remains to be the bottleneck and retards the overall performance. [3] Great efforts have been devoted to exploring robust OER catalysts, [4] and many candidate materials, such as Cu@NiFe LDH, Fe-Co 3 O 4 hierarchical hollow nanoplates, and CoFeZr oxides, generally show remarkable activity and stability under an alkaline environment. However, most of them tend to degrade rapidly under the practical PEM-based OER condition, which is typically a strong acidic media during electrolysis. [5] It is therefore highly desired to develop active and durable catalysts satisfying the harsh acidic OER within the PEM electrolyzer. In general, noble metalbased catalysts hold great potential for electrocatalytic reactions in acid due to their excellent catalytic activity and corrosion resistance. [6] Currently, ruthenium and iridium-based materials are two of the few effective materials for acidic OER. It was generally recognized that Ir-based catalysts exhibit good stability but relatively low activity [7] as well as extremely scarce reserve, [8] while ruthenium shows a very opposite trend. [7] Several experimental strategies, such as alloying, [9] phase/morphology engineering, [10] have proven their effectiveness in improving the intrinsic activity of iridium. Accordingly, core-shell nanostructured Ru@Ir composites were anticipated to hold great potential to improve the catalytic performance, [11] which allows optimizing the surface bonding energy via altering the core-shell electronic interactions and/or the strain effect meanwhile maintaining the good stability of the iridium shell. Moreover, the strain effect enables to continuously modulate the catalytic activity via strengthening or weakening chemisorption bonds by properly regulating the constituents of precursors. [12] Unfortunately, due to the multiple influencing factors and complicated modulation mechanism in material synthesis, competent Ru@Ir catalysts for acidic OER are still very limited in practice.Herein, we successfully synthesized core-shell nanoparticles with Ru core and oxygen incorporated Ir shell (denoted as Ru@Ir-O) that show high OER activity and good stability in acid. Noticeable tensile strain and a certain amount of oxygens were observed in the Ir shell, which also carries more negative charges as compared with pure Ir nanoparticles. These factors cause up-shifted band position and optimized bonding strength of O* and HOO* intermediates on the surface, as evidenced by density functional theory (DFT) calculations. Overall, the Ru@Ir-O catalyst shows a much lower overpotential of 238 mV The design of highly active and durable catalysts for the sluggish anodic oxygen evolution reaction (OER) in acid remains an urgent yet challenging goal in water electrolysis. Herein, a core-shell nanostructured Ru@Ir-O catalyst with tensile strains and incorporated oxygens is introduced in the Ir shell that holds an extremely low OER overpotential of 238 mV at 10 mA cm −2 in acid. The material also shows a remarkable 78-fold higher mass activity than the conventiona...

Yolk–shell structure with magnetic core, interior void and mesoporous polymer/carbon shell demonstrate potential applications in biocatalysis, magnetic biological separation, biomedicine, and magnetic resonance imaging due to their comprehensive benefits of magnetic and mesoporous shells. Herein, yolk–shell structured magnetic mesoporous polydopamine microspheres (Fe3O4@Void@mPDA) and the corresponding derivatives of carbon-based microspheres (Fe3O4@Void@mCN) are successfully fabricated through an interface assembly and selective etching approach. The obtained monodisperse Fe3O4@Void@mPDA microspheres consist of a magnetic core, a mesoporous polydopamine shell, and the large void formed between them, with perpendicular mesopores (5.2 nm), high surface area (303.3 m2g–1), and richness of functional groups. The Fe3O4@Void@mPDA microspheres show a remarkable inhibitory effect on tumor cells. Moreover, the Fe3O4@Void@mCN microspheres can immobilize ultrafine Au nanoparticles for hydrogenation of 4-nitrophenol with superb catalytic activity and excellent magnetic reusability.

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