Protonation Reactions Research Articles

Electrical monitoring of single-event protonation dynamics at the solid-liquid interface and its regulation by external mechanical forces

Detecting chemical reaction dynamics at solid-liquid interfaces is important for understanding heterogeneous reactions. However, there is a lack of exploration of interface reaction dynamics from the single-molecule perspective, which can reveal the intrinsic reaction mechanism underlying ensemble experiments. Here, single-event protonation reaction dynamics at a solid-liquid interface are studied in-situ using single-molecule junctions. Molecules with amino terminal groups are used to construct single-molecule junctions. An interfacial cationic state present after protonation is discovered. Real-time electrical measurements are used to monitor the reversible reaction between protonated and deprotonated states, thereby revealing the interfacial reaction mechanism through dynamic analysis. The protonation reaction rate constant has a linear positive correlation with proton concentration, whereas the deprotonation reaction rate constant has a linear negative correlation. In addition, external mechanical forces can effectively regulate the protonation reaction process. This work provides a single-molecule perspective for exploring interface science, which will contribute to the development of heterogeneous catalysis and electrochemistry.

New thermodynamic insights into pregabalin interactions with H+, Na+, Mg2+, Ca2+, Cu2+, Zn2+: Equilibrium constants, enthalpy changes and sequestering ability

The thermodynamics of the interaction between (S)-(+)-3-aminomethyl-5-methylhexanoic acid (pregabalin) and protons was studied potentiometrically at different temperatures (288.15 ≤ T/K ≤ 310.15), ionic strengths (0.16 ≤ I/mol kg−1(H2O) ≤ 0.97, NaCl), (0.11 ≤ I/mol kg−1(H2O) ≤ 1.11, (C2H5)4NI), (0.10 ≤ I/mol kg−1(H2O) ≤ 1.03, NaClO4, only at T = 298.15 K). The protonation constants at infinite dilution and the corresponding enthalpy change values were determined, as well as their parameters for the dependence on the temperature and ionic strength. The results showed that the protonation reactions are exothermic, and that the entropic contribution is the driving force of the processes.Formation constants of pregabalin (L) with Zn2+, Cu2+, Ca2+, and Mg2+ were determined in NaCl(aq) at different ionic strength values, at 298.15 K. Different speciation models were proposed for the various metal/Pregabalin systems: ZnHL2+, ZnLOH0(aq), CuL+, CuL20(aq), CaL+, CaHL2+, and MgL+, depending on the different acid-base properties of the metals and the possible formation of sparingly soluble species. The modelling of the thermodynamic formation parameters respect to the temperature and ionic strength variation was carried out by using both the Specific Ion Interaction Theory (SIT) and an extended Debye-Hückel type equation.Being Pregabalin an emerging contaminant, it was interesting to investigate its distribution in presence of the investigated metal cations in aqueous solution simulating both biological fluid (urine) and natural water (seawater).

Facile synthesis and tunable fluorescent properties of a new D-π-A isocoumarin: Applications in encryption and OLED technology

A facile synthesis of a new D-π-A isocoumarin (ICP-NH2) with only two steps under mild conditions through O-acylation/Wittig/reduction reaction has been established. The readily accessible phosphonium salt precursor 1 and 4-nitrobenzoyl chloride 2 produced intermediate ICP-NO2 in the presence of triethylamine. Subsequently, ICP-NO2 underwent conversion to ICP-NH2 through the reduction of stannous dichloride. ICP-NH2 exhibits enhanced fluorescence overcoming the photo-induced electron transfer (PET) process in ICP-NO2. ICP-NH2 demonstrates a significant change in fluorescence from blue to green in various polar solvents, and DFT analysis confirmed that its solvatochromism is attributed to intramolecular charge transfer (ICT) effect. ICP-NH2 undergoes noticeable acidochromism based on reversible protonation and deprotonation reactions with TFA and TEA, leading to periodic changes in fluorescence from green to dark blue. This phenomenon can be utilized in designing reusable encryption technology. Additionally, ICP-NH2 can be employed in the fabrication of a cyan green OLED device.

