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Addressing the challenges in solid oxide fuel cells (SOFCs) applications, this study develops efficient low-temperature cathode materials. The proton-conducting barium zirconate-based electrolyte BaZr 0·1 Ce 0·7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) shows excellent conductivity and stability, indicating significant potential in proton conducting SOFCs (H–SOFCs). A series of A-site defect-engineered (La 0·6 Sr 0.4) x Co 0.2 Fe 0·7 Nb 0·1 O 3-δ (LSCFN, x = 1, 0.95, 0.90) cathode materials were synthesized via the sol-gel method. The composite electrodes incorporating LSCFN and BZCYYb exhibited enhanced oxygen reduction reaction (ORR) performance. Results indicate that A-site defects significantly enhance electrocatalytic activity. At 750 °C, a single cell with a Ni-BZCYYb|BZCYYb|(LS) 0.90 CFN-BZCYYb configuration exhibited the lowest interfacial resistance (0.063 Ω cm2) and highest peak power density (0.933 W/cm2). Durability testing at 700 °C for 100 h under 0.3 A/cm2 showed excellent stability with negligible degradation, confirming the positive impact of A-site defects on ORR activity. The distribution of relaxation times (DRT) analysis provided insights into performance optimization. Thus, (La 0·6 Sr 0.4) 0.9 0 Co 0·2 Fe 0·7 Nb 0·1 O 3-δ -BZCYYb demonstrates excellent potential as an H–SOFC cathode material, advancing SOFC technology. • Synthesized (LS) x CFN (x = 1, 0.95, 0.90) cathodes with A-site defects. • Reached peak power density of 0.933 W/cm2 at 750 °C using (LS) 0.90 CFN-BZCYYb cathode. • Stable H–SOFC operation for 100 h at 700 °C, 0.3 A/cm2, with minor degradation. • A-site defects enhanced ORR kinetics, reducing interfacial resistance to 0.063 Ω cm2. • DRT analysis insights into electrochemical process optimization & cathode performance. [ABSTRACT FROM AUTHOR]

Perovskite-type proton conducting electrolytes are garnering significant attention due to its key role in protonic ceramic electrochemical cells (PCEC) and its application in hydrogen sensors (HS) used for metal melt measurements. Developing high proton conduction perovskite materials with good chemical stability is always a worldwide research focus. In this paper, Y, Yb and Gd triple-doping on B-site of BaCeO 3 -BaZrO 3 solid solution were carried out to investigate the effect of gadolinium doping on the performance of protonic conducting electrolytes. BaZr 0.1 Ce 0.7 (Y 0.5 Yb 0.5) 0.2- x Gd x O 3-δ (x = 0, 0.1, 0.15 and 0.2), which were also referred as BZCYYbGd x (x = 0, 10, 15 and 20), were synthesized by solid-state reaction at 1600 °C for 10 h. It is found that BZCYYbGd15 has the highest proton conductivity and proton transfer number among the four prepared materials. The proton mobility of BZCYYbGd15 is 4.06 × 10−6 cm2/(Vꞏs) at 800 °C, which increases with an increased temperature. Its proton transfer number is higher than 0.9 at 500 °C under the atmosphere of P H 2 O = 0.018 atm. A moderate doping of gadolinium increases the temperature threshold for proton conduction. Proton, oxygen vacancy, electron hole and total conductivity activation energies of BZCYYbGd15 under the wet atmosphere are found to be 0.74, 1.58, 1.41 and 0.92 eV, respectively. Furthermore, the chemical stability of pellets is improved after gadolinium doping. This study provides a reference value for future research on high proton conduction electrolytes. [ABSTRACT FROM AUTHOR]

A CO 2 -stable, easily sintered proton-conducting oxide electrolytes based on solid solution Ba 7 In 6 Al 2– x Zn x O 19-0.5 x with hexagonal structure has been synthesized for the first time. Within the homogeneity region (0 ≤ x ≤ 0.10), there is an increase in unit cell parameters, cell volumes and free cell volumes. The addition of Zn2+ markedly improved the sinterability of the material. The relative density of the ceramics of the doped samples reached 95 % at lower sintering temperatures than the parent phase. The electrical conductivity was studied using electrochemical impedance spectroscopy. Upon doping the oxygen-ion conductivity increased by 0.25 orders of magnitude at 800 °C. Proton transport was predominant below 500 °C for a wet atmosphere (pH 2 O = 1.92·10−2 atm). The investigated phases Ba 7 In 6 Al 2– x Zn x O 19-0.5 x are capable of hydration and incorporate up to 1.45 mol H 2 O vs 0.41 mol H 2 O for the parent phase. The studied phases exhibit chemical resistance to CO 2 under heat treatment at 600 °C. It was shown that solid solution Ba 7 In 6 Al 2– x Zn x O 19-0.5 x is a promising electrolyte material for intermediate-temperature fuel cells. [Display omitted] • The Zn-doping in solid solution Ba 7 In 6 Al 2– x Zn x O 19-0.5 x markedly improved the sinterability of the material and well-sintered ceramics were obtained with relative density 95 %. • The water uptake increased with increasing Zn-concentration. • Ba 7 In 6 Al 2– x Zn x O 19-0.5 x phases were protonic conductors at T < 500 °C in wet air. • Ba 7 In 6 Al 2– x Zn x O 19-0.5 x phases exhibited chemical resistance to pure CO 2. [ABSTRACT FROM AUTHOR]

The solid solution Ba 5 In 2– x Y x Al 2 ZrO 13 (0 ≤ х ≤0.50) with hexagonal structure (space group P 6 3 / mmc) was prepared by the solid-state reaction method. The effects of isovalent Y3+-substitution on the structure, hydration, bandgap and transport properties have been investigated. The introduction of yttrium was accompanied by lattice expansion, which led to an increase in the concentration of protons during hydration. The doping did not lead to a significant increase in oxygen-ion conductivity since there was no change in oxygen stoichiometry. At the same time, doping led to an increase in ionic transport numbers due to a decrease in hole conductivity. Proton conductivity contribution and the values of proton conductivity increase with the increase in yttrium concentration. The phases with yttrium content x > 0.2 were predominant proton conductors at the temperature below 600°С under wet air. [ABSTRACT FROM AUTHOR]

Proton-conducting solid oxide fuel cell is an emerging technology to deliver sustainable energy conversion with the benefit of fuel flexibility. A low proton conduction energy barrier in the perovskite-type electrolytes facilitates the fuel cells to operate at lower temperatures. The design of electrolytes heavily relies on a better understanding of the proton conduction mechanism in the lattice. However, the manifestation of multiple cations, vacancies, and structural distortion in the electrolyte materials raises complexities in the proton conduction mechanism. This article briefly reviews the proton conduction mechanism to explain the roles of electronegativity, dopants, and sintering aids on the hydration behavior. The impact of acceptor dopants on protonic defect formation and mobility is discussed with particular emphasis on the proton trapping effect. • Protonic defects formation and migration in proton conducting solid oxide fuel cells. • Grotthuss mechanism to transport protons in perovskites. • Dopants ionic radius, electronic structure, and compatibility with the parent lattice affect proton conduction. • Proton trapping at higher concentrations of acceptor dopants. [ABSTRACT FROM AUTHOR]

Novel chitosan (CS) composite membranes modified with ionic liquids (ILs), namely, 1-Hexyl-3- methylimidazolium tricyanomethanide ([HMIM][TCM]), Diethylmethylammonium methanesulfonate ([DEMA][OMs]), were synthesized to be used as a polymer electrolyte membrane (PEM) in for PEM fuel cells. The ionic conductivities of the prepared membrane samples were evaluated using electrochemical impedance spectroscopy (EIS). The CS is one of the attractive choices of green and sustainable membrane materials in PEMs because of its chemical tunability and cost-effectiveness. The membranes were prepared by solution casting followed by a solvent evaporating procedure. The low proton conductivity of pristine CS biopolymer was enhanced by the incorporation of ILs in the membrane framework. Tensile testing confirmed the excellent membrane mechanical integrity. A significant enhancement in the membranes' characteristics was observed upon the introduction of [DEMA][OMs] into its matrix. The experimental results showed enhanced proton conductivities of the prepared membranes along with enhanced flexibility. The proton conductivity of pristine CS membrane was increased from 8.4 × 10−4 to 1.25 × 10−2 S/cm and 1.1 × 10−2 S/cm when a 30 wt% [HMIM][TCM] and 100 wt% [DEMA][OMs] were added, respectively. Synergistic effects of amine and imidazolium-based ILs on the electrical, structural, water uptake, and thermal properties of CS-based biopolymer solid electrolyte membranes are reported for the first time in this work. The aforementioned characterization results demonstrate the potential of using these membranes in PEM fuel cells operating above the boiling point of water and at a lower cost. This work showed that there should be an optimization amount of the ILs content in the membrane to maintain its mechanical integrity. • Chitosan (CS) and ionic liquid (IL) membranes were prepared in this work. • The Pristine CS based membranes had a proton conductivity of 0.84 mS cm−1 • The conductivity of the 30 wt % [HMIM][TCM] IL/CS membrane was equal to 12.49 mS cm−1 • A conductivity of 11.05 mS cm−1 was reported for the CS membrane modified with [DEMA][OMs] IL. [ABSTRACT FROM AUTHOR]

