Grotthuss Proton Research Articles

Flux Synthesis of Robust Polyimide Covalent Organic Frameworks with High-Density Redox Sites for Efficient Proton Batteries.

Aqueous proton batteries are attracting increasing attention in the large-scale next-generation energy storage field. However, the electrode materials for proton batteries often suffer from low specific capacity and unsatisfactory cycle durability. Herein, we synthesize two highly crystalline and robust polyimide covalent organic frameworks (COFs) through a solvent-free flux synthesis approach with benzoic acid as a flux and catalyst. The as-synthesized COFs possess enriched redox-active sites for proton storage and intrinsic Grotthuss proton conduction, rendering them ideal candidates for proton electrode materials. The optimal COF electrodes achieve a high specific capacity of 180 mAh/g at 0.1 A/g, among the highest COF-based proton batteries, and exhibit an outstanding rate capability of up to 100 A/g and long-term cycling stability with capacity retention of 99% after 5000 cycles at 5 A/g. The assembled full cells deliver a specific capacity of 150 mAh/g at 0.2 A/g with a maximum energy density of 72 Wh/kg and a maximum supercapacitor-level power density of 64 kW/kg, surpassing all reported COF-based systems. This work paves a new avenue for the design of electrode materials for aqueous proton batteries with high energy density, power density, rate capability and long-term cycling stability.

An effective strategy to enhance phosphoric acid retention and proton conductivity stability: Construction of proton transfer channels with starch rather than H3PO4

To enhance the phosphoric acid (PA) retention as well as maintain high proton conductivity of phosphoric acid doped proton exchange membranes at high temperature, we successfully design a series of phosphoric acid doped biobased composite membranes by incorporation of starch and graphene oxide (GO) into poly arylene ether ketones (PAEK). Proton transfer channels should be mainly built through dense hydrogen bonds formed from massive oxygen-containing groups of starch mainchain, which is confirmed by Molecular dynamics (MD) simulation, FT-IR and XRD analysis. The dense hydrogen-bond structure could construct fast proton transfer channels with extreme low doping level (0.00484 molH3PO4). The excellent PA retention properties with almost unchanged proton conductivity at high temperature (200 °C) for 600 min indicates that PA molecules are firmly fixed into membranes. Thus, in this study, we suggest a novel strategy for stablizing proton conductivity at high temperature and improving PA retention properties of PA doped membranes, which is building dense hydrogen-bond structure with low PA doping level.Based on the results in this study and the Grotthuss proton transfer mechanism, dense hydrogen-bonds from oxygen-containing groups in polymer backbones should be more stable than hydrogen-bonds from massive H3PO4 molecules with high acid doping levels to promote proton conduction.

Synergistic energy harvesting and humidity sensing with single electrode triboelectric nanogenerator

Humidity sensors using triboelectric nanogenerators (TENGs) technology can provide continuous operation without the need for additional batteries. These sensors provide sustainable and self-powered humidity monitoring solutions, that can be utilized in various agriculture platforms and food processing industries. In this work, a sol-gel method is utilized to process the bismuth ferrite (abbreviated as BFO) materials and a simple mould pressing method to obtain freestanding Ethylene-vinyl acetate (abbreviated EVA)-BFO composites. These composites were characterized to shed light upon structural and microstructural properties. The single electrode mode operating TENG was fabricated having 2 cm × 2 cm active area at various wt.% of BFO onto EVA-based composites to compare the electrical response. The 5 wt.% BFO-EVA-based composites/FEP-based TENG generates a voltage and current of 45 V and 800 nA. Further, the TENG device was tested for long-term stability for 400 s, and charging of various capacitors having capacitance values such as 0.1 μF, 1 μF, 4.7 μF, and 10 μF along with 3 times charging/discharging cycles of 0.1 μF capacitor have been demonstrated. The humidity sensing mechanism elucidated which follows the conduction process based on the Grotthuss proton hopping mechanism. The TENG demonstrates a sensitivity of 0.53 V/RH% over the relative humidity range from 25 % to 85 %. The powering of the wristwatch confirms that fabricated TENG can be a reliable power source for future low-power electronics.

