Charge Transfer Energy Research Articles

Linear scaling of charge transfer versus work function of Ammonia chemisorption on X-metal (X = Ag, Au, Pd, and Pt) surface

Although the d-band center theory can efficiently describe the interaction between gas molecules and transition metal surfaces, the specific reaction process and detailed adsorption criteria remain unclear. Therefore, we systemically investigated the adsorption process and mechanism of Ammonia (NH3) molecules on transition metal (i.e., Ag, Au, Pd and Pt) surfaces using first-principles calculations. Results indicate that the NH3 molecule undergoes chemisorption on the Pt (111) surface with considerable charge transfer and adsorption energy, indicating that Pt metal is a promising NH3-sensitive material. Furthermore, the chemisorption primarily entails the highest-occupied molecular orbital (HOMO) of NH3, and the metal atoms conform perfectly to the principles of energy-level matching, wave function matching, and maximal orbital wave function overlap. Notably, a linear relationship exists between the charge transfer of NH3 and the work function of X-metal substrates. Our findings provide a feasible way to efficiently design NH3-sensitive materials for experiments.

Confining bulk molecular O2 by inhibiting charge transfer on surface anions toward stable redox electrochemistry in layered oxide cathodes

Molecular O2 has been clarified as an important O-oxidation model in anionic redox, the charge compensation provided by which pushes energy-density limits of layered oxide cathodes. However, how to confine the bulk-formed molecular O2 and retard its conversation to free gaseous O2 (↑), an origin of unstable redox electrochemistry, remains open questions. Here, we propose a strategy via tuning relative values of Mott–Hubbard U and charge-transfer energy Δ to suppress charge transfer on surface anions to confine the bulk molecular O2. Supported by theoretical calculations, Nb5+ without 4d electrons which can enable U < < Δ is selected as a charge-transfer insulator. The thus Nb5+-surface-tailored model compound Na0.67Fe0.5Mn0.5O2 shows an oxygen-redox-inactive surface and well-confined bulk molecular O2 as directly uncovered by soft X-ray absorption spectroscopy and 50 K-electron paramagnetic resonance results respectively. Meanwhile, a stable redox electrochemistry with enhanced cycling stability, inhibited voltage decay and eliminated P2-O2 phase transitions is observed because of the well-caged bulk O2. More broadly, this work presents a versatile access to stabilize the important O-oxidation model, enriching approaches of stabilizing the anionic redox electrochemistry.

Oxygen on-site Coulomb energy in Pr1.3−xLa0.7CexCuO4 and Bi2Sr2CaCu2O8+δ and its relation with Heisenberg exchange

We study the electronic structure of electron-doped Pr$_{1.3-x}$La$_{0.7}$Ce$_{x}$CuO$_{4}$ (PLCCO ; $T_{c}$ = 27 K, x = 0.1) and hole-doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212 ; $T_{c}$ = 90 K) cuprate superconductors using x-ray absorption spectroscopy (XAS) and resonant photoemission spectroscopy (Res-PES). From Res-PES across the O K-edge and Cu L-edge, we identify the O 2p and Cu 3d partial density of states (PDOS) and their correlation satellites which originate in two-hole Auger final states. Using the Cini-Sawatzky method, analysis of the experimental O 2p PDOS shows an oxygen on-site Coulomb energy for PLCCO to be $U_{p}$ = 3.3$\pm$0.5 eV and for Bi2212, $U_{p}$ = 5.6$\pm$0.5 eV, while the copper on-site Coulomb correlation energy, $U_{d}$ = 6.5$\pm$0.5 eV for Bi2212. The expression for the Heisenberg exchange interaction $J$ in terms of the electronic parameters $U_{d}$, $U_{p}$, charge-transfer energy $\Delta$ and Cu-O hopping $t_{pd}$ obtained from a simple Cu$_2$O cluster model is used to carry out an optimization analysis consistent with $J$ known from scattering experiments. The analysis also provides the effective one band on-site Coulomb correlation energy $\tilde{U}$ and the effective hopping $\tilde{t}$. PLCCO and Bi2212 are shown to exhibit very similar values of $\tilde{U}$/$\tilde{t}$ $\sim$9-10, confirming the strongly correlated nature of the singlet ground state in the effective one-band model for both the materials.

