Enhanced electrocatalysts fabricated via quenched ultrafast sintering: physicochemical properties and water oxidation applications (original) (raw)
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Synthesis of Sr0.9K0.1FeO3−δ electrocatalysts by mechanical activation
Journal of Solid State Chemistry, 2013
Chemical potential phase stability diagrams were calculated from relevant thermodynamic properties and used to predict the thermodynamic driving force under prospective conditions of room temperature mechanosynthesis. One analysed the dependence of chemical potential diagrams on temperature and partial pressure of evolving gases such as oxygen or carbon dioxide, as expected on using strontium peroxide or strontium carbonate as precursor reactants for the alkali earth component. Thermodynamic calculations were also obtained for changes in titania precursor reactants, including thermodynamic predictions for reactivity of strontium carbonate with amorphous titania. Experimental evidence showed that strontium titanate can be obtained by mechanosynthesis of strontium carbonate þ anatase mixtures, due to previous amorphization under high energy milling. Ability to perform mechanosynthesis with less energetic milling depends on the suitable choice of alternative precursor reactants, which meet the thermodynamic requirements without previous amorphization; this was demonstrated by mechanosynthesis from anatase þstrontium peroxide mixtures.
Frontiers in Energy Research, 2021
Plotting the roadmap of future “renewable energy highway” requires drastic technological advancement of devices like electrolyzers and fuel cells. Technological breakthrough is practically impossible without advanced fundamental understanding of interfacial energy conversion processes, including electrocatalytic water splitting. Particularly challenging is the oxygen evolution reaction which imposes high demands on the long-term activity of electrocatalysts and electrode support materials. To cross the “Rubicon” and in a deterministic manner claim that we developed principles of rational catalyst design, we need first to comprehend the determinants of electrocatalytic activity as well as character of their time evolution. How reliable are reported activity and stability trends, could we interrelate activity and stability, and how meaningful that relation really is are some of the important questions that have to be tackled in building of a more comprehensive view on critically impor...
Catalysts
Perovskites of strontium cobalt oxyhalides having the chemical formulae Sr2CoO4-xHx (H = F, Cl, and Br; x = 0 and 1) were prepared using a solid-phase synthesis approach and comparatively evaluated as electrocatalysts for oxygen evolution in an alkaline solution. The perovskite electrocatalyst crystal phase, surface morphology, and composition were examined by X-ray diffraction, a scanning electron microscope, and energy-dispersive X-ray (EDX) mapping. The electrochemical investigations of the oxyhalides catalysts showed that the doping of F, Cl, or Br into the Sr2CoO4 parent oxide enhances the electrocatalytic activity for the oxygen evolution reaction (OER) with the onset potential as well as the potential required to achieve a current density of 10 mA/cm2 shifting to lower potential values in the order of Sr2CoO4 (1.64, 1.73) > Sr2CoO3Br (1.61, 1.65) > Sr2CoO3Cl (1.53, 1.60) > Sr2CoO3F (1.50, 1.56) V vs. HRE which indicates that Sr2CoO3F is the most active electrode amon...
Chemical synthesis, 2024
Solid oxide cells (SOCs) are regarded as a promising energy technology due to their large current density, diverse range of fuels, and high energy conversion efficiency. The double perovskite Sr 2 FeMoO 6 (SFM) has attracted considerable attention for SOCs due to its tunable structure with superior performance of high conductivity, excellent thermal stability, and remarkable carbon deposition resistance in a reducing atmosphere. However, the electrocatalytic activity of SFM is considerably lower than that of commercial Ni-based SOC electrodes. A timely summary of the synthesis, modulation, and application of SFM perovskites is of great significance for its further development for SOCs. In this review, the methods employed in the preparation of SFM electrocatalysts are introduced first. Then, the advancements in the application of different SFM-based electrocatalysts in the field of SOCs are reviewed, and the research progress in the in-situ exsolution of SFM-based electrocatalysts through ion regulation is assessed. Finally, the future issues associated with SFM-based electrocatalysts are addressed in the realm of electrocatalysis, to advance their application.
Elsevier, 2021
The scarcity and high cost of commercial noble metal-based materials necessitate the need for synthesizing alternative electrocatalysts for oxygen evolution reaction (OER). Many efforts put in place in addressing this problem have resulted in huge successes by employing different routes for synthesizing electrocatalysts, using different families of atoms and compounds. In this regard, this review describes the conceptual study of OER and an overview of electrocatalytic kinetics and theoretical modeling for oxygen evolution reaction. For in-depth understanding, a comprehensive and general overview of the recent developments in the OER electrocatalysts and efficient methods of testing the stabilities of catalysts to obtain reliable results are given. The study also includes some tutorial manuals for describing various parameters needed in electrochemical OER processes. We do hope they will be the useful guiding principles for the newcomers in this field. Interestingly, the emphasis is focused on describing different families of compounds used to synthesize high-performance OER electrocatalysts: which include transition metal compounds, polyoxometalates, carbon nanotubes, single atoms, layered double hydroxide, and non-metal compounds. Conclusively, important future perspectives to foster the advancement of this field are discussed.