An Atomic-scale Explanation For The High Selectivity Towards Carbon Dioxide Reduction Observed On Liquid Metal Catalysts.

The low-temperature liquid metals Ga-In and Ga-Snhave previously showcased >95% selectivity towards the electrochemical reduction of CO2to formate, occuring only when the alloys are melted, not solid.Here, density functional theory molecular dynamics and metadynamics simulations reveal that CO2does not directly adsorb to the Ga-alloy surface, but instead is reduced indirectly by reaction with an adsorbed hydrogen. The reaction barrier is vastly more favourable when this process occurs at In or Sn sites (average: 0.26 eV), than when it occurs on Ga (average: 0.47 eV). However, there is no difference in barrier between solid and liquid surfaces. Instead, we find that Hadsis mobile only on the liquid surface, travelling due to the motion of the liquid beneath. This process drives Hadsto In/Sn sites, allowing low-barrier CO2reduction to occur only on the liquid. Therefore, the dynamic motion of liquid metal catalysts can underpin their unique reactivity. The result has far reaching implications for any protonation reaction conducted with a liquid metal catalyst.

Controllable In situ Polymerization of 1,3‐Dioxolane via Sustained‐Release Effect for Solid‐State Lithium Metal Batteries

AbstractIn situ formed poly(1,3‐dioxolane) (PDOL) electrolytes are of great interest due to the facile process and the improved interface contact. However, the practical application of in situ PDOL electrolytes is still plagued by fast solidification time (liquid state) and poor high‐voltage stability (solid state). Herein, the slow‐release carriers triglycidyl isocyanurate (TGIC), which play dual roles as initiator sustained‐release and network confinement, can tune DOL curing time and cathode/electrolyte interface chemistry is demonstrated. Specifically, the electronegative C≐O and epoxy groups in TGIC have an affinity with BF3, the decomposition product of lithium bis(oxalate)borate (LiDFOB), delaying BF3 protonation reaction and thus extending DOL solidification time. In addition, the epoxy groups in TGIC serve as crosslinking sites to form in situ crosslinked polymer electrolytes (TPDOL@FEC). The corresponding network structure suppresses the contact reaction between high‐fluidity organic components and cathodes, generating a uniform and thin cathode electrolyte interface layer. As a result, the TPDOL@FEC precursor solution can remain its liquid state even after resting 24 h at room temperature. The assembled LiNi0.6Co0.2Mn0.2O2||TPDOL@FEC||Li cells display an impressive capacity retention of 91.5% after 100 cycles at 4.4 V (0.5 C). This study is expected to be a leap in the pursuit of practically feasible in situ formed PDOL electrolytes.

Acid-Mediated Modulation of the Conductance of Diazapentalene Molecular Junctions.

We report an acid-mediated regulation of single-molecule junction conductance achieved using an electron-deficient unit, diazapentalene, functionalized with thiophene extending units and thiomethyl aurophilic terminal groups. This diazapentalene derivative exhibits a protonation reaction in the presence of trifluoroacetic acid, as characterized by UV-vis absorption spectroscopy, and the protonated species shows a voltage-dependent single-molecule conductance, which is not observed for the pristine molecules. Specifically, under a high bias voltage of 850 mV, we observe a conductance value for the protonated molecule larger than that for the deprotonated one by a factor of 4. Density functional theory-based transport calculations show a slight broadening of the HOMO and LUMO frontier orbitals, as well as a reduced HOMO-LUMO gap when the molecule becomes protonated; this implies an increased conductance under protonation that is consistent with the experimental conductance data. Our work demonstrates a new molecular design for versatile control of molecular conductance through the use of acid in the solvent environment.

Investigation of “high-energy” metastable state of the oxidized (OH) bovine cytochrome c oxidase: proton uptake and reaction with H2O2

Investigation of “high-energy” metastable state of the oxidized (OH) bovine cytochrome c oxidase: proton uptake and reaction with H2O2

Ultralow Power, Cleft Size-Adjustable and pH-Sensitive Hyaluronic Acid (HA) Biodevices for Acid-Sensing Ion Channels Emulation.