Effect of Sc-doping on crystal structure, morphology and conductivity of SrHfO 3 was studied for the first time. SrHf 1-x Sc x O 3-δ (x = 0–0.15) was synthesized by solid state reaction and examined using Rietveld refinement of X-ray diffraction patterns, scanning electron microscopy and four-probe DC technique. It was shown that scandium incorporates into the crystal lattice of SrHfO 3 and SrHf 1-x Sc x O 3-δ crystallizes in the orthorhombic Pbnm space group. Sc-doping enhances the grain growth and sinterability, which results in increased density of ceramics. The conductivity of SrHf 1-x Sc x O 3-δ increases with increasing Sc-content, which is consistent with the common model of oxygen vacancies formation. Increase in conductivity with increasing water vapor partial pressure indicates a significant contribution of protons to charge transport. High ionic conductivity is combined with high ion transference numbers, which makes SrHf 1-x Sc x O 3-δ promising electrolytes for use in electrolysis cells producing clean hydrogen from steam and fuel cells converting chemical energy into electricity. [Display omitted] • Sc-doping enhances grain growth and improves sintering ability of SrHfO 3. • Crystal structure of SrHfO 3 was modelled using Rietveld refinement parameters. • Sc-doped SrHfO 3 demonstrates significant protonic conductivity in wet atmosphere. • The sample with x = 0.15 has the highest conductivity among SrHf 1-x Sc x O 3-δ (x = 0–0.15). [ABSTRACT FROM AUTHOR]

• Four isomorphic rare earth metal-organic frameworks with high stability have been prepared. • JXUST-43 exhibits the highest conductivity with the value of 7.38 × 10–5 S·cm-1 at 98 % RH and 55 °C. • J XUST-42 displays a significant magnetocaloric effect with -Δ S m max of 16.63 J kg-1 K-1 at 3 K with Δ H = 7 T. The presence of field-induced slow magnetic relaxation behavior with antiferromagnetic coupling is observed in JXUST-43. Four isomorphic rare earth metal-organic frameworks designated as {[(CH 3) 2 NH 2 ] 0.7 [RE 2 (BTDBA) 1.5 (lac) 0.7 (H 2 O) 2 ]·solvent} n (RE = Tb (JXUST-19), Eu (JXUST-29), Gd (JXUST-42), and Dy (JXUST-43), where JXUST denotes Jiangxi University of Science and Technology) have been synthesized derived from a benzothiadiazole tetracarboxylate ligand (4′,4'''-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis([1,1′-biphenyl]-3,5-dicarboxylic acid), H 4 BTDBA). They present chain-based three-dimensional structures with one-dimensional channels extending along the b -axis. Notably, the free [(CH 3) 2 NH 2 ]+ cations within the channels serve as proton carriers during proton conduction. All complexes demonstrate significant proton conductivity dependent on relative humidity and temperature. Among them, JXUST-43 displays the peak conductivity achieved 7. 38 × 10–5 S·cm-1. In terms of magnetic research, JXUST-42 exhibits potential as a magnetorefrigerant, reaching a maximum entropy change (-Δ S m max) of 16.63 J kg-1 K-1 at 3.5 K with Δ H = 7 T. And the presence of field-induced slow magnetic relaxation behavior with antiferromagnetic coupling is observed in JXUST-43. A series of isomorphic RE-MOFs (JXUST-19, 29, 42 and 43) are potential candidates for proton conduction and magnetic refrigeration. [Display omitted] [ABSTRACT FROM AUTHOR]

Recently, it was demonstrated that employing metal-organic frameworks (MOFs) with prominent proton conductivity (σ) as fillers with organic substrates such as chitosan (CS) or Nafion is an effective approach for preparing composite membranes (CMs) with outstanding functionalities. Inspired by this, one extremely stable Zr(IV)-MOF (namely Zr-FDC) with a nanosheet structure produced by 1,1′-ferrocene dicarboxylic acid (H 2 FDA) was successfully manufactured in this research and subsequently used as a filler to synthesize a series of CS-based CMs via casting method. The alternating current (AC) impedance determinations manifested that both Zr-FDC and the related CS-based CMs (CS/MOF-x ; x = 2, 4, 6, 8 being the mass percentage of Zr-MOF in the CM) showed ultrahigh σ values, indicating the structural advantages of the Zr-MOF. Further research verified that when the MOF doping quantity is 4 %, the CM's (CS/MOF-4) σ is the greatest, being 2.22 × 10−2 S/cm, which is boosted by nearly tenfold at 100 °C and 98 % relative humidity (RH) compared to the original MOF (3.2 × 10−3 S/cm). Furthermore, the CM exhibits superior thermal stability and tensile resistance. Finally, considering the structural features of the MOF and CS, activation energy data, and other determinations, we thoroughly theorized the proton conduction process within the MOF framework and CMs, referencing the subsequent proton exchange membrane design. Highly stabilized Zr-FDC MOF nanosheet and related CS-based composite film (CS/MOF-4) were prepared with high proton conductivities at 100 °C/98 % RH, being 3.20 × 10−3 and 2.22 × 10−2 S/cm, respectively. Their proton conduction mechanisms were highlighted. [Display omitted] • One highly stable Zr(Ⅳ)-MOF and CS-based composite membranes were prepared. • Their ultrahigh proton conductivities were explored. • The conducting mechanisms were highlighted. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs), also known as transition metal‑oxygen clusters deliver unique physical and chemical properties such as low effective surface charge density, high thermal stability, and multi-electron acceptance, making them suitable for proton conductors. In recent years, proton conductive POMs have achieved significant progress in high performance (>10−2 S/cm) comparable to conventional materials through structural regulation strategies. At the same time, the veiled conduction mechanism has been elucidated by structural analysis and characterization. In this review, the research of POMs (Keggin-type, Dawson-type, composite materials) in proton conduction is reviewed mainly from the design strategy, proton conductivity and mechanism, structure-function relationship, and application, finally with a detailed discussion of challenges and prospects. This review will provide more inspiration for exploring and applying proton-conducting POM materials. Polyoxometalates (POMs) have low effective surface charge density, high thermal stability, electron acceptance ability, and discrete mobile ion components, making them particularly suitable as proton conductors. This article reviews the recent advances in this field, including Keggin-type POMs, Dawson-type POMs, organic-graded POMs, composites, and others. The design strategy, the relationship between structure and proton conductivity, and the future development trend of POMs are discussed. [Display omitted] • We provide a detailed elaboration on proton conducting POMs. • The design strategy, proton conductivity and mechanism, structure-function relationship, and application are summarized. • The review provides the prospects and challenges of proton conducting POMs. • The review would inspire development of more advanced proton conducting materials. [ABSTRACT FROM AUTHOR]

• Ozone-induced one-step grafting to produce PVDF- g -PAMPS graft copolymer. • Series of GO-incorporated PVDF- g -PAMPS membranes are fabricated. • PAG-2 exhibited excellent proton conductivity and stability. • PAG-2 showed a peak power density of 152.9 and 37.7 mW/cm2 in PEMFC and DMFC, respectively. • PAG-2 retained 91 % of its initial OCV after an accelerated durability test. Chemically modified poly (vinylidene fluoride) (PVDF) as polyelectrolyte has generated immense interest due to its high efficiency in electrochemical energy devices. Herein, the design of a polymer electrolyte membrane (PEM) is formulated by the synergistic fusion of graphene oxide (GO) into chemically grafted PVDF with 2-acrylamido-2-methylpropane sulfonic acid (AMPS) by solution phase intercalation producing GO@PVDF- g -PAMPS composite membranes. Ozone-induced graft copolymerization technique is employed to prepare PVDF- g -PAMPS with 18.2 % (w/w) degree of grafting. Incorporation of GO into the polymeric membrane generates appropriate hydrophilic-hydrophobic phase separation and constructs well-organized sub-nano slit-like pathways that elevate the proton conduction. PAG-0 membrane without any filler shows a proton conductivity (κ) of 15.1 mS/cm at 80 °C whereas PAG-2 membrane (with 2% w/w GO loading) shows a κ of 25.9 mS/cm under similar conditions. The presence of a perfluorinated backbone furnishes excellent oxidative stability to the PEMs by retaining 95 % of total mass and 97.3 % of κ after dipping in harsh Fenton's reagent at 60 °C for 6 h. Representative PAG-2 shows a peak power density of 152.9 mW/cm2 with a maximum current density of 480.6 mA/cm2 (fuel cell operating conditions: 75 °C at 100 % RH) in hydrogen fuel cell and a peak power density of 37.7 mW/cm2 in direct methanol fuel cell. Moreover, PAG-2 retains 91 % of its initial OCV and exhibits a mere 5.2 % loss in peak power density after 50 h of the durability test. [Display omitted] [ABSTRACT FROM AUTHOR]