Oxygen Vacancies Boosted Hydronium Intercalation: A Paradigm Shift in Aluminum‐Based Batteries

AbstractIn aqueous aluminum‐ion batteries (AAIBs), the insertion/extraction chemistry of Al3+ often leads to poor kinetics, whereas the rapid diffusion kinetics of hydronium ions (H3O+) may offer the solution. However, the presence of considerable Al3+ in the electrolyte hinders the insertion reaction of H3O+. Herein, we report how oxygen‐deficient α‐MoO3 nanosheets unlock selective H3O+ insertion in a mild aluminum‐ion electrolyte. The abundant oxygen defects impede the insertion of Al3+ due to excessively strong adsorption, while allowing H3O+ to be inserted/diffused through the Grotthuss proton conduction mechanism. This research advances our understanding of the mechanism behind selective H3O+ insertion in mild electrolytes.

Oxygen Vacancies Boosted Hydronium Intercalation: A Paradigm Shift in Aluminum-Based Batteries.

In aqueous aluminum-ion batteries (AAIBs), the insertion/extraction chemistry of Al3+ often leads to poor kinetics, whereas the rapid diffusion kinetics of hydronium ions (H3O+) may offer the solution. However, the presence of considerable Al3+ in the electrolyte hinders the insertion reaction of H3O+. Herein, we report how oxygen-deficient α-MoO3 nanosheets unlock selective H3O+ insertion in a mild aluminum-ion electrolyte. The abundant oxygen defects impede the insertion of Al3+ due to excessively strong adsorption, while allowing H3O+ to be inserted/diffused through the Grotthuss proton conduction mechanism. This research advances our understanding of the mechanism behind selective H3O+ insertion in mild electrolytes.

Chitosan Composite Membrane with Efficient Hydroxide Ion Transport via Nano-Confined Hydrogen Bonding Network for Alkaline Zinc-Based Flow Batteries.

The development of membranes with rapid and selective ionic transport is imperative for diverse electrochemical energy conversion and storage systems, including fuel cells and flow batteries. However, the practical application of membranes is significantly hindered by their limited conductivity and stability under strong alkaline conditions. Herein, a unique composite membrane decorated with functional Cu2+ cross-linked chitosan (Cts-Cu-M) is reported and their high hydroxide ion conductivity and stability in alkaline flow batteries are demonstrated. The underlying hydroxide ions transport of the membrane through Cu2+ coordinated nano-confined channels with abundant hydrogen bonding network via Grotthuss (proton hopping) mechanism is proposed. Consequently, the Cts-Cu-M membrane achieves high hydroxide ion conductivity with an area resistance of 0.17Ωcm2 and enables an alkaline zinc-based flow battery to operate at 320mAcm-2, along with an energy efficiency of ≈80%. Furthermore, the membrane enables the battery for 200cycles of long-cycle stability at a current density of 200mAcm-2. This study offers an in-depth understanding of ion transport for the design and preparation of high-performance membranes for energy storage devices and beyond.

Transition from vehicle to Grotthuss proton transfer in a nanosized flask: cryogenic ion spectroscopy of protonated p-aminobenzoic acid solvated with D2O.

Proton transfer (PT) is one of the most ubiquitous reactions in chemistry and life science. The unique nature of PT has been rationalized not by the transport of a solvated proton (vehicle mechanism) but by the Grotthuss mechanism in which a proton is transported to the nearest proton acceptor along a hydrogen-bonded network. However, clear experimental evidence of the Grotthuss mechanism has not been reported yet. Herein we show by infrared spectroscopy that a vehicle-type PT occurs in the penta- and hexahydrated clusters of protonated p-aminobenzoic acid, while Grotthuss-type PT is observed in heptahydrated clusters, indicating a change in the PT mechanism depending on the degree of hydration. These findings emphasize the importance of the usually ignored vehicle mechanism as well as the degree of hydration. It highlights the possibility of controlling the PT mechanism by the number of water molecules in chemical and biological environments.

What triggers the coupling of proton transfer and electron transfer at the active site of nitrogenase?

