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Zusammenfassung:
A family of dealloyed metal–oxide hybrid (M1M2@M1Ox) core@shell nanoparticle catalysts is demonstrated to provide substantial advances toward more efficient and less expensive electrolytic water splitting. IrNi@IrOx nanoparticles were synthesized from IrNix precursor alloys through selective surface Ni dealloying and controlled surface oxidation of Ir. Detailed depth-resolved insight into chemical structure, composition, morphology, and oxidation state was obtained using spectroscopic, diffraction, and scanning microscopic techniques (XANES, XRD, STEM-EDX, XPS), which confirmed our structural hypotheses at the outset. A 3-fold catalytic activity enhancement for the electrochemical oxygen evolution reaction (OER) over IrO2 and RuO2 benchmark catalysts was observed for the core-shell catalysts on a noble metal mass basis. Also, the active site-based intrinsic turnover frequency (TOF) was greatly enhanced for the most active IrNi@IrOx catalyst. This study documents the successful use of synthetic dealloying for the preparation of metal-oxide hybrid core-shell catalysts. The concept is quite general, can be applied to other noble metal nanoparticles, and points out a path forward to nanostructured proton-exchange-electrolyzer electrodes with dramatically reduced noble metal content.
