Efficient and sustainable water electrolysis achieved by excess electron reservoir enabling charge replenishment to catalysts.

Suppressing the oxidation of active-Ir(III) in IrOx catalysts is highly desirable to realize an efficient and durable oxygen evolution reaction in water electrolysis. Although charge replenishment from supports can be effective in preventing the oxidation of IrOx catalysts, most supports have inherently limited charge transfer capability. Here, we demonstrate that an excess electron reservoir, which is a charged oxygen species, incorporated in antimony-doped tin oxide supports can effectively control the Ir oxidation states by boosting the charge donations to IrOx catalysts. Both computational and experimental analyses reveal that the promoted charge transfer driven by excess electron reservoir is the key parameter for stabilizing the active-Ir(III) in IrOx catalysts. When used in a polymer electrolyte membrane water electrolyzer, Ir catalyst on excess electron reservoir incorporated support exhibited 75 times higher mass activity than commercial nanoparticle-based catalysts and outstanding long-term stability for 250 h with a marginal degradation under a water-splitting current of 1 A cm-2. Moreover, Ir-specific power (74.8 kW g-1) indicates its remarkable potential for realizing gigawatt-scale H2 production for the first time.

Hierarchically Assembled Cobalt Oxynitride Nanorods and N-Doped Carbon Nanofibers for Efficient Bifunctional Oxygen Electrocatalysis with Exceptional Regenerative Efficiency.

Oxygen-based electrocatalysis is an integral aspect of a clean and sustainable energy conversion/storage system. The development of economic bifunctional electrocatalysts with high activity and durability during reversible reactions remains a great challenge. The tailored porous structure and separately presented active sites for oxygen reduction and oxygen evolution reactions (ORR and OER) without mutual interference are most crucial for achieving desired bifunctional catalysts. Here, we report a hybrid composed of sheath-core cobalt oxynitride (CoOx@CoNy) nanorods grown perpendicularly on N-doped carbon nanofiber (NCNF). The brush-like CoOx@CoNy nanorods, composed of metallic Co4N cores and oxidized surfaces, exhibit excellent OER activity (E = 1.69 V at 10 mA cm-2) in an alkaline medium. Although pristine NCNF or CoOx@CoNy alone had poor catalytic activity in the ORR, the hybrid showed dramatically enhanced ORR performance (E = 0.78 V at -3 mA cm-2). The experimental results coupled with a density functional theory (DFT) simulation confirmed that the broad surface area of the CoOx@CoNy nanorods with an oxidized skin layer boosts the catalytic OER, while the facile adsorption of ORR intermediates and a rapid interfacial charge transfer occur at the interface between the CoOx@CoNy nanorods and the electrically conductive NCNF. Furthermore, it was found that the independent catalytic active sites in the CoOx@CoNy/NCNF catalyst are continuously regenerated and sustained without mutual interference during the round-trip ORR/OER, affording stable operation of Zn-air batteries.

Thiometallate precursors for the synthesis of supported Pt and PtNi nanoparticle electrocatalysts: Size-focusing by S capping.

Herein, we report for the first time the successful preparation of thiometallate-based precursors for use in a bottom-up synthetic process of supported Pt and PtNi nanoparticle catalyst. This precursor enabled the monodisperse synthesis of supported Pt nanoparticles and the in situ formation of S, which were caught directly in a collection system by the nanoparticle synthetic processes consisting of impregnation and thermal processes. S is proven to act as a capping agent in generating highly stable nanoparticles with the size ranging from 2 nm to 3 nm and further favors the formation of monodispersed particles by solid-state digestive ripening. The proposed synthetic methodology can be applied to high-quality PtNi alloy nanoparticle systems. The current route is readily scalable, and multi-gram quantities can be prepared. The prepared carbon-supported Pt and PtNi nanoparticles were characterized as electrocatalysts for the oxygen reduction reaction and exhibited superior performance and durability to commercial Pt/C.