Induced Charge Redistribution Research Articles

2D multifunctional SiAs2/GeAs2 van der Waals heterostructure

The structural and electronic properties of two-dimensional (2D) SiAs2/GeAs2 van der Waals heterostructure (vdWH) and its applications are investigated by combing first-principles calculations and Silvaco Atlas simulations. The stable SiAs2/GeAs2 vdWH exhibits an indirect bandgap of 0.99 eV in type II band alignment for light detection and energy harvesting. The vdWH can exhibit a direct bandgap up to 0.66 eV by applying an appropriate electric field (E ext ). Due to the E ext induced charge redistribution, its band alignment can be transformed from type II to type I for light-emitting. Further simulation shows that the band alignment of SiAs2/GeAs2 vdWH can be tuned back and forth between type II and type I by gate voltage in a single field-effect transistor for multiple functional applications. These results may be useful for applications of the SiAs2/GeAs2 heterostructure in future electronic and optoelectronic devices.

Room-temperature liquid metal synthesis of nanoporous copper-indium heterostructures for efficient carbon dioxide reduction to syngas

Nanoporous metals show promising performances in electrochemical catalysis. In this paper, we report a self-supporting bimetallic porous heterogeneous indium/copper structure synthesized with a eutectic gallium-indium (EGaIn) material on a copper substrate. This nanoporous copper-indium heterostructure catalyst exhibits excellent performance in the reduction of carbon dioxide to syngas. The ratio of H2/CO is tunable from 0.47 to 2.0 by changing working potentials. The catalyst is highly stable, showing 96% maintenance of the current density after a 70-h continuous test. Density functional theory calculations reveal that the indium/copper interface induces charge redistribution within the copper surface, leading to the formation of two distinct active sites, namely, Cuδ and Cu0, and enabling a high-performance generation of CO and H2. This work provides a new strategy for obtaining self-supporting nanoporous metal electrode catalysts.

High‐Rate Performance of Fluorinated Carbon Material Doped by Phosphorus Species for Lithium‐Fluorinated Carbon Battery

The lithium–fluorinated carbon (Li/CFx) battery possesses the highest energy density (2180 Wh kg−1) among all the primary lithium batteries. However, the poor electronic conductivity of the fluorinated carbon (CFx) material sets a limit on its rate discharge capability, confining its practical application. In this article, a doping strategy at a mild anneal condition is developed to synthesize the phosphorus species‐doped CFx materials (P‐CFx) for Li/CFx batteries. Compared to the commonly used methods, this eco‐friendly, and simple doping method does not involve washing, centrifugation, and filtration processes. Characterization using X‐Ray diffraction, high‐resolution transmission electron microscope, and X‐Ray photoelectron spectroscopy confirms the successful doping and the structure of the P‐CFx. Density functional theory calculations and characterization results demonstrate that phosphorus species doping can alter microstructure and induce charge redistribution to improve electronic and ionic conductivity. Therefore, the Li/P‐CFx battery possesses a high specific capacity and an excellent rate capability, shown by a high discharge capacity of 810 mAh g−1 with a voltage plateau of 2.53 V at 0.1 C. Extraordinarily, a discharge capacity of 597 mAh g−1 with a voltage plateau of 1.90 V at 20 C has been achieved as well as a high power density of 34 048 W kg−1.

Acrylonitrile‐Linked Covalent Organic Frameworks Enable Fast Stimulus‐Responsive Fluorescence with High Quantum Yield via Fluorine Chemistry

Covalent organic frameworks (COFs) have emerged as potential light‐emitting polymers for optoelectronic and optical devices, but their smart responsiveness to environmental stimuli has seldom been explored particularly for alkene‐linked conjugated COFs, which limits their application scope in “smart” systems. Herein, fluorine chemistry coupled with acrylonitrile linkage is introduced as a “one‐stone‐three‐bird” strategy to produce a smart COF with rapid pH‐responsive absorption and fluorescence, high fluorescence quantum yield (QY), and good crystallinity. In addition to increased crystallinity, the newly designed fluorinated acrylonitrile‐linked COF (TF‐COF) produces 20% enhancement in fluorescence QY and more rapid responsiveness of absorption and fluorescence under acid–base induction compared to the nonfluorinated counterpart. Impressively, the yielded QY reaches 33.6% in solid states and 41.0% in tetrahydrofuran dispersion, surpassing most existing COF materials. The synergy effect of fluorine chemistry induced charge redistribution and acrylonitrile linkage enabled reversible C═C bonds contributes to the rapid responsiveness, high fluorescence QY, and good crystallinity. The developed TF‐COF can be utilized as a responsive phosphor to endow image encryption with high coloration and good reversibility, and as an encryption data carrier via simple handwriting.

