Search

The advancement of bio‐ionotronics for the brain‐computer interaction necessitates an exploration of the mechanisms of electron‐ion coupled transport in solid state devices. In this study, a bio‐p–n junction composed of n‐type bacteriorhodopsin and p‐type P3HT are proposed. By leveraging electron‐proton synergistic effects, an opto‐ionotronic bio‐diode capable of performing ionotronic switching and rectification functions is fabricated. The switching behavior of the bio‐diode can be controlled both optically and electrically. Under light illumination, the ionotronic bio‐diode exhibits a rectification effect approaching that of an ideal diode, with a reliability of 99% and a rectification ratio of ≈661. Additionally, this bio‐organic composite ionotronic bio‐diode exhibits wide pH responsiveness, good photostability, and high biocompatibility. The proposed opto‐ionotronic bio‐diode can be utilized as a fundamental component in logic circuits, bridging the gap between semiconductor technology and biological systems, and represents a novel paradigm for the advancement of brain‐computer interaction. [ABSTRACT FROM AUTHOR]

Human voltage-gated proton (hHv1) channels are crucial for regulating essential biological processes such as immune cell respiratory burst, sperm capacitation, and cancer cell migration. Despite the significant concentration difference between protons and other ions in physiological conditions, hHv1 demonstrates remarkable proton selectivity. Our calculations of single-proton, cation, and anion permeation free energy profiles quantitatively demonstrate that the proton selectivity of the wild-type channel originates from its strong proton affinity via the titration of the key residues D112 and D174, although the channel imposes similar kinetic blocking effects for protons compared to other ions. A two-proton knock-on model is proposed to mathematically explain the electrophysiological measurements of the pH-dependent proton conductance in the conductive state. Moreover, it is shown that the anion selectivity of the D112N mutant channel is tied to impaired proton transport and substantial anion leakage. [ABSTRACT FROM AUTHOR]

BaZrO 3 -based oxides have attracted attention due to their intrinsic properties that allow protons to traverse. To accelerate proton conduction, a novel BaZr 0.5 Gd 0.25 Y 0.25 O 3 (BZGY) material is proposed as the electrolyte of proton ceramic fuel cells (PCFCs). The electronic structure, synergistic effect and proton transport mechanism of Gd and Y co-doped BaZrO 3 are theoretically studied. Y-doping and Gd-doping promote the formation of oxygen vacancies and the entry of H 2 O molecules into the structure and binding to oxygen vacancies, respectively. The co-doping of Y and Gd promotes the hydration process and increases the proton concentration. The binding of Gd or Y to the oxygen vacancy around the acceptor inhibits proton trapping. BZGY shows rapid and long-distance transport of protons. BZGY has obtained high proton concentrations and mobility, which fully support its potential application in next-generation PCFCs. The synergistic effects of Gd and Y co-doped BaZrO 3 provide important theoretical significance for the study of proton electrolytes. [ABSTRACT FROM AUTHOR]

Illuminated giant cells of Characeae produce alternating areas with H+-pump activity and zones of high H+/OH– conductance, where H+ fluxes between the medium and the cytoplasm are oppositely directed. In areas where proton equivalents enter the cell, the pH on cell surface (pHo) increases to pH 10, while the cytoplasmic pH (pHc) decreases. Deficiency of the permeant substrate of photosynthesis (CO2) and the acidic pHc shift under external alkaline zones promote the redirection of electron transport in chloroplasts from CO2-dependent assimilatory pathway to O2 reduction. This bypass route of electron transport elevates the thylakoid membrane ΔpH and enhances nonphotochemical quenching (NPQ) of chlorophyll excitations, which determines strict coordination between nonuniform distributions of pHo and photosynthetic activity in resting cells. When the action potential (AP) is generated, the longitudinal pH profile is temporarily smoothed out, while the heterogeneous distribution of NPQ and PSII photochemical activity (YII) becomes drastically sharpened. The damping of the pHo profile is due to the suppression of the H+-pump and passive H+/OH– conductance under the influence of an almost 100-fold increase in the cytoplasmic Ca2+ level ([Ca2+]c) during AP. The increase in [Ca2+]c stimulates photoreduction of O2 in chloroplasts underlying external alkaline zones and, at the same time, arrests the cytoplasmic streaming, which lead to the accumulation of excess amounts of H2O2 in the cytoplasm in areas of intense production of this metabolite and has a weak effect on areas of CO2 assimilation. These changes enhance the nonuniform distribution of cell photosynthesis and account for long-term oscillations of chlorophyll fluorescence and the quantum efficiency of linear electron flow on microscopic cell areas after the AP generation. [ABSTRACT FROM AUTHOR]

Organic bilayers or amorphous silica films of a few nanometer thickness featuring embedded molecular wires offer opportunities for chemically separating while at the same time electronically connecting photo- or electrocatalytic components. Such ultrathin membranes enable the integration of components for which direct coupling is not sufficiently efficient or stable. Photoelectrocatalytic systems for the generation or utilization of renewable energy are among the most prominent ones for which ultrathin separation layers open up new approaches for component integration for improving efficiency. Recent advances in the assembly and spectroscopic, microscopic, and photoelectrochemical characterization have enabled the systematic optimization of the structure, energetics, and density of embedded molecular wires for maximum charge transfer efficiency. The progress enables interfacial designs for the nanoscale integration of the incompatible oxidation and reduction catalysis environments of artificial photosystems and of microbial (or biomolecular)-abiotic systems for renewable energy.

[Display omitted] • A strategy for MOF-composite nanofiber with synergistic architecture is proposed. • PU@PAN/UiO-66 core/shell nanofiber is prepared by coaxial electrospinning. • 3D proton-conduction networks are constructed in proton exchange membrane. • Sulfamic acid is successfully introduced on nanofiber. • The maximum power density of Nafion/S@NF-50 exhibits 182.6 mW cm−2. Proton exchange membranes (PEMs) play an important role in fuel cells. For realizing a nanofiber (NF) structure design in PEMs, the material should have tunable pores and a high specific area. In this study, we attempt to design a novel NF with synergistic architecture doped MOF for constructing three-dimensional (3D) proton conduction networks in PEMs. In this framework, UiO-66-COOH serves as a platform for proton sites to synergistically promote proton conductivity via polyvinylpyrrolidone dissolution, hydrolyzation of polyacrylonitrile, and sulfamic acid functionalization of the shell-layer NF. Benefiting from enriched proton-transfer sites in NFs, the obtained composite membrane overcomes the trade-off among proton conductivity, methanol permeability, and mechanical stability. The composite membrane with 50 % fiber (Nafion/S@NF-50) exhibited a high proton conductivity of 0.212 S cm−1 at 80 °C and 100 % relative humidity, suppressed methanol permeability of 0.66 × 10−7 cm2 s−1, and the maximum power density of direct methanol fuel cell is 182.6 mW cm−2. Density functional theory was used to verify the important role of sulfamic acid in proton transfer, and the activation energy barriers under anhydrous and hydrous conditions are only 0.337 and 0.081 kcal, respectively. This study opens up new pathways for synthesizing NF composite PEMs. [ABSTRACT FROM AUTHOR]