In converting N2 to NH3 the enzyme nitrogenase utilises 8 electrons and 8 protons in the complete catalytic cycle. The source of the electrons is an Fe4S4 reductase protein (Fe-protein) which temporarily docks with the MoFe-protein that contains the catalytic active cofactor, FeMo-co, and an electron transfer cluster called the P cluster. The overall mechanism involves 8 repetitions of a cycle in which reduced Fe-protein docks with the MoFe-protein, one electron transfers to the P-cluster, and then to FeMo-co, followed by dissociation of the two proteins and re-reduction of the Fe-protein. Protons are supplied serially to FeMo-co by a Grotthuss proton translocation mechanism from the protein surface along a conserved chain of water molecules (a proton wire) that terminates near S atoms of the FeMo-co cluster [CFe7S9Mo(homocitrate)] where the multiple steps of the chemical conversions are effected. It is assumed that the chemical mechanisms use proton-coupled electron-transfer (PCET) and that H atoms (e- + H+) are involved in each of the hydrogenation steps. However there is neither evidence for, or mechanism proposed, for this coupling. Here I report calculations of cluster charge distribution upon electron addition, revealing that the added negative charge is on the S atoms of FeMo-co, which thereby become more basic, and able to trigger proton transfer from H3O+ waiting at the near end of the proton wire. This mechanism is supported by calculations of the dynamics of the proton transfer step, in which the barrier is reduced by ca. 3.5 kcal mol-1 and the product stabilised by ca. 7 kcal mol-1 upon electron addition. H tunneling is probable in this step. In nitrogenase it is electron transfer that triggers proton transfer.

Visualizing the Promoting Role of Interfacial Water in the Deprotonation of Formic Acid on Cu(111).

Water plays a crucial role in various heterogeneous catalytic reactions, but the atomic-scale characterization of how water participates in these chemical processes remains a significant challenge. Here we directly visualize the promoting role of interfacial water in the deprotonation of formic acid (FA) on a metal surface, using combined scanning tunneling microscopy and qPlus-based noncontact atomic force microscopy. We find the dissociation of FA when coadsorbed with water on the Cu(111) surface, resulting in the formation of hydronium and formate ions. Interestingly, most of the hydrated proton and formate ions exhibit a phase-separated behavior on Cu(111), in which Eigen and Zundel cations assemble into a monolayer hexagonal hydrogen-bonding (H-bonding) network, and bidentate formate ions are solvated with water and aggregate into one-dimensional chains or two-dimensional H-bonding networks. This phase-separated behavior is essential for preventing the proton transfer back from hydronium to formate and the reformation of FA. Density functional theory calculations reveal that the participation of water significantly reduces the deprotonation barrier of FA on Cu(111), in which water catalyzes the decomposition of FA through the Grotthuss proton transfer mechanism. In addition, the separate solvation of hydronium and bidentate formate ions is energetically preferred due to the enhanced interaction with the copper substrate. The promoting role of water in the deprotonation of FA is further confirmed by the temperature-programmed desorption experiment, which shows that the intensity of the H2 desorption peak significantly increases and the desorption of FA declines when water and FA coadsorbed on the Cu(111) surface.

Boosting H+ Storage in Aqueous Zinc Ion Batteries via Integrating Redox‐Active Sites into Hydrogen‐Bonded Organic Frameworks with Strong π‐π Stacking

AbstractIn the emerging aqueous zinc ion batteries (AZIBs), proton (H+) with the smallest molar mass and fast (de)coordination kinetics is considered as the most ideal charge carrier compared with Zn2+ counterpart, however, searching for new hosting materials for H+ storage is still at its infancy. Herein, redox‐active hydrogen‐bonded organic frameworks (HOFs) assembled from diaminotriazine moiety decorated hexaazatrinnphthalene (HOF‐HATN) are for the first time developed as the stable cathode hosting material for boosting H+ storage in AZIBs. The unique integration of hydrogen‐bonding networks and strong π‐π stacking endow it rapid Grotthuss proton conduction, stable supramolecular structure and inclined H+ storage. As a consequence, HOF‐HATN displays a high capacity (320 mAh g−1 at 0.05 A g−1) and robust cyclability of (>10000 cycles at 5 A g−1) based on three‐step cation coordination storage. These findings get insight into the proton transport and storage behavior in HOFs and provide the molecular engineering strategy for constructing well‐defined cathode hosting materials for rechargeable aqueous batteries.

Boosting H+ Storage in Aqueous Zinc Ion Batteries via Integrating Redox-Active Sites into Hydrogen-Bonded Organic Frameworks with Strong π-π Stacking.

