Activation Energy For Proton Conduction Research Articles

Self-assembled Gd0.1Ce0.9O1.95-BaGd0.8La0.2Co2O6‒δ nanocomposite cathode for efficient protonic ceramic fuel cells

Protonic ceramic fuel cells (PCFCs) are characterized by a low activation energy for proton conduction and a high fuel utilization efficiency at low-to-intermediate temperatures. However, the sluggish oxygen reduction reaction kinetics on the cathodes drastically limit the power output performance of PCFCs. Herein, multiphase Gd0.1Ce0.9O1.95-BaGd0.8La0.2Co2O6‒δ (GDC-BGLC) nanocomposite cathodes are prepared by coupling self-assembly and sintering-free electrode construction methods. The nanocomposite cathode comprises mixed H+/e– conducting BGLC and O2− conducting GDC and BaCoO3 nanoparticles, and these phases are homogeneously mixed with coherent heterointerfaces. The nanocomposite cathode exhibits a significant increase in surface oxygen vacancies and three-phase boundaries, enhanced catalytic activity, and reduced activation energy for the oxygen reduction and water formation reactions. The results imply that the oxygen reduction and water formation reactions on the multiphase GDC-BGLC nanocomposite electrodes are most likely the dissociation, reduction and diffusion of oxygen species, which in turn is affected by the water vapor formed. An anode-supported single cell with the GDC-BGLC cathode exhibits a peak power density of 810 mW cm−2 at 700 °C with excellent operating stability at 650 °C for 110 h. This study provides a new strategy for the preparation of a high-performance and durable nanocomposite cathode for PCFCs.

Surface proton hopping conduction mechanism dominant polymer electrolytes created by self-assembly of bicontinuous cubic liquid crystals.

For the development of the next generation of fuel cells, it is essential to create an innovative design principle of polymer electrolytes that is beyond extension of the existing strategy. In the present study, we focused on the surface hopping proton conduction mechanism where an activation energy for proton conduction is greatly reduced by decreasing the distance between SO3- groups. Our gyroid nanostructured polymer film (Film-G), with a hydrophilic surface where the SO3- groups are aligned densely and precisely, shows high proton conductivity of the order of 10-2 S cm-1 when the water content is about 15 wt%. We reveal that the high proton conductivity of Film-G is attributed to the exhibition of an extremely-fast surface hopping conduction mechanism due to the reduced activation energy barrier along the gyroid minimal surface. This finding should introduce a game-changing novel opportunity in polymer electrolyte design.

High Performance Protonic Ceramic Electrochemical Cells Operating at

Protonic ceramic electrochemical cells (PCECs) can operate in both fuel cell and steam electrolysis modes for efficient power generation and green hydrogen production. Thanks to the low activation energy of proton conduction, PCECs are uniquely capable of operating at temperatures below 600°C. Although some intriguing demonstrations of intermediate-temperature (500-600°C) PCECs (IT-PCECs) have been made in the last decade, the operating temperature of PCECs is still too high to revolutionize ceramic electrochemical cell technology, which is ascribed to the high ohmic resistance and positive electrode polarization resistance. It has been also recognized the electrode polarization resistance dominates the total resistance at <500°C. These challenges suggest both the electrolyte and positive electrode should be redesigned to lower the PCEC operating temperature.In this work, we present two main approaches to reducing electrolyte ohmic resistance, electrolyte-positive electrode contact resistance, and electrode polarization resistance, which enables PCECs operation at <500°C. First, by using the ultrasonic spray coating system to coat the electrolyte layer on a negative electrode substrate with low Ba-deficiency, a bamboo-structured, ultrathin, and chemically homogeneous electrolyte can be fabricated. Second, a newly in-situ formed composite positive electrode was developed, which enhances the interfacial bonding between the positive electrode and electrolyte, further reducing ASRo , while improving both bulk oxygen-ion diffusion coefficient and surface oxygen exchange coefficientat <500°C.The newly developed LT-PCECs attain outstanding power densities in fuel cell mode (as high as 0.77 W cm-2 at 450°C), and exceptional current densities in electrolysis mode (over -1.28 A cm-2 at 1.4 V and 450°C). Furthermore, reducing the temperature does not sacrifice the fuel flexibility of these ceramic fuel cells. We demonstrated that the PCECs can directly utilize ammonia and methane for power generation at <500°C. Exceptional durability has been also demonstrated in both fuel cell and electrolysis modes at <500°C.These results further emphasize that through the PCEC scalable manufacturing processes and novel positive electrode materials presented here, PCECs can be employed for power generation and H2 production at <500°C, thereby transforming the architectures and removing previous operational constraints of ceramic electrochemical cells for scaled operation. PCECs can therefore be considered as one part of the growing hydrogen economy, while leveraging the existing fossil fuel infrastructure and achieving higher energy efficiency and lower CO2 emissions.