Mitochondrial uncoupling by small molecule protonophores is a promising strategy for developing novel anticancer agents. Recently, aryl urea substituted fatty acids (aryl ureas) were identified as a new class of protonophoric anticancer agents. To mediate proton transport these molecules self‐assemble into membrane‐permeable anionic dimers in which intermolecular hydrogen bonds between the carboxylate and aryl‐urea anion receptor delocalise the negative charge across the aromatic π‐system. In this work, we extend the aromatic π‐system by introducing a second phenyl substituent to the aryl urea scaffold and compare the proton transport mechanisms and mitochondrial uncoupling actions of these compounds to their monoaryl analogues. It was found that incorporation of meta‐linked phenyl substituents into the aryl urea scaffold enhanced proton transport in vesicles and demonstrated superior capacity to depolarise mitochondria, inhibit ATP production and reduce the viability of MDA‐MB‐231 breast cancer cells. In contrast, diphenyl ureas linked through a 1,4‐distribution across the phenyl ring displayed diminished proton transport activity, despite both diphenyl urea isomers possessing similar binding affinities for carboxylates. Mechanistic studies suggest that inclusion of a second aryl ring changes the proton transport mechanism, presumably due to steric factors that impose higher energy penalties for dimer formation. [ABSTRACT FROM AUTHOR]

Electrochemical nitrate reduction reaction (NO3RR) is a promising approach to achieve remediation of nitrate‐polluted wastewater and sustainable production of ammonia. However, it is still restricted by the low activity, selectivity and Faraday efficiency for ammonia synthesis. Herein, we propose an effective strategy to modulate the electrolyte microenvironment in electrical double layer (EDL) by mediating alkali metal cations in the electrolyte to enhance the NO3RR performance. Taking bulk Cu as a model catalyst, the experimental study reveals that the NO3−‐to‐NH3 performance in different electrolytes follows the trend Li+

Structural change of ions induced by collision with a neutral has been studied in a guided ion beam tandem mass spectrometer, using Time‐Of‐Flight measurements and SIMION simulation. The exothermic catalytic isomerization of HOC+ to HCO+ is used to explore the new methodology. Isomerization is catalyzed via a proton transport mechanism through the interplay of a neutral molecule, the catalyst. Four different potential catalysts, Ne, D2, CH4, and C18O, were studied at different collision energies. SIMION simulation of the ion path and collision in the instrument leads to the highlight of a specific signature related to the catalytic isomerization in the time‐of‐flight spectra. This signature is used to identify the experimental conditions where isomerization takes place. Only C18O, at low collision energies, gives a clear signature of catalytic isomerization, and a quantitative estimate of the catalyzed isomerization cross‐section and rate constant is derived. This new methodology is sensitive to clear presence of catalyzed isomerization and can be used in instruments designed for cross‐section measurements, provided low collision energy is used and ion bunching is available. [ABSTRACT FROM AUTHOR]

Aims: Metabolic reprogramming in cancer cells has been linked to mitochondrial dysfunction. The mitochondrial 2‐oxoglutarate/malate carrier (OGC) has been suggested as a potential target for preventing cancer progression. Although OGC is involved in the malate/aspartate shuttle, its exact role in cancer metabolism remains unclear. We aimed to investigate whether OGC may contribute to the alteration of mitochondrial inner membrane potential by transporting protons. Methods: The expression of OGC in mouse tissues and cancer cells was investigated by PCR and Western blot analysis. The proton transport function of recombinant murine OGC was evaluated by measuring the membrane conductance (Gm) of planar lipid bilayers. OGC‐mediated substrate transport was measured in proteoliposomes using 14C‐malate. Results: OGC increases proton Gm only in the presence of natural (long‐chain fatty acids, FA) or chemical (2,4‐dinitrophenol) protonophores. The increase in OGC activity directly correlates with the increase in the number of unsaturated bonds of the FA. OGC substrates and inhibitors compete with FA for the same protein binding site. Arginine 90 was identified as a critical amino acid for the binding of FA, ATP, 2‐oxoglutarate, and malate, which is a first step towards understanding the OGC‐mediated proton transport mechanism. Conclusion: OGC extends the family of mitochondrial transporters with dual function: (i) metabolite transport and (ii) proton transport facilitated in the presence of protonophores. Elucidating the contribution of OGC to uncoupling may be essential for the design of targeted drugs for the treatment of cancer and other metabolic diseases. [ABSTRACT FROM AUTHOR]

The biophysics of water, has been debated over more than a century. Although its importance is still underestimated, significant breakthroughs occurred in recent years. The influence of protein condensation on water availability control was documented, new findings on water-transport proteins emerged, and the way water molecules rearrange to minimize free energy at interfaces was deciphered, influencing membrane thermodynamics. The state of knowledge continued to progress in the field of deep-sea marine biology, highlighting unknown effects of high hydrostatic pressure and/or temperature on interactions between proteins and ligands in extreme environments, and membrane structure adaptations. The role of osmolytes in protein stability control under stress is also discussed here in relation to fish egg hydration/buoyancy. The complexity of water movements within the cell is updated, all these findings leading to a better view of their impact on many cellular processes. The way water flow and osmotic gradients generated by ion transport work together to produce the driving force behind cell migration is also relevant to both marine biology and cancer research. Additional common points concern water dynamic changes during the neoplastic transformation of cells and tissues, or embryo development. This could improve imaging techniques, early cancer diagnosis, and understanding of the molecular and physiological basis of buoyancy for many marine species. [ABSTRACT FROM AUTHOR]