CO2 reduction reaction pathways on single-atom Co sites: Impacts of local coordination environment

Single-atom catalysts have been proposed as promising electrocatalysts for CO2 reduction reactions (CO2RR). Co-N4 active sites have attracted wide attention owing to their excellent CO selectivity and activity. However, the effect of the local coordination environment of Co sites on CO2 reduction reaction pathways is still unclear. In this study, we investigated the CO2 reduction reaction pathways on Co-N4 sites supported on conjugated N4-macrocyclic ligands with 1,10-phenanthroline subunits (Co-N4-CPY) by density functional theory calculations. The local coordination environment of single-atom Co sites with N substituted by O (Co-N3O-CPY) and C (Co-N3C-CPY) was studied for comparison. The calculation results revealed that both C and O coordination break the symmetry of the primary CoN4 ligand field and induce charge redistribution of the Co atom. For Co-N4-CPY, CO was confirmed to be the main product of CO2RR. HCOOH is the primary product of Co-N3O-CPY because of the greatly increased energy barrier of CO2 to *COOH. Although the energy barrier of CO2 to *COOH is reduced on Co-N3C-CPY, the desorption process of *CO becomes more difficult. CH3OH (or CH4) are obtained by further *CO hydrogenation reduction when using Co-N3C-CPY. This work provides new insight into the effect of the local coordination environment of single-atom sites on CO2 reduction reaction pathways.

Negative inductive effect enhances charge transfer driving in sulfonic acid functionalized graphitic carbon nitride with efficient visible-light photocatalytic performance

Efficient photogenerated carrier migration/separation plays a critical role in increasing the photocatalytic performance of g-C3N4. Herein, sulfonic acid group-functionalized g-C3N4 (SACN) was synthesized and then synchronously strengthened by a facile-solid-state thermal reaction of g-C3N4 and sulfamic acid. As a solid strong acid, sulfamic acid can be used to achieve acid etching on the surface of g-C3N4 with the assistance of thermal treatment, leading to an enlarged specific surface area and increased surface catalytic reaction sites. More importantly, our experiments and density functional theory calculations indicate that the driving force generated by the negative inductive effect of sulfonic acid groups significantly improves the charge transfer dynamics and effectively inhibits their recombination. Moreover, the negative inductive effect can induce charge redistribution, which reduces the conduction band potential of g-C3N4 to enhance the reduction ability of photo-induced electrons. As a result, the SACN-400 sample showed excellent photocatalytic performance in H2 generation with an apparent quantum efficiency of 11.03% at 420 ± 15 nm, as well as an efficient photodegradation rate for organic pollutants.

Encapsulated RuP2-RuS2 nanoheterostructure with regulated interfacial charge redistribution for synergistically boosting hydrogen evolution electrocatalysis.

Exploring cost-effective electrocatalysts with suitable hydrogen binding strength and rational micro/nano-architecture towards the hydrogen evolution reaction (HER) is crucial for energy technologies, yet remains a tough challenge. Herein we present the first instance of a nanoscale RuP2-RuS2 heterostructure encapsulated in N, P, and S co-doped porous carbon nanosheets (RuP2-RuS2/NPS-C) for boosting the HER. The synthesis involves the construction of a 2D core-shell structured precursor in which Ru3+-functionalized g-C3N4 is wrapped by poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) followed by pyrolysis. In this nanocomposite, the unique architecture with a highly dispersed embedded RuP2-RuS2 nanoheterostructure guarantees not only full exposure of the active sites with enhanced robustness but also smooth mass/charge transfer. More significantly, the experimental results and theoretical calculations reveal that coupling RuP2 with RuS2 to construct a heterointerface can induce charge redistribution, giving rise to optimized hydrogen adsorption energy for substantially accelerating the HER. This work provides a novel strategy to engineer high-performance Ru-based electrocatalysts by elegantly modulating the micro-/nano-architecture and interface coupling effect.

Effects of adatom species on the structure, stability, and work function of adatom-α-borophene nanocomposites.

