Water Molecules Research Articles

Enhanced Room-Temperature Phosphorescence in Delignified Wood Through Combination with Pyrene-Based Materials.

Organic room-temperature phosphorescent (RTP) materials, featured by their large Stokes shifts and long lifetimes, have garnered significant attention due to their promising applications in biophotonics and optoelectronics. However, the instability of their triplet states and their proneness to quenching in aerobic, room-temperature environments pose significant challenges. Herein, delignified wood (DW) is used as a porous substrate and applied heat to drive dehydration condensation between cellulose/hemicellulose hydroxyls and the phosphorescent chromophore 1-pyrenylboronic acid (Py-BOH). This reaction forms B─O bonds, anchoring Py-BOH in a rigid microenvironment created by hydrogenbonding in the DW pores, which restricts molecular thermal motion and facilitates the RTP emission, resulting in a lifetime of 340ms for the target RTP-DW film. Furthermore, due to the susceptibility of the cellulose hydrogen-bond network to disruption by water molecules, the RTP-DW film is sensitive to water and exhibits repeatable stimulus-responsive behavior under water/thermal stimulation. This material can be processed into various luminous objects by directly cutting the wood film into different shapes or grinding it into powder and compounding it with polymers, thereby holding potential applications in luminous indication and anti-counterfeiting. The successful preparation of this (room-temperature phosphorescent-delignified wood)RTP-DW film will provide an effective pathway for achieving high-value utilization of wood resources.

A Robust and Tough Composite Hydrogel Electrolyte with Anion-Locked Supramolecular Network for Zinc Ion Batteries.

Hydrogel electrolytes have garnered extensive attention in zinc ion batteries due to their excellent flexibility and good safety. However, their limited mechanical properties, low ionic conductivity, and poor Zn2+ transference number pose significant challenges for developing high-performance zinc ion batteries. Herein, this work constructs a 3D supramolecular network capable of locking anions and active water molecules through the abundant hydrogen bonding interactions between aramid nanofibers, polyvinyl alcohol, and anions. This network synergistically enhances the mechanical properties (with a mechanical strength of 0.88MPa and a toughness of 3.28MJ m-3), ionic conductivity (4.22 S m-1), and Zn2+ transference number (0.78). As a result, the supramolecular composite hydrogel electrolyte can effectively inhibit dendrite growth and side reactions, facilitate interface regulation, and enable uniform zinc deposition. The Zn anode exhibits a cycle life of 1500h at 5mA cm-2 and 5 mAh cm-2, with an average coulombic efficiency of 99.1% over 600 cycles. Additionally, the Zn||polyaniline full cell maintains a high capacity retention of 78% after 9100 cycles at 1 A g-1. The assembled pouch cells demonstrate good flexibility, deformability, and compression resistance. This work provides valuable insights into the design of high-performance hydrogel electrolytes for zinc ion batteries.

Anticoagulant Sulfonate Polyamide/Poly(ether sulfone) Membrane Barrier for Efficient Blood Oxygenation.

Extracorporeal membrane oxygenation (ECMO) is the most important support for patients with severe cardiopulmonary failure. As the key component, the oxygenation membrane has suffered the risk of blood coagulation and plasma leakage in the long term. Herein, we prepare a sulfonate polyamide film on poly(ether sulfone) (PES) support via interfacial polymerization modulated by a sulfonate amine monomer. The pore diameter of the prepared polyamide film is ∼3.67 Å (exactly a little smaller than the water molecule, the base of plasma). By such size repulsion effect, the polyamide film demonstrates remarkable plasma leakage resistance (confirmed by human plasma circulation). Moreover, the introduction of the sulfonate amine monomer effectively enhances the anticoagulation performance (activated partial thromboplastin time (aPTT) prolongation >10 s). In addition, the PES support used for interfacial polymerization is modified and realizes improved porosity, hydrophilicity, and positive charge potential, resulting in lower mass transfer resistance and improved interfacial strength between the support and polyamide film. ECMO-simulated circulation tests prove the facilitation effect on gas exchange derived from the support modification and interfacial polymerization modulation. This work provides a composite membrane simultaneously with significant plasma leakage resistance and anticoagulation properties for efficient blood oxygenation.