Proton conductivity of the azole composites based on BEA zeolites with different pore systems

There is a need for a stable and economical solid proton-conducting electrolyte capable of operating at elevated temperatures (>373 K), suitable for high-performance hydrogen fuel cells. In its search, imidazole (Im) or 1,2,4-triazole (Tri) is introduced into the channels of BEA zeolites with different porosity (i.e. the conventional microporous BEA (BEA-O) and two hierarchical materials with structural (BEA-C) or interparticle (BEA-TF) mesoporosity). The proton conductivity of obtained composites increases with increasing azole loading and temperature. The generation of mesopores in BEA zeolites leads to a decrease in the activation energy of proton conductivity in composites and favors the dispersion of a large amount of azoles. Zeolites with structural porosity (BEA-C) allow to introduce the highest amount of the azole molecules (0.29 wt% of imidazole), however the highest proton conductivity and the lowest activation energy is recorded for BEA-TF-0.25Im (σ = 5.86 × 10−4 S cm−1 at 393 K). A comparison of azole composites (with Im and Tri) of equal azole loadings shows that imidazole-containing materials exhibit significantly higher proton conductivity, regardless of the type of zeolite matrix.

Anhydrous Proton Conductivity in HAp-Collagen Composite

It is well known that a proton conductor is needed as an electrolyte of hydrogen fuel cells, which are attracting attention as an environmentally friendly next-generation device. In particular, anhydrous proton-conducting electrolytes are highly desired because of their advantages, such as high catalytic efficiency and the ability to operate at high temperatures, which will lead to the further development of fuel cells. In this study, we have investigated the proton-conducting properties of the hydroxyapatite (HAp)-collagen composite without external humidification conditions. It was found that, by injecting HAp into collagen, the electrical conductivity becomes higher than that of the HAp or the collagen. Moreover, the motional narrowing of the proton NMR line is observed above 130 °C. These results indicate that the electrical conductivity observed in the HAp-collagen composite is caused by mobile protons. Furthermore, we measured the proton conduction of HAp-collagen composite films with different HAp contents and investigated the necessity of the appearance of proton conductivity in HAp-collagen composites. HAp content (n = 0–0.38) is the number of HAp per collagen peptide representing Gly-Pro-Hyp. These results indicate that injection of HAp into collagen decreases the activation energy of proton conduction which becomes almost constant above a HAp content n of 0.3. It is deduced that the proton-conduction pathway in the HAp-collagen composite is fully formed above n = 0.3. Furthermore, these results indicate that the value of the activation energy of proton conductivity was lowered, accompanied by the formation of the HAp-collagen composite, and saturated at n &gt; 0.3. From these results, the HAp-collagen composite forms the proton-conduction pathway n &gt; 0.3 and becomes the proton conductor with no external humidification in the condition of n &gt; 0.3 above 130 °C.

Co-Exsolution Method Via Seeded Effect for Catalytically Active Anode in Protonic Ceramic Fuel Cells

Protonic ceramic fuel cells (PCFCs) have great potential in terms of reducing the operating temperature (400-600oC), because of the low activation energy of proton conduction in oxides compared to oxygen ion conduction. These characteristics provide a pathway to overcome the limitation of conventional SOFC (600-1000oC) such as durability, degradation of catalysts. However, poor catalyst activity at low operating temperatures still remains a problem to be solved. One promising way to improve catalytic activity is in-situ exsolution of various metal nanoparticles. Exsolved nanoparticles not only increase the active catalytic area but also have excellent resistance to thermal agglomeration and carbon coking. Unfortunately, it is difficult to achieve a high population density of metal nanoparticles due to the low exsolution kinetics (diffusion, nucleation) in the anode atmospheres of PCFC. In this study, we designed an A-site deficiency proton-conducting oxide, Ba0.9(Zr0.1Ce0.7Y0.1Yb0.1)0.95M0.05O3-d, as a host material to maximize exsolution behaviors. In addition, a co-exsolution strategy with Cu, which has the highest reducibility among transition metals, was introduced to achieve a high population density of exsolved atoms at low temperatures. A single doped Ni metal in the designed host material exhibited a population density value of 1.13 particles/um2 in reducing atmosphere at 600oC. The single doped Cu metal showed 24.1 particles/um2, but Co-doped with Ni and Cu metal produced the highest particle population of 98.31/um2, which is 87 times greater than a single Ni doping. These results follow the seeded growth mechanism induced by the additional surface energy of pre-exsolved Cu. This suggests a new synergy effect on exsolution phenomena that enhances segregation and nucleation kinetics Figure 1