Work function-tunable borophene-based electrode materials are of significant importance because they promote efficient carrier extraction/injection, thereby enabling electronic devices to achieve maximum energy conversion efficiency. Accordingly, determining the work function of adatom-borophene nanocomposites within a series wherein the adatom is systematically changed will facilitate the design of such materials. In this study, we theoretically determined that the M-B bond length, binding energy, electron transfer between adatoms and BBP, and work function (ϕ) are linearly dependent on the ionization potential (IP) and electronegativity for thermodynamically and kinetically stable adatom-α-borophene (M/BBP) systems involving a series of alkali (earth) metal/BBP (M = Li-Cs; Be-Ba) and halogen/BBP (M = F-I), respectively. However, the binding energies of Li/BBP and Be/BBP deviate from these dependencies owing to their super small adatoms and the resulting significantly enhanced effective M-B bonding areas. By interpreting the electron transfer picture among the different parts of M/BBP, we confirmed that metallic M/BBP possesses ionic sp-p and dsp-p M-B bonds in alkali (earth) metal/BBP but covalent-featured ionic p-p interactions in halogen/BBP. In particular, the direct proportionality between IP and ϕ for alkali (earth) metal/BBP originates from the synergistic effect of charge rearrangement and the increased induced dipole moment; however, the inverse proportionality between electronegativity and ϕ for halogen/BBP arises from the adsorption induced charge redistribution. Our results provide guidance for experimental efforts toward the realization of work function-tunable borophene-based electrodes as well as insight into the bonding rules between various adatoms and α-borophene.

Band Bending Induced Charge Redistribution on the Amorphous Mil-53(Al)/Co-Ldh Conjunction to Boost the Supercapacitive and Oxygen Evolution Performance

Band Bending Induced Charge Redistribution on the Amorphous Mil-53(Al)/Co-Ldh Conjunction to Boost the Supercapacitive and Oxygen Evolution Performance

Electron-induced effect and coordinated pi-delocalization synergistically promote charge transfer in benzenesulfonic acid modified g-C3N4 with efficient photocatalytic performance

The synergistic effect of the sulfonic acid group and aromatic ring in benzenesulfonic acid modified g-C3N4 induces charge redistribution for melon units, leading to efficient photocatalytic performance.

Aliovalent doping engineering enables multiple modulations of FeS2anodes to achieve fast and durable sodium storage

P doping regulates the electronic conductivity of FeS2and induces charge redistribution around the doping sites to generate a local built-in electric field. As an anode in SIBs, P–FeS2@C shows superior rate performance and cycling stability.

Encapsulated ruthenium nanoparticles activated few-layer carbon frameworks as high robust oxygen evolution electrocatalysts in acidic media

Noble metals have been extensively employed as high active catalysts for oxygen evolution reaction (OER), are usually subjected to serious surface transformation and poor structural stability, especially in acid media, which need imperatively remedied. Herein, the interfacial engineering of Ru via few-layer carbon (Ru@FLC) was carried out, in which FLC can significantly suppress the corrosion of Ru in acid media, ensuring the efficient interfacial charge transport between Ru and FLC. As a result, a low overpotentials@10 mA cm−2 of 258 mV and small Tafel slopes of 53.1 mV dec−1 for oxygen evolution OER were achieved in acid media. DFT calculations disclose that outer FLC could induce charge redistribution and effectively optimize intermediates free energy adsorption, resulting in greatly reduce the energy barrier for OER. Our work may offer a new avenue to produce progressive OER electrocatalysts for energy-related applications in acid solution.

Tuning selectivity of electrochemical reduction reaction of CO2 by atomically dispersed Pt into SnO2 nanoparticles

Electrochemical reduction of CO2 into fuels offers an attractive approach to environmental and energy sustainability. Herein, we designed atomically dispersed Pt into SnO2 catalyst (Pt atom/SnO2). Such catalyst dramatically improves the adsorption performance of CO2 and lowers the activation energy of CO2. DFT calculations indicate that the doping of Pt in SnO2 could induce charge redistribution and tune active electronic state, showing higher adsorption energy for intermediates CO2*, HCOO* and HCOOH*, which is different from the Pt NPs loaded SnO2 mainly for H2 generation. As a result, a higher Faradaic efficiency (82.1 ± 1.4%) and the production rate (5105 μmol h−1 cm−2) of HCOO– are achieved at −1.2 V vs. RHE. Moreover, the current density and Faradaic efficiency of HCOO– nearly remain unchanged in 8 h on the Pt atom/SnO2, indicating its high stability. This work opens up a new avenue to tune product selectivity by atomically dispersed catalysts.

