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Results for “perovskite-oxide”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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DOE OSTI2021

Sustainable Oxide Electrocatalyst for Hydrogen- and Oxygen-Evolution Reactions

In this work, an electrocatalyst for water splitting based on earth-abundant metals is reported. This perovskite-oxide catalyst, CaSrFe 0.75 Co 0.75 Mn 0.5 O 6-δ (CSFCM), is examined using both experimental and computational methods. It demonstrates a combination of properties, which include (a) very high activity for the oxygen-evolution reaction with an overpotential of eta = 0.19 V at 10 mA/cm 2 , (b) high stability over 1000 cycles of catalysis, (c) the ability to catalyze the hydrogen-evolution reaction effectively in both acidic and basic conditions, and (d) catalytic activity as a single-phase bulk material without the need for any additional processing, multicomponent composite preparation, or nanofabrication. Therefore, the catalytic activity of CSFCM is intrinsic, making it a good benchmark compound for future studies of electrocatalytic parameters. This work also highlights the impact of systematic structural design on electrocatalytic activity. Results from density functional theory calculations indicate that in addition to an optimal e g occupancy of similar to 1, an additional descriptor, i.e., maximizing the number of free e g carriers, correlates with the electrocatalytic activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Trace Fe activates perovskite nickelate OER catalysts in alkaline media via redox-active surface Ni species formed during electrocatalysis

The accurate description of activity trends among perovskite-oxide oxygen-evolution-reaction (OER) catalysts using electronic-structure descriptors requires that the bulk structure of the catalyst is comparable to that of the surface. Few studies have addressed the dynamic nature of the catalyst's structure during the OER and the consequential implications for understanding activity. Here, we use a combination of electrochemical and materials-characterization techniques to study the surface reconstruction and the associated formation of a new redox-active phase on LaNiO 3 particles, LaNiO 3 epitaxial films, and an analogous Ruddlesden-Popper phase, La 2 NiO 4 . Small, but characteristic, redox features corresponding to Ni redox in nominally amorphous NiO x H y are observed during cyclic voltammetry of these initially fully crystalline materials. The size of these redox features grows with prolonged cycling and contributes to an increased surface area as determined from electrochemical impedance spectroscopy (EIS). Here we find the OER activity is strongly dependent on soluble Fe species in the electrolyte, common impurities in alkaline media. These observations are consistent with the reconstruction of the crystalline surface to form NiO x H y species and subsequent activation by adsorption of Fe forming the well-known and extremely active NiFeO x H y OER catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