Probing the Degree of Restriction in Solvent Dynamics at the Interface of a Protein-RNA Complex.

Protein-RNA complexation is an important step for the regulation of numerous biological processes. Water present at the interface of a protein-RNA complex plays a critical role in guiding its structure, stability, and function. Therefore, studying the microscopic properties of interfacial water is essential to gain molecular insights into the formation of such complexes. In this study, we present results obtained from molecular dynamics (MD) simulations of poly(A)-binding protein (PABP) bound with poly(A) RNA, which is an essential regulatory step to control the deadenylation process, thereby stabilizing cellular mRNAs from degradation. Efforts have been made to explore how such complexation alters the regular dynamical and hydrogen bond properties of water present at the interface. The calculations revealed restricted water dynamics at the interface, characterized by heterogeneous time scales, with the extent of restriction being more pronounced for residues directly involved in protein-RNA binding. In particular, water molecules around the protein's linker, RRM2, and the RNA strand exhibit significantly more restricted motion compared to RRM1 upon complexation. Further, longer relaxation times of hydrogen bonds at the interface due to complex formation have been found to be correlated with increasingly restricted water motions. Notably, the kinetics of hydrogen bonds around the protein's linker, RRM2, and the RNA strand are more strongly influenced by complex formation, underscoring their critical role in mediating protein-RNA interactions.

Elucidation of an Unusually Long Pu-N Bond in a Plutonium(III)-Tetrazolate Complex.

Four trivalent, f-element tetrazolate hydrate complexes [M(H2O)9](Hdtb)3·nH2O (Nd1, n = 7 and Pu1, n = 9; dtb2- = 1,3-di(tetrazolate-5-yl)benzene) and [M(Hdtb)(H2O)8](dtb)·11H2O (Nd2 and Pu2) were prepared using metathesis reactions. These complexes contain hydrated M(III) cations, but in the latter complexes, Nd2 and Pu2, one of the water molecules has been displaced by a long interaction between the M(III) cation and a Hdtb- anion. Notably, the Pu(III)-N bond in Pu2, representing the longest IXPu(III)-N (IX = nine coordinate) bond reported has a length of 2.8338(15) Å and is slightly shorter than the Nd(III)-N bond length of 2.8425(13) Å in Nd2. Analysis of bond lengths, Wiberg bond indices (WBI), natural localized molecular orbitals (NLMOs), and quantum theory of atoms in molecules (QTAIM) reveals that the metal contribution to the Pu(III)-N bond is marginally greater than that of the Pu(III)-OH2 bonds in Pu2 and the Nd(III)-N bond in Nd2. Thus, this rather long M-N interaction provides an example where the expectation that An(III) compounds exhibit greater covalency with soft donor ligands compared to harder ligands fails. The absorption spectra of Pu1 and Pu2 further support this observation, highlighting a surprising degree of similarity in their electronic structures.

Water flipping and the oxygen evolution reaction on Fe2O3 nanolayers

Hematite photoanodes are promising for the oxygen evolution reaction, however, their high overpotential (0.5-0.6 V) for water oxidation and limited photocurrent make them economically unviable at present. The work needed to orient dipoles at an electrode surface may be an overlooked contribution to the overpotential, especially regarding dipoles of water, the electron source in the oxygen evolution reaction (OER). Here, we employ second harmonic amplitude and phase measurements to quantify the number of net-aligned Stern layer water molecules and the work associated with water flipping, on hematite, an earth abundant OER semiconductor associated with a high overpotential. At zero applied bias, the pH-dependent potentials for Stern layer water molecule flipping exhibit Nernstian behavior. At positive applied potentials and pH 13, approximately one to two monolayers of water molecules points the oxygen atoms towards the electrode, favorable for the OER. The work associated with water flipping matches the cohesive energy of liquid water (44 kJ mol-1) and the OER current density is highest. This current is negligible at pH 5, where the work approaches 100 kJ mol-1. Our findings suggest a causal relationship between the need for Stern layer water flipping and the OER overpotential, which may lead to developing strategies for decreasing the latter.