The membrane Fo factor of ATP synthase is highly sensitive to mutations in the proton half-channel leading to the functional blocking of the entire protein. To identify functionally important amino acids for the proton transport, we performed molecular dynamic simulations on the selected mutants of the membrane part of the bacterial FoF1-ATP synthase embedded in a native lipid bilayer: there were nine different mutations of a-subunit residues (aE219, aH245, aN214, aQ252) in the inlet half-channel. The structure proved to be stable to these mutations, although some of them (aH245Y and aQ252L) resulted in minor conformational changes. aH245 and aN214 were crucial for proton transport as they directly facilitated H+ transfer. The substitutions with nonpolar amino acids disrupted the transfer chain and water molecules or neighboring polar side chains could not replace them effectively. aE219 and aQ252 appeared not to be determinative for proton translocation, since an alternative pathway involving a chain of water molecules could compensate the ability of H+ transmembrane movement when they were substituted. Thus, mutations of conserved polar residues significantly affected hydration levels, leading to drastic changes in the occupancy and capacity of the structural water molecule clusters (W1–W3), up to their complete disappearance and consequently to the proton transfer chain disruption. [ABSTRACT FROM AUTHOR]

Fast proton conduction plays an essential role in ion conductive membranes (ICMs) for energy conversion and storage technologies, but the demand for low reactive species permeation always limits further enhancement in proton transport rate. Herein, an ICM incorporating ZSM‐5 zeolite with optimized physicochemical property of pore channels was developed to achieve highly conductive ion transport via regulating the silicon‐aluminum atomic (Si/Al) ratio of ZSM‐5. Benefiting from the regulation of pore channels of zeolites, the proton conductivity of the pristine membrane was remarkably improved to 1.7‐fold. As expected, the optimized membrane exhibited outstanding voltage efficiency (VE) of 85.7% and energy efficiency (EE) of 85.1% at 120 mA/cm2, which is considerably better than pure polymer membrane (VE of 80.5% and EE of 79.4%) and commercial Nafion 212 (VE of 81.3% and EE of 77.4%) membrane, respectively. [ABSTRACT FROM AUTHOR]

The perfluorosulfonic acid (PFSA) membrane doped with two-dimensional conductive filler Ti3C2Tx is a fuel cell proton exchange membrane with high application potential. Experimental studies showed that the proton conductivity of Nafion/Ti3C2Tx composite membrane is improved significantly compared with that in pure Nafion. However, the microscopic mechanism of doping on the enhancement of membrane performance is remain unclear now. In this work, molecular dynamics simulation was used to investigate the microscopic morphology and proton transport behaviors of Nafion/Ti3C2Tx composite membrane at the molecular level. The results shown that there were significant differences about the diffusion kinetics of water molecules and hydroxium ions in Nafion/Ti3C2Tx at low and high hydration levels in the nanoscale region. With the increase of water content, Ti3C2Tx in membrane was gradually surrounded by ambient water molecules to form a hydration layer, and forming a relatively continuous proton transport channel between Nafion polymer and Ti3C2Tx monomer. The continuous proton transport channel could increase the number of binding sites of proton and thus achieving high proton conductivity and high mobility of water molecules at higher hydration level. The current work can provide a theoretical guidance for designing new type of Nafion composite membranes. [ABSTRACT FROM AUTHOR]

Proton exchange membrane (PEM) is a key component of proton exchange membrane fuel cell, and its proton conductivity directly affects the performance of fuel cell. Imparting order to Nafion molecules is one of potential effective approaches that can significantly improve the proton transport performance of PEM, but the underlying mechanism of this effect as well as the regulatory mechanism is unknown. In order to investigate the regulatory mechanism of temperature, electric field, and water content on the transport mechanism of the PEM and compare the transport properties between ordered and amorphous membranes, this study examined the proton migration rate of ordered and amorphous membranes under different electric field and water contents at 300 K and 350 K with molecular dynamics methods. The simulation results indicate that the ordered PEM exhibits better proton conductivity compared with the amorphous PEM due to its ordered structure with smoothly connected proton transport channels. The proton conductivity of the ordered PEM with a water content of 16 exhibits a remarkably high proton conductivity of 0.153 S/cm at a temperature of 350 K. Additionally, it was found that increasing electric field intensity, temperature, and hydration level can enhance the diffusion of water molecules and hydrated protons and improve the proton conductivity of the PEM. Especially, at low electric field intensity, ordered PEM demonstrates superior proton conductivity compared to amorphous PEM. However, as the electric field strength increases to 0.7 V/nm, the proton diffusion behaviour of amorphous PEM gradually surpasses that of ordered PEM. Moreover, the electric field can enhance the anisotropic diffusion behaviour of PEM. As the electric field increases from 0 V/nm to 0.7 V/nm, the diffusion coefficient parallel to the direction of the electric field increases by three orders of magnitude, while the diffusion coefficient perpendicular to the direction of the electric field increases by only one order of magnitude. • Different water content systems of amorphous and ordered PEM were constructed and studied by using molecular dynamics. • The diffusion coefficient and proton conductivity of the amorphous and ordered PEM were calculated. • Increasing the order degree of Nafion molecular chain increases the proton conductivity of the proton exchange membrane. • Increasing the electric field strength, temperature and hydration level can improve the proton conductivity of the PEM. • Ordered PEM exhibits better proton conductivity than amorphous PEM at low electric field strengths. [ABSTRACT FROM AUTHOR]

The development of stimuli‐responsive artificial H+/Cl− ion channels, capable of specifically disturbing the intracellular ion homeostasis of cancer cells, presents an intriguing opportunity for achieving high selectivity in cancer therapy. Herein, we describe a novel family of non‐covalently stapled self‐assembled artificial channels activatable by biocompatible visible light at 442 nm, which enables the co‐transport of H+/Cl− across the membrane with H+/Cl− transport selectivity of 6.0. Upon photoirradiation of the caged C4F‐L for 10 min, 90 % of ion transport efficiency can be restored, giving rise to a 10.5‐fold enhancement in cytotoxicity against human colorectal cancer cells (IC50=8.5 μM). The mechanism underlying cancer cell death mediated by the H+/Cl− channels involves the activation of the caspase 9 apoptosis pathway as well as the scarcely reported disruption of the autophagic processes. In the absence of photoirradiation, C4F‐L exhibits minimal toxicity towards normal intestine cells, even at a concentration of 200 μM. [ABSTRACT FROM AUTHOR]

