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Abstract Pseudocapacitors promise to fill the gap between traditional capacitors and batteries by delivering reasonable energy densities and power densities. In this work, pseudocapacitive charge storage properties are demonstrated for two isostructural oxides, Sr₂LaFeMnO₇and Sr₂LaCoMnO₇. These materials comprise spatially separated bilayer stacks of corner sharing BO₆units (B=Fe, Co or Mn). The spaces between stacks accommodate the lanthanum and strontium ions, and the remaining empty spaces are available for oxide ion intercalation, leading to pseudocapacitive charge storage. Iodometric titrations indicate that these materials do not have oxygen‐vacancies. Therefore, the oxide ion intercalation becomes possible due to their structural features and the availability of interstitial sites between the octahedral stacks. Electrochemical studies reveal that both materials show promising energy density and power density values. Further experiments through fabrication of a symmetric two‐electrode cell indicate that these materials retain their pseudocapacitive performance over hundreds of galvanostatic charge‐discharge cycles, with little degradation even after 1000 cycles. 

Abstract Multifunctional materials that are capable of facilitating multiple electrocatalytic processes are highly desirable. This work reports the observation of bifunctional electrocatalytic properties for water‐splitting in layered oxides, featuring 2‐dimensional layers of octahedrally coordinated transition metals separated by alkaline‐earth or rare‐earth metals. Remarkably, these materials are able to catalyze both half‐reactions of water‐splitting,i. e., oxygen‐evolution reaction (OER) and hydrogen‐evolution reaction (HER). Electrical charge‐transport studies of SrLaFe_1‐xCo_xO_4‐δin a wide range of temperatures, 25 to 800 °C, indicate semiconducting behavior for all three compounds, where there is a systematic increase in electrical conductivity as a function of temperature. The end member of the series, SrLaCoO_4‐δ, exhibits the highest electrical charge transport and best electrocatalytic activity toward both OER and HER. This catalyst also features the highest degree of polyhedral distortion as well as the presence of oxygen‐vacancies. In addition, the transition metals in this material have a favorable electronic configuration for enhanced electrocatalytic activity.