Investigation of the Boundary Value Problem for an Extended System of Stationary Nernst–Planck–Poisson Equations in the Diffusion Layer

This article investigates the boundary value problem for an extended stationary system of Nernst–Planck–Poisson equations, corresponding to a mathematical model of the influence of changes in the equilibrium coefficient on the transport of ions of a binary salt in the diffusion layer. Dimensionless variables were introduced using characteristic parameter values. As a result, a dimensionless boundary value problem was obtained, which is singularly perturbed, containing a small parameter in the derivative of the Poisson equation and, additionally, another regular small parameter. A similarity theory was developed: trivial and non-trivial similarity criteria and their physical meaning were determined, which allowed for the identification of general properties of the solutions. A numerical investigation of the boundary value problem was conducted using the finite element method. With an increase in the initial solution concentration, the value of the small parameter entering singularly decreases, reaching values on the order of 10−12 and below, leading to computational difficulties that prevent a comprehensive analysis of the influence of changes in the equilibrium coefficient on salt ion transport. In this regard, an analytical solution to the problem was constructed, based on dividing the solution domain into several subdomains (regions of electroneutrality, extended space charge region, quasi-equilibrium region, recombination region, intermediate layer), in each of which the problem is solved differently, followed by matching these solutions. Verification of the analytical solution was carried out by comparing it with the numerical solution. The advantage of the obtained analytical solution is the possibility of a comprehensive analysis of the influence of the dissociation/recombination reaction of water molecules on salt ion transport over a wide range of real changes in the concentration and composition of the electrolyte solution and other input parameters. This boundary value problem serves as a benchmark for constructing asymptotic solutions for other singularly perturbed boundary value problems in membrane electrochemistry.

In Situ Time-Resolved X-ray Absorption Spectroscopy Unveils Partial Re-Oxidation of Tellurium Cluster for Prolonged Lifespan in Hydrogen Evolution.

Efficient and long-lasting electrocatalysts are one of the key factors in determining their large-scale commercial viability. Although the fundamentals of deactivation and regeneration of electrocatalysts are crucial for understanding and sustaining durable activity, little has been conducted on metalloids compared to metal-derived ones. Herein, by virtue of in situ seconds-resolved X-ray absorption spectroscopy, we discovered the chemical evolution during the deactivation-regeneration cycles of tellurium clusters supported by nitrogen-doped carbon (termed Te-ACs@NC) as a high-performance electrocatalyst in the hydrogen evolution reaction (HER). Through in situ electrochemical reduction, Te-ACs@NC, which had been deactivated due to surface phase transitions in a previous HER process, was reactivated and regenerated for the next run, where partially oxidized Te was found, surprisingly, to perform better than its nonoxidized state. After 10 consecutive deactivation-regeneration cycles over 480 h, the Te-ACs@NC retained 85% of its initial catalytic activity. Theoretical studies suggest that local oxidation modulates the electronic distribution within individual Te clusters to optimize the adsorption energy of water molecules and reduce dissociation energy. This study provides fundamental insights into the rarely explored metalloid cluster catalysts during deactivation and regeneration and will assist in the future design and development of supported catalysts with high activity and long durability.

Analysis of the Wetting Behavior and Kinetic Mechanism of Non-Ionic Surfactants on the Micro Interface of Coal: A Case Study.

This study addresses the issue of varying the wetting effects of surfactants in coal dust control. Utilizing low-field nuclear magnetic resonance (LF-NMR) experiments and molecular dynamics (MD) simulations, it reveals the microscopic wetting mechanism of nonionic surfactant fatty alcohol polyoxyethylene ether (JFCS) on different coal ranks. The results indicate that JFCS can reduce the attractive forces between molecules on the coal surface, promoting the diffusion of water molecules at the coal interface. The wetting effect of JFCS on lignite is superior to that on bituminous coal. The wetting range and diffusion rate of water molecules in the surfactant system were obtained, elucidating the microscopic wetting mechanism and influencing the laws of different coal ranks under the action of surfactants. This provides excellent theoretical guidance for coal seam water injection dust prevention, improves the effectiveness and pertinence of mine dust control, and contributes to the improvement of cleaner production levels in mines.

