Undercoordinated Two-Dimensional Pt Nanoring Stabilized by a Ring-on-Sheet Nanoheterostructure for Highly Efficient Alkaline Hydrogen Evolution Reaction.

Platinum (Pt) is a state-of-the-art electrocatalyst for green hydrogen production in alkaline electrolytes. The delicate design and fabrication of two-dimensional (2D) Pt nanocatalysts can significantly enhance atomic utilization efficiency, while further improving intrinsic catalytic performance by modulating the density of surface active sites. However, the high surface energy and morphology complexity of 2D nanostructures often result in poor structural stability under the working conditions. Here, we report the synthesis of a 2D ring-on-sheet nanoheterostructure featuring abundant low-coordination Pt sites in which a defect-rich Pt nanoring is stabilized by an ultrathin 2D rhodium (Rh) support. The Rh@Pt nanoring exhibits remarkably enhanced activity and stability in an electrocatalytic hydrogen evolution reaction in alkaline media compared to defect-free Rh@Pt core-shell nanoplates and commercial Pt/C. This work provides new insights for the design and synthesis of 2D nanoheterostructures with abundant surface active sites for efficient and durable electrocatalysis.