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Osteoarthritis scaffold-based grafts fail because of poor integration with the surrounding soft tissue and inadequate tribological properties. To circumvent this, we propose electrospun poly(ε-caprolactone)/zein-based scaffolds owing to their biomimetic capabilities. The scaffold surfaces were characterized using Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, static water contact angles, and profilometry. Scaffold biocompatibility properties were assessed by measuring protein adsorption (Bicinchoninic Acid Assay), cell spreading (stained F-actin), and metabolic activity (PrestoBlue™ Cell Viability Reagent) of primary bovine chondrocytes. The data show that zein surface segregation in the membranes not only completely changed the hydrophobic behavior of the materials, but also increased the cell yield and metabolic activity on the scaffolds. The surface segregation is verified by the infrared peak at 1658 cm−1, along with the presence and increase in N1 content in the survey XPS. This observation could explain the decrease in the water contact angles from 125° to approximately 60° in zein-comprised materials and the decrease in the protein adsorption of both bovine serum albumin and synovial fluid by half. Surface nano roughness in the PCL/zein samples additionally benefited the radial spreading of bovine chondrocytes. This study showed that co-electrospun PCL/zein scaffolds have promising surface and biocompatibility properties for use in articular-tissue-engineering applications.

The grafting of an iridium-aluminium precursor onto silica followed by thermal treatment under H2 yields small (

Perovskite oxides have been at the forefront among catalysts for the oxygen evolution reaction (OER) in alkaline media offering a higher degree of freedom in cation arrangement. Several highly OER active Co-based perovskites have been known to show extraordinary activities and stabilities when the B-site is partially occupied by Fe. At the current stage, the role of Fe in enhancing the OER activity and stability is still unclear. In order to elucidate the roles of Co and Fe in the OER mechanism of cubic perovskites, two prospective perovskite oxides, La0.2Sr0.8Co1- xFexO3-δ and Ba0.5Sr0.5Co1-xFexO3-δ with x = 0 and 0.2, were prepared by flame spray synthesis as nanoparticles. This study highlights the importance of Fe in order to achieve high OER activity and stability by drawing relations between their physicochemical and electrochemical properties. Ex situ and operando X-ray absorption spectroscopy (XAS) was used to study the local electronic and geometric structure under oxygen evolving conditions. In parallel, density function theory computational studies were conducted to provide theoretical insights into our findings. Our findings show that the incorporation of Fe into Co-based perovskite oxides alters intrinsic properties rendering efficient OER activity and prolonged stability.

IrO2 is the state-of-art O2-evolution reaction (OER) electrocatalyst implemented in proton exchange membrane electrolyzers, but in the near future iridium's ultra-low availability could threaten the successful development of this technology. To minimize this dependency, Ir-oxides with enhanced mass-specific surface areas and OER-activities are progressively being developed, but often suffer from a poorly understood deactivation under operating conditions. To understand this activity loss, in this study we used a modified Adams’ fusion method to produce an Ir-oxide with a surface area of ≈350 m2 g−1 that consists of nano-disks with their surface partially covered by a layer of Ir(OOH). In order to investigate the effect of this surface oxidation state on the catalyst's reactivity and stability, a fraction of this as-synthetized sample was submitted to a second heat-treatment in air to further oxidize its surface (i.e., yielding IrO2 with ≈250 m2 g−1). While electrochemical characterization through rotating disk electrode voltammetry unveiled that the as-synthesized catalyst features a ≈2-fold larger surface-specific OER-activity than its heat-treated derivative, it also undergoes a greater loss of such activity in the course of an accelerated stress test (AST) that mimics electrolyzer startup/shutdown (≈45 vs. ≈30% OER-current decrease for the as-synthetized sample vs. its heat-treated derivative, respectively). Since ex situ analyses (e.g., through X-ray photoelectron spectroscopy) were not sufficient to explain this difference in stability, the operando changes in the samples' morphology and chemical composition were assessed using a recently developed apparatus that combines small angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS). While the XAS measurements demonstrated the compositional stability of both catalysts (i.e., oxidation state and local geometric structure), SAXS showed that the as-synthetized catalyst is made of two-dimensionally agglomerated disks that become thinner and wider in the course of the AST, whereas the heat-treated sample is composed of morphologically stable, sintered particles in the form of rough and porous agglomerates. Considering the complementary information provided by these operando and ex situ techniques, it was then possible to quantify the contributions of Ir-dissolution, surface area loss and changes in the surface oxidation state to the destabilization of both catalysts.