Signatures of rotation-translation couplings, symmetry-breaking, and intermolecular interactions in the rovibrational spectra of solid H2O@C60.

Some spectral features observed in the rovibrational spectra of solid H2O@C60 are shown to provide spectroscopic signatures of confinement-induced perturbations related to the coupling between the orientational and positional degrees-of-freedom of the water molecules. Their attribution to either para-H2O@C60 or ortho-H2O@C60 is established from their behavior during nuclear spin conversion. The frequency of the rovibrational transitions that emanate from their ground ro-translational (RT) states appears conspicuously redshifted from that of the corresponding transitions in the free water molecule in the gas phase. However, a few of the 21 hot band spectral features, and one ground state transition, observed in the infrared spectrum of solid H2O@C60 and reported here for the first time, cannot be straightforwardly assigned based on the softening of its intramolecular HOH bending and OH stretching vibrational modes due to confinement within C60. The most strongly perturbed transitions provide insights into the complex confinement-induced quantum nuclear dynamics arising from rotation-translation coupling, allowing the topology of the confinement potential to be revealed using a simple confined rotor model [Putaud et al., J. Chem. Phys. 162, 144313 (2025)]. While the line profiles exhibited by most of the transitions are consistent with symmetry-breaking interactions arising from merohedral disorder in solid H2O@C60, evidence for additional perturbations of the 10100 RT state, in the ground and vibrationally excited manifolds, is reported. Moreover, the line profiles displayed by the transitions emanating from the ground RT state of para-H2O@C60 and the observation of nominally forbidden Q-branch transitions, in the intramolecular HOH bending and symmetric OH stretching ranges of solid H2O@C60 samples with a fill ratio of 75%, are shown to provide a spectroscopic signature of intermolecular dipolar interactions between nearest-neighbor H2O@C60 molecules.

Dinuclear oxido-bridged iron(III) complexes containing sulfato ligands

Abstract A new iron(III) sulfato complex [Fe2(bpy)2(H2O)2(µ-O)(µ-SO4)2]·3H2O has been prepared from iron(II) chloride by using potassium peroxydisulfate being the oxidation agent and the source of sulfato ligands as well. The compound has been characterized by infrared, Raman and Mössbauer spectroscopies. X-ray structure analysis confirmed the presence of the Fe(III)–O–Fe(III) core in the complex. Both sulfato groups are bonded in the form of bridged bis(monodentate) ligands. The coordination polyhedra about the central atoms are completed by 2,2′-bipyridine and water molecules, forming thus distorted octahedra. A thorough comparison of bonding parameters of all dinuclear oxido-bridged sulfato complexes of iron(III) that have been solved by X-ray structure analysis revealed several strong correlations between these parameters and bonding mode of sulfato ligands. The characteristic vibrational bands of the FeOFe group has been observed at 770 cm−1 (IR) for νas(FeOFe) and at 513 cm−1 (IR) and 520 cm−1 (Raman) for νs(FeOFe). The assignment of characteristic bands was corroborated by DFT calculation. The isomer shift values obtained in Mössbauer spectra indicate high-spin Fe3+, while the large quadrupole splitting is characteristic of oxygen bridged Fe3+ ions.

Highly Efficient Charge Transfer between Water and Two-Dimensional Materials with Polar Bonds.

