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The electrochemical nitrogen reduction reaction (e‐NRR) presents a promising approach for environmentally friendly ammonia synthesis. However, the efficiency of ammonia synthesis can be hindered by competitive hydrogen evolution reactions (HER). Therefore, the development of a catalyst capable of suppressing HER is essential. In this study, a synergistic hybrid catalyst Sr(Ti0.6Fe0.4)0.8B0.2O3‐δ [S(TF)B0.2], composed of Sr3B2O6 (SB) and SryTi0.6Fe0.4O3‐δ (SyTF, y<1) is synthesized and used as an electrocatalyst for electrochemical ammonia synthesis via protonic ceramic electrolysis cells, in which SB is utilized as a proton acceptor, thereby inhibiting HER and promoting proton‐coupled electron transfer (PCET) for the ammonia synthesis. The formation of SB results in a deficiency of A‐site cations in SyTF, leading to an increased number of oxygen vacancies in S(TF)B0.2. DFT calculation indicates that oxygen vacancies facilitate ammonia generation and desorption, adhering to the enzymatic pathway for NH3 synthesis. Additionally, the grain boundary (GB) between SyTF and SB introduces further defects, which contribute to the enhancement of the eNRR. Research indicates that utilizing S(TF)B0.2 as a catalyst enhances both the ammonia synthesis rate and Faradaic efficiency. This study presents a straightforward and efficient approach for the fabrication of eNRR catalysts. [ABSTRACT FROM AUTHOR]

Large‐scale hydrogen production through water splitting represents an optimal approach for storing sustainable but intermittent energy sources. However, water oxidation, a complex and sluggish reaction, poses a significant bottleneck for water splitting efficiency. The impact of outer chemical environments on the reaction kinetics of water oxidation catalytic centers remains unexplored. Herein, chemical environment impacts were integrated by featuring methylpyridinium cation group (Py+) around the classic Ru(bpy)(tpy) (bpy=2,2'‐bipyridine, tpy=2,2′ : 6′,2′′‐terpyridine) water oxidation catalyst on the electrode surface via electrochemical co‐polymerization. The presence of Py+ groups could significantly enhance the turnover frequencies of Ru(bpy)(tpy), surpassing the performance of typical proton acceptors such as pyridine and benzoic acid anchored around the catalyst. Mechanistic investigations reveal that the flexible internal proton acceptor anions induced by Py+ around Ru(bpy)(tpy) are more effective than conventionally anchored proton acceptors, which promoted the rate‐determining proton transfer process and enhanced the rate of water nucleophilic attack during O−O bond formation. This study may provide a novel perspective on achieving efficient water oxidation systems by integrating cations into the outer chemical environments of catalytic centers. [ABSTRACT FROM AUTHOR]

Industrial water splitting has long been suppressed by the sluggish kinetics of the oxygen evolution reaction (OER), which requires a catalyst to be efficient. Herein, we propose a molecular-level proton acceptor strategy to produce an efficient OER catalyst that can boost industrial-scale water splitting. Molecular-level phosphate (-PO4) group is introduced to modify the surface of PrBa0.5Ca0.5Co2O5+δ (PBCC). The achieved catalyst (PO4-PBCC) exhibits significantly enhanced catalytic performance in alkaline media. Based on the X-ray absorption spectroscopy results and density functional theory (DFT) calculations, the PO4 on the surface, which is regarded as the Lewis base, is the key factor to overcome the kinetic limitation of the proton transfer process during the OER. The use of the catalyst in a membrane electrode assembly (MEA) is further evaluated for industrial-scale water splitting, and it only needs a low voltage of 1.66 V to achieve a large current density of 1 A cm−2. This work provides a new molecular-level strategy to develop highly efficient OER electrocatalysts for industrial applications.