Pyrochlore oxides (A2B2O7 ) simultaneously containing iridium and ruthenium in the B-site are promising catalysts for oxygen evolution reaction (OER) in acid media. The catalytic activity of the pyrochlore basedcatalysts is increased by the coexistence of Ir and Ru in the B-site of the pyrochlore structure. Lanthanide(Yb, Gd, or Nd) stabilized mixed pyrochlores with a fraction of Ru in the B-site of x Ru = 0.2, 0.4, 0.6, 0.8were synthesized by the spray-freeze freeze-dry approach. All prepared mixed pyrochlore catalysts aresurpassing the OER activity of the corresponding iridium and ruthenium analogues featuring no cationmixing as well as that of the benchmark IrO2 catalyst. The synergy of Ir and Ru in the B-site of thepyrochlore structure suppresses the effect of the A-site cation radius on the OER activity. The observedOER activity scales with the Ir-Ru bond distance which represents the local structure of the preparedmaterials. The most active ytterbium catalyst also shows a significant stability improvement under OERoperando conditions over the benchmark IrO2&nbsp

The members of the perovskite oxide family have been vastly explored for their potential as active electrocatalysts for an efficient anodic reaction (i.e. the oxygen evolution reaction, OER) of the water splitting process. Therefore, restless effort has been invested in the development of perovskite oxides as efficient OER catalysts, while the OER mechanism is still in veil. The rational development of perovskite catalysts for practical water electrolysis is left on hold until the full comprehension of the underlying mechanism is established under real operation conditions. Up to date, primarily two different OER mechanisms - conventional and lattice oxygen evolution - have been conjectured where the former follows a reversible route while the latter leads to irreversible changes. In this present study, we present evidence which suggests that perovskite catalysts follow both mechanisms concomitantly while one is preferentially selected based on their thermodynamic and kinetic natures dependent on pH., Materials Advances, 2 (1), ISSN:2633-5409

In the last two decades, small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS) have evolved into two well-established techniques capable of providing complementary and operando information about a sample’s morphology and composition, respectively. Considering that operation conditions can often lead to simultaneous and related changes in a catalyst’s speciation and shape, herein we introduce a setup that combines SAXS and XAS in a configuration that allows optimum acquisition and corresponding data quality for both techniques. To determine the reliability of this setup, the latter was used to study the operando degradation of two carbon-supported Pt-nanoparticle (Pt/C) catalysts customarily used in polymer electrolyte fuel cells. The model used for the fitting of the SAXS curves unveiled the fractal nature of the Pt/C-electrodes and their evolution during the operando tests, and both X-ray techniques were complemented with control, ex situ transmission electron microscopy, and standa...

Mixed Ni–Fe metal oxides currently represent some of the most attractive anode catalysts for the electrochemical splitting of water in alkaline electrolyte due to their low overpotentials for the oxygen evolution reaction (OER). Here we employ a practical and scalable liquid-feed flame-spray synthesis capable of producing highly crystalline Ni–Fe oxide (Ni1−xFexOy) nanoparticles with high specific surface areas (SABET ≈ 20–75 m2 g−1). The work presented herein focuses on expanding the current understanding of how Fe incorporation influences the surface electronic and local coordination structures of Ni1−xFexOy and how this impacts the electrochemical stability and OER activity. The resulting operando XANES and EXAFS analyses at the Ni and Fe K-edges permit useful insight into the nature of the valence states and the rearrangements in local structure that occur under operating conditions representative of alkaline water electrolysis. Specifically, we show that the incorporation of Fe greatly stabilizes the Ni electronic and local coordination environment under OER conditions. Combined with electrochemical measurements, we find that the incorporation of Fe leads to an overall stabilization of the initially compact and crystalline rock salt structure of Ni1−xFexOy and thereby inhibits the transformation to more layered and disordered polymorphs (e.g. β/γ-Ni1−xFexOOH).