Charge transfer at solid-liquid interfaces is pivotal in biochemical processes, catalysis, and electrochemical devices. However, understanding the charge transfer mechanism at the nanoscale solid-liquid interface remains highly challenging. Here, we conduct ab initio molecular dynamics simulations to investigate interfacial charge transfer between water and the two most common two-dimensional materials: graphene with nonpolar C-C bonds and hexagonal boron nitride (hBN) with polar B-N bonds. It is counterintuitive to find that the charge transfer between water and hBN is approximately 1 order of magnitude higher than that between water and graphene despite the fact that graphene is semiconducting and hBN is insulating. Our further analyses attribute this phenomenon to a higher tendency of water molecules to point a hydrogen atom toward the hBN surface compared to the graphene surface, although they have similar crystallographic structures. This single hydrogen-down water configuration on the hBN surface prompts electron delocalization from hBN and facilitates electron migration to water. Moreover, the polar B-N bonds in hBN result in a strong orbital overlap between nitrogen atoms and hydrogen atoms of water. A similar charge transfer enhancement is also observed between water and two-dimensional gallium nitride (GaN) and aluminum nitride (AlN), which also own polar bonds, and a positive correlation between the charge transfer and the bond polarity is demonstrated. Further simulations indicate that the friction coefficient of water on graphene and hBN surfaces positively correlates with the amount of charge transfer. These findings suggest that materials with polar bonds like hBN can serve as promising materials for biochemical sensors and energy conversion devices.

Water-Stable MIL-MOFs Developed Through a Novel Sacrifice-Protection Strategy Inspired by Butterfly Wings' Scales for Long-Term Turn-On Fluorescence Sensing of H2S.

Metal-organic frameworks, which are the desired candidates for biosensing application due to their tunable properties, are significantly hindered by their rapid degradation in aqueous solutions, as well as the loss of their inherent fluorescence. Most studies aim to improve the hydrophobicity of materials by modifying their contact angle, thereby enhancing water stability. However, water droplets poorly adhere to the surface of hydrophobic materials, limiting their application for direct contact and detection in aqueous environments. Drawing inspiration from the sacrificial protection mechanism of butterfly wings used to evade predation and entanglement, a universal approach is successfully developed to protect water-sensitive MIL-MOFs from water molecule attack while preserving good hydrophilicity. Using the organic ligand 2,2'-bipyridine-5,5'-dicarboxylic acid (bpydc) as sacrificial protection scales, the MIL-125-NH2-bpydc demonstrated broad pH structural stability (pH 2-12) and fluorescence stability increased by 10.17 time in aqueous solutions, achieving the highest performance in MILMOFs. The MIL-125-NH2-bpydc is biocompatible enabling it to perform long-term fluorescence imaging in living cells and zebrafish, further detecting hydrogen sulfide (H2S) in the aqueous and biological systems via turn-on fluorescence emission. This study offers a novel and universal sacrifice-protection strategy for the design and development of the luminescent biocompatible MOFs tailored for biosensing applications.

Photophysics of meta- and para-nitrophenolate. I. The role of configuration, microsolvation, and solvation on the charge transfer transition.

The structure of the first five singlet excited electronic states of meta-nitrophenolate (m-NP) and para-nitrophenolate (p-NP) is investigated here in the gas phase, micro-solvent, and bulk solvent environments. The first excited state (S1) of m-NP was found to be a charge transfer state in the gas phase, whereas that of p-NP is a ππ* state. A stronger coupling between the donor and acceptor molecular orbitals in p-NP leads to a higher excitation energy of the S1 state as compared to m-NP. An examination of the topography of the potential energy surfaces reveals low energy conical intersections of the S1 state with the S2 and S3 states in p-NP. Such conical intersections in m-NP are located at higher energies relative to the S1 state minimum. Repulsion between the S1(1A') and S2(1A″) electronic states via the out-of-plane -NO2 torsional mode leads to a symmetrical double well topography of the S1 state of m-NP. Present results establish that while a single solvent molecule like water, methanol, and acetonitrile leads to a blue shift in the first absorption band maxima of m-NP, the electronic localization on the donor molecular orbital due to a single water molecule yields a red shift in the first absorption band of p-NP. However, the attachment of a single water molecule to the nitro site of p-NP facilitates electronic delocalization, leading to a blue shift in the S1 state excitation energy. As a result, in an aqueous medium, the first absorption band maximum was observed very near to that found in bare p-NP.

Coarse-grained simulation of water: A comparative study and overview.