An in-depth understanding of the local mass transport process is essential for precisely regulating the catalyst layer structure in fuel cells. The ionomer on the Pt surface in the catalyst plays a crucial role in the local transport of oxygen and protons. While most models assume that Pt is completely covered by ionomer, experiments have indicated that Pt is partially covered by ionomer in some cause. In this paper, an improved local mass transport model is proposed to investigate the effect of ionomer coverage on internal mass transport process and fuel cell performance. The results show that the current density first increases and then decreases as the ionomer coverage rises from 10% to 90% under 0.6 V. The optimal performance is achieved with a coverage of 40%. Oxygen is more easily transported in water, while ionomer is a better proton conductor. Variations in ionomer coverage lead to different distances for oxygen and proton transfer, which have an important effect on reactant concentration. Furthermore, further study reveals that the current density is greatest at the interface between water and ionomer. Increasing the interface can effectively reduce the comprehensive transport distance of reactants in ionomer and water to improve performance, which is more pronounced than increasing the oxygen transfer coefficient in the ionomer. Overall, this study provides new ideas for the design of high-performance catalyst layers. • An improved fine-structure model of local mass transport in CCL is developed. • Simulate the effect of local oxygen and proton transport on cell performance. • The best cell performance is obtained with an ionomer coverage of 40% under 0.6 V. • Increasing the ionomer/water interface can significantly improve cell performance. • Increasing interface is more effective than enhancing oxygen diffusion in ionomer. [ABSTRACT FROM AUTHOR]

Proton‐conducting oxide materials are interesting objects from both fundamental and applied viewpoints due to the origination of protonic defects in a crystal structure as a result of their interaction with hydrogen‐containing atmospheres at elevated temperatures. The high mobility of such defects at temperatures between 400 and 700 °C leads to superior ionic conductivity. As a result, some perovskite‐type proton‐conducting oxides have been proposed as electrolytes for solid oxide fuel and electrolysis cells. Barium cerate (BaCeO3), barium zirconate (BaZrO3), and barium cerate‐zirconates (BaCeO3–BaZrO3) have been widely studied in terms of the parent phases of proton‐conducting electrolytes. Among them, Y and Yb co‐doped Ba(Ce,Zr)O3 can be identified as one of the most promising systems so far. This review discloses key functional properties of such phases and explains the increased attention of researchers to this system. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) display great potential to be assembled into proton conductive membranes for their uniform and controllable pore structure, yet constructing self‐standing COF membrane with high crystallinity to fully exploit their ordered crystalline channels for efficient ionic conduction remains a great challenge. Here, a macromolecular‐mediated crystallization strategy is designed to manipulate the crystallization of self‐standing COF membrane, where the −SO3H groups in introduced sulfonated macromolecule chains function as the sites to interact with the precursors of COF and thus offer long‐range ordered template for membrane crystallization. The optimized self‐standing COF membrane composed of highly‐ordered nanopores exhibits high proton conductivity (75 mS cm−1 at 100 % relative humidity and 20 °C) and excellent flow battery performance, outperforming Nafion 212 and reported membranes. Meanwhile, the long‐term run of membrane is achieved with the help of the anchoring effect of flexible macromolecule chains. Our work provides inspiration to design self‐standing COF membranes with ordered channels for permselective application. [ABSTRACT FROM AUTHOR]

The biophysics of water, has been debated over more than a century. Although its importance is still underestimated, significant breakthroughs occurred in recent years. The influence of protein condensation on water availability control was documented, new findings on water-transport proteins emerged, and the way water molecules rearrange to minimize free energy at interfaces was deciphered, influencing membrane thermodynamics. The state of knowledge continued to progress in the field of deep-sea marine biology, highlighting unknown effects of high hydrostatic pressure and/or temperature on interactions between proteins and ligands in extreme environments, and membrane structure adaptations. The role of osmolytes in protein stability control under stress is also discussed here in relation to fish egg hydration/buoyancy. The complexity of water movements within the cell is updated, all these findings leading to a better view of their impact on many cellular processes. The way water flow and osmotic gradients generated by ion transport work together to produce the driving force behind cell migration is also relevant to both marine biology and cancer research. Additional common points concern water dynamic changes during the neoplastic transformation of cells and tissues, or embryo development. This could improve imaging techniques, early cancer diagnosis, and understanding of the molecular and physiological basis of buoyancy for many marine species.

Monte Carlo simulation has become an effective method for solving different physical problems, which is especially advantageous in the particle transport problems with complex geometric models. Charged particle transport simulation programs based on Monte Carlo method are widely used in medical therapy, radiation protection, accelerator design and other fields. Although the domestic neutron and photon transport simulation programs are well developed, there are few programs being able to do charged particle transport simulation. In addition, the energy range for programs based on the intranuclear cascade model and evaporative fission model is usually high, above several tens of MeV. For medium and low energy proton transport, the accuracy of nuclear reaction simulations based on nuclear databases is better than that of models. The biggest problem with Monte Carlo methods for simulating charged particle transport calculations is that the number of collisions of charged particles is too frequent. Therefore, this paper was based on the condensed history method to simulate the proton transport. In this study, with the application of key physical model of charged particle transport, such as the continuous slowing down approximation theory, multiple scattering theory and energy straggling model, a framework of heavy charged particles transport simulation program was established. Based on nuclear database of ENDF/B-Ⅶ.0 proton-nucleus interactions, the proton transport simulation function was implemented on the NPTS (neutron-photon transport simulation program). The extended NPTS program supported the simulation of proton transport problems in the energy range from 1 keV to 150 MeV and multi-coupling transport calculations of protons, neutrons, photons and electrons. A comparison of the stopping power of protons, deuterons and alpha particles in common materials with SRIM was carried out by the NPTS program, which proved the correctness of NPTS in calculating the stopping power of charged particles. The numerical results of neutron yield, average energy and angle for the thick target model agree well with GEANT4, MCNP6 and experimental results. In order to fully verify the program, a proton treatment chamber model with larger spatial dimensions and more complex geometry was used for the study. The neutron flux distribution inside the treatment chamber obtained by NPTS was basically consistent with GEANT4. The accuracy of the NPTS simulations of proton transport and multiparticle coupled transport was verified by several test models. Moreover, the proton energy and continuous slowing down approximation range curves obtained from the NPTS calculations can be used to quickly estimate the target thickness at maximum neutron yield, providing a favourable reference for BNCT (boron neutron capture therapy) target design. This paper effectively extends the application of the NPTS program in accelerator target design, shielding analysis, and radiation protection. The research effectively improves the application value of NPTS program, as well as enriching the research method of medium and low energy proton transport programs in domestic.