• A pzdc2- ligand covalently functionalized arsenotungstate was synthesized. • Four pzdc2– ligands are coordinated with w atoms of POMs skeleton. • This hybrid arsenotungstate displays decent proton conduction property. A pyrazine-2,3-dicarboxylic acid hybrid arsenotungstate K 5 Ba 5 H{Ba[AsW 11 O 37 (pzdc) 2 ] 2 }·22H 2 O (1 , H 2 pzdc = pyrazine-2,3-dicarboxylic acid) has been synthesized. This compound displayed a dimeric polyanion which consisted of two ancient official cap-shaped [AsW 11 O 37 (pzdc) 2 ]9– subunits linked together via a Ba2+ cation. The [AsW 11 O 37 (pzdc) 2 ]9– subunit is fused together by a trivacant [AsW 9 O 33 ]9– fragment and two {WO 2 (pzdc)} groups. And the [Ba(AsW 9 O 33) 2 ]16– subunit can be simplified into the ferrocene-like structure. What is particularly interesting is that one N and one O atom of the pzdc2– ligand can directly chelate with the W atom to construct the infrequent W–O–C–C–N five-membered ring. Compound 1 exhibits good proton conduction property with the conductivity of 1 can reach up to 2.37× 10–3 S cm-1 at 70 °C under 95% relative humidity. Synopsis A pzdc2− ligand covalently functionalized arsenotungstate, K 5 Ba 5 H{Ba[AsW 11 O 37 (pzdc) 2 ] 2 }·22H 2 O, consisted of two ancient official cap-shaped polyanion [AsW 11 O 37 (pzdc) 2 ]9− linked via a Ba2+ cation, which exhibits decent proton conduction property with conductivity of 2.37× 10−3 S cm−1 at 70 °C under 95% relative humidity. [Display omitted] [ABSTRACT FROM AUTHOR]

Bilayer electrolytes can enhance the performance of protonic ceramic fuel cells (PCFCs). In this work, the transport of charged defects through BaZr 0.8 Y 0.2 O 3 − δ | BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3 − δ bilayer electrolytes is modeled using a Nernst–Planck–Poisson formulation. New parameter sets were fitted to accurately represent the conductivity data and predict the i – V curve. The concentration and electrostatic potential profiles were calculated, along with the defect fluxes. The results show that the bilayer electrolyte exhibits lower hole conduction compared to the corresponding single-layer electrolytes. Additionally, a positive proton concentration gradient towards the cathode side is observed in the bilayer electrolyte, which is not present in single-layer electrolytes. The slope of the concentration profile increases as the L BZY / L tot ratio decreases, corresponding with improved cell performance. This observed increase in proton concentration towards the cathode side suggests favorable conditions for proton supply to the cathode, thereby enhancing overall cell performance. • The Nernst–Planck–Poisson model is solved for bilayer electrolytes. • Suppressed leakage current in bilayer electrolytes. • Proton concentration profile steep positive slope linked to increased PCFC performance. [ABSTRACT FROM AUTHOR]

• Three MOFs based on rare earth and transition metal ions were prepared. • Their structures were characterized by SCXRD, IR, XRD and TGA. • The highest proton conductivity is 3.38×10‒5 S cm‒1 at 338 K and 98% RH. • The entropy change (−Δ S m) of compound 1 is 7.1 J kg−1 K−1 at 7 K and 7 T. Three heterometallic metal-organic frameworks, namely, {RE 2 Co 3 L 6 (H 2 O) 6 } n (RE = Gd (1), Dy (2), Y(3)), have been hydrothermally synthesized based on rare-earth (RE) and transition metal ions and the organic ligand of 3-hydroxyisonicotinic acid (H 2 L). Single-crystal X-ray diffraction reveals that compounds 1 ‒ 3 are isomorphic and features three-dimensional (3D) porous structure. In compound 1 , the Gd3+ ion is located in the C 3 axis, and every two propeller-like {GdCo 3 } units are capped up and down to a {Gd 6 Co 6 } ring through twelve L2‒ ligands, giving rise to the formation of the cavities. Notably, three compounds display high thermal stability determined by thermogravimetric analysis (TGA), and good water stability proved by the well-matched of PXRD curves before and after soaked three samples in water for three days. AC impedance measurements exhibit the proton conductivities of compounds 1 ‒ 3 with powder samples are distinctly temperature and humidity dependent, and the values can reach 3.38×10‒5, 1.91×10‒5, and 2.23×10‒5 S cm‒1 at 98% RH and 338 K, respectively. Moreover, compounds 1 ‒ 3 display antiferromagnetic behaviours, and the magnetocaloric effect (MCE) study indicates that the entropy change (−Δ S m) of compound 1 is 7.1 J kg−1 K−1 at 7 K and 7 T. Compound 2 exhibits the slow magnetic relaxation behaviour. Three MOFs based on rare earth and transition metal ions have been prepared under hydrothermal condition and characterized by single-crystal X-ray diffraction, IR, XRD and TGA. Their proton conductivities can reach 10‒5 S cm‒1 at 338 K and 98% RH. In addition, compounds 1 and 2 displays antiferromagnetic behaviors. The entropy change (−Δ S m) of compound 1 is 7.1 J kg−1 K−1 at 7 K and 7 T. [Display omitted] [ABSTRACT FROM AUTHOR]

• Li doping induces phase self-assembly, incorporating a new hydration phase, LiFeO 2. • In-situ reconstruction of electrolyte under fuel cell atmosphere yields oxide/oxide-carbonate/hydroxide nanocomposite. • Rich interfaces bring high ionic conductivity and fuel cell performance at Low temperature. • Experimentally verified proton conduction nature in nanocomposite. • The hydration phase improves proton transport. In the development of low temperature solid oxide fuel cells (LT-SOFCs), also called ceramic fuel cells, the lack of highly conductive and the high manufacturing cost of dense electrolyte materials severely delay their wide development. In this work, we depart from the classic substitution approach to achieve sufficient ionic conduction (0.01 S cm−2 level at temperature ≥600 °C), a superionic conductive electrolyte material was obtained from a self-assembled hybrid oxide that was derived from the perovskite oxide precursor through alkali metal ion substitution. Moreover, the hybrid oxide was further in-situ reconstructed into a nanocomposite of oxide/carbonate-hydroxide under fuel cell condition. The nanocomposite possesses dominated proton conductivity as verified by the benefited hydration effect, versatile oxygen ionic blocking cell experiment, and concentration cell investigation. Specifically, an outstanding ionic conductivity of 0.185 S cm−1 and an excellent peak power density of 1012 mW cm−2 were demonstrated at 550 °C under an typical H 2 /air atmosphere. This research offers a rational design strategy to achieve low temperature, high-performance semiconductor-based functional composite electrolytes for efficient and sustainable energy conversion in SOFC technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modification of MOF nanochannels with high concentrations of sulfonic acid by introducing polymers into the nanochannels of the MIL-101 series. • The MOF composites exhibited outstanding barium ion adsorption capacity with maximum uptakes of 356.9 mg·g−1. • The MOF composites also exhibited superior proton conductivity with maximum values of 1.43 × 10−1 S·cm−1 at 85 °C and 98 % RH. Porous materials with a high concentration of sulfonic acid groups are highly desirable for applications such as radioactive Ba2+ adsorption, catalysis, and proton-conductive materials, but they are also challenging to synthesize. In this work, we introduce polymers containing sulfonic acid groups into the nanochannels of metal–organic frameworks (MOFs) through in-situ synthesis to enhance the sulfonic acid content. We use a alkene with sulfonic acid groups (2)-acrylamido-2-methylpropane sulfonic acid, AMPS) and a crosslinking agent N,N'-methylenebisacrylamide (MBAA) to synthesize two MOF composites, PAMPS@MIL-101 and PAMPS@MIL-101-SO 3 H, in the ultra-stable MIL-101 series through in-situ polymerization with free radical initiators. The two MOF composites have a high and uniform distribution of sulfonic acid groups in the MOF framework, which results in ultra-high barium ion adsorption capacity. The maximum adsorption amounts are 142.7 and 356.9 mg·g−1 for PAMPS@MIL-101 and PAMPS@MIL-101-SO 3 H, respectively, which are higher than those of most reported adsorbents. Importantly, the adsorption equilibrium can be achieved within 20 min. Moreover, both MOF composites, PAMPS@MIL-101 and PAMPS@MIL-101-SO 3 H, exhibit super proton conductivity, with values of 6.43 × 10−2 S·cm−1 and 1.43 × 10−1 S·cm−1 at 85 °C and 98 % RH, respectively. This method offers a new way of modifying MOF nanochannels with high sulfonic acid concentrations, and opens up new opportunities for developing radioactive Ba2+ adsorption materials and proton-conductive materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • NUS-9 nanosheets with well-defined sulfonic acid groups possess intrinsic proton conductivity. • DNA with plentiful linear arranged phosphate groups provide extrinsic proton-conducting sites. • Synergism of orderly intrinsic and extrinsic proton-conducting sites facilitates the proton conduction. • DNA@COF-X membranes exhibit enhanced proton conductivity in different humidity. Development of high proton-conducting membranes is the major demand in energy conversion, sensing, and catalysis. The emerging ionic covalent organic frameworks (iCOFs) with abundant and well-arranged proton-conducting groups offer new materials for efficient proton conduction. However, the poor processability of iCOFs makes it difficult to fabricate defect-free membranes. Herein, we use the interfacial reaction method to synthesize high crystalline iCOF nanosheets (NUS-9) which are then processed into defect-free membranes by vacuum-assisted assembly method. The plenty of intrinsic orderly aligned sulfonic acid groups in the iCOF skeletons endows the nanosheets with intrinsic high proton conductivity. Furthermore, the deoxyribonucleic acid molecules (DNA) with sequential linear arranged phosphate groups are intercalated into the iCOF membrane. The synergetic effect of orderly intrinsic and extrinsic proton-conducting sites gives the resulting DNA@iCOF membranes high proton conductivity of up to 494.7 mS cm−1 (98% RH, 80 °C), which is among the highest values of the state-of-the-art COF-based proton conductors. Besides, it also retains high conductivity over a wide range of RH (40–100%) and temperature (30−80 °C). [ABSTRACT FROM AUTHOR]