Summary The development of electrocatalysts for the electrochemical splitting of water is of high importance in order to meet the energy storage demands imposed by the growth of intermittent renewable energy sources. In situ/operando X-ray absorption spectroscopy (XAS) is a powerful technique with the potential of revealing the electronic and geometric structure of nanoparticulate electrocatalyst systems under gas-evolving conditions, thereby providing vital insight into the nature of the catalytic active site in the oxygen evolution reaction (OER) on oxide-based electrocatalysts. This article provides an overview detailing the recent applications of operando XAS as applied to the OER for state-of-the-art acid membrane and alkaline electrolyte systems. In doing so, we portray the fundamental studies that have assisted in the identification of key reactive species participating in the OER for IrO2-based acidic electrolyte systems and those that have aided in elucidating the role of Fe in Fe–Ni oxide alkaline electrolyte systems.

The utilization and development of efficient water electrolyzers for hydrogen production is currently limited due to the sluggish kinetics of the anodic process—the oxygen evolution reaction (OER). Moreover, state of the art OER catalysts contain high amounts of expensive and low-abundance noble metals such as Ru and Ir, limiting their large-scale industrial utilization. Therefore, the development of low-cost, highly active, and stable OER catalysts is a key requirement toward the implementation of a hydrogen-based economy. We have developed a synthetic approach to high-surface-area chlorine-free iridium oxide nanoparticles dispersed in titania (IrO2-TiO2), which is a highly active and stable OER catalyst in acidic media. IrO2-TiO2 was prepared in one step in molten NaNO3 (Adams fusion method) and consists of ca. 1–2 nm IrO2 particles distributed in a matrix of titania nanoparticles with an overall surface area of 245 m2 g–1. This material contains 40 molM % of iridium and demonstrates improved OER activi...

Mixed transitionmetal nickel oxide materials (M-NiO; M=Co, Mn, Fe) supported on silicone nanofilaments (SNFs) were synthesized via precipitation reaction with urea. All materials were evaluated for their OER activity in 0.1 M KOH, of which the Fe-NiO/SNFs showed a notable improvement over NiO/SNFs and unsupported NiO. The results presented herein demonstrate the extension of our previously reported synthesis for NiO/SNFs to yield SNF-supported mixed transition metal-oxide materials. The versatility and scalability of the synthesis are particularly interesting for the facile preparation of three-dimensional, binderless electrodes for alkaline water electrolysis applications.

Density Functional Theory (DFT) has proven to be an invaluable and effective tool for identifying highly active electrocatalysts for the oxygen evolution reaction (OER). Herein we take a computational approach in order to first identify a series of rare-earth pyrochlore oxides based on Ir and Ru as potential OER catalysts. The DFT-based phase diagrams, Pourbaix diagrams (E vs. pH), projected density of states (PDOS), and band energy diagrams were used to identify prospective OER catalysts based on rare earth Ir and Ru pyrochlores. The predicted materials were synthesized using the spray-freeze freeze-drying approach to afford nanoparticulate oxides conforming to the pyrochlore structural type A2B2O7 where A = Nd, Gd, or Yb and B = Ir or Ru. In agreement with the computed Pourbaix diagrams, the materials were found to be moderately stable under OER conditions. All prepared materials show higher stability as compared to the benchmark IrO2 catalyst and the OER mass activity of Yb2Ir2O7 and the ruthenate pyrochlores (Nd2Ru2O7, Gd2Ru2O7, and Yb2Ru2O7) were also found to exceed that of the benchmark IrO2 catalyst. We find that the OER activity of each pyrochlore series (i.e. iridate or ruthenate) generally improves as the size of the A-site cation decreases, indicating that maintaining control over the local structure can be used to influence the electrocatalytic properties.