ATP12A encodes the catalytic subunit of the non-gastric proton pump, which is expressed in many epithelial tissues and mediates the secretion of protons in exchange for potassium ions. In the airways, ATP12A-dependent proton secretion contributes to complex mechanisms regulating the composition and properties of the fluid and mucus lining the respiratory epithelia, which are essential to maintain the airway host defense and the respiratory health. Increased expression and activity of ATP12A in combination with the loss of other balancing activities, such as the bicarbonate secretion mediated by CFTR, leads to excessive acidification of the airway surface liquid and mucus dysfunction, processes that play relevant roles in the pathogenesis of cystic fibrosis and other chronic inflammatory respiratory disorders. In this review, we summarize the findings dealing with ATP12A expression, function, and modulation in the airways, which led to the consideration of ATP12A as a potential therapeutic target for the treatment of cystic fibrosis and other airway diseases; we also highlight the current advances and gaps regarding the development of therapeutic strategies aimed at ATP12A inhibition. [ABSTRACT FROM AUTHOR]

Human carbonic anhydrase II catalyzes the reversible reaction of carbon dioxide and water to form bicarbonate and a proton. His64-mediated proton shuttling between the active site and the bulk solvent is rate limiting. Here we investigate the protonation behavior of His64 as well as its structural and dynamic features in a pH dependent way. We derive two pKa values for His64, 6.25 and 7.60, that we were able to assign to its inward and outward conformation. Furthermore, we show that His64 exists in both conformations equally, independent of pH. Both conformations display an equal distribution of their two neutral tautomeric states. The life time of each conformation is short and both states display high flexibility within their orientation. Therefore, His64 is never static, but rather poised to change conformation. These findings support an energetic, dynamic and solution ensemble-based framework for the high enzymatic activity of human carbonic anhydrase II. [ABSTRACT FROM AUTHOR]

The role of protons in ATP synthase is typically considered to be energy storage in the form of an electrochemical potential, as well as an operating element proving rotation. However, this review emphasizes that protons also act as activators of conformational changes in F1 and as direct participants in phosphorylation reaction. The protons transferred through Fo do not immediately leave to the bulk aqueous phase, but instead provide for the formation of a pH gradient between acidifying Fo and alkalizing F1. It facilitates a directed inter-subunit proton transfer to F1, where they are used in the ATP synthesis reaction. This ensures that the enzyme activity is not limited by a lack of protons in the alkaline mitochondrial matrix or chloroplast stroma. Up to one hundred protons bind to the carboxyl groups of the F1 subunit, altering the electrical interactions between the amino acids of the enzyme. This removes the inhibition of ATP synthase caused by the electrostatic attraction of charged amino acids of the stator and rotor and also makes the enzyme more prone to conformational changes. Protonation occurs during ATP synthesis initiation and during phosphorylation, while deprotonation blocks the rotation inhibiting both synthesis and hydrolysis. Thus, protons participate in the functioning of all main components of ATP synthase molecular machine making it effectively a proton-driven electric machine. The review highlights the key role of protons as a coupling factor in ATP synthase with multifaceted functions, including charge and energy transport, torque generation, facilitation of conformational changes, and participation in the ATP synthesis reaction. [ABSTRACT FROM AUTHOR]

For the last decades, significant progress has been made in studying the biological functions of H-bond networks in membrane proteins, proton transporters, receptors, and photosynthetic reaction centers. Increasing availability of the X-ray crystal and cryo-electron microscopy structures of photosynthetic complexes resolved with high atomic resolution provides a platform for their comparative analysis. It allows identifying structural factors that are ensuring the high quantum yield of the photochemical reactions and are responsible for the stability of the membrane complexes. The H-bond networks are known to be responsible for proton transport associated with electron transfer from the primary to the secondary quinone as well as in the processes of water oxidation in photosystem II. Participation of such networks in reactions proceeding on the periplasmic side of bacterial photosynthetic reaction centers is less studied. This review summarizes the current understanding of the role of H-bond networks on the donor side of photosynthetic reaction centers from purple bacteria. It is discussed that the networks may be involved in providing close association with mobile electron carriers, in light-induced proton transport, in regulation of the redox properties of bacteriochlorophyll cofactors, and in stabilization of the membrane protein structure at the interface of membrane and soluble phases. [ABSTRACT FROM AUTHOR]

Mitochondrial adenine nucleotide translocase (ANT) exchanges ADP for ATP to maintain energy production in the cell. Its protonophoric function in the presence of long-chain fatty acids (FA) is also recognized. Our previous results imply that proton/FA transport can be best described with the FA cycling model, in which protonated FA transports the proton to the mitochondrial matrix. The mechanism by which ANT1 transports FA anions back to the intermembrane space remains unclear. Using a combined approach involving measurements of the current through the planar lipid bilayers reconstituted with ANT1, site-directed mutagenesis and molecular dynamics simulations, we show that the FA anion is first attracted by positively charged arginines or lysines on the matrix side of ANT1 before moving along the positively charged protein–lipid interface and binding to R79, where it is protonated. We show that R79 is also critical for the competitive binding of ANT1 substrates (ADP and ATP) and inhibitors (carboxyatractyloside and bongkrekic acid). The binding sites are well conserved in mitochondrial SLC25 members, suggesting a general mechanism for transporting FA anions across the inner mitochondrial membrane. [ABSTRACT FROM AUTHOR]

The membrane lipid composition plays an important role in the regulation of membrane protein activity. To probe its influence on proton half-channels' structure in FoF1-ATP synthase, we performed molecular dynamics simulations with the bacterial protein complex (PDB ID: 6VWK) embedded in three types of membranes: a model POPC, a lipid bilayer containing 25% (in vivo), and 75% (bacterial stress) of cardiolipin (CL). The structure proved to be stable regardless of the lipid composition. The presence of CL increased the hydration of half-channels. The merging of two water cavities at the inlet half-channel entrance and a long continuous chain of water molecules directly to cAsp61 from the periplasm were observed. Minor conformational changes in half-channels with the addition of CL caused extremely rare direct transitions between aGlu219-aAsp119, aGlu219-aHis245, and aGln252-cAsp61. Deeper penetration of water molecules (W1–W3) also increased the proton transport continuity. Stable spatial positions of significant amino acid (AA) residue aAsn214 were found under all simulation conditions indicate a prevailing influence of AA-AA or AA-W interactions on the side-chain dynamics. These results allowed us to put forward a model of the proton movement in ATP synthases under conditions close to in vivo and to evaluate the importance of membrane composition in simulations. [ABSTRACT FROM AUTHOR]