In the emerging aqueous zinc ion batteries (AZIBs), proton (H+ ) with the smallest molar mass and fast (de)coordination kinetics is considered as the most ideal charge carrier compared with Zn2+ counterpart, however, searching for new hosting materials for H+ storage is still at its infancy. Herein, redox-active hydrogen-bonded organic frameworks (HOFs) assembled from diaminotriazine moiety decorated hexaazatrinnphthalene (HOF-HATN) are for the first time developed as the stable cathode hosting material for boosting H+ storage in AZIBs. The unique integration of hydrogen-bonding networks and strong π-π stacking endow it rapid Grotthuss proton conduction, stable supramolecular structure and inclined H+ storage. As a consequence, HOF-HATN displays a high capacity (320 mAh g-1 at 0.05 A g-1 ) and robust cyclability of (>10000 cycles at 5 A g-1 ) based on three-step cation coordination storage. These findings get insight into the proton transport and storage behavior in HOFs and provide the molecular engineering strategy for constructing well-defined cathode hosting materials for rechargeable aqueous batteries.

ELECTROCHEMICAL EVALUATION OF HUMIDITY BASED PROTON CONDUCTIVITY OF ALUMINIUM(III) TARTRATE

Aluminium(III) tartrate was synthesized by simple solution crystallization and its humidity dependent proton conductivity was evaluated using electrochemical impedance spectroscopy. The compound exhibited very low DC conductivity and AC conductivity in the as synthesized form and dried conditions. However, upon exposing to 100% relative humidity(RH) the AC conductivity of the compound increased significantly with time and is several orders greater than DC conductivity. The structural stability of the compound was analysed by FTIR and PXRD experiments. The compound has good structural stability on hydration, dehydration and rehydration. The proton conductivity of the sample decreased several orders on dehydration and it bounces back to original value on rehydration. The complex exhibited reversible proton conductivity with respect to moisture. The variation of proton conductivity with temperature implies that the compound exhibits Grotthuss type proton conductivity.

Shuttling-free redox electrolyte locks proton-conductive polyoxometalates in porous carbon for high-performance pseudocapacitors

Redox electrolytes are highly attractive to bring conventional carbon-based supercapacitors the additional pseudocapacitance; however, shuttling of redox species remains a severe issue restricting the potential applications of redox electrolytes. Here, we report a new phosphotungstic acid-containing redox electrolyte for carbon-based supercapacitors, which shows the shuttling-free feature by locking the polyoxometalate mediators in the porous carbon electrode. Impressively, the porous carbon electrode affords a remarkable specific capacitance of 885.7 F g−1 at 5 mV s−1 in the phosphotungstic acid-added electrolyte, triple that in the additive-free H2SO4 electrolyte (290.2 F g−1). Profiting from the unique Grotthuss proton conduction of phosphotungstic acid, the porous carbon electrode achieves the dramatic rate capability in our redox electrolyte (i.e., 567.7 F g−1 at 200 mV s−1). Moreover, the assembled supercapacitor device affords a specific energy of 52.3 Wh kg−1 and long-term cycling stability (93.7% over 5000 cycles). This study highlights the superiority of the polyoxometalate additive for redox electrolytes in developing advanced supercapacitors integrating high energy density, excellent rate performance, and electrochemical durability.

Gas-Phase Internal Proton-Transfer of Protonated para-Aminobenzoic Acid Catalyzed by One Methanol Molecule.