Defect Induced Charge Redistribution and Enhanced Adsorption of Lysozyme on Hydroxyapatite for Efficient Antibacterial Activity.

Defects in hydroxyapatite (HA) have attracted increasing research interest due to their significant functions to increase the bioactivity and antibacterial ability of hard-tissue implants. However, little is known about the natural property and functional mechanism of the defects in HA. Herein, we reported on the defect property concerned with the coordination state and charge distribution in Al doped HA, as well as the consequent interface and protein capture ability for improved antibacterial activity. Systemic investigations suggested that Al replacing Ca in HA induced coordination defect with decreased coordination number and bond distance, caused charge transfer and redistribution of surrounding O atom and resulted in an increase in negative charge of coordinated O atoms. These O atoms coordinated with Al further served as docking sites for lysozyme molecules via electrostatic and H-bonding interaction. The capacity of lysozyme adsorption for Al-HA increased approximately 10-fold more than that of HA, which significantly increased the antibacterial activity through lysozyme-catalyzed splitting of cell wall of bacteria. Moreover, in vitro studies indicated that Al-HA materials showed good cytocompatibility. These findings not only provided new insights into the important effect of defects on the performances of HA biomaterials by modulation of the coordination state, charge distribution, and chemical activity, but also proposed a promising method for efficient antibacterial activity of HA biomaterials.

Can di-4-ANEPPDHQ reveal the structural differences between nanodiscs and liposomes?

The potential-sensitive di-4-ANEPPDHQ dye is presently gaining popularity in structural studies of the lipid bilayer. Within the bilayer, dye environmental sensitivity originates from the excitation induced charge redistribution and is usually attributed to solvent relaxation. Here, di-4-ANEPPDHQ is utilized to compare the structure of neutral and negatively charged lipid bilayers between two model systems: the nanodiscs and the liposomes. Using the well-established approach of measuring solvatochromic shifts of the steady-state spectra to study the bilayer structural changes has proved insufficient in this case. By applying an in-depth analysis of time-resolved fluorescence decays and emission spectra, we distinguished and characterized two and three distinct emissive di-4-ANEPPDHQ species in the liposomes and the nanodiscs, respectively. These emissive species were ascribed to the dual emission of the dye rather than to solvent relaxation. An additional, long-lived component present in the nanodiscs was associated with a unique domain of high order, postulated recently. Our results reveal that the di-4-ANEPPDHQ steady-state fluorescence should be interpreted with caution. With the experimental approach presented here, the di-4-ANEPPDHQ sensitivity was improved. We confirmed that the bilayer structure is, indeed, altered in the nanodiscs. Moreover, molecular dynamic simulations showed a distribution of the probe in the nanodiscs plane, which is sensitive to lipid composition. In POPC nanodiscs, probe frequently interacts with MSP, while in POPC-POPG nanodiscs, such interactions are rare. We did not observe, however, any impact of those interactions on the probe fluorescence.

Magnetically induced charge redistribution in the bending of a composite beam with flexoelectric semiconductor and piezomagnetic dielectric layers

We study electromechanical fields in a thin composite beam of a flexoelectric semiconductor layer sandwiched between two piezomagnetic dielectric layers induced by an applied magnetic field. The macroscopic theory of piezomagnetics and flexoelectric semiconductors is used. A one-dimensional model is derived from the three-dimensional equations. Responses under static and time-harmonic magnetic fields are obtained analytically from the model. Results show magnetically induced bending deformation and redistribution or motion of charge carriers toward the top and bottom of the beam through combined piezomagnetic and flexoelectric couplings. A coupling coefficient depending on the physical and geometric parameters of the structure is introduced to characterize the strength of the effect. The coupling coefficient assumes a maximum for a specific thickness ratio of the piezomagnetic and semiconductor layers. The results are fundamental to the emerging field of flexoelectronics when magnetic fields are involved.

