Browsing by Author "Ventosa, Edgar"

Now showing 1 - 4 of 4
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    Evaluation of Perovskites as Electrocatalysts for the Oxygen Evolution Reaction
    (ChemPhysChem, 2014) Rincón, Rosalba A.; Ventosa, Edgar; Masa, Justus; Seisel, Sabine; Kuznetsov, Volodymyr
    The oxygen evolution reaction (OER) is an enabling process for technologies in the area of energy conversion and storage, but its slow kinetics limits its efficiency. We performed an electrochemical evaluation of 14 different perovskites of variable composition and stoichiometry as OER electrocatalysts in alkaline media. We particularly focused on improved methods for a reliable comparison of catalyst activity. From initial electrochemical results we selected the most active samples for further optimization of electrode preparation and testing. An inverted cell configuration facilitated gas bubble detachment and thus minimized blockage of the active surface area. We describe parameters, such as the presence of specific cations, stoichiometry, and conductivity, that are important for obtaining electroactive perovskites for OER. Conductive additives enhanced the current and decreased the apparent overpotential of OER for one of the most active samples (La0.58Sr0.4Fe0.8Co0.2O3).
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    Nanoelectrodes Reveal the Electrochemistry of Single Nickelhydroxide Nanoparticles
    (Chemical Communications, 2016) Clausmeyer, Jan; Masa, Justus; Ventosa, Edgar; Schuhmann, Wolfgang
    Individual Ni(OH)2 nanoparticles deposited on carbon nanoelectrodes are investigated in non-ensemble measurements with respect to their energy storage properties and electrocatalysis for the oxygen evolution reaction (OER). Charging by oxidation of Ni(OH)2 is limited by the diffusion of protons into the particle bulk and the OER activity is independent of the particle size.
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    Powder Catalyst Fixation for Post-Electrolysis Structural Characterization of NiFe Layered Double Hydroxide Based Oxygen Evolution Reaction Electrocatalysts
    (Angewandte Chemie International Edition, 2017) Andronescu, Corina; Barwe, Stefan; Ventosa, Edgar; Masa, Justus; Vasile, Eugeniu; Schuhmann, Wolfgang
    An active and stable OER catalyst was directly fixated on an electrode starting from a NiFe layered double hydroxide (LDH)/polybenzoxazine composite. Owing to its stable immobilization on the electrode, the catalyst can be characterized before and after electrolysis. After electrolysis at 200 mA cm−2 in 5 m KOH for 100 h, previously not reported structural changes were observed for the NiFe LDH.
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    Ultrathin High Surface Area Nickel Boride (NixB) Nanosheets as Highly Efficient Electrocatalyst for Oxygen Evolution
    (Advanced Energy Materials, 2017) Masa, Justus; Sinev, Ilya; Mistry, Hemma; Ventosa, Edgar; Schuhmann, Wolfgang
    The overriding obstacle to mass production of hydrogen from water as the premium fuel for powering our planet is the frustratingly slow kinetics of the oxygen evolution reaction (OER). Additionally, inadequate understanding of the key barriers of the OER is a hindrance to insightful design of advanced OER catalysts. This study presents ultrathin amorphous high-surface area nickel boride (NixB) nanosheets as a low-cost, very efficient and stable catalyst for the OER for electrochemical water splitting. The catalyst affords 10 mA cm−2 at 0.38 V overpotential during OER in 1.0 m KOH, reducing to only 0.28 V at 20 mA cm−2 when supported on nickel foam, which ranks it among the best reported nonprecious catalysts for oxygen evolution. Operando X-ray absorption fine-structure spectroscopy measurements reveal prevalence of NiOOH, as well as Ni-B under OER conditions, owing to a Ni-B core@nickel oxyhydroxide shell (Ni-B@NiOxH) structure, and increase in disorder of the NiOxH layer, thus revealing important insight into the transient states of the catalyst during oxygen evolution.