Occurrence Modes of Critical Metals (Li+ and Ge4+) in the Organic Molecular Structures of Coal: A Density Functional Theory Study.

To explore the mechanism of critical metal (Li+ and Ge4+) occurrence in the organic molecular structures of different rank coals, simulations were investigated using quantum chemical density functional theory. In this paper, Wender lignite, bituminous, and anthracite molecular models were used as organic molecular structures in coal. The electrostatic potential (ESP), frontier molecular orbitals, and Mulliken charges were used to identify adsorption sites in organic molecular structures. Mulliken charge, bond length, Mayer bond order (MBO), and adsorption energy values were used to estimate the binding conformation and strength between organic molecular structures and critical metals (Li+ and Ge4+). The results showed that the negative ESP, the highest occupied molecular orbitals, and negative Mulliken charges in the organic molecular structures were located at the O atom of oxygen functional groups and the aromatic structures, respectively, which were the active sites for critical metal adsorption. Mulliken charge transfer, bond length, MBO, and adsorption energy data suggested that the binding of Li+ with organic molecular structures was controlled by the carbonyl group (C=O), while the aromatic structures had less effect on the occurrence of Li+ in the organic molecular structures. The maximum adsorption energy value for binding Li+ with organic molecular structures was -742.16 kJ/mol. The Ge4+ ions not only showed strong binding ability with oxygen functional groups, but also Ge4+ formed thermodynamically stable half-sandwich complexes with aromatic structures. Therefore, the coal rank had little effect on the binding of Ge4+ with organic molecular structures. Moreover, the binding of Ge4+ with organic molecule structures was enhanced by the synergistic interactions of oxygen functional groups and aromatic structures. The adsorption energy values were up to -8511.43 kJ/mol. The adsorption of organic matter in coal to critical metals (Li+ and Ge4+) generated changes in the spatial configuration of the organic molecular structure, including local twisting of the organic molecular structure in lignite and bending of the aromatic structure in anthracite.

Fe−O−P bond in MIL-88A(Fe)/BOHP heterojunctions as a highway for rapid electron transfer to enhance photo-Fenton abatement of enrofloxacin

MIL-88A(Fe)/BOHP (MxBy) heterojunctions were firstly fabricated via a ball-milling method, which were adopted as catalysts to activate hydrogen peroxide (H2O2) with the aid of visible light illumination to build a heterogeneous photocatalysis-Fenton-like synergetic system. The catalytic degradation efficiency of enrofloxacin (ENR) (10 mg/L) in the optimal M3B7/Vis/H2O2 system reached nearly 100 % with appreciable mineralization ability. Experimental and theoretical results co-unraveled that the formation of interfacial Fe−O−P chemical bonds between MIL-88A(Fe) and BOHP effectively reduced the charge transfer energy barrier (59.41–26.69 eV) and migration distance (3.104–1.917 Å), allowing the photo-generated carriers to be efficiently separated in space and improving the activation efficiency of H2O2 for producing more active species. Impressively, the constructed M3B7/Vis/H2O2 system was a cost-optimal and green technology for antibiotic wastewater treatment based on Electrical Energy per Order (EE/O) concept, life cycle assessment (LCA) and quantitative structure–activity relationship (QSAR) analysis.

General Charge Transfer Dipole Model for AMOEBA-Like Force Fields.

The development of highly accurate force fields is always an importance aspect in molecular modeling. In this work, we introduce a general damping-based charge transfer dipole (D-CTD) model to describe the charge transfer energy and the corresponding charge flow for H, C, N, O, P, S, F, Cl, and Br elements in common bio-organic systems. Then, two effective schemes to evaluate the charge flow from the corresponding induced dipole moment between the interacting molecules were also proposed and discussed. The potential applicability of the D-CTD model in ion-containing systems was also demonstrated in a series of ion-water complexes including Li+, Na+, K+, Mg2+, Ca2+, Fe2+, Zn2+, Pt2+, F-, Cl-, Br-, and I- ions. In general, the D-CTD model demonstrated good accuracy and good transferability in both charge transfer energy and the corresponding charge flow for a wide range of model systems. By distinguishing the intermolecular charge redistribution (charge transfer) under the influence of an external electric field from the accompanying intramolecular charge redistribution (polarization), the D-CTD model is theoretically consistent with current induced dipole-based polarizable dipole models and hence can be easily implemented and parameterized. Along with our previous work in charge penetration-corrected electrostatics, a bottom-up approach constructed water model was also proposed and demonstrated. The structure-maker and structure-breaker roles of cations and anions were also correctly reproduced using Na+, K+, Cl-, and I- ions in the new water model, respectively. This work demonstrates a cost-effective approach to describe the charge transfer phenomena. The water and ion models also show the feasibility of a modulated development approach for future force fields.

