In hydrogen production, the anodic oxygen evolution reaction (OER) limits the energy conversion efficiency and also impacts stability in proton-exchange membrane water electrolyzers. Widely used Ir-based catalysts suffer from insufficient activity, while more active Ru-based catalysts tend to dissolve under OER conditions. This has been associated with the participation of lattice oxygen (lattice oxygen oxidation mechanism (LOM)), which may lead to the collapse of the crystal structure and accelerate the leaching of active Ru species, leading to low operating stability. Here we develop Sr–Ru–Ir ternary oxide electrocatalysts that achieve high OER activity and stability in acidic electrolyte. The catalysts achieve an overpotential of 190 mV at 10 mA cm–2 and the overpotential remains below 225 mV following 1,500 h of operation. X-ray absorption spectroscopy and 18O isotope-labeled online mass spectroscopy studies reveal that the participation of lattice oxygen during OER was suppressed by interactions in the Ru–O–Ir local structure, offering a picture of how stability was improved. The electronic structure of active Ru sites was modulated by Sr and Ir, optimizing the binding energetics of OER oxo-intermediates.

An electride has been synthesized that is stable to auto-decomposition at room temperature. The key was the theoretically directed synthesis of a per-aza analogue of cryptand[2.2.2] in which each of the linking arms contains a piperazine ring. This complexant was designed to provide strong complexation of Na+ via pre-organization of a "crypt" that contains eight nonreducible tertiary amine nitrogens. The structure and properties indicate that, as with other electrides, the "anions" are electrons trapped in the cavities formed by close-packing of the complexed cations. The isostructural sodide, with Na- anions in the cavities, is also stable at and above room temperature.

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The three-dimensional geometries of cavities and channels in four electrides are determined in detail with the aid of computer graphics methods. Previous theoretical and experimental studies support the view that electrons are trapped in cavities and interact through connecting channels. The magnetic coupling constants and the dimensionalities of the magnetic interactions are consistent in all cases with the cavity and channel structures of electrides. By combining structural information and theory, it may be possible to describe the overall electronic properties of electrides with a model of an electron gas in a complex "plumber's nightmare box" whose geometry is given by the cavity and channel structures.

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