In spite of the tremendous increase in computational power over the last few decades, the problem of simulating atomistic systems containing large amounts of water molecules over longer lengths and time scales still remains. In this respect, the coarse-grained (CG) force field reduces the computational cost and, therefore, allows simulations of larger systems for longer times. However, the specific scope of the different CG water models is more limited compared to their atomistic counterparts. In this context, we conducted a comparative study on the molecular physical structure, thermodynamic, and dynamic properties of bulk water systems using six distinct CG water models and all-atom (AA) simulations. The six CG simulation procedures involved modeling with three variants of the water model coming from the MARTINI force field, one from the SPICA force field, and the two Iterative Boltzmann Inversion (IBI) derived potentials from the AA simulations. The AA simulations have been performed using the SPC/E and TIP4P force fields. The IBI models, namely SPC/E-IBI and TIP4P-IBI, depict the structural features in close agreement with the atomistic samples. The explicit number of water molecules in the first coordination shell for the three MARTINI models and the SPICA force field is in excellent agreement with the SPC/E and TIP4P values. The ensuing simulated densities for the various water models align significantly with the literature data, indicating the reliability of our approach. The SPC/E and SPICA models stand out in predicting the enthalpy of vaporization among the all-atom and CG force fields, respectively. The two all-atom models and their IBI equivalents are better at representing the isobaric specific heat capacity compared to the other models. The isothermal compressibility is reproduced comprehensively by the SPC/E force field followed by TIP4P, while SPICA is the better choice within the CG models. With respect to the dynamics of the system, the diffusion coefficient of the SPICA force field is in perfect agreement with the experimental data, even better than the atomistic samples. The overall scores of the different models, indicative of their relative performances compared to the other models, have also been computed.

Linear-scaling quadruple excitations in local pair natural orbital coupled-cluster theory.

We present a fast, asymptotically linear-scaling implementation of the perturbative quadruples energy correction in coupled-cluster theory using local natural orbitals. Our work follows the domain-based local pair natural orbital (DLPNO) approach previously applied to lower levels of excitations in coupled-cluster theory. Our DLPNO-CCSDT(Q) algorithm uses converged doubles and triples amplitudes from a preceding DLPNO-CCSDT computation to compute the quadruples amplitude and energy in the quadruples natural orbital (QNO) basis. We demonstrate the compactness of the QNO space, showing that more than 95% of the (Q) correction can be recovered using relatively loose natural orbital cutoffs, compared to the tighter cutoffs used in pair and triples natural orbitals at lower levels of coupled-cluster theory. We also highlight the accuracy of our algorithm in the computation of relative energies, which yields deviations of sub-kJ mol-1 in relative energy compared to the canonical CCSDT(Q). Timings are conducted on a series of growing linear alkanes (up to 10 carbons and 608 basis functions) and water clusters (up to 49 water molecules and 2842 basis functions) to establish the asymptotic linear-scaling of our DLPNO-(Q) algorithm.

A simple confined rotor model to describe the ro-translational dynamics of water endofullerenes and to assign the ro-vibrational spectra of solid H2O@C60.

A simple Confined Rotor Model (CRM) is used to assign the thirty-nine ro-vibrational transitions observed through the HOH bending and OH stretching ranges of the solid H2O@C60 mid-infrared (MIR) spectra reported in the companion paper [Chartrand et al., J. Chem. Phys. (unpublished) (2024)]. Assuming that the intramolecular vibrations of the water molecules are separable from their rotational and translational motions, the CRM Hamiltonian describes confinement of H2O within C60 as an eccentric, but otherwise isotropic, 3D harmonic oscillator and as an asymmetric rigid rotor. The topology of the effective confinement potential is constrained using seven transitions observed in the HOH bending range of the MIR spectra of solid H2O@C60, yielding an effective force constant, k = (11.86 ± 0.03)Jm-2, and an eccentricity, dCI = (7.55 ± 0.07)pm, in good agreement with DF-LMP2/cc-pVDZ results. While twenty-one broad and overlapping spectral features arising from hot band transitions were described and tentatively assigned by Chartrand et al., some of them appear very strongly perturbed compared to the gas phase. Using the CRM, it is shown that the conspicuous shifts displayed by certain very specific pairs of ro-vibrational transitions provide evidence for confinement-induced rotation-translation coupling between the orientational and positional degrees-of-freedom of endohedral water, resulting in a strong mixing between very specific pairs of ro-translational eigenstates of translational and rotational character. The CRM is shown to provide a satisfactory description of all observed ro-vibrational transitions along with a compelling interpretation for the complex confinement-induced quantum nuclear dynamics of endohedral water as revealed by the rotational and ro-vibrational spectra of solid H2O@C60.