Constrained density functional theory calculations for estimation of forward and backward intermolecular charge transfer energy

AbstractCharge transfer (CT) in donor–acceptor complexes can occur in two directions: from donor to acceptor (forward CT, CTF) and from acceptor to donor (backward CT, CTB). For an ethylene and tetrafluoroethylene model system, coupled cluster calculations predict that CTF is more stable than CTB. Meanwhile, density functional theory (DFT) and time‐dependent DFT (TDDFT) employing B3LYP functional show a different CT state order depending on the Hartree–Fock exchange (HFX) contribution. The impact of basis sets as a possible cause to induce such unreasonable CT state reverse along with the increase of HFX was investigated. The physical origin of CT state reversal is examined in terms of molecular orbital energy. We analyzed two additional molecular pairs that feature CT state reversal along with the amount of HFX in B3LYP functional. Despite the reduced gap, we suggest constrained DFT using M06‐HF functional as an effective approach to estimate two CT state energies on equal footing.

Achieving Rapid Ultralow-Temperature Ion Transfer via Constructing Lithium-Anion Nanometric Aggregates to Eliminate Li+-Dipole Interactions.

Sluggish desolvation in extremely cold environments caused by strong Li+-dipole interactions is a key inducement for the capacity decline of a battery. Although the Li+-dipole interaction is reduced by increasing the electrolyte concentration, its high viscosity inevitably limits ion transfer at low temperatures. Herein, Li+-dipole interactions were eliminated to accelerate the migration rate of ions in electrolytes and at the electrode interface via designing Li+-anion nanometric aggregates (LA-nAGGs) in low-concentration electrolytes. Li+ coordinated by TFSI- and FSI- anions instead of a donor solvent promotes the formation of an inorganic-rich interfacial layer and facilitates Li+ transfer. Consequently, the LA-nAGG-type electrolyte demonstrated a high ionic conductivity (0.6 mS cm-1) at -70 °C and a low activation energy of charge transfer (38.24 kJ mol-1), enabling Li||NiFe-Prussian blue derivative cells to deliver ∼83.1% of their room-temperature capacity at -60 °C. This work provides an advanced strategy for the development of low-temperature electrolytes.

Minimized Energy Loss at the Buried Interface of p‐i‐n Perovskite Solar Cells via Accelerating Charge Transfer and Forming p–n Homojunction

AbstractThe energy loss (Eloss) aroused by inefficient charge transfer and large energy level offset at the buried interface of p‐i‐n perovskite solar cells (PVSCs) limits their development. In this work, a BF4− anion‐assisted molecular doping (AMD) strategy is first proposed to improve the charge transfer capability of hole transport layers (HTLs) and reduce the energy level offset at the buried interface of PVSCs. The AMD strategy improves the carrier mobility and density of poly[bis(4‐phenyl) (2,4,6‐trimethylphenyl) amine] (PTAA) and poly[N,N′‐bis(4‐butilphenyl)‐N,N′‐bis(phenyl)‐benzidine] (Poly‐TPD) HTLs while lowering their Fermi levels. Meanwhile, BF4− anions regulate the crystallization and reduce donor‐type iodine vacancies, resulting in the energetics transformation from n‐type to p‐type on the bottom surface of perovskite film. The faster charge transfer and formed p–n homojunction reduce charge recombination and Eloss at the HTL/perovskite buried interface. The PVSCs utilizing AMD treated PTAA and Poly‐TPD as HTLs demonstrate a highest power conversion efficiency (PCE) of 24.26% and 22.65%, along with retaining 90.97% and 85.95% of the initial PCE after maximum power point tracking for 400 h. This work provides an effective way to minimize the Eloss at the buried interface of p‐i‐n PVSCs by accelerating charge transfer and forming p–n homojunctions.