Proton Conductivity Enhancement at High Temperature on Polybenzimidazole Membrane Electrolyte with Acid-Functionalized Graphene Oxide Fillers.

Graphene oxide (GO) and its acid-functionalized form are known to be effective in enhancing the proton transport properties of phosphoric-acid doped polybenzimidazole (PA-doped PBI) membranes utilized in high-temperature proton exchange membrane fuel cells (HTPEMFC) owing to the presence of proton-conducting functional groups. This work aims to provide a comparison between the different effects of GO with the sulfonated GO (SGO) and phosphonated GO (PGO) on the properties of PA-doped PBI, with emphasis given on proton conductivity to understand which functional groups are suitable for proton transfer under high temperature and anhydrous conditions. Each filler was synthesized following existing methods and introduced into PBI at loadings of 0.25, 0.5, and 1 wt.%. Characterizations were carried out on the overall thermal stability, acid doping level (ADL), dimensional swelling, and proton conductivity. SGO and PGO-containing PBI exhibit better conductivity than those with GO at 180 °C under anhydrous conditions, despite a slight reduction in ADL. PBI with 0.5 wt.% SGO exhibits the highest conductivity at 23.8 mS/cm, followed by PBI with 0.5 wt.% PGO at 19.6 mS/cm. However, the membrane with PGO required a smaller activation energy for proton conduction, thus less energy was needed to initiate fast proton transfer. Additionally, the PGO-containing membrane also displayed an advantage in its thermal stability aspect. Therefore, considering these properties, it is shown that PGO is a potential filler for improving PBI properties for HTPEMFC applications.

Origin of the Temperature Dependence of Proton Conductivity in Phosphate Glass Prepared by Alkali-Proton Substitution Technique

The temperature dependence of proton conductivity in 36HO1/2−4NbO5/2−2BaO-4LaO3/2−4GeO2−1BO3/2−49PO5/2 glasses prepared through the alkali-proton substitution method was investigated in this study. The activation energy of proton conduction, E a , was found to exhibit an non-Arrhenius type temperature dependence. The origin of the temperature dependence of the proton conductivity caused by thermal expansion of the glass structure was discussed in terms of the effect of changes in the local environment surrounding the protons. These changes were elucidated using Raman spectroscopy, 1H- and 31P-NMR, infrared spectroscopy, and molecular modeling. Because protons form O-H bonds, they are sensitive to changes in the distance between two oxygen atoms, which affects the strength of the hydrogen bond, and concluded that there is a temperature dependence as observed.

Synergistic effect of MOF-Directed acid-base pairs for enhanced proton conduction