Ceramics electrets of hydroxyapatite (HAp) have been developed for both power generators and artificial bones. However, the formation mechanisms of the HAp electrets have not yet been completely understood. In particular, it is unclear how the OH− ion-dipoles in HAp lattices contribute to electret performance. Herein, we show that HAp with controlled OH− ion content exhibits excellent performance as an electret. We prepare OH−-defect-controlled HAp samples either by restricted dehydration during thermal process or by valence control through the substitution of Ca2+ with Nd3+. The experimental results prove that the electrets prepared by partially dehydrated HAp and Nd-substituted HAp with a small number of OH− ions showed better performance. Our results suggest that the OH− ion-dipole polarization contributes negatively to the electret performance. [ABSTRACT FROM AUTHOR]

• Symmetrical PCFC with high performance is demonstrated. • Proton formation in PrBaFe 2 O 5+ δ electrode is systematically investigated. • Redox stability of PCFC with PrBaFe 2 O 5+ δ electrode is firstly confirmed. The proton conduction behavior and electrochemical performance of PrBaFe 2 O 5+ δ (PBF) are firstly studied for use as promising anode materials in symmetrical proton-conducting solid oxide fuel cells (PCFCs). This study focuses on the investigation of protonic defect formation in PBF and its properties as an electrode, including its chemical stability, electrochemical performance and redox stability. PBF is found to have proton conductivity at intermediate temperatures, which contributes to improved hydrogen oxidation reaction and water formation reaction at the anode and cathode, respectively. Hence, the symmetrical PCFC exhibits a peak power density of 301 mW∙cm−2 and total resistance of 0.77 Ω∙cm2 at 700 °C. Further, it shows excellent redox-cycle stability upon cycling between fuel and air under a current load. The electrochemical analysis and redox cycling tests of the PBF anode demonstrate that PBF is an attractive candidate for alternative material for symmetrical PCFCs. [ABSTRACT FROM AUTHOR]

Sulfonated poly(ether ether ketone) (SPEEK) membrane with high sulfonation degree (SD) is a promising substitute of Nafion as proton exchange membrane (PEM), due to the excellent proton conductivity and low cost. However, its widespread application is limited by the inferior structural stability. Here, we report the fabrication of high SD SPEEK membrane with outstanding structural stability through an in-situ molecular-level hybridization method. Concretely, the ionic nanophase of SPEEK membrane is filled with precursors, which are then in-situ converted into polymer quantum dots (PQDs) by a microwave-assisted polycondensation process. In this manner, the micro-phase separation structure of SPEEK membrane is well maintained. PQDs with abundant hydrophilic functional groups together with the inherent –SO 3 H groups impart hybrid membrane highly enhanced proton conductivity of 138.2 mS cm−1 at 80 °C, which is comparable to Nafion. This then offers a 116.3% enhancement in device output power. Meanwhile, PQDs act as cross-linkers via generated electrostatic interactions with SPEEK, affording hybrid membrane with SD of 94.1% an ultralow swelling ratio of 1.35% at 25 °C, about 35 times lower than control membrane. More importantly, the in-situ molecular-level hybridization method is versatile, which can also boost the performances of chitosan (CS)-based membranes. [Display omitted] • In-situ molecular-level hybridization by polymer quantum dots (PQDs) is proposed. • PQD hybridization makes high-sulfonation-degree SPEEK membrane useful. • PQDs in ionic nanophase of SPEEK act as cross-linkers via electrostatic interaction. • The functional groups on PQDs work as additional proton transfer sites. • Structural stability and proton conductivity of SPEEK membrane are highly enhanced. [ABSTRACT FROM AUTHOR]

• A nickel(II) hydrogen-bonded organic framework (NiHOF) was synthesized based on an organodisulfonate. • The NiHOF exhibit a highly hydrogen-bonded structure with simple paramagnetism. • The NiHOF displays temperature- and humidity-dependent proton conduction. A three-dimensional nickel(II) hydrogen-bonded organic framework (NiHOF), formulated as [Ni(H 2 O) 2 (EtOH) 2 (MeCN) 2 ][nds] (NiHOF-HGNU-2 , H 2 nds = 1,5-Naphthalenedisulfonic acid, HGNU = Huanggang Normal University), was synthesized and magnetically and electrically characterized. Single-crystal X-ray diffraction (SC-XRD) analysis revealed that extensive hydrogen bonding interactions formed between the [Ni(H 2 O)(EtOH)(MeCN)]2+cations and organodisulfonate anions nds2−, leading to a highly hydrogen-bonded network. Variable-temperature SC-XRD and thermogravimetric analysis both reveal the crystalline sample of NiHOF-HGNU-2 can be thermally stable up to 400 K. Magnetic investigations reveal the uniaxial magnetic anisotropy (D = -9.87 cm−1) of the distorted octahedral Ni2+ ions of NiHOF-HGNU-2 without slow magnetic relaxation. Alternating current impedance spectroscopy indicate NiHOF-HGNU-2 exhibits temperature- and humidity-dependent proton conduction behavior with the highest measured conductivity reaching 1.15 × 10−4 S cm−1 at 85 °C and 98 % relative humidity, suggesting a supramolecular proton conductor of the NiHOF-HGNU-2. The forgoing results not only provide a new Ni-based proton conductor but also an organodisulfonate strategy for building supramolecular proton-conducting materials. A nickel(II) hydrogen-bonded organodisulfonate framework was reported to exhibit temperature- and humidity-dependent proton conduction behavior. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The developments of POM-based macrocycles including their syntheses, structures, properties, and related applications are summarized. • The interesting modular hierarchical assembly of POM-based macrocycles was summarized. • The structure–property/application relationships of POM-based macrocycles are summarized. • The development prospects and the present challenges in the study of POM-based macrocycles are discussed. Polyoxometalate (POM) macrocycles have been extensively investigated due to their potential applications in various fields, including sensing, optics, magnetism, proton conduction, catalysis, and host–guest chemistry, leveraging the advantages offered by their unique wheeled structures. In this review, the recent progress of POM macrocycles, including their assembly strategies, crystal structures, properties, and various applications, is reviewed. Additionally, the current obstacles and challenges regarding the design and construction of POM macrocycles are also discussed. [ABSTRACT FROM AUTHOR]