Although platinum is widely recognized as a benchmark catalyst for realizing highly efficient hydrogen evolution reactions, its practical application is hindered by the scarcity and high cost of Pt. In this regard, metal-free organic catalysts are considered vital alternatives for producing H 2 in green energy applications. In this study, we prepare binder-free electrocatalysts by combining salmon DNA with activated carbon (AC) (cacao pods) for H 2 production. The AC-DNA (0.025 M DNA) sample requires an overpotential (η) of 106 mV to generate a current density of 10 mA cm−2, with a Tafel slope of 96 mV dec−1, in 0.5 M H 2 SO 4. The phosphate-mediated proton acceptance of DNA facilitates the hydrogen evolution reaction (HER) in the presence of AC, resulting in excellent durability over 40 h at 10 mA cm−2 (η 10 = 106 mV) and 100 mA cm−2 (η 100 = 271 mV). In addition, the electrocatalyst exhibits a faradaic efficiency of 96.9%. The proton acceptance facilitated by the phosphate group in DNA achieves outstanding performance with a turnover frequency of 2.76 s−1 and an exchange current density of 2.08 × 10−3 A cm−2. Theoretical calculations support the in-depth H 2 evolution mechanism at the DNA-anchored AC samples via proton capturing of phosphate groups during water splitting. [Display omitted] • The negative charge (PO 4 3−) of the DNA could boost proton adsorption. • Probe sonication fragments the DNA to provide more active sites. • The AC-DNA generated 10 mA cm−2 of current density at 106 mV. • Electron transfer at the dsDNA was established. • The DFT supports the phosphate-mediated proton adsorption boosted HER. [ABSTRACT FROM AUTHOR]

Retinal-containing light-sensitive proteins – rhodopsins – are found in many microorganisms. Interest in them is largely explained by their role in light energy storage and photoregulation in microorganisms, as well as the prospects for their use in optogenetics to control neuronal activity, including treatment of various diseases. One of the representatives of microbial rhodopsins is ESR, the retinal protein of Exiguobacterium sibiricum. What distinguishes ESR from homologous proteins is the presence of a lysine residue (Lys96) as a proton donor for the Schiff base. This feature, along with the hydrogen bond of the proton acceptor Asp85 with the His57 residue, determines functional characteristics of ESR as a proton pump. This review examines the results of ESR studies conducted using various methods, including direct electrometry. Comparison of the obtained data with the results of structural studies and with other retinal proteins allows us to draw conclusions about the mechanisms of transport of hydrogen ions in ESR and similar retinal proteins. [ABSTRACT FROM AUTHOR]

Metal oxyhydroxide (MOOH) through irreversible reconstructed fabrication from transition metal compounds are highly efficient oxygen evolution reaction (OER) electrocatalysts but face limits from adsorption energy scaling relationship and sluggish deprotonation kinetics. Herein, we present Fe-doped nickel hydrogen cyanamide (Ni 0.8 Fe 0.2 -HC), which is rapidly surface reconstructed into Ni 0.8 Fe 0.2 (OOH)-HC after OER. In-situ Raman spectroscopy and density functional theory (DFT) calculations, revealed that under OER conditions, -HNCN- converts into -NCN- ligand incorporating its abundant and uniform distribution across the active sites. DFT calculations further indicate that Fe predominantly acts as the active site, with -NCN- ligands contribute to the OER by facilitating the deprotonation of *OH in the rate-determining step (RDS), acting effectively as proton acceptor. The ensemble effect between Fe and -NCN- ligand forms the foundation of the exceptional electrocatalytic performance of Ni 0.8 Fe 0.2 (OOH)-HC (190 mV at 20 mA·cm−2). This discovery offers insights for designing innovative MOOH pre-catalysts to enhance OER efficiency. [Display omitted] • Pre-catalyst Ni0.8Fe0.2-HC is prepared by a one-step method. • Ni0.8Fe0.2(OOH)-HC with proton acceptor is in-situ produce by rapid reconstruction. • In-situ generation of -NCN- makes it uniformly distributed across the active sites. • Ni0.8Fe0.2(OOH)-HC exhibit excellent OER performance (190 mV at 20 mA∙cm-2). [ABSTRACT FROM AUTHOR]