A current challenge faced in water electrolysis is the development of structure–activity relationships for understanding and improving IrOx-based catalysts for the oxygen evolution reaction (OER). We report a simple and scalable modified Adams fusion method for preparing highly OER active, chlorine–free iridium oxide nanoparticles of various size and shape. The applied approach allows for the effects of particle size, morphology, and the nature of the surface species on the OER activity of IrO2 to be investigated. Iridium oxide synthesized at 350 °C from Ir(acac)3, consisting of 1.7 ± 0.4 nm particles with a specific surface area of 150 m2 g–1, shows the highest OER activity (E = 1.499 ± 0.003 V at 10 A gox–1). Operando X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) studies indicate the presence of iridium hydroxo (Ir–OH) surface species, which are strongly linked to the OER activity. Preparation of larger IrO2 particles using higher temperatures results in a change of the ...

An electrochemical three-electrode flow-cell is presented for in situ small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS) experiments in transmission mode at synchrotron X-ray sources. The cell also allows for in situ XAS performed in fluorescence mode. Constant experimental conditions, even under moderate gas evolution, are provided by the electrolyte flow with controlled gas saturation. A special configuration of working and counter electrode, respectively, yields low residual ohmic resistance in three-electrode measurements that enables the study of thick porous electrodes of active high surface area materials. The cell proved its functionality and reliability in two studies: First, an in situ anomalous SAXS experiment for the high-potential degradation properties of a Pt/IrO2-TiO2 catalyst for the oxygen reduction reaction at polymer electrolyte fuel cell cathodes; and second, an in situ XAS study of the electronic state of Ir centers inside an IrO2-TiO2 catalyst under oxygen evolution conditions., Journal of the Electrochemical Society, 163 (10), ISSN:0013-4651, ISSN:1945-7111

Nanocrystalline ruthenium dioxide and doped ruthenia of the composition Ru1−xMxO2 (M = Co, Ni, Zn) with 0 ≤ x ≤ 0.2 were prepared by the spray-freezing freeze-drying technique. The oxygen reduction activity and selectivity of the prepared materials were evaluated in alkaline media using the RRDE methodology. All ruthenium based oxides show a strong preference for a 2-electron oxygen reduction pathway at low overpotentials. The catalysts' selectivity shifts towards the 4-electron reduction pathway at high overpotentials (i.e. at potentials below 0.4 V vs. RHE). This trend is particularly noticeable on non-doped and Zn-doped catalysts; the materials containing Ni and Co produce a significant fraction of hydrogen peroxide even at high overpotentials. The suppression of the 4-electron reduction pathway on Ni and Co-doped catalysts can be accounted for by the presence of the Ni and Co cations in the cus binding sites as shown by the DFT-based analyses on non-doped and doped catalysts.

Nanocrystalline Mg-doped ruthenium dioxide catalysts with the formula Ru1-xMgxO2 (0 ≤ x ≤ 20) were synthesized by the spray-freezing freeze-drying technique. Synthesized materials are of nanoparticulate nature and show a single phase diffraction pattern conforming to a tetragonal oxide of the rutile structural type. Magnesium ions are not distributed homogeneously in the material, but exist in Mg-rich clusters as shown by X-ray absorption spectroscopy. The refinement of the Mg EXAFS functions for materials with low Mg content shows that the magnesium rich clusters contain Mg in a highly strained environment similar to that of the rutile-type structure. The Mg environment shifts to an ilmenite-type inclusion when Mg occupies more than 10% of all cationic positions. All Mg modified materials are active in oxygen evolution and chlorine evolution reactions. Although the Mg containing catalysts show lower overall activities compared with the non-doped ruthenia, they feature enhanced selectivity toward the chlorine evolution process, which is attributed primarily to the opening of a reaction pathway for chlorine evolution associated with presence of Mg modified active sites.