• A new dinuclear holmium(III) complex was synthesized. • The Ho(III) complex exhibit highly hydrogen-bonded supramolecular structure. • The Ho(III) complex display slow magnetic relaxation and proton-conducting behavior. Multifunctional magnetic-electrical materials are highly interesting, such as proton-conductive lanthanide single-ion magnets (SIMs). Herein, we reported the synthesis, crystal structure, magnetic and electrical properties of a bifunctional binuclear holmium(III) complex, [Ho 2 (H 2 dobdc)(H 2 O) 14 ]·(H 2 dobdc) 2 ·8H 2 O (Ho 2 , H 4 dobdc = 2,5-dioxodo-1,4-benzenedicarboxylate), which was constructed by a hydroxy‑functionalizd dicarboxybenzene and holmium(III) ions. Interestingly, single-crystal X-ray diffraction analysis reveals a highly hydrogen-bonded supramolecular structure and highly oxygenated site were formed within the complex. Magnetic measurements indicate the complex exhibits filed-induced slow magnetic relaxation property. Additionally, the impedance spectroscopy measurements show the complex also exhibits humidity- and temperature-dependent proton conduction behaviour via the Grotthus mechanism. These results support a proton-conductive holmium(III) single-ion magnet of Ho 2. This work not only provides the first bifunctional HoIII complexes showing slow magnetic relaxation and proton-conducting behaviour but also a supramolecular way for advanced magnetic-electrical systems linking slow magnetic relaxation with unique proton conducting behaviour exploiting a possible cooperative behaviour. A dinuclear holmium(III) complex with a highly hydrogen-bonded supramolecular structure was reported to show field-induced slow magnetic relaxation and proton-conducting behavior. [Display omitted] [ABSTRACT FROM AUTHOR]

Sulfonated polyarylene membranes are demonstrated to be efficient as proton exchange membranes (PEMs) for proton exchange membrane fuel cells (PEMFCs) in clean energy conversion systems. In this study, we design and synthesize a series of sulfonated polyarylene with all-carbon backbones and densely sulfonated pendant groups, which can be prepared by copolymerization of 1,3-Disulfonic acid benzaldehyde, 1,1,1-trifluoroacetone and biphenyl under superacid-catalyzed conditions. Rigid, hydrophobic backbone and hydrophilic side chains make the membrane form good microphase separation morphology. The PEMs exhibit high proton conductivity (404 mS cm−1) and excellent dimensional stability (swelling ratio lower than 24% and water uptake lower than 40%) at 80 °C. Moreover, the PEMs show good oxidization stability (the retaining weight rate of membrane up to 99.2% for 1 h oxidative treatment), and the oxidization stability and degradation mechanism of Ar 3 CH in polymer backbone are also studied. The H 2 /O 2 fuel cell assembled with PEMs exhibited a maximum peak power density of 560 mW cm−2. It indicates that all-carbon main chain and densely sulfonated structure show great potential for improving the performance of PEMs. • The low-cost and commercial monomers were used to prepare the ether-free PEMs by a simple preparation route. • PEMs with all-carbon rigid skeleton and dense sulfonated side chain have high electrical conductivity and low SR. • The stability and degradation mechanism of PEMs were investigated. • P (BP-0.6SBA-TFK) membrane performs better in fuel cells than commercial Nafion117. [ABSTRACT FROM AUTHOR]

Lanthanide metal-organic frameworks (Ln-MOFs) have exhibited remarkable capabilities in color change, luminescence, proton conduction through the strategic modification of metal nodes, organic ligands and channels or pores. By modifying the electron-deficient bipyridinium to contain carboxylic acid moieties and coordinating them with the luninescent Eu3+ ion, a unique and versatile Eu-MOF has been synthesized. Under UV light conditions, the complex shows an obvious color change from colorless to blue, which is due to the formation of viologen radicals after photoinduced electron transfer (PIET) process. As we all know, the changed color is caused by the alteration of absorption intensity, ultimately impacting its luminescence as well. Thus, the bright and strong red fluorescence of this complex is quenched upon continuous UV light irradiation, which may be attributed to intramolecular energy transfer from the excited state of the europium ion to the colored state of the CV ligand. Based on the control of multiple colors of the complex, the designed encryption model can realize multiple anti-counterfeiting of real numbers. In addition, the conductivity of this compound increases significantly after UV illumination, showing excellent photo-modulated proton conductivity. In short, our work has proposed a multifunctional bipyridinium-based Ln-MOF with photochromism, photo-switchable photoluminescence and proton conduction, which offers valuable insights for the creation of versatile switchable materials based on MOFs. [Display omitted] • A novel viologen-based Eu-MOF exhibits reversible photochromism and photo-modulated photoluminescence. • The colored Eu-MOF presents higher proton conductivity after UV irradiation. • The Eu-MOF can be used for multiple anti-counterfeiting encryption of information. [ABSTRACT FROM AUTHOR]

The ionic conduction of perovskite-type oxides remains a fundamental and important issue in the research of solid oxide fuel cells (SOFCs). In this research, a thin perovskite-type ceramic membrane was fabricated in situ at anode side attached to the surface of Gd 0.2 Ce 0·8 O 1.9 (GDC20) electrolyte membrane. The single cell working between H 2 and static air showed good stability (over 50 h), high open circuit voltages (above 1.0 V) as well as high peak power densities (749-264 mW cm−2) from 600 to 500 °C. Detailed analyses of current research demonstrated that the thin perovskite film mainly possessed the oxygen ion conductivity under reducing atmosphere, while the proton conductivity was severely suppressed, showing the high flexibility in ionic conductivity of perovskite oxide. This work also implies that the oxygen ion and proton conduction may be in high correlation with each other, which provides important information to unveil the nature of the ionic conduction of perovskite-type oxides. [ABSTRACT FROM AUTHOR]

The inorganic silica immobilized PWA based (Si-PWA)-PVA/PTFE composite membrane was developed by an amalgamation of pore filling and layer by layer (LBL) casting. The composition of the top layer was optimized to be 0.3 M PWA: 0.2 M TEOS: 0.15PVA concerning to proton-conductivity and methanol permeability of the membrane. Surface morphological studies and elemental analysis were carried out by using SEM-EDX. The FT-IR and XRD analysis had confirmed the intercalation of sol with PTFE. Thermal deformation of the membrane was studied by TGA and it is stable up to 180 °C. Ion exchange capacity and water uptake were determined to be 2.38 meq per gram and 21.7%. The membrane has exhibited maximum proton conductivity of 41.2 mS cm−1 at 100 °C. The membrane has significantly lower methanol permeability of 3.2 × 10−7 cm2 S−1 compared to that of Nafion117 (7.9 × 10−7 cm2 S−1) at 28 °C and the same trend was observed at 40, 60, and 80 °C. The (Si-PWA)-PVA/PTFE composite membrane is showed enhanced proton conductivity and lower methanol permeability at elevated temperatures. Image 1 • The (Si-PWA)-PVA/PTFE composite membrane was successfully synthesized. • The membrane exhibited increased proton conductivity of 41.2 mS cm-1 at 100 °C. • The membrane has significantly lower methanol permeability compared to Nafion117. • The membrane was thermally stable up to 180 °C with aggregate weight loss of 4.1%. • The composite membrane is promising for application in high-temperature DMFC. [ABSTRACT FROM AUTHOR]

With the wide use of platinum alloy electrocatalysts proton exchange membrane fuel cells, the dissolution of transition metal in the acid environment of catalyst layer becomes a major concern due to the decreased catalytic activity during long-term operation. Although great efforts have been done, few attention is paid to the effect of transition metal ion contamination of Nafion ionomer that wrapped around catalyst particles within catalyst layer which might greatly influence the proton conduction. To elucidate such effect, ultrathin Nafion film on SiO 2 model substrate is prepared via self-assembly method to represent the ionomer in fuel-cell catalyst layers, and the ultrathin film with specific thickness is further equilibrated in Co(NO 3) 2 /HNO 3 solutions with different Co2+ concentration to achieve different doping level. Conductivity measurements demonstrate that the non-precious metal contamination severely worsens proton conduction of Nafion ionomer, but it is always ignored before. In addition, when the occupation of H+ in Nafion ionomer is less than 50%, the activation energy shows a sharp increase, indicating a possible change in proton conduction mechanism. Image 1 • 40 and 120 nm Nafion thin films with different cobalt doping levels are prepared. • Effect of cobalt doping level on proton conduction of Nafion ionomer is tested. • The increase of cobalt doping level seriously reduces the proton conductivity. [ABSTRACT FROM AUTHOR]