The burgeoning implantable biodevices have unlocked new frontiers in healthcare, promising personalized monitoring strategies tailored to specific needs. Herein, hyaluronic acid (HA) is harnessed to create fully biocompatible, acidity-sensitivity and cleft-adjustable neuromorphic devices. These HA-biodevices exhibit remarkable sensitivity to pH variations, effectively mimicking biological acid-sensing ion channels (ASICs) through protonation reactions between electronegative atoms and hydrogen ions, even at ultralow driving voltage (5mV). They can monitor joint cartilage acidity by tracking changes in proton concentration and successfully diagnose the onset of arthritis. Furthermore, by adjusting the synaptic device's cleft distance, which determines responsiveness, power efficiency and plasticity, HA-based neuromorphic devices can be tailored to meet the unique demands of various implantation sites, providing both high-sensitivity and low-heat dissipation, thus broadening their application scopes. Moreover, the HA-biodevices maintain stable performance across various bending degrees, up to a curvature radius of 7.5mm, with flexibility and deformation resilience enabling installation on joints of varying curvatures. The combination of all-biocompatibility, high sensitivity, low heat dissipation, ultralow low power (2 pW), and extraordinary deformation tolerance paves the way for the development of versatile, multipurpose medical monitoring devices with immense potential in the field of healthcare.

The Effect of the Tetraalkylammonium Cation in the Electrochemical CO2 Reduction Reaction on Copper Electrode.

Aprotic organic solvents such as acetonitrile offer a potential solution to promote electrochemical CO2 reduction over the competing hydrogen evolution reaction. Tetraalkylammonium cations (TAA+) are widely used as supporting electrolytes in organic media due to their high solubility and conductivity. The alkyl chain length of TAA+ cations is known to influence electron transfer processes in electrochemical systems by the adsorption of TAA+, causing modifications of the double layer. In this work, we elucidate the influence of the cation chain length on the mechanism and selectivity of the CO2RR reaction under controlled dry and wet acetonitrile conditions on copper cathodes. We find that the hydrophobic hydration character of the cation, which can be tuned by the chain length, has an effect on product distribution, altering the reaction pathway. Under dry conditions, smaller cations (TEA+) preferentially promote oxalate production via dimerization of the CO2 ·- intermediate, whereas formate is favored in the presence of water via protonation reaction. Larger cations (TBA+ > TPA+ > TEA+) favor the generation of CO regardless of water content. In situ FTIR analysis showed that TBA+ cations are able to stabilize adsorbed CO more effectively than TEA+, explaining why larger cations generate a higher proportion of CO. Our findings also suggest that higher cation concentrations suppress hydrogen evolution, particularly with larger cations, highlighting the role of cation chain length size and hydrophobic hydration shell.

Mechanisms of Ni Dissolution from Ni-Rich Cathode in Li-Ion Batteries

Nickel-rich cathodes are the most promising candidates for realizing high-energy-density Li-ion batteries because of the high theoretical capacity. However, their structural instability detrimentally affects the battery performance during cell cycling, which restricts its large-scale commercial application. One impediment to their commercialization is the dissolution of transition metal ions, which can diffuse to the anode, corrupt the solid electrolyte interphase (SEI) films protecting the anode, and accelerate battery capacity fading. Here, we use ab initio molecular dynamics (AIMD) simulations to investigate the mechanism of Ni dissolution from the LiNiO2 cathode surfaces. Our calculations identified that the proton-transfer reactions between electrolytes and cathode surfaces cause the reduction of surface Ni atoms from Ni3+ to Ni2+, which weakened the Ni-O bonding. As the LiNiO2 cathode surface gets delithiated, more surface protonation reactions were observed, and the reduced Ni atoms were found to be dissolved from the cathode surfaces in the form of NiOOH, which is the fundamental origin of phase transition of LiNiO2 cathode from a layered to electrochemically inactive spinel-like structure, accompanied by H2O elimination and O2 evolution. Besides, we also studied the impact of various factors on Ni dissolution rates such as the presence of fluorine attachment and the coordination of Ni atoms and electrolyte species. These findings help inform future design of protective coatings, electrolytes, additives, and interfaces for Ni-rich cathode.