Abstract: The high performance proton transfer in polymer electrolyte membranes (PEMs) is known to be achieved through cooperating of proton donors and acceptors. In order to obtain the effective and efficient proton transfer, the present work proposes a membrane with proton donors and proton acceptors in layer‐by‐layer (LbL) structure. By applying sulfonated poly (ether ether ketone) (SPEEK) as the substrate membrane and soaking alternatively with the proton donor polymer, i.e. poly(acrylic acid) (PAA), and the proton acceptor heterocycles, i.e. benzimidazoles (BI), the LbL SPEEK/BI/PAA membranes can be achieved. The systematic variation based on the branching benzimidazole groups suggest that the LbL SPEEK/BI/PAA membrane obtained shows an increase in proton conductivity compared to the neat SPEEK, especially in the case of the membrane with trifunctional benzimidazole (B4) is as high as 1–2.5 orders of magnitude over the temperature range of 30–170 °C. The present work points out the simple surface modification of the proton conductive membrane by layer‐by‐layer approach as a practical and simple way to enhance the performance of polymer electrolyte membrane. [ABSTRACT FROM AUTHOR]

Systematic arrangement of the proton donor and acceptor as a layer-by-layer (LbL) structure is one of the simplest surface modification methods to improve the proton conductivity of a proton exchange membrane. In general, LbL assembly occurs via physical or chemical interaction between each deposited layer. Here, the stabilization of the proton donor and acceptor polymers by cross-linking those two layers together was applied as a concept. The challenge was the molecular design of the proton donor and accepter polymer species to each have compatible cross-linkable functional groups as well as proton transfer species in the molecules. Poly(acrylic acid) decorated with different amounts of thiol groups (PAA-M) was synthesized, while benzimidazole decorated branching polyethyleneimine was functionalized with maleimide groups (BIm-PEI-MI). The cross-linkable proton donor and acceptor were alternately LbL deposited on a sulfonated poly(ether ether ketone) (SPEEK) surface. The LbL membrane with an optimum crosslink level showed a proton conductivity of up to 2 orders of magnitude higher than that of the pure SPEEK membrane even at a temperature as high as 170 °C. [ABSTRACT FROM AUTHOR]

Heterocyclic compounds are known as proton transfer species for anhydrous polymer electrolyte membrane (PEM), for which efficient proton conductivity at high operating temperature has yet to be found. The present work proposes an approach to enhance the proton transfer of the membrane by combining the concept of proton donor and acceptor with an ordered structure, i.e. layer-by-layer (LbL). By simply applying poly(acrylic acid) (PAA) as a polymeric proton donor and benzimidazole (BIm) conjugated on branching poly(ethyleneimine) as a polymeric proton acceptor and alternately coating the sulfonated poly(ether ether ketone) (SPEEK), a LbL membrane can be obtained. The proton transfer can be fine-tuned by the number of bilayers, and at that time, the 20-bilayered SPEEK/BIm-PEI/PAA is an optimal condition, which achieves a balance between the hydrogen bond and chain mobility under LbL packing that allows a 1.5 higher order of magnitude conductivity than an as-prepared SPEEK membrane even at a high operating temperature range (90–170 °C). The present work, for the first time, shows how a simple LbL technique is practical for constructing high-ordered structure of proton donor and acceptor species on the membrane surface for the efficient proton transfer in a PEM. [ABSTRACT FROM AUTHOR]

This review covers the properties of a retinal protein (ESR) from the psychrotrophic bacterium Exiguobacterium sibiricum that functions as a light-driven proton pump. The presence of a lysine residue at the position corresponding to intramolecular proton donor for the Schiff base represents a unique structural feature of ESR. We have shown that Lys96 successfully facilitates delivery of protons from the cytoplasmic surface to the Schiff base, thus acting as a proton donor in ESR. Since proton uptake during the photocycle precedes Schiff base reprotonation, we conclude that this residue is initially in the uncharged state and acquires a proton for a short time after Schiff base deprotonation and M intermediate formation. Involvement of Lys as a proton donor distinguishes ESR from the related retinal proteins - bacteriorhodopsin (BR), proteorhodopsin (PR), and xanthorhodopsin (XR), in which the donor function is performed by residues with a carboxyl side chain. Like other eubacterial proton pumps (PR and XR), ESR contains a histidine residue interacting with the proton acceptor Asp85. In contrast to PR, this interaction leads to shift of the acceptor's p K to more acidic pH, thus providing its ability to function over a wide pH range. The presence of a strong H-bond between Asp85 and His57, the structure of the proton-conducting pathways from cytoplasmic surface to the Schiff base and to extracellular surface, and other properties of ESR were demonstrated by solving its three-dimensional structure, which revealed several differences from known structures of BR and XR. The structure of ESR, its photocycle, and proton transfer reactions are discussed in comparison with homologous retinal proteins. [ABSTRACT FROM AUTHOR]