The hydrogen diffusivity in the La 0.91 Sr 0.09 ScO 3–δ oxide was investigated by the hydrogen isotope exchange and the high-temperature thermogravimetry in the temperature range of 500–800°С and pressure ranges of hydrogen and water vapour of 0.2–4.1 kPa and 8.1–24.3 kPa, respectively. The values of hydrogen diffusion coefficients were obtained. The electrical conductivity of La 0.91 Sr 0.09 ScO 3–δ was studied using the electrochemical impedance spectroscopy in the temperature range of 300–750 °C and molecular hydrogen (protium and deuterium) pressure of 0.2 kPa. The H/D-isotope effect in conductivity and diffusivity was observed. The structural positions of protonic defects, determining transport in water- and hydrogen-containing atmospheres, were determined by the neutron powder diffraction. Image 1 • The hydrogen diffusion coefficients are measured in Sr-doped LaScO 3 oxide. • H/D-isotope effect in the conductivity is observed in Sr-doped LaScO 3 oxide. • Sr-doped LaScO 3 oxide is found to be unipolar protonic conductor in H 2 atmosphere. • The structural positions of protonic defects in the Sr-doped LaScO 3 are determined. [ABSTRACT FROM AUTHOR]

A composite membrane was synthesized by functionalizing the Polytetrafluoroethylene film with inorganic Zirconium Phosphate and polyvinyl alcohol. The hybrid method of pore infiltration and layer by layer coating was adopted to obtain the membrane. Hydrophilicity of the PTFE support was increased by chemical treatment. The proton conductivity of the membrane was increased considerably by using chemically treated hydrophilic support. The composition of ZrP and PVA in the solution (sol) was optimized with respect to methanol crossover and proton conductivity. The top view of the membrane surface morphology was observed by using SEM and EDX revealed the presence of 31.9% Zirconium and 26.44% Phosphate in the synthesized membrane. The membrane top layer functional groups were analyzed by FT-IR and the spectra confirm the incidence of functional groups related to ZrP and PVA. Thermal stability of the membrane was analyzed using TGA-DTA and it was stable up to 140 °C. The membrane was mechanically stabile with a mechanical strength of 44 MPa. The membrane possessed proton conductivity of 28.1 mS cm−1 and low methanol permeability (14.5 × 10-7 cm2 s−1) at 80 °C. Image 1 • PTFE-ZrP-PVA composite membrane was synthesized for high temperature DMFC. • The methanol permeability of the membrane ∼3 times lower than that of Nafion117. • The membrane is mechanically and thermally stable for commercial applications. • Enhancement of membrane properties were attained at higher temperatures up to 80 °C. • The PTFE-ZrP-PVA membrane is economical to use in DMFC. [ABSTRACT FROM AUTHOR]

• Tunable electrochemical properties of BZY10 by proper sample processing conditions. • Low bulk and grain boundary proton conductivity for BZY10 by long sintering time. • Higher/lower ionic transport number in bulk/grain boundary by longer sintering time. • Decreasing Schottky barrier height in grain boundary core by adding ZnO into BZY10. BaZr 0.9 Y 0.1 O 3-δ (BZY10) is a popular composition for the electrolyte in protonic ceramic cells, due to its relatively high proton conductivity, excellent chemical stability, and good compatibility with NiO negatrode substrate during high temperature co-sintering. The microstructure of BZY10 is highly dependent on sample processing, leading to large discrepancy of the electrochemical performance of BZY10 in literature. In this work, three BZY10 samples were prepared by different sample processing and sintering conditions, and the grain interior (bulk) and grain boundary partial conductivities of protons and holes were separated. The sintering processes influenced the transport properties of pristine BZY10 samples significantly, and longer sintering time at high temperature (1650 – 1700 °C) leads to lower proton conductivity in both bulk and grain boundary. However interestingly, longer sintering time resulted in higher ionic transport number of bulk conduction, but lower ionic transport number of grain boundary conduction, possibly due to increasing Ba-deficiency in bulk by longer annealing at high temperature. Besides, adding ZnO into BZY10 decreased the proton conductivity in both bulk and grain boundary, but its ionic transport number of bulk conduction increases. A further analysis based on the theory of space charge layer indicated that adding ZnO leaded to decreased Schottky barrier height in the grain boundary core, and the highest Schottky barrier height was observed in the pristine sample which was sintered for longer time. The results obtained in this work suggest a potential strategy to regulate the transport properties of BZY10 by choosing appropriate approaches for sample processing to control the microstructure and local composition of the polycrystalline BZY10 ceramic electrolyte. [ABSTRACT FROM AUTHOR]

Artificial synapses based on protonic memristor have great potential in constructing neural morphological computing system. However, further investigation is still required to understand the proton conduction mechanism of protonic memristors. Here, we present a new type of Ga doped boehmite based memristors with artificial synapse functionality, which can achieve variations in conductance levels by precise control of the Ga doping content. Compared with undoped boehmite, there is no obvious change in crystal structure, particle morphology and chemical bond doped with different of concentration Ga. The change in the electrical conductance is found to be a result of proton transfer, closely resembling what takes place in biological neurons. Furthermore, the first-principle density functional theory (DFT) calculation is conducted to elucidate the proton conduction mechanism and zig-zag-like pathways for proton transfer in the memristor was proposed. The results establish a precedent for tuning the proton transfer behaviour in memristor-based neural devices, thereby enhancing their practicality. It provides a novel approach for studying the resistance switching behavior in proton transfer-based memristors. • The conductivity level of Ga doped Boehmite Memristors are controlled by the doping content of Ga. • Ga doped Boehmite Memristors achieve basic synaptic functions. • The influence of Ga doping on the proton migration barrier in Boehmite was studied by DFT. • Resistive switching mechanism of proton transfer based memristor revealed by DFT. [ABSTRACT FROM AUTHOR]

Cs 3 PW 12 O 40 (Cs3WPA) composites with CsHSO 4 (CHS) were prepared, and their effects on proton conductivity were investigated. These composites comprise CHS, H 2 SO 4 , and Cs3WPA, where the Cs3WPA served as the matrix element. The CHS in the composites became amorphous, and it was caused by the strong acidic catalytic properties and a large surface area of Cs3WPA. Amorphous-CHS provides an effective proton carrier, and the conductivity increases with increasing amorphous-CHS content. CHS-H 2 SO 4 -Cs3WPA ternary system was prepared based on the three aforementioned components of the composites. It was found that the activation energy of proton conductivity for the ternary system is lower than that of a composite with an identical composition. The difference of activation energy between composite and ternary system results from the difference of the quantity of incorporated water molecules. • The Cs 3 PW 12 O 40 (Cs3WPA) composites from CsHSO 4 (CHS) and H 3 PW 12 O 40 consist of CHS, H 2 SO 4 , and Cs3WPA. • The CHS in the composites became amorphous, and it is suggested that this is caused by the characteristic properties of Cs3WPA. • The amorphous-CHS is considered to donate the mobile proton carriers, enhancing proton conduction. • Some water molecules are presumed to be incorporated with H 2 SO 4 in the composite, and provide proton hopping sites. • CHS-H 2 SO 4 -CsWPA system based on the composite, it includes more incorporated water than the composite and decrease in the activation energy. [ABSTRACT FROM AUTHOR]

Semiconductor ionic materials (SIM) have recently gained broad attention due to their unique structural and chemical properties that enable efficient proton transport, making them promising materials for advanced fuel cell applications. This mini-review provides an overview of the proton transport phenomena in SIM and discusses their significance and future perspectives. We discuss the different types of SIMs, their proton transport mechanisms, and the factors that affect their performance. Furthermore, we emphasize the correlation between traditional perovskite oxides and SIMs and how this can be leveraged to improve the development of more advanced proton conductors for fuel cells. Also, we have highlighted the Proton-coupled electron transfer (PCET) mechanism in SIM. This mini-review provides a comprehensive overview of the current state of this emerging field, including its scientific foundations, future prospects, and applicable materials, technologies, devices, and basics for proton ceramic fuel cells (PCFCs). • This review covers efficient proton transport in SIM for fuel cell applications. • Discussed SIM protons transport's relevance, prospects, and factors. • To develop fuel cell proton conductors, we study Perovskite-SIM interactions. • This review covers PCET methods, challenges, and SIM's future. [ABSTRACT FROM AUTHOR]

Protonic solid oxide fuel cells (P-SOFCs) have garnered significant attention due to their high power density and efficiency in operating at 400–700 oC. The development of high-performance cathode materials, characterized by excellent proton, oxide-ion, and electron conductivity, catalytic activity for oxygen reduction reaction, and long-term stability, is essential and urgently needed for realizing high-efficiency P-SOFCs. Recently, machine learning (ML) has emerged as a powerful tool in materials science, playing a central role in transitioning away from traditional approaches for developing new materials. In this review, recent advances of high-performance cathodes are summarized, and the challenges associated with their developments are highlighted. Furthermore, the potential ML-guided perspectives in terms of predicting proton, oxide-ion, and electron conductivity, catalytic activity, hydration ability, and stability for addressing these challenges are detailedly discussed, providing insights into the design and optimization of high-performance cathodes. Finally, the difficulties faced are presented for better utilization of ML in developing high-performance cathodes. In a word, this review not only presents the latest advances and challenges in high-performance cathodes for P-SOFCs but also highlights the promising role of ML in guiding their development. [Display omitted] • Machine learning guided perspectives in developing high-performance cathodes. • Proton uptake and conduction mechanisms in oxides. • The advances and challenges in developing high-performance cathodes. [ABSTRACT FROM AUTHOR]