Water‐in‐acid Strategy for Corrosion‐Free Proton Storage: Phosphoric Acid Electrolyte Engineering Toward Sustainable Aqueous Batteries

Aqueous proton batteries, leveraging the intrinsic advantages of protons such as minimal hydrated radius, natural abundance, and rapid transport kinetics, have emerged as promising candidates for next‐generation energy storage. However, conventional strong acid electrolytes like H2SO4 suffer from critical limitations including electrode dissolution and incompatibility with battery components. To circumvent these challenges, weak acids (e.g., HCOOH and H3PO4) have been strategically selected as alternative electrolytes due to their non‐corrosive characteristics. Particularly, the implementation of a high‐concentration "water‐in‐acid" (WIA) effectively suppresses undesirable interactions between electrode materials and free water molecules. Through electrolyte engineering, we developed a 9.5 M H3PO4 WIA system that synergizes with a molybdenum trioxide electrode, achieving remarkable electrochemical performance: a high reversible capacity of 229.8 mAh g‐1 at 3 A g‐1 and exceptional cycling stability with 83.86% capacity retention after 1,000 cycles at 5 A g‐1, surpassing conventional H2SO4‐based systems by both capacity and cyclability. This innovative approach establishes a new paradigm for developing high‐performance aqueous energy storage systems through acid‐dominated electrolyte design.

Water-in-acid Strategy for Corrosion-Free Proton Storage: Phosphoric Acid Electrolyte Engineering Toward Sustainable Aqueous Batteries.

Aqueous proton batteries, leveraging the intrinsic advantages of protons such as minimal hydrated radius, natural abundance, and rapid transport kinetics, have emerged as promising candidates for next-generation energy storage. However, conventional strong acid electrolytes like H2SO4 suffer from critical limitations including electrode dissolution and incompatibility with battery components. To circumvent these challenges, weak acids (e.g., HCOOH and H3PO4) have been strategically selected as alternative electrolytes due to their non-corrosive characteristics. Particularly, the implementation of a high-concentration "water-in-acid" (WIA) effectively suppresses undesirable interactions between electrode materials and free water molecules. Through electrolyte engineering, we developed a 9.5 M H3PO4 WIA system that synergizes with a molybdenum trioxide electrode, achieving remarkable electrochemical performance: a high reversible capacity of 229.8 mAh g-1 at 3 A g-1 and exceptional cycling stability with 83.86% capacity retention after 1,000 cycles at 5 A g-1, surpassing conventional H2SO4-based systems by both capacity and cyclability. This innovative approach establishes a new paradigm for developing high-performance aqueous energy storage systems through acid-dominated electrolyte design.

Double-layer capacitance peaks: Origins, ion dependence, and temperature effects.

Differential capacitance (Cdl) is arguably the most important lumped parameter of electrical double layers (EDLs). Two peaks in the Cdl profile have been commonly attributed to the crowding of counterions within the EDL. More recent studies have suggested that the two peaks are primarily caused by orientational polarization of interfacial water molecules. Herein, this recent perspective is extended by considering orientation-dependent adsorption free energy of water and tested at Au(111)-aqueous solution interfaces. Our comparative analysis of the ion dependency of the Cdl profile corroborates the view that the capacitance peaks are caused mainly by the saturation of the orientational polarization of interfacial water molecules. In addition, the temperature dependency of the Cdl profile is consistently interpreted as a consequence of the temperature effects on the orientational polarization of interfacial water.