[Display omitted] Having a highly-conductive protonic electrolyte is an essential requirement of developing solid ceramic fuel cell (SCFC) operated below 600 °C. Proton transport in solid electrolyte structure occurs via a bulk conduction mechanism in conventional SCFC, which may not be so efficient; therefore we have developed a fast proton conducting NaAlO 2 /LiAlO 2 (NAO-LAO) heterostructure electrolyte, achieving the ionic conductivity of 0.23 S cm−1 thanks to its rich cross-linked solid–liquid interfaces; the SCFC employing this new developed electrolyte showed a maximum power density of 844 mW cm−2 at 550 °C, and the fuel cell could still operate at even lower temperatures down to 370 °C, although the output reduced to 90 mW cm−2. The proton-hydration liquid layer promoted the formation of cross-linked solid–liquid interfaces in the NAO-LAO electrolyte, which promoted the construction of solid–liquid hybrid proton transportation channels and effectively reduced polarization loss, leading to high proton conduction at even lower temperatures. This work provides an efficient design approach for developing enabling electrolytes with high proton conductivity for SCFCs to be operated at relatively lower temperatures (300–600 °C) than traditional solid oxide fuel cells which operate above 750 °C. [ABSTRACT FROM AUTHOR]

Nature creates aquaporins to effectively transport water, rejecting all ions including protons. Aquaporins (AQPs) has brought inspiration for the development of Artificial Water Channels (AWCs). Imidazole‐quartet (I‐quartet) was the first AWC that enabled to self‐assemble a tubular backbone for rapid water and proton permeation with total ion rejection. Here, we report the discovery of bis‐alkylureido imidazole compounds, which outperform the I‐quartets by exhibiting ≈3 times higher net and single channel permeabilities (107 H2O/s/channel) and a ≈2–3 times lower proton conductance. The higher water conductance regime is associated to the high partition of more hydrophobic bis‐alkylureido channels in the membrane and to their pore sizes, experiencing larger fluctuations, leading to an increase in the number of water molecules in the channel, with decreasing H‐bonding connectivity. This new class of AWCs will open new pathways toward scalable membranes with enhanced water transport performances. [ABSTRACT FROM AUTHOR]

Metal‐Organic frameworks (MOFs) have the advantages of high porosity, angstrom‐scale pore size, and unique structure. In this work, a kind of MOFs, UiO‐66 and its derivatives (including aminated UiO‐66‐(NH2)2 and sulfonated UiO‐66‐(NH‐SAG)2), were constructed on the inner surface of solid‐state nanopores for ultra‐selective proton transport. UiO‐66 and UiO‐66‐(NH2)2 nanocrystal particles were in‐situ grown at the orifice of glass nanopores firstly, which were used to investigate the ionic current responses in LiCl and HCl solutions when the monovalent anions (Cl−) were unchanged. Compared with UiO‐66‐modifed nanopores, the aminated MOFs modification (UiO‐66‐(NH2)2) can improve the proton selectivity obviously. However, when the UiO‐66‐(NH‐SAG)2 nanopore is prepared by further post‐modification with sulfo‐acetic acid, lithium ions can hardly pass through the channel, and the interaction between protons and sulfonic acid groups can promote the transport of protons, thus achieving ultra‐high selectivity to protons. This work provides a new way to achieve sub‐nanochannels with high selectivity, which can widely be used in ion separation, sensing and energy conversion. [ABSTRACT FROM AUTHOR]

Single molecules that co‐transport cations as well as anions across lipid membranes are few despite their high biological utility. The elegant yet simple lipidomimmetic peptide design herein enables efficient HCl transport without the use of any external additives for proton transport. The carboxylic acids in the dipeptide scaffold provide a handle to append two long hydrophobic tails and also provide a polar hydrophilic carboxylate group. The peptide central unit also provides NH sites for anion binding. Protonation of the carboxylate group coupled with the weak halide binding of the terminal NH group results in HCl transport with transport rates of H+>Cl−. The lipid‐like structure also facilitates seamless membrane integration and flipping of the molecule. The biocompatibility, design simplicity, and potential pH regulation of these molecules open up several avenues for their therapeutic use. [ABSTRACT FROM AUTHOR]

In respiring mitochondria, the proton gradient across the inner mitochondrial membrane is used to drive ATP production. Mitochondrial uncouplers, which are typically weak acid protonophores, can disrupt this process to induce mitochondrial dysfunction and apoptosis in cancer cells. We have shown that bisaryl urea-based anion transporters can also mediate mitochondrial uncoupling through a novel fatty acid-activated proton transport mechanism, where the bisaryl urea promotes the transbilayer movement of deprotonated fatty acids and proton transport. In this paper, we investigated the impact of replacing the urea group with squaramide, amide and diurea anion binding motifs. Bisaryl squaramides were found to depolarise mitochondria and reduce MDA-MB-231 breast cancer cell viability to similar extents as their urea counterpart. Bisaryl amides and diureas were less active and required higher concentrations to produce these effects. For all scaffolds, the substitution of the bisaryl rings with lipophilic electron-withdrawing groups was required for activity. An investigation of the proton transport mechanism in vesicles showed that active compounds participate in fatty acid-activated proton transport, except for a squaramide analogue, which was sufficiently acidic to act as a classical protonophore and transport protons in the absence of free fatty acids. [ABSTRACT FROM AUTHOR]

For the first time the LaIn 1- x Zn x O 3-1/2 x samples was synthesized via solid-state reaction method. The Zn2+−doping effect on the B-site of LaInO 3 on structure, water uptake and electrical properties was investigated. The results show that Zn2+ is good alternative to alkaline earth metals. The Zn-doping decreases the sintered temperature and makes it possible to obtain high-density ceramics. The substitution increases the conductivity by ∼2 orders of magnitude. Below ∼500 °C the phases exhibit the dominant oxygen-ionic transport (dry atmosphere), and the dominant protonic transport below 600 °C (wet atmosphere). The obtained results suggest the prospects for using these materials in the Hydrogen Energy field. A new concept of the ability of perovskite phases La B O 3 to incorporate water has been proposed. In addition to the presence of oxygen vacancies, their size, which depends on the B-cation nature, is of decisive importance in the hydration process and the formation of proton conductivity. [Display omitted] • LaIn 1- x Zn x O 3-1/2 x (0 ≤ x < 0.1) samples were obtained for the first time. • The water uptake value was about 90% of the concentration of oxygen vacancies. • The Zn-doping at In3+-site increases the conductivity by ∼2 orders of magnitude. • All LaIn 1- x Zn x O 3-1/2 x phases are protonic conductors at T < 600 °C in wet air. • The creation of proton transport in doped La B O 3 phases depends on the vacancy size. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Biological proton channels play important roles in the delicate metabolism process, and have led to great interest in mimicking selective proton transport. Herein, we designed a bioinspired proton transport membrane by incorporating flexible 14‐crown‐4 (14C4) units into rigid frameworks of polyimine films by an interfacial Schiff base reaction. The Young's modulus of the membrane reaches about 8.2 GPa. The 14C4 units could grab water, thereby forming hydrogen bond‐water networks and acting as jumping sites to lower the energy barrier of proton transport. The molecular chains present a vertical orientation to the membrane, and the ions travel between the quasi‐planar molecular sheets. Furthermore, the 14C4 moieties could bond alkali ions through host–guest interactions. Thus, the ion conductance follows H+≫K+>Na+>Li+, and an ultrahigh selectivity of H+/Li+ (ca. 215) is obtained. This study provides an effective avenue for developing ion‐selective membranes by embedding macrocycle motifs with inherent cavities. [ABSTRACT FROM AUTHOR]