Development of proton exchange membrane fuel cells, have to be tempered with the cost, a significant portion of which is due to the so called ‘stability criterion’ restricting the choice to Pt and Pt alloy materials.Fuelcellsoperating inalkaline media havepotential advantage of facile kinetics of oxygen reduction reaction on non-precious group metals and stability at high pH values. In addition, the hydrodynamics of alkaline membrane fuel cells is potentially beneficial considering the problems associated with water management in a conventional PEM fuel cell. Further, highly stable PTFE based membranes are not required under alkaline conditions as the membranes are less prone to attack by peroxide ions. Even though AEMFCs alleviate most of the hurdles associated with PEM fuel cells, state of art performance of H2/air does not exceed half of the performance shown by H2 fed PEM fuel cells using Pt based catalysts (compare 700 mW cm −2 for PEMFCs 1 at 0.65 V

It is shown that producing PrBaCo2O5 and Ba0.5Sr0.5Co0.8Fe0.2O3 nanoparticle by a scalable synthesis method leads to high mass activities for the oxygen evolution reaction with outstanding improvements by 10 and 50 times, respectively, compared to those prepared via the state of the art synthesis method. Here, detailed comparisons at both laboratory and industrial scales show that Ba0.5Sr0.5Co0.8Fe0.2O3 appears to be the most active and stable perovskite catalyst under alkaline conditions, while PrBaCo2O6 reveals thermodynamic instability described by the density functional theory based Pourbaix diagrams highlighting cation dissolution under oxygen evolution conditions. Operando Xray absorption spectroscopy is used in parallel to monitor electronic and structural changes of the catalysts during oxygen evolution reaction. The exceptional BSCF functional stability can be correlated to its thermodynamic metastability under oxygen evolution conditions as highlighted by Pourbaix diagram analysis. BSCF is able to dynamically self reconstruct its surface, leading to formation of Co based oxyhydroxide layers while retaining its structural stability. Differently, PBCO demonstrates a high initial oxygen evolution reaction activity while it undergoes a degradation process considering its thermodynamic instability under oxygen evolution conditions as anticipated by its Pourbaix diagram. Overall, this work demonstrates a synergetic approach of using both experimental and theoretical studies to understand the behavior of perovskite catalysts.