Crystallinity engineering for overcoming the activity–stability tradeoff of spinel oxide in Fenton-like catalysis

A precise modulation of heterogeneous catalysts in structural and surface properties promises the development of more sustainable advanced oxidation water purification technologies. However, while catalysts with superior decontamination activity and selectivity are already achievable, maintaining a long-term service life of such materials remains challenging. Here, we propose a crystallinity engineering strategy to break the activity-stability tradeoff of metal oxides in Fenton-like catalysis. The amorphous/crystalline cobalt-manganese spinel oxide (A/C-CoMnOx) provided highly active, hydroxyl group-rich surface, with moderate peroxymonosulfate (PMS)-binding affinity and charge transfer energy and strong pollutant adsorption, to trigger concerted radical and nonradical reactions for efficient pollutant mineralization, thereby alleviating the catalyst passivation by oxidation intermediate accumulation. Meanwhile, the surface-confined reactions, benefited from the enhanced adsorption of pollutants at A/C interface, rendered the A/C-CoMnOx/PMS system ultrahigh PMS utilization efficiency (82.2%) and unprecedented decontamination activity (rate constant of 1.48min-1) surpassing almost all the state-of-the-art heterogeneous Fenton-like catalysts. The superior cyclic stability and environmental robustness of the system for real water treatment was also demonstrated. Our work unveils a critical role of material crystallinity in modulating the Fenton-like catalytic activity and pathways of metal oxides, which fundamentally improves our understanding of the structure-activity-selectivity relationships of heterogeneous catalysts and may inspire material design for more sustainable water purification application and beyond.

Enabling extraordinary oxygen reduction reaction activity of dual alkaline earth-substituted perovskite cathodes for intermediate-temperature solid oxide fuel cells

Dual alkaline earth-substituted Pr0.94Ba1–2xSrxCaxCo2O5+δ perovskites are evaluated as potential cathodes for intermediate-temperature solid oxide fuel cells. When incorporating Sr2+ and Ca2+ into the lattice, the phase transformation from tetragonal layered perovskite to simple cubic perovskite can be identified. Benefitting from enhanced electrical conductivity, oxygen surface exchange and ionic diffusion rates, the as-prepared perovskite catalysts demonstrate highly electrocatalytic activity for oxygen reduction reaction. The Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δ cathode exhibits an area-specific resistance of 0.025 Ω cm2 at 700 °C, approximately decreased by = 60% relative to the pristine Pr0.94BaCo2O5+δ. It is discovered that Sr2+ and Ca2+ co-substituting lowers the charge transfer energy, as well as oxygen adsorption energy. Furthermore, the Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δ cathode-based fuel cell delivers a peak power density of 1194 mW cm−2 at 700 °C, along with outstanding short-term stability over a period of 160 h. Our results highlight a strategy of dual alkaline earth substitution for rationally designing the perovskite electrocatalysts.

The adsorption and sensing mechanism of toxic gases HCN, NO2, NH3 and Cl2 on Mo, Ag-modified WSe2 monolayer: Insights from the first-principles computations

In accordance to the density functional theory, the adsorption properties of toxic gases (HCN, Cl2, NH3, and NO2) upon pristine and X-doped (X = Mo, Ag) two-dimensional (2D) WSe2 were explored in this work. The adsorption performances were simulated and analyzed in terms of the charge transfer, DOS and molecular orbital. Results show that both Ag-WSe2 and Mo-WSe2 exhibit satisfactory adsorption capacity for HCN, Cl2, NH3, and NO2. Occurrence of chemisorption for the four gases on Mo-WSe2 monolayer is indicated by the exceptional molecular deformation, significant charge transfer and adsorption energy. Ag-WSe2 and Mo-WSe2 monolayer might be favorable materials for the sensing industrial toxic gases. In addition, Mo-doped WSe2 monolayer performs better in adsorbing NH3, NO2 and HCN than Ag-doped WSe2 monolayer, while Ag-doped WSe2 monolayer exhibits more satisfactory adsorption properties on Cl2. Finally, the NO2 molecule can be adsorbed better on both Ag-WSe2 monolayer and Mo-WSe2 monolayer, compared with NH3, Cl2 and HCN. This paper manifests that X-doped (X = Mo, Ag) WSe2 may be recommended in the field of toxic gases detection.