Electrospray ionization (ESI) is used to deliver analytes for mass analysis across a huge range of mass spectrometry applications. Despite its ubiquitous application and many mechanistic investigations, it remains that a fundamental understanding of ESI processes is not complete. In particular, all the factors that influence the populations of protonation isomers are elusive such that it remains a challenge to optimize experimental conditions to favor one isomer over another. The molecule para-aminobenzoic acid has emerged as an archetype for the study of protonation isomers, with both amino and carboxylic acid protonation site isomers (protomers) typically formed upon ESI, with the isomer ratio shown to be sensitive to several physical and chemical parameters. Here we report an ion-trap mass spectrometry study of the time-resolved methanol-catalyzed proton transfer between the amine and carboxylic acid moieties of para-aminobenzoic acid. The experimental and computational results presented are consistent with a bimolecular mechanism where isomerization is mediated by a single methanol rather than a multimolecular Grotthuss proton transfer process. Pseudo-first-order rate constants for protomer specific product ions are reported and confirm the depletion of the amino protomer is correlated to the growth of the carboxylic acid protomer. Under the controlled conditions of a low-pressure ion-trap mass spectrometer (2.5 mTorr, 300 K), the number of methanol molecules required to isomerize para-aminobenzoic acid is determined to be one, and the second-order rate constant for methanol-catalyzed isomerization is (1.9 ± 0.1) × 10-11 cm3 molecule-1 s-1. The para-aminobenzoic acid vehicle mechanism is explored computationally at the DSD-PBEP86-D3BJ/aug-cc-pVDZ level of theory and reveals that the transition state for proton transfer is submerged (-10 kJ mol-1) relative to the separated reactant energies. The findings from this paper show that single-solvent catalyzed intramolecular proton transfer reactions are possible and must be considered during the late stages of ESI to predict the site(s) of protonation and the ion's stability in the presence of solvent molecules.

Proton-Conductive Supramolecular Hydrogen-Bonded Organic Superstructures for High-Performance Zinc-Organic Batteries.

With fast (de)coordination kinetics, the smallest and the lightest proton stands out as the most ideal charge carrier for aqueous Zn-organic batteries (ZOBs). Hydrogen-bonding networks with rapid Grotthuss proton conduction is particularly suitable for organic cathodes, yet not reported. We report the supramolecular self-assembly of cyanuric acid and 1,3,5-triazine-2,4,6-triamine into organic superstructures through in-plane H-bonds and out-of-plane π-π interaction. The supramolecular superstructures exhibit highly stable lock-and-key H-bonding networks with an ultralow activation energy for protonation (0.09 eV vs. 0.25 eV of zincification). Then, high-kinetics H+ coordination is prior to Zn2+ into protophilic C=O sites via a two-step nine-electron reaction. The assembled ZOBs show high-rate capability (135 mAh g-1 at 150 A g-1 ), high energy density (267 Wh kg-1 cathode ) and ultra-long life (50 000 cycles at 10 A g-1 ), becoming the state-of-the-art ZOBs in comprehensive performances.

Proton‐Conductive Supramolecular Hydrogen‐Bonded Organic Superstructures for High‐Performance Zinc‐Organic Batteries

AbstractWith fast (de)coordination kinetics, the smallest and the lightest proton stands out as the most ideal charge carrier for aqueous Zn‐organic batteries (ZOBs). Hydrogen‐bonding networks with rapid Grotthuss proton conduction is particularly suitable for organic cathodes, yet not reported. We report the supramolecular self‐assembly of cyanuric acid and 1,3,5‐triazine‐2,4,6‐triamine into organic superstructures through in‐plane H‐bonds and out‐of‐plane π‐π interaction. The supramolecular superstructures exhibit highly stable lock‐and‐key H‐bonding networks with an ultralow activation energy for protonation (0.09 eV vs. 0.25 eV of zincification). Then, high‐kinetics H+coordination is prior to Zn2+into protophilic C=O sites via a two‐step nine‐electron reaction. The assembled ZOBs show high‐rate capability (135 mAh g−1at 150 A g−1), high energy density (267 Wh kg−1cathode) and ultra‐long life (50 000 cycles at 10 A g−1), becoming the state‐of‐the‐art ZOBs in comprehensive performances.

Proton Storage in Metallic H1.75MoO3 Nanobelts through the Grotthuss Mechanism.