Developing novel proton-conducting materials is crucial to improve the energy conversion performance of proton exchange membrane fuel cells, especially under the condition of low humidity. Metal-organic frameworks (MOFs) have expressed an apparent potential in proton conduction applications due to their orderly and tunable structure. Previous studies mainly focus on the MOFs modified with homogeneous functional groups to tune the proton conductivities. In this study, an acid-base pair synergistic strategy, namely introducing the acidic and basic groups into mix-linker MOF simultaneously to obtain acid-base coexistence materials, was firstly proposed to improve the proton conduction performance at 75% RH. Herein, 10 kinds of ML-UiO-66-(A)(B)-X were synthesized and the effects of content and ratio of acid-base pairs in MOF matrix on proton-conducting properties were studied. It was found that ML-UiO-66-(NH 2 )(SO 3 H)-5:5 possessed the highest proton conduction in the ML-UiO-66 materials, with the value of 2.8 × 10 -2 S·cm −1 at 353 K. In addition, at 303K, 75% RH, the proton conductivity of ML-UiO-66-(NH 2 )(SO 3 H)-5:5 reached 7.4 × 10 −3 S·cm −1 , which is three orders of magnitude higher than pristine UiO-66 (~980 times), two orders of magnitude higher than the base-functionalized UiO-66-NH 2 (~529 times) and about 218% higher than the acid-functionalized UiO-66-SO 3 H at 97% RH. The results show that at relatively lower humidity 75%, ML-UiO-66-(NH 2 )(SO 3 H)-5:5 has the better proton conductivity than other UiO-66 materials at nearly 100% RH. Meanwhile, ML-UiO-66-(NH 2 )(SO 3 H)-5:5 shows high water and thermal stability under high humidity and high temperature, which ensures its application in complex environment. Performance and mechanism studies show that the strategy of introducing acid-base pair into MOF matrix may open an avenue to design novel proton-conducting materials with excellent properties. UiO-66-directed ordered acid-base coexistence materials are prepared with the conductivity being 2.8 × 10 −2 S cm −1 at 353 K and 75% RH. • The proton conductivity of ML-UiO-66-(NH 2 )(SO 3 H)-5:5 is 2.8 × 10 −2 S cm −1 at 353 K, 75% RH. • The acid-base pairs in MOFs helps to reduce the activation energy of proton conduction. • The MOF-directed acid-base coexistence strategy is helpful to reduce the production cost and has high practical application value.

Performance Evaluation of Intermediate Temperature Proton-Conducting Soec with BaZr0.6Ce0.2Y0.2O3-δ Electrolyte

A solid oxide steam electrolysis cell (SOEC) has attracted much attention for the production of a clean H2 from water by using renewable electricity. Activation energy of proton conduction in proton conducting perovskite oxides BaZr x Ce1-x-y Y y O3-δ (BZCY) is much lower than that of yttria stabilized zirconia which is practically used for the high temperature SOECs [1]. Hence the cells using the proton conductors (H+-SOEC) are expected to operate at lower temperatures than that of YSZ-base SOEC. In general, the solid solutions, i.e. BaCe1−x−y Zr x M y O3-δ (M = Y, Yb etc.) tend to be more tolerant to CO2 and steam with increasing Zr contents [2], and thus the Zr-rich side BaCe1−x−y Zr x M y O3-δ are recently attractive as a practical electrolyte for H+-SOECs. However, the poor sinterability and relatively large grain-boundary resistances retards the application of Zr-rich phase to device application.In this study, we successfully fabricated the thin film electrolysis cells using Zr-rich side BaZr0.6Ce0.2Y0.2O3−δ (BZCY622) electrolytes. The cathode-supported cells were fabricated by a solid-state reactive sintering method assisted by zinc nitrate sintering additives. The cell comprises of a porous Ni-BZCY622 cermet cathode support, dense electrolyte film with a 20 mm thickness and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) porous anode. The cells with a 15 nm-thick interlayer of La0.5Sr0.5CoO3- δ (LSC) was also fabricated by sputtering deposition of LSC nanofilms on the surface of the electrolyte films before printing LSCF anodes. The cell with and without LSC yielded electrolysis currents of 420 and 200 mA cm-2, respectively, at 1.5 V cell bias at 600 ºC. EIS measurements confirmed that both polarization and ohmic resistances decreased with a use of LSC interlayer, which implies that LSC layer promotes proton transfer at the anode/electrolyte interface and thus reduce the proton transfer resistance and promote anode reactions. Y. Guo, R. Ran and Z. Shao, Int. J. Hydrogen Energy, 35, 5611, (2010). P. Sawant, S. Varma, B. N. Wani and S. R. Bharadwaj, Int. J. Hydrogen Energy, 37, 3848, (2012).

Tungstophosphoric acid-doped sulfonated poly(arylene ether nitriles) composite membranes with improved proton conductivity and excellent long-term stability

A series of composite membranes based on sulfonated poly(arylene ether nitriles) (SPEN) with embedded tungstophosphoric acid (TPA) were prepared. The effect of TPA concentration on morphology, structure, thermal stability, mechanical strength, ion-exchange capacity and proton conductivity of SPEN-TPA composite membranes was studied in detailed. SEM images indicated the TPA were uniformly distributed throughout the SPEN membranes matrix, which is due to the hydrogen bonding networks and the electrostatic interactions in the composites. The existence of hydrogen bonds was also confirmed by FTIR. Benefiting from these, the composite membranes showed higher IEC, mechanical strength, and higher water uptake compared to pristine SPEN. The proton conductivity of the SPEN-TPA composite membranes were dominated by the TPA concentration. The proton conductivity of SPEN-50TPA achieved the highest value of 0.107 S/cm at 80 °C, which is 4.4 times as high as that of pristine SPEN. Moreover, it also showed excellent long-term stability, as the TPA did not show any leakage after 120 h at 80 °C. Furthermore, activation energy of proton conductivity imply coexistence of Grotthuss and vehicle mechanisms in the composite membranes. These results indicate that SPEN-TPA composite membrane have great potential as proton exchange membrane with high performance.