Activation analysis of RFT-30 cyclotron target assembly

This work evaluated the validity of computer simulation codes by comparing the results of an inventory calculation for a89Zr target assembly with measured data obtained using a high-purity germanium detector. For the inventory calculation, the MCNP6 and FISAPCT-Ⅱ codes were used, and for the measurement, efficiency derived from the efficiency transfer method was used. The MCNP6's ENDF/B-Ⅶ library (TENDL-2017 library for 89Y) and the CEM03.03 physics model were employed to simulate proton reactions, while the ENDF/B-Ⅶ library alone was utilized for neutron reactions. To verify the efficiency obtained by the efficiency transfer method, the calculated activity of the reference sources was compared with the measured activity and confirmed to be within 11%. For the target assembly, the average calculated-to-measured activity (C/M) ratio was determined to be 0.7–2.0 (physics model) and 0.7–1.5 (data library with TENDL), thus confirming the validity of the computer simulation codes. The above results suggest that the methods presented in this study could be used to establish decommissioning plans for the cyclotron facility, including plans for waste disposal of cyclotron components such as target assemblies.

Reconstruction of zinc-metal battery solvation structures operating from −50 ~ +100 °C

Serious solvation effect of zinc ions has been considered as the cause of the severe side reactions (hydrogen evolution, passivation, dendrites, and etc.) of aqueous zinc metal batteries. Even though the regulation of cationic solvation structure has been widely studied, effects of the anionic solvation structures on the zinc metal were rarely examined. Herein, co-reconstruction of anionic and cationic solvation structures was realized through constructing a new multi-component electrolyte (Zn(BF4)2-glycerol-boric acid-chitosan-polyacrylamide, simplified as ZGBCP), which incorporates double crosslinking network via the esterification, protonation and polymerization reactions, thereby combining multiple advantages of ‘liquid-like’ high conductivity, ‘gel-like’ robust interface, and ‘solid-like’ high Zn2+ transfer number. Based on the ZGBCP electrolyte, the Zn anodes achieve record-low polarization and stable cycling. Furthermore, the ZGBCP electrolyte renders the AZMBs ultrawide working temperature (−50 °C ~ +100 °C) and ultralong cycle life (30000 cycles), which further validates the feasibility of the dual solvation structure strategy and provides a innovative perspective for the development of high-performance AZMBs.

Bioinspired Diiron Complex with Proton Shuttling and Redox-Active Ligand for Electrocatalytic Hydrogen Evolution.

A μ-oxo diiron complex, featuring the pyridine-2,6-dicarboxamide-based thiazoline-derived redox-active ligand, H2L (H2L = N2,N6-bis(4,5-dihydrothiazol-2-yl)pyridine-2,6-dicarboxamide), was synthesized and thoroughly characterized. [FeIII-(μ-O)-FeIII] showed electrocatalytic hydrogen evolution reaction activity in the presence of different organic acids of varying pKa values in dimethylformamide. Through electrochemical analysis, we found that [FeIII-(μ-O)-FeIII] is a precatalyst that undergoes concerted two-electron reduction to generate an active catalyst. Fourier transform infrared spectrum of reduced species and density functional theory (DFT) investigation indicate that the active catalyst contains a bridged hydroxo unit which serves as a local proton source for the Fe(III) hydride intermediate to release H2. We propose that in this active catalyst, the thiazolinium moiety acts as a proton-transferring group. Additionally, under sufficiently strong acidic conditions, bridged oxygen gets protonated before two-electron reduction. In the presence of exogenous acids of varying strengths, it displays electro-assisted catalytic response at a distinct applied potential. Stepwise electron-transfer and protonation reactions on the metal center and the ligand were studied through DFT to understand the thermodynamically favorable pathways. An ECEC or EECC mechanism is proposed depending on the acid strength and applied potential.