Nanoconfined fusion of g-C3N4 within edge-rich vertically oriented graphene hierarchical networks for high-performance photocatalytic hydrogen evolution utilizing superhydrophillic and superaerophobic responses in seawater

Two-dimensional photocatalysts often suffer severe aggregation due to the inevitable van der Waals forces between nanosheets, which limits their photocatalytic water-splitting efficiency. Herein, a rational design of confined synthesis of g-C3N4 nanomeshes (GCN) on N-doped vertically-oriented graphene (NVG) arrays for enhanced hydrogen evolution is reported. The aggregation of 2D g-C3N4 nanosheets is effectively avoided via physical separation by electrically conductive NVG networks. Well-defined hierarchical architecture of the GCN/NVG photocatalyst endows with superaerophobicity and simultaneously enhanced light absorption. Experimental and ab initio simulation results suggest that the protruding graphene edges induce charge redistribution, thus enhancing interfacial charge separation. The GCN/NVG samples demonstrate a high areal hydrogen evolution rate of 41.7 μmol h−1 cm−2 (225 L m−2 in 24 h, STP) in water and 45.8 μmol h−1 cm−2 (246.2 L m−2 in 24 h, STP) in simulated seawater. This work creates further opportunities for the development of earth-abundant photocatalysts.

A non-carbon catalyst support upgrades the intrinsic activity of ruthenium for hydrogen evolution electrocatalysis via strong interfacial electronic effects

Abstract Metal-support interactions play crucial roles in tailoring the activity and stability of catalytic active sites by virtue of electronic, geometric and compositional effects. Here, we report a hybrid electrocatalyst composed of ultrafine Ru nanoclusters uniformly anchored on mesoporous Mo2N nanorods (Ru–Mo2N) for highly efficient hydrogen evolution reaction (HER). With a low Ru content of 4.1 wt%, Ru–Mo2N requires overpotentials of only 18 and 16 mV for affording a current density of −10 mA cm−2 in acidic and alkaline media, respectively. The outstanding performance has been revealed to originate from the interfacial electronic interactions between Ru and Mo2N, which induces charge redistribution at the interface region and slightly positive oxidation state of Ru. The downshift of the d-band center of Ru nanoclusters results in reduced binding strength to reactive intermediates and improved HER thermodynamics on Ru surface. This work has demonstrated that engineering the electronic interactions between catalyst and support is one promising route for constructing high-performance electrocatalysts.

Matching the Directions of Electric Fields from Triboelectric and Ferroelectric Charges in Nanogenerator Devices for Boosted Performance.

SummaryEmbedding additional ferroelectric dipoles in contacting polymer layers is known to enhance the performance of triboelectricnanogenerator (TENG) devices. However, the influence of dipoles formed between the triboelectric surface charges on two contacting ferroelectric films has been ignored in all relevant studies. We demonstrate that proper attention to the alignment of the distinct dipoles present between two contacting surfaces and in composite polymer/BaTiO3 ferroelectric films can lead to up to four times higher energy and power density output compared with cases when dipole arrangement is mismatched. For example, TENG device based on PVAc/BaTiO3 shows energy density increase from 32.4 μJ m−2 to 132.9 μJ m−2 when comparing devices with matched and mismatched dipoles. The presented strategy and understanding of resulting stronger electrostatic induction in the contacting layers enable the development of TENG devices with greatly enhanced properties.

Distinct electronic and transport properties between 1T-HfSe2 and 1T-PtSe2

In this study, we employed the first-principles calculation to investigate the structural, electronic and transport properties of 1T-HfSe2 and 1T-PtSe2 transition metal dichalcogenides, and further explain why they share the same 1T (octahedral) layered structure but exhibit very different electronic and transport properties. There are two underlying concepts: the degree of interlayer bond ionicity and the number of 5d valence electrons of transition metal. The high degree of Hf-Se bond ionicity not only gives rise to the indirect energy gap of HfSe2 bulk and thin films, but also results in the weak Se-Se vdW interlayer coupling to further restrict the electron transport only within a HfSe2 layer. On the other hand, the modulation of metallic/semiconducting property of PtSe2 bulk and thin films can be understood by the significant vdW interlayer coupling, which induces charge redistribution of Se atom and allows electrons to transport within a PtSe2 layer as well as cross neighboring layers. Finally, our transport calculation for 1T-HfSe2/1T-PtSe2 bulks and monolayers suggests the great electron transport within Hf-Se/Pt-Se layer but suppresses/allows electron from neighboring layers. The robust two-dimensional characteristic of 1T-HfSe2 and the metal-to-semiconductor transition of 1T-PtSe2 may provide more knowledge for future application in nanoelectronic and optoelectronic devices.