Chemical modification of proton exchanger sulfonated polystyrene with sulfonated graphene oxide for application as a new polymer electrolyte membrane in direct methanol fuel cell

A novel composite membrane is prepared by the dispersion of sulfonated graphene oxide (SGO) in sulfonated polystyrene–polyethylene (SPS-PE) for electrolyte in direct methanol fuel cell. For sulfonated polystyrene used the method that patented by Makowski et al. Graphene oxide (GO) is prepared by modified Hummer's method and is further functionalized with SO3-H. SGO is then incorporated in SPS-PE matrix using solvent cast method to form composite membrane. The composite membranes are characterized by FT-IR, TGA and SEM. Oxidative resistance, water uptake, ionic conductivity and methanol permeability are measured to evaluate its performance in a direct methanol fuel cell with cation exchanger membrane. The membranes were confirmed to retain 1–5% water vapor at 80–140 °C in air due to the hydrophilic of highly SPS and SGO. The ionic conductivity and permeability of the membrane to methanol was found to increase with temperature increasing. The membrane SGO-SPS–PE shows the proton conductivity of 2.74 × 10-2 S cm-1 at 100 °C without extra humidity supply and is very promising for high temperature with low humidity. The high proton conductivity is ascribed to the unique composition in which the heterocyclic polymer provides the proton motion by construction diffusion and the highly SGO-SPS copolymer retains water vapor to lower the activation energy for proton conduction.

Dielectric properties of healthy and diabetic alloxan-induced lenses in rabbits

The dielectric properties of the eye lens were studied for healthy and alloxane-induced diabetic rabbits in the frequency range from 500 Hz to 100 kHz electric field and temperatures from 25 to 50 °C. In the full temperature range, the average relative permittivity and dielectric loss values for a healthy lens are lower than those recorded for diabetic tissue. Dielectric relaxation of polar amino acids on the alpha-crystallin surface with a characteristic frequency of 7 kHz in the range of 25–50 °C for healthy and diabetic samples is accompanied by the activation energy of proton conductivity with an average values of 33 and 39 kJ mol−1, respectively. The permittivity decrement, which characterizes the size of the dielectric dispersion with a central relaxation time of 0.023 ms for a diabetic sample, is more than twice as high as for a healthy sample. Measurements on the rabbit eye lens were carried out at ambient temperature above and below the physiological range, since these conditions provide an appropriate pattern of dielectric behavior for the diagnosis of clinical dysfunction of the human lens.

Organic-inorganic backbone with high contents of proton conducting groups: A newly designed high performance proton conductor

To prepare new high temperature organic-inorganic proton conductor for applications in proton exchange membrane fuel cells (PEMFC), 2,4,6-triphosphono-1,3,5-triazine (TPT) was synthesized and reacted with three different types of metal ions (Ce, Zr and Fe) in varied molar ratios. In each TPT molecule, three phosphonic acid groups were introduced into the triazine ring to obtain an organic compound with high content of proton conducting groups, which was then reacted with metal ions to ensure the insolubility in water aiming to avoid leaking during PEMFC operation. CeTPT(1:2) exhibited good thermal stability up to 200 °C and showed crystalline phase. MTPT exhibited high ion exchange capacity (IEC, 1.53–2.12 meq. g−1). CeTPT(1:2) exhibited highest proton conductivity among all samples, which reached 0.116, 0.070 and 0.034 S cm−1 at 100% relative humidity (RH), 50% RH and anhydrous conditions at 180 °C, respectively. The corresponding activation energy for proton conduction was 14.5, 16.0 and 21.5 kJ mol−1 at 100% RH, 50% RH and anhydrous conditions, respectively. The mechanism for proton conduction was proposed according to the activation energy. The proton conductor can find promising applications in fuel cells, corrosion inhibition and water desalination due to its good thermal stability and high IEC.