The perovskite oxides with general structure formula of ABO3 have been at the forefront among catalysts for the oxygen evolution reaction (OER) in alkaline media offering a higher degree of freedom in cation arrangement. From its ability to partially accommodate foreign cations (i.e. A’ and B’) of different oxidation states, which then alters the original oxidation state of the B-site cation and the content of oxygen vacancies, correlations can be drawn between physicochemical properties and catalytic performance.1 Particularly, Ba0.5Sr0.5Co0.8Fe0.2O2+ δ (BSCF) has been demonstrated an exceptional activity towards OER,2-6 and recent studies have taken advantages of operando characterization techniques in order to relate changes in its electronic and geometric structure to the OER process.2 These studies have identified the formation of a dynamic self-assembled surface oxy(hydroxide) layer of B-site cations (i.e. Co/Fe for BSCF), which is the result of the lattice oxygen evolution reaction (LOER), as the key feature to obtain a higher OER activity.2, 7-8 In addition, the partial occupancy of Fe at the B-site of BSCF has shown favorable effects in its performance.2 Yet, the functional role of Fe with respect to OER activities and stabilities of Co-based perovskite oxides is still left to be answered. Therefore, in this study, we elucidate the roles of Fe in the OER mechanism of Co-based cubic perovskite oxides; two prospective perovskite oxides – La0.2Sr0.8Co0.8-xFexO3 and Ba0.5Sr0.5Co0.8-xFexO2+ δ with x = 0 and 0.2 – were prepared by flame spray synthesis as nanoparticles. Ex situ and operando X-ray absorption spectroscopy (XAS) was used to study the local electronic and geometric structure under oxygen evolving conditions. In parallel, density function theory (DFT) computational studies were conducted to provide theoretical insights into our findings. Overall, the gathered results highlight the synergetic role of Fe such that Fe would help to stabilize the cobalt in a lower oxidation state leading to allow a greater oxygen vacancy content. In this regard, the dynamic growth of the active (oxy)hydroxide species is inhibited in the absence of Fe for these Co-based perovskites (see Figure 1). Therefore, Fe ultimately contributes to attain a higher OER activity and stability of perovskite catalysts. Overall, information gathered from this study takes another step to understanding the physicochemical properties of perovskite oxides as oxygen evolution reaction catalysts. References Zhu, J.; Li, H.; Zhong, L.; Xiao, P.; Xu, X.; Yang, X.; Zhao, Z.; Li, J., Perovskite Oxides: Preparation, Characterizations, and Applications in Heterogeneous Catalysis. ACS Catalysis 2014, 4 (9), 2917-2940. Fabbri, E.; Nachtegaal, M.; Binninger, T.; Cheng, X.; Kim, B. J.; Durst, J.; Bozza, F.; Graule, T.; Schaublin, R.; Wiles, L.; Pertoso, M.; Danilovic, N.; Ayers, K. E.; Schmidt, T. J., Dynamic surface self-reconstruction is the key of highly active perovskite nano-electrocatalysts for water splitting. Nat. Mater. 2017, 16 (9), 925-+. Cheng, X.; Fabbri, E.; Kim, B.; Nachtegaal, M.; Schmidt, T. J., Effect of ball milling on the electrocatalytic activity of Ba0.5Sr0.5Co0.8Fe0.2O3 towards the oxygen evolution reaction. J. Mater. Chem. A 2017, 5 (25), 13130-13137. Suntivich, J.; May, K. J.; Gasteiger, H. A.; Goodenough, J. B.; Shao-Horn, Y., A Perovskite Oxide Optimized for Oxygen Evolution Catalysis from Molecular Orbital Principles. Science 2011, 334 (6061), 1383-1385. Fabbri, E.; Nachtegaal, M.; Cheng, X.; Schmidt, T. J., Superior Bifunctional Electrocatalytic Activity of Ba0.5Sr0.5Co0.8Fe0.2O3-/Carbon Composite Electrodes: Insight into the Local Electronic Structure. Adv. Energy Mater. 2015, 5 (17). Fabbri, E.; Habereder, A.; Waltar, K.; Kotz, R.; Schmidt, T. J., Developments and perspectives of oxide-based catalysts for the oxygen evolution reaction. Catal. Sci. Technol. 2014, 4 (11), 3800-3821. Burke, M. S.; Kast, M. G.; Trotochaud, L.; Smith, A. M.; Boettcher, S. W., Cobalt-Iron (Oxy)hydroxide Oxygen Evolution Electrocatalysts: The Role of Structure and Composition on Activity, Stability, and Mechanism. J. Am. Chem. Soc. 2015, 137 (10), 3638-3648. Burke, M. S.; Enman, L. J.; Batchellor, A. S.; Zou, S. H.; Boettcher, S. W., Oxygen Evolution Reaction Electrocatalysis on Transition Metal Oxides and (Oxy)hydroxides: Activity Trends and Design Principles. Chem. Mater. 2015, 27 (22), 7549-7558. Figure 1. Illustration of difference in OER mechanisms of BSC and BSCF; For BSC, the presence of native CoO(OH) perturbs the growth of self-assembled CoO(OH), while BSCF promotes dynamic growth of self-assembled CoO(OH) to attain a high OER activity Figure 1

