Topotactic Transformations in an Icosahedral Nanocrystal to Form Efficient Water-Splitting Catalysts.

Designing high-performance, precious-metal-based, and economic electrocatalysts remains an important challenge in proton exchange membrane (PEM) electrolyzers. Here, a highly active and durable bifunctional electrocatalyst for PEM electrolyzers based on a rattle-like catalyst comprising a Ni/Ru-doped Pt core and a Pt/Ni-doped RuO2 frame shell, which is topotactically transformed from an icosahedral Pt/Ni/Ru nanocrystal, is reported. The RuO2 -based frame shell with its highly reactive surfaces leads to a very high activity for the oxygen evolution reaction (OER) in acidic media, reaching a current density of 10 mA cm-2 at an overpotential of 239 mV, which surpasses those of previously reported catalysts. The Pt dopant in the RuO2 shell enables a sustained OER activity even after a 2000 cycles of an accelerated durability test. The Pt-based core catalyzes the hydrogen evolution reaction with an excellent mass activity. A two-electrode cell employing Pt/RuO2 as the electrode catalyst demonstrates very high activity and durability, outperforming the previously reported cell performances.