Thickness Dependence Impact on Proton Transport Proton Properties of Nafion® Thin-Film on Platinum Model Electrode

Introduction Improving oxygen reduction reaction (ORR) activity of cathode catalyst is required for wide spread of polymer electrolyte fuel cells. Because ORR occurs at the three-phase-boundary among the cathode catalyst, ionomer and oxygen gas, understanding the impact the ionomer on the cathode catalyst is important to achieve the high performance PEFCs. Especially, the structure of the ionomer on the cathode is strongly influenced by humidity, thickness, annealing treatment [1-3]. In this study, we examined the proton conductivity the Nafion® thin-film with various thickness from 5 to 200 nm. The correlation between structure and proton conductivity of the Nafion on Pt electrode was discussed. Experimental For proton conductivity measurements, Nafion thin-films were prepared on interdigitated array of gold electrodes on SiO2 substrate by soaking the electrode on Nafion dispersion. For GISAXS measurements, Nafion thin-films were prepared on Pt sputtered P doped-silicon substrates by spin casting of Nafion dispersion. Proton conductivity under humidity was measured by applying an alternating potential of amplitude 100 mV over a frequency 7 MHz to 0.01 Hz. GISAXS measurements were performed under humidity in beamline BL40B2 at SPring-8, Japan. Results and Discussion In the Nafion thin-films with thickness more than 50 nm, EIS results indicated that the hydrophilic domains grew gradually as the thickness increases. In contrast, the hydrophilic domains, which works as the protonic path, grows larger with increase of the thickness, leading to reduce the activation energy of proton conductivity. According to GISAXS, the hydrophilic domain disappears in the Nafion thin-film with thickness less than 50 nm. These results indicate that the structure of Nafion thin-film drastically changes with the thickness. It is anticipated that the proton conductivity of the in-plane in the Nafion film is larger than that of the out-of-plane because the hydrophilic domain of the in-plane grows larger than that of the out-of-plane. The anisotropy of the ordered structure in the Nafion thin-film is enhanced by the interaction between the ionomer and substrate. These results indicate that the proton conductivity in the Nafion is largely influenced by the amount of the hydrophobic domain. Acknowledgments This research is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Reference: [1] A. Kusoglu, D. Kushner, D. K. Paul, D. Karan, M. Hickner, A. Weber, Adv. Funct. Mater., 24, 4763 (2014) [2] D. K. Paul, H. K. Shim, J. B. Giorgi, K. Karan, J. Polym. Sci. B Polym. Phys., 54, 1267 (2016) [3] D. K. Paul, R. McCreery, K. Karan, J. Electrochem. Soc., 161, F1395 (2014)

Designing UiO-66-Based Superprotonic Conductor with the Highest Metal-Organic Framework Based Proton Conductivity.

Metal-organic framework (MOF) based proton conductors have received immense importance recently. The present study endeavors to design two post synthetically modified UiO-66-based MOFs and examines the effects of their structural differences on their proton conductivity. UiO-66-NH2 is modified by reaction with sultones to prepare two homologous compounds, that is, PSM 1 and PSM 2, with SO3H functionalization in comparable extent (Zr:S = 2:1) in both. However, the pendant alkyl chain holding the -SO3H group is of different length. PSM 2 has longer alkyl chain attachment than PSM 1. This difference in the length of side arms results in a huge difference in proton conductivity of the two compounds. PSM 1 is observed to have the highest MOF-based proton conductivity (1.64 × 10-1 S cm-1) at 80 °C, which is comparable to commercially available Nafion, while PSM 2 shows significantly lower conductivity (4.6 × 10-3 S cm-1). Again, the activation energy for proton conduction is one of the lowest among all MOF-based proton conductors in the case of PSM 1, while PSM 2 requires larger activation energy (almost 3 times). This profound effect of variation of the chain length of the side arm by one carbon atom in the case of PSM 1 and PSM 2 was rather surprising and never documented before. This effect of the length of the side arm can be very useful to understand the proton conduction mechanism of MOF-based compounds and also to design better proton conductors. Besides, PSM 1 showed proton conductivity as high as 1.64 × 10-1 S cm-1 at 80 °C, which is the highest reported value to date among all MOF-based systems. The lability of the -SO3H proton of the post synthetically modified UiO-66 MOFs has theoretically been determined by molecular electrostatic potential analysis and theoretical p Ka calculation of models of functional sites along with relevant NBO analyses.