Front Cover: Influence of Changing the Remote Substituents on Charge Transfer Properties of Cyanide‐Bridged Trinuclear Fe−Ru−Fe Complexes (Eur. J. Inorg. Chem. 12/2023)

The Front Cover shows a new series of trinuclear Fe−Ru−Fe mixed-valence compounds obtained by changing the electron-donating ability of the remote substituents (R) of the ligand on the bridging metal center. The “person” (which symbolizes the electron) in the picture has to climb up different heights to reach the next corresponding step, which denotes the metal-to-metal charge transfer (MMCT) energy barriers from Ru2+ to Fe3+ in this family of compounds. As the electron-donating ability of the remote substituents decreases, it becomes more and more difficult for the “person” to reach the corresponding step, which means higher energy barriers need to be overcome for MMCT. The cover was designed by Bing-Chang Tan (the first author). More information can be found in the Research Article by T.-L. Sheng and co-workers.

V-Shaped RuO2 Nanotwin Complex Defect Facilitation of OER Reaction

RuO2 is one of the most active catalysts for the acidic oxygen evolution reaction (OER). As a first step in understanding the mechanism for V-shaped RuO2 nanotwin facilitation of the OER reaction, the relaxed atomic configuration and detailed partial density of states are determined using density-functional theory and are shown to dictate an upward shift of d- and p-band centers. The RuO2 101-nanotwin grain boundary (101-TGB), as the first ∑101 V-shaped structure constructed, reduces the distance between kinked Ru and its surrounding O atoms, which enhances p–d hybridization. The special structure properly regulates the value of ΔG*O–ΔG*OH and charge-transfer energy. In addition, with the introduction of transition-metal and oxygen vacancies, the degree of nanotwin dislocation increases, exhibiting positive effects on the improvement of surface catalytic activity. Regulating the synergistic effect of nanotwins and transition metals can thus be crucial in assisting the exploration of new, multiple, and excellent RuO2-based nanocatalyst materials.

Reviving Oxygen Evolution Electrocatalysis of Bulk La-Ni Intermetallics via Gaseous Hydrogen Engineering.

A hydrogen processing strategy is developed to enable bulk LaNi5 to attain high activity and long-term stability toward the electrocatalytic oxygen evolution reaction (OER). By a combination of in situ Raman and quasi in situ X-ray absorption (XAS) spectra, secondary-electron-excited scanning transmission electron microscopy (STEM) patterns as well as the Rietveld method and density functional theory (DFT) calculations, it is discovered that hydrogen-induced lattice distortion, grain refinement, and particle cracks dictate the effective reconstruction of the LaNi5 surface into a porous hetero-nanoarchitecture composed of uniformly confined active γ-NiOOH nanocrystals by La(OH)3 layer in the alkaline OER process. This significantly optimizes the charge transfer, structural integrity, active-site exposure, and adsorption energy toward the reaction intermediates. Benefiting from these merits, the overpotential (322mV) at 100mAcm-2 for the hydrogen-processed OER catalyst deposited on nickel foam is reduced by 104mV as compared to the original phase. Notably, it exhibits remarkable stability for 10 days at an industrial-grade current density of more than 560mAcm-2 in alkaline media.

Fully Flexible Covalent Organic Frameworks for Fluorescence Sensing 2,4,6-Trinitrophenol and p-Nitrophenol.