Realization of Long-Life Proton Battery by Layer Intercalatable Electrolyte.

Proton batteries have attracted increasing interests because of their potential for grid-scale energy storage with high safety and great low-temperature performances. However, their development is significantly retarded by electrolyte design due to free water corrosion. Herein, we report a layer intercalatable electrolyte (LIE) by introducing trimethyl phosphate (TMP) into traditional acidic electrolyte. Different from conventional role in batteries, the presence of TMP intriguingly achieves co-intercalation of solvent molecules into the interlayer of anode materials, enabling a new working mechanism for proton reactions. The electrode corrosion was also strongly retarded with expanded electrochemical stability window. The half-cell therefore showed an outstanding long-term cycling stability with 91.0 % capacity retention at 5 A g-1 after 5000 cycles. Furthermore, the assembled full batteries can even deliver an ultra-long lifetime with a capacity retention of 74.9 % for 2 months running at -20 °C. This work provides new opportunities for electrolyte design of aqueous batteries.

Realization of Long‐Life Proton Battery by Layer Intercalatable Electrolyte

Proton batteries have attracted increasing interests because of their potential for grid‐scale energy storage with high safety and great low‐temperature performances. However, their development is significantly retarded by electrolyte design due to free water corrosion. Herein, we report a layer intercalatable electrolyte (LIE) by introducing trimethyl phosphate (TMP) into traditional acidic electrolyte. Different from conventional role in batteries, the presence of TMP intriguingly achieves co‐intercalation of solvent molecules into the interlayer of anode materials, enabling a new working mechanism for proton reactions. The electrode corrosion was also strongly retarded with expanded electrochemical stability window. The half‐cell therefore showed an outstanding long‐term cycling stability with 91.0% capacity retention at 5 A g−1 after 5000 cycles. Furthermore, the assembled full batteries can even deliver an ultra‐long lifetime with a capacity retention of 74.9% for 2 months running at ‐20 °C. This work provides new opportunities for electrolyte design of aqueous batteries.

Factors Governing Site and Charge Density of Dissolved Natural Organic Matter

Rising organic charge in northern freshwaters is attributed to increasing levels of dissolved natural organic matter (DNOM) and changes in water chemistry. Organic charge concentration may be determined through charge balance calculations (Org.−) or modelled (OAN−) using the Oliver and Hruška conceptual models, which are based on the density of weak acid functional sites (SD) present in DNOM. The charge density (CD) is governed by SD as well as protonation and complexation reactions on the functional groups. These models use SD as a key parameter to empirically fit the model to Org.−. Utilizing extensive water chemistry datasets, this study shows that spatial and temporal differences in SD and CD are influenced by variations in the humic-to-fulvic ratio of DNOM, organic aluminum (Al) complexation, and the mole fraction of CD to SD, which is governed by acidity. The median SD values obtained for 44 long-term monitored acid-sensitive lakes were 11.1 and 13.9 µEq/mg C for the Oliver and Hruška models, respectively. Over 34 years of monitoring, the CD increased by 70%, likely due to rising pH and declining Al complexation with DNOM. Present-day median SD values for the Oliver and Hruška models in 16 low-order streams are 13.8 and 15.8 µEq/mg C, respectively, and 10.8 and 12.5 µEq/mg C, respectively, in 10 high-order rivers.