• A 1D MOF based on benzothiadiazole derivative has been solvothermally synthesized and fully characterized. • JXUST-26 exhibits good solvents and pH stabilities as well as relatively good thermal stability. • The proton conductivity reaches 3.24 × 10–7 S·cm-1 at 80 °C under 98% relative humidity. A one-dimensional metal–organic framework (MOF) with the formula of {[N i (BIBT)(pydc)(H 2 O) 2 ]·H 2 O} n (JXUST-26 , BIBT = 4,7-bis(1 H -imidazole-1-yl)-2,1,3-benzothiadiazole, H 2 pydc = 3,5-pyridinedicarboxylic acid) has been successfully synthesized under solvothermal condition, which crystallizes in the monoclinic C 2 /c space group. It is noteworthy that JXUST-26 exhibits good solvents and pH stabilities as well as relatively good thermal stability. The proton conductivity increases with increasing temperature, and reaches 1.65 × 10−8 S·cm−1 at 30 °C and 3.24 × 10−7 S·cm−1 at 80 °C under 98% relative humidity, respectively. In the low temperature range of 303–353 K, the activating energy (E a) is 0.51 eV, which belongs to the Vehicle mechanism. A NiII-based metal-organic framework based on benzothiadiazole derivative has been solvothermally synthesized, which exhibits good solvent, pH and thermal stability as well as significant proton conductivity (3.24 × 10–7 S·cm-1 at 80 °C and 98% RH). [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Specific focus on broadly neglected uniformity/sufficiency of filler modification. • Optimized surficial geography of SNMMT toward reformed interface in Nafion matrix. • Markedly promoted conductivity of Nafion/SNMMT over any reported composite PEM. • Evident advantages on cell output and durability among related PEMFC/DMFC studies. Interfacial compatibility between filler and matrix substantially affects the overall morphology and performance of nanocomposites. Compared with bare montmorillonite (MMT), surface modified product such as sulfonated MMT (SMMT) has been known to render optimized interfacial compatibility in composite proton exchange membranes (PEMs) for proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). Nevertheless, in-depth understanding and investigation on the sulfonation of MMT are seldom focused, such as uniformity and sufficiency. Herein, these broadly neglected issues are proposed and resolved using an exemplary polynorepinephrine (PNE)-regulated SMMT (SNMMT). Rather than direct sulfonation utilizing the inherent hydroxyl groups of MMT, a PNE coating with ample hydroxyl groups is deposited on MMT beforehand, which results in more homogeneous and sufficient sulfonation of SNMMT. Compared with normal SMMT, this alteration on surficial geography of filler functionalization brings significant benefits when composited with Nafion matrix, including harmonized filler-matrix compatibility, improved mechanical stability and enhanced proton conduction. Moreover, the antioxidative ability of PNE layer enables improved chemical stability of nanocomposite PEM. The Nafion/SNMMT composite PEM achieves 0.275 S cm−1 proton conductivity at 95 °C in water, evidently beyond any previously reported composite PEMs using normal SMMT. Equipped with this reformed nanocomposite PEM, both PEMFC and DMFC display competitive peak power densities (1.121 W cm−2 with H 2 /O 2 at 80 °C/100 % relative humidity (RH) for PEMFC, and 0.228 W cm−2 with 1.6 M methanol/100 % RH O 2 for DMFC), and simultaneously show minor performance deteriorations in constant current density operation and RH cycle tests. It would be instructive the specific focus and reformation on the uniformity and sufficiency of filler modification may render significant interface and performance advancements for nanocomposites. [ABSTRACT FROM AUTHOR]

• Developed an electrochemical based hydrogen isotope sensor using synthesized mixed-phase Sr 2 CeO 4 - SrCe 0.85 Y 0.15 O 3-ᴓ ceramic. • The sensor is tested at different temperatures (400, 450 & 500 °C) with known and fixed calibrated hydrogen concentration in reference and working side. • The sensor exhibited a stable electrochemical potential at 450 & 500 °C and its values were found to be close to the theoretical estimations. One of the most significant fundamental requirement for the Tritium Extraction System (TES) of fusion breeder blanket system with liquid Pb-Li as tritium breeder is an online, quick, accurate, and reliable measurement of hydrogen isotope concentration in liquid lead lithium (Pb-Li). Though Permeation-based hydrogen isotope sensors have been reported for this, they corrode in the presence of liquid Pb-Li. This corrosion greatly lowers the permeation flux and hence the sensor's performance over time. As a result, they may need to be replaced frequently, which is a limitation of permeation-based sensors. Solid state proton conducting ceramics have attracted a significant importance in applications related to hydrogen measurement, transport, fuel cell etc. In order to address the issues in hydrogen concentration measurement associated with permeation-based sensors as well to establish an alternate measurement technique, solid state proton conducting electrolyte-based hydrogen isotope sensors are being proposed in literature. These sensors have good physical and chemical sustainability in liquid Pb-Li at higher temperatures. This work presents the detailed description of the design, fabrication and testing of electrochemical–-based hydrogen isotope sensor using in-house synthesized mixed-phase Sr 2 CeO 4 - SrCe 0.85 Y 0.15 O 3-ᴓ ceramic. The disc shaped pellet of mixed phase Sr 2 CeO 4 - SrCe 0.85 Y 0.15 O 3-ᴓ ceramic is used as a solid electrolyte in the sensor. The sensor is tested at various temperatures (400, 450 & 500 °C) with known and fixed calibrated hydrogen concentration in reference and working side. The sensor exhibited a stable electrochemical potential at 450 & 500 °C, and its values was found to be close to the theoretical estimations using Nernst's equation (deviation up to ∼55 mV). In contrast, the sensor at 400 °C showed the shift in potential throughout the experiment (∼2 h). [ABSTRACT FROM AUTHOR]

• The benzothiadiazole-based 3D Zn(II) MOF JXUST-13 could be considered as a difunctional material of fluorescence sensing cations and proton conduction. • JXUST-13 exhibited rarely fluorescence blue-shifted sensing towards Al3+ and Ga3+ ions, and it also showed good sensitivity, selectivity, anti-interference characteristic and cyclicity. In addition, JXUST-13 could rapidly detect Al3+ and Ga3+ ions by naked eyes and portable fluorescence trips. • JXUST-13 exhibited relatively high proton conductivity of 1.97 × 10−5 S·cm−1 at 80 °C and 98 % relative humidity. Energy shortage and environmental pollution become increasingly serious. Thus, there is urgent need to develop new functional materials to deal with these problems. Metal−organic frameworks (MOFs) are ideal candidates for fluorescence sensing pollutants and proton conduction. A benzothiadiazole-based three-dimensional (3D) Zn(II) MOF with the formula of {[(CH 3) 2 NH 2 ][Zn 3 (bbip)(BTDI) 1.5 (OH)]·DMF·MeOH·3H 2 O} n (JXUST-13 , bbip = 2,6-bis(benzimidazol-1-yl)pyridine and H 4 BTDI = 5,5′-(benzo[ c ][1,2,5]thiadiazole-4,7-diyl)diisophthalic acid) with fluorescent ligands and rich hydrogen bond framework was used as a cation fluorescence sensor and proton conduction material. The fluorescence experiment revealed that JXUST-13 could detect Al3+ and Ga3+ ions by fluorescence blue shift and slight fluorescence enhancement. And it showed high sensitivity, good selectivity, anti-interference performance and cyclicity. The detection limits of JXUST-13 toward Al3+ and Ga3+ ions were 4.0 μM and 0.67 μM, respectively. Importantly, it could be rapidly detected by fluorescent test strips and naked eyes. The sensing mechanism may be due to the presence of electron transfer and the formation of exciplex. Proton conduction result indicated that the maximum conductivity value of JXUST-13 was 1.97 × 10−5 S·cm−1 at 80 °C and 98% RH. And the conductivity increased with humidity and temperature. The activation energy (E a) value of JXUST-13 was 0.47 eV, which revealed the Vehicle mechanism. Therefore, JXUST-13 could be considered as a rare difunctional materials of blue-shifted fluorescence sensor for Al3+, Ga3+ ions and proton conduction. [Display omitted] A benzothiadiazole-based 3D Zn(II) MOF JXUST-13 was used as a cations sensor and proton conduction material. Importantly, JXUST-13 could detect Al3+and Ga3+ions via rare fluorescence blue shift, and it also could be recognized by naked eyes and fluorescent test strips. Proton conduction results indicated that conductivity value of JXUST-13 was 1.97 × 10−5 S·cm−1 at 80 °C and 98 % RH. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag-NTO NRs were firstly prepared for high-performance acetonitrile detection. • The proton conductive sensing mechanism of Ag-NTO NRs was investigated. • Ag-NTO NRs had an ultra-fast response (∼5 s) to 0.1 ppm acetonitrile at 75 °C. • Ag-NTO NRs showed extremely high selectivity to CH 3 CN due to its high polarity. The detection of acetonitrile is of great importance in a variety of fields related to environmental monitoring and public health. Poor selectivity and high operating temperature are two bottlenecks for existing acetonitrile sensors. In this study, high-performance acetonitrile detection was realized by using Ag-decorated sodium titanate nanoribbons (Ag-NTO NRs) which exhibited a unique surface proton-conductive sensing mechanism. Due to the high polarity of acetonitrile, acetonitrile promoted the proton conduction of Ag-NTO NRs, whereas other common reducing VOCs such as methanol, ethanol, and formaldehyde induced an opposite resistance change, resulting in an inherently high acetonitrile selectivity of Ag-NTO NRs. 5 % Ag-NTO NRs were capable of rapidly detecting acetonitrile (∼5 s) with extremely high selectivity and stability at 75 °C, while also exhibiting a low detection limit of 0.1 ppm (500 times lower than the IDLH value of acetonitrile). Finally, the proton-conductive sensing mechanism of Ag-NTO NRs was investigated in depth, and the influences from Ag loading, applied voltage, humidity, and operating temperature were discussed. [ABSTRACT FROM AUTHOR]