Humidity-triggered single-crystal-to-single-crystal structural transformations in a Zn(ii) coordination polymer displaying unusual activation energy change in proton conductivity.

Single-crystal-to-single crystal structural conversions occur in a Zn(ii) coordination polymer, uniquely induced by fine-tuned relative humidity. Proton conductivity depends on the number of hydrogen bonds in the structures. Slope change in the Arrhenius plot is uncommon among coordination-based conductors and associated with temperature-dependent phase changes.

Hybrid electrolyte SiW9MoV2/rGO/SPEEK for solid supercapacitors with enhanced conductive performance

To improve the proton conductive performance of heteropoly acids, a novel proton-conducting hybrid electrolyte SiW9MoV2/rGO/SPEEK was prepared by a simple and effective method based on sulfonated polyether ether ketone (SPEEK), H6SiW9MoV2O40 (SiW9MoV2) and reduced graphene oxide (rGO) in this work. This hybrid material was characterized by IR, TEM and XRD. Electrochemical impedance spectroscopy shows the obtained SiW9MoV2/rGO/SPEEK electrolyte exhibits an appreciable proton conductivity of 1.07 × 10−2 S cm−1 at 16 °C and 70% relative humidity, which increases with higher temperature, and the activation energy for proton conduction of this hybrid film is 17.82 kJ mol−1. The proton conduction is speculated to be the mixing of Grotthuss mechanism and Vehicle mechanism that accelerate the proton mobility in the hybrid electrolyte. This work lays a foundation in the field of HPAs-based separator films for proton exchange membrane devices and solid supercapacitors.

Proton Conductivity and Thermal Properties of Ba(H2PO4)2

We have grown single crystals of barium dihydrogen phosphate and studied its thermal transformations during heating to 500°C and its electrotransport properties. Ba(H2PO4)2 (Pccn) has been shown to undergo no phase transitions up to its dehydration temperature. The thermal decomposition of Ba(H2PO4)2, accompanied by dehydration, involves two steps, with maximum rates at ~265 and 370°C, and results in the formation of barium dihydrogen pyrophosphate and barium metaphosphate, respectively. The total enthalpy of the endothermic dehydration events is–244.6 J/g. Using impedance spectroscopy, we have studied in detail the proton conductivity of polycrystalline and single-crystal Ba(H2PO4)2 samples in a controlled atmosphere. Adsorbed water has been shown to have a significant effect on the proton conductivity of Ba(H2PO4)2 up to 130°C. The proton conductivity of the Ba(H2PO4)2 single crystals has been shown to be anisotropic. The conductivity anisotropy correlates with specific structural features of the salt. Higher conductivity values, 3 × 10–9 to 2 × 10–7 S/cm in the range 60–160°C, have been observed in the [100] crystallographic direction, exceeding the conductivity along [010] by an order of magnitude. The activation energy for proton conduction is 0.80 eV.

Influence of Cathode Porosity on High Performance Protonic Ceramic Fuel Cells with PrBa0.5Sr0.5Co1.5Fe0.5O5-δ Cathode

Protonic ceramic fuel cells (PCFCs) are attractive energy conversion systems at intermediate operating temperatures (500–650°C) because of the low activation energy for proton conduction. Despite this advantage, the efficient operation of PCFCs is still limited partly due to the large cathodic polarization resistance. To decrease the large cathodic polarization, the modification of cathode microstructure could be an effective way because the PCFC cathode microstructure requires both sufficient pathways for oxygen supply and water vapor removal, along with a large surface area for electrochemical reactions. Herein, the correlation between the cathode microstructure and the electrochemical performance is investigated based on BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) electrolyte under the PCFC operating condition at 650°C. Four cells with PrBa0.5Sr0.5Co1.5Fe0.5O5-δ (PBSCF) cathode of different porosity with identical anode/electrolyte configuration were fabricated and tested. Interestingly, the modification of cathode porosity effectively decreases the cathodic polarization resistance from 0.077 to 0.048 Ω cm2 at 650°C, and the corresponding maximum power density of PCFCs is improved from 1.23 to 1.62 W cm− 2. The influence of other microstructural factors such as grain size, specific surface area (per volume), and porosity in the cathode should be studied to fully understand the impacts of microstructure on the cathode performance of PCFC.