Theoretical study of the methylprolithospermate's pKa in aqueous solution

Protonation and deprotonation reactions play an important role in the biological processes. Such processes are fully thermodynamic and occur in complex media where functional groups are surrounded by other chemicals such as molecules, ions, water, etc. In this paper, the compound of interest is the methylprolithospermate (MPL) molecule, which was recently isolated from salvia yunnanensis CH Wright. The intended functional groups for deprotonation are -OH and -COOH. These are the potential groups depicted at four sites located in MPL. Three thermodynamic cycles were required for the estimation of MPL's pKa by the means of DFT at the levels of B3LYP and PW6B95 with the dual basis set 6–311++G(d,p)//6–31+G(d). Cycle 1 is the direct pKa calculation, Cycle 2 is also the direct pKa calculation with proton hydration, and Cycle 3, the proton exchange process with hydroxyl anion hydration. In these cycles, water molecules as, reagents as well as products, were held as monomers in one hand (monomer cycle approaches), and cluster on the other hand (cluster cycle approaches). The isodesmic scheme was used as benchmark method for pKa calculation and yielded: pKa1 = 3.6 ± 0.3, pKa2 = 6.6 ± 0.2, pKa3 = 9.3 ± 0.2, and pKa4 = 14.4. The inclusion of binding energies of MPL anions in the pKa calculation has improved the results. The best cycles depend on the level of waters and the level of acidity. The more the number of waters clustered to MPL anions, the more the deviation of pKa values.

Conductive layer coupled mesoporous hard carbon enabling high rate and initial Coulombic efficiency for potassium ion battery

Hard carbon with rich mesopores is considered as one of the most promising anodes for potassium-ion batteries, resulting from its shortened ions diffusion distance, good electrolyte penetration ability, and highly released stress. However, the well-developed pore channels tend to separate graphite-domains and enlarge direct contact area between electrode/electrolyte, which easily cause discontinuous electrons transfer paths and extra electrolyte depletion, thus leading to poor rate performance and initial Coulombic efficiency (ICE). Hence, we propose polyaniline conductive layer coated hollow mesoporous carbon spheres (HMCS@PAN) tailored based on local protonation reaction strategy, which can enhance conductivity and simultaneously maintain considerable pore structure, accounting for an ultrahigh-rate performance (233.9 mAh/g at 5 A/g) and long cycling life (216.8 mAh/g at 5 A/g over 2000 cycles). Besides, PAN coating can inhibit the direct contact between inner pore channels and electrolyte and reduce the excessive depletion of active ions in the filling of pores with larger pore size, which is conducive to building an even, stable, and inorganic-rich solid electrolyte interphase (SEI) layer, resulting in an excellent ICE (70.7%). This work provides a guidance for the structure design of mesopore hard carbon to improve its rate and ICE.

Computational screening of single-atom catalysts supported on Al12N12 nanocage for nitrogen reduction reaction

The electrochemical nitrogen reduction reaction (NRR) on TM@Al12N12(TM=Sc∼Cu, Mo, Ru∼Pd) nanocages are investigated by density functional theory (DFT) study. TM@Al12N12(TM=Cr, Co, Ni, Ru, Mo, Rh) are evaluated as potential candidate using N2 adsorption (ΔG(*N2)), protonation reactions in first step (ΔG(*N2-*NNH)) and final step (ΔG(*NH2-*NH3)). Among all the screened deposition systems, the NRR performance shows an increase over the pure Al12N12 nanocage and the first hydrogenation step (*N2-*NNH) is the potential determining step. The electronic effect and charge transfer of the system are analyzed by the density of states (DOS) and natural bond orbital (NBO) charge. The electron density difference and the frontier orbitals analysis reveal that the screened deposition nanocages exhibit a significantly improved activation of N2 compared to the pure Al12N12 nanocage. Especially, the Ru@Al12N12 has excellent reactivity for NRR with the limiting potential of −0.80 V via distal pathway.

Polyaniline/Tungsten Trioxide Organic-Inorganic Hybrid Anode for Aqueous Proton Batteries.

Aqueous proton batteries have received increasing attention due to their outstanding rate performance, stability and high capacity. However, the selection of anode materials in strongly acidic electrolytes poses a challenge in achieving high-performance aqueous proton batteries. This study optimized the proton reaction kinetics of layered metal oxide WO3 by introducing interlayer structural water and coating polyaniline (PANI) on its surface to prepare organic-inorganic hybrid material (WO3 ⋅ 2H2O@PANI). We constructed an aqueous proton battery with WO3 ⋅ 2H2O@PANI anode and MnO2@GF cathode. After 1500 cycles at a current density of 10 A g-1, the capacity retention rate can still reach 80.2 %. These results can inspire the development of new aqueous proton batteries.