Electrolyte membranes play a critical role as their properties directly influences the performance of fuel cell. A copper‐based metal organic framework (MOF) anchored polymeric blend membrane was developed for fuel cell application. Cu‐MOF serves as an excellent filler material due to its small size, high degree of crystallinity and surface area. Through XRD analysis well defined crystallite sites was evidenced and the average crystallite size measured ∼ 0.3 Å. The acidic functional group in MOF interacts with sulfonic acid (−SO3H) group in sulfonated polyetheretherketone (sPEEK) matrix which further improves proton conduction via. hydrogen bonding interaction. With the as‐prepared sPEEK as the matrix; polyimide (PI) was blended to improve its processibility and thermal stability. Cu‐MOF loaded composite membranes (X wt.% Cu‐MOF‐sPEEK/PI) were prepared and characterized. To assess the suitability of the developed membranes for proton exchange membrane fuel cell (PEMFC) applications, ion exchange capacity (IEC), water uptake and proton conductivity was measured. 3 wt.% Cu‐MOF‐2‐sPEEK/PI membrane displayed an IEC value of 2.35 meq g−1 with a water uptake of 38.18 % and proton conductivity of 0.0711 S cm−1. Overall, the experimental results of the prepared membranes revealed that they act as an efficient proton exchange membrane (PEM) for PEMFCs. [ABSTRACT FROM AUTHOR]

It is important but still challenging to develop high-performance proton exchange membranes (PEMs) which should meet the following requirements: consecutive proton-conducting channels, efficient proton transfer, and excellent stability. In this study, polyvinyl alcohol (PVA) composite membranes were constructed by loading post synthetically phytic acid (PA) encapsulated Zn-MOF, denoted as PVA@PA@Zn-MOF-X (X = 0, 2, 4, 6. wt%). The novel Zn-MOF with high thermal and pH stability has been synthesized from the zinc salt and dual ligands (H 2 NDI: 2,7-bis(3,5-dimethyl) dipyrazol-1,4,5,8-naphthalene-tetracarboxydiimide; HBTA: 1 H-benzotriazole) which can be employed to host PA as proton carriers. Composite membranes were evaluated by microstructure, thermal stability, mechanical property, dimensional stability, proton conductivity, and so forth. It is found that the codoping of PA encapsulated Zn-MOF with suitable content is more stability of the composite membranes. Furthermore, PVA@PA@Zn-MOF-4 shows the highest proton conductivity of 1.85 × 10-2 S cm-1 at 80 oC and 90% RH with relatively lower value for ion exchange capacity (0.58 mmol g-1) among the composite membranes. This phenomenon is attributed to the consecutive hydrogen bonding networks which are composed of the carbonyl oxygen sites within Zn-MOF, phosphate groups of PA, and hydroxyl groups of PVA, enhancing the efficiency of proton transport. This is a referable strategy for designing and constructing the high-performance PEMs for fuel cells. [Display omitted] [ABSTRACT FROM AUTHOR]

Membranes with high ion selectivity and conductivity are critical for the wide application of electrochemical energy conversion and storage devices. Herein, functional molecular cross‐linked two‐dimensional zeolite nanosheets (ZN) with ‐NH2 and ‐SO3H groups are prepared and incorporated into sulfonated poly (ether ether ketone) (SPEEK) polymer matrix. These embedded nanosheets act as strong barrier to vanadium ions, while their internal pores provide transport channels for protons. In addition, the side functional groups grafted on ZN not only effectively enhance the surface affinity, but also bind and arrange the sulfonic acid groups of the polymer matrix to construct a continuous fast proton transfer pathway along the interface between SPEEK and ZN. Consequently, the hybrid membranes exhibit synchronously enhanced conductive‐ion selectivity and impressive performance with coulombic efficiency (CE) of ~99.0% and energy efficiency (EE) of ~85.0% at 120 mA cm−2, which is much higher than these of pure SPEEK (CE: ~97.8%, EE: ~78.4%) and Nafion 212 membranes (CE: ~96.3%, EE: ~80.1%). This functional‐designed hybrid approach provides a general strategy to develop high‐performance proton conductive membranes for energy‐related applications. [ABSTRACT FROM AUTHOR]

Proton conducting ceramic fuel cells (PCFCs) have been attracting much more attentions due to is affordable ionic conductivity lower operating temperatures (<600 °C). CeO 2 nanosheets expose mainly to the (111) plane exhibit a super proton conductivity of 0.3 S cm−1 and a maximum power density of 948 mWcm−2 at 550 °C. In these two morphologies of CeO 2 , the difference in Ce3+/Ce4+ ratios and the formation of oxygen vacancies on the surface are mainly responsible for proton transport. Theoretical calculation proves that protons can move more easily on the CeO 2 (111) facet with smaller binding energy (0.14 eV) and lower energy barrier for H–O formation (1.7 eV) than on other facets, also superior proton conduction for the nanosheet morphology over the nano-particles. This work has developed a morphological methodology for high proton surface conduction to design highly efficient ionic transport for advanced CFCs and electrochemical devices. [ABSTRACT FROM AUTHOR]