Catalysts
A novel processing method that creates and preserves ceramic nanoparticles in solid oxide electrodes during co-sintering at traditional sintering temperatures is introduced. Specifically, carbon templated samarium-doped ceria nanoparticles (nSDC) were successfully integrated with commercial lanthanum strontium cobalt ferrite (LSCF) and commercial SDC powders, producing LSCF-SDC-nSDC cathodes upon processing. The effect of nSDC concentration on cathode electrocatalytic activity was investigated at low operational temperatures, 600 °C–700 °C, with symmetrical cells. Low nSDC loadings, ≤5 wt% nSDC, significantly decreased cell polarization resistance whereas higher loadings increased it. The best electrochemical performance was achieved with 5 wt% nSDC, lowering the polarization resistance by 41% at 600 °C. Fuel cell tests demonstrate that adding 5 wt% nSDC increased the maximum fuel cell power density by 38%. Electrochemical impedance spectra showed substantial improvements in both fu...
Materials Technology for the Energy and Environmental Nexus, Volume 2, 2023
The smooth transition from finite non-renewables to renewable energy conversion technologies will require efficient electrocatalysts which can harness intermittent energies to store in the form of chemical bonds. The oxygen evolution reaction (OER) impedes the widespread usage of water electrolyzers to convert H 2 O into H 2 and persists as a bottleneck, including other energy conversion devices with sluggish four H + /e − kinetics. In this context, designing highly active and stable catalysts capable of driving a lower overpotential in the OER to produce continuous hydrogen (H 2) is a primary demanded. This chapter discussed the mechanism of the OER in conventional adsorbate oxygen and lattice oxygen participation in transition metal oxides (TMOs). Further, the influences of surface engineering, doping, and defects in the TMOs and understanding the electronic structure to screen electrodes towards the structure-activity relationship are highlighted. Specifically, the adsorption strength of O 2p is understood in detail as its binding ability over the surface of TMOs can be correlated directly to the OER activity. The iterative development of TMOs in terms of understanding electronic structural attributes is essential for the commercial deployment of energy conversion technologies. The comprehensive outlook of this chapter investigates thoroughly how TMOs can be used as significant materials for the OER in the near future.
ChemElectroChem, 2019
The activity of electrocatalysts critically depends on the chemical coordination around the active sites. Amorphous materials have short‐range atomic ordering while their crystalline counterparts have both short and long‐range ordering. Traditional synthesis of amorphous materials, involving quenching from high temperatures is unsuitable as it results in less porosity and surface area. In this context, room‐temperature syntheses of high surface area amorphous materials with high activity are desirable. Here, we contrast two electrochemical synthesis procedures for generating high surface area amorphous Co3O4 at room temperature via electrochemical ion intercalation/deintercalation and surface oxidation/reduction cycles and evaluate their performance for electrocatalytic oxygen evolution reaction (OER). In the first approach, Li‐ion is used for the intercalation/deintercalation (Li/D−Li) cycles in Co3O4, which leads to expansion and contraction of structure, inducing amorphization of...
International Journal of Electrochemical Science, 2019
Perovskite-type oxides of La, Sr and Co have been prepared via a sol-gel route using nitrate salt of metals and polyvinylpyrrolidone (PVP40) as precursors. The electrocatalytic properties of the material was investigated by recording cyclic voltammogram (CV) and anodic polarization curve in 1 M KOH at 25 ºC. The experiments have been performed in a three-electrode single compartment glass cell in which the synthesized oxide was taken as anode in the form of film electrode. Auxiliary and reference electrodes were Pt-foil (area ~ 2 cm 2) and Hg/HgO/1M KOH, respectively. The CV recorded in the potential region 0.0-0.7 V, exhibited an anodic (Epa = 495±14 mV) and corresponding cathodic peaks (Epc = 353 ± 38 mV) prior to onset of oxygen evolution reaction (OER). Anodic polarization study indicates that substitution of Sr in the base oxide (LaCoO3) enhanced the electrocatalytic properties of the material. The activity was found to be highest with 0.8 Sr-substitution. At E = 800 mV, it produced current density j = 261.8 mA cm-2 , which is about 65 times higher than the base oxide. Values of Tafel slope and reaction order as given in Table 2, describe that each oxide electrode has different mechanistic path towards OER. Thermodynamic parameters, such as standard entropy of activation (S˚#), standard enthalpy of activation (H˚#) and standard electrochemical energy of activation (Hel˚#) have been estimated for each oxide electrode. Materials have also been analysed for their perovskite phase and morphology by using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques, respectively.