality of these correlations appears to be comparable to that of the correlations currently available for these properties, regardless of the role, solute or solvent, the involved molecules played.

Enhanced CO2 photoreduction to CH4 via *COOH and *CHO intermediates stabilization by synergistic effect of implanted P and S vacancy in thin-film SnS2

Reduction of CO2 to value-added hydrocarbons through artificial photosynthesis is one of the way to address the energy crisis and climate change issues. It is known that lowering the activation energy of CO2 molecules on the photocatalyst surface and key intermediates is crucial in photocatalytic CO2 reduction. Herein, we present phosphorus-implanted 20-nm SnS2 continuous thin film with sulfur vacancies (i.e., SV-SnS2:P where P substitutes on S sites). The fabrication process involves thermal evaporation, post-sulfurization, and ion implantation. Our gas-phase photocatalytic experiments show an enhanced and selective CO2 photoreduction to CH4 with a yield of 0.13 µmol cm−2 and selectivity of 92 % under solar-light irradiation for 4 h over an optimal ∼4.5 % P and ∼16 % SV. Experimental observations, conducted through X-ray absorption near edge, in situ near ambient pressure X-ray photoelectron, and in situ Fourier transform infrared spectroscopies, along with first-principle density functional theory calculations. Results reveal that P dopant is significantly affected by nearby SV via local charge density transfer from P to the nearest Sn and next-nearest S neighbor atoms, consequently, leads to the stabilization of *COOH and *CHO intermediates, where asterisks stand for P as the active site. Our results demonstrate how active site modulation, without using precious co-catalysts, plays a crucial role in intermediate stabilization in a wireless photocatalysis process.

High Thiophene-S doped soft carbons for sodium storage

S-doped carbon materials with both low cost and high capacity are one of the best choices for large-scale sodium storage. However, conventional S doping strategies often fail to obtain a high S concentration and accurately control the doping forms of sulfur, which restricts the Na-storage performance and mechanism revelation of materials. Here, low-cost pitch-derived soft carbons with ultrahigh surface-S doping (12.19 at%) and thiophene-S ratio approaching 95 % (CSC95) are accurately synthesized by a modified sulfate pyrolysis strategy. Density functional theory calculations indicate that thiophene-S is an ideal doping form that can form reversible Na-S bonds, which is beneficial for improving the Na-adsorption and storage ability for the materials. The rich thiophene-S regulates the local charge density to improve the electrical conductivity of CSC95. More importantly, the highly reversible redox reactions between thiophene-S and Na+ dominate the Na-storage process. In addition, the hierarchically porous structure of CSC95 provides moderate surface area and ion diffusion channels to ensure the fast Na-storage kinetics. As expected, CSC95 deliver a high Na-storage capacity of 574.5 and 187.7 mAh g−1 at 0.2 and 10 A g−1, respectively, and remarkable cyclability of 77.4 % capacity retention for 800 cycles at 10 A g−1. Moreover, Na3V2(PO4)2F3@C (NVPF@C)//CSC95 full cells display gravimetric energy density of 217 Wh kg−1 at 0.1C and 89.4 % capacity retention after 120 cycles at 1C.

Long-term irradiation of an ATLAS NSW SM2 Micromegas quadruplet using an AmBe neutron source

The NSW Micromegas chambers in the ATLAS forward muon spectrometer are subject to background rates of 15-20kHz/cm2 under HL-LHC conditions. The innermost detector area closest to the LHC beam pipe will accumulate a charge of 0.068Ccm−2year−1 under these rates. Due to the late change of the detector gas from non-aging Ar:CO2 93:7vol% to the more HV stable ternary mixture Ar:CO2:iC4H10 93:5:2vol% and the known vulnerability of wire chambers to Hydrocarbon-containing gas mixtures a three-year-long aging study has been performed. An SM2 series module of the NSW Micromegas quadruplets was irradiated at LMU in Garching/Munich using a 10GBq AmBe neutron source emitting 6×105MeV n/s as well as 3.5×105 4.4MeV gammas/s and 3.6×109 60keV gammas/s. The SM2 chamber was irradiated in a region of several 10cm2 in size with a dose rate well exceeding the HL-LHC equivalent local charge densities for three years. In between the irradiation periods the performance of the SM2 chamber regarding spatial resolution and efficiency on cosmic muon tracking was tested several times. We report on the irradiation and the performance studies of the SM2 Micromegas quadruplet and conclude that no sign of loss in performance has been observed in contradiction to an earlier experience using drift tube wire chambers.

Machine-Learning driven STM images prediction of doped/defective graphene: Towards optimized tools for 2D nanomaterials characterization

Scanning tunneling microscopy (STM) is a key characterization technique that allows for visualization of specific features at nanostructures, given its ability to reveal changes in local charge densities in doping or defective sites. Besides the experimental acquisition of STM data from real samples, there is the theoretical route, which allows for STM images simulation from ab-initio calculations on defined nanostructures. This work presents an alternative route for theoretical STM image prediction by means of Machine Learning (ML) methods, based on the training of deep convolutional neural networks using simulated STM data. The ML-based STM predictions for defective, B- and N-doped graphene quantum dots are compared to ab-initio STM simulations, in terms of accuracy of structural rearrangements, charge density localizations, and computational resources requirements. The results demonstrate that STM images predicted by ML-methods are accurate at doping sites, whereas they show good similarity to simulations of large structural vacancies. This work represents a novel alternative for the use of ML methods in image-based characterization routines of doped/defective graphene, and potentially, for other 2-dimensional nanomaterials.

Oxygen-Deficient FeNbO4-x In-Situ Growth in Honey-Derived N-Doping Porous Carbon for Overall Water Splitting.

It is still a great challenge to reasonably design green, low cost, high activity and good stability catalysts for overall water splitting (OWS). Here, we introduce a novel catalyst with ferric niobate (FeNbO4) in-situ growing in honey-derived porous carbon of high specific surface area, and its catalytic activity is further enhanced by micro-regulation (oxygen vacancy and N-doping). From the experimental results and density functional theory (DFT) calculations, the oxygen vacancy in catalyst FeNbO4-x@NC regulates the local charge density of active site, thus increasing conductivity and optimizing hydrogen/oxygen species adsorption energy. FeNbO4 in-situ grows within N-doping honey-derived porous carbon, which can enhance active specific surface area exposure, strengthen gaseous substances escape rate, and accelerate electrons/ions transfer and electrolytes diffusion. Moreover, in-situ Raman also confirms O-species generation in oxygen evolution reaction (OER). As a result, the catalyst FeNbO4-x@NC shows good electrochemical performance in OER, HER and OWS.