BACKGROUND: Differential protein expression of the oral microbiome is related to human diseases, including cancer. OBJECTIVE: In order to reveal the potential relationship between oral bacterial protein expression in oral squamous cell carcinoma (OSCC), we designed this study. METHODS: We obtained samples of the same patient from cancer lesion and anatomically matched normal site. Then, we used the label free quantitative technique based on liquid chromatography tandem mass spectrometry (LC-MS/MS) to analyze the bacteria in the samples of oral squamous cell carcinoma at the protein level, so as to detect the functional proteins. RESULTS: Protein diversity in the cancer samples was significantly greater than in the normal samples. We identified a substantially higher number of the taxa than those detected in previous studies, demonstrating the presence of a remarkable number of proteins in the groups. In particular, proteins involved in energy production and conversion, proton transport, hydrogen transport and hydrogen ion transmembrane transport, ATP-binding cassette (ABC) transporter, PTS system, and L-serine dehydratase were enriched significantly in the experimental group. Moreover, some proteins associated with Actinomyces and Fusobacterium were highly associated with OSCC and provided a good diagnostic outcome. CONCLUSION: The present study revealed considerable changes in the expression of bacterial proteins in OSCC and enrich our understanding in this point. [ABSTRACT FROM AUTHOR]

Protonic ceramic electrochemical cells provide an excellent basis for the advancement of high-temperature solid oxide devices, offering potential solutions to a range of challenges in the hydrogen energy and carbon capture fields. The facilitated ionic transport in proton-conducting electrolytes enables these cells to operate at temperatures 100 °C–500 °C lower than those of conventional solid oxide cells with known zirconia electrolytes. As a result, promising performances have been reported for various types of proton ceramic electrochemical cells. Nevertheless, these advancements have been demonstrated only at the laboratory scale, whereas their ZrO _2 -based counterparts have already been commercialized. This review presents an overview of the fundamental and applied aspects related to the fabrication of tubular protonic ceramic electrochemical cells and their subsequent characterization as hydrogen permeation membranes, hydrogen pumps, hydrogen sensors, fuel cells, electrolysis cells, and electrochemical reactors. A specific focus is placed on the technological aspects of the tube preparations derived from the original powder sources as well as the dimensional characteristics of the tubes, which serve as an indicator of scaling. Therefore, this review serves as a starting point for the development and scaling of protonic ceramic electrochemical cells, with the potential for large-scale production.

Abstract Protonic ceramic fuel cells (PCFCs) offer a convenient means for electrochemical conversion of chemical energy into electricity at intermediate temperatures with very high efficiency. Although BaCeO3- and BaZrO3-based complex oxides have been positioned as the most promising PCFC electrolytes, the design of new protonic conductors with improved properties is of paramount importance. Within the present work, we studied transport properties of scandium-doped barium stannate (Sc-doped BaSnO3). Our analysis included the fabrication of porous and dense BaSn1−x Sc x O3−δ ceramic materials (0 ⩽ x ⩽ 0.37), as well as a comprehensive analysis of their total, ionic, and electronic conductivities across all the experimental conditions realized under the PCFC operation: both air and hydrogen atmospheres with various water vapor partial pressures (p(H2O)), and a temperature range of 500–900 °C. This work reports on electrolyte domain boundaries of the undoped and doped BaSnO3 for the first time, revealing that pure BaSnO3 exhibits mixed ionic-electronic conduction behavior under both oxidizing and reducing conditions, while the Sc-doping results in the gradual improvement of ionic (including protonic) conductivity, extending the electrolyte domain boundaries towards reduced atmospheres. This latter property makes the heavily-doped BaSnO3 representatives attractive for PCFC applications.

Proton relay between interfacial water molecules allows rapid two-dimensional diffusion. An energy barrier, Δ G r ‡ , opposes proton-surface-to-bulk release. The Δ G r ‡ -regulating mechanism thus far has remained unknown. Here, we explored the effect interfacial charges have on Δ G r ‡ 's enthalpic and entropic constituents, Δ G H ‡ and Δ G S ‡ , respectively. A light flash illuminating a micrometer-sized membrane patch of a free-standing planar lipid bilayer released protons from an adsorbed hydrophobic caged compound. A lipid-anchored pH-sensitive dye reported protons' arrival at a distant membrane patch. Introducing net-negative charges to the bilayer doubled Δ G H ‡ , while positive net charges decreased Δ G H ‡ . The accompanying variations in Δ G S ‡ compensated for the Δ G H ‡ modifications so that Δ G r ‡ was nearly constant. The increase in the entropic component of the barrier is most likely due to the lower number and strength of hydrogen bonds known to be formed by positively charged residues as compared to negatively charged moieties. The resulting high Δ G r ‡ ensured interfacial proton diffusion for all measured membranes. The observation indicates that the variation in membrane surface charge alone is a poor regulator of proton traffic along the membrane surface. [ABSTRACT FROM AUTHOR]

Covalent organic framework nanosheets (COF‐NSs) are emerging building blocks for functional materials, and their scalable fabrication is highly desirable. Current synthetic methods suffer from low volume yields resulting from confined on‐surface/at‐interface growth space and complex multiple‐phase synthesis systems. Herein, we report the synthesis of charged COF‐NSs in open space using a single‐phase organic solution system, achieving magnitudes higher volume yields of up to 18.7 mg mL−1. Charge‐induced electrostatic repulsion forces enable in‐plane anisotropic secondary growth from initial discrete and disordered polymers into large and crystalline COF‐NSs. The charged COF‐NS colloidal suspensions are cast into thin and compact proton exchange membranes (PEMs) with lamellar morphology and oriented crystallinity, displaying outstanding proton conductivity, negligible dimensional swelling, and good H2/O2 fuel cell performance. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is pivotal in sustainable fuel production. Neutral‐pH OER reduces operational risks and enables direct coupling to electrochemical CO2 reduction, but typically is hampered by low current densities. Here, the rate limitations in neutral‐pH OER are clarified. Using cobalt‐based catalyst films and phosphate ions as essential electrolyte bases, current–potential curves are recorded and simulated. Operando X‐ray spectroscopy shows the potential‐dependent structural changes independent of the electrolyte phosphate concentration. Operando Raman spectroscopy uncovers electrolyte acidification at a micrometer distance from the catalyst surface, limiting the Tafel slope regime to low current densities. The electrolyte proton transport is facilitated by diffusion of either phosphate ions (base pathway) or H3O+ ions (water pathway). The water pathway is not associated with an absolute current limit but is energetically inefficient due to the Tafel‐slope increase by 60 mV dec−1, shown by an uncomplicated mathematical model. The base pathway is a specific requirement in neutral‐pH OER and can support high current densities, but only with accelerated buffer‐base diffusion. Catalyst internal phosphate diffusion or other internal transport mechanisms do not limit the current densities. A proof‐of‐principle experiment shows that current densities exceeding 1 A cm−2 can also be achieved in neutral‐pH OER. [ABSTRACT FROM AUTHOR]