Abstract: The supramolecular properties of cucurbit[7]uril and 1,ω-bisbenzimidazolyl derivatives have been studied by 1H NMR, fluorescence emission spectroscopy, and X-ray single crystal analysis. The distinctly fluorescent response behaviors indicated that the benzimidazole moiety here not only acts as the optical signaling unit for the pseudorotaxane system, but also behaves as a proton acceptor during the host–guest complexation. Furthermore, the fluorescent signals intensity could be adjusted by varying the alkylene spacer between the two benzimidazole moieties. [Copyright &y& Elsevier]

Abstract: We review studies of subunit III-depleted cytochrome c oxidase (CcO III (−)) that elucidate the structural basis of steady-state proton uptake from solvent into an internal proton transfer pathway. The removal of subunit III from R. sphaeroides CcO makes proton uptake into the D pathway a rate-determining step, such that measurements of the pH dependence of steady-state O2 consumption can be used to compare the rate and functional pK a of proton uptake by D pathways containing different initial proton acceptors. The removal of subunit III also promotes spontaneous suicide inactivation by CcO, greatly shortening its catalytic lifespan. Because the probability of suicide inactivation is controlled by the rate at which the D pathway delivers protons to the active site, measurements of catalytic lifespan provide a second method to compare the relative efficacy of proton uptake by engineered CcO III (−) forms. These simple experimental systems have been used to explore general questions of proton uptake by proteins, such as the functional value of an initial proton acceptor, whether an initial acceptor must be surface-exposed, which side chains will function as initial proton acceptors and whether multiple acceptors can speed proton uptake. This article is part of a Special Issue entitled: Respiratory Oxidases. [Copyright &y& Elsevier]

The silatranes basicity study results are summarized. A large amount of experimental data obtained 25-40 years ago is critically reviewed. It is shown that the reactivity and physicochemical properties of silatranes are determined by their basicity, which depends on the stereoelectronic structure. [ABSTRACT FROM AUTHOR]

Chitosanase from Paenibacillus fukuinensis D2 is an attractive enzyme, and it exhibits both chitosanase and β-1, 4 glucanase activities. In our previous study, we generated P. fukuinensis chitosanase-displaying yeast cells using a yeast cell surface-displaying system. Chitosanase-displaying yeast can be utilized as a chitosanase cluster without many time-consuming purification steps. In this study, using the system, we have investigated whether Glu302, which is supposed as a putative proton acceptor, is an essential amino acid residue for exhibiting chitosanase activity and analyzed the contribution of mutual interaction between Glu302 and Asn312 to the activity. A mutant library in which Glu302 and Asn312 were comprehensively substituted by the other amino acid residues was constructed on the yeast cell surface. From the results of chitosanase and β-1, 4 glucanase activity assays, we demonstrated that Glu302 was a proton acceptor for chitosanase activity, and Asn312 also participated in the hydrolysis of chitosan and cellulose. [ABSTRACT FROM AUTHOR]

Abstract: This is a short survey of the area of the hydrogen bonding where the noble and coinage metal gold enters its manifold of the proton acceptors. It is largely focused on the nonconventional hydrogen bonds that are formed in the complexes of the auride anion Au− with HF, (HF)2, H2O, (H2O)2, NH3, and (NH3)2, as mostly experimentally investigated to date. A thorough comparison of the experimental and computational data on these nonconventional hydrogen bonds is the main motif of the present work. [Copyright &y& Elsevier]

The formation of the complex between 4-cyanopyridine and 4-(6-acryloyloxy-hexyloxy) benzoic acid and its polymeric analog proceeds due to the proton transfer with the H-bond formation. The presence of two proton acceptor groups within one molecule provides a strong shift of the electron density along the complex molecule due to the conjugation within the proton acceptor molecule. The dielectric relaxation process in a symmetric associate experimentally observed is explained as a kinetic effect related to the formation and destruction of the associate.Transition from a monomer to a polymer proton donor leads to the formation of the characteristic 1:1 complex with SmC layered structure different from that of a polymer itself. [Copyright &y& Elsevier]