The proton, as the cationic form of the lightest element-H, is regarded as most ideal charge carrier in "rocking chair" batteries. However, current research on proton batteries is still at its infancy, and they usually deliver low capacity and suffer from severe acidic corrosion. Herein, electrochemically activated metallic H1.75MoO3 nanobelts are developed as a stable electrode for proton storage. The electrochemically pre-intercalated protons not only bond directly with the terminal O3 site via strong O-H bonds but also interact with the oxygens within the adjacent layers through hydrogen bonding, forming a hydrogen-bonding network in H1.75MoO3 nanobelts and enabling a diffusion-free Grotthuss mechanism as a result of its ultralow activation energy of ∼0.02 eV. To the best of our knowledge, this is the first reported inorganic electrode exhibiting Grotthuss mechanism-based proton storage. Additionally, the proton intercalation into MoO3 with formation of H1.75MoO3 induces strong Jahn-Teller electron-phonon coupling, rendering a metallic state. As a consequence, the H1.75MoO3 shows an outstanding fast charging performance and maintains a capacity of 111 mAh/g at 2500 C, largely outperforming the state-of-art battery electrodes. More importantly, a symmetric proton ion full cell based on H1.75MoO3 was assembled and delivered an energy density of 14.7 Wh/kg at an ultrahigh power density of 12.7 kW/kg, which outperforms those of fast charging supercapacitors and lead-acid batteries.

Proton-assisted mixed-valence vanadium oxides cathode with long-term stability for rechargeable aqueous zinc ion batteries

In this work, we developed a rGO assisted vanadium oxide xerogel (abbreviate as VOHG) as cathode material for rechargeable aqueous zinc ion batteries (RA-ZIBs). The VOHG cathode exhibits an ultra-high specific capacity of 625 mA h g−1 at current density of 0.1 A g−1, superior reversibility and a long cycle life with a coulombic efficiency of 100.0% after 10,000 cycles. The VOHG material has mixed valent vanadium ions V4+/V5+and a layer structure with interlayer water. The interlayer water acts as soft support for the VO6 octahedron, forming a large space in the layers for H+/Zn2+ intercalation, which improves the migration rate of Zn2+ due to its charge shielding effect. Protons can move quickly through the interlayer water network by Grotthuss proton transport mechanism. The application of the unique structure of VOHG makes zinc ions battery will be a promising candidate of energy storage device with high-capacity and long cycle stability.

Antifreezing Proton Zwitterionic Hydrogel Electrolyte via Ionic Hopping and Grotthuss Transport Mechanism toward Solid Supercapacitor Working at −50 °C

Hydrogel electrolyte is widely used in solid energy storage devices because of its high ionic conductivity, environmental friendliness, and non‐leakage property. However, hydrogel electrolyte is not resistant to freezing. Here, a high proton conductive zwitterionic hydrogel electrolyte with super conductivity of 1.51 mS cm–1 at −50 °C is fabricated by random copolymerization of acrylamide and zwitterionic monomer in the presence of 1 m H2SO4 and ethylene glycol (EG). The antifreezing performance and low temperature conductivity are ascribed to hydrogen bonds and ionic bonds between the components and water molecules in the system and can be tuned by changing the monomer ratio and EG contents. The proton hopping migration on the ionic group of the polymer chains and Grotthuss proton transport mechanism are responsible for the high proton conductivity while Grotthuss transport is dominated at the glassy state of the polymer chains. The electrolyte‐assembled supercapacitor (SC) offers high specific capacitance of 93.5 F g–1 at 25 °C and 62.0 F g–1 at −50 °C with a capacitance retention of 91.1% and 81.5% after 10 000 cycles, respectively. The SC can even work at −70 °C. The electrolyte outperforms most reported antifreezing hydrogel electrolytes and has high potential in low‐temperature devices.

Anhydrous Fast Proton Transport Boosted by the Hydrogen Bond Network in a Dense Oxide-Ion Array of α-MoO3.

Developing high-power battery chemistry is an urgent task to buffer fluctuating renewable energies and achieve a sustainable and flexible power supply. Owing to the small size of the proton and its ultrahigh mobility in water via the Grotthuss mechanism, aqueous proton batteries are an attractive candidate for high-power energy storage devices. Grotthuss proton transfer is ultrafast owing to the hydrogen-bonded networks of water molecules. In this work, similar continuous hydrogen bond networks in a dense oxide-ion array of solid α-MoO3 are discovered, which facilitate the anhydrous proton transport even without structural water. The fast proton transfer and accumulation that occurs during (de)intercalation in α-MoO3 is unveiled using both experiments and first-principles calculations. Coupled with a zinc anode and a superconcentrated Zn2+ /H+ electrolyte, the proton-transport mechanism in anhydrous hydrogen-bonded networks realizes an aqueous MoO3 -Zn battery with large capacity, long life, and fast charge-discharge abilities.