Nitrophenols are important nitroaromatic compounds, both important environmental pollutants and dangerous explosives, posing a devastating danger and pollution threat to humans. It is vital to detect efficiently trace nitrophenols in the environment. In this contribution, a series of fully flexible cyclotriphosphazene-based COFs (FFCP COFs: HDADE, HBAPB, and HBPDA), prepared with both a flexible knot and flexible linkers of different lengths, were used for sensing 2,4,6-trinitrophenol (TNP) and p-nitrophenol (p-NP) in real time with excellent sensitivity and selectivity. The quenching constants of HDADE by TNP, HBAPB, and HBPDA by p-NP are 6.29 × 104, 2.17 × 105, and 2.48 × 105 L·mol-1, respectively. The LODs of TNP and p-NP are 1.19 × 10-11, 6.91 × 10-12, and 6.05 × 10-12 mol·L-1. Their sensitivities increase with the linker length, which is better than the corresponding COFs composed of rigid linkers. There is only a photoinduced electron transfer mechanism in the fluorescence quenching of HBPDA by p-NP. Meanwhile, the mechanisms of photoinduced charge transfer and resonance energy transfer exist in the fluorescence quenching of HDADE by TNP and the fluorescence quenching of HBAPB by p-NP.

Theoretical proposal and material realization of ferromagnetic negative charge-transfer energy insulator

Here we propose another type of ferromagnetic semiconductors: ferromagnetic negative charge-transfer insulator (FNCTI). In FNCTI, the negative charge-transfer states strongly enhance the ferromagnetic (FM) exchange interactions and the orbital hybridization gap permits the magnetic molecular orbitals as the underlying magnetic units rather than local atomic orbitals. Thus the FM exchange interactions are rather strong and decay slowly due to the large spearding of magnetic molecular orbitals. This is distinct from the superexchange mechanism where FM exchange interactions are quite weak as summarized in the well-known Goodenough-Kanamori-Anderson semi-empirical rules.Through first-principle calculations with the hybrid functional, PbO-type CrAs monolayer is mapped out to be a FNCTI, which possesses a band gap $\sim$ 0.35 eV, FM nearest-/next-nearest-neighbor exchange coupling strength $\sim$ 57/40 meV, and a high $T_c$ $\sim$ 1500 K respectively. It is believed that the existence of FNCTI validates the long-pending hypothesis by D. I. Khomskii and G. A. Sawatzky in 1997 [Solid State Commun. 102, 87 (1997)].

Frontispiece: Unlocking Charge Transfer Limitations for Extreme Fast Charging of Li‐Ion Batteries

Lithium Ion Batteries. Fast charging of high-energy Li-ion batteries is achieved by simultaneously reducing the anode and cathode charge transfer energy barriers through electrolyte engineering, as reported by Chong Yan, Qiang Zhang et al. in their Research Article (e202214828).

Soft-assembled, bio-gel electrolytic double layer capacitor system for sustainable energy storage

ABSTRACT Carrageenan is an attractive bio-derived polymer electrolyte due to its high ionic conductivity, cyclic stability, and cost-effectiveness in copolymerizing with other biocompatible polymers such as polyvinyl alcohol (PVA). This paper discusses the physical and chemical characterizations of the bio-electrolyte(s): PVA, carrageenan, and PVA-carrageenan copolymer blend. We also describe a fabrication method to create a soft-printed, thin-film, bio-gel electrolytic double-layer capacitor (bio-EDLC) using a PVA-carrageenan polymer blend. The addition of PVA to carrageenan provided structural and mechanical stability to the biopolymer, as confirmed by the hydrogen bonds detected using attenuated Fourier-transform infrared spectroscopy analysis. The assembled bio-EDLCs were analyzed for their electrical properties including their internal charge transfer mechanism, electrical breakdown, specific capacitance, power density, and energy density. It was determined that the bio-EDLC offers specific capacitance of 84 F/g and power density of 4.15E-02 W/kg and has a breakdown voltage of ~1.1 V. Furthermore, preliminary optimization was performed on the bio-EDLC with a drop casting of reduced graphene oxide at the electrode/electrolyte interface to create surface micro-roughness resulting in a bio-EDLC system which demonstrated superior electrical characteristics with an overall specific capacitance of up to 118 F/g, breakdown voltage of ~1.3 V, and improved maximum charging capability to 80%.

Organic macromolecule on graphene with structural defects: Estimations of charge transfer and adhesion energy

The previously proposed model of dengling bonds of an organic macromolecule (MM) adsorbed on an ideal single-layer graphene (SLG) is generalized to the presence of structural defects in SLG: inclusions of two-layer or amorphous graphene. Analytical estimates of the charge transition between MM and the substrate and the adhesion energy are obtained. Keywords: macromolecule with dangling bonds, single- and bilayer graphene, amorphous graphene.