Mixed Ni-Fe metal oxides currently represent some of the most attractive anode catalysts for the electrochemical splitting of water due to their low overpotentials for the oxygen evolution reaction (OER) in alkaline electrolytes. The concentrated potassium hydroxide solutions and anion exchange membranes that are typically employed in alkaline water electrolyzers, however, are prone to carbonation which can lead to significant shifts in the electrolyte pH from alkaline to quasi-neutral conditions (pH = 7-10). So far a fundamental understanding of how changes in the local pH environment induced via carbonation affect the catalyst electronic and surface structure, and ultimately the catalyst stability and electrochemical OER activity, is lacking. The importance of understanding this behavior is further highlighted by the potential application of Ni-Fe oxides as anode catalysts in co-electrolysis, where the electrochemical reduction of CO2 and the anodic evolution of oxygen occur in a carbonated, quasi-neutral pH environment. Here we demonstrate a practical and scalable flame-spray pyrolysis synthesis capable of producing highly crystalline Ni-Fe oxide (Ni1-xFexOy) nanoparticles with high surface areas (SABET ≈ 20 - 75 m2/g). The research presented herein focuses on expanding the current understanding of the influence of the local electronic and surface structures on the OER activity and electrochemical stability in both alkaline (pH = 13) and carbonated, quasi-neutral (pH = 9) electrolyte. The resulting operando XANES and EXAFS analyses of the Ni and Fe K-edges permit useful insight into the nature of the valence states and rearrangements in local structure that occur under operating conditions representative of alkaline water electrolysis and co-electrolysis. Combined with a broad range of ex situ physical characterization techniques, we then relate the structural, electronic, and morphological changes to the observed electrochemical OER activity and stability.

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In this study, the performance of the anionic electrodes in polymer-based alkaline fuel cells is analyzed. Direct alcohol, alkaline fuel cells suffer from a rapid decrease in cell potential at low discharge currents. Several effects are described to account for this drop in cell potential. Quaternary ammonium ions can specifically adsorb on the catalyst surface decreasing the active surface area and lowering the rate of methanol oxidation. In addition, the tethering of the quaternary ammonium cations on the polymer electrolyte inhibits the cation mobility causing a diffuse double layer to be formed. The diffuse double layer electrostatically inhibits the migration of hydroxide to the surface of the electrode which is needed for alcohol oxidation.

Paper describes synthesis, structural characterization and electrocatalytic activity of cubic pyrochlores featuring lanthanide (Yb, Gd and Nd) in the A site and Ru or Ir in the B site. The resulting catalytic activity correlates with the unit cell parameter of the catalysts which is in agreement withdband center theorem.

Extensive investigations in understanding the functional mechanisms of metal oxides behind oxygen evolution have been carried out since an electrolyzer has demonstrated promising possibilities as a device to produce hydrogen for electrochemical energy conversion systems. In particular, perovskite oxides are reputable for high activity toward the oxygen evolution reaction (OER). Here, we revisited the list of active perovskite oxides constructed based on theoretical oxygen binding energies of reaction intermediates to the catalyst surface. From this list, Ru-based perovskites, i.e. SrRuO3 and LaRuO3, have been predicted as active perovskites to exhibit a particularly high OER activity. We report on the stability of nanoscaled SrRuO3 perovskite prepared by a simple and scalable flame synthesis method. Attempts to obtain LaRuO3 were made; however, its DFT calculated phase diagram suggests that its perovskite phase is not thermodynamically stable, which supports our experimental results such that only a mixture of different La Ru O phases has been obtained. Nanoscaled SrRuO3 is evaluated for its electrochemical activity with a particular emphasis pointed toward stability in both alkaline and acidic media. Through conjoining electrochemical methods, operando X-ray absorption spectroscopy (XAS), and theoretical calculations, we show that SrRuO3 exhibits trivial activity toward OER that decreases promptly. The loss in activity is rationalized through DFT based computations, which corroboratively suggest the poor chemical stability of both selected perovskites. Regardless of the predicted theoretical OER activity, the intrinsic instability strongly suggests that Sr- and La-based ruthenium oxides are not viable catalysts for OER in aqueous media. This further suggests that their activities are independent of their binding energies between intermediates and catalyst surface but rather closely associated with material dissolution. We highlight that understanding the origin of stability under a real operating environment is absolutely essential for the design of a sustainable electrocatalyst with optimal balance between activity and stability.