A novel polyoxometalate-based coordination supramolecule was synthesized via a hydrothermal method. The compound exhibited high proton conductivity with good stability. Polyoxometalate skeleton, 2-methylimidazole ligands and water molecules provided continuous hydrogen bonds for the proton conduction. Kinetic studies indicated that the proton conduction mechanism of the compound followed the vehicle mechanism. Developing new low-cost and efficient proton-conducting materials remains an attractive and challenging task. Herein, a Preyssler-type polyoxometalate derived coordination compound had been synthesized with a hydrothermal method, namely, H 4.5 NaCo 5 (2-MI) 15.5 (2-MI) 3 [NaP 5 W 30 O 110 ]·5H 2 O (1) (where 2-methylimidazole is abbreviated as 2-MI, and partial 2-MI was deprotonated). The structure was characterized by single crystal X-ray diffraction, PXRD, FT-IR, TG, CHN and ICP-OES elemental analyses. We studied the relationship between the crystal structure and proton conduction of compound 1 and found that the presence of 2-MI reduced the leakage of polyoxometalate under high relative humidity. Meanwhile, the strong interaction of the counter cation Na+ with water is beneficial to form more hydrogen bonds. Compound 1 showed the maximum proton conductivity with a value of 4.42 × 10−3 S cm−1 at 367 K and 97% RH. Kinetic investigation indicates that the proton conduction mechanism of compound 1 follows the vehicle mechanism. [ABSTRACT FROM AUTHOR]

One imidazole multi-carboxylate-based {[Sr(o -CPhH 2 IDC)(H 2 O) 2 ]·2H 2 O} n (1) is prepared. Variable-humidity and variable-temperature experiments indicate that the proton conductivity of the compound will increase significantly with the increase of temperature or humidity. The complex showed high water and chemical stabilities, and also indicated good structural stability after the electrochemical tests. To design and obtain proton conductive MOFs with high stability, we used 2-(2-carboxylphenyl)-1 H -imidazole-4,5-dicarboxylic acid (o -CbPhH 4 IDC) to react with Sr(NO 3) 2 under hydrothermal condition. Fortunately, a novel 1D chain MOF, {[Sr(o -CPhH 2 IDC)(H 2 O) 2 ]·2H 2 O} n (1) was obtained. Its thermal, water and chemical stabilities were investigated by TGA and PXRD determinations. Impressively, variable-temperature and variable-humidity experiments for 1 indicate that its proton conductivity increases significantly with the increase of temperature or humidity. MOF 1 has optimal proton conductivity of 6.08 × 10−5 S cm−1 under 98% RH and 100 °C, which can be compared to the reported imidazole dicarboxylate-based MOFs. The results of structural analysis, E a values and water vapor absorption were utilized to get an insight into the proton mechanism. The time-dependent tests illustrate its ability to keep conductivity up to 24 h. [ABSTRACT FROM AUTHOR]

A simple conventional aqueous solution "one-pot" method was developed to prepare two Polyoxometalate-based lanthanide-amino acid coordination polymers served as proton conductors. Owing to the considerable yield in a short period as well as green chemical reagents involved and preparation process, the synthetic strategy has numerous advantages of cost-effective, facile, highly purified, scalable and environmentally friendly. The highest conductivity reached up to 4.97 × 10−3 S cm−1 at 80 °C and 97% RH. Unlabelled Image • A simple conventional aqueous solution "one-pot" method was developed. • Two Polyoxometalate-based lanthanide-amino acid complexes were prepared. • These compounds can be used as candidates for proton conducting materials. [ABSTRACT FROM AUTHOR]

Abstract Inspired by the parallel performing of storage and processing information in biological synapse, artificial synapse that can control ionic and protonic currents are ideal means for attracted tremendous attention as a promising option to break the von Neumann bottleneck. Here we demonstrate an artificial synapse with tunable synaptic behavior based on solution-processed two-dimensional (2D) C 3 N/polyvinylpyrrolidone (PVPy). The proton modulated memristive characteristics of synaptic device are verified by ambient pressure X-ray photoelectron spectroscopy under different H 2 O gas atmosphere. The highly proton conducting of C 3 N/PVPy matrix stems from the hydrogen bonding network between C 3 N and PVPy, as well as the large amount of ordered nitrogen atoms in C 3 N. The artificial synapse ensure a direct imitation of short-term and long-term plasticity in biological synapses including excitatory post-synaptic current (EPSC), paired-pulse facilitation (PPF), paired-pulse depression (PPD), PPF following PPD and post-tetanic potentiation (PTP). The C 3 N/PVPy matrix-based memristor which can mimic the synapse cleft based on proton conducting mechanism may find further applications in artificial intelligence. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Abstract One critical issue for the application of high-temperature polymer electrolyte membranes (HT-PEMs) is to obtain good balance between their proton conductivities and mechanical strength. In this work, a novel strategy has been developed to achieve the balance by increasing the number of functional groups in the grafting site of the side chain of polysulfone (PSU). 2,4,6-tri(dimethylaminomethyl)-phenol (TDAP) with three tertiary amine groups was grafted on PSU (TDAP-PSU) to achieve higher phosphoric acid (PA) uptake at a lower grafting degree. Moreover, the bundle of amine groups in one grafting site reduces the volume swelling compared to the single tertiary amine group grafted PSU membrane (DMA-PSU). Thereby, the TDAP-PSU membrane with 75% grafting degree achieves comparable PA uptake with the DMA-PSU membrane with 99% grafting degree, whereas the mechanical strength of former membrane after PA doping is 2.2 times higher than that of the later one after PA doping. Moreover, single cells based on the TDAP-PSU membrane reach the peak power density of 453 mW cm−2 and excellent stability without external humidification. Overall, increasing the number of active groups in the grafting site of the polymer side chain is a promising strategy to deal with the trade-off between the proton conductivity and membrane dimensional stability of HT-PEMs. Graphical abstract fx1 Highlights • 2,4,6-tri(dimethylaminomethyl)-phenol grafted polysulfone (TDAP-PSU) was synthesized. • Phosphoric acid doped TDAP-PSU membrane shows high conductivity and tensile stress. • The fuel cell with the membrane shows a power density of 498 mW cm−2 at 180 °C. [ABSTRACT FROM AUTHOR]

Abstract The Cold Sintering Process (CSP) was applied to CsH 2 PO 4 , a proton conducting electrolyte. The powders were sintered between 120 °C and 200 °C under 300 MPa for 1 h and the ceramics investigated for their respective structure-property-process relations. The microstructure development of the CsH 2 PO 4 materials was characterized for grain size, and dihedral angle distributions for a variety of the CSP processing conditions. The electrical properties of the cold sintered CsH 2 PO 4 were characterized through electrochemical impedance spectroscopy over a temperature range between 120 °C and 200 °C. The data suggests that the proton conductivity is 2.30 × 10−4 Scm-1 at 200 °C with good repeatability during cycled measurements. [ABSTRACT FROM AUTHOR]